40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2012 CFR

2012-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2011 CFR

2011-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2013 CFR

2013-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2014 CFR

2014-07-01

... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such... injection until all required corrective action has been taken. (3) Injection pressure limitation. The...

Triggering active galactic nuclei in galaxy clusters

NASA Astrophysics Data System (ADS)

Marshall, Madeline A.; Shabala, Stanislav S.; Krause, Martin G. H.; Pimbblet, Kevin A.; Croton, Darren J.; Owers, Matt S.

2018-03-01

We model the triggering of active galactic nuclei (AGN) in galaxy clusters using the semi-analytic galaxy formation model SAGE. We prescribe triggering methods based on the ram pressure galaxies experience as they move throughout the intracluster medium, which is hypothesized to trigger star formation and AGN activity. The clustercentric radius and velocity distribution of the simulated active galaxies produced by these models are compared with those of AGN and galaxies with intense star formation from a sample of low-redshift relaxed clusters from the Sloan Digital Sky Survey. The ram pressure triggering model that best explains the clustercentric radius and velocity distribution of these observed galaxies has AGN and star formation triggered if 2.5 × 10-14 Pa < Pram < 2.5 × 10-13 Pa and Pram > 2Pinternal; this is consistent with expectations from hydrodynamical simulations of ram-pressure-induced star formation. Our results show that ram pressure is likely to be an important mechanism for triggering star formation and AGN activity in clusters.

Ozone formation in pulsed SDBD in a wide pressure range

NASA Astrophysics Data System (ADS)

Starikovskiy, Andrey; Nudnova, Maryia; mipt Team

2011-10-01

Ozone concentration in surface anode-directed DBD for wide pressure range (150 - 1300 torr) was experimentally measured. Voltage and pressure effect were investigated. Reduced electric field was measured for anode-directed and cathode-directed SDBD. E/n values in cathode-directed SDBD is higher than in cathode-directed on 50 percent at atmospheric pressure. E/n value increase leads to decrease the rate of oxygen dissociation and Ozone formation at lower pressures. Radiating region thickness of sliding discharge was measured. Typical thickness of radiating zone is 0.4-1.0 mm within pressure range 220-740 torr. It was shown that high-voltage pulsed nanosecond discharge due to high E/n value produces less Ozone with compare to other discharges. Kinetic model was proposed to describe Ozone formation in the pulsed nanosecond SDBD.

40 CFR 144.55 - Corrective action.

Code of Federal Regulations, 2010 CFR

2010-07-01

... injection zone does not exceed hydrostatic pressure at the site of any improperly completed or abandoned... the case of Class II wells operating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. For such...

Bromate formation from the oxidation of bromide in the UV/chlorine process with low pressure and medium pressure UV lamps.

PubMed

Fang, Jingyun; Zhao, Quan; Fan, Chihhao; Shang, Chii; Fu, Yun; Zhang, Xiangru

2017-09-01

When a bromide-containing water is treated by the ultraviolet (UV)/chlorine process, hydroxyl radicals (HO) and halogen radicals such as Cl or Br are formed due to the UV photolysis of free halogens. These reactive species may induce the formation of bromate, which is a probable human carcinogen. Bromate formation in the UV/chlorine process using low pressure (LP) and medium pressure (MP) lamps in the presence of bromide was investigated in the present study. The UV/chlorine process significantly enhanced bromate formation as compared to dark chlorination. The bromate formation was elevated with increasing UV fluence, bromide concentration, and pH values under both LP and MP UV irradiations. It was significantly enhanced at pH 9 compared to those at pH 6 and 7 with MP UV irradiation, while it was slightly enhanced at pH 9 with LP UV. The formation by UV/chlorine process started with the formation of free bromine (HOBr/OBr - ) through the reaction of chlorine and bromide, followed by a subsequent oxidation of free bromine and formation of BrO and bromate by reacting with radicals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Recent experimental data may point to a greater role for osmotic pressures in the subsurface

USGS Publications Warehouse

Neuzil, C.E.; Provost, A.M.

2009-01-01

Uncertainty about the origin of anomalous fluid pressures in certain geologic settings has caused researchers to take a second look at osmosis, or flow driven by chemical potential differences, as a pressure‐generating process in the subsurface. Interest in geological osmosis has also increased because of an in situ experiment by Neuzil (2000) suggesting that Pierre Shale could generate large osmotic pressures when highly compacted. In the last few years, additional laboratory and in situ experiments have greatly increased the number of data on osmotic properties of argillaceous formations, but they have not been systematically examined. In this paper we compile these data and explore their implications for osmotic pressure generation in subsurface systems. Rather than base our analysis on osmotic efficiencies, which depend strongly on concentration, we calculated values of a quantity we term osmotic specific surface area (Aso) that, in principle, is a property of the porous medium only. The Aso values are consistent with a surprisingly broad spectrum of osmotic behavior in argillaceous formations, and all the formations tested exhibited at least a modest ability to generate osmotic pressure. It appears possible that under appropriate conditions some formations can be highly effective osmotic membranes able to generate osmotic pressures exceeding 30 MPa (3 km of head) at porosities as high as ∼0.1 and pressures exceeding 10 MPa at porosities as high as ∼0.2. These findings are difficult to reconcile with the lack of compelling field evidence for osmotic pressures, and we propose three explanations for the disparity: (1) Our analysis is flawed and argillaceous formations are less effective osmotic membranes than it suggests; (2) the necessary subsurface conditions, significant salinity differences within intact argillaceous formations, are rare; or (3) osmotic pressures are unlikely to be detected and are not recognized when encountered. The last possibility, that osmotic pressures routinely escape detection or are attributed to other mechanisms, has important implications for understanding subsurface flow regimes.

A Pressure-Based Analysis of Vortex Ring Pinch-Off

NASA Astrophysics Data System (ADS)

Schlueter, Kristy; Braun, Noah; Dabiri, John

2014-11-01

This study investigated the development of vortex rings over a range of maximum stroke ratios, and analyzed vorticity and pressure data for clues to the physical mechanisms underlying vortex pinch-off. An impulsive piston velocity profile and Reynolds number of 3000 were used for all cases. The formation number was consistently found to be 3.6 +/-0.3. A recently developed algorithm was used to generate pressure fields by integrating the pressure gradient along several paths through the velocity field and taking the median to get explicit values for pressure. The formation time at the occurrence of a local maximum in the pressure between the vortex ring and the lip of the nozzle, known as the trailing pressure maximum, was found to occur concurrently with the formation number for each case, within the error associated with the temporal resolution of the data. This suggests that the trailing pressure maximum is an indicator of vortex ring pinch-off. This is consistent with the results of Lawson and Dawson (2014), who found that the appearance of the trailing pressure maximum was coincident with the formation number. This pressure based approach to determining vortex ring pinch-off will be applied to a biological flow to examine the efficiency of such a flow. This research was partially supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

Variations of permeability and pore size distribution of porous media with pressure.

PubMed

Chen, Quan; Kinzelbach, Wolfgang; Ye, Chaohui; Yue, Yong

2002-01-01

Porosity and permeability of porous and fractured geological media decrease with the exploitation of formation fluids such as petroleum, natural gas, or ground water. This may result in ground subsidence and a decrease of recovery of petroleum, natural gas, or ground water. Therefore, an evaluation of the behavior of permeability and porosity under formation fluid pressure changes is important to petroleum and ground water industries. This study for the first time establishes a method, which allows for the measurement of permeability, porosity, and pore size distribution of cores simultaneously. From the observation of the pore size distribution by low-field nuclear magnetic resonance (NMR) relaxation time spectrometry the mechanisms of pressure-dependent porosity and permeability change can be derived. This information cannot be obtained by traditional methods. As the large-size pores or fractures contribute significantly to the permeability, their change consequently leads to a large permeability change. The contribution of fractures to permeability is even larger than that of pores. Thus, the permeability of the cores with fractures decreased more than that of cores without fractures during formation pressure decrease. Furthermore, it did not recover during formation pressure increase. It can be concluded that in fractures, mainly plastic deformation takes place, while matrix pores mainly show elastic deformation. Therefore, it is very important to keep an appropriate formation fluid pressure during the exploitation of ground water and petroleum in a fractured formation.

Radiation pressure in super star cluster formation

NASA Astrophysics Data System (ADS)

Tsang, Benny T.-H.; Milosavljević, Miloš

2018-05-01

The physics of star formation at its extreme, in the nuclei of the densest and the most massive star clusters in the universe—potential massive black hole nurseries—has for decades eluded scrutiny. Spectroscopy of these systems has been scarce, whereas theoretical arguments suggest that radiation pressure on dust grains somehow inhibits star formation. Here, we harness an accelerated Monte Carlo radiation transport scheme to report a radiation hydrodynamical simulation of super star cluster formation in turbulent clouds. We find that radiation pressure reduces the global star formation efficiency by 30-35%, and the star formation rate by 15-50%, both relative to a radiation-free control run. Overall, radiation pressure does not terminate the gas supply for star formation and the final stellar mass of the most massive cluster is ˜1.3 × 106 M⊙. The limited impact as compared to in idealized theoretical models is attributed to a radiation-matter anti-correlation in the supersonically turbulent, gravitationally collapsing medium. In isolated regions outside massive clusters, where the gas distribution is less disturbed, radiation pressure is more effective in limiting star formation. The resulting stellar density at the cluster core is ≥108 M⊙ pc-3, with stellar velocity dispersion ≳ 70 km s-1. We conclude that the super star cluster nucleus is propitious to the formation of very massive stars via dynamical core collapse and stellar merging. We speculate that the very massive star may avoid the claimed catastrophic mass loss by continuing to accrete dense gas condensing from a gravitationally-confined ionized phase.

The effect of nozzle diameter, injection pressure and ambient temperature on spray characteristics in diesel engine

NASA Astrophysics Data System (ADS)

Rhaodah Andsaler, Adiba; Khalid, Amir; Sharifhatul Adila Abdullah, Nor; Sapit, Azwan; Jaat, Norrizam

2017-04-01

Mixture formation of the ignition process is a key element in the diesel combustion as it influences the combustion process and exhaust emission. Aim of this study is to elucidate the effects of nozzle diameter, injection pressure and ambient temperature to the formation of spray. This study investigated diesel formation spray using Computational Fluid Dynamics. Multiphase volume of fluid (VOF) behaviour in the chamber are determined by means of transient simulation, Eulerian of two phases is used for implementation of mixing fuel and air. The detail behaviour of spray droplet diameter, spray penetration and spray breakup length was visualised using the ANSYS 16.1. This simulation was done in different nozzle diameter 0.12 mm and 0.2 mm performed at the ambient temperature 500 K and 700 K with different injection pressure 40 MPa, 70 MPa and 140 MPa. Results show that high pressure influence droplet diameter become smaller and the penetration length longer with the high injection pressure apply. Smaller nozzle diameter gives a shorter length of the breakup. It is necessary for nozzle diameter and ambient temperature condition to improve the formation of spray. High injection pressure is most effective in improvement of formation spray under higher ambient temperature and smaller nozzle diameter.

Wellbore pressure transducer

DOEpatents

Shuck, Lowell Z.

1979-01-01

Subterranean earth formations containing energy values are subjected to hydraulic fracturing procedures to enhance the recovery of the energy values. These fractures are induced in the earth formation by pumping liquid into the wellbore penetrating the earth formation until the pressure of the liquid is sufficient to fracture the earth formation adjacent to the wellbore. The present invention is directed to a transducer which is positionable within the wellbore to generate a signal indicative of the fracture initiation useful for providing a timing signal to equipment for seismic mapping of the fracture as it occurs and for providing a measurement of the pressure at which the fracture is initiated.

Role of Salt, Pressure, and Water Activity on Homogeneous Ice Nucleation.

PubMed

Espinosa, Jorge R; Soria, Guiomar D; Ramirez, Jorge; Valeriani, Chantal; Vega, Carlos; Sanz, Eduardo

2017-09-21

Pure water can be substantially supercooled below the melting temperature without transforming into ice. The achievable supercooling can be enhanced by adding solutes or by applying hydrostatic pressure. Avoiding ice formation is of great importance in the cryopreservation of food or biological samples. In this Letter, we investigate the similarity between the effects of pressure and salt on ice formation using a combination of state-of-the-art simulation techniques. We find that both hinder ice formation by increasing the energetic cost of creating the ice-fluid interface. Moreover, we examine the widely accepted proposal that the ice nucleation rate for different pressures and solute concentrations can be mapped through the activity of water [ Koop , L. ; Tsias , P. Nature , 2000 , 406 , 611 ]. We show that such a proposal is not consistent with the nucleation rates predicted in our simulations because it does not include all parameters affecting ice nucleation. Therefore, even though salt and pressure have a qualitatively similar effect on ice formation, they cannot be quantitatively mapped onto one another.

Effect of pulse pressure on borehole stability during shear swirling flow vibration cementing.

PubMed

Cui, Zhihua; Ai, Chi; Lv, Lei; Yin, Fangxian

2017-01-01

The shear swirling flow vibration cementing (SSFVC) technique rotates the downhole eccentric cascade by circulating cementing fluid. It makes the casing eccentrically revolve at high speed around the borehole axis. It produces strong agitation action to the annulus fluid, makes it in the state of shear turbulent flow, and results in the formation of pulse pressure which affects the surrounding rock stress. This study was focused on 1) the calculation of the pulse pressure in an annular turbulent flow field based on the finite volume method, and 2) the analysis of the effect of pulse pressure on borehole stability. On the upside, the pulse pressure is conducive to enhancing the liquidity of the annulus fluid, reducing the fluid gel strength, and preventing the formation of fluid from channeling. But greater pulse pressure may cause lost circulation and even formation fracturing. Therefore, in order to ensure smooth cementing during SSFVC, the effect of pulse pressure should be considered when cementing design.

HOW GALACTIC ENVIRONMENT REGULATES STAR FORMATION

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

Meidt, Sharon E.

2016-02-10

In a new simple model I reconcile two contradictory views on the factors that determine the rate at which molecular clouds form stars—internal structure versus external, environmental influences—providing a unified picture for the regulation of star formation in galaxies. In the presence of external pressure, the pressure gradient set up within a self-gravitating turbulent (isothermal) cloud leads to a non-uniform density distribution. Thus the local environment of a cloud influences its internal structure. In the simple equilibrium model, the fraction of gas at high density in the cloud interior is determined simply by the cloud surface density, which is itselfmore » inherited from the pressure in the immediate surroundings. This idea is tested using measurements of the properties of local clouds, which are found to show remarkable agreement with the simple equilibrium model. The model also naturally predicts the star formation relation observed on cloud scales and at the same time provides a mapping between this relation and the closer-to-linear molecular star formation relation measured on larger scales in galaxies. The key is that pressure regulates not only the molecular content of the ISM but also the cloud surface density. I provide a straightforward prescription for the pressure regulation of star formation that can be directly implemented in numerical models. Predictions for the dense gas fraction and star formation efficiency measured on large-scales within galaxies are also presented, establishing the basis for a new picture of star formation regulated by galactic environment.« less

Sour gas injection for use with in situ heat treatment

DOEpatents

Fowler, Thomas David [Houston, TX

2009-11-03

Systems, methods, and heaters for treating a subsurface formation are described herein. At least one method for providing acidic gas to a subsurface formation is described herein. The method may include providing heat from one or more heaters to a portion of a subsurface formation; producing fluids that include one or more acidic gases from the formation using a heat treatment process. At least a portion of one of the acidic gases may be introduced into the formation, or into another formation, through one or more wellbores at a pressure below a lithostatic pressure of the formation in which the acidic gas is introduced.

Early episodes of high-pressure core formation preserved in plume mantle

NASA Astrophysics Data System (ADS)

Jackson, Colin R. M.; Bennett, Neil R.; Du, Zhixue; Cottrell, Elizabeth; Fei, Yingwei

2018-01-01

The decay of short-lived iodine (I) and plutonium (Pu) results in xenon (Xe) isotopic anomalies in the mantle that record Earth’s earliest stages of formation. Xe isotopic anomalies have been linked to degassing during accretion, but degassing alone cannot account for the co-occurrence of Xe and tungsten (W) isotopic heterogeneity in plume-derived basalts and their long-term preservation in the mantle. Here we describe measurements of I partitioning between liquid Fe alloys and liquid silicates at high pressure and temperature and propose that Xe isotopic anomalies found in modern plume rocks (that is, rocks with elevated 3He/4He ratios) result from I/Pu fractionations during early, high-pressure episodes of core formation. Our measurements demonstrate that I becomes progressively more siderophile as pressure increases, so that portions of mantle that experienced high-pressure core formation will have large I/Pu depletions not related to volatility. These portions of mantle could be the source of Xe and W anomalies observed in modern plume-derived basalts. Portions of mantle involved in early high-pressure core formation would also be rich in FeO, and hence denser than ambient mantle. This would aid the long-term preservation of these mantle portions, and potentially points to their modern manifestation within seismically slow, deep mantle reservoirs with high 3He/4He ratios.

Surface morphologies and oddities for ices under temperature and pressure conditions extending from Earth to ocean worlds of the outer solar system: Do penitentes and suncups form on Europa and Enceladus?

NASA Astrophysics Data System (ADS)

Hand, K. P.; Berisford, D. F.; Foster, J.; Furst, B.; Poston, M.; Kosberg, J.; Hofmann, A.; Lang, M.

2017-12-01

In cold, low-pressure, high-irradiance environments on Earth extraordinary formations of penitentes and suncups are observed. These morphologies emerge, in part, as a result of radiative feedback in ice and snow at temperatures and pressures near the vapor pressure sublimation curve of water. For ice covered ocean worlds of the outer solar system, such as Europa and Enceladus, the 100 K surfaces lack atmospheres (<1e-8 torr) and thus exist in a physical regime for water where the physics of penitente formation, as known from Earth, may not apply. Thus, we predict that those surfaces are unlikely to evolve to penitente and suncup morphologies, at least as they are known and formed on Earth. To investigate the range of possible morphologies and formation mechanisms under Earth and extraterrestrial conditions our team has constructed several temperature-, pressure-, and irradiance-controlled chambers. Results to date indicate that with even modest reduction in temperature and pressure toward Europa or Enceladus conditions leads to inhibition of penitente formation. Furthermore, addition of salts, as would be expected in ocean-derived waters of Europa and Enceladus, also inhibits penitente and suncup formation. During this talk we will present results from these experiments and discuss application of these results to the future exploration of ocean worlds.

Pressure effect on dissimilatory sulfate reduction

NASA Astrophysics Data System (ADS)

Williamson, A. J.; Carlson, H. K.; Coates, J. D.

2015-12-01

Biosouring is the production of H2S by sulfate reducing microorganisms (SRM) in-situ or in the produced fluids of oil reservoirs. Sulfide is explosive, toxic and corrosive which can trigger equipment and transportation failure, leading to environmental catastrophe. As oil exploration and reservoir development continue, subsequent enhanced recovery is occurring in progressively deeper formations and typical oil reservoir pressures range from 10-50 MPa. Therefore, an understanding of souring control effects will require an accurate understanding of the influence of pressure on SRM metabolism and the efficacy of souring control treatments at high pressure. Considerable work to date has focussed on souring control at ambient pressure; however, the influence of pressure on biogeochemical processes and souring treatments in oil reservoirs is poorly understood. To explore the impact of pressure on SRM, wild type Desulfovibrio alaskensis G20 (isolated from a producing oil well in Ventura County, California) was grown under a range of pressures (0.1-14 MPa) at 30 °C. Complete sulfate reduction occurred in all pressures tested within 3 days, but microbial growth was inhibited with increasing pressure. Bar-seq identified several genes associated with flagella biosynthesis (including FlhB) and assembly as important for survival at elevated pressure and fitness was confirmed using individual transposon mutants. Flagellar genes have previously been implicated with biofilm formation and confocal microscopy on glass slides incubated with wild type D. alaskensis G20 showed more biomass associated with surfaces under pressure, highlighting the link between pressure, flagellar and biofilm formation. To determine the effect of pressure on the efficacy of SRM inhibitors, IC50 experiments were conducted and D. alaskensis G20 showed a greater resistance to nitrate and the antibiotic chloramphenicol, but a lower resistance to perchlorate. These results will be discussed in the context of deep subsurface microbiology and oil reservoir biosouring. Overall, this work furthers our understanding of oil reservoir biogeochemistry and highlights the impact of pressure on biofilm formation and biosouring strategies.

Semipermeability Evolution of Wakkanai Mudstones During Isotropic Compression

NASA Astrophysics Data System (ADS)

Takeda, M.; Manaka, M.

2015-12-01

Precise identification of major processes that influence groundwater flow system is of fundamental importance for the performance assessment of waste disposal in subsurface. In the characterization of groundwater flow system, gravity- and pressure-driven flows have been conventionally assumed as dominant processes. However, recent studies have suggested that argillites can act as semipermeable membranes and they can cause chemically driven flow, i.e., chemical osmosis, under salinity gradients, which may generate erratic pore pressures in argillaceous formations. In order to identify the possibility that chemical osmosis is involved in erratic pore pressure generations in argillaceous formations, it is essential to measure the semipermeability of formation media; however, in the measurements of semipermeability, little consideration has been given to the stresses that the formation media would have experienced in past geologic processes. This study investigates the influence of stress history on the semipermeability of an argillite by an experimental approach. A series of chemical osmosis experiments were performed on Wakkanai mudstones to measure the evolution of semipermeability during loading and unloading confining pressure cycles. The osmotic efficiency, which represents the semipermeability, was estimated at each confining pressure. The results show that the osmotic efficiency increases almost linearly with increasing confining pressure; however, the increased osmotic efficiency does not recover during unloading unless the confining pressure is almost relieved. The observed unrecoverable change in osmotic efficiency may have an important implication on the evaluation of chemical osmosis in argillaceous formations that have been exposed to large stresses in past geologic processes. If the osmotic efficiency increased by the past stress can remain unchanged to date, the osmotic efficiency should be measured at the past highest stress rather than the current in-situ stress. Otherwise, the effect of chemical osmosis on the pore pressure generation would be underestimated.

Subsurface fluid pressures from drill-stem tests, Uinta Basin, Utah

USGS Publications Warehouse

Nelson, P.H.

2002-01-01

High fluid pressures are known to be associated with oil and gas fields in the Uinta Basin, Utah. Shut-in pressure measurements from drill-stem tests show how pressure varies with depth and by area within the basin. The data base used in this report incorporates over 2,000 pressure measurements from drill-stem tests in wells completed prior to 1985. However, the number of useful pressure measurements is considerably less, because many drill-stem tests fail to stabilize at the actual formation pressure if the permeability is low. By extracting the maximum pressure measurements recorded in a collection of wells within an area, the trend of formation pressure within that area can be approximated. Areal compilations of pressures from drill-stem tests show that overpressured rock formations occur throughout much of the northern and eastern areas of the Uinta Basin. In particular, significant overpressuring (0.5 < pressure gradient < 0.8 psi/ft) is found throughout much of the Altamont-Bluebell field at depths ranging from 10,000 to 13,000 ft, equivalent to 5,000 to 8,000 ft below sea level. Limited data indicate that the pressure gradient declines at depths greater than 13,000 ft. An underpressured zone appears to exist in the Altamont-Bluebell field at depths shallower than 5,000 ft. Throughout the eastern Uinta Basin, moderately overpressured zones (0.46 < pressure gradient < 0.5 psi/ft) are common, with local evidence of significantly overpressured zones, but pressure gradients greater than 0.6 psi/ft are rare.

Determination of the heat of hydride formation/decomposition by high-pressure differential scanning calorimetry (HP-DSC).

PubMed

Rongeat, Carine; Llamas-Jansa, Isabel; Doppiu, Stefania; Deledda, Stefano; Borgschulte, Andreas; Schultz, Ludwig; Gutfleisch, Oliver

2007-11-22

Among the thermodynamic properties of novel materials for solid-state hydrogen storage, the heat of formation/decomposition of hydrides is the most important parameter to evaluate the stability of the compound and its temperature and pressure of operation. In this work, the desorption and absorption behaviors of three different classes of hydrides are investigated under different hydrogen pressures using high-pressure differential scanning calorimetry (HP-DSC). The HP-DSC technique is used to estimate the equilibrium pressures as a function of temperature, from which the heat of formation is derived. The relevance of this procedure is demonstrated for (i) magnesium-based compounds (Ni-doped MgH2), (ii) Mg-Co-based ternary hydrides (Mg-CoHx) and (iii) Alanate complex hydrides (Ti-doped NaAlH4). From these results, it can be concluded that HP-DSC is a powerful tool to obtain a good approximation of the thermodynamic properties of hydride compounds by a simple and fast study of desorption and absorption properties under different pressures.

Effect of confining pressure on diffusion coefficients in clay-rich, low-permeability sedimentary rocks.

PubMed

Xiang, Y; Al, T; Mazurek, M

2016-12-01

The effect of confining pressure (CP) on the diffusion of tritiated-water (HTO) and iodide (I - ) tracers through Ordovician rocks from the Michigan Basin, southwestern Ontario, Canada, and Opalinus Clay from Schlattingen, Switzerland was investigated in laboratory experiments. Four samples representing different formations and lithologies in the Michigan Basin were studied: Queenston Formation shale, Georgian Bay Formation shale, Cobourg Formation limestone and Cobourg Formation argillaceous limestone. Estimated in situ vertical stresses at the depths from which the samples were retrieved range from 12.0 to 17.4MPa (Michigan Basin) and from 21 to 23MPa (Opalinus Clay). Effective diffusion coefficients (D e ) were determined in through-diffusion experiments. With HTO tracer, applying CP resulted in decreases in D e of 12.5% for the Queenston Formation shale (CP max =12MPa), 30% for the Georgian Bay Formation shale (15MPa), 34% for the Cobourg Formation limestone (17.4MPa), 31% for the Cobourg Formation argillaceous limestone (17.4MPa) and 43-46% for the Opalinus Clay (15MPa). Decreases in D e were larger for the I - tracer: 13.8% for the Queenston shale, 42% for the Georgian Bay shale, 50% for the Cobourg Formation limestone, 55% for the Cobourg Formation argillaceous limestone and 63-68% for the Opalinus Clay. The tracer-specific nature of the response is attributed to an increasing influence of anion exclusion as the pore size decreases at higher CP. Results from the shales (including Opalinus Clay) indicate that the pressure effect on D e can be represented by a linear relationship between D e and ln(CP), which provides valuable predictive capability. The nonlinearity results in a relatively small change in D e at high CP, suggesting that it is not necessary to apply the exact in situ pressure conditions in order to obtain a good estimate of the in situ diffusion coefficient. Most importantly, the CP effect on shale is reversible (±12%) suggesting that, for argillaceous rocks, it is possible to obtain D e values that are representative of the in-situ condition by conducting measurements on re-pressurized samples that were obtained with standard drilling practices. This may not be the case for brittle rock samples as the results from limestone suggest that irreversible damage occurred during the pressure cycling. Copyright © 2016 Elsevier B.V. All rights reserved.

Changes in Physical Properties of the Nankai Trough Megasplay Fault Induced by Earthquakes, Detected by Continuous Pressure Monitoring

NASA Astrophysics Data System (ADS)

Kinoshita, C.; Saffer, D.; Kopf, A.; Roesner, A.; Wallace, L. M.; Araki, E.; Kimura, T.; Machida, Y.; Kobayashi, R.; Davis, E.; Toczko, S.; Carr, S.

2018-02-01

One primary objective of Integrated Ocean Drilling Program Expedition 365, conducted as part of the Nankai Trough Seismogenic Zone Experiment, was to recover a temporary observatory emplaced to monitor formation pore fluid pressure and temperature within a splay fault in the Nankai subduction zone offshore SW Honshu, Japan. Here we use a 5.3 year time series of formation pore fluid pressure, and in particular the response to ocean tidal loading, to evaluate changes in pore pressure and formation and fluid elastic properties induced by earthquakes. Our analysis reveals 31 earthquake-induced perturbations. These are dominantly characterized by small transient increases in pressure (28 events) and decreases in ocean tidal loading efficiency (14 events) that reflect changes to formation or fluid compressibility. The observed perturbations follow a magnitude-distance threshold similar to that reported for earthquake-driven hydrological effects in other settings. To explore the mechanisms that cause these changes, we evaluate the expected static and dynamic strains from each earthquake. The expected static strains are too small to explain the observed pressure changes. In contrast, estimated dynamic strains correlate with the magnitude of changes in both pressure and loading efficiency. We propose potential mechanism for the changes and subsequent recovery, which is exsolution of dissolved gas in interstitial fluids in response to shaking.

Interpreting fluid pressure anomalies in shallow intraplate argillaceous formations

USGS Publications Warehouse

Neuzil, Christopher E.

2015-01-01

Investigations have revealed several instances of apparently isolated highs or lows in pore fluid potential in shallow (< ~ 1 km depth) argillaceous formations in intraplate settings. Formations with the pressure anomalies are distinguished by (1) smaller ratios of hydraulic conductivity to formation thickness and (2) smaller hydraulic (or pressure) diffusivities than those without anomalies. This is consistent with transient Darcian flow caused by strain at rates of ~ 10−17 to 10-16 s-1, by significant perturbing events in the past 104 to 106 annum or by some combination of the two. Plausible causes include erosional downwasting, tectonic strain, and glaciation. In this conceptualization the anomalies provide constraints on formation-scale flow properties, flow history, and local geological forcing in the last 106 annum and in particular indicate zones of low permeability (10−19–10−22 m2) that could be useful for isolation of nuclear waste.

Formation of ball streamers at a subnanosecond breakdown of gases at a high pressure in a nonuniform electric field

NASA Astrophysics Data System (ADS)

Beloplotov, D. V.; Tarasenko, V. F.; Sorokin, D. A.; Lomaev, M. I.

2017-11-01

The formation of a diffuse discharge plasma at a subnanosecond breakdown of a "cone-plane" gap filled with air, nitrogen, methane, hydrogen, argon, neon, and helium at various pressures has been studied. Nanosecond negative and positive voltage pulses have been applied to the conical electrode. The experimental data on the dynamics of plasma glow at the stage of formation and propagation of a streamer have been obtained with intensified charge-coupled device and streak cameras. It has been found that the formation of ball streamers is observed in all gases and at both polarities. A supershort avalanche electron beam has been detected behind the flat foil electrode in a wide range of pressures in the case of a negatively charged conical electrode. A mechanism of the formation of streamers at breakdown of various gases at high overvoltages has been discussed.

Increased likelihood of induced seismicity in highly overpressured shale formations

NASA Astrophysics Data System (ADS)

Eaton, David W.; Schultz, Ryan

2018-05-01

Fluid-injection processes such as disposal of saltwater or hydraulic fracturing can induce earthquakes by increasing pore pressure and/or shear stress on faults. Natural processes, including transformation of organic material (kerogen) into hydrocarbon and cracking to produce gas, can similarly cause fluid overpressure. Here we document two examples from the Western Canada Sedimentary Basin where earthquakes induced by hydraulic fracturing are strongly clustered within areas characterized by pore-pressure gradient in excess of 15 kPa/m. Despite extensive hydraulic-fracturing activity associated with resource development, induced earthquakes are virtually absent in the Montney and Duvernay Formations elsewhere. Statistical analysis suggests a negligible probability that this spatial correlation developed by chance. This implies that, in addition to known factors such as anthropogenic pore-pressure increase and proximity to critically stressed faults, high in-situ overpressure of shale formations may also represent a controlling factor for inducing earthquakes by hydraulic fracturing. On a geological timescale, natural pore-pressure generation may lead to fault-slip episodes that regulate magnitude of formation-overpressure.

Quantitative Analysis of Major Phytochemicals in Orthodox tea (Camellia sinensis), Oxidized under Compressed Air Environment.

PubMed

Panda, Brajesh Kumar; Datta, Ashis Kumar

2016-04-01

This study describes major changes in phytochemical composition of orthodox tea (Camellia sinensis var. Assamica) oxidized under compressed air (CA). The experiments for oxidation were conducted under air pressure (101, 202, and 303 kPa) for 150 min. Relative change in the concentrations of caffeine, catechins, theaflavins (TF), and thearubigins (TR) were analyzed. Effect of CA pressure was found to be nonsignificant in regulating caffeine concentration during oxidation. But degradation in different catechins as well as formation of different TF was significantly affected by CA pressure. At high CA pressure, TF showed highest peak value. TR was found to have slower rate of formation during initial phase of oxidation than TF. Even though the rate of TR formation was significantly influenced by CA, a portion of catechins remained unoxidized at end of oxidation. Except caffeine, the percent change in rate of formation or degradation were more prominent at 202 kPa. © 2016 Institute of Food Technologists®

Effect of wave action on near-well zone cleaning

NASA Astrophysics Data System (ADS)

Pen'kovskii, V. I.; Korsakova, N. K.

2017-10-01

Drilling filtrate invasion into the producing formation and native water accumulating of the near-well zone in well operation reduce the well productivity. As a result of that, depending on characteristic capillary pressure scale and differential pressure drawdown, oil production rate may become lower than expected one. In this paper, it is considered the hysteresis effects of capillary pressure after reversion of displacement. As applied to laboratory experiment conditions, the solution of problem of oil flow in formation model with a pressure drop on the model sides harmonically varied with time is presented. It was estimated a range of fluid vibration effective action on the near-well zone cleaning from capillary locking water. The plant simulating extraction of oil from formation using widely practised sucker-rod pump has been created. Formation model is presented as a slot filled with broken glass between two plates. In the process, natural oil and sodium chloride solution were used as working fluids. The experiments qualitatively confirm a positive effect of jack pumps on the near-well zone cleaning.

Conductivity affects nanosecond electrical pulse induced pressure transient formation

NASA Astrophysics Data System (ADS)

Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.; Beier, Hope T.; Glickman, Randolph D.

2016-03-01

Nanoporation occurs in cells exposed to high amplitude short duration (< 1μs) electrical pulses. The biophysical mechanism(s) responsible for nanoporation is unknown although several theories exist. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. Our group has shown that mechanical forces of substantial magnitude are also generated during nsEP exposures. We hypothesize that these mechanical forces may contribute to pore formation. In this paper, we report that alteration of the conductivity of the exposure solution also altered the level of mechanical forces generated during a nsEP exposure. By reducing the conductivity of the exposure solutions, we found that we could completely eliminate any pressure transients normally created by nsEP exposure. The data collected for this proceeding does not definitively show that the pressure transients previously identified contribute to nanoporation; however; it indicates that conductivity influences both survival and pressure transient formation.

Effect of plasticity and atmospheric pressure on the formation of donut- and croissantlike buckles.

PubMed

Hamade, S; Durinck, J; Parry, G; Coupeau, C; Cimetière, A; Grilhé, J; Colin, J

2015-01-01

The formation of donut- and croissantlike buckles has been observed onto the free surface of gold thin films deposited on silicon substrates. Numerical simulations clearly evidence that the coupling effect between the atmospheric pressure acting on the free surface and the plastic folding of the ductile film is responsible for the circular blister destabilization and the formation of the donut- and croissantlike buckling patterns.

Acoustic velocity in rift basin mudstones: effects of in situ stress and sample lithology, and its relation to formation strength

NASA Astrophysics Data System (ADS)

Zakharova, N. V.; Goldberg, D.

2017-12-01

Acoustic/sonic velocity (Vp) provides one of the best proxies for formation strength, which is essential for geomechanical modeling and formation evaluation. Vp-strength relations need to be built empirically for specific basins and/or rock types. Since velocity is stress- and frequency-dependent, such relations can be very sensitive to experimental conditions; therefore, it is important to quantify their effect on velocity values. In this study, we present confined velocity and strength measurements for over 70 samples from the Newark Rift basin, a candidate site for carbon sequestration, and one of the largest in a series of the Mesozoic rift basins on the eastern North-American coast. Acoustic velocity measurements were obtained for a range of confining pressures from 0 to 6,000 psi, roughly corresponding to in situ confining pressure range. Although, overall, Vp values tend to increase with increasing pressure, the degree of Vp response to stress varies dramatically from sample to sample, and does not appear to correlate directly to lithology or porosity. Select samples exhibit near-zero change in Vp with increasing confining pressure, while others are characterized by up to 15% Vp change with 3,000 psi increase in confining pressure. Compared to sonic logs, the low-stress Vp values usually underestimate sonic velocities, while high-stress values tend to overestimate them. Therefore, a systematic frequency-dependent core-log difference is not observed in these rift basin formations, but accounting for Vp dependence on confining pressure is important. We quantify the Vp-pressure dependence using laboratory acoustic measurements, and develop depth-dependent Vp-strength relation, which could be used with sonic logs for geomechanical analysis in similar Mesozoic rift basin formations.

Modeling the Buildup of Annular Pressure in Cased and Uncased Annuli of Faulty Wellbores

NASA Astrophysics Data System (ADS)

Lackey, G.; Rajaram, H.

2017-12-01

Structurally sound wellbores are essential to oil and gas production, natural gas storage, and carbon dioxide sequestration operations. Wellbore integrity is easily assessed at the wellhead by the presence of pressure or gas flow in the outer annuli of a well, as it indicates the uncontrolled vertical migration of fluids outside the production casing. This phenomenon is typically referred to as sustained casing pressure (SCP), sustained annular pressure, or surface casing vent flow. Of particular concern is the buildup of pressure in the surface casing annulus. If the surface casing is sealed at the wellhead and cement is not brought into the bottom of the casing, annular pressure that builds induces gas migration when the fluid and entry pressure of the formation at the bottom of the surface casing is exceeded. Multiple incidents of stray gas migration from oil and gas operations have contaminated water wells in Colorado, Pennsylvania, and Ohio through this mechanism. Natural gas escaping the #25 Standard Senson well at the Aliso Gas storage facility in California, the largest accidental release of greenhouse gases in US history, also followed this pathway. Previous studies have modeled the buildup of SCP in faulty wells with fully-cased annuli that are isolated from the surrounding formation. However, the majority of onshore oil and gas wells in the US are constructed with uncased outermost annuli that are hydraulically connected to the surrounding subsurface. In this study, we adapt current approaches of modeling SCP to include the regulation of annular liquid level by formation fluid pressure, dissolution of gas into the annular liquids, the transport of aqueous gas by crossflow into deep formations, and gas migration away from the well, when the entry pressure of the formations or fractures along the uncased annulus is exceeded, to compare the buildup behavior of SCP in both uncased and fully-cased annuli. We consider well construction and subsurface geology representative of the Wattenberg Field in Colorado and interpret observations of sustained casing pressure collected by the Colorado Oil and Gas Conservation Commission. We demonstrate that the potential negative consequences of integrity loss are much greater for an uncased well than for fully-cased well.

Long Term Observations of Subsurface Pore Pressure in the Kumano Basin and Upper Accretionary Wedge along the NanTroSIEZE Transect, offshore Japan: Signals from the 2011 Tohoku Earthquake

NASA Astrophysics Data System (ADS)

Zhang, Y.; Saffer, D. M.

2013-12-01

Subsurface pore pressure as a sensitive measure of strain and formation properties has provided insights into the wide range of fault slip behaviors, contributing to the understanding of fault and earthquake mechanics. Pore pressures from off shore borehole observatory are especially important, as 1) they are the only detectable signals of small and slow events; 2) they provide our only access to the outer forearc, where the tsunami hazards are triggered by the fault slip. As part of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) a suite of borehole sensors were installed as part of a long-term borehole observatory at IODP Site C0002, during IODP Expedition # 332 in December of 2010. The observatory includes a broadband seismometer, short period geophones, a volumetric strainmeter, temperature sensors, an accelerometer, and formation pore pressure monitoring at two depths: one in the mudstones of the Kumano Basin in an interval spanning 757-780 meters below seafloor (mbsf), and a second in the uppermost accretionary wedge in an interval from 937 - 980 mbsf. Here, we report on pore pressure records acquired at a sampling frequency of 1/60 Hz, spanning the period from December 2010 to January 2013, which were recovered in early 2013. We observe a clear hydraulic signal from March 11, 2011 Tohoku earthquake and aftershocks, including both dynamic pore pressure changes during passage of surface waves and shifts in formation pressure following the event. Pressure exhibit an increase of ~3 kPa in the upper sediment screened interval following the earthquake, and decrease by ~5 kPa in the accretionary prism interval. Both of the offset changes persist through the end of the data recording. These pore pressure changes may reflect static stress changes from the earthquake, or local site effects related to shaking. We also observe a clear increase in formation pore pressures associated with drilling operations at nearby holes in November and December 2012. These inadvertent two-well tests provide information about formation hydraulic properties at the ~20-50 m scale.

CO2 hydrate formation and dissociation in cooled porous media: a potential technology for CO2 capture and storage.

PubMed

Yang, Mingjun; Song, Yongchen; Jiang, Lanlan; Zhu, Ningjun; Liu, Yu; Zhao, Yuechao; Dou, Binlin; Li, Qingping

2013-09-03

The purpose of this study was to investigate the hydrate formation and dissociation with CO2 flowing through cooled porous media at different flow rates, pressures, temperatures, and flow directions. CO2 hydrate saturation was quantified using the mean intensity of water. The experimental results showed that the hydrate block appeared frequently, and it could be avoided by stopping CO2 flooding early. Hydrate formed rapidly as the temperature was set to 274.15 or 275.15 K, but the hydrate formation delayed when it was 276.15 K. The flow rate was an important parameter for hydrate formation; a too high or too low rate was not suitable for CO2 hydration formation. A low operating pressure was also unacceptable. The gravity made hydrate form easily in the vertically upward flow direction. The pore water of the second cycle converted to hydrate more completely than that of the first cycle, which was a proof of the hydrate "memory effect". When the pressure was equal to atmospheric pressure, hydrate did not dissociate rapidly and abundantly, and a long time or reduplicate depressurization should be used in industrial application.

Method for the measurement of susceptibility to decubitus ulcer formation.

PubMed

Meijer, J H; Schut, G L; Ribbe, M W; Goovaerts, H G; Nieuwenhuys, R; Reulen, J P; Schneider, H

1989-09-01

A method for measuring the susceptibility of a patient to develop decubitus ulcers is described and initially evaluated. It is based on an indirect, noninvasive measurement of the transient regional blood flow response after a test pressure load which simulates the external stimulus for pressure-sore formation. This method was developed to determine the individual risk of a patient and to study the subfactors which contribute to the susceptibility. This would also offer the possibility of evaluating the effect of preventive treatment aimed at reducing the susceptibility. The method was found to discriminate between preselected elderly patients at risk on the one hand, and non-risk patients and healthy young adults on the other hand. No differences in blood flow responses were found between the non-risk elderly patients and the healthy young adults. This suggests that age per se is not a factor in the formation of pressure sores. In the risk group the recovery time after pressure relief was found to be three times as long as the duration of the pressure exercise. This indicates that the recovery time after pressure exercise may be as important as the period of pressure exercise in deducing the risk of developing decubitus ulcers.

The Combined Effect of High Hydrostatic Pressure and Calcium Salts on the Stability, Solubility and Gel Formation of β-Lactoglobulin

PubMed Central

Saalfeld, Daniel; Riegel, Ina; Kulozik, Ulrich; Gebhardt, Ronald

2015-01-01

Stability, aggregation and gelation of β-Lactoglobulin are affected by high pressure and salts of the Hofmeister series. Little is known about their combined effects on structure formation processes of β-Lactoglobulin, mainly because many salts of the series are not suitable for use in food. Here, we investigate the effect of calcium salts on the strength of pressure-induced gels, inspired by the fact that high pressure and salts change the water structure in a similar way. We find that the larger the applied pressures, the higher the strength of the gels. In addition to pressure, there is a significant influence by the type of anions and the amount of added calcium salts. Gel strength increases in the order CaCl2 < Ca (NO3)2 < CaI2. This trend correlates with the position of the salts in the Hofmeister series. The results are explained by analogy with the thermal aggregate formation by taking reaction rates for unfolding and aggregation, as well as specific/non-specific salts effect into consideration. PMID:28231200

A novel scaling approach for sooting laminar coflow flames at elevated pressures

NASA Astrophysics Data System (ADS)

Abdelgadir, Ahmed; Steinmetz, Scott A.; Attili, Antonio; Bisetti, Fabrizio; Roberts, William L.

2016-11-01

Laminar coflow diffusion flames are often used to study soot formation at elevated pressures due to their well-characterized configuration. In these expriments, these flames are operated at constant mass flow rate (constant Reynolds number) at increasing pressures. Due to the effect of gravity, the flame shape changes and as a results, the mixing field changes, which in return has a great effect on soot formation. In this study, a novel scaling approach of the flame at different pressures is proposed. In this approach, both the Reynolds and Grashof's numbers are kept constant so that the effect of gravity is the same at all pressures. In order to keep the Grashof number constant, the diameter of the nozzle is modified as pressure varies. We report both numerical and experimental data proving that this approach guarantees the same nondimensional flow fields over a broad range of pressures. In the range of conditions studied, the Damkoehler number, which varies when both Reynolds and Grashof numbers are kept constant, is shown to play a minor role. Hence, a set of suitable flames for investigating soot formation at pressure is identified. This research made use of the resources of IT Research Computing at King Abdullah University of Science & Technology (KAUST), Saudi Arabia.

Acoustic Effects in Classical Nucleation Theory

NASA Technical Reports Server (NTRS)

Baird, J. K.; Su, C.-H.

2017-01-01

The effect of sound wave oscillations on the rate of nucleation in a parent phase can be calculated by expanding the free energy of formation of a nucleus of the second phase in powers of the acoustic pressure. Since the period of sound wave oscillation is much shorter than the time scale for nucleation, the acoustic effect can be calculated as a time average of the free energy of formation of the nucleus. The leading non-zero term in the time average of the free energy is proportional to the square of the acoustic pressure. The Young-Laplace equation for the surface tension of the nucleus can be used to link the time average of the square of the pressure in the parent phase to its time average in the nucleus of the second phase. Due to the surface tension, the pressure in the nuclear phase is higher than the pressure in the parent phase. The effect is to lower the free energy of formation of the nucleus and increase the rate of nucleation.

Operational design and pressure response of large-scale compressed air energy storage in porous formations

NASA Astrophysics Data System (ADS)

Wang, Bo; Bauer, Sebastian

2017-04-01

With the rapid growth of energy production from intermittent renewable sources like wind and solar power plants, large-scale energy storage options are required to compensate for fluctuating power generation on different time scales. Compressed air energy storage (CAES) in porous formations is seen as a promising option for balancing short-term diurnal fluctuations. CAES is a power-to-power energy storage, which converts electricity to mechanical energy, i.e. highly pressurized air, and stores it in the subsurface. This study aims at designing the storage setup and quantifying the pressure response of a large-scale CAES operation in a porous sandstone formation, thus assessing the feasibility of this storage option. For this, numerical modelling of a synthetic site and a synthetic operational cycle is applied. A hypothetic CAES scenario using a typical anticline structure in northern Germany was investigated. The top of the storage formation is at 700 m depth and the thickness is 20 m. The porosity and permeability were assumed to have a homogenous distribution with a value of 0.35 and 500 mD, respectively. According to the specifications of the Huntorf CAES power plant, a gas turbine producing 321 MW power with a minimum inlet pressure of 43 bars at an air mass flowrate of 417 kg/s was assumed. Pressure loss in the gas wells was accounted for using an analytical solution, which defines a minimum bottom hole pressure of 47 bars. Two daily extraction cycles of 6 hours each were set to the early morning and the late afternoon in order to bypass the massive solar energy production around noon. A two-year initial filling of the reservoir with air and ten years of daily cyclic operation were numerically simulated using the Eclipse E300 reservoir simulator. The simulation results show that using 12 wells the storage formation with a permeability of 500 mD can support the required 6-hour continuous power output of 321MW, which corresponds an energy output of 3852 MWh per day. The average bottom hole pressure is 87 bars at the beginning of cyclic operation and reduces to 79 bars after 10 years. This pressure drop over time is caused by the open boundary conditions defined at the model edges and is not influenced by the cyclic operation. In the storage formation, the pressure response induced by the initial filling can be observed in the whole model domain, and a maximum pressure built-up of about 31 bars and 3 bars are observed near the wells and at a distance of 10 km from the wells, respectively. During the cyclic operation, however, pressure fluctuations of more than 1 bar can only be observed within the gas phase. Assuming formations with different permeabilities, a sensitivity analysis is carried out to find the number of wells required. Results show that the number of wells required does not linearly decrease with increasing permeability of the storage formation due to well interference during air extraction.

The granin VGF promotes genesis of secretory vesicles, and regulates circulating catecholamine levels and blood pressure.

PubMed

Fargali, Samira; Garcia, Angelo L; Sadahiro, Masato; Jiang, Cheng; Janssen, William G; Lin, Wei-Jye; Cogliani, Valeria; Elste, Alice; Mortillo, Steven; Cero, Cheryl; Veitenheimer, Britta; Graiani, Gallia; Pasinetti, Giulio M; Mahata, Sushil K; Osborn, John W; Huntley, George W; Phillips, Greg R; Benson, Deanna L; Bartolomucci, Alessandro; Salton, Stephen R

2014-05-01

Secretion of proteins and neurotransmitters from large dense core vesicles (LDCVs) is a highly regulated process. Adrenal LDCV formation involves the granin proteins chromogranin A (CgA) and chromogranin B (CgB); CgA- and CgB-derived peptides regulate catecholamine levels and blood pressure. We investigated function of the granin VGF (nonacronymic) in LDCV formation and the regulation of catecholamine levels and blood pressure. Expression of exogenous VGF in nonendocrine NIH 3T3 fibroblasts resulted in the formation of LDCV-like structures and depolarization-induced VGF secretion. Analysis of germline VGF-knockout mouse adrenal medulla revealed decreased LDCV size in noradrenergic chromaffin cells, increased adrenal norepinephrine and epinephrine content and circulating plasma epinephrine, and decreased adrenal CgB. These neurochemical changes in VGF-knockout mice were associated with hypertension. Germline knock-in of human VGF1-615 into the mouse Vgf locus rescued the hypertensive knockout phenotype, while knock-in of a truncated human VGF1-524 that lacks several C-terminal peptides, including TLQP-21, resulted in a small but significant increase in systolic blood pressure compared to hVGF1-615 mice. Finally, acute and chronic administration of the VGF-derived peptide TLQP-21 to rodents decreased blood pressure. Our studies establish a role for VGF in adrenal LDCV formation and the regulation of catecholamine levels and blood pressure.

Association between presence of pneumonia and pressure ulcer formation following traumatic spinal cord injury.

PubMed

Krishnan, Shilpa; Karg, Patricia E; Boninger, Michael L; Brienza, David M

2017-07-01

To determine if the presence of pneumonia and pressure ulcers are associated in individuals with an acute spinal cord injury during acute care and rehabilitation hospitalizations. Retrospective, secondary analyses of data obtained from the Spinal Cord Injury Model Systems enrolled from 1993 until 2006 Setting: Acute care hospitalization and inpatient rehabilitation facilities Participants: A cohort of individuals hospitalized in acute care (n = 3,098) and inpatient rehabilitation (n = 1,768) was included in the analysis. Frequencies of pressure ulcer formation and episodes of pneumonia were noted in both settings. Not applicable. Pressure ulcer formation and diagnosis of pneumonia Results: The development of pressure ulcers, including stage I, was 20.3% acute care and 21.1% during in inpatient rehabilitation. Multivariate logistic regression analyses revealed a significant association of pneumonia with occurrence of pressure ulcers (P ≤ 0.001, OR = 2.3 and 2.2 respectively), the American Spinal Injury Association Impairment Scale grades (P < 0.001), and utilization of mechanical ventilation (P < 0.01) in both settings. A higher presence of pressure ulcers was found in individuals with pneumonia, after adjusting for injury severity, age, sex, and utilization of mechanical ventilation. Impaired inflammatory response and decreased mobility in individuals with pneumonia may predispose these individuals to develop pressure ulcers. Surveillance and preventive measures for pressure ulcers should be rigorous in individuals with SCI and pneumonia.

Pore Formation During Solidification of Aluminum: Reconciliation of Experimental Observations, Modeling Assumptions, and Classical Nucleation Theory

NASA Astrophysics Data System (ADS)

Yousefian, Pedram; Tiryakioğlu, Murat

2018-02-01

An in-depth discussion of pore formation is presented in this paper by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory for homogeneous and heterogeneous nucleation, with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and the corresponding probability of vacancies clustering to form that size have been calculated using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with the reinterpretations of in situ observations as well as the assumptions made in the literature to model pore formation.

Method for laser drilling subterranean earth formations

DOEpatents

Shuck, Lowell Z.

1976-08-31

Laser drilling of subterranean earth formations is efficiently accomplished by directing a collimated laser beam into a bore hole in registry with the earth formation and transversely directing the laser beam into the earth formation with a suitable reflector. In accordance with the present invention, the bore hole is highly pressurized with a gas so that as the laser beam penetrates the earth formation the high pressure gas forces the fluids resulting from the drilling operation into fissures and pores surrounding the laser-drilled bore so as to inhibit deleterious occlusion of the laser beam. Also, the laser beam may be dynamically programmed with some time dependent wave form, e.g., pulsed, to thermally shock the earth formation for forming or enlarging fluid-receiving fissures in the bore.

Globular cluster formation - The fossil record

NASA Technical Reports Server (NTRS)

Murray, Stephen D.; Lin, Douglas N. C.

1992-01-01

Properties of globular clusters which have remained unchanged since their formation are used to infer the internal pressures, cooling times, and dynamical times of the protocluster clouds immediately prior to the onset of star formation. For all globular clusters examined, it is found that the cooling times are much less than the dynamical times, implying that the protoclusters must have been maintained in thermal equilibrium by external heat sources, with fluxes consistent with those found in previous work, and giving the observed rho-T relation. Self-gravitating clouds cannot be stably heated, so that the Jeans mass forms an upper limit to the cluster masses. The observed dependence of protocluster pressure upon galactocentric position implies that the protocluster clouds were in hydrostatic equilibrium after their formation. The pressure dependence is well fitted by that expected for a quasi-statically evolving background hot gas, shock heated to its virial temperature. The observations and inferences are combined with previous theoretical work to construct a picture of globular cluster formation.

Shear Stress-Normal Stress (Pressure) Ratio Decides Forming Callus in Patients with Diabetic Neuropathy

PubMed Central

Noguchi, Hiroshi; Takehara, Kimie; Ohashi, Yumiko; Suzuki, Ryo; Yamauchi, Toshimasa; Kadowaki, Takashi; Sanada, Hiromi

2016-01-01

Aim. Callus is a risk factor, leading to severe diabetic foot ulcer; thus, prevention of callus formation is important. However, normal stress (pressure) and shear stress associated with callus have not been clarified. Additionally, as new valuables, a shear stress-normal stress (pressure) ratio (SPR) was examined. The purpose was to clarify the external force associated with callus formation in patients with diabetic neuropathy. Methods. The external force of the 1st, 2nd, and 5th metatarsal head (MTH) as callus predilection regions was measured. The SPR was calculated by dividing shear stress by normal stress (pressure), concretely, peak values (SPR-p) and time integral values (SPR-i). The optimal cut-off point was determined. Results. Callus formation region of the 1st and 2nd MTH had high SPR-i rather than noncallus formation region. The cut-off value of the 1st MTH was 0.60 and the 2nd MTH was 0.50. For the 5th MTH, variables pertaining to the external forces could not be determined to be indicators of callus formation because of low accuracy. Conclusions. The callus formation cut-off values of the 1st and 2nd MTH were clarified. In the future, it will be necessary to confirm the effect of using appropriate footwear and gait training on lowering SPR-i. PMID:28050567

Effects of control parameters of three-point initiation on the formation of an explosively formed projectile with fins

NASA Astrophysics Data System (ADS)

Li, R.; Li, W. B.; Wang, X. M.; Li, W. B.

2018-03-01

The effects of the initiation diameter and synchronicity error on the formation of fins and stable-flight velocity of an explosively formed projectile (EFP) with three-point initiation are investigated. The pressure and area of the Mach wave acting on the metal liner at different initiation diameters are calculated employing the Whitham method. LS-DYNA software is used to investigate the asymmetric collision of detonation waves resulting from three-point initiation synchronicity error, the distortion characteristics of the liner resulting from the composite detonation waves, and the performance parameters of the EFP with fins. Results indicate that deviations of the Y-shaped high-pressure zone and central ultrahigh-pressure zone from the liner center can be attributed to the error of three-point initiation, which leads to the irregular formation of EFP fins. It is noted that the area of the Mach wave decreases, but the pressure of the Mach wave and the final speed and length-to-diameter ( L/ D) ratio of the EFP increase, benefiting the formation of the EFP fins, as the initiation diameter increases.

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.

High-pressure minerals in shocked meteorites

NASA Astrophysics Data System (ADS)

Tomioka, Naotaka; Miyahara, Masaaki

2017-09-01

Heavily shocked meteorites contain various types of high-pressure polymorphs of major minerals (olivine, pyroxene, feldspar, and quartz) and accessory minerals (chromite and Ca phosphate). These high-pressure minerals are micron to submicron sized and occur within and in the vicinity of shock-induced melt veins and melt pockets in chondrites and lunar, howardite-eucrite-diogenite (HED), and Martian meteorites. Their occurrence suggests two types of formation mechanisms (1) solid-state high-pressure transformation of the host-rock minerals into monomineralic polycrystalline aggregates, and (2) crystallization of chondritic or monomineralic melts under high pressure. Based on experimentally determined phase relations, their formation pressures are limited to the pressure range up to 25 GPa. Textural, crystallographic, and chemical characteristics of high-pressure minerals provide clues about the impact events of meteorite parent bodies, including their size and mutual collision velocities and about the mineralogy of deep planetary interiors. The aim of this article is to review and summarize the findings on natural high-pressure minerals in shocked meteorites that have been reported over the past 50 years.

Intracellular pressure is a motive force for cell motion in Amoeba proteus.

PubMed

Yanai, M; Kenyon, C M; Butler, J P; Macklem, P T; Kelly, S M

1996-01-01

The cortical filament layer of free-living amoebae contains concentrated actomyosin, suggesting that it can contract and produce an internal hydrostatic pressure. We report here on direct and dynamic intracellular pressure (P(ic)) measurements in Amoeba proteus made using the servo-null technique. In resting apolar A. proteus, P(ic) increased while the cells remained immobile and at apparently constant volume. P(ic) then decreased approximately coincident with pseudopod formation. There was a positive correlation between P(ic) at the onset of movement and the rate of pseudopod formation. These results are the first direct evidence that hydrostatic pressure may be a motive force for cell motion. We postulate that contractile elements in the amoeba's cortical layer contract and increase P(ic) and that this P(ic) is utilized to overcome the viscous flow resistance of the intracellular contents during pseudopod formation.

The use of additive ceramic hollow spheres on cement slurry to prevent lost circulation in formation `X' having low pressure fracture

NASA Astrophysics Data System (ADS)

Rita, Novia; Mursyidah, Syahindra, Michael

2018-03-01

When drilling, if the hydrostatic pressure is higher than formation pressure (fracture pressure) it will cause lost circulation during cementing process. To solve this problem, hydrostatic pressure of slurry can be decreased by lowering the slurry density by using some additives. Ceramic Hollow Spheres (CHS) is lightweight additive. This additive comes with low specific gravity so it can lowered the slurry density. When the low-density slurry used in cementing process, it can prevent low circulation and fractured formation caused by cement itself. Class G cement is used in this experiment with the standard density of this slurry is 15.8 ppg. With the addition of CHS, slurry density lowered to 12.5 ppg. CHS not only used to lower the slurry density, it also used to make the same properties with the standard slurry even the density has been lowered. Both thickening time and compressive strength have not change if the CHS added to the slurry. With addition of CHS, thickening time at 70 Bc reached in 03 hours 12 minutes. For the compressive strength, 2000 psi reached in 07 hours 07 minutes. Addition of CHS can save more time in cementing process of X formation.

The influence of the cluster environment on the star formation efficiency of 12 Virgo spiral galaxies

NASA Astrophysics Data System (ADS)

Vollmer, B.; Wong, O. I.; Braine, J.; Chung, A.; Kenney, J. D. P.

2012-07-01

The influence of the environment on gas surface density and star formation efficiency of cluster spiral galaxies is investigated. We extend previous work on radial profiles by a pixel-to pixel analysis looking for asymmetries due to environmental interactions. The star formation rate is derived from GALEX UV and Spitzer total infrared data based on the 8, 24, 70, and 160 μm data. As in field galaxies, the star formation rate for most Virgo galaxies is approximately proportional to the molecular gas mass. Except for NGC 4438, the cluster environment does not affect the star formation efficiency with respect to the molecular gas. Gas truncation is not associated with major changes in the total gas surface density distribution of the inner disk of Virgo spiral galaxies. In three galaxies (NGC 4430, NGC 4501, and NGC 4522), possible increases in the molecular fraction and the star formation efficiency with respect to the total gas, of factors of 1.5 to 2, are observed on the windward side of the galactic disk. A significant increase of the star formation efficiency with respect to the molecular gas content on the windward side of ram pressure-stripped galaxies is not observed. The ram-pressure stripped extraplanar gas of 3 highly inclined spiral galaxies (NGC 4330, NGC 4438, and NGC 4522) shows a depressed star formation efficiency with respect to the total gas, and one of them (NGC 4438) shows a depressed rate even with respect to the molecular gas. The interpretation is that stripped gas loses the gravitational confinement and associated pressure of the galactic disk, and the gas flow is diverging, so the gas density decreases and the star formation rate drops. We found two such regions of low star formation efficiency in the more face-on galaxies NGC 4501 and NGC 4654 which are both undergoing ram pressure stripping. These regions show low radio continuum emission or unusually steep radio spectral index. However, the stripped extraplanar gas in one highly inclined galaxy (NGC 4569) shows a normal star formation efficiency with respect to the total gas. We propose this galaxy is different because it is observed long after peak pressure, and its extraplanar gas is now in a converging flow as it resettles back into the disk. Appendices are available in electronic form http://www.aanda.org

Cenosphere formation from heavy fuel oil: a numerical analysis accounting for the balance between porous shells and internal pressure

NASA Astrophysics Data System (ADS)

Reddy, Vanteru M.; Rahman, Mustafa M.; Gandi, Appala N.; Elbaz, Ayman M.; Schrecengost, Robert A.; Roberts, William L.

2016-01-01

Heavy fuel oil (HFO) as a fuel in industrial and power generation plants ensures the availability of energy at economy. Coke and cenosphere emissions from HFO combustion need to be controlled by particulate control equipment such as electrostatic precipitators, and collection effectiveness is impacted by the properties of these particulates. The cenosphere formation is a function of HFO composition, which varies depending on the source of the HFO. Numerical modelling of the cenosphere formation mechanism presented in this paper is an economical method of characterising cenosphere formation potential for HFO in comparison to experimental analysis of individual HFO samples, leading to better control and collection. In the present work, a novel numerical model is developed for understanding the global cenosphere formation mechanism. The critical diameter of the cenosphere is modelled based on the balance between two pressures developed in an HFO droplet. First is the pressure (Prpf) developed at the interface of the liquid surface and the inner surface of the accumulated coke due to the flow restriction of volatile components from the interior of the droplet. Second is the pressure due to the outer shell strength (PrC) gained from van der Walls energy of the coke layers and surface energy. In this present study it is considered that when PrC ≥ Prpf the outer shell starts to harden. The internal motion in the shell layer ceases and the outer diameter (DSOut) of the shell is then fixed. The entire process of cenosphere formation in this study is analysed in three phases: regression, shell formation and hardening, and post shell hardening. Variations in pressures during shell formation are analysed. Shell (cenosphere) dimensions are evaluated at the completion of droplet evaporation. The rate of fuel evaporation, rate of coke formation and coke accumulation are analysed. The model predicts shell outer diameters of 650, 860 and 1040 µm, and inner diameters are 360, 410 and 430 µm respectively, for 700, 900 and 1100 µm HFO droplets. The present numerical model is validated with experimental results available from the literature. Total variation between computational and experimental results is in the range of 3-7%.

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

NASA Technical Reports Server (NTRS)

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

2008-01-01

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

Influence of operating pressure on the biological hydrogen methanation in trickle-bed reactors.

PubMed

Ullrich, Timo; Lindner, Jonas; Bär, Katharina; Mörs, Friedemann; Graf, Frank; Lemmer, Andreas

2018-01-01

In order to investigate the influence of pressures up to 9bar absolute on the productivity of trickle-bed reactors for biological methanation of hydrogen and carbon dioxide, experiments were carried out in a continuously operated experimental plant with three identical reactors. The pressure increase promises a longer residence time and improved mass transfer of H 2 due to higher gas partial pressures. The study covers effects of different pressures on important parameters like gas hourly space velocity, methane formation rate, conversion rates and product gas quality. The methane content of 64.13±3.81vol-% at 1.5bar could be increased up to 86.51±0.49vol-% by raising the pressure to 9bar. Methane formation rates of up to 4.28±0.26m 3 m -3 d -1 were achieved. Thus, pressure increase could significantly improve reactor performance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Review on pressure swirl injector in liquid rocket engine

NASA Astrophysics Data System (ADS)

Kang, Zhongtao; Wang, Zhen-guo; Li, Qinglian; Cheng, Peng

2018-04-01

The pressure swirl injector with tangential inlet ports is widely used in liquid rocket engine. Commonly, this type of pressure swirl injector consists of tangential inlet ports, a swirl chamber, a converging spin chamber, and a discharge orifice. The atomization of the liquid propellants includes the formation of liquid film, primary breakup and secondary atomization. And the back pressure and temperature in the combustion chamber could have great influence on the atomization of the injector. What's more, when the combustion instability occurs, the pressure oscillation could further affects the atomization process. This paper reviewed the primary atomization and the performance of the pressure swirl injector, which include the formation of the conical liquid film, the breakup and atomization characteristics of the conical liquid film, the effects of the rocket engine environment, and the response of the injector and atomization on the pressure oscillation.

Shock tube study of the fuel structure effects on the chemical kinetic mechanisms responsible for soot formation

NASA Technical Reports Server (NTRS)

Frenklach, M.

1983-01-01

Soot formation in toluene-, benzene-, and acetylene-oxygen-argon mixtures was investigated to study soot formation in a combustion environment. High concentrations of oxygen completely suppress soot formation. The addition of oxygen at relatively low concentrations uniformly suppresses soot formation at high pressures, while at relatively lower pressures it suppresses soot formation at higher temperatures while promoting soot production at lower temperatures. The observed behavior indicates that oxidation reactions compete with ring fragmentation. The main conclusion to be drawn from the results is that the soot formation mechanism is probably the same for the pyrolysis and oxidation of hydrocarbons. That is, the addition of oxygen does not alter the soot route but rather promotes or inhibits this route by means of competitive reactions. An approach to empirical modeling of soot formation during pyrolysis of aromatic hydrocarbons is also presented.

Overpressure Prediction From Seismic Data: Implications on Drilling Safety

NASA Astrophysics Data System (ADS)

Osinowo, O. O.; Oladunjoye, M. A.; Olayinka, A. I.

2007-12-01

High rate of sediment influx into the Niger Delta via river Niger coupled with high rate of basin subsidence, very thick clayey members of Agbada and Akata Formations as well as prevailing presence of growth faults had been identified as the main factors responsible for overpressure generation and preservation in the Niger Delta basin. Analysis of porosity dependent parameters such as interval transit times and interval velocities derived from the seismic records of a field in the Western Niger Delta revealed the presence of overpressured formation at depth of 8670 feet, which is the top of the overpressured zone. The plot of interval transit times against depth gave a positive deflection from normal at the region of overpressure while interval velocity plot gave negative deflection; the ratio of this deviation in both cases is as high as 1.52. Pressure gradient in the upper, normally pressured part of the field was determined to be 0.465 psi/ft., which is within the established normal pressure gradient range in Niger Delta, while the abnormal formation pressure gradient in the overpressured region was determined to be 0.96 psi/ft., and this is also within the published abnormal pressure gradient range of 0.71 to 1.1 psi/ft. in Niger Delta. Formation fracture pressure gradients were determined from the formation pressure information to be 0.66psi/ft. in the upper part of the field and 1.2psi/ft. in the overpressured horizon. Mud weight window (MWW); mud density range necessary to prevent formation kick without initiating hydraulic fracturing was determined to be 10.2 to 12.5lbm/gal in the upper part of the field and 22.1 to 22.63lbm/gal in the overpressured horizon. MWW is indispensable for the selection of the mud pump type, capacity, pumping rate and mud densities at different formation pressure regimes. Overpressure prediction is also requisite for drilling program design, casing design as well as rig capacity choice before spudding. It is necessary to reduce well construction risk, save drilling hour as well as cut down drilling cost. If adequate predictions are not taken however, drilling hazards known as blowout may occur. Blowout, an uncontrollable flow of formation fluid into the well has made oil exploration and exploitation activities in Niger Delta, Southern Nigeria, a curse for the people rather than a blessing because considerable numbers of wells blew out during well construction activities, hence the characteristic oil spill which had degraded the environment, making fishing operation, a source of livelihood of the people difficult. Therefore the need for overpressure prediction as a guide for safe drilling, especially in unfamiliar exploration environments.

Role of vortices in cavitation formation in the flow across a mechanical heart valve.

PubMed

Li, Chi-Pei; Lu, Po-Chien; Liu, Jia-Shing; Lo, Chi-Wen; Hwang, Ned H

2008-07-01

Cavitation occurs during mechanical heart valve closure when the local pressure drops below vapor pressure. The formation of stable gas bubbles may result in gaseous emboli, and secondarily cause transient ischemic attacks or strokes. It is noted that instantaneous valve closure, occluder rebound and high-speed leakage flow generate vortices that promote low-pressure regions in favor of stable bubble formation; however, to date no studies have been conducted for the quantitative measurement and analysis of these vortices. A Björk-Shiley Monostrut (BSM) monoleaflet valve was placed in the mitral position of a pulsatile mock circulatory loop. Particle image velocimetry (PIV) and pico coulomb (PCB) pressure measurements were applied. Flow field measurements were carried out at t = -5, -3, -1, -0.5, 0 (valve closure), 0.3, 0.5, 0.75, 1.19, 1.44, 1.69, 1.94, 2, 2.19, 2.54, 2.79, 3.04, 3.29, 3.54, 5 and 10 ms. The vortices were quantitatively analyzed using the Rankine vortex model. A single counter-clockwise vortex was The instantaneous formation of cavitation bubbles at mechanical heart valve (MHV) closure, which subsequently damage blood cells and valve integrity, is a well-known and widely studied phenomenon (1-4). Contributing factors seem to include the water-hammer, squeeze flow and Venturi effects, all of which are short-lived. Both, Dauzat et al. (5) and Sliwka et al. (6) have detected high-intensity transient signals (HITS) with transcranial Doppler ultrasound in the carotid and cerebral arteries of MHV recipients, while Deklunder (7) observed clinical occurrences of cerebral gas emboli that were not seen with bioprosthetic valves. These detected over the major orifice, while a pair of counter-rotating vortices was found over the minor orifice. Velocity profiles were consistent with Rankine vortices. The vortex strength and magnitude of the pressure drop peaked shortly after initial occluder-housing impact and rapidly decreased after 0.5 ms, indicating viscous dissipation, with a less significant contribution from the occluder rebound effect. The maximum pressure drop was on the order of magnitude of 40 mmHg. Detailed PIV measurements and quantitative analysis of the BSM mechanical heart valve revealed large-scale vortex formation immediately after valve closure. Of note, the vortices were typical of a Rankine vortex and the maximum pressure change at the vortex center was only 40 mmHg. These data support the conclusion that vortex formation alone cannot generate the magnitude of pressure drop required for cavitation bubble formation.

Observed transition from Richtmyer-Meshkov jet formation through feedout oscillations to Rayleigh-Taylor instability in a laser target

NASA Astrophysics Data System (ADS)

Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Nikitin, S. P.; Metzler, N.; Oh, J.

2012-10-01

Experimental study of hydrodynamic perturbation evolution triggered by a laser-driven shock wave breakout at the free rippled rear surface of a plastic target is reported. We observed a transition between two qualitatively distinct types of perturbation evolution: jet formation at low shock pressure and areal mass oscillations at high shock pressure, which correspond respectively to high and low values of effective adiabatic index. The experiments were done on the KrF Nike laser facility with laser wavelength 248 nm and a 4 ns pulse. We varied the number of beams overlapped on the plastic target to change the ablative pressure driving the shock wave through the target: 36 beams produce pressure of ˜8 Mbar, whereas a single beam irradiation reduces the pressure to ˜0.7 Mbar. With the help of side-on monochromatic x-ray imaging, planar jets manifesting the development of the Richtmyer-Meshkov-type instability in a non-accelerated target are observed at sub-megabar shock pressure. As the shock pressure exceeds 1 Mbar, instead of jet formation an oscillatory rippled expansion wave is observed, followed by the ``feedout'' of the rear-surface perturbations to the ablation front and the development of the Rayleigh-Taylor instability, which breaks up the accelerated target.

Numerical Modelling of Extended Leak-Off Test with a Pre-Existing Fracture

NASA Astrophysics Data System (ADS)

Lavrov, A.; Larsen, I.; Bauer, A.

2016-04-01

Extended leak-off test (XLOT) is one of the few techniques available for stress measurements in oil and gas wells. Interpretation of the test is often difficult since the results depend on a multitude of factors, including the presence of natural or drilling-induced fractures in the near-well area. Coupled numerical modelling of XLOT has been performed to investigate the pressure behaviour during the flowback phase as well as the effect of a pre-existing fracture on the test results in a low-permeability formation. Essential features of XLOT known from field measurements are captured by the model, including the saw-tooth shape of the pressure vs injected volume curve, and the change of slope in the pressure vs time curve during flowback used by operators as an indicator of the bottomhole pressure reaching the minimum in situ stress. Simulations with a pre-existing fracture running from the borehole wall in the radial direction have revealed that the results of XLOT are quite sensitive to the orientation of the pre-existing fracture. In particular, the fracture initiation pressure and the formation breakdown pressure increase steadily with decreasing angle between the fracture and the minimum in situ stress. Our findings seem to invalidate the use of the fracture initiation pressure and the formation breakdown pressure for stress measurements or rock strength evaluation purposes.

Effect of Negative Pressure on Proliferation, Virulence Factor Secretion, Biofilm Formation, and Virulence-Regulated Gene Expression of Pseudomonas aeruginosa In Vitro

PubMed Central

Wang, Guo-Qi; Li, Tong-Tong; Li, Zhi-Rui; Zhang, Li-Cheng

2016-01-01

Objective. To investigate the effect of negative pressure conditions induced by NPWT on P. aeruginosa. Methods. P. aeruginosa was cultured in a Luria–Bertani medium at negative pressure of −125 mmHg for 24 h in the experimental group and at atmospheric pressure in the control group. The diameters of the colonies of P. aeruginosa were measured after 24 h. ELISA kit, orcinol method, and elastin-Congo red assay were used to quantify the virulence factors. Biofilm formation was observed by staining with Alexa Fluor® 647 conjugate of concanavalin A (Con A). Virulence-regulated genes were determined by quantitative RT-PCR. Results. As compared with the control group, growth of P. aeruginosa was inhibited by negative pressure. The colony size under negative pressure was significantly smaller in the experimental group than that in the controls (p < 0.01). Besides, reductions in the total amount of virulence factors were observed in the negative pressure group, including exotoxin A, rhamnolipid, and elastase. RT-PCR results revealed a significant inhibition in the expression level of virulence-regulated genes. Conclusion. Negative pressure could significantly inhibit the growth of P. aeruginosa. It led to a decrease in the virulence factor secretion, biofilm formation, and a reduction in the expression level of virulence-regulated genes. PMID:28074188

Project Rulison gas flow analysis

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

Montan, D.N.

1971-01-01

An analysis of the well performance was attempted by fitting a simple model of the chimney, gas sands, and explosively created fracturing to the 2 experimentally measured variables, flow rate, and chimney pressure. The gas-flow calculations for various trial models were done by a finite difference solution to the nonlinear partial differential equation for radial Darcy flow. The TRUMP computer program was used to perform the numerical calculations. In principle, either the flow rate or the chimney pressure could be used as the independent variable in the calculations. In the present case, the flow rate was used as the independentmore » variable, since chimney pressure measurements were not made until after the second flow period in early Nov. 1970. Furthermore, the formation pressure was not accurately known and, hence, was considered a variable parameter in the modeling process. The chimney pressure was assumed equal to the formation pressure at the beginning of the flow testing. The model consisted of a central zone, representing the chimney, surrounded by a number of concentric zones, representing the formation. The effect of explosive fracturing was simulated by increasing the permeability in the zones near the central zone.« less

Pressure-temperature evolution of Neoproterozoic metamorphism in the Welayati Formation (Kabul Block), Afghanistan

NASA Astrophysics Data System (ADS)

Collett, Stephen; Faryad, Shah Wali

2015-11-01

The Welayati Formation, consisting of alternating layers of mica-schist and quartzite with lenses of amphibolite, unconformably overlies the Neoarchean Sherdarwaza Formation of the Kabul Block that underwent Paleoproterozoic granulite-facies and Neoproterozoic amphibolite-facies metamorphic events. To analyze metamorphic history of the Welayati Formation and its relations to the underlying Sherdarwaza Formation, petrographic study and pressure-temperature (P-T) pseudosection modeling were applied to staurolite- and kyanite-bearing mica-schists, which crop out to the south of Kabul City. Prograde metamorphism, identified by inclusion trails and chemical zonation in garnet from the micaschists indicates that the rocks underwent burial from around 6.2 kbar at 525 °C to maximum pressure conditions of around 9.5 kbar at temperatures of around 650 °C. Decompression from peak pressures under isothermal or moderate heating conditions are indicated by formation of biotite and plagioclase porphyroblasts which cross-cut and overgrow the dominant foliation. The lack of sillimanite and/or andalusite suggests that cooling and further decompression occurred in the kyanite stability field. The results of this study indicate a single amphibolite-facies metamorphism that based on P-T conditions and age dating correlates well with the Neoproterozoic metamorphism in the underlying Sherdarwaza Formation. The rocks lack any paragenetic evidence for a preceding granulite-facies overprint or subsequent Paleozoic metamorphism. Owing to the position of the Kabul Block, within the India-Eurasia collision zone, partial replacement of the amphibolite-facies minerals in the micaschist could, in addition to retrogression of the Neoproterozoic metamorphism, relate to deformation associated with the Alpine orogeny.

Scaling the Morphology of Sapping and Pressurized Groundwater Experiments to Martian Valleys

NASA Astrophysics Data System (ADS)

Marra, W. A.; Kleinhans, M. G.

2013-12-01

Various valleys exist on Mars, which shows the former existence of fluvial activity and thus liquid water at the surface. Although these valleys show similarities with some valleys on Earth, many morphological features are unique for Mars or are very rare on Earth. Therefore, we lack knowledge about the formative processes of these enigmatic valleys. In this study, we explored possible groundwater scenarios for the formation of these valleys using flume experiments, as there are no pure Earth analogues for these systems. We aim to infer their formative processes from morphological properties. A series of flume experiments were carried out in a 4x6x1 m experimental setup, where we observed the valley formation as result from seeping groundwater by both local and distal groundwater sources and by pressurized groundwater release. Time-lapse imagery and DEMs of the experiments show the morphological development, associated processes, and landscape evolution. Indicators of the processes where we particularly looked at were changes in valley slope, cross-sectional shape, the relations between valley dimensions, and regional landscape properties as drainage density and valley size distributions. Hydrological modelling assists in scaling the observed experimental features to real-world systems. Additionally, we looked at valleys on Earth in the Atacama Desert, at Box canyon in Idaho, valleys around Kohala on Hawaii and Apalachicola bluffs in Florida to test the applicability of our methods to real-world systems. In the seeping groundwater valleys, valleys develop due to a combination of mass-wasting failures, mudflows and fluvial flow. The latter two processes are expressed in the final morphology by a break in slope. The mass wasting processes result in U-shaped valleys, which are more pronounced in distal groundwater cases. However, in real-world cases of similar shaped valleys, the cross-sectional shape seems strongly influenced by the strength of the material as well. Groundwater flow piracy of multiple valleys within one system are characterized by equal ratios of width and length development, a property that is absent in case of a local groundwater source which does not induce flow piracy. In case of pressurized groundwater release, the sediment surface in the source area fractured and pits developed due to high groundwater pressure. The resulting valley head consisted of feather-shaped converging flow features. Scaling of the non-fluvial features that relate to groundwater pressure is possible by using hydrological modelling of groundwater pressure and geophysical modelling of the behaviour of the material under such pressures. Our results on sapping valley formation, combined with insights from multiple terrestrial sites of similar valleys contribute to the discussion of some enigmatic valleys on Mars. We provide several quantitative morphological measures, which directly relate to the formative process, which is valuable in linking morphology to the formative process. Our results on pressurized groundwater release prove a long-standing hypothesis on the formation on some of the largest valleys observed in our solar system. In both cases, the insights in the formative processes enable us to quantify the amount of water required for the formation of groundwater-induced Martian valleys.

Shatter cones - An outstanding problem in shock mechanics. [geological impact fracture surface in cratering

NASA Technical Reports Server (NTRS)

Milton, D. J.

1977-01-01

Shatter cone characteristics are surveyed. Shatter cones, a form of rock fracture in impact structures, apparently form as a shock front interacts with inhomogeneities or discontinuities in the rock. Topics discussed include morphology, conditions of formation, shock pressure of formation, and theories of formation. It is thought that shatter cones are produced within a limited range of shock pressures extending from about 20 to perhaps 250 kbar. Apical angles range from less than 70 deg to over 120 deg. Tentative hypotheses concerning the physical process of shock coning are considered. The range in shock pressures which produce shatter cones might correspond to the range in which shock waves decompose into elastic and deformational fronts.

Formation of model polar stratospheric cloud films

NASA Technical Reports Server (NTRS)

Middlebrook, Ann M.; Koehler, Birgit G.; Mcneill, Laurie S.; Tolbert, Margaret A.

1992-01-01

Fourier transform infrared spectroscopy was used to examine the competitive growth of films representative of polar stratospheric clouds. These experiments show that either crystalline nitric acid trihydrate (beta-NAT) or amorphous films with H2O:HNO3 ratios close to 3:1 formed at temperatures 3-7 K warmer than the ice frost point under stratospheric pressure conditions. In addition, with higher HNO3 pressure, we observed nitric acid dihydrate (NAD) formation at temperatures warmer than ice formation. However, our experiments also show that NAD surfaces converted to beta-NAT upon exposure to stratospheric water pressures. Finally, we determined that the net uptake coefficient for HNO3 on beta-NAT is close to unity, whereas the net uptake coefficient for H2O is much less.

Physicochemical properties of natural actomyosin from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure.

PubMed

Zhou, Aimei; Lin, Liying; Liang, Yan; Benjakul, Soottawat; Shi, Xiaoling; Liu, Xin

2014-08-01

Changes of physicochemical properties in natural actomyosin (NAM) from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure (200, 400, 600MPa for 10, 30, 50min) were studied. The increase in turbidity of NAM was coincidental with the decrease in protein solubility with increasing pressure and time, suggesting the formation of protein aggregates. SDS-PAGE showed that polymerisation and degradation of myosin heavy chain were induced by high pressure. Ca(2+)-ATPase activity of NAM treated by high pressure was lost, suggesting the denaturation of myosin and the dissociation of actomyosin complex. Surface hydrophobicity of NAM increased when the pressure and pressurization time increased, indicating that the exposed hydrophobic residues increased upon application of high pressure. Decrease in total sulfhydryl content and increase in surface-reactive sulfhydryl content of NAM samples were observed with the extension of pressurizing time, indicating the formation of disulphide bonds through oxidation of SH groups or disulphide interchanges. The above changes of physicochemical properties suggested conformational changes of NAM from muscle of threadfin bream induced by high hydrostatic pressure. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synoptic patterns leading to hailstorm in Chaharmahal and Bakhtiari province, Iran

NASA Astrophysics Data System (ADS)

Salahi, Bromand; Nohegar, Ahmad; Behrouzi, Mahmoud; Aalijahan, Mehdi

2018-03-01

The purpose of this study was to extract the synoptic patterns of 500 mb geopotential height and the sea level pressure leading to form hail in Chaharmahal and Bakhtiari province, Iran. To this end, at first, we explored hail occurrence in different areas of the province under investigation. Then, using sea level pressure and 500 mb geopotential height data, the patterns of hail occurrence were investigated through hierarchical clustering and Ward's method. The level of 500 mb patterns resulting in hail formation in the area include: (1) settlement of a cut-off low pressure blocking in Turkey and Iran's position in downstream of trough and injection of humidity coming from the Red Sea; (2) settlement of low ridge in northern Europe and Iran lying in downstream of the trough and injection of humidity of the Mediterranean Sea; (3) settlement of a cut-off low pressure in east of Europe and Iran lying in downstream of the trough; and (4) settlement of a deep trough in the Mediterranean Sea, formation of an omega-shaped blocking in Northern Europe and Iran lying in downstream of the trough. At sea level, the following patterns have caused hail formation in Chaharmahal and Bakhtiari province: (1) settlement of low pressure in Iran and Russia accompanying high pressure in Taklimakan Desert and east of Europe; (2) settlement of low pressure in Iran and high pressure in Egypt, northern Europe, and Taklimakan Desert; and (3) settlement of low pressure in Iran, Saudi Arabia and south of Italy and high pressure in Egypt and Siberia.

Effects of varying pulsatile lavage pressure on cancellous bone structure and fracture healing.

PubMed

Polzin, Britton; Ellis, Thomas; Dirschl, Douglas R

2006-04-01

To study the effects of variations in pulsatile lavage irrigation pressure on the rate of new bone formation and the degree to which cellular elements are removed from cancellous bone after fracture. A previously described intraarticular fracture model was used for 29 New Zealand white rabbits that underwent osteotomy of the medial femoral condyle. Fractures were irrigated with high-pressure pulsatile lavage at a fixed distance and volume, but at nozzle pressures varying from 20 to 70 psi. Fractures were reduced and stabilized, and animals euthanized 14 days after fracture. Fluorescent bone staining was used to determine the rate of new bone formation in the osteotomy site. At the time of euthanasia, the nonoperated knees of 12 rabbits underwent osteotomy and irrigation using the same protocol. These specimens were sent for immediate scanning electron microscopy to determine the amount of cellular material removed from the bony trabeculae. In the first week after irrigation, there was no significant difference in the amount of new bone formation between the 20- and 30-psi groups, but there were significant differences between these groups and the 50- and 70-psi groups. There were no significant differences between any of the groups in the amount of new bone formed during the second week after irrigation. No structural damage to the bony trabeculae was observed in any specimen irrigated at any of the pressures used. There was a direct correlation between percentage of the trabecula completely cleared of cellular material and irrigation pressure; there were statistically significant differences between each of the groups. There are presently no recommended guidelines as to the optimal irrigation pressure, and this study is the first to address the effects of variations in pressure on bone healing. The results of this study indicate that early new bone formation in an intraarticular fracture rabbit model is inhibited by irrigation pressure of 50 psi or greater. Additionally, this study demonstrates a direct relationship between irrigation pressure and the amount of cellular material removed from the trabecula at the irrigation site. Surgeons should be aware of the potentially detrimental effects of using irrigation pressures at or above 50 psi in the treatment of fractures.

Portable device and method for determining permeability characteristics of earth formations

DOEpatents

Shuck, Lowell Z.

1977-01-01

The invention is directed to a device which is used for determining permeability characteristics of earth formations at the surface thereof. The determination of the maximum permeability direction and the magnitude of permeability are achieved by employing a device comprising a housing having a central fluid-injection port surrounded by a plurality of spaced-apart fluid flow and pressure monitoring ports radially extending from the central injection port. With the housing resting on the earth formation in a relatively fluid-tight manner as provided by an elastomeric pad disposed therebetween, fluid is injected through the central port into the earth formation and into registry with the fluid-monitoring ports disposed about the injection port. The fluid-monitoring ports are selectively opened and the flow of the fluid through the various fluid ports is measured so as to provide a measurement of flow rates and pressure distribution about the center hole which is indicative on the earth formation permeability direction and magnitude. For example, the azimuthal direction of the fluid-monitoring ports in the direction through which the greatest amount of injected fluid flows as determined by the lowest pressure distribution corresponds to the direction of maximum permeability in the earth formation.

Brine migration resulting from pressure increases in a layered subsurface system

NASA Astrophysics Data System (ADS)

Delfs, Jens-Olaf; Nordbeck, Johannes; Bauer, Sebastian

2016-04-01

Brine originating from the deep subsurface impairs parts of the freshwater resources in the North German Basin. Some of the deep porous formations (esp. Trias and Jurassic) exhibit considerable storage capacities for waste fluids (CO2, brine from oil production or cavern leaching), raising concerns among water providers that this type of deep subsurface utilization might impair drinking water supplies. On the one hand, overpressures induced by fluid injections and the geothermal gradient support brine migration from deep into shallow formations. On the other hand, the rising brine is denser than the surrounding less-saline formation waters and, therefore, tends to settle down. Aim of this work is to investigate the conditions under which pressurized formation brine from deep formations can reach shallow freshwater resources. Especially, the role of intermediate porous formations between the storage formation and the groundwater is studied. For this, complex thermohaline simulations using a coupled numerical process model are necessary and performed in this study, in which fluid density depends on fluid pressure, temperature and salt content and the governing partial differential equations are coupled. The model setup is 2D and contains a hypothetic series of aquifers and barriers, each with a thickness of 200 m. Formation pressure is increased at depths of about 2000 m in proximity to a salt wall and a permeable fault. The domain size reaches up to tens of kilometers horizontally to the salt wall. The fault connects the injection formation and the freshwater aquifer such that conditions can be considered as extremely favorable for induced brine migration (worst case scenarios). Brine, heat, and salt fluxes are quantified with reference to hydraulic permeabilities, storage capacities (in terms of domain size), initial salt and heat distribution, and operation pressures. The simulations reveal the development of a stagnation point in the fault region in each intermediate aquifer above the injection formation, where brine settles down and flows from the fault zone into the aquifer. This effect changes buoyancy so that lower density brine from the upper aquifers can rise higher and at larger fluxes compared to the case when no intermediary aquifers are present. In general, uplift of brine originating from the intermediary aquifers is mainly restricted to the next overlying two to three permeable aquifers (200m-1000m) or even only to the next aquifer if injection pressures are lower than about 10 bar. If injection induced over-pressures are high, brine from the injection reservoir can dominate inflow into the freshwater reservoir at late times (tens of years). An extensive parameter variation shows the effects of individual parameters. It is found, e.g., that no brine enters the freshwater aquifer if fault permeability is lower than about 10-14 m2. Acknowledgments: This work is part of the ANGUS+ project (www.angusplus.de) and funded by the German Federal Ministry of Education and Research (BMBF) as part of the energy storage initiative "Energiespeicher".

Vortex rope instabilities in a model of conical draft tube

NASA Astrophysics Data System (ADS)

Skripkin, Sergey; Tsoy, Mikhail; Kuibin, Pavel; Shtork, Sergey

2017-10-01

We report on experimental studies of the formation of vortex ropes in a laboratory simplified model of hydroturbine draft tube. Work is focused on the observation of various flow patterns at the different rotational speed of turbine runner at fixed flow rate. The measurements involve high-speed visualization and pressure pulsations recordings. Draft tube wall pressure pulsations are registered by pressure transducer for different flow regimes. Vortex rope precession frequency were calculated using FFT transform. The experiments showed interesting features of precessing vortex rope like twin spiral and formation of vortex ring.

The granin VGF promotes genesis of secretory vesicles, and regulates circulating catecholamine levels and blood pressure

PubMed Central

Fargali, Samira; Garcia, Angelo L.; Sadahiro, Masato; Jiang, Cheng; Janssen, William G.; Lin, Wei-Jye; Cogliani, Valeria; Elste, Alice; Mortillo, Steven; Cero, Cheryl; Veitenheimer, Britta; Graiani, Gallia; Pasinetti, Giulio M.; Mahata, Sushil K.; Osborn, John W.; Huntley, George W.; Phillips, Greg R.; Benson, Deanna L.; Bartolomucci, Alessandro; Salton, Stephen R.

2014-01-01

Secretion of proteins and neurotransmitters from large dense core vesicles (LDCVs) is a highly regulated process. Adrenal LDCV formation involves the granin proteins chromogranin A (CgA) and chromogranin B (CgB); CgA- and CgB-derived peptides regulate catecholamine levels and blood pressure. We investigated function of the granin VGF (nonacronymic) in LDCV formation and the regulation of catecholamine levels and blood pressure. Expression of exogenous VGF in nonendocrine NIH 3T3 fibroblasts resulted in the formation of LDCV-like structures and depolarization-induced VGF secretion. Analysis of germline VGF-knockout mouse adrenal medulla revealed decreased LDCV size in noradrenergic chromaffin cells, increased adrenal norepinephrine and epinephrine content and circulating plasma epinephrine, and decreased adrenal CgB. These neurochemical changes in VGF-knockout mice were associated with hypertension. Germline knock-in of human VGF1–615 into the mouse Vgf locus rescued the hypertensive knockout phenotype, while knock-in of a truncated human VGF1–524 that lacks several C-terminal peptides, including TLQP-21, resulted in a small but significant increase in systolic blood pressure compared to hVGF1–615 mice. Finally, acute and chronic administration of the VGF-derived peptide TLQP-21 to rodents decreased blood pressure. Our studies establish a role for VGF in adrenal LDCV formation and the regulation of catecholamine levels and blood pressure.—Fargali, S., Garcia, A. L., Sadahiro, M., Jiang, C., Janssen, W. G., Lin, W.-J., Cogliani, V., Elste, A., Mortillo, S., Cero, C., Veitenheimer, B., Graiani, G., Pasinetti, G. M., Mahata, S. K., Osborn, J. W., Huntley, G. W., Phillips, G. R., Benson, D. L., Bartolomucci, A., Salton, S. R. The granin VGF promotes genesis of secretory vesicles, and regulates circulating catecholamine levels and blood pressure. PMID:24497580

Current sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-Frequency Assisted Discharge

NASA Technical Reports Server (NTRS)

Hallock, Ashley K.; Choueiri, Edgar Y.; Polzin, Kurt A.

2007-01-01

The inductive formation of current sheets in a conical theta pinch FARAD (Faraday Accelerator with Radio-frequency Assisted Discharge) thruster is investigated experimentally with time-integrated photography. The goal is to help in understanding the mechanisms and conditions controlling the strength and extent of the current sheet, which are two indices important for FARAD as a propulsion concept. The profiles of these two indices along the inside walls of the conical acceleration coil are assumed to be related to the profiles of the strength and extent of the luminosity pattern derived from photographs of the discharge. The variations of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all parameters held constant) provided the first clues on the nature and qualitative dependencies of current sheet formation. It was found that there is an optimal pressure for which both indices reach a maximum and that the rate of change in these indices with pressure differs on either side of this optimal pressure. This allowed the inference that current sheet formation follows a Townsend-like breakdown mechanism modified by the existence of a finite pressure-dependent radio-frequency-generated electron density background. The observation that the effective location of the luminosity pattern favors the exit-half of the conical coil is explained as the result of the tendency of the inductive discharge circuit to operate near its minimal self-inductance. Movement of the peak in the luminosity pattern towards the upstream side of the cone with increasing pressure is believed to result from the need of the circuit to compensate for the increase in background plasma resistivity due to increasing pressure.

Effect of Processing Pressure on Isolated Pore Formation during Controlled Directional Solidification in Small Channels

NASA Technical Reports Server (NTRS)

Cox, Matthew C.; Anilkumar, Amrutur V.; Grugel, RIchard N.; Lee, Chun P.

2008-01-01

Directional solidification experiments were performed, using succinonitrile saturated with nitrogen gas, to examine the effects of in-situ processing pressure changes on the formation growth, and evolution of an isolated, cylindrical gaseous pore. A novel solidification facility, capable of processing thin cylindrical samples (I.D. < 1.0 mm), under controlled pressure conditions, was used for the experiments. A new experimental method for growing the isolated pore from a seed bubble is introduced. The experimental results indicate that an in-situ processing pressure change will result in either a transient change in pore diameter or a complete termination of pore growth, indicating that pressure changes can be used as a control parameter to terminate bubble growth. A simple analytical model has been introduced to explain the experimental observations.

Chondrocyte burst promotes space for mineral expansion.

PubMed

Hara, Emilio Satoshi; Okada, Masahiro; Nagaoka, Noriyuki; Hattori, Takako; Iida, Letycia Mary; Kuboki, Takuo; Nakano, Takayoshi; Matsumoto, Takuya

2018-01-22

Analysis of tissue development from multidisciplinary approaches can result in more integrative biological findings, and can eventually allow the development of more effective bioengineering methods. In this study, we analyzed the initial steps of mineral formation during secondary ossification of mouse femur based on biological and bioengineering approaches. We first found that some chondrocytes burst near the mineralized area. External factors that could trigger chondrocyte burst were then investigated. Chondrocyte burst was shown to be modulated by mechanical and osmotic pressure. A hypotonic solution, as well as mechanical stress, significantly induced chondrocyte burst. We further hypothesized that chondrocyte burst could be associated with space-making for mineral expansion. In fact, ex vivo culture of femur epiphysis in hypotonic conditions, or under mechanical pressure, enhanced mineral formation, compared to normal culture conditions. Additionally, the effect of mechanical pressure on bone formation in vivo was investigated by immobilization of mouse lower limbs to decrease the body pressure onto the joints. The results showed that limb immobilization suppressed bone formation. Together, these results suggest chondrocyte burst as a novel fate of chondrocytes, and that manipulation of chondrocyte burst with external mechano-chemical stimuli could be an additional approach for cartilage and bone tissue engineering.

Abnormal formation velocities and applications to pore pressure prediction

NASA Astrophysics Data System (ADS)

Liu, Libin; Shen, Guoqiang; Wang, Zhentao; Yang, Hongwei; Han, Hongwei; Cheng, Yuanfeng

2018-06-01

The pore pressure is a vital concept to the petroleum industry and cannot be ignored by either reservoir engineers or geoscientists. Based on theoretical analyses of effective stresses and the grain packing model, a new equation is proposed for predicting pore pressures from formation velocity data. The predictions agree well with both measured pressures and estimations using Eaton's empirical equation, but the application of the new equation to seismic data is simple and convenient. One application example shows that the identification of sweet spots is much easier using pore pressure data than with inverted seismic velocity data. In another application example using field seismic data, a distribution of overpressured strata is revealed, which is a crucial clue for petroleum generation and accumulation. Still, the accuracy of pore pressure prediction is hardly always guaranteed, mainly owing to the complexity of the real geology and the suitability of specific assumptions about the underlying rock physics.

The formation of chondrules at high gas pressures in the solar nebula.

PubMed

Galy, A; Young, E D; Ash, R D; O'Nions, R K

2000-12-01

High-precision magnesium isotope measurements of whole chondrules from the Allende carbonaceous chondrite meteorite show that some aluminum-rich Allende chondrules formed at or near the time of formation of calcium-aluminum-rich inclusions and that some others formed later and incorporated precursors previously enriched in magnesium-26. Chondrule magnesium-25/magnesium-24 correlates with [magnesium]/[aluminum] and size, the aluminum-rich, smaller chondrules being the most enriched in the heavy isotopes of magnesium. These relations imply that high gas pressures prevailed during chondrule formation in the solar nebula.

Low Temperature Kinetics of the First Steps of Water Cluster Formation

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

Bourgalais, J.; Roussel, V.; Capron, M.

2016-03-01

We present a combined experimental and theoretical low temperature kinetic study of water cluster formation. Water cluster growth takes place in low temperature (23-69 K) supersonic flows. The observed kinetics of formation of water clusters are reproduced with a kinetic model based on theoretical predictions for the first steps of clusterization. The temperature-and pressure-dependent association and dissociation rate coefficients are predicted with an ab initio transition state theory based master equation approach over a wide range of temperatures (20-100 K) and pressures (10(-6) - 10 bar).

The low salinity effect at high temperatures

DOE PAGES

Xie, Quan; Brady, Patrick V.; Pooryousefy, Ehsan; ...

2017-04-05

The mechanism(s) of low salinity water flooding (LSWF) must be better understood at high temperatures and pressures if the method is to be applied in high T/P kaolinite-bearing sandstone reservoirs. We measured contact angles between a sandstone and an oil (acid number, AN = 3.98 mg KOH/g, base number, BN = 1.3 mg KOH/g) from a reservoir in the Tarim Field in western China in the presence of various water chemistries. We examined the effect of aqueous ionic solutions (formation brine, 100X diluted formation brine, and softened water), temperature (60, 100 and 140 °C) and pressure (20, 30, 40, andmore » 50 MPa) on the contact angle. We also measured the zeta potential of the oil/water and water/rock interfaces to calculate oil/brine/rock disjoining pressures. A surface complexation model was developed to interpret contact angle measurements and compared with DLVO theory predictions. Contact angles were greatest in formation water, followed by the softened water, and low salinity water at the same pressure and temperature. Contact angles increased slightly with temperature, whereas pressure had little effect. DLVO and surface complexation modelling predicted similar wettability trends and allow reasonably accurate interpretation of core-flood results. Water chemistry has a much larger impact on LSWF than reservoir temperature and pressure. As a result, low salinity water flooding should work in high temperature and high pressure kaolinite-bearing sandstone reservoirs.« less

The low salinity effect at high temperatures

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

Xie, Quan; Brady, Patrick V.; Pooryousefy, Ehsan

The mechanism(s) of low salinity water flooding (LSWF) must be better understood at high temperatures and pressures if the method is to be applied in high T/P kaolinite-bearing sandstone reservoirs. We measured contact angles between a sandstone and an oil (acid number, AN = 3.98 mg KOH/g, base number, BN = 1.3 mg KOH/g) from a reservoir in the Tarim Field in western China in the presence of various water chemistries. We examined the effect of aqueous ionic solutions (formation brine, 100X diluted formation brine, and softened water), temperature (60, 100 and 140 °C) and pressure (20, 30, 40, andmore » 50 MPa) on the contact angle. We also measured the zeta potential of the oil/water and water/rock interfaces to calculate oil/brine/rock disjoining pressures. A surface complexation model was developed to interpret contact angle measurements and compared with DLVO theory predictions. Contact angles were greatest in formation water, followed by the softened water, and low salinity water at the same pressure and temperature. Contact angles increased slightly with temperature, whereas pressure had little effect. DLVO and surface complexation modelling predicted similar wettability trends and allow reasonably accurate interpretation of core-flood results. Water chemistry has a much larger impact on LSWF than reservoir temperature and pressure. As a result, low salinity water flooding should work in high temperature and high pressure kaolinite-bearing sandstone reservoirs.« less

Multivariate Formation Pressure Prediction with Seismic-derived Petrophysical Properties from Prestack AVO inversion and Poststack Seismic Motion Inversion

NASA Astrophysics Data System (ADS)

Yu, H.; Gu, H.

2017-12-01

A novel multivariate seismic formation pressure prediction methodology is presented, which incorporates high-resolution seismic velocity data from prestack AVO inversion, and petrophysical data (porosity and shale volume) derived from poststack seismic motion inversion. In contrast to traditional seismic formation prediction methods, the proposed methodology is based on a multivariate pressure prediction model and utilizes a trace-by-trace multivariate regression analysis on seismic-derived petrophysical properties to calibrate model parameters in order to make accurate predictions with higher resolution in both vertical and lateral directions. With prestack time migration velocity as initial velocity model, an AVO inversion was first applied to prestack dataset to obtain high-resolution seismic velocity with higher frequency that is to be used as the velocity input for seismic pressure prediction, and the density dataset to calculate accurate Overburden Pressure (OBP). Seismic Motion Inversion (SMI) is an inversion technique based on Markov Chain Monte Carlo simulation. Both structural variability and similarity of seismic waveform are used to incorporate well log data to characterize the variability of the property to be obtained. In this research, porosity and shale volume are first interpreted on well logs, and then combined with poststack seismic data using SMI to build porosity and shale volume datasets for seismic pressure prediction. A multivariate effective stress model is used to convert velocity, porosity and shale volume datasets to effective stress. After a thorough study of the regional stratigraphic and sedimentary characteristics, a regional normally compacted interval model is built, and then the coefficients in the multivariate prediction model are determined in a trace-by-trace multivariate regression analysis on the petrophysical data. The coefficients are used to convert velocity, porosity and shale volume datasets to effective stress and then to calculate formation pressure with OBP. Application of the proposed methodology to a research area in East China Sea has proved that the method can bridge the gap between seismic and well log pressure prediction and give predicted pressure values close to pressure meassurements from well testing.

The Maximum Flux of Star-Forming Galaxies

NASA Astrophysics Data System (ADS)

Crocker, Roland M.; Krumholz, Mark R.; Thompson, Todd A.; Clutterbuck, Julie

2018-04-01

The importance of radiation pressure feedback in galaxy formation has been extensively debated over the last decade. The regime of greatest uncertainty is in the most actively star-forming galaxies, where large dust columns can potentially produce a dust-reprocessed infrared radiation field with enough pressure to drive turbulence or eject material. Here we derive the conditions under which a self-gravitating, mixed gas-star disc can remain hydrostatic despite trapped radiation pressure. Consistently taking into account the self-gravity of the medium, the star- and dust-to-gas ratios, and the effects of turbulent motions not driven by radiation, we show that galaxies can achieve a maximum Eddington-limited star formation rate per unit area \\dot{Σ }_*,crit ˜ 10^3 M_{⊙} pc-2 Myr-1, corresponding to a critical flux of F*, crit ˜ 1013L⊙ kpc-2 similar to previous estimates; higher fluxes eject mass in bulk, halting further star formation. Conversely, we show that in galaxies below this limit, our one-dimensional models imply simple vertical hydrostatic equilibrium and that radiation pressure is ineffective at driving turbulence or ejecting matter. Because the vast majority of star-forming galaxies lie below the maximum limit for typical dust-to-gas ratios, we conclude that infrared radiation pressure is likely unimportant for all but the most extreme systems on galaxy-wide scales. Thus, while radiation pressure does not explain the Kennicutt-Schmidt relation, it does impose an upper truncation on it. Our predicted truncation is in good agreement with the highest observed gas and star formation rate surface densities found both locally and at high redshift.

The maximum flux of star-forming galaxies

NASA Astrophysics Data System (ADS)

Crocker, Roland M.; Krumholz, Mark R.; Thompson, Todd A.; Clutterbuck, Julie

2018-07-01

The importance of radiation pressure feedback in galaxy formation has been extensively debated over the last decade. The regime of greatest uncertainty is in the most actively star-forming galaxies, where large dust columns can potentially produce a dust-reprocessed infrared radiation field with enough pressure to drive turbulence or eject material. Here, we derive the conditions under which a self-gravitating mixed gas-star disc can remain hydrostatic despite trapped radiation pressure. Consistently, taking into account the self-gravity of the medium, the star- and dust-to-gas ratios, and the effects of turbulent motions not driven by radiation, we show that galaxies can achieve a maximum Eddington-limited star formation rate per unit area \\dot{Σ }_*,crit ˜ 10^3 M_{⊙} pc-2 Myr-1, corresponding to a critical flux of F*,crit ˜ 1013 L⊙ kpc-2 similar to previous estimates; higher fluxes eject mass in bulk, halting further star formation. Conversely, we show that in galaxies below this limit, our 1D models imply simple vertical hydrostatic equilibrium and that radiation pressure is ineffective at driving turbulence or ejecting matter. Because the vast majority of star-forming galaxies lie below the maximum limit for typical dust-to-gas ratios, we conclude that infrared radiation pressure is likely unimportant for all but the most extreme systems on galaxy-wide scales. Thus, while radiation pressure does not explain the Kennicutt-Schmidt relation, it does impose an upper truncation on it. Our predicted truncation is in good agreement with the highest observed gas and star formation rate surface densities found both locally and at high redshift.

Rapid gas hydrate formation processes: Will they work?

DOE PAGES

Brown, Thomas D.; Taylor, Charles E.; Bernardo, Mark P.

2010-06-07

Researchers at DOE’s National Energy Technology Laboratory (NETL) have been investigating the formation of synthetic gas hydrates, with an emphasis on rapid and continuous hydrate formation techniques. The investigations focused on unconventional methods to reduce dissolution, induction, nucleation and crystallization times associated with natural and synthetic hydrates studies conducted in the laboratory. Numerous experiments were conducted with various high-pressure cells equipped with instrumentation to study rapid and continuous hydrate formation. The cells ranged in size from 100 mL for screening studies to proof-of-concept studies with NETL’s 15-Liter Hydrate Cell. The results from this work demonstrate that the rapid and continuousmore » formation of methane hydrate is possible at predetermined temperatures and pressures within the stability zone of a Methane Hydrate Stability Curve.« less

Spectral shifting strongly constrains molecular cloud disruption by radiation pressure on dust

NASA Astrophysics Data System (ADS)

Reissl, Stefan; Klessen, Ralf S.; Mac Low, Mordecai-Mark; Pellegrini, Eric W.

2018-03-01

Aim. We aim to test the hypothesis that radiation pressure from young star clusters acting on dust is the dominant feedback agent disrupting the largest star-forming molecular clouds and thus regulating the star-formation process. Methods: We performed multi-frequency, 3D, radiative transfer calculations including both scattering and absorption and re-emission to longer wavelengths for model clouds with masses of 104-107 M⊙, containing embedded clusters with star formation efficiencies of 0.009-91%, and varying maximum grain sizes up to 200 μm. We calculated the ratio between radiative and gravitational forces to determine whether radiation pressure can disrupt clouds. Results: We find that radiation pressure acting on dust almost never disrupts star-forming clouds. Ultraviolet and optical photons from young stars to which the cloud is optically thick do not scatter much. Instead, they quickly get absorbed and re-emitted by the dust at thermal wavelengths. As the cloud is typically optically thin to far-infrared radiation, it promptly escapes, depositing little momentum in the cloud. The resulting spectrum is more narrowly peaked than the corresponding Planck function, and exhibits an extended tail at longer wavelengths. As the opacity drops significantly across the sub-mm and mm wavelength regime, the resulting radiative force is even smaller than for the corresponding single-temperature blackbody. We find that the force from radiation pressure falls below the strength of gravitational attraction by an order of magnitude or more for either Milky Way or moderate starbust conditions. Only for unrealistically large maximum grain sizes, and star formation efficiencies far exceeding 50% do we find that the strength of radiation pressure can exceed gravity. Conclusions: We conclude that radiation pressure acting on dust does not disrupt star-forming molecular clouds in any Local Group galaxies. Radiation pressure thus appears unlikely to regulate the star-formation process on either local or global scales.

Determining the Area of Review for Industrial Waste Disposal Wells.

DTIC Science & Technology

1981-12-01

pressure increases sufficiently to force formation fluids and/or injected wastes up abandoned well bores to contaminate underground sources of drinking...Drilling Mud Circulating System . . 72 9. Increase in Gel Strength of Various Mud Types With Time . . . . . . . . . . . . . . . . . . 96 10. Gel... increased fluid pressure in a disposal zone which results from a waste injection operation may force injected and/or formation fluid to migrate up an

Pressure broadening of the ((dt. mu. )dee)/sup */ formation resonances

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

Cohen, J.S.; Leon, M.; Padial, N.T.

1988-01-01

The treatment of ((dt..mu..)dee)/sup */ formation at high densities as a pressure broadening process is discussed. The quasistatic approximation is shown to satisfy the usual conditions of muon-catalyzed fusion better than does the impact approximation. Complete accurate results are shown for the impact approximation, and a preliminary rough treatment is presented to illustrate the quasistatic approximation. 13 refs., 8 figs.

Spacecraft Maneuvering at the Sun/Earth-Moon L2 Libration Point

NASA Astrophysics Data System (ADS)

Shahid, Kamran

Spacecraft formation flying in the vicinity of the Sun/Earth-Moon libration points offers many promising possibilities for space exploration. The concept of formation flying involves the distribution of the functionality of a single spacecraft among several smaller, cooperative spacecraft. The libration points are locations relative to two large orbiting bodies where a third body with relatively small mass can remain stationary relative to the two larger bodies. The most significant perturbation experienced by a spacecraft at the libration point is effect of solar radiation pressure. This thesis presents the development of nonlinear control techniques for maneuvering control at the Sun-Earth/Moon L2 libration point. A new thruster based formation control technique is presented. We also consider a leader/follower formation architecture, and examine the station keeping control of the leader spacecraft and the formation control of the follower spacecraft using solar radiation pressure. Reference trajectories of the leader spacecraft, halo and Lissajous orbits, are determined using a numerical technique in order to take into account all major gravitational perturbations. The nonlinear controllers are developed based on Lyapunov analysis, including non-adaptive and adaptive designs. Thruster based and solar radiation pressure based control laws for spacecraft maneuvering at the Sun-Earth/Moon libration point are developed. Higher order sliding mode control is utilized to address the non-affine structure of the solar sail control inputs. The reduced input solar radiation pressure problem is properly addressed as an underactuated control problem. The development of adaptive control for solar sail equipped spacecraft is an innovation and represents and advancement in solar sailing control technology. Controller performance is evaluated in a high fidelity ephemeris model to reflect a realistic simulated space environment. The numerical results demonstrate the effectiveness of the proposed control techniques for spacecraft maneuvering using solar radiation pressure at the L2 libration point. Stationkeeping accuracies of 50m and formation maintenance accuracies of less than 1m are possible using solar radiation pressure at a sub-L2 libration point. The benefits of these control techniques include increasing libration point mission lifetimes and doubling payload mass fractions as compared to conventional propulsion methods.

Localized fluid discharge in subduction zones: Insights from tension veins around an ancient megasplay fault (Nobeoka Thrust, SW Japan)

NASA Astrophysics Data System (ADS)

Otsubo, M.; Hardebeck, J.; Miyakawa, A.; Yamaguchi, A.; Kimura, G.

2017-12-01

Fluid-rock interactions along seismogenic faults are of great importance to understand fault mechanics. The fluid loss by the formation of mode I cracks (tension cracks) increases the fault strength and creates drainage asperities along the plate interface (Sibson, 2013, Tectonophysics). The Nobeoka Thrust, in southwestern Japan, is an on-land example of an ancient megasplay fault and provides an excellent record of deformation and fluid flow at seismogenic depths of a subduction zone (Kondo et al., 2005, Tectonics). We focus on (1) Pore fluid pressure loss, (2) Amount of fault strength recovery, and (3) Fluid circulation by the formation of mode I cracks in the post-seismic period around the fault zone of the Nobeoka Thrust. Many quartz veins that filled mode I crack at the coastal outcrops suggest a normal faulting stress regime after faulting of the Nobeoka Thrust (Otsubo et al., 2016, Island Arc). We estimated the decrease of the pore fluid pressure by the formation of the mode I cracks around the Nobeoka Thrust in the post-seismic period. When the pore fluid pressure exceeds σ3, veins filling mode I cracks are constructed (Jolly and Sanderson, 1997, Jour. Struct. Geol.). We call the pore fluid pressure that exceeds σ3 "pore fluid over pressure". The differential stress in the post-seismic period and the driving pore fluid pressure ratio P* (P* = (Pf - σ3) / (σ1 - σ3), Pf: pore fluid pressure) are parameters to estimate the pore fluid over pressure. In the case of the Nobeoka Thrust (P* = 0.4, Otsubo et al., 2016, Island Arc), the pore fluid over pressure is up to 20 MPa (assuming tensile strength = 10 MPa). 20 MPa is equivalent to <10% of the total pore fluid pressure around the Nobeoka Thrust (depth = 10 km, density = 2.7 kg/m3). When the pore fluid pressure decreases by 4%, the normalized pore pressure ratio λ* (λ* = (Pf - Ph) / (Pl - Ph), Pl: lithostatic pressure; Ph: hydrostatic pressure) changes from 0.95 to 0.86. In the case of the Nobeoka Thrust, the fault strength can increase by up to 10 MPa (assuming frictional coefficient = 0.6). 10 MPa is almost equivalent to the stress drop values in large trench type earthquakes. Hence, we suggest that the fluid loss caused by the formation of mode I cracks in the post-seismic period may play an important role by increasing frictional strength along the megasplay fault.

Detecting overpressure using the Eaton and Equivalent Depth methods in Offshore Nova Scotia, Canada

NASA Astrophysics Data System (ADS)

Ernanda; Primasty, A. Q. T.; Akbar, K. A.

2018-03-01

Overpressure is an abnormal high subsurface pressure of any fluids which exceeds the hydrostatic pressure of column of water or formation brine. In Offshore Nova Scotia Canada, the values and depth of overpressure zone are determined using the eaton and equivalent depth method, based on well data and the normal compaction trend analysis. Since equivalent depth method is using effective vertical stress principle and Eaton method considers physical property ratio (velocity). In this research, pressure evaluation only applicable on Penobscot L-30 well. An abnormal pressure is detected at depth 11804 feet as possibly overpressure zone, based on pressure gradient curve and calculation between the Eaton method (7241.3 psi) and Equivalent Depth method (6619.4 psi). Shales within Abenaki formation especially Baccaro Member is estimated as possible overpressure zone due to hydrocarbon generation mechanism.

Under pressure: progressively enlarging facial mass following high-pressure paint injection injury.

PubMed

Mushtaq, Jameel; Walker, Abigail; Hunter, Ben

2016-01-19

High-pressure paint injection injuries are relatively rare industrial accidents and almost exclusively occur on the non-dominant hand. A rarely documented complication of these injuries is the formation of a foreign body granuloma. We report a case of a 33-year-old man presenting with extensive facial scarring and progressive right paranasal swelling 7 years after a high-pressure paint injury. After imaging investigations, an excision of the mass and revision of scarring was performed. Access to the mass was gained indirectly through existing scarring over the nose to ensure an aesthetic result. Histological analysis revealed a florid granulomatous foreign body reaction to retained paint. To the best of our knowledge, this is the first reported case of a facial high-pressure paint injury with consequent formation of a foreign body granuloma. 2016 BMJ Publishing Group Ltd.

Does Pressure Accentuate General Relativistic Gravitational Collapse and Formation of Trapped Surfaces?

NASA Astrophysics Data System (ADS)

Mitra, Abhas

2013-04-01

It is widely believed that though pressure resists gravitational collapse in Newtonian gravity, it aids the same in general relativity (GR) so that GR collapse should eventually be similar to the monotonous free fall case. But we show that, even in the context of radiationless adiabatic collapse of a perfect fluid, pressure tends to resist GR collapse in a manner which is more pronounced than the corresponding Newtonian case and formation of trapped surfaces is inhibited. In fact there are many works which show such collapse to rebound or become oscillatory implying a tug of war between attractive gravity and repulsive pressure gradient. Furthermore, for an imperfect fluid, the resistive effect of pressure could be significant due to likely dramatic increase of tangential pressure beyond the "photon sphere." Indeed, with inclusion of tangential pressure, in principle, there can be static objects with surface gravitational redshift z → ∞. Therefore, pressure can certainly oppose gravitational contraction in GR in a significant manner in contradiction to the idea of Roger Penrose that GR continued collapse must be unstoppable.

Phase diagram and high-pressure boundary of hydrate formation in the ethane-water system.

PubMed

Kurnosov, Alexander V; Ogienko, Andrey G; Goryainov, Sergei V; Larionov, Eduard G; Manakov, Andrey Y; Lihacheva, Anna Y; Aladko, Eugeny Y; Zhurko, Fridrikh V; Voronin, Vladimir I; Berger, Ivan F; Ancharov, Aleksei I

2006-11-02

Dissociation temperatures of gas hydrate formed in the ethane-water system were studied at pressures up to 1500 MPa. In situ neutron diffraction analysis and X-ray diffraction analysis in a diamond anvil cell showed that the gas hydrate formed in the ethane-water system at 340, 700, and 1840 MPa and room temperature belongs to the cubic structure I (CS-I). Raman spectra of C-C vibrations of ethane molecules in the hydrate phase, as well as the spectra of solid and liquid ethane under high-pressure conditions were studied at pressures up to 6900 MPa. Within 170-3600 MPa Raman shift of the C-C vibration mode of ethane in the hydrate phase did not show any discontinuities, which could be evidence of possible phase transformations. The upper pressure boundary of high-pressure hydrate existence was discovered at the pressure of 3600 MPa. This boundary corresponds to decomposition of the hydrate to solid ethane and ice VII. The type of phase diagram of ethane-water system was proposed in the pressure range of hydrate formation (0-3600 MPa).

Metallic glass formation at the interface of explosively welded Nb and stainless steel

NASA Astrophysics Data System (ADS)

Bataev, I. A.; Hokamoto, K.; Keno, H.; Bataev, A. A.; Balagansky, I. A.; Vinogradov, A. V.

2015-07-01

The interface between explosively welded niobium and stainless steel SUS 304 was studied using scanning electron microscopy, transmission electron microscopy and energy dispersive X-Ray spectroscopy. The wavy interface along which vortex zones were located was observed. The vortex zones formed due to the mixing of materials typically had amorphous structure. Inoue's criteria of glass formation were used to explain this result. The effect of the composition, cooling rate and pressure on the glass formation are discussed. The conditions of deformation, heating, and cooling as well as shockwaves propagation were numerically simulated. We show that the conditions of vortex zone formation resemble the conditions of rapid solidification processes. In contrast to the "classical" methods of rapid solidification of melt, the conditions of metastable phase formation during explosive welding are significantly complicated by the fluctuations of composition and pressure. Possible metastable structures formation at the interface of some common explosively joined materials is predicted.

Bull heading to kill live gas wells

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

Oudeman, P.; Avest, D. ter; Grodal, E.O.

1994-12-31

To kill a live closed-in gas well by bull heading down the tubing, the selected pump rate should be high enough to ensure efficient displacement of the gas into the formation (i.e., to avoid the kill fluid bypassing the gas). On the other hand, the pressures that develop during bull heading at high rate must not exceed wellhead pressure rating, tubing or casing burst pressures or the formation breakdown gradient, since this will lead, at best, to a very inefficient kill job. Given these constraints, the optimum kill rate, requited hydraulic horsepower, density and type of kill fluids have tomore » be selected. For this purpose a numerical simulator has been developed, which predicts the sequence of events during bull heading. Pressures and flow rates in the well during the kill job are calculated, taking to account slip between the gas and kill fluid, hydrostatic and friction pressure drop, wellbore gas compression and leak-off to the formation. Comparison with the results of a dedicated field test demonstrates that these parameters can be estimated accurately. Example calculations will be presented to show how the simulator can be used to identify an optimum kill scenario.« less

Novel design for transparent high-pressure fuel injector nozzles.

PubMed

Falgout, Z; Linne, M

2016-08-01

The efficiency and emissions of internal combustion (IC) engines are closely tied to the formation of the combustible air-fuel mixture. Direct-injection engines have become more common due to their increased practical flexibility and efficiency, and sprays dominate mixture formation in these engines. Spray formation, or rather the transition from a cylindrical liquid jet to a field of isolated droplets, is not completely understood. However, it is known that nozzle orifice flow and cavitation have an important effect on the formation of fuel injector sprays, even if the exact details of this effect remain unknown. A number of studies in recent years have used injectors with optically transparent nozzles (OTN) to allow observation of the nozzle orifice flow. Our goal in this work is to design various OTN concepts that mimic the flow inside commercial injector nozzles, at realistic fuel pressures, and yet still allow access to the very near nozzle region of the spray so that interior flow structure can be correlated with primary breakup dynamics. This goal has not been achieved until now because interior structures can be very complex, and the most appropriate optical materials are brittle and easily fractured by realistic fuel pressures. An OTN design that achieves realistic injection pressures and grants visual access to the interior flow and spray formation will be explained in detail. The design uses an acrylic nozzle, which is ideal for imaging the interior flow. This nozzle is supported from the outside with sapphire clamps, which reduces tensile stresses in the nozzle and increases the nozzle's injection pressure capacity. An ensemble of nozzles were mechanically tested to prove this design concept.

METHOD OF SOLID STATE WELDING

DOEpatents

Storchheim, S.

1958-07-10

An improved method is described for pressure bonding of dissimilar metals, particularly nickel and aluminum. Using ordinary techniques for the pressure bonding of these metals, an alloy zone is usually formed between the metals, and this alloy zone exhibits undesirable brittleness and lack of tensile strengh. Formation of this alloy zone can be inhibited or prevented by heating the metals being bonded to a temperature below the melting point of either of the metals and using very high pressures for short periods of time. In this manner a bond is formed without the formation of the undesirable alloy zone.

Architecture Controls on Reservoir Performance of Zubair Formation, Rumaila and West Qurna Oilfields in the Southern Iraq

NASA Astrophysics Data System (ADS)

Al-Ziayyir, Haitham; Hodgetts, David

2015-04-01

The main reservoir in Rumaila /West Qurna oilfields is the Zubair Formation of Hautervian and Barremian age. This silicilastic formation extends over the regions of central and southern Iraq. This study attempts to improve the understanding of the architectural elements and their control on fluid flow paths within the Zubair Formation. A significant source of uncertainty in the zubair formation is the control on hydrodynamic pressure distribution. The reasons for pressure variation in the Zubair are not well understood. This work aims to reduce this uncertainty by providing a more detailed knowledge of reservoir architecture, distribution of barriers and baffles, and reservoir compartmentalization. To characterize the stratigraphic architecture of the Zubair formation,high resolution reservoir models that incorporate dynamic and static data were built. Facies modelling is accomplished by means of stochastic modelling techniques.The work is based on a large data set collected from the Rumaila oilfields. These data, comprising conventional logs of varying vintages, NMR logs, cores from six wells, and pressure data, were used for performing geological and petrophysical analyses.Flow simulation studies have also been applied to examine the impact of architecture on recovery. Understanding of geology and reservoir performance can be greatly improved by using an efficient, quick and viable integrated analysis, interpretation, and modelling.

Active CO2 Reservoir Management: A Strategy for Controlling Pressure, CO2 and Brine Migration in Saline-Formation CCS

NASA Astrophysics Data System (ADS)

Buscheck, T. A.; Sun, Y.; Hao, Y.; Court, B.; Celia, M. A.; Wolery, T.; Tompson, A. F.; Aines, R. D.; Friedmann, J.

2010-12-01

CO2 capture and sequestration (CCS) in deep geological formations is regarded as a promising means of lowering the amount of CO2 emitted to the atmosphere and thereby mitigate global warming. The most promising systems for CCS are depleted oil reservoirs, particularly those suited to CO2-based Enhanced Oil Recovery (CCS-EOR), and deep saline formations, both of which are well separated from the atmosphere. For conventional, industrial-scale, saline-formation CCS, pressure buildup can have a limiting effect on CO2 storage capacity. To address this concern, we analyze Active CO2 Reservoir Management (ACRM), which combines brine extraction and residual-brine reinjection with CO2 injection, comparing it with conventional saline-formation CCS. We investigate the influence of brine extraction on pressure response and CO2 and brine migration using the NUFT code. By extracting brine from the lower portion of the storage formation, from locations progressively further from the center of injection, we can counteract buoyancy that drives CO2 to the top of the formation, which is useful in dipping formations. Using “push-pull” manipulation of the CO2 plume, we expose less of the caprock seal to CO2 and more of the storage formation to CO2, with more of the formation utilized for trapping mechanisms. Plume manipulation can also counteract the influence of heterogeneity. We consider the impact of extraction ratio, defined as net extracted brine volume (extraction minus reinjection) divided by injected CO2 volume. Pressure buildup is reduced with increasing extraction ratio, which reduces CO2 and brine migration, increases CO2 storage capacity, and reduces other risks, such as leakage up abandoned wells, caprock fracturing, fault activation, and induced seismicity. For a 100-yr injection period, a 10-yr delay in brine extraction does not diminish the magnitude of pressure reduction. Moreover, it is possible to achieve pressure management with just a few brine-extraction wells, located far from the injection zone. For an extraction ratio of 1, pressure buildup is minimized, greatly reducing the Area of Review, as well as the area required for securing mineral rights. For an extraction ratio of 1, CO2 and brine migration are unaffected by neighboring CO2 operations, which allows planning, assessing, and conducting of each operation to be carried out independently; thus, permits could be granted on a single-site basis. Brine-extraction wells will be useful during monitoring, providing information for system calibration and history matching. One of several key aspects that ACRM has in common with CCS-EOR is the possibility of generating revenue from the extracted fluids; namely, fresh water produced via brine desalination, using technologies such as Reverse Osmosis. These benefits can offset brine extraction and treatment costs, streamline permitting, and help gain public acceptance. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Valley formation by groundwater seepage, pressurized groundwater outbursts and crater-lake overflow in flume experiments with implications for Mars

NASA Astrophysics Data System (ADS)

Marra, Wouter A.; Braat, Lisanne; Baar, Anne W.; Kleinhans, Maarten G.

2014-04-01

Remains of fluvial valleys on Mars reveal the former presence of water on the surface. However, the source of water and the hydrological setting is not always clear, especially in types of valleys that are rare on Earth and where we have limited knowledge of the processes involved. We investigated three hydrological scenarios for valley formation on Mars: hydrostatic groundwater seepage, release of pressurized groundwater and crater-lake overflow. Using physical modeling in laboratory experiments and numerical hydrological modeling we quantitatively studied the morphological development and processes involved in channel formation that result from these different sources of water in unconsolidated sediment. Our results show that valleys emerging from seeping groundwater by headward erosion form relatively slowly as fluvial transport takes place in a channel much smaller than the valley. Pressurized groundwater release forms a characteristic source area at the channel head by fluidization processes. This head consist of a pit in case of superlithostatic pressure and may feature small radial channels and collapse features. Valleys emerging from a crater-lake overflow event develop quickly in a run-away process of rim erosion and discharge increase. The valley head at the crater outflow point has a converging fan shape, and the rapid incision of the rim leaves terraces and collapse features. Morphological elements observed in the experiments can help in identifying the formative processes on Mars, when considerations of experimental scaling and lithological characteristics of the martian surface are taken into account. These morphological features might reveal the associated hydrological settings and formative timescales of a valley. An estimate of formative timescale from sediment transport is best based on the final channel dimensions for groundwater seepage valleys and on the valley dimensions for pressurized groundwater release and crater-lake overflow valleys. Our experiments show that different sources of water form valleys of similar size in quite different timescales.

Study on Flake Formation Behavior and Its Influence Factors in Cr5 Steel

PubMed Central

Chen, Huitao; Zhao, Wu; Yan, Liang

2018-01-01

A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism, previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However, according to recent studies, the hydrogen leads to the decline of the mechanical properties of steel, which is known as hydrogen embrittlement, is another reason for flake formation. In addition, the phenomenon of stress induced hydrogen uphill diffusion should not be neglected. All of the three behaviors are at work simultaneously. In order to further explore the formation mechanism of flakes in steel, the process of flake initiation and growth were studied with the following three coupling factors: trap hydrogen pressure, hydrogen embrittlement, and stress induced hydrogen re-distribution. The analysis model was established using the finite element method, and a crack whose radius is 0.5 mm was set in its center. The cohesive method and Bilinear Traction Separate Law (BTSL) were used to address the coupling effect. The results show that trap hydrogen pressure is the main driving force for flake formation. After the high hydrogen pressure was generated around the trap, a stress field formed. In addition, the trap is the center of stress concentration. Then, hydrogen is concentrated in a distribution around this trap, and most of the steel mechanical properties are reduced. The trap size is a key factor for defining the critical hydrogen content for flake formation and propagation. However, when the trap size exceeds the specified value, the critical hydrogen content does not change any more. As for the crack whose radius is 0.5 mm, the critical hydrogen content of Cr5VMo steel is 2.2 ppm, which is much closer to the maximum safe hydrogen concentration of 2.0 ppm used in China. The work presented in this article increases our understanding of flake formation and propagation mechanisms in steel. PMID:29702610

A High-Pressure Study of Manganese Metal and its Reactions with CO2 at 6, 23, and 44 GPa

NASA Astrophysics Data System (ADS)

Sawchuk, K. L. S.; McGuire, C. P.; Greenburg, A.; Makhluf, A.; Kavner, A.

2017-12-01

The free energies of formation of oxides and carbonates at the extreme pressures and temperatures of Earth's interior provides some of the thermodynamic constrains for models of mantle/core formation and subsequent chemical evolution. The broad goal of our research program is to measure the pressure- and temperature-dependence of free energies of formation of transition metal oxides and carbonates. This requires measurements of the phase stability, density, and thermoelastic properties of metals, oxides, and carbonates at deep-Earth and planetary conditions. Manganese is of interest because it is one of the most abundant transition metal geochemical tracers, it readily forms a carbonate at ambient pressure, and its high-pressure carbonate and oxide densities and equation of state parameters are relatively unknown. Here we report new data on the pressure/volume equation of state and structure of manganese metal as well as its reactions with CO2. These measurements were made using a laser heated diamond anvil cell in conjunction with synchrotron-based X-ray diffraction at beamline 12.2.2 at the Advanced Light Source. Three samples of manganese metal were gas-loaded in a CO2 pressure medium and pressurized to 6, 23, and 44 GPa. Upon laser heating, the CO2 reacted with the Mn metal generating new phases. To analyze the diffraction patterns, we we use a python-based program developed in-house for extracting high resolution 2-dimensional diffraction peak position and intensity information from two-dimensional X-ray diffraction patterns. At each pressure step, the structure and density of the quenched Mn metal phase was determined. At 6 GPa, Mn metal adopts a BCC structure, and at 23 GPa a tetragonal distortion is observed in the lattice. The measured equation of state is in good agreement with an existing meaurement by Fujihisa and Takemura (1995). MnCO3 rhodochrosite is observed in the sample quenched after heating at 6 GPa. Additional high pressure phases are evident in the diffraction patterns from the samples at 23 GPa and 44 GPa. The density and equation of state parameters for our observed oxide, carbonate, and metal manganese structures are used in conjunction with existing thermodynamic information to predict how the free energies of formation of Mn- oxide and Mn-carbonate change as a function of pressure.

Methane hydrate synthesis from ice: Influence of pressurization and ethanol on optimizing formation rates and hydrate yield

USGS Publications Warehouse

Chen, Po-Chun.; Huang, Wuu-Liang; Stern, Laura A.

2010-01-01

Polycrystalline methane gas hydrate (MGH) was synthesized using an ice-seeding method to investigate the influence of pressurization and ethanol on the hydrate formation rate and gas yield of the resulting samples. When the reactor is pressurized with CH4 gas without external heating, methane hydrate can be formed from ice grains with yields up to 25% under otherwise static conditions. The rapid temperature rise caused by pressurization partially melts the granular ice, which reacts with methane to form hydrate rinds around the ice grains. The heat generated by the exothermic reaction of methane hydrate formation buffers the sample temperature near the melting point of ice for enough time to allow for continuous hydrate growth at high rates. Surprisingly, faster rates and higher yields of methane hydrate were found in runs with lower initial temperatures, slower rates of pressurization, higher porosity of the granular ice samples, or mixtures with sediments. The addition of ethanol also dramatically enhanced the formation of polycrystalline MGH. This study demonstrates that polycrystalline MGH with varied physical properties suitable for different laboratory tests can be manufactured by controlling synthesis procedures or parameters. Subsequent dissociation experiments using a gas collection apparatus and flowmeter confirmed high methane saturation (CH 4·2O, with n = 5.82 ± 0.03) in the MGH. Dissociation rates of the various samples synthesized at diverse conditions may be fitted to different rate laws, including zero and first order.

Borehole Stability in High-Temperature Formations

NASA Astrophysics Data System (ADS)

Yan, Chuanliang; Deng, Jingen; Yu, Baohua; Li, Wenliang; Chen, Zijian; Hu, Lianbo; Li, Yang

2014-11-01

In oil and gas drilling or geothermal well drilling, the temperature difference between the drilling fluid and formation will lead to an apparent temperature change around the borehole, which will influence the stress state around the borehole and tend to cause borehole instability in high geothermal gradient formations. The thermal effect is usually not considered as a factor in most of the conventional borehole stability models. In this research, in order to solve the borehole instability in high-temperature formations, a calculation model of the temperature field around the borehole during drilling is established. The effects of drilling fluid circulation, drilling fluid density, and mud displacement on the temperature field are analyzed. Besides these effects, the effect of temperature change on the stress around the borehole is analyzed based on thermoelasticity theory. In addition, the relationships between temperature and strength of four types of rocks are respectively established based on experimental results, and thermal expansion coefficients are also tested. On this basis, a borehole stability model is established considering thermal effects and the effect of temperature change on borehole stability is also analyzed. The results show that the fracture pressure and collapse pressure will both increase as the temperature of borehole rises, and vice versa. The fracture pressure is more sensitive to temperature. Temperature has different effects on collapse pressures due to different lithological characters; however, the variation of fracture pressure is unrelated to lithology. The research results can provide a reference for the design of drilling fluid density in high-temperature wells.

THE EFFECT OF GAS HYDRATES DISSOCIATION AND DRILLING FLUIDS INVASION UPON BOREHOLE STABILITY IN OCEANIC GAS HYDRATES-BEARING SEDIMENT

NASA Astrophysics Data System (ADS)

Ning, F.; Wu, N.; Jiang, G.; Zhang, L.

2009-12-01

Under the condition of over-pressure drilling, the solid-phase and liquid-phase in drilling fluids immediately penetrate into the oceanic gas hydrates-bearing sediment, which causes the water content surrounding the borehole to increase largely. At the same time, the hydrates surrounding borehole maybe quickly decompose into water and gas because of the rapid change of temperature and pressure. The drilling practices prove that this two factors may change the rock characteristics of wellbore, such as rock strength, pore pressure, resistivity, etc., and then affect the logging response and evaluation, wellbore stability and well safty. The invasion of filtrate can lower the angle of friction and weaken the cohesion of hydrates-bearing sediment,which is same to the effect of invading into conventional oil and gas formation on borehole mechnical properties. The difference is that temperature isn’t considered in the invasion process of conventional formations while in hydrates-bearing sediments, it is a factor that can not be ignored. Temperature changes can result in hydrates dissociating, which has a great effect on mechanical properties of borehole. With the application of numerical simulation method, we studied the changes of pore pressure and variation of water content in the gas hydrates-bearing sediment caused by drilling fluid invasion under pressure differential and gas hydrate dissociation under temperature differential and analyzed their influence on borehole stability.The result of simulation indicated that the temperature near borehole increased quickly and changed hardly any after 6 min later. About 1m away from the borehole, the temperature of formation wasn’t affected by the temperature change of borehole. At the place near borehole, as gas hydrate dissociated dramatically and drilling fluid invaded quickly, the pore pressure increased promptly. The degree of increase depends on the permeability and speed of temperature rise of formation around bohole. If the formation has a low permeability and is heated quickly, the dissociated gas and water couldn’t flow away in time, which is likely to bring a hazard of excess pore pressure. Especially in the area near the wall of borehole, the increase degree of pore pressure is high than other area because the dissociation of gas hydrates is relatively violent and hydraulic gradient is bigger. We also studied the distribution of water saturation around borehole after 10min, 30min and 60min respectively. It revealed that along with the invasion of drilling fluid and dissociation of gas hydrate, the degree of water saturation increased gradually. The effect of gas hydrate dissociation and drilling fluids invasion on borehole stability is to weaken mechanical properties of wellbore and change the pore pressure, then changes the effective stress of gas hydrates-bearing sediment. So temperature, pressure in the borehole and filter loss of drilling fluids should be controlled strictly to prevent gas hydrates from decomposing largely and in order to keep the borehole stability in the gas hydrates-bearing formations.

Abnormally high formation pressures, Potwar Plateau, Pakistan

USGS Publications Warehouse

Law, B.E.; Shah, S.H.A.; Malik, M.A.

1998-01-01

Abnormally high formation pressures in the Potwar Plateau of north-central Pakistan are major obstacles to oil and gas exploration. Severe drilling problems associated with high pressures have, in some cases, prevented adequate evaluation of reservoirs and significantly increased drilling costs. Previous investigations of abnormal pressure in the Potwar Plateau have only identified abnormal pressures in Neogene rocks. We have identified two distinct pressure regimes in this Himalayan foreland fold and thrust belt basin: one in Neogene rocks and another in pre-Neogene rocks. Pore pressures in Neogene rocks are as high as lithostatic and are interpreted to be due to tectonic compression and compaction disequilibrium associated with high rates of sedimentation. Pore pressure gradients in pre-Neogene rocks are generally less than those in Neogene rocks, commonly ranging from 0.5 to 0.7 psi/ft (11.3 to 15.8 kPa/m) and are most likely due to a combination of tectonic compression and hydrocarbon generation. The top of abnormally high pressure is highly variable and doesn't appear to be related to any specific lithologic seal. Consequently, attempts to predict the depth to the top of overpressure prior to drilling are precluded.

Origin of pressure effects on regioselectivity and enantioselectivity in the rhodium-catalyzed hydroformylation of styrene with (S,S,S)-BisDiazaphos.

PubMed

Watkins, Avery L; Landis, Clark R

2010-08-04

Gas pressure influences the regioselectivity and enantioselectivity of aryl alkene hydroformylation as catalyzed by rhodium complexes of the BisDiazaphos ligand. Deuterioformylation of styrene at 80 degrees C results in extensive deuterium incorporation into the terminal position of the recovered styrene. This result establishes that rhodium hydride addition to form a branched alkyl rhodium occurs reversibly. The independent effect of carbon monoxide and hydrogen partial pressures on regioselectivity and enantioselectivity were measured. From 40 to 120 psi, both regioisomer (b:l) and enantiomer (R:S) ratios are proportional to the carbon monoxide partial pressure but approximately independent of the hydrogen pressure. The absolute rate for linear aldehyde formation was found to be inhibited by carbon monoxide pressure, whereas the rate for branched aldehyde formation is independent of CO pressure up to 80 psi; above 80 psi one observes the onset of inhibition. The carbon monoxide dependence of the rate and enantioselectivity for branched aldehyde indicates that the rate of production of (S)-2-phenyl propanal is inhibited by CO pressure, while the formation rate of the major enantiomer, (R)-2-phenyl propanal, is approximately independent of CO pressure. Hydroformylation of alpha-deuteriostyrene at 80 degrees C followed by conversion to (S)-2-benzyl-4-nitrobutanal reveals that 83% of the 2-phenylpropanal resulted from rhodium hydride addition to the re face of styrene, and 83% of the 3-phenylpropanal resulted from rhodium hydride addition to the si face of styrene. On the basis of these results, kinetic and steric/electronic models for the determination of regioselectivity and enantioselectivity are proposed.

Open-cell cloud formation over the Bahamas

NASA Technical Reports Server (NTRS)

2002-01-01

What atmospheric scientists refer to as open cell cloud formation is a regular occurrence on the back side of a low-pressure system or cyclone in the mid-latitudes. In the Northern Hemisphere, a low-pressure system will draw in surrounding air and spin it counterclockwise. That means that on the back side of the low-pressure center, cold air will be drawn in from the north, and on the front side, warm air will be drawn up from latitudes closer to the equator. This movement of an air mass is called advection, and when cold air advection occurs over warmer waters, open cell cloud formations often result. This MODIS image shows open cell cloud formation over the Atlantic Ocean off the southeast coast of the United States on February 19, 2002. This particular formation is the result of a low-pressure system sitting out in the North Atlantic Ocean a few hundred miles east of Massachusetts. (The low can be seen as the comma-shaped figure in the GOES-8 Infrared image from February 19, 2002.) Cold air is being drawn down from the north on the western side of the low and the open cell cumulus clouds begin to form as the cold air passes over the warmer Caribbean waters. For another look at the scene, check out the MODIS Direct Broadcast Image from the University of Wisconsin. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Grapevine species from varied native habitats exhibit differences in embolism formation/repair associated with leaf gas exchange and root pressure.

PubMed

Knipfer, Thorsten; Eustis, Ashley; Brodersen, Craig; Walker, Andrew M; McElrone, Andrew J

2015-08-01

Drought induces xylem embolism formation, but grapevines can refill non-functional vessels to restore transport capacity. It is unknown whether vulnerability to embolism formation and ability to repair differ among grapevine species. We analysed in vivo embolism formation and repair using x-ray computed microtomography in three wild grapevine species from varied native habitats (Vitis riparia, V. arizonica, V. champinii) and related responses to measurements of leaf gas exchange and root pressure. Vulnerability to embolism formation was greatest in V. riparia, intermediate in V. arizonica and lowest in V. champinii. After re-watering, embolism repair was rapid and pronounced in V. riparia and V. arizonica, but limited or negligible in V. champinii even after numerous days. Similarly, root pressure measured after re-watering was positively correlated with drought stress severity for V. riparia and V. arizonica (species exhibiting embolism repair) but not for V. champinii. Drought-induced reductions in transpiration were greatest for V. riparia and least in V. champinii. Recovery of transpiration after re-watering was delayed for all species, but was greatest for V. champinii and most rapid in V. arizonica. These species exhibit varied responses to drought stress that involve maintenance/recovery of xylem transport capacity coordinated with root pressure and gas exchange responses. © 2014 John Wiley & Sons Ltd.

On Porosity Formation in Metal Matrix Composites Made with Dual-Scale Fiber Reinforcements Using Pressure Infiltration Process

NASA Astrophysics Data System (ADS)

Etemadi, Reihaneh; Pillai, Krishna M.; Rohatgi, Pradeep K.; Hamidi, Sajad Ahmad

2015-05-01

This is the first such study on porosity formation phenomena observed in dual-scale fiber preforms during the synthesis of metal matrix composites (MMCs) using the gas pressure infiltration process. In this paper, different mechanisms of porosity formation during pressure infiltration of Al-Si alloys into Nextel™ 3D-woven ceramic fabric reinforcements (a dual-porosity or dual-scale porous medium) are studied. The effect of processing conditions on porosity content of the ceramic fabric infiltrated by the alloys through the gas PIP (PIP stands for "Pressure Infiltration Process" in which liquid metal is injected under pressure into a mold packed with reinforcing fibers.) is investigated. Relative density (RD), defined as the ratio of the actual MMC density and the density obtained at ideal 100 pct saturation of the preform, was used to quantify the overall porosity. Increasing the infiltration temperature led to an increase in RD due to reduced viscosity of liquid metal and enhanced wettability leading to improved feedability of the liquid metal. Similarly, increasing the infiltration pressure led to enhanced penetration of fiber tows and resulted in higher RD and reduced porosity. For the first time, the modified Capillary number ( Ca*), which is found to predict formation of porosity in polymer matrix composites quite well, is employed to study porosity in MMCs made using PIP. It is observed that in the high Ca* regime which is common in PIP, the overall porosity shows a strong downward trend with increasing Ca*. In addition, the effect of matrix shrinkage on porosity content of the samples is studied through using a zero-shrinkage Al-Si alloy as the matrix; usage of this alloy as the matrix led to a reduction in porosity content.

Volumetric analysis of formation of the complex of G-quadruplex DNA with hemin using high pressure.

PubMed

Takahashi, Shuntaro; Bhowmik, Sudipta; Sugimoto, Naoki

2017-01-01

DNA guanine-quadruplexes (G-quadruplexes) complexed with the Fe-containing porphyrin, hemin (iron(III)-protoporphyrin IX), can catalyze oxidation reactions. This so-called DNAzyme has been widely used in the field of DNA nanotechnology. To improve DNAzyme properties, we sought to elucidate the interaction mechanism between G-quadruplex DNA and hemin. Here, we performed volumetric analyses of formation of the complex between an oligonucleotide with the sequence of human telomeric DNA (h-telo) and hemin. The G-quadruplex DNA alone and the G-quadruplex DNA-hemin complex were destabilized with increasing pressure in Na + buffer. The pressure required to destabilize the h-telo-hemin complex was less in K + -containing buffer than in buffer with Na + , which indicates that there was a smaller volumetric change upon h-telo formation in K + buffer than in Na + buffer. The calculated change in h-telo-hemin binding volume (∆V b ) in the Na + buffer was 2.5mLmol -1 , whereas it was -41.7 in mLmol -1 the K + buffer. The DNAzyme activity in the K + buffer was higher than that in the Na + buffer at atmospheric pressure. Interestingly, the pressure effect on the destabilization of the h-telo-hemin complex in the presence of poly(ethylene glycol)200 (PEG200) was repressed compared to that in the absence of PEG200. These results suggest that differences in volumetric parameters reflect different mechanisms of interaction between hemin and h-telo due to differences in both the fit of hemin into the h-telo structure and hydration. Thus, the pressure-based thermodynamic analysis provided important information about complex formation and could be a useful index to improve function of DNAzymes. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of nitric oxide on photochemical ozone formation in mixtures of air with molecular chlorine and with trichlorofluoromethane

NASA Technical Reports Server (NTRS)

Bittker, D. A.; Wong, E. L.

1978-01-01

Ozone formation in a reaction chamber at room temperature and atmospheric pressure were studied for the photolysis of mixtures of NO with either Cl2 or CFCl3 in air. Both Cl2 + NO and CFCl3 + NO in air strongly inhibited O3 formation during the entire 3 to 4 hour reaction. A chemical mechanism that explains the results was presented. An important part of this mechanism was the formation and destruction of chlorine nitrate. Computations were performed with this same mechanism for CFCl3-NO-air mixtures at stratospheric temperatures, pressures, and concentrations. Results showed large reductions in steady-state O3 concentrations in these mixtures as compared with pure air.

String cavitation formation inside fuel injectors

NASA Astrophysics Data System (ADS)

Reid, B. A.; Gavaises, M.; Mitroglou, N.; Hargrave, G. K.; Garner, C. P.; McDavid, R. M.

2015-12-01

The formation of vortex or ‘string’ cavitation has been visualised at pressures up to 2000 bar in an automotive-sized optical diesel fuel injector nozzle. The multi-hole nozzle geometry studied allowed observation of the hole-to-hole vortex interaction and, in particular, that of a bridging vortex in the sac region between the holes. Above a threshold Reynolds number, their formation and appearance during a 2 ms injection event was repeatable and independent of upstream pressure and cavitation number. In addition, two different hole layouts and threedimensional flow simulations have been employed to describe how, the relative positions of adjacent holes influenced the formation and hole-to-hole interaction of the observed string cavitation vortices, with good agreement between the experimental and simulation results being achieved.

[Calculi formation and biliary hydrodynamics].

PubMed

Zou, S Q

1990-09-01

In this study, 167 white rabbits were divided into 5 groups to observe the effects of biliary stricture and infection on the formation of bile duct stones and the pathophysiological changes of the biliary tract. It was found that there was a gradient of static hydraulic pressure along biliary tract and the pressure was directly proportional to hepatic blood flow. In the rabbits with bile duct stone formation, the activity of SDH, ATP ase and glycogen (PAS) in the mucosa of biliary tract was low and that of LDH was high. In the biliary tract wall damaged by infection and choledocholithiasis, a frame work consisting of polysaccharide protein, mucin, and mucoid polymer was observed and the authors considered it as one of causing factors in the formation of the stones.

Silicon nitride-aluminum oxide solid solution (SiAION) formation and densification by pressure sintering

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Sanders, W. A.; Fiyalko, J. L.

1975-01-01

Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.

Method of well testing

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

Ringgenberg, P.D.; Burris, W.J.

1988-06-28

A method is described of flow testing a formation in a wellbore, comprising: providing a testing string including at least one annulus pressure responsive tool bore closure valve; providing a packer and setting the packer in the wellbore to seal thereacross; running the testing string into the wellbore with the tool bore closure valve in an open position; stinging into the set packer with the bottom of the testing string; increasing pressure a first time in the wellbore annulus around the testing string and above the set packer without cycling the tool bore closure valve; reducing pressure in the wellboremore » annulus; closing the tool bore closure valve responsive to the pressure reduction; increasing pressure a second time in the wellbore annulus; reopening the tool bore closure valve responsive to the second increase; and flowing fluids from the formation through the reopened tool bore closure valve.« less

Optical Emission Studies of Copper Plasma Induced Using Infrared Transversely Excited Atmospheric (IR TEA) Carbon Dioxide Laser Pulses.

PubMed

Momcilovic, Milos; Kuzmanovic, Miroslav; Rankovic, Dragan; Ciganovic, Jovan; Stoiljkovic, Milovan; Savovic, Jelena; Trtica, Milan

2015-04-01

Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm. The effect of surrounding air pressure, in the pressure range 0.1 to 1013 mbar, on plasma formation and its characteristics was investigated. A linear dependence of intensity threshold for plasma formation on logarithm of air pressure was found. Lowering of the air pressure reduces the extent of gas breakdown, enabling better laser-target coupling and thus increases ablation. Optimum air pressure for target plasma formation was 0.1 mbar. Under that pressure, the induced plasma consisted of two clearly distinguished and spatially separated regions. The maximum intensity of emission, with sharp and well-resolved spectral lines and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The estimated excitation temperature in this zone was around 7000 K. The favorable signal to background ratio obtained in this plasma region indicates possible analytical application of TEA CO2 laser produced copper plasma. Detection limits of trace elements present in the Cu sample were on the order of 10 ppm (parts per million). Time-resolved measurements of spatially selected plasma zones were used to find a correlation between the observed spatial position and time delay.

Grapevine species from varied native habitats exhibit differences in embolism formation/repair associated with leaf gas exchange and root pressure

USDA-ARS?s Scientific Manuscript database

Drought induces xylem embolism formation, but grapevines can refill blocked conduits to restore transport capacity. It is unknown whether vulnerability to embolism formation and ability to repair differ among grapevine species. We analyzed in vivo embolism formation and repair using x-ray microtomog...

Biogenic amine formation and nitrite reactions in meat batter as affected by high-pressure processing and chilled storage.

PubMed

Ruiz-Capillas, C; Aller-Guiote, P; Carballo, J; Colmenero, F Jiménez

2006-12-27

Changes in biogenic amine formation and nitrite depletion in meat batters as affected by pressure-temperature combinations (300 MPa/30 min/7, 20, and 40 degrees C), cooking process (70 degrees C/30 min), and storage (54 days/2 degrees C) were studied. Changes in residual nitrite concentration in raw meat batters were conditioned by the temperature and not by the pressure applied. Cooking process decreased (P < 0.05) the residual nitrite concentration in all samples. High-pressure processing and cooking treatment increased (P < 0.05) the nitrate content. Whereas protein-bound nitrite concentration decreased with pressure processing, no effect was observed with the heating process of meat batters. High-pressure processing conditions had no effect on the rate of residual nitrite loss throughout the storage. The application of high pressure decreased (P < 0.05) the concentration of some biogenic amines (tyramine, agmatine, and spermine). Irrespective of the high processing conditions, generally, throughout storage biogenic amine levels did not change or increased, although quantitatively this effect was not very important.

Computational Fluid Dynamics Analysis of High Injection Pressure Blended Biodiesel

NASA Astrophysics Data System (ADS)

Khalid, Amir; Jaat, Norrizam; Faisal Hushim, Mohd; Manshoor, Bukhari; Zaman, Izzuddin; Sapit, Azwan; Razali, Azahari

2017-08-01

Biodiesel have great potential for substitution with petrol fuel for the purpose of achieving clean energy production and emission reduction. Among the methods that can control the combustion properties, controlling of the fuel injection conditions is one of the successful methods. The purpose of this study is to investigate the effect of high injection pressure of biodiesel blends on spray characteristics using Computational Fluid Dynamics (CFD). Injection pressure was observed at 220 MPa, 250 MPa and 280 MPa. The ambient temperature was kept held at 1050 K and ambient pressure 8 MPa in order to simulate the effect of boost pressure or turbo charger during combustion process. Computational Fluid Dynamics were used to investigate the spray characteristics of biodiesel blends such as spray penetration length, spray angle and mixture formation of fuel-air mixing. The results shows that increases of injection pressure, wider spray angle is produced by biodiesel blends and diesel fuel. The injection pressure strongly affects the mixture formation, characteristics of fuel spray, longer spray penetration length thus promotes the fuel and air mixing.

Proof-of-feasibility of using well bore deformation as a diagnostic tool to improve CO 2 sequestration

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

Murdoch, Larry; Moysey, Stephen; Germanovich, Leonid

Injecting CO 2 raises pore pressure and this causes subsurface formations to deform. The pattern and amount of deformation will reflect the distribution of pressure and formation properties in the subsurface, two quantities of interest during CO 2 storage. The hypothesis underlying this research is that the small deformation accompanying CO 2 storage can be measured and interpreted to improve the storage process.

Phase diagram of carbon and the factors limiting the quantity and size of natural diamonds

NASA Astrophysics Data System (ADS)

Blank, Vladimir D.; Churkin, Valentin D.; Kulnitskiy, Boris A.; Perezhogin, Igor A.; Kirichenko, Alexey N.; Denisov, Viktor N.; Erohin, Sergey V.; Sorokin, Pavel B.; Popov, Mikhail Yu

2018-03-01

Phase diagrams of carbon, and those focusing on the graphite-to-diamond transitional conditions in particular, are of great interest for fundamental and applied research. The present study introduces a number of experiments carried out to convert graphite under high-pressure conditions, showing a formation of stable phase of fullerene-type onions cross-linked by sp3-bonds in the 55-115 GPa pressure range instead of diamonds formation (even at temperature 2000-3000 K) and the already formed diamonds turn into carbon onions. Our results refute the widespread idea that diamonds can form at any pressure from 2.2 to 1000 GPa. The phase diagram built within this study allows us not only to explain the existing numerous experimental data on the formation of diamond from graphite, but also to make assumptions about the conditions of its growth in Earth’s crust.

Effect of high hydrostatic pressure on background microflora and furan formation in fruit purée based baby foods.

PubMed

Kultur, Gulcin; Misra, N N; Barba, Francisco J; Koubaa, Mohamed; Gökmen, Vural; Alpas, Hami

2018-03-01

The baby foods industry is currently seeking technologies to pasteurize products without formation of processing contaminants such as furan. This work demonstrates the applicability of high hydrostatic pressure (HHP) as a non-thermal decontamination intervention for fruit purée based baby foods. HHP processing was evaluated at 200, 300, and 400 MPa pressures, for 5, 10 and 15 min of treatment times at 25, 35 and 45 °C. HHP application at 400 MPa, 45 °C for 15 min ensured complete inactivation (about 6 log 10 ) of total mesophilic aerophiles, as well as yeasts and molds. No furan was detected in HHP processed products. Thus, the key advantage of HHP over thermal processing is the ability to achieve commercially acceptable microbiological inactivation while avoiding the formation of processing contaminants such as furan.

Rapid gas hydrate formation process

DOEpatents

Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

2013-01-15

The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

Formation and decomposition of ethane, propane, and carbon dioxide hydrates in silica gel mesopores under high pressure.

PubMed

Aladko, E Ya; Dyadin, Yu A; Fenelonov, V B; Larionov, E G; Manakov, A Yu; Mel'gunov, M S; Zhurko, F V

2006-10-05

The experimental data on decomposition temperatures for the gas hydrates of ethane, propane, and carbon dioxide dispersed in silica gel mesopores are reported. The studies were performed at pressures up to 1 GPa. It is shown that the experimental dependence of hydrate decomposition temperature on the size of pores that limit the size of hydrate particles can be described on the basis of the Gibbs-Thomson equation only if one takes into account changes in the shape coefficient that is present in the equation; in turn, the value of this coefficient depends on a method of mesopore size determination. A mechanism of hydrate formation in mesoporous medium is proposed. Experimental data providing evidence of the possibility of the formation of hydrate compounds in hydrophobic matrixes under high pressure are reported. Decomposition temperature of those hydrate compounds is higher than that for the bulk hydrates of the corresponding gases.

Molecular dynamics simulations of bubble formation and cavitation in liquid metals.

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

Insepov, Z.; Hassanein, A.; Bazhirov, T. T.

2007-11-01

Thermodynamics and kinetics of nano-scale bubble formation in liquid metals such as Li and Pb were studied by molecular dynamics (MD) simulations at pressures typical for magnetic and inertial fusion. Two different approaches to bubble formation were developed. In one method, radial densities, pressures, surface tensions, and work functions of the cavities in supercooled liquid lithium were calculated and compared with the surface tension experimental data. The critical radius of a stable cavity in liquid lithium was found for the first time. In the second method, the cavities were created in the highly stretched region of the liquid phase diagram;more » and then the stability boundary and the cavitation rates were calculated in liquid lead. The pressure dependences of cavitation frequencies were obtained over the temperature range 700-2700 K in liquid Pb. The results of MD calculations for cavitation rate were compared with estimates of classical nucleation theory (CNT).« less

Formation and decomposition of CO2-filled ice.

PubMed

Massani, B; Mitterdorfer, C; Loerting, T

2017-10-07

Recently it was shown that CO 2 -filled ice is formed upon compression of CO 2 -clathrate hydrate. Here we show two alternative routes of its formation, namely, by decompression of CO 2 /ice VI mixtures at 250 K and by isobaric heating of CO 2 /high-density amorphous ice mixtures at 0.5-1.0 GPa above 200 K. Furthermore, we show that filled ice may either transform into the clathrate at an elevated pressure or decompose to "empty" hexagonal ice at ambient pressure and low temperature. This complements the literature studies in which decomposition to ice VI was favoured at high pressures and low temperatures.

Formation and decomposition of CO2-filled ice

NASA Astrophysics Data System (ADS)

Massani, B.; Mitterdorfer, C.; Loerting, T.

2017-10-01

Recently it was shown that CO2-filled ice is formed upon compression of CO2-clathrate hydrate. Here we show two alternative routes of its formation, namely, by decompression of CO2/ice VI mixtures at 250 K and by isobaric heating of CO2/high-density amorphous ice mixtures at 0.5-1.0 GPa above 200 K. Furthermore, we show that filled ice may either transform into the clathrate at an elevated pressure or decompose to "empty" hexagonal ice at ambient pressure and low temperature. This complements the literature studies in which decomposition to ice VI was favoured at high pressures and low temperatures.

Preparation of novel layer-stack hexagonal CdO micro-rods by a pre-oxidation and subsequent evaporation process

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

Peng, Kun, E-mail: kpeng@hnu.edu.cn; Hunan Province Key Laboratory for Spray Deposition Technology and Application, Hunan University, Changsha 410082; Jiang, Pan

2014-12-15

Graphical abstract: Layer-stack hexagonal cadmium oxide (CdO) micro-rods were prepared. - Highlights: • Novel hexagonal layer-stack structure CdO micro-rods were synthesized by a thermal evaporation method. • The pre-oxidation, vapor pressure and substrate nature play a key role on the formation of CdO rods. • The formation mechanism of CdO micro-rods was explained. - Abstract: Novel layer-stack hexagonal cadmium oxide (CdO) micro-rods were prepared by pre-oxidizing Cd granules and subsequent thermal oxidation under normal atmospheric pressure. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to characterize the phase structure and microstructure. The pre-oxidation process, vapor pressure and substratemore » nature were the key factors for the formation of CdO micro-rods. The diameter of micro-rod and surface rough increased with increasing of thermal evaporation temperature, the length of micro-rod increased with the increasing of evaporation time. The formation of hexagonal layer-stack structure was explained by a vapor–solid mechanism.« less

Formation Mechanism of Surface Crack in Low Pressure Casting of A360 Alloy

NASA Astrophysics Data System (ADS)

Liu, Shan-Guang; Cao, Fu-Yang; Ying, Tao; Zhao, Xin-Yi; Liu, Jing-Shun; Shen, Hong-Xian; Guo, Shu; Sun, Jian-Fei

2017-12-01

A surface crack defect is normally found in low pressure castings of Al alloy with a sudden contraction structure. To further understand the formation mechanism of the defect, the mold filling process is simulated by a two-phase flow model. The experimental results indicate that the main reason for the defect deformation is the mismatching between the height of liquid surface in the mold and pressure in the crucible. In the case of filling, a sudden contraction structure with an area ratio smaller than 0.5 is obtained, and the velocity of the liquid front increases dramatically with the influence of inertia. Meanwhile, the pressurizing speed in the crucible remains unchanged, resulting in the pressure not being able to support the height of the liquid level. Then the liquid metal flows back to the crucible and forms a relatively thin layer solidification shell on the mold wall. With the increasing pressure in the crucible, the liquid level rises again, engulfing the shell and leading to a surface crack. As the filling velocity is characterized by the damping oscillations, surface cracks will form at different heights. The results shed light on designing a suitable pressurizing speed for the low pressure casting process.

Device for temporarily closing duct-formers in well completion apparatus

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

Zandmer, H.M.; Zandmer, S.M.

A duct-forming device is disclosed for use in a well completion apparatus of the kind, wherein a bore hole casing is positioned in a bore hole and duct-forming devices of alkali- and acid resistant metal-such as steel-are secured at spaced levels to the casing in alignment with holes machined in the casing wall. In accordance with the invention, a closure device is arranged within the duct-forming device which permits flow of predetermined amounts of liquid, such as acid, from the interior of the casing through the duct-forming device and into the producing formation, while gradually being moved by the liquidmore » into a position in which such fluid flow is prevented. After the fluid flow has been stopped by the closure device and when the formation pressure exceeds the pressure within the duct-forming device and the casing, fluid from the formation then forces the closure device toward and into the casing space to permit thereafter free flow of formation fluid into the duct-forming device and the casing or of pressurized treatment liquid from the casing into the formation. The inventive arrangement permits inter alia the establishment of a sufficient and substantially uniform feeding rate of treatment liquid, such as acid, from the casing into the producing formation through all the duct-formers in preparation for subsequent acidification or other treatments, such as sand fracking.« less

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.

Off-Axis Driven Current Effects on ETB and ITB Formations based on Bifurcation Concept

NASA Astrophysics Data System (ADS)

Pakdeewanich, J.; Onjun, T.; Chatthong, B.

2017-09-01

This research studies plasma performance in fusion Tokamak system by investigating parameters such as plasma pressure in the presence of an edge transport barrier (ETB) and an internal transport barrier (ITB) as the off-axis driven current position is varied. The plasma is modeled based on the bifurcation concept using a suppression function that can result in formation of transport barriers. In this model, thermal and particle transport equations, including both neoclassical and anomalous effects, are solved simultaneously in slab geometry. The neoclassical coefficients are assumed to be constant while the anomalous coefficients depend on gradients of local pressure and density. The suppression function, depending on flow shear and magnetic shear, is assumed to affect only on the anomalous channel. The flow shear can be calculated from the force balance equation, while the magnetic shear is calculated from the given plasma current. It is found that as the position of driven current peak is moved outwards from the plasma center, the central pressure is increased. But at some point it stars to decline, mostly when the driven current peak has reached the outer half of the plasma. The higher pressure value results from the combination of ETB and ITB formations. The drop in central pressure occurs because ITB stats to disappear.

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

Das, Kaushik, E-mail: kaushikdas2089@gmail.com; Kundu, Sarathi

Long chain fatty acid molecules (e.g., stearic and behenic acids) form a monolayer on water surface in the presence of Ba{sup 2+} ions at low subphase pH (≈ 5.5) and remain as a monolayer before collapse generally occurs at higher surface pressure (π{sub c} > 50 mN/m). Monolayer formation is verified from the surface pressure vs. area per molecule (π-A) isotherms and also from the atomic force microscopy (AFM) analysis of the films deposited by single upstroke of hydrophilic Si (001) substrate through the monolayer covered water surface. At high subphase pH (≈ 9.5), barium stearate molecules form multilayer structuremore » at lower surface pressure which is verified from the π-A isotherms and AFM analysis of the film deposited at 25 mN/m. Such monolayer to multilayer structure formation or monolayer collapse at lower surface pressure is unusual as at this surface pressure generally fatty acid salt molecules form a monolayer on the water surface. Formation of bidentate chelate coordination in the metal containing headgroups is the reason for such monolayer to multilayer transition. However, for longer chain barium behenate molecules only monolayer structure is maintained at that high subphase pH (≈ 9.5) due to the presence of relatively more tail-tail hydrophobic interaction.« less

Synthesis of Fullerenes in Low Pressure Benzene/Oxygen Diffusion Flames

NASA Technical Reports Server (NTRS)

Hebgen, Peter; Howard, Jack B.

1999-01-01

The interest in fullerenes is strongly increasing since their discovery by Kroto et al. in 1985 as products of the evaporation of carbon into inert gas at low pressure. Due to their all carbon closed-shell structure, fullerenes have many exceptional physical and chemical properties and a large potential for applications such as superconductors, sensors, catalysts, optical and electronic devices, polymers, high energy fuels, and biological and medical materials. This list is still growing, because the research on fullerenes is still at an early stage. Fullerenes can be formed not only in a system containing only carbon and an inert gas, but also in premixed hydrocarbon flames under reduced pressure and fuel rich conditions. The highest yields of fullerenes in flames are obtained under conditions of substantial soot formation. There is a need for more information on the yields of fullerenes under different conditions in order to understand the mechanisms of their formation and to enable the design of practical combustion systems for large-scale fullerene production. Little work has been reported on the formation of fullerenes in diffusion flames. In order to explore the yields of fullerenes and the effect of low pressure in diffusion flames, therefore we constructed and used a low pressure diffusion flame burner in this study.

Creating and maintaining a gas cap in tar sands formations

DOEpatents

Vinegar, Harold J.; Karanikas, John Michael; Dinkoruk, Deniz Sumnu; Wellington, Scott Lee

2010-03-16

Methods for treating a tar sands formation are disclosed herein. Methods for treating a tar sands formation may include providing heat to at least part of a hydrocarbon layer in the formation from one or more heaters located in the formation. Pressure may be allowed to increase in an upper portion of the formation to provide a gas cap in the upper portion. At least some hydrocarbons are produced from a lower portion of the formation.

Chondrule Crystallization Experiments

NASA Technical Reports Server (NTRS)

Hweins, R. H.; Connolly, H. C., Jr.; Lofgren, G. E.; Libourel, G.

2004-01-01

Given the great diversity of chondrules, laboratory experiments are invaluable in yielding information on chondrule formation process(es) and for deciphering their initial conditions of formation together with their thermal history. In addition, they provide some critical parameters for astrophysical models of the solar system and of nebular disk evolution in particular (partial pressures, temperature, time, opacity, etc). Most of the experiments simulating chondrules have assumed formation from an aggregate of solid grains, with total pressure of no importance and with virtually no gain or loss of elements from or to the ambient environment. They used pressed pellets attached to wires and suffered from some losses of alkalis and Fe.

Opportunities for increasing CO 2 storage in deep, saline formations by active reservoir management and treatment of extracted formation water: Case study at the GreenGen IGCC facility, Tianjin, PR China

DOE PAGES

Ziemkiewicz, Paul; Stauffer, Philip H.; Sullivan-Graham, Jeri; ...

2016-08-04

Carbon capture, utilization and storage (CCUS) seeks beneficial applications for CO 2 recovered from fossil fuel combustion. This study evaluated the potential for removing formation water to create additional storage capacity for CO 2, while simultaneously treating the produced water for beneficial use. Furthermore, the process would control pressures within the target formation, lessen the risk of caprock failure, and better control the movement of CO 2 within that formation. The project plans to highlight the method of using individual wells to produce formation water prior to injecting CO 2 as an efficient means of managing reservoir pressure. Because themore » pressure drawdown resulting from pre-injection formation water production will inversely correlate with pressure buildup resulting from CO 2 injection, it can be proactively used to estimate CO 2 storage capacity and to plan well-field operations. The project studied the GreenGen site in Tianjin, China where Huaneng Corporation is capturing CO 2 at a coal fired IGCC power plant. Known as the Tianjin Enhanced Water Recovery (EWR) project, local rock units were evaluated for CO 2 storage potential and produced water treatment options were then developed. Average treatment cost for produced water with a cooling water treatment goal ranged from 2.27 to 2.96 US$/m 3 (recovery 95.25%), and for a boiler water treatment goal ranged from 2.37 to 3.18 US$/m 3 (recovery 92.78%). Importance analysis indicated that water quality parameters and transportation are significant cost factors as the injection-extraction system is managed over time. Our study found that in a broad sense, active reservoir management in the context of CCUS/EWR is technically feasible. In addition, criteria for evaluating suitable vs. unsuitable reservoir properties, reservoir storage (caprock) integrity, a recommended injection/withdrawal strategy and cost estimates for water treatment and reservoir management are proposed.« less

Opportunities for increasing CO 2 storage in deep, saline formations by active reservoir management and treatment of extracted formation water: Case study at the GreenGen IGCC facility, Tianjin, PR China

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

Ziemkiewicz, Paul; Stauffer, Philip H.; Sullivan-Graham, Jeri

Carbon capture, utilization and storage (CCUS) seeks beneficial applications for CO 2 recovered from fossil fuel combustion. This study evaluated the potential for removing formation water to create additional storage capacity for CO 2, while simultaneously treating the produced water for beneficial use. Furthermore, the process would control pressures within the target formation, lessen the risk of caprock failure, and better control the movement of CO 2 within that formation. The project plans to highlight the method of using individual wells to produce formation water prior to injecting CO 2 as an efficient means of managing reservoir pressure. Because themore » pressure drawdown resulting from pre-injection formation water production will inversely correlate with pressure buildup resulting from CO 2 injection, it can be proactively used to estimate CO 2 storage capacity and to plan well-field operations. The project studied the GreenGen site in Tianjin, China where Huaneng Corporation is capturing CO 2 at a coal fired IGCC power plant. Known as the Tianjin Enhanced Water Recovery (EWR) project, local rock units were evaluated for CO 2 storage potential and produced water treatment options were then developed. Average treatment cost for produced water with a cooling water treatment goal ranged from 2.27 to 2.96 US$/m 3 (recovery 95.25%), and for a boiler water treatment goal ranged from 2.37 to 3.18 US$/m 3 (recovery 92.78%). Importance analysis indicated that water quality parameters and transportation are significant cost factors as the injection-extraction system is managed over time. Our study found that in a broad sense, active reservoir management in the context of CCUS/EWR is technically feasible. In addition, criteria for evaluating suitable vs. unsuitable reservoir properties, reservoir storage (caprock) integrity, a recommended injection/withdrawal strategy and cost estimates for water treatment and reservoir management are proposed.« less

Saturation meter

DOEpatents

Gregurech, S.

1984-08-01

A saturation meter for use in a pressurized water reactor plant comprising a differential pressure transducer having a first and second pressure sensing means and an alarm. The alarm is connected to the transducer and is preset to activate at a level of saturation prior to the formation of a steam void in the reactor vessel.

Initial reactive sticking coefficient of O 2 on Si(111)-7 × 7 at elevated temperatures

NASA Astrophysics Data System (ADS)

Shklyaev, A. A.; Suzuki, Takanori

1996-05-01

Kinetics of the initial stage of oxide growth in the reaction of oxygen with Si(111)-7 × 7 at temperatures from room temperature to Ttr, and pressures from 5 × 10 -9 to 2 × 10 -7 Torr are investigated with optical second-harmonic generation, here temperature from oxide growth to Si etching without oxide growth. At a fixed pressure, the initial reactive sticking coefficient ( S0), obtained from the rate of oxide growth, decreases with increasing temperature to S0=0 at Ttr. We have found that the initial reacti sticking coefficient depends on the O 2 pressure. At temperatures above 320°C, the whole temperature dependence of S0 is situated in the region of higher temperatures for higher O 2 pressures ( Pox). Moreover, an additional bend in the temperature dependence of S0 is observed for Pox>1 × 10 -8 Torr near Ttr. A precursor-mediated adsorption model involving the reaction of formation is considered. The parameters of this model, obtained from the best fits to the experimental data, show that oxide growth rate constant increases and volatile SiO formation rate constant decreases as a function of O 2 pressure. At zero oxide coverage, the pressure dependence of the reaction rate constants is suggested to originate from interaction in the layer of the chemisorbed precursor species, whose coverage depends on the O 2 pressure. The volatile SiO formation is described by a three-step sequential two-channel process through the chemisorbed O 2 precursor species, whereas one of the channels with a larger activation energy is suggested to induce the additional bend in S0( T) near Ttr at higher O 2 pressures.

Activation of Latent Dihydroorotase from Aquifex aeolicus by Pressure*

PubMed Central

Hervé, Guy; Evans, Hedeel Guy; Fernado, Roshini; Patel, Chandni; Hachem, Fatme; Evans, David R.

2017-01-01

Elevated hydrostatic pressure was used to probe conformational changes of Aquifex aeolicus dihydroorotase (DHO), which catalyzes the third step in de novo pyrimidine biosynthesis. The isolated protein, a 45-kDa monomer, lacks catalytic activity but becomes active upon formation of a dodecameric complex with aspartate transcarbamoylase (ATC). X-ray crystallographic studies of the isolated DHO and of the complex showed that association induces several major conformational changes in the DHO structure. In the isolated DHO, a flexible loop occludes the active site blocking the access of substrates. The loop is mostly disordered but is tethered to the active site region by several electrostatic and hydrogen bonds. This loop becomes ordered and is displaced from the active site upon formation of DHO-ATC complex. The application of pressure to the complex causes its time-dependent dissociation and the loss of both DHO and ATC activities. Pressure induced irreversible dissociation of the obligate ATC trimer, and as a consequence the DHO is also inactivated. However, moderate hydrostatic pressure applied to the isolated DHO subunit mimics the complex formation and reversibly activates the isolated subunit in the absence of ATC, suggesting that the loop has been displaced from the active site. This effect of pressure is explained by the negative volume change associated with the disruption of ionic interactions and exposure of ionized amino acids to the solvent (electrostriction). The interpretation that the loop is relocated by pressure was validated by site-directed mutagenesis and by inhibition by small peptides that mimic the loop residues. PMID:27746403

Deposit formation in hydrocarbon rocket fuels

NASA Technical Reports Server (NTRS)

Roback, R.; Szetela, E. J.; Spadaccini, L. J.

1981-01-01

An experimental program was conducted to study deposit formation in hydrocarbon fuels under flow conditions that exist in high-pressure, rocket engine cooling systems. A high pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon rocket fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6 to 30 m/sec, and tube wall temperatures in the range 422 to 811 K. Results indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800 K, with peak deposit formation occurring near 700 K. No improvements were obtained when deoxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. There appeared to be little difference between commercial-grade and chemically-pure propane with regard to type and quantity of deposit. Results of tests conducted with RP-1 indicated that the rate of deposit formation increased slightly with pressure over the range 136 atm to 340 atm. Finally, lating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel.

Nanobubbles at GPa Pressure under Graphene.

PubMed

Zamborlini, Giovanni; Imam, Mighfar; Patera, Laerte L; Menteş, Tevfik Onur; Stojić, Nataša; Africh, Cristina; Sala, Alessandro; Binggeli, Nadia; Comelli, Giovanni; Locatelli, Andrea

2015-09-09

We provide direct evidence that irradiation of a graphene membrane on Ir with low-energy Ar ions induces formation of solid noble-gas nanobubbles. Their size can be controlled by thermal treatment, reaching tens of nanometers laterally and height of 1.5 nm upon annealing at 1080 °C. Ab initio calculations show that Ar nanobubbles are subject to pressures reaching tens of GPa, their formation being driven by minimization of the energy cost of film distortion and loss of adhesion.

Triggering Star Formation: From the Pillars of Creation to the Formation of Our Solar System

NASA Astrophysics Data System (ADS)

Gritschneder, Matthias; Lin, Douglas N. C.

We study the evolution of molecular clouds under the influence of ionizing radiation. We propose that the Pipe Nebula is an HII region shell swept up by the B2 IV β Cephei star θ Ophiuchi. After reviewing the recent observations, we perform a series of analytical calculations. We are able to show that the current size, mass and pressure of the region can be explained in this scenario. The Pipe Nebula can be best described by a three phase medium in pressure equilibrium. The pressure support is provided by the ionized gas and mediated by an atomic component to confine the cores at the observed current pressure. We then present simulations on the future evolution as soon as the massive star explodes in a supernova. We show that a surviving core at the border of the HII-region (D = 5 pc) is getting enriched sufficiently with supernova material and is triggered into collapse fast enough to be consistent with the tight constraints put by meteoritic data of e.g.26Al on the formation of our Solar System. We therefore propose that the formation of the Solar System was triggered by the shock wave of a type IIa supernova interacting with surviving cold structures similar to the Pillars of Creation at the border of HII-regions.

Aerated drilling cutting transport analysis in geothermal well

NASA Astrophysics Data System (ADS)

Wakhyudin, Aris; Setiawan, Deni; Dwi Marjuan, Oscar

2017-12-01

Aeratad drilling widely used for geothermal drilling especially when drilled into predicted production zone. Aerated drilling give better performance on preventing lost circulation problem, improving rate of penetration, and avoiding drilling fluid invasion to productive zone. While well is drilled, cutting is produced and should be carried to surface by drilling fluid. Hole problem, especially pipe sticking will occur while the cutting is not lifted properly to surface. The problem will effect on drilling schedule; non-productive time finally result more cost to be spent. Geothermal formation has different characteristic comparing oil and gas formation. Geothermal mainly has igneous rock while oil and gas mostly sedimentary rock. In same depth, formation pressure in geothermal well commonly lower than oil and gas well while formation temperature geothermal well is higher. While aerated drilling is applied in geothermal well, Igneous rock density has higher density than sedimentary rock and aerated drilling fluid is lighter than water based mud hence minimum velocity requirement to transport cutting is larger than in oil/gas well drilling. Temperature and pressure also has impact on drilling fluid (aerated) density. High temperature in geothermal well decrease drilling fluid density hence the effect of pressure and temperature also considered. In this paper, Aerated drilling cutting transport performance on geothermal well will be analysed due to different rock and drilling fluid density. Additionally, temperature and pressure effect on drilling fluid density also presented to merge.

Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted Discharge

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Hallock, Ashley K.; Choueiri, Edgar Y.

2008-01-01

Data from an inductive conical theta pinch accelerator are presented to gain insight into the process of inductive current sheet formation in the presence of a preionized background gas produced by a steady-state RF-discharge. The presence of a preionized plasma has been previously shown to allow for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts, leading to greater accelerator efficiencies at lower power levels. Time-resolved magnetic probe measurements are obtained for different background pressures and pulse energies to characterize the effects of these parameters on current sheet formation. Indices are defined that describe time-resolved current sheet characteristics, such as the total current owing in the current sheet, the time-integrated total current ('strength'), and current sheet velocity. It is found that for a given electric field strength, maximums in total current, strength, and velocity occur for one particular background pressure. At other pressures, these current sheet indices are considerably smaller. The trends observed in these indices are explained in terms of the principles behind Townsend breakdown that lead to a dependence on the ratio of the electric field to the background pressure. Time-integrated photographic data are also obtained at the same experimental conditions, and qualitatively they compare quite favorably with the time-resolved magnetic field data.

Development of in vivo impedance spectroscopy techniques for measurement of micropore formation following microneedle insertion

PubMed Central

Brogden, Nicole K.; Ghosh, Priyanka; Hardi, Lucia; Crofford, Leslie J.; Stinchcomb, Audra L.

2013-01-01

Microneedles provide a minimally invasive means to enhance skin permeability by creating micron-scale channels (micropores) that provide a drug delivery pathway. Adequate formation of the micropores is critical to the success of this unique drug delivery technique. The objective of these studies was to develop sensitive and reproducible impedance spectroscopy techniques to monitor micropore formation in animal models and human subjects. Hairless guinea pigs, a Yucatan miniature pig, and human volunteers were treated with 100 microneedle insertions per site following an overnight pre-hydration period. Repeated measurements were made pre- and post-microneedle treatment using dry and gel Ag/AgCl electrodes applied with light vs. direct pressure to hold the electrode to the skin surface. Impedance measurements dropped significantly post-microneedle application at all sites (p < 0.05, irrespective of electrode type or gel application), confirming micropore formation. In the Yucatan pig and human subjects, gel electrodes with direct pressure yielded the lowest variability (demonstrated by lower %RSD), whereas dry electrodes with direct pressure were superior in the guinea pigs. These studies confirm that impedance measurements are suitable for use in both clinical and animal research environments to monitor formation of new micropores that will allow for drug delivery through the impermeable skin layers. PMID:23589356

Development of in vivo impedance spectroscopy techniques for measurement of micropore formation following microneedle insertion.

PubMed

Brogden, Nicole K; Ghosh, Priyanka; Hardi, Lucia; Crofford, Leslie J; Stinchcomb, Audra L

2013-06-01

Microneedles (MNs) provide a minimally invasive means to enhance skin permeability by creating micron-scale channels (micropores) that provide a drug delivery pathway. Adequate formation of the micropores is critical to the success of this unique drug delivery technique. The objective of the current work was to develop sensitive and reproducible impedance spectroscopy techniques to monitor micropore formation in animal models and human subjects. Hairless guinea pigs, a Yucatan miniature pig, and human volunteers were treated with 100 MN insertions per site following an overnight prehydration period. Repeated measurements were made pre- and post-MN treatment using dry and gel Ag/AgCl electrodes applied with light verses direct pressure to hold the electrode to the skin surface. Impedance measurements dropped significantly post-MN application at all sites (p < 0.05, irrespective of electrode type or gel application), confirming micropore formation. In the Yucatan pig and human subjects, gel electrodes with direct pressure yielded the lowest variability (demonstrated by lower %relative standard deviation), whereas dry electrodes with direct pressure were superior in the guinea pigs. These studies confirm that impedance measurements are suitable for use in both clinical and animal research environments to monitor the formation of new micropores that will allow for drug delivery through the impermeable skin layers. Copyright © 2013 Wiley Periodicals, Inc.

Numerical analysis of wellbore instability in gas hydrate formation during deep-water drilling

NASA Astrophysics Data System (ADS)

Zhang, Huaiwen; Cheng, Yuanfang; Li, Qingchao; Yan, Chuanliang; Han, Xiuting

2018-02-01

Gas hydrate formation may be encountered during deep-water drilling because of the large amount and wide distribution of gas hydrates under the shallow seabed of the South China Sea. Hydrates are extremely sensitive to temperature and pressure changes, and drilling through gas hydrate formation may cause dissociation of hydrates, accompanied by changes in wellbore temperatures, pore pressures, and stress states, thereby leading to wellbore plastic yield and wellbore instability. Considering the coupling effect of seepage of drilling fluid into gas hydrate formation, heat conduction between drilling fluid and formation, hydrate dissociation, and transformation of the formation framework, this study established a multi-field coupling mathematical model of the wellbore in the hydrate formation. Furthermore, the influences of drilling fluid temperatures, densities, and soaking time on the instability of hydrate formation were calculated and analyzed. Results show that the greater the temperature difference between the drilling fluid and hydrate formation is, the faster the hydrate dissociates, the wider the plastic dissociation range is, and the greater the failure width becomes. When the temperature difference is greater than 7°C, the maximum rate of plastic deformation around the wellbore is more than 10%, which is along the direction of the minimum horizontal in-situ stress and associated with instability and damage on the surrounding rock. The hydrate dissociation is insensitive to the variation of drilling fluid density, thereby implying that the change of the density of drilling fluids has a minimal effect on the hydrate dissociation. Drilling fluids that are absorbed into the hydrate formation result in fast dissociation at the initial stage. As time elapses, the hydrate dissociation slows down, but the risk of wellbore instability is aggravated due to the prolonged submersion in drilling fluids. For the sake of the stability of the wellbore in deep-water drilling through hydrate formation, the drilling fluid with low temperatures should be given priority. The drilling process should be kept under balanced pressures, and the drilling time should be shortened.

30 CFR 250.1617 - Application for permit to drill.

Code of Federal Regulations, 2011 CFR

2011-07-01

... well and for well control, including the following: (i) Pore pressure; (ii) Formation fracture..., fracture gradients of the exposed formations, casing setting depths, and cementing intervals, total well...

Wellbottom fluid implosion treatment system

DOEpatents

Brieger, Emmet F.

2001-01-01

A system for inducing implosion shock forces on perforation traversing earth formations with fluid pressure where an implosion tool is selected relative to a shut in well pressure and a tubing pressure to have a large and small area piston relationship in a well tool so that at a predetermined tubing pressure the pistons move a sufficient distance to open an implosion valve which permits a sudden release of well fluid pressure into the tubing string and produces an implosion force on the perforations. A pressure gauge on the well tool records tubing pressure and well pressure as a function of time.

A Comparison of Young Star Properties with Local Galactic Environment for LEGUS/LITTLE THINGS Dwarf Irregular Galaxies

NASA Astrophysics Data System (ADS)

Hunter, Deidre A.; Adamo, Angela; Elmegreen, Bruce G.; Gallardo, Samavarti; Lee, Janice C.; Cook, David O.; Thilker, David; Kayitesi, Bridget; Kim, Hwihyun; Kahre, Lauren; Ubeda, Leonardo; Bright, Stacey N.; Ryon, Jenna E.; Calzetti, Daniela; Tosi, Monica; Grasha, Kathryn; Messa, Matteo; Fumagalli, Michele; Dale, Daniel A.; Sabbi, Elena; Cignoni, Michele; Smith, Linda J.; Gouliermis, Dimitrios M.; Grebel, Eva K.; Aloisi, Alessandra; Whitmore, Bradley C.; Chandar, Rupali; Johnson, Kelsey E.

2018-07-01

We have explored the role environmental factors play in determining characteristics of young stellar objects in nearby dwarf irregular and blue compact dwarf galaxies. Star clusters are characterized by concentrations, masses, and formation rates; OB associations by mass and mass surface density; O stars by their numbers and near-ultraviolet absolute magnitudes; and H II regions by Hα surface brightnesses. These characteristics are compared to surrounding galactic pressure, stellar mass density, H I surface density, and star formation rate (SFR) surface density. We find no trend of cluster characteristics with environmental properties, implying that larger-scale effects are more important in determining cluster characteristics or that rapid dynamical evolution erases any memory of the initial conditions. On the other hand, the most massive OB associations are found at higher pressure and H I surface density, and there is a trend of higher H II region Hα surface brightness with higher pressure, suggesting that a higher concentration of massive stars and gas is found preferentially in regions of higher pressure. At low pressures we find massive stars but not bound clusters and OB associations. We do not find evidence for an increase of cluster formation efficiency as a function of SFR density. However, there is an increase in the ratio of the number of clusters to the number of O stars with increasing pressure, perhaps reflecting an increase in clustering properties with SFR.

Kinetics of Methane Clathrate Formation in the Presolar Nebula

NASA Astrophysics Data System (ADS)

Vu, Tuan; Choukroun, Mathieu

2016-10-01

Clathrate hydrates are a distinct form of water ice wherein the crystal lattice of the host water molecules forms symmetric, polyhedral cages that trap volatile guest species under appropriate pressures and temperatures. These materials are an abundant source of hydrocarbons on Earth, and have been expected to be present on a number of icy celestial bodies, including Mars, Europa, Titan, and Enceladus. Clathrates are also thought to be one of the most likely traps for volatiles during the condensation of the protostellar nebulae. Prior to the Voyager mission, the prevailing expectation was that the elemental composition of the giant planets would reflect the composition of the solar nebula and therefore be similar to solar abundances. However, spacecraft observations by Voyager, Galileo, and Cassini-Huygens, as well as ground-based observations, have revealed unexpected elemental enrichment, relative to solar abundances, of C, N, S, As, P, and noble gases in the giant planets and in comets. One of the contending explanations is the retention of these volatiles as clathrate hydrates, which may have enabled their capture early in the history of the Solar System.While the formation and stability of clathrates have been addressed theoretically and, to some extent, experimentally at relatively high pressures (10-7-10-3 bar), there is a scarcity of experimental undertaking on the kinetics of clathrate formation and their stability at the low pressures relevant to the early outer solar nebula (~10-11 bar). This study seeks to elucidate the clathrate formation kinetics under nebula-relevant conditions via a series of optical Raman experiments on ice/gas mixtures over a range of pressures and temperatures. Our work on the methane gas/ice system shows that clathrate formation occurs on a rather fast timescale (typically within minutes at 223-253 K and 30-50 bar CH4). In addition, the rate of enclathration increases with pressures and temperatures, and the activation energy for clathrate growth is found to be comparable to those for gas diffusion through ice. These results suggest that the energy barrier for clathrate formation is quite low, implying the likelihood of existence of these materials under nebular conditions.

Formation pressure testing at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Operational summary, history matching, and interpretations

USGS Publications Warehouse

Anderson, B.; Hancock, S.; Wilson, S.; Enger, C.; Collett, T.; Boswell, R.; Hunter, R.

2011-01-01

In February 2007, the U.S. Department of Energy, BP Exploration (Alaska), and the U.S. Geological Survey, collected open-hole pressure-response data, as well as gas and water sample collection, in a gas hydrate reservoir (the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well) using Schlumberger's Modular Dynamics Formation Tester (MDT) wireline tool. Four such MDT tests, ranging from six to twelve hours duration, and including a series of flow, sampling, and shut-in periods of various durations, were conducted. Locations for the testing were selected based on NMR and other log data to assure sufficient isolation from reservoir boundaries and zones of excess free water. Test stages in which pressure was reduced sufficiently to mobilize free water in the formation (yet not cause gas hydrate dissociation) produced readily interpretable pressure build-up profiles. Build-ups following larger drawdowns consistently showed gas-hydrate dissociation and gas release (as confirmed by optical fluid analyzer data), as well as progressive dampening of reservoir pressure build-up during sequential tests at a given MDT test station.History matches of one multi-stage, 12-h test (the C2 test) were accomplished using five different reservoir simulators: CMG-STARS, HydrateResSim, MH21-HYDRES, STOMP-HYD, and TOUGH. +. HYDRATE. Simulations utilized detailed information collected across the reservoir either obtained or determined from geophysical well logs, including thickness (11.3. m, 37 ft.), porosity (35%), hydrate saturation (65%), both mobile and immobile water saturations, intrinsic permeability (1000 mD), pore water salinity (5 ppt), and formation temperature (3.3-3.9 ??C). This paper will present the approach and preliminary results of the history-matching efforts, including estimates of initial formation permeability and analyses of the various unique features exhibited by the MDT results. ?? 2010 Elsevier Ltd.

Effect of pressure on high Karlovitz number lean turbulent premixed hydrogen-enriched methane-air flames using LES

NASA Astrophysics Data System (ADS)

Cicoria, David; Chan, C. K.

2017-07-01

Large eddy simulation (LES) is employed to investigate the effect of pressure on lean CH4-H2-air turbulent premixed flames at high Karlovitz number for mixtures up to 60% of hydrogen in volume. The subfilter combustion term representing the interaction between turbulence and chemistry is modelled using the PaSR model, along with complex chemistry using a skeletal mechanism based on GRI-MECH3.0. The influence of pressure at high turbulence levels is studied by means of the local flame structure, and the assessment of species formation inside the flame. Results show that the ratio of turbulent flame thickness to laminar flame thickness δt/δu increases faster with pressure, and increases with the fraction of hydrogen in the mixture, leading to higher ratio of turbulent to laminar flame speed. The flame displays smaller structures and higher degree of wrinkling at higher pressure. Final species of CO2 and H2O formation is almost independent of pressure. For intermediate species CO and OH, an increase in pressure at constant volume fraction of hydrogen β leads to a decrease of emission of these species.

Pressures in Tumuli: A Study of Tumuli Formation

NASA Technical Reports Server (NTRS)

Hansen, James E.

2005-01-01

Tumuli form via localized inflation in surface lava flows. These domed features have widths of 10-20 m, lengths of 10-150 m, and heights of 1-9 m. The axial fracture exposes a brittle crust overlying a ductilely deformed layer. The total crustal thickness is typically less than lm. Tumuli are observed on both terrestrial and martian lava flow surfaces, and provide insight on the flow formation processes and rates. Past studies have estimated the inflation pressure using a bending model for a circular, thin elastic plate, assuming small deflection (Rossi and Gudmundson, 1996). This formulation results in unrealistic pressures for some tumuli. We thus examine alternative models, including those with different shapes, bending of the ductile crust, large deflection, plastic deformation, and thick plate bending. Using the thickness of the ductile crust in the equations for thin, circular plates reduces most pressures to reasonable values. Alternative plate shapes do not cause a significant reduction in inflation pressure. Although the large deflection equations should be applicable based on the plate thickness to tumuli height ratios, they give even less realistic pressures. Tumuli with unrealistic pressures appear to have exceeded the critical bending moment, and have relatively thick crusts, requiring thick plate bending models.

The Role of Cosmic-Ray Pressure in Accelerating Galactic Outflows

NASA Astrophysics Data System (ADS)

Simpson, Christine M.; Pakmor, Rüdiger; Marinacci, Federico; Pfrommer, Christoph; Springel, Volker; Glover, Simon C. O.; Clark, Paul C.; Smith, Rowan J.

2016-08-01

We study the formation of galactic outflows from supernova (SN) explosions with the moving-mesh code AREPO in a stratified column of gas with a surface density similar to the Milky Way disk at the solar circle. We compare different simulation models for SN placement and energy feedback, including cosmic rays (CRs), and find that models that place SNe in dense gas and account for CR diffusion are able to drive outflows with similar mass loading as obtained from a random placement of SNe with no CRs. Despite this similarity, CR-driven outflows differ in several other key properties including their overall clumpiness and velocity. Moreover, the forces driving these outflows originate in different sources of pressure, with the CR diffusion model relying on non-thermal pressure gradients to create an outflow driven by internal pressure and the random-placement model depending on kinetic pressure gradients to propel a ballistic outflow. CRs therefore appear to be non-negligible physics in the formation of outflows from the interstellar medium.

THE ROLE OF COSMIC-RAY PRESSURE IN ACCELERATING GALACTIC OUTFLOWS

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

Simpson, Christine M.; Pakmor, Rüdiger; Pfrommer, Christoph

We study the formation of galactic outflows from supernova (SN) explosions with the moving-mesh code AREPO in a stratified column of gas with a surface density similar to the Milky Way disk at the solar circle. We compare different simulation models for SN placement and energy feedback, including cosmic rays (CRs), and find that models that place SNe in dense gas and account for CR diffusion are able to drive outflows with similar mass loading as obtained from a random placement of SNe with no CRs. Despite this similarity, CR-driven outflows differ in several other key properties including their overallmore » clumpiness and velocity. Moreover, the forces driving these outflows originate in different sources of pressure, with the CR diffusion model relying on non-thermal pressure gradients to create an outflow driven by internal pressure and the random-placement model depending on kinetic pressure gradients to propel a ballistic outflow. CRs therefore appear to be non-negligible physics in the formation of outflows from the interstellar medium.« less

Pulmonary edema associated with upper airway obstruction in dogs.

PubMed

Algren, J T; Price, R D; Buchino, J J; Stremel, R W

1993-12-01

In order to evaluate the effect of acute upper airway obstruction upon pulmonary edema (PE) formation, we studied seven dogs that were subjected to inspiratory obstruction for three hours. Hypoxia was avoided by the administration of supplemental oxygen during the study period. Six dogs developed pulmonary vascular congestion, and four developed histologic findings of PE. Inspiratory intrapleural pressure decreased to -28 +/- 4 mmHg in dogs that developed PE and to -23 +/- 2 mmHg in dogs that did not. Transmural pulmonary artery pressure and pulmonary artery wedge pressure did not increase significantly. Central venous pressure during inspiration (CVPi) increased in all dogs, and CVP at end expiration (CVPe) was significantly higher in dogs with PE. Dogs that developed PE experienced a decrease in cardiac output and an increase in systemic vascular resistance. Furthermore, alveolar ventilation declined in dogs with PE, ultimately resulting in ventilatory failure. Pulmonary edema formation was not preceded by an increase in pulmonary vascular pressures but was associated with higher CVP, pulmonary vascular congestion, and hypercarbia.

Implications of bisphosphonate calcium ion depletion interfering with desmosome epithelial seal in osseointegrated implants and pressure ulcers.

PubMed

Touyz, Louis Z G; Afrashtehfar, Kelvin I

2017-09-01

Osteoporosis (OP) is a global bone disease prevalent in aging in humans, especially in older women. Bisphosphonates (BPs) are commonly used as therapy for OP as it influences hard and soft tissues calcium metabolism. Mucosal and dermal ulceration with exposure of underlying bone arises from incomplete epithelial recovery due to reduced desmosome formation deriving from lack of available calcium. Pathological situations such as bisphosphonate-related osteonecrosis of the jaw have been described. This hypothesis states other situations which demand intact functional desmosomes such as healing skin over chronic pressure points leading to pressure ulcers (as well-known as bedsores, pressure sores, pressure injuries, decubitus ulcers), and hemidesmosomes such as epithelial seals in contact with titanium surfaces will have a higher prevalence of breakdown among patients being treated with BPs. This may be proven through the diminished modulation of calcium ions due to BPs, and its effect on the formation of intercellular gap junctions. Copyright © 2017. Published by Elsevier Ltd.

Carbonate formation on Mars: Latest experiments

NASA Technical Reports Server (NTRS)

Stephens, S. K.; Stevenson, D. J.; Rossman, G. R.; Keyser, L. F.

1993-01-01

Laboratory simulations of Martian CO2 storage address whether carbonate formation could have reduced CO2 pressure from a hypothetical greater than 1 bar to the present 7 mbar in less than or equal to 3 to 4 billion years. This problem is addressed with experiments and analysis designed to verify and improve previous kinetic measurements, reaction mechanisms, and product characterizations, with the goal of improving existing models of Martian CO2 history. A sensitive manometer monitored the pressure drop of CO2 due to uptake by powdered silicate for periods of 3 to 100+ days. Pressure drops for diopside 1 and basalt show rapid short-term (approximately one day) CO2 uptake and considerably slower long-term pressure drops. Curves for diopside 2, olivine 1, and olivine 2 are qualitatively similar to those for diopside 1, whereas quartz and plagioclase show near-zero short-term pressure drops and very slow long-term signals, indistinguishable from a leak (less than 10(exp 11) mol/sq m/s).

Investigation of the formation of gaseous sodium sulfate in a doped methane-oxygen flame

NASA Technical Reports Server (NTRS)

Stearns, C. A.; Miller, R. A.; Kohl, F. J.; Fryburg, G. C.

1977-01-01

Na2SO4(g) formation was measured at atmospheric pressure in CH4-O2 flames, with high pressure, free-jet expansion, mass spectrometric sampling used to identify and measure reaction products. Measured composition profiles of reaction products for a doped 9.5 mole ratio O2/CH4 flame are presented. Weight percentages of reactants were 4.7 CH4, 89.0 O2, 3.5 H2O, 2.0 SO2 and 0.35 NaCl.

Atomistic properties of γ uranium.

PubMed

Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

2012-02-22

The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

Atomistic properties of γ uranium

NASA Astrophysics Data System (ADS)

Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

2012-02-01

The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

Role of vortices in growth of microbubbles at mitral mechanical heart valve closure.

PubMed

Rambod, Edmond; Beizai, Masoud; Sahn, David J; Gharib, Morteza

2007-07-01

This study is aimed at refining our understanding of the role of vortex formation at mitral mechanical heart valve (MHV) closure and its association with the high intensity transient signals (HITS) seen in echocardiographic studies with MHV recipients. Previously reported numerical results described a twofold process leading to formation of gas-filled microbubbles in-vitro: (1) nucleation and (2) growth of micron size bubbles. The growth itself consists of two processes: (a) diffusion and (b) sudden pressure drop due to valve closure. The role of diffusion has already been shown to govern the initial growth of nuclei. Pressure drop at mitral MHV closure may be attributed to other phenomena such as squeezed flow, water hammer and primarily, vortex cavitation. Mathematical analysis of vortex formation at mitral MHV closure revealed that a closing velocity of approximately 12 m/s can induce a strong regurgitant vortex which in return can instigate a local pressure drop of about 0.9 atm. A 2D experimental model of regurgitant flows was used to substantiate the impact of vortices. At simulated flow and pressure conditions, a regurgitant vortex was observed to drastically enlarge micron size hydrogen bubbles at its core.

Possible significance of cubic water-ice, H2O-Ic, in the atmospheric water cycle of Mars

NASA Technical Reports Server (NTRS)

Gooding, James L.

1988-01-01

The possible formation and potential significance of the cubic ice polymorph on Mars is discussed. When water-ice crystallizes on Earth, the ambient conditions of temperature and pressure result in the formation of the hexagonal ice polymorph; however, on Mars, the much lower termperature and pressures may permit the crystallization of the cubic polymorph. Cubic ice has two properties of possible importance on Mars: it is an excellant nucleator of other volatiles (such as CO2), and it undergoes an exothermic transition to hexagonal ice at temperatures above 170 K. These properties may have significant implications for both martian cloud formation and the development of the seasonal polar caps.

Early Episodes of High-Pressure Core Formation Preserved in Plume Mantle

NASA Astrophysics Data System (ADS)

Jackson, C. R. M.; Bennett, N. R.; Du, Z.; Cottrell, E.; Fei, Y.

2018-05-01

New experiments demonstrate that xenon isotopes are sensitive to core formation. This behavior may be crucial in explaining the co-occurrence xenon and tungsten anomalies recently observed in plume mantle.

Thin and Flexible Carbon Nanotube-Based Pressure Sensors with Ultra-wide Sensing Range.

PubMed

Doshi, Sagar M; Thostenson, Erik T

2018-06-26

A scalable electrophoretic deposition (EPD) approach is used to create novel thin, flexible and lightweight carbon nanotube-based textile pressure sensors. The pressure sensors can be produced using an extensive variety of natural and synthetic fibers. These piezoresistive sensors are sensitive to pressures ranging from the tactile range (< 10 kPa), in the body weight range (~ 500 kPa), and very high pressures (~40 MPa). The EPD technique enables the creation of a uniform carbon nanotube-based nanocomposite coating, in the range of 250-750 nm thick, of polyethyleneimine (PEI) functionalized carbon nanotubes on non-conductive fibers. In this work, non-woven aramid fibers are coated by EPD onto a backing electrode followed by film formation onto the fibers creating a conductive network. The electrically conductive nanocomposite coating is firmly bonded to the fiber surface and shows piezoresistive electrical/mechanical coupling. The pressure sensor displays a large in-plane change in electrical conductivity with applied out-of-plane pressure. In-plane conductivity change results from fiber/fiber contact as well as the formation of a sponge-like piezoresistive nanocomposite "interphase" between the fibers. The resilience of the nanocomposite interphase enables sensing of high pressures without permanent changes to the sensor response, showing high repeatability.

Cavitation clouds created by shock scattering from bubbles during histotripsy

PubMed Central

Maxwell, Adam D.; Wang, Tzu-Yin; Cain, Charles A.; Fowlkes, J. Brian; Sapozhnikov, Oleg A.; Bailey, Michael R.; Xu, Zhen

2011-01-01

Histotripsy is a therapy that focuses short-duration, high-amplitude pulses of ultrasound to incite a localized cavitation cloud that mechanically breaks down tissue. To investigate the mechanism of cloud formation, high-speed photography was used to observe clouds generated during single histotripsy pulses. Pulses of 5−20 cycles duration were applied to a transparent tissue phantom by a 1-MHz spherically focused transducer. Clouds initiated from single cavitation bubbles that formed during the initial cycles of the pulse, and grew along the acoustic axis opposite the propagation direction. Based on these observations, we hypothesized that clouds form as a result of large negative pressure generated by the backscattering of shockwaves from a single bubble. The positive-pressure phase of the wave inverts upon scattering and superimposes on the incident negative-pressure phase to create this negative pressure and cavitation. The process repeats with each cycle of the incident wave, and the bubble cloud elongates toward the transducer. Finite-amplitude propagation distorts the incident wave such that the peak-positive pressure is much greater than the peak-negative pressure, which exaggerates the effect. The hypothesis was tested with two modified incident waves that maintained negative pressure but reduced the positive pressure amplitude. These waves suppressed cloud formation which supported the hypothesis. PMID:21973343

Effect of pressure fluctuations on Richtmyer-Meshkov coherent structures

NASA Astrophysics Data System (ADS)

Bhowmick, Aklant K.; Abarzhi, Snezhana

2016-11-01

We investigate the formation and evolution of Richtmyer Meshkov bubbles after the passage of a shock wave across a two fluid interface in the presence of pressure fluctuations. The fluids are ideal and incompressible and the pressure fluctuations are scale invariant in space and time, and are modeled by a power law time dependent acceleration field with exponent -2. Solutions indicate sensitivity to pressure fluctuations. In the linear regime, the growth of curvature and bubble velocity is linear. The growth rate is dominated by the initial velocity for weak pressure fluctuations, and by the acceleration term for strong pressure fluctuations. In the non-linear regime, the bubble curvature is constant and the solutions form a one parameter family (parametrized by the bubble curvature). The solutions are shown to be convergent and asymptotically stable. The physical solution (stable fastest growing) is a flat bubble for small pressure fluctuations and a curved bubble for large pressure fluctuations. The velocity field (in the frame of references accounting for the background motion) involves intense motion of the fluids in a vicinity of the interface, effectively no motion of the fluids away from the interfaces, and formation of vortical structures at the interface. The work is supported by the US National Science Foundation.

Effect of pressure fluctuations on Richtmyer-Meshkov coherent structures

NASA Astrophysics Data System (ADS)

Bhowmick, Aklant K.; Abarzhi, Snezhana

2016-10-01

We investigate the formation and evolution of Richtmyer Meshkov bubbles after the passage of a shock wave across a two fluid interface in the presence of pressure fluctuations. The fluids are ideal and incompressible and the pressure fluctuations are scale invariant in space and time, and are modeled by a power law time dependent acceleration field with exponent -2. Solutions indicate sensitivity to pressure fluctuations. In the linear regime, the growth of curvature and bubble velocity is linear. The growth rate is dominated by the initial velocity for weak pressure fluctuations, and by the acceleration term for strong pressure fluctuations. In the non-linear regime, the bubble curvature is constant and the solutions form a one parameter family (parametrized by the bubble curvature). The solutions are shown to be convergent and asymptotically stable. The physical solution (stable fastest growing) is a flat bubble for small pressure fluctuations and a curved bubble for large pressure fluctuations. The velocity field (in the frame of references accounting for the background motion) involves intense motion of the fluids in a vicinity of the interface, effectively no motion of the fluids away from the interfaces, and formation of vortical structures at the interface. The work is supported by the US National Science Foundation.

A Polymer Visualization System with Accurate Heating and Cooling Control and High-Speed Imaging

PubMed Central

Wong, Anson; Guo, Yanting; Park, Chul B.; Zhou, Nan Q.

2015-01-01

A visualization system to observe crystal and bubble formation in polymers under high temperature and pressure has been developed. Using this system, polymer can be subjected to a programmable thermal treatment to simulate the process in high pressure differential scanning calorimetry (HPDSC). With a high-temperature/high-pressure view-cell unit, this system enables in situ observation of crystal formation in semi-crystalline polymers to complement thermal analyses with HPDSC. The high-speed recording capability of the camera not only allows detailed recording of crystal formation, it also enables in situ capture of plastic foaming processes with a high temporal resolution. To demonstrate the system’s capability, crystal formation and foaming processes of polypropylene/carbon dioxide systems were examined. It was observed that crystals nucleated and grew into spherulites, and they grew at faster rates as temperature decreased. This observation agrees with the crystallinity measurement obtained with the HPDSC. Cell nucleation first occurred at crystals’ boundaries due to CO2 exclusion from crystal growth fronts. Subsequently, cells were nucleated around the existing ones due to tensile stresses generated in the constrained amorphous regions between networks of crystals. PMID:25915031

Massive star formation in 100,000 years from turbulent and pressurized molecular clouds.

PubMed

McKee, Christopher F; Tan, Jonathan C

2002-03-07

Massive stars (with mass m* > 8 solar masses Mmiddle dot in circle) are fundamental to the evolution of galaxies, because they produce heavy elements, inject energy into the interstellar medium, and possibly regulate the star formation rate. The individual star formation time, t*f, determines the accretion rate of the star; the value of the former quantity is currently uncertain by many orders of magnitude, leading to other astrophysical questions. For example, the variation of t*f with stellar mass dictates whether massive stars can form simultaneously with low-mass stars in clusters. Here we show that t*f is determined by the conditions in the star's natal cloud, and is typically about 105yr. The corresponding mass accretion rate depends on the pressure within the cloud--which we relate to the gas surface density--and on both the instantaneous and final stellar masses. Characteristic accretion rates are sufficient to overcome radiation pressure from about 100M middle dot in circle protostars, while simultaneously driving intense bipolar gas outflows. The weak dependence of t*f on the final mass of the star allows high- and low-mass star formation to occur nearly simultaneously in clusters.

Features of lymphatic dysfunction in compressed skin tissues - Implications in pressure ulcer aetiology.

PubMed

Gray, Robert J; Voegeli, David; Bader, Dan L

2016-02-01

Impaired lymph formation and clearance has previously been proposed as a contributory factor in the development of pressure ulcers. The present study has been designed to trial fluorescence lymphangiography for establishing how lymphatic function is altered under a clinically relevant form of mechanical loading. Lymph formation and clearance was traced in both forearms by an intradermal injection of indocyanine green (ICG) (50 μl, 0.05%w/v), imaged using a commercial near-infrared fluorescence imaging unit (Fluobeam(®) 800). External uniaxial loading equivalent to a pressure of 60 mmHg was applied for 45 min in one arm using a custom-built indenter. Loading was associated with a decreased frequency of normal directional drainage (DD) of ICG within delineated vessels, both immediately after loading and 45 min thereafter. Loading was also associated with non-directional drainage (NDD) of ICG within the interstitium. Signal intensity within NDD was often greatest at areas of stress concentration, producing a 'halo pattern', corresponding to the rounded edges of the indenter. These results suggest that loading skin with a clinically relevant magnitude of pressure alters both lymph formation and clearance. Further work to quantify impaired clearance under mechanical loading could provide valuable insight into their involvement in the development of pressure ulcers. Copyright © 2016 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

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.

Space shuttle solid rocket booster recovery system definition. Volume 3: SRB water impact loads computer program, user's manual

NASA Technical Reports Server (NTRS)

1973-01-01

This user's manual describes the FORTRAN IV computer program developed to compute the total vertical load, normal concentrated pressure loads, and the center of pressure of typical SRB water impact slapdown pressure distributions specified in the baseline configuration. The program prepares the concentrated pressure load information in punched card format suitable for input to the STAGS computer program. In addition, the program prepares for STAGS input the inertia reacting loads to the slapdown pressure distributions.

The significance of stylolitization and intergranular pressure solution in the formation of pressure compartment seals in the St. Peter Sandstone, Ordovician, Michigan basin

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

Drzewiecki, P.A.; Simo, T.; Moline, G.

1991-03-01

The Middle to Late Ordovician St. Peter Sandstone of the Michigan basin is a fine- to medium-grained quartz sandstone. Extensive stylolitization and intergranular pressure solution have been major factors in reducing the porosity of certain horizons within the St. Peter, resulting in pressure compartmentation of the reservoir. Pressure versus depth data for various Michigan basin wells indicate that the basin contains compartments that are overpressured by as much as 500 psi. Horizons bounding these compartments are often affected by intense stylolitization (or intergranular pressure solution) and quartz cementation and have been correlated with zones of low porosity and permeability ({phi}more » = 0-3%, k = <50 {mu}d). These tight zones can be correlated within single gas fields, and some may extend across the Michigan basin. The St. Peter Sandstone has been buried to depths of about 3,500 m in the central part of the basin and 1,500 m at the margins. Intensely stylolitized zones are found at all depths throughout the basin and do not appear to change in abundance or style with depths. Factors that influence the formation, morphology, and abundance of stylolites in the St. Peter include (1) clay intraclasts, (2) intergranular clay, and (3) fine-grained, feldspar-rich sand. Stylolites also occur at contacts between quartz-cemented and carbonate-cemented zones and within well-cemented sands. Intergranular pressure solution and stylolites may be responsible for the formation of a compartment seal. Understanding their genesis can allow prediction of variations in porosity in Michigan basin well cores.« less

The composite TTG series: evidence for a non-unique tectonic setting for Archaean crustal growth.

NASA Astrophysics Data System (ADS)

Moyen, Jean-François

2010-05-01

The geodynamic context of formation of the Archaean TTG (tonalite-trondhjemite-granodiorite) series, the dominant component of the Archaean continental crust, is a matter of debate. The two end-member models for TTG formation are melting of the basaltic slab in a "hot subduction"; and intra-plate melting of basaltic rocks at the base of thick crust (oceanic plateau?). Both models do however predict strikingly different geothermal gradients, as in the modern Earth a typical subduction gradient is less than 10 °C/km compared to > 25-30 °C/km in the case of plateau melting. Using a large database of published TTG compositions, and filtering it to remove rocks that do not match the definition of TTG, it is possible to show that the TTG series is actually composite and made of a range of geochemically identifiable components that can be referred to as low-, medium- and high-pressure groups. The geochemistry of the low-pressure group (low Al, Na, Sr, relatively high Y and Nb) is consistent with derivation from a plagioclase and garnet- amphibolite; the medium-pressure group was formed in equilibrium with a garnet-rich, plagioclase-poor amphibolite, whereas the high pressure group derived from a rutile bearing eclogite. As the temperature of melting of metamafic rocks is largely independent from pressure, this corresponds to melting along a range of contrasting geothermal gradients. The low pressure group requires gradients of 10-12 °C/km, whereas the gradient required for the low pressure group can be as high as 25—30 °C/km. Regardless of the preferred tectonic model for the Archaean, such a range of gradients requires an equally large range of tectonic sites for the formation of the Archaean continental crust.

Comparative study of the oxidation of NiAl(100) by molecular oxygen and water vapor using ambient-pressure X-ray photoelectron spectroscopy

DOE PAGES

Liu, Qianqian; Qin, Hailang; Boscoboinik, Jorge Anibal; ...

2016-10-11

The oxidation behavior of NiAl(100) by molecular oxygen and water vapor under a near-ambient pressure of 0.2 Torr is monitored using ambient-pressure X-ray photoelectron spectroscopy. O 2 exposure leads to the selective oxidation of Al at temperatures ranging from 40 to 500 °C. By contrast, H 2O exposure results in the selective oxidation of Al at 40 and 200 °C, and increasing the oxidation temperature above 300 °C leads to simultaneous formation of both Al and Ni oxides. Furthermore, these results demonstrate that the O 2 oxidation forms a nearly stoichiometric Al 2O 3 structure that provides improved protection tomore » the metallic substrate by barring the outward diffusion of metals. By contrast, the H 2O oxidation results in the formation of a defective oxide layer that allows outward diffusion of Ni at elevated temperatures for simultaneous NiO formation.« less

Ultralight Axion Dark Matter and Its Impact on Dark Halo Structure in N-body Simulations

NASA Astrophysics Data System (ADS)

Zhang, Jiajun; Sming Tsai, Yue-Lin; Kuo, Jui-Lin; Cheung, Kingman; Chu, Ming-Chung

2018-01-01

Ultralight axion is a dark matter candidate with mass { O }({10}-22){eV} and de Broglie wavelength of order kiloparsec. Such an axion, also called fuzzy dark matter (FDM), thermalizes via gravitational force and forms a Bose–Einstein condensate. Recent studies suggested that the quantum pressure from FDM can significantly affect structure formation in small scales, thus alleviating the so-called “small-scale crisis.” In this paper, we develop a new technique to discretize the quantum pressure and illustrate the interactions among FDM particles in an N-body simulation that accurately simulates the formation of the dark matter halo and its inner structure in the region outside the softening length. In a self-gravitationally bound virialized halo, we find a constant density solitonic core, which is consistent with theoretical prediction. The existence of the solitonic core reveals the nonlinear effect of quantum pressure and impacts structure formation in the FDM model.

Comparative study of the oxidation of NiAl(100) by molecular oxygen and water vapor using ambient-pressure X-ray photoelectron spectroscopy

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

Liu, Qianqian; Qin, Hailang; Boscoboinik, Jorge Anibal

The oxidation behavior of NiAl(100) by molecular oxygen and water vapor under a near-ambient pressure of 0.2 Torr is monitored using ambient-pressure X-ray photoelectron spectroscopy. O 2 exposure leads to the selective oxidation of Al at temperatures ranging from 40 to 500 °C. By contrast, H 2O exposure results in the selective oxidation of Al at 40 and 200 °C, and increasing the oxidation temperature above 300 °C leads to simultaneous formation of both Al and Ni oxides. Furthermore, these results demonstrate that the O 2 oxidation forms a nearly stoichiometric Al 2O 3 structure that provides improved protection tomore » the metallic substrate by barring the outward diffusion of metals. By contrast, the H 2O oxidation results in the formation of a defective oxide layer that allows outward diffusion of Ni at elevated temperatures for simultaneous NiO formation.« less

Pre-Darcy flow in tight and shale formations

NASA Astrophysics Data System (ADS)

Dejam, Morteza; Hassanzadeh, Hassan; Chen, Zhangxin

2017-11-01

There are evidences that the fluid flow in tight and shale formations does not follow Darcy law, which is identified as pre-Darcy flow. Here, the unsteady linear flow of a slightly compressible fluid under the action of pre-Darcy flow is modeled and a generalized Boltzmann transformation technique is used to solve the corresponding highly nonlinear diffusivity equation analytically. The effect of pre-Darcy flow on the pressure diffusion in a homogenous formation is studied in terms of the nonlinear exponent, m, and the threshold pressure gradient, G1. In addition, the pressure gradient, flux, and cumulative production per unit area for different m and G1 are compared with the classical solution of the diffusivity equation based on Darcy flow. Department of Petroleum Engineering in College of Engineering and Applied Science at University of Wyoming and NSERC/AI-EES(AERI)/Foundation CMG and AITF (iCORE) Chairs in Department of Chemical and Petroleum Engineering at University of Calgary.

In-situ visual observation for the formation and dissociation of methane hydrates in porous media by magnetic resonance imaging.

PubMed

Zhao, Jiafei; Lv, Qin; Li, Yanghui; Yang, Mingjun; Liu, Weiguo; Yao, Lei; Wang, Shenglong; Zhang, Yi; Song, Yongchen

2015-05-01

In this work, magnetic resonance imaging (MRI) was employed to observe the in-situ formation and dissociation of methane hydrates in porous media. Methane hydrate was formed in a high-pressure cell with controlled temperature, and then the hydrate was dissociated by thermal injection. The process was photographed by the MRI, and the pressure was recorded. The images confirmed that the direct visual observation was achieved; these were then employed to provide detailed information of the nucleation, growth, and decomposition of the hydrate. Moreover, the saturation of methane hydrate during the dissociation was obtained from the MRI intensity data. Our results showed that the hydrate saturation initially decreased rapidly, and then slowed down; this finding is in line with predictions based only on pressure. The study clearly showed that MRI is a useful technique to investigate the process of methane hydrate formation and dissociation in porous media. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of operational conditions on sludge degradation and organic acids formation in low-critical wet air oxidation.

PubMed

Chung, Jinwook; Lee, Mikyung; Ahn, Jaehwan; Bae, Wookeun; Lee, Yong-Woo; Shim, Hojae

2009-02-15

Wet air oxidation processes are to treat highly concentrated organic compounds including refractory materials, sludge, and night soil, and usually operated at supercritical water conditions of high temperature and pressure. In this study, the effects of operational conditions including temperature, pressure, and oxidant dose on sludge degradation and conversion into subsequent intermediates such as organic acids were investigated at low critical wet oxidation conditions. The reaction time and temperature in the wet air oxidation process was shown an important factor affecting the liquefaction of volatile solids, with more significant effect on the thermal hydrolysis reaction rather than the oxidation reaction. The degradation efficiency of sludge and the formation of organic acids were improved with longer reaction time and higher reaction temperature. For the sludge reduction and the organic acids formation under the wet air oxidation, the optimal conditions for reaction temperature, time, pressure, and oxidant dose were shown approximately 240 degrees C, 30min, 60atm, and 2.0L/min, respectively.

Effect of Saturation Pressure Difference on Metal–Silicide Nanopowder Formation in Thermal Plasma Fabrication

PubMed Central

Shigeta, Masaya; Watanabe, Takayuki

2016-01-01

A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size–composition distribution for a metal–silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal–silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder. PMID:28344300

Periodic nanostructures formed on a poly-methyl methacrylate surface with a femtosecond laser for biocompatibility improvement

NASA Astrophysics Data System (ADS)

Takenaka, Keisuke; Tsukamoto, Masahiro; Sato, Yuji; Ooga, Takahiro; Asai, Satoru; Murai, Kensuke

2018-06-01

Poly(methyl methacrylate) (PMMA) is widely used as a biomaterial. The formation of periodic nanostructures on the surface is necessary to improve the biocompatibility. A method was proposed and developed to form periodic nanostructures on a PMMA surface. A PMMA plate was placed on titanium (Ti) plate, and then the Ti plate was irradiated with a laser through the PMMA plate. We try to effectively produce periodic nanostructures on PMMA with a femtosecond laser at a fundamental wavelength by increasing the contact pressure and using titanium (Ti) plate. The contact pressure between PMMA and Ti required to form a periodic nanostructure is 300 kPa, and for a contact pressure of 2400 kPa, periodic nanostructures are formed in 62% of the laser-irradiated area on the PMMA surface. These results suggest that the formation efficiency of the periodic nanostructure depends on the laser conditions and the contact pressure.

Effect of Saturation Pressure Difference on Metal-Silicide Nanopowder Formation in Thermal Plasma Fabrication.

PubMed

Shigeta, Masaya; Watanabe, Takayuki

2016-03-07

A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size-composition distribution for a metal-silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal-silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder.

Water Vapor Effects on Silica-Forming Ceramics

NASA Technical Reports Server (NTRS)

Opila, E. J.; Greenbauer-Seng, L. (Technical Monitor)

2000-01-01

Silica-forming ceramics such as SiC and Si3N4 are proposed for applications in combustion environments. These environments contain water vapor as a product of combustion. Oxidation of silica-formers is more rapid in water vapor than in oxygen. Parabolic oxidation rates increase with the water vapor partial pressure with a power law exponent value close to one. Molecular water vapor is therefore the mobile species in silica. Rapid oxidation rates and large amounts of gases generated during the oxidation reaction in high water vapor pressures may result in bubble formation in the silica and nonprotective scale formation. It is also shown that silica reacts with water vapor to form Si(OH)4(g). Silica volatility has been modeled using a laminar flow boundary layer controlled reaction equation. Silica volatility depends on the partial pressure of water vapor, the total pressure, and the gas velocity. Simultaneous oxidation and volatilization reactions have been modeled with paralinear kinetics.

Radial Features around Irnini Mons, Venus: Implications for Timing of Regional Compression

NASA Astrophysics Data System (ADS)

Buczkowski, D. L.; McGill, G. E.; Cooke, M. L.

2003-12-01

Flows and other deposits from Irnini Mons are superimposed on an older, regional plains material. Wrinkle ridges are generally abundant on this regional plains material and are present in at least two sets: one trending east-west and another concentric to Irnini Mons. Radial features on top of the Irnini flows are mapped as lineations or grabens, as resolution allows. High resolution mapping at 75 m/pixel also reveals ridges radial to Irnini Mons on top of the Irnini flows. These radial ridges are located from approximately N60E to N75E. Radial grabens around a volcano have been explained mathematically, with the magma chamber of a volcano simplistically described as a pressurized hole in an elastic plate. However, magma pressure alone can not explain the presence of radial ridges. The regional east-west trending wrinkle ridges imply a regional north-south compression affecting the Irnini Mons area. The regional stress field around an empty hole in an elastic plate is perturbed close to the hole, although it remains unperturbed at infinity; the change in material properties from the surrounding rock to a magma-filled chamber allows us to consider the chamber as "soft" and thus effectively empty. The perturbation of a uniaxial regional compressive stress around a pressurized hole is such that at angles of 90 and 270 degrees (east-west) the maximum principal stresses close to the hole are compressive, while at angles 0 and 180 degrees (north-south) the maximum principal stresses are tensile. The angle at which maximum principal stresses change from tension to compression depends upon the distance from the hole and the relative magnitudes of magma pressure and the regional compression. While in the simple model resultant stresses would be symmetric around the hole, structural complexities to the south and west of Irnini Mons restrict the predicted pattern of radial ridges as well as grabens to the region northeast of the volcano. Thus, the existence of radial ridges on the Irnini flows implies that the regional north-south compression that caused the east-west trending wrinkle ridges was still active during the formation of Irnini Mons. A rough timeline for events in the region could be: 1) formation of east-west wrinkle ridges on regional plains, 2) formation of graben radial to Irnini due to magma pressure coeval with formation of radial ridges due to a combination of magma pressure and ongoing regional compression, 3) cessation of magma pressure and formation of concentric grabens, and 4) formation of concentric wrinkle ridges, perhaps due to gravitational relaxation of the topographic rise.

Abnormal pressure study in the Malay and Penyu Basins: A regional understanding

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

Kader, M.S.; Leslie, W.

1994-07-01

A majority of wells drilled in the Malay and Penyu basins were terminated due to abnormal pressure. Blowouts and the subsequent loss of technical data have always been a concern during drilling operations. This study employs data from 94 exploratory wells spread throughout the Malay and Penyu basins. The postdrill abnormal pressure predictive method used is pressure vs. depth plots of data obtained from Repeat Formation tester (RFT) readings. The study results indicate that abnormal pressure occurs in a progressively older stratigraphic unit toward the basin margins. The margins of the Malay and the entire Penyu basins tend to bemore » normally pressured. The onset of abnormal pressure appears to be abrupt in the northern portion and more gradual in the southern part of the Malay Basin. Abnormal pressure in the Malay Basin is found to be neither depth dependent nor age related. Many factors can cause the abnormal formation pressures. In some areas, a combination of factors prevails. Rapid deposition of the middle to late Miocene siliciclastic sediments appears to be a dominant cause particularly in the center of the Malay Basin. A low sand:shale ratio coupled with a high geothermal gradient is also found to be a local cause near the axis of the basin. This phenomenon is crucial to the understanding of hydrocarbon migration and will enable the planning of safe and efficient drilling campaigns.« less

High Pressure/Temperature Metal Silicate Partitioning of Tungsten

NASA Technical Reports Server (NTRS)

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

2010-01-01

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

Stochastic Approach to Determine CO2 Hydrate Induction Time in Clay Mineral Suspensions

NASA Astrophysics Data System (ADS)

Lee, K.; Lee, S.; Lee, W.

2008-12-01

A large number of induction time data for carbon dioxide hydrate formation were obtained from a batch reactor consisting of four independent reaction cells. Using resistance temperature detector(RTD)s and a digital microscope, we successfully monitored the whole process of hydrate formation (i.e., nucleation and crystal growth) and detected the induction time. The experiments were carried out in kaolinite and montmorillonite suspensions at temperatures between 274 and 277 K and pressures ranging from 3.0 to 4.0 MPa. Each set of data was analyzed beforehand whether to be treated by stochastic manner or not. Geochemical factors potentially influencing the hydrate induction time under different experimental conditions were investigated by stochastic analyses. We observed that clay mineral type, pressure, and temperature significantly affect the stochastic behavior of the induction times for CO2 hydrate formation in this study. The hydrate formation kinetics along with stochastic analyses can provide basic understanding for CO2 hydrate storage in deep-sea sediment and geologic formation, securing its stability under the environments.

Simulated formation and flow of microemulsions during surfactant flushing of contaminated soil.

PubMed

Ouyan, Ying; Cho, Jong Soo; Mansell, Robert S

2002-01-01

Contamination of groundwater resources by non-aqueous phase liquids (NAPLs) has become an issue of increasing environmental concern. This study investigated the formation and flow of microemulsions during surfactant flushing of NAPL-contaminated soil using the finite difference model UTCHEM, which was verified with our laboratory experimental data. Simulation results showed that surfactant flushing of NAPLs (i.e., trichloroethylene and tetrachloroethylene) from the contaminated soils was an emulsion-driven process. Formation of NAPL-in-water microemulsions facilitated the removal of NAPLs from contaminated soils. Changes in soil saturation pressure were used to monitor the mobilization and entrapment of NAPLs during surface flushing process. In general, more NAPLs were clogged in soil pores when the soil saturation pressure increased. Effects of aquifer salinity on the formation and flow of NAPL-in-water microemulsions were significant. This study suggests that the formation and flow of NAPL-in-water microemulsions through aquifer systems are complex physical-chemical phenomena that are critical to effective surfactant flushing of contaminated soils.

Depletion of potassium and sodium in mantles of Mars, Moon and Vesta by core formation.

PubMed

Steenstra, E S; Agmon, N; Berndt, J; Klemme, S; Matveev, S; van Westrenen, W

2018-05-04

The depletions of potassium (K) and sodium (Na) in samples from planetary interiors have long been considered as primary evidence for their volatile behavior during planetary formation processes. Here, we use high-pressure experiments combined with laser ablation analyses to measure the sulfide-silicate and metal-silicate partitioning of K and Na at high pressure (P) - temperature (T) and find that their partitioning into metal strongly increases with temperature. Results indicate that the observed Vestan and Martian mantle K and Na depletions can reflect sequestration into their sulfur-rich cores in addition to their volatility during formation of Mars and Vesta. This suggests that alkali depletions are not affected solely by incomplete condensation or partial volatilization during planetary formation and differentiation, but additionally or even primarily reflect the thermal and chemical conditions during core formation. Core sequestration is also significant for the Moon, but lunar mantle depletions of K and Na cannot be reconciled by core formation only. This supports the hypothesis that measured isotopic fractionations of K in lunar samples represent incomplete condensation or extensive volatile loss during the Moon-forming giant impact.

Investigating Created Properties of Nanoparticles Based Drilling Mud

NASA Astrophysics Data System (ADS)

Ghasemi, Nahid; Mirzaee, Mojtaba; Aghayari, Reza; Maddah, Heydar

2018-05-01

The success of drilling operations is heavily dependent on the drilling fluid. Drilling fluids cool down and lubricate the drill bit, remove cuttings, prevent formation damage, suspend cuttings and also cake off the permeable formation, thus retarding the passage of fluid into the formation. Typical micro or macro sized loss circulation materials (LCM) show limited success, especially in formations dominated by micropores, due to their relatively large sizes. Due to unique characteristics of nanoparticles such as their size and high surface area to volume ratio, they play an effective role in solving problems associated with the drilling fluid. In this study, we investigate the effect of adding Al2O3 and TiO2 nanoparticles into the drilling mud. Al2O3 and TiO2 nanoparticles were used in 20 and 60 nm of size and 0.05 wt% in concentration. Investigating the effects of temperature and pressure has shown that an increase in temperature can reduce the drilling mud rheological properties such as plastic viscosity, while an increase in pressure can enhance these properties. Also, the effects of pressure in high temperatures were less than those in low temperatures. Studying the effects of adding nanoparticles has shown that they can reduce the drilling mud rheological properties. Moreover, they can increase gel strength, reduce capillary suction time and decrease formation damage.

Jet formation of SF6 bubble induced by incident and reflected shock waves

NASA Astrophysics Data System (ADS)

Zhu, Yuejin; Yu, Lei; Pan, Jianfeng; Pan, Zhenhua; Zhang, Penggang

2017-12-01

The computational results of two different cases on the evolution of the shock-SF6 heavy bubble interaction are presented. The shock focusing processes and jet formation mechanisms are analyzed by using the high resolution of computation schemes, and the influence of reflected shock waves is also investigated. It is concluded that there are two steps in the shock focusing process behind the incident shock wave, and the density and pressure values increase distinctly when the shock focusing process is completed. The local high pressure and vorticities in the vicinity of the downstream pole can propel the formation of the jet behind the incident shock wave. In addition, the gas is with the rightward velocity before the reflected shock wave impinges on the bubble; therefore, the evolutions of the waves and the bubble are more complicated when the reflected shock wave impinges on the SF6 bubble. Furthermore, the different end wall distances would affect the deformation degree of the bubble before the interaction of the reflected shock wave; therefore, the different left jet formation processes are found after the impingement of reflected shock waves when L = 27 mm. The local high pressure zones in the vicinity of the left bubble interface and the impingement of different shock waves can induce the local gas to shift the rightward velocity to the leftward velocity, which can further promote the formation of jets.

Metal-Silicate Partitioning of Various Siderophile Elements at High Pressure and High Temperatures: a Diamond Anvil Cell Study

NASA Astrophysics Data System (ADS)

Badro, J.; Blanchard, I.; Siebert, J.

2015-12-01

Core formation is the major chemical fractionation that occurred on Earth. This event is widely believed to have happened at pressures of at least 40 GPa and temperatures exceeding 3000 K. It has left a significant imprint on the chemistry of the mantle by removing most of the siderophile (iron-loving) elements from it. Abundances of most siderophile elements in the bulk silicate Earth are significantly different than those predicted from experiments at low P-T. Among them, vanadium, chromium, cobalt and gallium are four siderophile elements which abundances in the mantle have been marked by core formation processes. Thus, understand their respective abundance in the mantle can help bringing constraints on the conditions of Earth's differentiation. We performed high-pressure high-temperature experiments using laser heating diamond anvil cell to investigate the metal-silicate partitioning of those four elements. Homogeneous glasses doped in vanadium, chromium, cobalt and gallium were synthesized using a levitation furnace and load inside the diamond anvil cell along with metallic powder. Samples were recovered using a Focused Ion Beam and chemically analyzed using an electron microprobe. We investigate the effect of pressure, temperature and metal composition on the metal-silicate partitioning of V, Cr, Co and Ga. Three previous studies focused on V, Cr and Co partitioning at those conditions of pressure and temperature, but none explore gallium partitioning at the relevant extreme conditions of core formation. We will present the first measurements of gallium metal-silicate partitioning performed at the appropriate conditions of pressure and temperature of Earth's differentiation.

Formation of Gradient Structures in the Zone of Joining a Deformable Nickel Alloy and a Single-Crystal Intermetallic Alloy during Thermodiffusion Pressure Welding and Subsequent Heat Treatment

NASA Astrophysics Data System (ADS)

Povarova, K. B.; Valitov, V. A.; Drozdov, A. A.; Bazyleva, O. A.; Galieva, E. V.; Arginbaeva, E. G.

2018-01-01

The possibility of formation of a high-quality solid-phase joint of an Ni3Al-based single-crystal intermetallic VKNA-25 blade alloy with a high-temperature deformable EP975 disk alloy by pressure welding is studied to create high-performance one-piece blisk unit for the next-generation aviation gas turbine engines and to decrease the unit mass. The influence of the conditions of thermodiffusion pressure welding under the hightemperature superplasticity of the disk alloy and the influence of heat treatment of welded joints on the gradient structures in the welded joint zone and the structure at the periphery of the welded samples are investigated.

Asteroid entry in Venusian atmosphere: Pressure and density fields effect on crater formation

NASA Technical Reports Server (NTRS)

Schmidt, Robert

1995-01-01

The objectives are to look at time scales of overpressure compared to cratering and to determine: what are the transient pressure and density due to atmospheric entry; do shock waves evacuate ambient gas; do transient atmospheric disturbances 'settle down' during cratering; can the pressure/density field be approximated as quasi-static; how does disturbance scale with impactor size; and what is the role of atmospheric thickness. The general approach is to perform inexpensive exploratory calculations, perform experiments to validate code and observe crater growth, and to follow up with more realistic coupling calculations. This viewgraph presentation presents progress made with the objective to obtain useful scaling relationships for crater formation when atmospheric effects are important.

Analysis of high injection pressure and ambient temperature on biodiesel spray characteristics using computational fluid dynamics

NASA Astrophysics Data System (ADS)

Hashim, Akasha; Khalid, Amir; Jaat, Norrizam; Sapit, Azwan; Razali, Azahari; Nizam, Akmal

2017-09-01

Efficiency of combustion engines are highly affected by the formation of air-fuel mixture prior to ignition and combustion process. This research investigate the mixture formation and spray characteristics of biodiesel blends under variant in high ambient and injection conditions using Computational Fluid Dynamics (CFD). The spray characteristics such as spray penetration length, spray angle and fluid flow were observe under various operating conditions. Results show that increase in injection pressure increases the spray penetration length for both biodiesel and diesel. Results also indicate that higher spray angle of biodiesel can be seen as the injection pressure increases. This study concludes that spray characteristics of biodiesel blend is greatly affected by the injection and ambient conditions.

Mössbauer analysis of the magnetic structure of a high-carbon austenitic steel upon deformation and under pressure

NASA Astrophysics Data System (ADS)

Shabashov, V. A.; Korshunov, L. G.; Zamatovskii, A. E.; Litvinov, A. V.

2007-10-01

A large plastic deformation of Hadfield steel (frictional action, shear under pressure, filing, and rolling) leads to the growth of an internal effective field at 57Fe nuclei, magnetic-degeneracy removal in the spectra, and delay of the paraprocess up to room temperature. In the Mössbauer spectrum of the 120G13 Hadfield steel, the reversible formation of a hyperfine structure, which is supposedly connected with magnetic ordering, has been detected in situ upon quasi-hydrostatic compression to 26 GPa. The observed growth of magnetic characteristics upon deformation and under high pressure is explained by the deformation-induced redistribution of carbon with the formation of short-range ordering of oxygen and manganese.

Results of hydrologic tests and water-chemistry analyses, wells H-5A, H-5B, and H-5C, at the proposed Waste Isolation Pilot Plant site, southeastern New Mexico

USGS Publications Warehouse

Dennehy, Kevin F.; Mercer, Jerry W.

1982-01-01

Data were collected during hydrologic testing at wells H-5A, H-5B, and H-5C in the northeastern part of the proposed Waste Isolation Pilot Plant site in southeastern New Mexico. The three water-bearing zones tested, the Magenta and Culebra Dolomite Members of the Rustler Formation and the Rustler Formation-Salado Formation contact, yield water to wells at rates less than 0.6 gallon per minute. Throughout the testing, water-pressure response in the tested zone was monitored by a pressure-transducer system. Shut-in and slug tests were conducted to acquire data. Water samples from the Magenta Dolomite Member, Culebra Dolomite Member, and Rustler Formation-Salado Formation contact had dissolved-solids concentrations of 6,090, 144,000, and 412,000 milligrams per liter, respectively. The major chemical constituents of water samples from the Magenta Dolomite Member were sodium and sulfate; from the Culebra Dolomite Member, sodium and chloride; and from the Rustler Formation-Salado Formation contact, magnesium, and chloride. Radium-226, a naturally occurring radioactive element, was present in samples from all three zones. (USGS)

Process for treating earth formations to be relatively inpermeable to formation water

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

Peacock, D.W.

1966-12-13

In a method for treatment of earth formations to make them relatively impermeable to formation water, high pH water is introduced through the bore into the formation under sufficient pressure to force the formation water out of the formation being treated. Thereafter, a high pH additive solution is introduced into the formation through the well bore. The pH of the additive solution is lowered in situ to precipitate the additive in the formation, thus shutting off the flow of water from the formation into the well. The additive is a tannin obtained from flavotannins, gallotannins, and mixed tannins. (7 claims)

Disruption of Giant Molecular Clouds by Massive Star Clusters

NASA Astrophysics Data System (ADS)

Harper-Clark, Elizabeth

The lifetime of a Giant Molecular Cloud (GMC) and the total mass of stars that form within it are crucial to the understanding of star formation rates across a whole galaxy. In particular, the stars within a GMC may dictate its disruption and the quenching of further star formation. Indeed, observations show that the Milky Way contains GMCs with extensive expanding bubbles while the most massive stars are still alive. Simulating entire GMCs is challenging, due to the large variety of physics that needs to be included, and the computational power required to accurately simulate a GMC over tens of millions of years. Using the radiative-magneto-hydrodynamic code Enzo, I have run many simulations of GMCs. I obtain robust results for the fraction of gas converted into stars and the lifetimes of the GMCs: (A) In simulations with no stellar outputs (or "feedback''), clusters form at a rate of 30% of GMC mass per free fall time; the GMCs were not disrupted but contained forming stars. (B) Including ionization gas pressure or radiation pressure into the simulations, both separately and together, the star formation was quenched at between 5% and 21% of the original GMC mass. The clouds were fully disrupted within two dynamical times after the first cluster formed. The radiation pressure contributed the most to the disruption of the GMC and fully quenched star formation even without ionization. (C) Simulations that included supernovae showed that they are not dynamically important to GMC disruption and have only minor effects on subsequent star formation. (D) The inclusion of a few micro Gauss magnetic field across the cloud slightly reduced the star formation rate but accelerated GMC disruption by reducing bubble shell disruption and leaking. These simulations show that new born stars quench further star formation and completely disrupt the parent GMC. The low star formation rate and the short lifetimes of GMCs shown here can explain the low star formation rate across the whole galaxy.

INSIDE-OUT PLANET FORMATION. III. PLANET–DISK INTERACTION AT THE DEAD ZONE INNER BOUNDARY

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

Hu, Xiao; Tan, Jonathan C.; Chatterjee, Sourav

The Kepler mission has discovered more than 4000 exoplanet candidates. Many of them are in systems with tightly packed inner planets. Inside-out planet formation (IOPF) has been proposed as a scenario to explain these systems. It involves sequential in situ planet formation at the local pressure maximum of a retreating dead zone inner boundary (DZIB). Pebbles accumulate at this pressure trap, which builds up a pebble ring and then a planet. The planet is expected to grow in mass until it opens a gap, which helps to both truncate pebble accretion and also induce DZIB retreat that sets the location ofmore » formation of the next planet. This simple scenario may be modified if the planet undergoes significant migration from its formation location. Thus, planet–disk interactions play a crucial role in the IOPF scenario. Here we present numerical simulations that first assess the degree of migration for planets of various masses that are forming at the DZIB of an active accretion disk, where the effective viscosity is undergoing a rapid increase in the radially inward direction. We find that torques exerted on the planet by the disk tend to trap the planet at a location very close to the initial pressure maximum where it formed. We then study gap opening by these planets to assess at what mass a significant gap is created. Finally, we present a simple model for DZIB retreat due to penetration of X-rays from the star to the disk midplane. Overall, these simulations help to quantify both the mass scale of first (“Vulcan”) planet formation and the orbital separation to the location of second planet formation.« less

Inside-out Planet Formation. III. Planet-Disk Interaction at the Dead Zone Inner Boundary

NASA Astrophysics Data System (ADS)

Hu, Xiao; Zhu, Zhaohuan; Tan, Jonathan C.; Chatterjee, Sourav

2016-01-01

The Kepler mission has discovered more than 4000 exoplanet candidates. Many of them are in systems with tightly packed inner planets. Inside-out planet formation (IOPF) has been proposed as a scenario to explain these systems. It involves sequential in situ planet formation at the local pressure maximum of a retreating dead zone inner boundary (DZIB). Pebbles accumulate at this pressure trap, which builds up a pebble ring and then a planet. The planet is expected to grow in mass until it opens a gap, which helps to both truncate pebble accretion and also induce DZIB retreat that sets the location of formation of the next planet. This simple scenario may be modified if the planet undergoes significant migration from its formation location. Thus, planet-disk interactions play a crucial role in the IOPF scenario. Here we present numerical simulations that first assess the degree of migration for planets of various masses that are forming at the DZIB of an active accretion disk, where the effective viscosity is undergoing a rapid increase in the radially inward direction. We find that torques exerted on the planet by the disk tend to trap the planet at a location very close to the initial pressure maximum where it formed. We then study gap opening by these planets to assess at what mass a significant gap is created. Finally, we present a simple model for DZIB retreat due to penetration of X-rays from the star to the disk midplane. Overall, these simulations help to quantify both the mass scale of first (“Vulcan”) planet formation and the orbital separation to the location of second planet formation.

Hydrologic and water-chemistry data from the Cretaceous-aquifers test well (BFT-2055), Beaufort County, South Carolina

USGS Publications Warehouse

Landmeyer, J.E.; Bradley, P.M.

1998-01-01

Test well BFT-2055 was drilled through the entire thickness of Coastal Plain sediments beneath central Hilton Head Island, South Carolina, and terminated in bedrock at a depth of 3833 feet. The well was drilled to evaluate the hydraulic properties of the Cretaceous formations beneath Hilton Head Island as a potential source of supplemental water to supplies currently withdrawn from the Upper Floridan aquifer. The intervals tested include sediments of the Cape Fear and Middendorf Formations. Results from aquifer tests indicate that the transmissivity of the formations screened ranges from 1300 to 3000 feet squared per day and an average hydraulic conductivity of about 15 feet per day. Formation-fluid pressure tests indicate that the potential exists for upward ground-water flow from higher fluid pressures in the deeper Cape Fear and Middendorf Formations to lower fluid pressures in the Black Creek Formation and shallower units. A flowmeter test indicated that greater than 75 percent of the natural, unpumped flow in the well is from the screened intervals no deeper than 3100 feet. Water-chemistry analyses indicate that the water sampled from the Middendorf and Cape Fear has about 1450 milligrams per liter dissolved solids, 310 to 1000 milligrams per liter sodium, and 144 to 1600 milligrams per liter chloride. Because these chloride concentrations would render water pumped from these aquifers as nonpotable, it is unlikely that these aquifers will be used as a supplemental source of water for island residents without some form of pretreatment. Similar chloride concentrations are present in some wells in the Upper Floridan aquifer adjacent to Port Royal Sound, and these chloride concentrations were the primary reason for drilling the test well in the Cretaceous formations as a possible source of more potable water.

Hydrothermal formation of tobermorite studied by in situ X-ray diffraction under autoclave condition.

PubMed

Kikuma, Jun; Tsunashima, Masamichi; Ishikawa, Tetsuji; Matsuno, Shin-ya; Ogawa, Akihiro; Matsui, Kunio; Sato, Masugu

2009-09-01

Hydrothermal formation of tobermorite from a pre-cured cake has been investigated by transmission X-ray diffraction (XRD) using high-energy X-rays from a synchrotron radiation source in combination with a newly designed autoclave cell. The autoclave cell has a large and thin beryllium window for wide-angle X-ray diffraction; nevertheless, it withstands a steam pressure of more than 1.2 MPa, which enables in situ XRD measurements in a temperature range of 373 to 463 K under a saturated steam pressure. Formation and/or decomposition of several components has been successfully observed during 7.5 h of reaction time. From the intensity changes of the intermediate materials, namely non-crystalline C-S-H and hydroxylellestadite, two pathways for tobermorite formation have been confirmed. Thus, the newly developed autoclave cell can be used for the analyses of reaction mechanisms under specific atmospheres and temperatures.

A PDMS-Based Microfluidic Hanging Drop Chip for Embryoid Body Formation.

PubMed

Wu, Huei-Wen; Hsiao, Yi-Hsing; Chen, Chih-Chen; Yet, Shaw-Fang; Hsu, Chia-Hsien

2016-07-06

The conventional hanging drop technique is the most widely used method for embryoid body (EB) formation. However, this method is labor intensive and limited by the difficulty in exchanging the medium. Here, we report a microfluidic chip-based approach for high-throughput formation of EBs. The device consists of microfluidic channels with 6 × 12 opening wells in PDMS supported by a glass substrate. The PDMS channels were fabricated by replicating polydimethyl-siloxane (PDMS) from SU-8 mold. The droplet formation in the chip was tested with different hydrostatic pressures to obtain optimal operation pressures for the wells with 1000 μm diameter openings. The droplets formed at the opening wells were used to culture mouse embryonic stem cells which could subsequently developed into EBs in the hanging droplets. This device also allows for medium exchange of the hanging droplets making it possible to perform immunochemistry staining and characterize EBs on chip.

Self-regulating galaxy formation. Part 1: HII disk and Lyman alpha pressure

NASA Technical Reports Server (NTRS)

Cox, D. P.

1983-01-01

Assuming a simple but physically based prototype for behavior of interstellar material during formation of a disk galaxy, coupled with the lowest order description of infall, a scenario is developed for self-regulated disk galaxy formation. Radiation pressure, particularly that of Lyman depha (from fluorescence conversion Lyman continuum), is an essential component, maintaining an inflated disk and stopping infall when only a small fraction of the overall perturbation has joined the disk. The resulting galaxies consist of a two dimensional family whose typical scales and surface density are expressable in terms of fundamental constants. The model leads naturally to galaxies with a rich circumgalactic environment and flat rotation curves (but is weak in its analysis of the subsequent evolution of halo material).

Method for directional hydraulic fracturing

DOEpatents

Swanson, David E.; Daly, Daniel W.

1994-01-01

A method for directional hydraulic fracturing using borehole seals to confine pressurized fluid in planar permeable regions, comprising: placing a sealant in the hole of a structure selected from geologic or cemented formations to fill the space between a permeable planar component and the geologic or cemented formation in the vicinity of the permeable planar component; making a hydraulic connection between the permeable planar component and a pump; permitting the sealant to cure and thereby provide both mechanical and hydraulic confinement to the permeable planar component; and pumping a fluid from the pump into the permeable planar component to internally pressurize the permeable planar component to initiate a fracture in the formation, the fracture being disposed in the same orientation as the permeable planar component.

Potential for deep basin-centered gas accumulation in Hanna Basin, Wyoming

USGS Publications Warehouse

Wilson, Michael S.; Dyman, Thaddeus S.; Nuccio, Vito F.

2001-01-01

The potential for a continuous-type basin-centered gas accumulation in the Hanna Basin in Carbon County, Wyoming, is evaluated using geologic and production data including mud-weight, hydrocarbon-show, formation-test, bottom-hole-temperature, and vitrinite reflectance data from 29 exploratory wells. This limited data set supports the presence of a hypothetical basin-centered gas play in the Hanna Basin. Two generalized structural cross sections illustrate our interpretations of possible abnormally pressured compartments. Data indicate that a gas-charged, overpressured interval may occur within the Cretaceous Mowry, Frontier, and Niobrara Formations at depths below 10,000 ft along the southern and western margins of the basin. Overpressuring may also occur near the basin center within the Steele Shale and lower Mesaverde Group section at depths below 18,000 to 20,000 ft. However, the deepest wells drilled to date (12,000 to 15,300 ft) have not encountered over-pressure in the basin center. This overpressured zone is likely to be relatively small (probably 20 to 25 miles in diameter) and is probably depleted of gas near major basement reverse faults and outcrops where gas may have escaped. Water may have invaded reservoirs through outcrops and fracture zones along the basin margins, creating an extensive normally pressured zone. A zone of subnormal pressure also may exist below the water-saturated, normal-pressure zone and above the central zone of overpressure. Subnormal pressures have been interpreted in the center of the Hanna Basin at depths ranging from 10,000 to 25,000 ft based on indirect evidence including lost-circulation zones. Three wells on the south side of the basin, where the top of the subnormally pressured zone is interpreted to cut across stratigraphic boundaries, tested the Niobrara Formation and recovered gas and oil shows with very low shut-in pressures.

Evolution of the Active Phase of CoMo/Al2O3 Catalysts under Industrial Conditions: a High-Pressure MES Study

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

Dugulan, A.I.; Overweg, A.R.; Craje, M.W.J.

2005-04-26

The behavior of CoMo/Al2O3 catalysts sulfided in H2S/H2 gas mixture, under industrial conditions, was investigated using Moessbauer emission spectroscopy (MES). An intermediate Co-Mo phase is formed after increasing the sulfidation pressure to 4 MPa, favoring the Co-Mo-S phase formation. An increase in the quadrupole splitting value of the Co-sulfide species after treatment at 573 K is proposed as a prerequisite for the formation of ideal Co-Mo-S structures.

Procesos físicos en mezclas gaseosas

NASA Astrophysics Data System (ADS)

Milone, L. A.; Merlo, D. C.

In gaseous mixtures of different compositions (solar, metal poor, Helium-rich and Helium metal poor), we analyze chemical abundances (free electrons, neutral atoms, ions, negative ions and moleculae) as function of temperature and electronic pressures. At relative lower temperatures and higher electronic pressures, we obtain unreachable physical conditions if molecular formation of H2 and C2 are not included (the relations log (Pg) vs log (Pe) tend to infinite); this divergence disappears if molecular formation is taken into account. Finally, we analyze and explain the causes of this phenomena using accuracy numerical calculations.

Comprehensive database of wellbore temperatures and drilling mud weight pressures by depth for Judge Digby field, Louisiana

USGS Publications Warehouse

Burke, Lauri

2010-01-01

This document serves as the repository for the unprocessed data used in the investigation of temperature and overpressure relations within the deep Tuscaloosa Formation in Judge Digby field. It is a compilation of all the publicly accessible wellbore temperature and pressure data for Judge Digby field, a prolific natural gas field producing from the Upper Cretaceous lower part of the Tuscaloosa Formation in the Gulf Coast region. This natural gas field is in Pointe Coupee Parish in the southern part of onshore Louisiana.

Laminar Soot Processes (Lsp) Experiment: Findings From Ground-Based Measurements

NASA Technical Reports Server (NTRS)

Kim, C. H.; El-Leathy, A. M.; Faeth, G. M.; Xu, F.

2003-01-01

Processes of soot formation and oxidation must be understood in order to achieve reliable computational combustion calculations for nonpremixed (diffusion) flames involving hydrocarbon fuels. Motivated by this observation, the present investigation extended earlier work on soot formation and oxidation in laminar jet ethylene/air and methane/oxygen premixed and acetylene-nitrogen/air diffusion flames at atmospheric pressure in this laboratory, emphasizing soot surface growth and early soot surface oxidation in laminar diffusion flames fueled with a variety of hydrocarbons at pressures in the range 0.1 - 1.0 atm.

CO.sub.2 Pretreatment prevents calcium carbonate formation

DOEpatents

Neavel, Richard C.; Brunson, Roy J.; Chaback, Joseph J.

1980-01-01

Scale formation during the liquefaction of lower ranking coals and similar carbonaceous materials is significantly reduced and/or prevented by pretreatment with carbon dioxide. The carbon dioxide pretreatment is believed to convert the scale-forming components to the corresponding carbonate prior to liquefaction. The pretreatment is accomplished at a total pressure within the range from about 14 to about 68 atmospheres and a carbon dioxide partial pressure within the range from about 14 to about 34 atmospheres. Temperature during pretreatment will generally be within the range from about 100.degree. to about 200.degree. C.

Method for carbon dioxide sequestration

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

Wang, Yifeng; Bryan, Charles R.; Dewers, Thomas

A method for geo-sequestration of a carbon dioxide includes selection of a target water-laden geological formation with low-permeability interbeds, providing an injection well into the formation and injecting supercritical carbon dioxide (SC-CO.sub.2) and water or bine into the injection well under conditions of temperature, pressure and density selected to cause the fluid to enter the formation and splinter and/or form immobilized ganglia within the formation.

Implications of Peer Pressure for Adolescent Nursing Research: A Concept Analysis Approach.

PubMed

Pittman, Alison F

2018-01-02

The influence of peers is widely held as a significant factor in child and adolescent development. As health care providers seek ways to improve the health of children and adolescents, peer pressure must be examined. This article analyzes peer pressure and its relationship to the health of children and adolescents. Defining attributes of peer pressure are discussed, including incomplete identity formation, the presence of a peer influence, and a need for approval. Antecedents and consequences of peer pressure are also explored. Methods of measuring peer pressure are discussed, along with implications for health care research in the pediatric population.

Microbial activity at gigapascal pressures.

PubMed

Sharma, Anurag; Scott, James H; Cody, George D; Fogel, Marilyn L; Hazen, Robert M; Hemley, Russell J; Huntress, Wesley T

2002-02-22

We observed physiological and metabolic activity of Shewanella oneidensis strain MR1 and Escherichia coli strain MG1655 at pressures of 68 to 1680 megapascals (MPa) in diamond anvil cells. We measured biological formate oxidation at high pressures (68 to 1060 MPa). At pressures of 1200 to 1600 MPa, living bacteria resided in fluid inclusions in ice-VI crystals and continued to be viable upon subsequent release to ambient pressures (0.1 MPa). Evidence of microbial viability and activity at these extreme pressures expands by an order of magnitude the range of conditions representing the habitable zone in the solar system.

Microstructural characteristics of Hadfield steel solidified under high pressure

NASA Astrophysics Data System (ADS)

Zhang, Yuzi; Li, Yanguo; Han, Bo; Zhang, Fucheng; Qian, Lihe

2011-12-01

Samples of Hadfield steel, high manganese austenite steel with 13 wt% manganese and 1.2 wt% carbon, were solidified under a pressure of 6 GPa. The microstructures of the samples were analyzed by metallography and X-ray diffraction. The results indicate that the solidification microstructure of the Hadfield steel was remarkably refined under high pressure. Additionally, the carbide of M23C6 was obtained in the Hadfield steel solidified under high pressure was different from the carbide of M3C obtained by solidification under normal pressure. Furthermore, high pressure promoted the formation of orientational solidified microstructure of the Hadfield steel.

Evidence of preorganization in quinonoid intermediate formation from L-Trp in H463F mutant Escherichia coli tryptophan indole-lyase from effects of pressure and pH.

PubMed

Phillips, Robert S; Kalu, Ukoha; Hay, Sam

2012-08-21

The effects of pH and hydrostatic pressure on the reaction of H463F tryptophan indole-lyase (TIL) have been evaluated. The mutant TIL shows very low activity for elimination of indole but is still competent to form a quinonoid intermediate from l-tryptophan [Phillips, R. S., Johnson, N., and Kamath, A. V. (2002) Biochemistry 41, 4012-4019]. Stopped-flow measurements show that the formation of the quinonoid intermediate at 505 nm is affected by pH, with a bell-shaped dependence for the forward rate constant, k(f), and dependence on a single basic group for the reverse rate constant, k(r), with the following values: pK(a1) = 8.14 ± 0.15, pK(a2) = 7.54 ± 0.15, k(f,min) = 18.1 ± 1.3 s(-1), k(f,max) = 179 ± 46.3 s(-1), k(r,min) = 11.4 ± 1.2 s(-1), and k(r,max) = 33 ± 1.6 s(-1). The pH effects may be due to ionization of Tyr74 as the base and Cys298 as the acid influencing the rate constant for deprotonation. High-pressure stopped-flow measurements were performed at pH 8, which is the optimum for the forward reaction. The rate constants show an increase with pressure up to 100 MPa and a subsequent decrease above 100 MPa. Fitting the pressure data gives the following values: k(f,0) = 15.4 ± 0.8 s(-1), ΔV(‡) = -29.4 ± 2.9 cm(3) mol(-1), and Δβ(‡) = -0.23 ± 0.03 cm(3) mol(-1) MPa(-1) for the forward reaction, and k(r,0) = 20.7 ± 0.8 s(-1), ΔV(‡) = -9.6 ± 2.3 cm(3) mol(-1), and Δβ(‡) = -0.05 ± 0.02 cm(3) mol(-1) MPa(-1) for the reverse reaction. The primary kinetic isotope effect on quinonoid intermediate formation at pH 8 is small (~2) and is not significantly pressure-dependent, suggesting that the effect of pressure on k(f) may be due to perturbation of an active site preorganization step. The negative activation volume is also consistent with preorganization of the ES complex prior to quinonoid intermediate formation, and the negative compressibility may be due to the effect of pressure on the enzyme conformation. These results support the conclusion that the preorganization of the H463F TIL Trp complex, which is probably dominated by motion of the l-Trp indole moiety of the aldimine complex, contributes to quinonoid intermediate formation.

Formation of MgO-B{sub 4}C composite via a thermite-based combustion reaction

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

Wang, L.L.; Munir, Z.A.; Holt, J.B.

1995-03-01

The combustion synthesis of MgO-B{sub 4}C composites was investigated by coupling a highly exothermic Mg-B{sub 2}O{sub 3} thermite reaction with a weakly exothermic B{sub 4}C formation reaction. Unlike the case of using Al as the reducing agent, the interaction between Mg and B{sub 2}O{sub 3} depends on the surrounding inert gas pressure due to the high vapor pressure of Mg. The interaction changes from one involving predominantly gaseous Mg and liquid B{sub 2}O{sub 3} to one involving liquid Mg and liquid B{sub 2}O{sub 3} as the pressure increases. At low inert gas pressure, the initiation temperature is found to bemore » just below the melting point of Mg (650 C). As the inert gas pressure increases, the vaporization loss of reactants is reduced, and this in turn increases the combustion temperature, which promotes greater grain growth of the product phases, MgO and B{sub 4}C. The particle size of B{sub 4}C increased from about 0.2 to 5 {mu}m as the pressure changed from 1 to 30 atm.« less

Intense cavitation at extreme static pressure.

PubMed

Pishchalnikov, Yuri A; Gutierrez, Joel; Dunbar, Wylene W; Philpott, Richard W

2016-02-01

Cavitation is usually performed at hydrostatic pressures at or near 0.1 MPa. Higher static pressure produces more intense cavitation, but requires an apparatus that can build high amplitude acoustic waves with rarefactions exceeding the cavitation threshold. The absence of such an apparatus has prevented the achievement of intense acoustic cavitation, hindering research and the development of new applications. Here we describe a new high-pressure spherical resonator system, as well as experimental and modeling results in water and liquid metal (gallium), for cavitation at hydrostatic pressures between 10 and 150 MPa. Our computational data, using HYADES plasma hydrodynamics code, show the formation of dense plasma that, under these conditions, reaches peak pressures of about three to four orders of magnitude greater than the hydrostatic pressure in the bulk liquid and temperatures in the range of 100,000 K. Passive cavitation detection (PCD) data validate both a linear increase in shock wave amplitude and the production of highly intense concentrations of mechanical energy in the collapsing bubbles. High-speed camera observations show the formation of bubble clusters from single bubbles. The increased shock wave amplitude produced by bubble clusters, measured using PCD and fiber optic probe hydrophone, was consistent with current understanding that bubble clusters enable amplification of energy produced. Copyright © 2015 Elsevier B.V. All rights reserved.

Star formation in a high-pressure environment: an SMA view of the Galactic Centre dust ridge

NASA Astrophysics Data System (ADS)

Walker, D. L.; Longmore, S. N.; Zhang, Q.; Battersby, C.; Keto, E.; Kruijssen, J. M. D.; Ginsburg, A.; Lu, X.; Henshaw, J. D.; Kauffmann, J.; Pillai, T.; Mills, E. A. C.; Walsh, A. J.; Bally, J.; Ho, L. C.; Immer, K.; Johnston, K. G.

2018-02-01

The star formation rate in the Central Molecular Zone (CMZ) is an order of magnitude lower than predicted according to star formation relations that have been calibrated in the disc of our own and nearby galaxies. Understanding how and why star formation appears to be different in this region is crucial if we are to understand the environmental dependence of the star formation process. Here, we present the detection of a sample of high-mass cores in the CMZ's `dust ridge' that have been discovered with the Submillimeter Array. These cores range in mass from ˜50-2150 M⊙ within radii of 0.1-0.25 pc. All appear to be young (pre-UCHII), meaning that they are prime candidates for representing the initial conditions of high-mass stars and sub-clusters. We report that at least two of these cores (`c1' and `e1') contain young, high-mass protostars. We compare all of the detected cores with high-mass cores and clouds in the Galactic disc and find that they are broadly similar in terms of their masses and sizes, despite being subjected to external pressures that are several orders of magnitude greater, ˜108 K cm-3, as opposed to ˜105 K cm-3. The fact that >80 per cent of these cores do not show any signs of star-forming activity in such a high-pressure environment leads us to conclude that this is further evidence for an increased critical density threshold for star formation in the CMZ due to turbulence.

Cost Differentials between E-Books and Print in Academic Libraries

ERIC Educational Resources Information Center

Bailey, Timothy P.; Scott, Amanda L.; Best, Rickey D.

2015-01-01

Academic libraries continue to face funding pressures compounded by the need to provide students with access to electronic resources, both in journal and book formats. With space constraints and the need to repurpose library space to other uses, libraries must carefully examine the move to e-only formats for books to determine if the format makes…

A Multi-Faceted Formative Assessment Approach: Better Recognising the Learning Needs of Students

ERIC Educational Resources Information Center

Jenkins, James O.

2010-01-01

Students are increasingly subject to a series of learning pressures that prevent effective engagement in assessment. Thus, the aim of this study was to create a multi-faceted formative assessment approach that better enabled students to engage in the assessment process. A formative assessment approach, consisting of six key initiatives, is…

Integrated CO 2 Storage and Brine Extraction

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

Hunter, Kelsey; Bielicki, Jeffrey M.; Middleton, Richard

Carbon dioxide (CO 2) capture, utilization, and storage (CCUS) can reduce CO 2 emissions from fossil fuel power plants by injecting CO 2 into deep saline aquifers for storage. CCUS typically increases reservoir pressure which increases costs, because less CO 2 can be injected, and risks such as induced seismicity. Extracting brine with enhanced water recovery (EWR) from the CO 2 storage reservoir can manage and reduce pressure in the formation, decrease the risks linked to reservoir overpressure (e.g., induced seismicity), increase CO 2 storage capacity, and enable CO 2 plume management. We modeled scenarios of CO 2 injection withmore » EWR into the Rock Springs Uplift (RSU) formation in southwest Wyoming. The Finite Element Heat and Mass Transfer Code (FEHM) was used to model CO 2 injection with brine extraction and the corresponding increase in pressure within the RSU. We analyzed the model for pressure management, CO 2 storage, CO 2 saturation, and brine extraction due to the quantity and location of brine extraction wells. The model limited CO 2 injection to a constant pressure increase of two MPa at the injection well with and without extracting brine at hydrostatic pressure. Finally, we found that brine extraction can be used as a technical and cost-effective pressure management strategy to limit reservoir pressure buildup and increase CO 2 storage associated with a single injection well.« less

Integrated CO 2 Storage and Brine Extraction

DOE PAGES

Hunter, Kelsey; Bielicki, Jeffrey M.; Middleton, Richard; ...

2017-08-18

Carbon dioxide (CO 2) capture, utilization, and storage (CCUS) can reduce CO 2 emissions from fossil fuel power plants by injecting CO 2 into deep saline aquifers for storage. CCUS typically increases reservoir pressure which increases costs, because less CO 2 can be injected, and risks such as induced seismicity. Extracting brine with enhanced water recovery (EWR) from the CO 2 storage reservoir can manage and reduce pressure in the formation, decrease the risks linked to reservoir overpressure (e.g., induced seismicity), increase CO 2 storage capacity, and enable CO 2 plume management. We modeled scenarios of CO 2 injection withmore » EWR into the Rock Springs Uplift (RSU) formation in southwest Wyoming. The Finite Element Heat and Mass Transfer Code (FEHM) was used to model CO 2 injection with brine extraction and the corresponding increase in pressure within the RSU. We analyzed the model for pressure management, CO 2 storage, CO 2 saturation, and brine extraction due to the quantity and location of brine extraction wells. The model limited CO 2 injection to a constant pressure increase of two MPa at the injection well with and without extracting brine at hydrostatic pressure. Finally, we found that brine extraction can be used as a technical and cost-effective pressure management strategy to limit reservoir pressure buildup and increase CO 2 storage associated with a single injection well.« less

Method and system for producing lower alcohols. [Heteropolyatomic lead salt coated with alkali metal formate

DOEpatents

Rathke, J.W.; Klingler, R.J.; Heiberger, J.J.

1983-09-26

It is an object of the present invention to provide an improved catalyst for the reaction of carbon monoxide with water to produce methanol and other lower alcohols. It is a further object to provide a process for the production of methanol from carbon monoxide and water in which a relatively inexpensive catalyst permits the reaction at low pressures. It is also an object to provide a process for the production of methanol from carbon monoxide and water in which a relatively inexpensive catalyst permits the reaction at low pressures. It is also an object to provide a process for the production of methanol in which ethanol is also directly produced. It is another object to provide a process for the production of mixtures of methanol with ethanol and propanol from the reaction of carbon monoxide and water at moderate pressure with inexpensive catalysts. It is likewise an object to provide a system for the catalytic production of lower alcohols from the reaction of carbon monoxide and water at moderate pressure with inexpensive catalysts. In accordance with the present invention, a catalyst is provided for the reaction of carbon monoxide and water to produce lower alcohols. The catalyst includes a lead heteropolyatomic salt in mixture with a metal formate or a precursor to a metal formate.

Formation and electronic properties of palladium hydrides and palladium-rhodium dihydride alloys under pressure.

PubMed

Yang, Xiao; Li, Huijian; Ahuja, Rajeev; Kang, Taewon; Luo, Wei

2017-06-14

We present the formation possibility for Pd-hydrides and Pd-Rh hydrides system by density functional theory (DFT) in high pressure upto 50 GPa. Calculation confirmed that PdH 2 in face-centered cubic (fcc) structure is not stable under compression that will decomposition to fcc-PdH and H 2 . But it can be formed under high pressure while the palladium is involved in the reaction. We also indicate a probably reason why PdH 2 can not be synthesised in experiment due to PdH is most favourite to be formed in Pd and H 2 environment from ambient to higher pressure. With Rh doped, the Pd-Rh dihydrides are stabilized in fcc structure for 25% and 75% doping and in tetragonal structure for 50% doping, and can be formed from Pd, Rh and H 2 at high pressure. The electronic structural study on fcc type Pd x Rh 1-x H 2 indicates the electronic and structural transition from metallic to semi-metallic as Pd increased from x = 0 to 1.

Numerical Analysis of Extremely-rich CH4/O2/H2O Premixed Flames at High Pressure and High Temperature Considering Production of Higher Hydrocarbons

NASA Astrophysics Data System (ADS)

Kumagami, Manabu; Ogami, Yasuhiro; Tamaki, Yuichi; Kobayashi, Hideaki

Numerical analysis of CH4/O2/H2O laminar premixed flame under various conditions of pressure, equivalence ratio and steam concentration was performed using GRI-Mech 3.0 and the mechanism proposed by Davis and Law, which consists of C1 to C6 hydrocarbons in addition to GRI-Mech 3.0. The pressure dependence of laminar burning velocity and flame structure under fuel-rich conditions was focused on. Effects of the formation of higher hydrocarbons under fuel-rich conditions were also clarified using the mechanism proposed by Davis and Law. Results showed that for extremely fuel-rich conditions, laminar burning velocity increases as pressure increases for both mechanisms. The increase of laminar burning velocity is caused by the shift of the oxidation pathway of CH3 radical from the C2 Route to the C1 Route. The formation of C3-C6 hydrocarbons has only a small effect on laminar burning velocity. Under fuel-rich conditions, super-adiabatic flame temperature (SAFT) occurs and its pressure dependency was clarified.

Mechanism of Runaway Electron Generation at Gas Pressures from a Few Atmospheres to Several Tens of Atmospheres

NASA Astrophysics Data System (ADS)

Zubarev, N. M.; Ivanov, S. N.

2018-04-01

The mechanism of runaway electron generation at gas pressures from a few atmospheres to several tens of atmospheres is proposed. According to this mechanism, the electrons pass into the runaway mode in the enhanced field zone that arises between a cathode micropoint—a source of field-emission electrons—and the region of the positive ion space charge accumulated near the cathode in the tails of the developing electron avalanches. As a result, volume gas ionization by runaway electrons begins with a time delay required for the formation of the enhanced field zone. This process determines the delay time of breakdown. The influence of the gas pressure on the formation dynamics of the space charge region is analyzed. At gas pressures of a few atmospheres, the space charge arises due to the avalanche multiplication of the very first field-emission electron, whereas at pressures of several tens of atmospheres, the space charge forms as a result of superposition of many electron avalanches with a relatively small number of charge carriers in each.

Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system

NASA Technical Reports Server (NTRS)

Lunine, J. I.; Stevenson, D. J.

1985-01-01

The thermodynamic stability of clathrate hydrate is calculated to predict the formation conditions corresponding to a range of solar system parameters. The calculations were performed using the statistical mechanical theory developed by van der Waals and Platteeuw (1959) and existing experimental data concerning clathrate hydrate and its components. Dissociation pressures and partition functions (Langmuir constants) are predicted at low pressure for CO clathrate (hydrate) using the properties of chemicals similar to CO. It is argued that nonsolar but well constrained noble gas abundances may be measurable by the Galileo spacecraft in the Jovian atmosphere if the observed carbon enhancement is due to bombardment of the atmosphere by clathrate-bearing planetesimals sometime after planetary formation. The noble gas abundances of the Jovian satellite Titan are predicted, assuming that most of the methane in Titan is accreted as clathrate. It is suggested that under thermodynamically appropriate conditions, complete clathration of water ice could have occurred in high-pressure nebulas around giant planets, but probably not in the outer solar nebula. The stability of clathrate in other pressure ranges is also discussed.

Paleostress and fluid-pressure regimes inferred from the orientations of Hishikari low sulfidation epithermal gold veins in southern Japan

NASA Astrophysics Data System (ADS)

Faye, Guillaume D.; Yamaji, Atsushi; Yonezu, Kotaro; Tindell, Thomas; Watanabe, Koichiro

2018-05-01

The orientation distribution of dilational fractures is affected by the state of stress around the fractures and by the pressure of the fluid that opened the fractures. Thus, the distribution can be inverted to determine not only the stress but also the pressure condition at the time of vein formation. However, epithermal ore veins that we observe today are the results of a great number of intermittent upwelling of overpressured fluids with different pressures. Here, we define driving pressure index (DPI) as the representative non-dimensionalized fluid pressure for the fluids. We collected the orientations of ∼1000 ore veins in the Hishikari gold mine, which were deposited at around 1 Ma, in southern Kyushu, Japan. It was found that the majority of the veins were deposited under an extensional stress with a NW-SE-trending σ3-axis and a northeasterly-inclined σ1-axis with relatively high stress ratio. The representative driving pressure ratio was ∼0.2. Data sets obtained at different depths in the mine indicated a positive correlation of representative driving pressure ratios with the depths. The correlation suggests repeated formation and break of pressure seals during the mineralization. Our compilation of the Pliocene-Quaternary stress regimes in southern Kyushu, including the result of the present study, suggests that epithermal gold mineralization was associated with distributed extensional deformations in southern Kyushu, and strain localization into an intra-arc rift seems to have terminated the mineralization.

Early Detection of Pressure Ulcer Development Following Traumatic Spinal Cord Injury Using Inflammatory Mediators.

PubMed

Krishnan, Shilpa; Karg, Patricia E; Boninger, Michael L; Vodovotz, Yoram; Constantine, Greg; Sowa, Gwendolyn A; Brienza, David M

2016-10-01

To identify changes in concentrations of inflammatory mediators in plasma and urine after traumatic spinal cord injury (SCI) and before the occurrence of a first pressure ulcer. Retrospective; secondary analysis of existing data. Acute hospitalization and inpatient rehabilitation sites at a university medical center. Individuals with a pressure ulcer and plasma samples (n=17) and individuals with a pressure ulcer and urine samples (n=15) were matched by age and plasma/urine sample days to individuals with SCI and no pressure ulcer (N=35). Not applicable. Plasma and urine samples were assayed in patients with SCI, capturing samples within 4 days after the SCI to a week before the formation of the first pressure ulcer. The Wilcoxon signed-rank test was performed to identify changes in the inflammatory mediators between the 2 time points. An increase in concentration of the chemokine interferon-γ-induced protein of 10kd/CXCL10 in plasma (P<.01) and a decrease in concentration of the cytokine interferon-α in urine (P=.01) were observed before occurrence of a first pressure ulcer (∼4d) compared with matched controls. Altered levels of inflammatory mediators in plasma and urine may be associated with pressure ulcer development after traumatic SCI. These inflammatory mediators should be explored as possible biomarkers for identifying individuals at risk for pressure ulcer formation. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

The effect of abdominal pressure on urinary flow rate.

PubMed

Hasegawa, N; Kitagawa, Y; Takasaki, N; Miyazaki, S

1983-07-01

We examined the effect of abdominal pressure on urinary flow rate and urethral closure pressure in 46 subjects, ranging in age from 26 to 82 years. An increase in urinary flow rate caused by abdominal straining was not found when organic obstruction was present in the prostatic urethra in men or the proximal urethra in women, or when dysuria is caused by the lowered detrusor pressure. An increase in urinary flow rate caused by straining was noted when anterior urethral stricture or stress incontinence was present. The increase in urinary flow rate owing to straining was undetermined in the control group. The urethral closure pressure on the anti-stress incontinence zone increased as a result of straining at the same time and to the same degree as did the intravesical pressure. When the anti-stress incontinence zone was subjected to transurethral resection for canal formation urination became possible as a result of straining. The patients who were able to urinate with straining sometimes suffered temporary stress incontinence. The degree of straining did not determine whether the patient could urinate with straining. Therefore, it was concluded that abdominal pressure should be excluded from intravesical pressure in performing several urodynamic studies on the lower urinary tract, such as pressure flow studies, and that it is important to have a sufficient canal formation in the anti-stress incontinence zone when urination with straining is expected when performing an operation on patients with urethral obstruction in the anti-stress incontinence zone.

Laser-assisted formation of micropores and nanobubbles in sclera promote stable normalization of intraocular pressure

NASA Astrophysics Data System (ADS)

Baum, Olga; Wachsmann-Hogiu, Sebastian; Milner, Thomas; Sobol, Emil

2017-06-01

Pores in sclera enhance uveoscleral water outflow and can normalize intraocular pressure in glaucomatous eyes. The aims of this study are to demonstrate laser-induced formation of pores with a dendritic structure and to answer the questions: How is a pore system stable and can laser treatment provide a long-lasting pressure stabilization effect? Effect of 1.56 µm laser radiation on porcine eye sclera was studied using atomic force microscopy and super resolution structured irradiation microscopy with fluorescent markers. Results suggest that the pores with a complex spatial configuration can arise as a result of laser irradiation and that laser-generated stable gas nanobubbles coated with calcium ions allow pore stabilization in the sclera. Our results support a laser based approach for treatment of glaucoma.

Pressure and tension waves from bubble collapse near a solid boundary: A numerical approach.

PubMed

Lechner, Christiane; Koch, Max; Lauterborn, Werner; Mettin, Robert

2017-12-01

The acoustic waves being generated during the motion of a bubble in water near a solid boundary are calculated numerically. The open source package OpenFOAM is used for solving the Navier-Stokes equation and extended to include nonlinear acoustic wave effects via the Tait equation for water. A bubble model with a small amount of gas is chosen, the gas obeying an adiabatic law. A bubble starting from a small size with high internal pressure near a flat, solid boundary is studied. The sequence of events from bubble growth via axial microjet formation, jet impact, annular nanojet formation, torus-bubble collapse, and bubble rebound to second collapse is described. The different pressure and tension waves with their propagation properties are demonstrated.

3D modeling of unconstrained HPT process: role of strain gradient on high deformed microstructure formation

NASA Astrophysics Data System (ADS)

Ben Kaabar, A.; Aoufi, A.; Descartes, S.; Desrayaud, C.

2017-05-01

During tribological contact’s life, different deformation paths lead to the formation of high deformed microstructure, in the near-surface layers of the bodies. The mechanical conditions (high pressure, shear) occurring under contact, are reproduced through unconstrained High Pressure Torsion configuration. A 3D finite element model of this HPT test is developed to study the local deformation history leading to high deformed microstructure with nominal pressure and friction coefficient. For the present numerical study the friction coefficient at the interface sample/anvils is kept constant at 0.3; the material used is high purity iron. The strain distribution in the sample bulk, as well as the main components of the strain gradients according to the spatial coordinates are investigated, with rotation angle of the anvil.

Curious kinetic behavior in silica polymorphs solves seifertite puzzle in shocked meteorite

PubMed Central

Kubo, Tomoaki; Kato, Takumi; Higo, Yuji; Funakoshi, Ken-ichi

2015-01-01

The presence of seifertite, one of the high-pressure polymorphs of silica, in achondritic shocked meteorites has been problematic because this phase is thermodynamically stable at more than ~100 GPa, unrealistically high-pressure conditions for the shock events in the early solar system. We conducted in situ x-ray diffraction measurements at high pressure and temperatures, and found that it metastably appears down to ~11 GPa owing to the clear difference in kinetics between the metastable seifertite and stable stishovite formations. The temperature-insensitive but time-sensitive kinetics for the formation of seifertite uniquely constrains that the critical shock duration and size of the impactor on differentiated parental bodies are at least ~0.01 s and ~50 to 100 m, respectively, from the presence of seifertite. PMID:26601182

Experimental investigation of the effect of insulator sleeve length on the time to pinch and multipinch formation in the plasma focus facility

NASA Astrophysics Data System (ADS)

Momenei, M.; Khodabakhshei, Z.; Panahi, N.; Mohammadi, M. A.

2017-03-01

The length of insulator sleeve is varied to investigate its effect on the pinch formation in the plasma focus facility. In this paper, the effect of insulator length on the time to pinch at various pressures and working voltages in the 1.15 kJ Mather type plasma focus is investigated. The results show that with 4.5 cm insulator length the time to pinch at all pressures is minimum. Other results also confirm that with increasing of pressure the time to pinch is increased. Moreover, with increasing working voltage the time to pinch is decreased. Pictures, captured using a digital single lens reflex (DSLR) Canon EOS 7D system, show that multipinch phenomenon is formed.

Restoration of the Potosi Dynamic Model 2010

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

Adushita, Yasmin; Leetaru, Hannes

2014-09-30

In topical Report DOE/FE0002068-1 [2] technical performance evaluations on the Cambrian Potosi Formation were performed through reservoir modeling. The data included formation tops from mud logs, well logs from the VW1 and the CCS1 wells, structural and stratigraphic formation from three dimensional (3D) seismic data, and field data from several waste water injection wells for Potosi Formation. Intention was for two million tons per annum (MTPA) of CO2 to be injected for 20 years. In this Task the 2010 Potosi heterogeneous model (referred to as the "Potosi Dynamic Model 2010" in this report) was re-run using a new injection scenario;more » 3.2 MTPA for 30 years. The extent of the Potosi Dynamic Model 2010, however, appeared too small for the new injection target. It was not sufficiently large enough to accommodate the evolution of the plume. Also, it might have overestimated the injection capacity by enhancing too much the pressure relief due to the relatively close proximity between the injector and the infinite acting boundaries. The new model, Potosi Dynamic Model 2013a, was built by extending the Potosi Dynamic Model 2010 grid to 30 miles x 30 miles (48 km by 48 km), while preserving all property modeling workflows and layering. This model was retained as the base case. Potosi Dynamic Model 2013.a gives an average CO2 injection rate of 1.4 MTPA and cumulative injection of 43 Mt in 30 years, which corresponds to 45% of the injection target. This implies that according to this preliminary model, a minimum of three (3) wells could be required to achieve the injection target. The injectivity evaluation of the Potosi formation will be revisited in topical Report 15 during which more data will be integrated in the modeling exercise. A vertical flow performance evaluation could be considered for the succeeding task to determine the appropriate tubing size, the required injection tubing head pressure (THP) and to investigate whether the corresponding well injection rate falls within the tubing erosional velocity limit. After 30 years, the plume extends 15 miles (24 km) in E-W and 14 miles (22 km) in N-S directions. After injection is completed, the plume continues to migrate laterally, mainly driven by the remaining pressure gradient. After 100 years post-injection, the plume extends 17 miles (27 km) in E-W and 15 miles (24 km) in N-S directions. The increase of reservoir pressure at the end of injection is approximately 370 psia around the injector and gradually decreases away from the well. The reservoir pressure increase is less than 30 psia beyond 14 miles (22 km) away from injector. The initial reservoir pressure is restored after approximately 20 years post-injection. This result, however, is associated with uncertainties on the boundary conditions, and a sensitivity analysis could be considered for the succeeding tasks. It is important to remember that the respective plume extent and areal pressure increase corresponds to an injection of 43 Mt CO2. Should the targeted cumulative injection of 96 Mt be achieved; a much larger plume extent and areal pressure increase could be expected. Re-evaluating the permeability modeling, vugs and heterogeneity distributions, and relative permeability input could be considered for the succeeding Potosi formation evaluations. A simulation using several injectors could also be considered to determine the required number of wells to achieve the injection target while taking into account the pressure interference.« less

Measurement and reduction of micro-bubble formation in high-viscosity fluids

NASA Astrophysics Data System (ADS)

Tom, Glenn; Liu, Wei

2012-03-01

Gases at high drive pressure can initially dissolve into the fluids used in lithography and other critical processes during the fabrication of integrated circuits. In the low pressure portion of the dispense train, the dissolved gases can revert to bubbles. These bubbles can: 1. Affect the compressibility of the working fluid and change the flow characteristics of the dispense heads which require frequent re-tuning of the coating tools. 2. Contribute to defect formation if the bubbles are trapped on the surface of the wafer. Photosensitive Polyimides (PI) have high viscosities (1000 to 20,000 cP). Because of the high viscosity, high-powered, expensive pumps are needed to effectively remove the fluid from its container. Suction from the pump filling cycle easily causes cavitation, which can create flow rate variability, and micro-bubble formation. It is a common practice to apply pressure to the PI resists to minimize cavitation in the pump. The trade-off to this practice is the entrainment (dissolution) of the drive gas into the resist and the risk of micro-bubbles forming later in the dispense train. In the current study, ATMI measured the effects of two methods of pressure dispense from the container on the amount of gas entrained in a viscous fluid: (1) indirect pressure dispense and (2) direct pressure dispense. The main analytical method employed to measure the amount of dissolved gases is a gas chromatograph (GC), which can measure the concentration of gases dissolved in a volatile fluid. It is not suitable to measure gases in low volatility fluids. The new test method developed, however, is capable of measuring dissolved gases in low volatility fluids.

Pressure-induced amorphization in plagioclase feldspars: A time-resolved powder diffraction study during rapid compression

NASA Astrophysics Data System (ADS)

Sims, M.; Jaret, S.; Carl, E. R.; Schrodt, N.; Rhymer, B.; Mohrholz, V.; Konopkova, Z.; Smith, J.; Liermann, H. P.; Glotch, T. D.; Ehm, L.

2017-12-01

Impact cratering is important in planetary body formation and evolution [1]. The pressure and temperature conditions during impacts are classified using systems [2] that stem from 1) petrographic features and 2) the presence of high pressure mineral phases observed in impactites. Maskelynite, amorphous plagioclase ((Na1-x Cax)Al1+x Si2-x O8), is a key indicator of petrographic type S5 (strongly shocked) and forms between 25 and 45 GPa. However, the formation pressure of maskelynite differs substantially depending on the experimental technique producing it. Shock experiments produce amorphization at > 10 GPa higher than static diamond anvil cell (DAC) experiments. We utilize a new technique, fast compression in combination with time-resolved powder diffraction, to study the effect of strain rate on plagioclase amorphization pressure. Anorthite and albite were compressed to 80 GPa at multiple rates from 0.05 GPa/s to 80 GPa/s, and we observed a decrease in amorphization pressure with increasing compression rate for strain rates of about 10-3 s-1. This decrease demonstrates negative strain rate sensitivity, which is likely caused by structural defects. Negative strain rate sensitivity implies that faster rates are more ductile and heterogeneous and slower rates are more brittle and homogeneous. Our results fit into the deformation framework proposed by Huffman and Reimold [3] and are consistent with the formation mechanism for maskelynite by "shear melting" proposed by Grady [4]. [1] Chao, E.C.T., Shock Metamorphism of Natural Materials., Baltimore, Md: Mono Book Corp, 1968; [2] Stöffler, D., J. Geophys. Res, 76(23), 5541, 1971; [3] Huffman, A.R. and W.U. Reimold, Tectonophysics, 256(1-4), 165-217, 1996; [4] Grady, D., J. Geophys. Res. Solid Earth, 85(B2), 913-924, 1980.

Atelectasis is inversely proportional to transpulmonary pressure during weaning from ventilator support in a large animal model.

PubMed

Gudmundsson, M; Perchiazzi, G; Pellegrini, M; Vena, A; Hedenstierna, G; Rylander, C

2018-01-01

In mechanically ventilated, lung injured, patients without spontaneous breathing effort, atelectasis with shunt and desaturation may appear suddenly when ventilator pressures are decreased. It is not known how such a formation of atelectasis is related to transpulmonary pressure (P L ) during weaning from mechanical ventilation when the spontaneous breathing effort is increased. If the relation between P L and atelectasis were known, monitoring of P L might help to avoid formation of atelectasis and cyclic collapse during weaning. The main purpose of this study was to determine the relation between P L and atelectasis in an experimental model representing weaning from mechanical ventilation. Dynamic transverse computed tomography scans were acquired in ten anaesthetized, surfactant-depleted pigs with preserved spontaneous breathing, as ventilator support was lowered by sequentially reducing inspiratory pressure and positive end expiratory pressure in steps. The volumes of gas and atelectasis in the lungs were correlated with P L obtained using oesophageal pressure recordings. Work of breathing (WOB) was assessed from Campbell diagrams. Gradual decrease in P L in both end-expiration and end-inspiration caused a proportional increase in atelectasis and decrease in the gas content (linear mixed model with an autoregressive correlation matrix; P < 0.001) as the WOB increased. However, cyclic alveolar collapse during tidal ventilation did not increase significantly. We found a proportional correlation between atelectasis and P L during the 'weaning process' in experimental mild lung injury. If confirmed in the clinical setting, a gradual tapering of ventilator support can be recommended for weaning without risk of sudden formation of atelectasis. © 2017 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

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

Bolstad, J.W.; Haarman, R.A.

The results of two transients involving the loss of a steam generator in a single-pass, steam generator, pressurized water reactor have been analyzed using a state-of-the-art, thermal-hydraulic computer code. Computed results include the formation of a steam bubble in the core while the pressurizer is solid. Calculations show that continued injection of high pressure water would have stopped the scenario. These are similar to the happenings at Three Mile Island.

The gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide from combustion calorimetry, vapor pressure measurements, and ab initio calculations.

PubMed

Emel'yanenko, Vladimir N; Verevkin, Sergey P; Heintz, Andreas

2007-04-04

Ionic liquids are attracting growing interest as alternatives to conventional molecular solvents. Experimental values of vapor pressure, enthalpy of vaporization, and enthalpy of formation of ionic liquids are the key thermodynamic quantities, which are required for the validation and development of the molecular modeling and ab initio methods toward this new class of solvents. In this work, the molar enthalpy of formation of the liquid 1-butyl-3-methylimidazolium dicyanamide, 206.2 +/- 2.5 kJ.mol-1, was measured by means of combustion calorimetry. The molar enthalpy of vaporization of 1-butyl-3-methylimidazolium dicyanamide, 157.2 +/- 1.1 kJ.mol-1, was obtained from the temperature dependence of the vapor pressure measured using the transpiration method. The latter method has been checked with measurements of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, where data are available from the effusion technique. The first experimental determination of the gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide, 363.4 +/- 2.7 kJ.mol-1, from thermochemical measurements (combustion and transpiration) is presented. Ab initio calculations of the enthalpy of formation in the gaseous phase have been performed for 1-butyl-3-methylimidazolium dicyanamide using the G3MP2 theory. Excellent agreement with experimental results has been observed. The method developed opens a new way to obtain thermodynamic properties of ionic liquids which have not been available so far.

Quasicrystals at extreme conditions: The role of pressure in stabilizing icosahedral Al 63Cu 24Fe 13 at high temperature

DOE PAGES

Stagno, Vincenzo; Bindi, Luca; Park, Changyong; ...

2015-11-20

Icosahedrite, the first natural quasicrystal with composition Al 63Cu 24Fe 13, was discovered in several grains of the Khatyrka meteorite, a unique CV3 carbonaceous chondrite. The presence in the meteorite fragments of icosahedrite strictly associated with high-pressure phases like ahrensite and stishovite indicates a formation conditions at high pressures and temperatures, likely during an impact-induced shock occurred in contact with the reducing solar nebula gas. In contrast, previous experimental studies on the stability of synthetic icosahedral AlCuFe, which were limited to ambient pressure, indicated incongruent melting at ~1123 K, while high-pressure experiments carried out at room temperature showed structural stabilitymore » up to about 35 GPa. These data are insufficient to experimentally constrain the formation and stability of icosahedrite under extreme conditions. Here we present the results of in situ high pressure experiments using diamond anvil cells of the compressional behavior of synthetic icosahedrite up to ~50 GPa at room temperature. Simultaneous high P-T experiments have been also carried out using both laser-heated diamond anvil cells combined with in situ synchrotron X-ray diffraction (at ~42 GPa) and multi-anvil apparatus (at 21 GPa) to investigate the structural evolution of icosahedral Al 63Cu 24Fe 13 and crystallization of possible coexisting phases. The results demonstrate that the quasiperiodic symmetry of icosahedrite is retained over the entire experimental pressure range explored. In addition, we show that pressure acts to stabilize the icosahedral symmetry at temperatures much higher than previously reported. Based on our experimental study, direct crystallization of Al-Cu-Fe quasicrystals from an unusual Al-Cu-rich melt would be possible but limited to a narrow temperature range beyond which crystalline phases would form, like those observed in the Khatyrka meteorite. Here, an alternative mechanism would consist in late formation of the quasicrystal after crystallization and solid-solid reaction of Al-rich phases. In both cases, linking our results with observations in nature, quasicrystals are expected to preserve their structure even after hypervelocity impacts that involve simultaneous high pressures and temperatures, thus proving their cosmic stability.« less

Pressure regulates osteoclast formation and MCSF expression in marrow culture.

PubMed

Rubin, J; Biskobing, D; Fan, X; Rubin, C; McLeod, K; Taylor, W R

1997-01-01

One of the forces generated during skeletal loading is hydrostatic pressure. In the work presented here, the ability of increased pressure to influence recruitment of osteoclasts was evaluated. Murine marrow cultures, with pO2 and pCO2 kept constant, were subjected to either control (1.0 atm) or elevated (1.37 or 2.0 atm) hydrostatic pressure. As compared to control, cultures pressurized for 6 days at 1.37 atm formed less osteoclast-like cells (OCLC) (71 +/- 6% of control, P < 0.0001). A similar degree of inhibition occurred in cultures exposed to pressure during days 2-4 only (62 +/- 6%), while treatment during days 5-7 failed to inhibit the OCLC number relative to control (99 +/- 5%). Delivery of 2.0 atm pressure on days 2-4 generated 52 +/- 4% OCLC compared to control. Since macrophage colony stimulating factor (MCSF)-dependent proliferation of osteoclast precursors occurs during the pressure-sensitive period, semiquantitative RT-PCR for MCSF mRNA was performed after 3 days in 1.37 atm (days 2-4). As compared to controls, pressure caused a decrease in mRNA coding for the membrane bound form of MCSF (71.2 +/- 4% (n = 25, P < or = 0.05), while the MCSF RT-PCR product representing the secreted form showed no consistent change. This lack of response of the soluble MCSF RT-PCR product was expected, as levels of bioassayable MCSF were not altered by pressure. Extrapolating these data to in vivo conditions suggests that load-bearing will inhibit the formation of osteoclasts.

Advanced life systems hardware development for future missions

NASA Technical Reports Server (NTRS)

1975-01-01

An examination of the pulse formation in an externalized vessel suggests that the vessel does not behave as a simple visco-elastic tube. Pressure-pulse waveform transducers are sensitive either to the pressure present at the vessel wall or to the volume of blood filling a region of tissue. Results of comparisons between intra-and extra-vascular pressure recordings suggest that changes in vasomotor tone and transducer-vessel pressures may be the greatest contributors to the divergence of extra-vascular waveforms from intra-vascular waveforms.

Influence of pressure on acoustic and rheologic parameters in water solutions of laury sodium sulfate

NASA Astrophysics Data System (ADS)

Khamidov, B. T.; Lezhnev, N. B.

1995-10-01

Ultrasonic velocity and density in water solutions of lauril sodium sulphate at frequency 36 MHz, within the range of pressures from 0.1 to 105 MPa at temperature T equals 293 K were measured. According to data of ultrasonic velocity and density under high pressures there was calculated adiabatic compressibility in objects studied from pressure. It was found out that the region of critical concentration of micelle formation has been shifted to the zone of much more low concentrations.

Supercritical fuel injection system

NASA Technical Reports Server (NTRS)

Marek, C. J.; Cooper, L. P. (Inventor)

1980-01-01

a fuel injection system for gas turbines is described including a pair of high pressure pumps. The pumps provide fuel and a carrier fluid such as air at pressures above the critical pressure of the fuel. A supercritical mixing chamber mixes the fuel and carrier fluid and the mixture is sprayed into a combustion chamber. The use of fuel and a carrier fluid at supercritical pressures promotes rapid mixing of the fuel in the combustion chamber so as to reduce the formation of pollutants and promote cleaner burning.

Quenchable compressed graphite synthesized from neutron-irradiated highly oriented pyrolytic graphite in high pressure treatment at 1500 °C

NASA Astrophysics Data System (ADS)

Niwase, Keisuke; Terasawa, Mititaka; Honda, Shin-ichi; Niibe, Masahito; Hisakuni, Tomohiko; Iwata, Tadao; Higo, Yuji; Hirai, Takeshi; Shinmei, Toru; Ohfuji, Hiroaki; Irifune, Tetsuo

2018-04-01

The super hard material of "compressed graphite" (CG) has been reported to be formed under compression of graphite at room temperature. However, it returns to graphite under decompression. Neutron-irradiated graphite, on the other hand, is a unique material for the synthesis of a new carbon phase, as reported by the formation of an amorphous diamond by shock compression. Here, we investigate the change of structure of highly oriented pyrolytic graphite (HOPG) irradiated with neutrons to a fluence of 1.4 × 1024 n/m2 under static pressure. The neutron-irradiated HOPG sample was compressed to 15 GPa at room temperature and then the temperature was increased up to 1500 °C. X-ray diffraction, high-resolution transmission electron microscopy on the recovered sample clearly showed the formation of a significant amount of quenchable-CG with ordinary graphite. Formation of hexagonal and cubic diamonds was also confirmed. The effect of irradiation-induced defects on the synthesis of quenchable-CG under high pressure and high temperature treatment was discussed.

Lithium vapor/aerosol studies. Interim summary report

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

Whitlow, G.A.; Bauerle, J.E.; Down, M.G.

1979-04-01

The temperature/cover gas pressure regime, in which detectable lithium aerosol is formed in a static system has been mapped for argon and helium cover gases using a portable He--Ne laser device. At 538/sup 0/C (1000/sup 0/F), lithium aerosol particles were observed over the range 0.5 to 20 torr and 2 to 10 torr for argon and helium respectively. The experimental conditions in this study were more conducive to aerosol formation than in a fusion reactor. In the real reactor system, very high intensity mechanical and thermal disturbances will be made to the liquid lithium. These disturbances, particularly transient increases inmore » lithium vapor pressure appear to be capable of producing high concentrations of optically-dense aerosol. A more detailed study is, therefore, proposed using the basic information generated in these preliminary experiments, as a starting point. Areas recommended include the kinetics of aerosol formation and the occurrence of supersaturated vapor during rapid vapor pressure transients, and also the effect of lithium agitation (falls, jets, splashing, etc.) on aerosol formation.« less

Pressure-temperature phase behavior of mixtures of natural sphingomyelin and ceramide extracts.

PubMed

Barriga, Hanna M G; Parsons, Edward S; McCarthy, Nicola L C; Ces, Oscar; Seddon, John M; Law, Robert V; Brooks, Nicholas J

2015-03-31

Ceramides are a group of sphingolipids that act as highly important signaling molecules in a variety of cellular processes including differentiation and apoptosis. The predominant in vivo synthetic pathway for ceramide formation is via sphingomyelinase catalyzed hydrolysis of sphingomyelin. The biochemistry of this essential pathway has been studied in detail; however, there is currently a lack of information on the structural behavior of sphingomyelin- and ceramide-rich model membrane systems, which is essential for developing a bottom-up understanding of ceramide signaling and platform formation. We have studied the lyotropic phase behavior of sphingomyelin-ceramide mixtures in excess water as a function of temperature (30-70 °C) and pressure (1-200 MPa) by small- and wide-angle X-ray scattering. At low ceramide concentrations the mixtures form the ripple gel phase (P(β)') below the gel transition temperature for sphingomyelin, and this observation has been confirmed by atomic force microscopy. Formation of the ripple gel phase can also be induced at higher temperatures via the application of hydrostatic pressure. At high ceramide concentration an inverse hexagonal phase (HII) is formed coexisting with a cubic phase.

Observing RAM Pressure Stripping and Morphological Transformation in the Coma Cluster

NASA Astrophysics Data System (ADS)

Gregg, Michael; West, Michael

2017-07-01

The two largest spirals in the Coma cluster, NGC4911 and NGC4921, are being vigorously ram-pressure stripped by the hot intracluster medium. Our HST ACS and WFC3 images have revealed galactic scale shock fronts, giant "Pillars of Creation", rivulets of dust, and spatially coherent star formation in these grand design spirals. We have now obtained HST WFC3 imaging of five additional large Coma spirals to search for and investigate the effects of ram pressure stripping across the wider cluster environment. The results are equally spectacular as the first two examples. The geometry of the interactions in some cases allows an estimation of the various time scales involved, including gas flows out of the disk leading to creation of the ICM, and the attendant triggered star formation in the galaxy disks. The global star formation patterns yield insights into the spatial and temporal ISM-ICM interactions driving cluster galaxy evolution and ultimately transforming morphologies from spiral to S0. These processes were much more common in the early Universe when the intergalactic and intracluster components were initially created from stripping and destruction of member galaxies.

Nanobubbles: a new paradigm for air-seeding in xylem.

PubMed

Schenk, H Jochen; Steppe, Kathy; Jansen, Steven

2015-04-01

Long-distance water transport in plants relies on a system that typically operates under negative pressure and is prone to hydraulic failure due to gas bubble formation. One primary mechanism of bubble formation takes place at nanoporous pit membranes between neighboring conduits. We argue that this process is likely to snap off nanobubbles because the local increase in liquid pressure caused by entry of air-water menisci into the complex pit membrane pores would energetically favor nanobubble formation over instant cavitation. Nanobubbles would be stabilized by surfactants and by gas supersaturation of the sap, may dissolve, fragment into smaller bubbles, or create embolisms. The hypothesis that safe and stable nanobubbles occur in plants adds a new component supporting the cohesion-tension theory. Copyright © 2015 Elsevier Ltd. All rights reserved.

Millimeter-Wave Time Resolved Studies of the Formation and Decay of CO^+

NASA Astrophysics Data System (ADS)

Oesterling, Lee; Herbst, Eric; de Lucia, Frank

1998-04-01

Since the rate constants for ion-molecule interactions are typically much larger than neutral-neutral interactions, understanding ion-molecule interactions is essential to interpreting radio astronomical spectra from interstellar clouds and modeling the processes which lead to the formation of stars in these regions. We have developed a cell which allows us to study ion-molecule interactions in gases at low temperatures and pressures by using an electron gun technique to create ions. By centering our millimeter-wave source on a rotational resonance and gating the electron beam on and off, we are able to study the time-dependent rotational state distribution of the ion during its formation and decay, and so learn about excitation and relaxation processes as functions of temperature, pressure, electron beam energy, and electron beam current.

Fuel quality combustion analysis

NASA Technical Reports Server (NTRS)

Naegeli, D. W.; Moses, C. A.

1979-01-01

A high pressure research combustor operating over a wide range of burner inlet conditions was used to determine the effects of fuel molecular structure on soot formation. Six test fuels with equal hydrogen content (12.8%) were blended to stress different molecular components and final boiling points. The fuels containing high concentrations (20%) of polycyclic aromatics and partially saturated polycyclic structures such as tetralin, produced more soot than would be expected from a hydrogen content correlation for typical petroleum based fuels. Fuels containing naphthenes such as decalin agreed with the hydrogen content correlation. The contribution of polycyclic aromatics to soot formation was equivalent to a reduction in fuel hydrogen content of about one percent. The fuel sensitivity to soot formation due to the polycyclic aromatic contribution decreased as burner inlet pressure and fuel/air ratio increased.

Prediction of induction time for methane hydrate formation in the presence or absence of THF in flow loop system by Natarajan model

NASA Astrophysics Data System (ADS)

Talaghat, Mohammad Reza; Jokar, Seyyed Mohammad

2018-03-01

The induction time is a time interval to detect the initial hydrate formation, which is counted from the moment when the stirrer is turned on until the first detection of hydrate formation. The main objective of the present work is to predict and measure the induction time of methane hydrate formation in the presence or absence of tetrahydrofuran (THF) as promoter in the flow loop system. A laboratory flow mini-loop apparatus was set up to measure the induction time of methane hydrate formation. The induction time is predicted using developed Kashchiev and Firoozabadi model and modified model of Natarajan for a flow loop system. Furthermore, the effects of volumetric flow rate of the fluid on the induction time were investigated. The results of the models were compared with experimental data. They show that the induction time of hydrate formation in the presence of THF is very short at high pressure and high volumetric flow rate of the fluid. It decreases with increasing pressure and liquid volumetric flow rate. It is also shown that the modified Natarajan model is more accurate than the Kashchiev and Firoozabadi ones in prediction of the induction time.

Artesian pressures and water quality in Paleozoic aquifers in the Ten Sleep area of the Bighorn Basin, north-central Wyoming

USGS Publications Warehouse

Cooley, Maurice E.

1986-01-01

The major Paleozoic artesian aquifers, the aquifers most favorable for continued development, in the Ten Sleep area of the Bighorn Basin of Wyoming are the Tensleep Sandstone, the Madison Limestone and Bighorn Dolomite (Madison-Bighorn aquifer), and the Flathead Sandstone. The minor aquifers include the Goose Egg and Park City Formations (considered in the Ten Sleep area to be the lateral equivalent of the Phosphoria Formation) and the Amsden Formation. Most wells completed in the major and minor aquifers flow at the land surface. Wellhead pressures generally are less than 50 pounds per square inch for the Tensleep Sandstone, 150-250 pounds per square inch for the Madison-Bighorn aquifer, and more than 400 pounds per square inch for the Flathead Sandstone. Flowing wells completed in the Madison-Bighorn aquifer and the Flathead Sandstone yield more than 1,000 gallons per minute. The initial test of one well completed in the Madison-Bighorn aquifer indicated a flow rate of 14,000 gallons per minute. Transmissivities range from 500 to 1,900 feet squared per day for the Madison-Bighorn aquifer and from about 90 to 325 feet squared per day for the Tensleep and Flathead Sandstones. Significant secondary permeability from fracturing in the Paleozoic aquifers allows local upward interformational movement of water, and this affects the altitude of the potentiometric surfaces of the Tensleep Sandstone and the Madison-Bighorn aquifer. Water moves upward from the Tensleep and other formations, through the Goose Egg Formation, to discharge at the land surface as springs. Much of the spring flow is diverted for irrigation or is used for rearing fish. Decreases from original well pressures were not apparent in wells completed in the Tensleep Sandstone or in the Madison-Bighorn aquifer in the study area except for a few wells in or near the town of Ten Sleep. Most wells completed in the Flathead Sandstone, which also are open to the Madison-Bighorn aquifer, show a decrease of pressure from the time of completion to 1978. The decrease of pressure is partly the result of water moving from the Flathead Sandstone into the Madison-Bighorn aquifer, which has a lower potentiometric surface than does the Flathead Sandstone, even during the time the wells are not in operation. Pressure in some small-capacity wells completed in the Goose Egg Formation also has decreased near Ten Sleep. Most of the wells, particularly the irrigation wells, show a progressive decrease in pressure during the irrigation season but recover during periods of nonuse. Measurements of the pressure were made principally in 1953, 1962, 1970, and 1975-78. Well water from the Paleozoic aquifers generally contains minimal concentrations of dissolved solids and individual constituents but excessive hardness. Dissolved-solids concentrations of water are less than 300 milligrams per liter in the Tensleep Sandstone and the Madison-Bighorn aquifer, less than 200 milligrams per liter in the Flathead Sandstone, and as much as 450 milligrams per liter in the Goose Egg Formation. Bicarbonate is the major constituent, followed by calcium and magnesium. Relatively large concentrations of sulfate, as much as 490 milligrams per liter, were found, mainly in water from the Goose Egg Formation. The water has low sodium (alkali) and medium salinity; therefore, the water is satisfactory for irrigation and most other uses, if excessive hardness is not a detrimental factor. Wellhead temperatures range from 11 ? to 27.5 ? Celsius (51 ? to 81.5 ? Fahrenheit) within a range in depth of approximately 250 to 4,000 feet. This gives a geothermal gradient of about 0.44 ? Celsius per 100 feet (0.79 ? Fahrenheit per 100 feet).

Effects of environmental gas compression on the multiphase ISM and star formation . The Virgo spiral galaxies NGC 4501 and NGC 4567/68

NASA Astrophysics Data System (ADS)

Nehlig, F.; Vollmer, B.; Braine, J.

2016-03-01

The cluster environment can affect galaxy evolution in different ways: via ram pressure stripping or by gravitational perturbations caused by galactic encounters. Both kinds of interactions can lead to the compression of the interstellar medium (ISM) and its associated magnetic fields, causing an increase in the gas surface density and the appearance of asymmetric ridges of polarized radio continuum emission. New IRAM 30m HERA CO(2-1) data of NGC 4501, a Virgo spiral galaxy currently experiencing ram pressure stripping, and NGC 4567/68, an interacting pair of galaxies in the Virgo cluster, are presented. We find an increase in the molecular fraction where the ISM is compressed. The gas is close to self-gravitation in compressed regions. This leads to an increase in gas pressure and a decrease in the ratio between the molecular fraction and total ISM pressure. The overall Kennicutt Schmidt relation based on a pixel-by-pixel analysis at ~1.5 kpc resolution is not significantly modified by compression. However, we detected continuous regions of low molecular star formation efficiencies in the compressed parts of the galactic gas disks. The data suggest that a relation between the molecular star formation efficiency SFEH2 = SFR/M(H2) and gas self-gravitation (Rmol/Ptot and Toomre Q parameter) exists. Both systems show spatial variations in the star formation efficiency with respect to the molecular gas that can be related to environmental compression of the ISM. An analytical model was used to investigate the dependence of SFEH2 on self-gravitation. The model correctly reproduces the correlations between Rmol/Ptot, SFEH2, and Q if different global turbulent velocity dispersions are assumed for the three galaxies. We found that variations in the NH2/ICO conversion factor can mask most of the correlation between SFEH2 and the Toomre Q parameter. Dynamical simulations were used to compare the effects of ram pressure and tidal ISM compression. These models give direct access to the volume density. We conclude that a gravitationally induced ISM compression has the same consequences as ram pressure compression: (I) an increasing gas surface density; (II) an increasing molecular fraction; and (III) a decreasing Rmol/Ptot in the compressed region due to the presence of nearly self-gravitating gas. The response of SFEH2 to compression is more complex. While in the violent ISM-ISM collisions (e.g., Taffy galaxies and NGC 4438) the interaction makes star formation drop by an order of magnitude, we only detect an SFEH2 variation of ~50% in the compressed regions of the three galaxies. We suggest that the decrease in star formation depends on the ratio between the compression timescale and the turbulent dissipation timescale. In NGC 4501 and NGC 4567/68 the compression timescale is comparable to the turbulent dissipation timescale and only leads to minor changes in the molecular star formation efficiency.

Effect of inlet-air humidity, temperature, pressure, and reference Mach number on the formation of oxides of nitrogen in a gas turbine combustor

NASA Technical Reports Server (NTRS)

Marchionna, N. R.; Diehl, L. A.; Trout, A. M.

1973-01-01

Tests were conducted to determine the effect of inlet air humidity on the formation of oxides of nitrogen (NOx) from a gas turbine combustor. Combustor inlet air temperature ranged from 506 K (450 F) to 838 K (1050 F). The tests were primarily run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NOx emission index was found to decrease with increasing inlet air humidity at a constant exponential rate: NOx = NOx0e-19H (where H is the humidity and the subscript 0 denotes the value at zero humidity). the emission index increased exponentially with increasing normalized inlet air temperature to the 1.14 power. Additional tests made to determine the effect of pressure and reference Mach number on NOx showed that the NOx emission index varies directly with pressure to the 0.5 power and inversely with reference Mach number.

Downhole steam generator using low pressure fuel and air supply

DOEpatents

Fox, Ronald L.

1983-01-01

An apparatus for generation of steam in a borehole for penetration into an earth formation wherein a spiral, tubular heat exchanger is used in the combustion chamber to isolate the combustion process from the water being superheated for conversion into steam. The isolation allows combustion of a relatively low pressure oxidant and fuel mixture for generating high enthalpy steam. The fuel is preheated by feedback of combustion gases from the top of the combustion chamber through a fuel preheater chamber. The hot exhaust gases of combustion at the bottom of the combustion chamber, after flowing over the heat exchanger enter an exhaust passage and pipe. The exhaust pipe is mounted inside the water supply line heating the water flowing into the heat exchanger. After being superheated in the heat exchanger, the water is ejected through an expansion nozzle and converts into steam prior to penetration into the earth formation. Pressure responsive doors are provided at a steam outlet downstream of the nozzle and close when the steam pressure is lost due to flameout.

Drilling plastic formations using highly polished PDC cutters

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

Smith, R.H.; Lund, J.B.; Anderson, M.

1995-12-31

Highly plastic and over-pressured formations are troublesome for both roller cone and PDC bits. Thus far, attempts to increase penetration rates in these formations have centered around re-designing the bit or modifying the cutting structure. These efforts have produced only moderate improvements. This paper presents both laboratory and field data to illustrate the benefits of applying a mirror polished surface to the face of PDC cutters in drilling stressed formations. These cutters are similar to traditional PDC cutters, with the exception of the reflective mirror finish, applied to the diamond table surfaces prior to their installation in the bit. Resultsmore » of tests conducted in a single point cutter apparatus and a full-scale drilling simulator will be presented and discussed. Field results will be presented that demonstrate the effectiveness of polished cutters, in both water and oil-based muds. Increases in penetration rates of 300-400% have been observed in the Wilcox formation and other highly pressured shales. Typically, the beneficial effects of polished cutters have been realized at depths greater than 7000 ft, and with mud weights exceeding 12 ppg.« less

NOx formation in apokamp-type atmospheric pressure plasma jets in air initiated by a pulse-repetitive discharge

NASA Astrophysics Data System (ADS)

Sosnin, Eduard A.; Didenko, Maria V.; Panarin, Victor A.; Skakun, Victor S.; Tarasenko, Victor F.; Liu, Dongping P.; Song, Ying

2018-04-01

The decomposition products of atmospheric pressure plasma of repetitive pulsed discharge in apokamp and corona modes were determined by optical and chemical methods. It is shown, that the decomposition products contain mainly nitrogen oxides NOx. A brief review of the plasma- and thermochemical reactions in the pulsed discharges was made. The review and experimental data allow us to explain the reactive oxygen species formation mechanisms in a potential discharge channel with apokamp. The possible applications of this plasma source for treatment of seeds of agricultural crops are discussed.

Methylene blue prevents surgery-induced peritoneal adhesions but impairs the early phase of anastomotic wound healing

PubMed Central

Dinc, Soykan; Ozaslan, Cihangir; Kuru, Bekir; Karaca, Sefa; Ustun, Huseyin; Alagol, Haluk; Renda, Nurten; Oz, Murat

2006-01-01

Objectives Adhesion formation continues to be an important problem in gastrointestinal surgery. In recent years, methylene blue (MB) has been reported to be an effective agent for preventing peritoneal adhesions. However, its effects on the wound healing process are unknown. In the present study, we investigated the effects of MB on the early and late phases of anastomotic wound healing and on adhesion formation. Methods We randomly categorized 92 rats into 2 groups in bursting pressure measurements and 50 rats into 3 groups in the adhesion model. We divided the animals into saline-treated (n = 46) or MB-treated (n = 46) groups. Bursting pressures of the anastomoses were measured on postoperative days 3 and 7. In biochemical studies, tissue hydroxyproline levels, total nitrite/nitrate levels and nitric oxide synthase activity were measured on postoperative days 3 and 7. In the adhesion model, we randomly categorized rats into sham (n = 10), saline-treated (n = 20) and MB-treated (n = 20) groups, and the formation of intraperitoneal adhesions was scored on postoperative day 14. We compared the measurement of bursting pressure and biochemical measurements of tissue hydroxyproline levels, total nitrite/nitrate levels and nitric oxide synthase activity. Histopathological findings of specimens were presented. Results During the early phase of wound healing (postoperative day 3), bursting pressures, tissue hydroxyproline, total nitrite/nitrate levels and nitric oxide synthase activity in the MB-treated group were significantly lower than those of the saline-treated group. On postoperative day 7, there was no significant difference in these parameters between MB and saline-treated groups. In the adhesion model, MB caused a significant reduction in the formation of peritoneal adhesions. Conclusion MB prevents peritoneal adhesions but causes a significant impairment of anastomotic bursting pressure during the early phase of the wound healing process by its transient inhibitory effect on the nitric oxide pathway. PMID:17152569

Use of Anticlines for Geologic Sequestration of Carbon Dioxide in a Saline Aquifer in Northwestern Taiwan

NASA Astrophysics Data System (ADS)

Lin, Shin-Hsun; Liou, Tai-Sheng

2013-04-01

In this study, migration of CO2 in a deep saline aquifer with anticlines under various injection schemes was numerically simulated using the ECO2N simulator. The hypothetical study site was selected at the Taoyuan Plateau near the second largest coal-fired power plant, Datan power plant (annual CO2 emission of 1.5 Mt/yr), in Northwestern Taiwan. A 15x15 km2 simulation domain, containing two sub-parallel east-northeast Hukou and Pingzhen anticlines, was discretized into unstructured grid with spatial refinement at the injection borehole. Kueichulin sandstone and Chinshui shale in the simulation domain were considered as the storage formation and the cap rock, respectively. It was assumed that no CO2 exists in the aquifer prior to injection, and that the aquifer has a hydrostatic pressure distribution and a constant salinity of 3%. All boundaries were assumed to be "open". Isothermal simulations with 1 Mt/yr injection rate and 20 years of injection period were considered. van Genuchten capillary pressure and Corey relative permeability were assumed for all rock formations. Simulation results indicated that pressure buildup characterized the CO2 migration into three different phases: drainage of brine, formation dry-out, and dissolution and gravity take-over . It was found that the worst leakage scenario occurs if a single injection borehole is placed along the anticline axis. In this case, rock formations near the anticline axis provide a leakage path such that CO2 ultimately leaks out of the upper boundary. On the other hand, CO2 can be safely sequestrated in the storage formation if the injection borehole was placed away from the anticline axis. This is because gas phase CO2 migrates along the counter dipping direction of the anticline as a result of buoyancy. More favorable scenarios were found if a multiple-borehole injection scheme was used. In such cases, not only pressure buildup was significantly mitigated but the amount of precipitated salt was reduced. If a five-borehole scheme was used, for example, pressure buildup and the amount of precipitated salt can be reduced by 20% and 90%, respectively. More interestingly, if injection borehole was placed midway between the two anticlines, buoyancy dominates the migration of CO2 such that most CO2 is accumulated under the apex of anticline. Therefore, it is suggested that a multiple-borehole injection scheme would be a preferable scenario because of the reduced risks of pressure buildup and salt precipitation. Moreover, it would be better to place the injection boreholes away from the anticline axis in order to make good use of all possible trapping mechanisms to permanently sequestrate CO2 in deep rock formations.

DIPPR Project 871 For 1995 - Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for Methyl Benzoate, Ethyl Benzoate, (R)-(+)-Limonene, Tert-Amyl Methyl Ether, Trans-Crotonaldehyde, and

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

Steele, W.V.

2002-07-01

Ideal-gas enthalpies of formation of methyl benzoate, ethyl benzoate, (R)-(+)-limonene, tert-amyl methyl ether, trans-crotonaldehyde, and diethylene glycol are reported. The standard energy of combustion and hence standard enthalpy of formation of each compound in the liquid phase has been measured using an oxygen rotating-bomb calorimeter without rotation. Vapor pressures were measured to a pressure limit of 270 kPa or the lower decomposition point for each of the six compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperature (ambient to a maximum of 548 K). A differential scanningmore » calorimeter was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. For methyl benzoate and tert-amyl methyl ether, critical temperatures and critical densities were determined from the DSC results and corresponding critical pressures derived from the fitting procedures. Fitting procedures were used to derive critical temperatures, critical pressures, and critical densities for each of the remaining compounds. The results of the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization (restricted to within {+-}50 K of the temperature region of the experimentally determined vapor pressures), and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. All measured and derived values were compared with those obtained in a search of the literature. Recommended critical parameters are listed for each of the compounds studied. Group-additivity parameters, useful in the application of the Benson gas-phase group-contribution correlations, were derived.« less

Transient pressure analysis of a volume fracturing well in fractured tight oil reservoirs

NASA Astrophysics Data System (ADS)

Lu, Cheng; Wang, Jiahang; Zhang, Cong; Cheng, Minhua; Wang, Xiaodong; Dong, Wenxiu; Zhou, Yingfang

2017-12-01

This paper presents a semi-analytical model to simulate transient pressure curves for a vertical well with a reconstructed fracture network in fractured tight oil reservoirs. In the proposed model, the reservoir is a composite system and contains two regions. The inner region is described as a formation with a finite conductivity hydraulic fracture network and the flow in the fracture is assumed to be linear, while the outer region is modeled using the classical Warren-Root model where radial flow is applied. The transient pressure curves of a vertical well in the proposed reservoir model are calculated semi-analytically using the Laplace transform and Stehfest numerical inversion. As shown in the type curves, the flow is divided into several regimes: (a) linear flow in artificial main fractures; (b) coupled boundary flow; (c) early linear flow in a fractured formation; (d) mid radial flow in the semi-fractures of the formation; (e) mid radial flow or pseudo steady flow; (f) mid cross-flow; (g) closed boundary flow. Based on our newly proposed model, the effects of some sensitive parameters, such as elastic storativity ratio, cross-flow coefficient, fracture conductivity and skin factor, on the type curves were also analyzed extensively. The simulated type curves show that for a vertical fractured well in a tight reservoir, the elastic storativity ratios and crossflow coefficients affect the time and the degree of crossflow respectively. The pressure loss increases with an increase in the fracture conductivity. To a certain extent, the effect of the fracture conductivity is more obvious than that of the half length of the fracture on improving the production effect. With an increase in the wellbore storage coefficient, the fluid compressibility is so large that it might cover the early stage fracturing characteristics. Linear or bilinear flow may not be recognized, and the pressure and pressure derivative gradually shift to the right. With an increase in the skin effect, the pressure loss increases gradually.

Molten Boron Phase-Change Thermal Energy Storage to Augment Solar Thermal Propulsion Systems

DTIC Science & Technology

2011-07-22

during the 50 psi case included bubble clouds somewhat similar to the " popcorn " and "jellyfish" formations observed at ambient-pressure conditions...between the "jellyfish" and " popcorn " was lost -- popcorn formations were generally longer-lived, often traversing a significant portion of the field of... popcorn -like bubbles were generally swirling in/around the jellyfish formations. The turbulent wake of some of the jellyfish-like formations could

A first-principles study of the structural, mechanical and electronic properties of precipitates of Al2Cu in Al-Cu alloys.

PubMed

Ouyang, Y F; Chen, H M; Tao, X M; Gao, F; Peng, Q; Du, Y

2018-01-03

The properties of precipitates are important in understanding the strengthening mechanism via precipitation during heat treatment and the aging process in Al-Cu based alloys, where the formation of precipitates is sensitive to temperature and pressure. Here we report a first-principles investigation of the effect of temperature and pressure on the structural stability, elastic constants and formation free energy for precipitates of Al 2 Cu, as well as their mechanical properties. Based on the formation enthalpy of Guinier-Preston (GP(I)) zones, the size of the GP(I) zone is predicted to be about 1.4 nm in diameter, which is in good agreement with experimental observations. The formation enthalpies of the precipitates are all negative, suggesting that they are all thermodynamically stable. The present calculations reveal that entropy plays an important role in stabilizing θ-Al 2 Cu compared with θ C '-Al 2 Cu. The formation free energies of θ''-Al 3 Cu, θ C '-Al 2 Cu, θ D '-Al 5 Cu 3 and θ t '-Al 11 Cu 7 increase with temperature, while those of θ'-Al 2 Cu, θ O '-Al 2 Cu and θ-Al 2 Cu decrease. The same trend is observed with the effect of pressure. The calculated elastic constants for the considered precipitation phases indicate that they are all mechanically stable and anisotropic, except θ C '-Al 2 Cu. θ D '-Al 5 Cu 3 has the highest Vicker's hardness. The electronic structures are also calculated to gain insight into the bonding characteristics. The present results can help in understanding the formation of precipitates by different treatment processes.

76 FR 2726 - Withdrawal of Regulatory Guide 1.154

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-14

... NUCLEAR REGULATORY COMMISSION [NRC-2011-0010] Withdrawal of Regulatory Guide 1.154 AGENCY: Nuclear Regulatory Commission. ACTION: Withdrawal of Regulatory Guide 1.154, ``Format and Content of Plant-Specific Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water Reactors.'' FOR FURTHER INFORMATION CONTACT: Mekonen M. Bayssie,...

Understanding the Links among the Magnetic Fields, Filament, Bipolar Bubble, and Star Formation in RCW 57A Using NIR Polarimetry

NASA Astrophysics Data System (ADS)

Eswaraiah, Chakali; Lai, Shih-Ping; Chen, Wen-Ping; Pandey, A. K.; Tamura, M.; Maheswar, G.; Sharma, S.; Wang, Jia-Wei; Nishiyama, S.; Nakajima, Y.; Kwon, Jungmi; Purcell, R.; Magalhães, A. M.

2017-12-01

The influence of magnetic fields (B-fields) on the formation and evolution of bipolar bubbles, due to the expanding ionization fronts (I-fronts) driven by the H II regions that are formed and embedded in filamentary molecular clouds, has not been well-studied yet. In addition to the anisotropic expansion of I-fronts into a filament, B-fields are expected to introduce an additional anisotropic pressure, which might favor the expansion and propagation of I-fronts forming a bipolar bubble. We present results based on near-infrared polarimetric observations toward the central ˜8‧ × 8‧ area of the star-forming region RCW 57A, which hosts an H II region, a filament, and a bipolar bubble. Polarization measurements of 178 reddened background stars, out of the 919 detected sources in the JHK s bands, reveal B-fields that thread perpendicularly to the filament long axis. The B-fields exhibit an hourglass morphology that closely follows the structure of the bipolar bubble. The mean B-field strength, estimated using the Chandrasekhar-Fermi method (CF method), is 91 ± 8 μG. B-field pressure dominates over turbulent and thermal pressures. Thermal pressure might act in the same orientation as the B-fields to accelerate the expansion of those I-fronts. The observed morphological correspondence among the B-fields, filament, and bipolar bubble demonstrate that the B-fields are important to the cloud contraction that formed the filament, to the gravitational collapse and star formation in it, and in feedback processes. The last one includes the formation and evolution of mid-infrared bubbles by means of B-field supported propagation and expansion of I-fronts. These may shed light on preexisting conditions favoring the formation of the massive stellar cluster in RCW 57A.

Low pressure-induced secondary structure transitions of regenerated silk fibroin in its wet film studied by time-resolved infrared spectroscopy.

PubMed

He, Zhipeng; Liu, Zhao; Zhou, Xiaofeng; Huang, He

2018-06-01

The secondary structure transitions of regenerated silk fibroin (RSF) under different external perturbations have been studied extensively, except for pressure. In this work, time-resolved infrared spectroscopy with the attenuated total reflectance (ATR) accessory was employed to follow the secondary structure transitions of RSF in its wet film under low pressure. It has been found that pressure alone is favorable only to the formation of β-sheet structure. Under constant pressure there is an optimum amount of D 2 O in the wet film (D 2 O : film = 2:1) so as to provide the optimal condition for the reorganization of the secondary structure and to have the largest formation of β-sheet structure. Under constant amount of D 2 O and constant pressure, the secondary structure transitions of RSF in its wet film can be divided into three stages along with time. In the first stage, random coil, α-helix, and β-turn were quickly transformed into β-sheet. In the second stage, random coil and β-turn were relatively slowly transformed into β-sheet and α-helix, and the content of α-helix was recovered to the value prior to the application of pressure. In the third and final stage, no measurable changes can be found for each secondary structure. This study may be helpful to understand the secondary structure changes of silk fibroin in silkworm's glands under hydrostatic pressure. © 2018 Wiley Periodicals, Inc.

GSOD Based Daily Global Mean Surface Temperature and Mean Sea Level Air Pressure (1982-2011)

DOE Data Explorer

Xuan Shi, Dali Wang

2014-05-05

This data product contains all the gridded data set at 1/4 degree resolution in ASCII format. Both mean temperature and mean sea level air pressure data are available. It also contains the GSOD data (1982-2011) from NOAA site, contains station number, location, temperature and pressures (sea level and station level). The data package also contains information related to the data processing methods

Development of a low pressure microwave excited plasma and its application to the formation of microcrystalline silicon films

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

Kikukawa, Daisuke; Hori, Masaru; Honma, Koichiro

2006-11-15

Microwave excited plasma source operating at a low pressure of 1.5 Pa was newly developed. This plasma source was successfully applied to the formation of hydrogenated microcrystalline silicon films in a glass substrate with a mixture gas of silane (SiH{sub 4}), hydrogen (H{sub 2}), and xenon (Xe). It was found that the crystallinity of films was dramatically improved with decreasing pressure. The crystalline fraction was evaluated to be 82% at a substrate temperature of 400 deg. C, a mixture gas of SiH{sub 4}/H{sub 2}/Xe: 5/200/30 SCCM, and a total pressure of 1.5 Pa by Raman spectroscopy. The absolute density ofmore » hydrogen atoms and the behavior of higher radicals and molecules in the mixture gas were evaluated using vacuum ultraviolet absorption spectroscopy and quadrupole mass spectrometer, respectively. H atom densities were of the order of 10{sup 11} cm{sup -3}. The fraction of H atom density increased, while higher radicals and molecules decreased with decrease in the total pressure. The increase in H atom density and decrease in higher radicals and molecules improved the crystallinity of films in low pressures below 10 Pa.« less

The shock formation distance in a bounded sound beam of finite amplitude.

PubMed

Tao, Chao; Ma, Jian; Zhu, Zhemin; Du, Gonghuan; Ping, Zihong

2003-07-01

This paper investigates the shock formation distance in a bounded sound beam of finite amplitude by solving the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation using frequency-domain numerical method. Simulation results reveal that, besides the nonlinearity and absorption, the diffraction is another important factor that affects the shock formation of a bounded sound beam. More detailed discussions of the shock formation in a bounded sound beam, such as the waveform of sound pressure and the spatial distribution of shock formation, are also presented and compared for different parameters.

Hydraulic impulse generator and frequency sweep mechanism for borehole applications

DOEpatents

Kolle, Jack J.; Marvin, Mark H.; Theimer, Kenneth J.

2006-11-21

This invention discloses a valve that generates a hydraulic negative pressure pulse and a frequency modulator for the creation of a powerful, broadband swept impulse seismic signal at the drill bit during drilling operations. The signal can be received at monitoring points on the surface or underground locations using geophones. The time required for the seismic signal to travel from the source to the receiver directly and via reflections is used to calculate seismic velocity and other formation properties near the source and between the source and receiver. This information can be used for vertical seismic profiling of formations drilled, to check the location of the bit, or to detect the presence of abnormal pore pressure ahead of the bit. The hydraulic negative pressure pulse can also be used to enhance drilling and production of wells.

Time-resolved microscopy reveals the driving mechanism of particle formation during ultrashort pulse laser ablation of dentin-like ivory

NASA Astrophysics Data System (ADS)

Domke, Matthias; Gavrilova, Anna; Rapp, Stephan; Frentzen, Matthias; Meister, Joerg; Huber, Heinz P.

2015-07-01

In dental health care, the application of ultrashort laser pulses enables dental tissue ablation free from thermal side effects, such as melting and cracking. However, these laser types create undesired micro- and nanoparticles, which might cause a health risk for the patient or surgeon. The aim of this study was to investigate the driving mechanisms of micro- and nanoparticle formation during ultrashort pulse laser ablation of dental tissue. Time-resolved microscopy was chosen to observe the ablation dynamics of mammoth ivory after irradiation with 660 fs laser pulses. The results suggest that nanoparticles might arise in the excited region. The thermal expansion of the excited material induces high pressure in the surrounding bulk tissue, generating a pressure wave. The rarefaction wave behind this pressure wave causes spallation, leading to ejection of microparticles.

[Complex formation between alpha-chymotrypsin and block copolymers based on ethylene and propylene oxide, induced by high pressure].

PubMed

Topchieva, I N; Sorokina, E M; Kurganov, B I; Zhulin, V M; Makarova, Z G

1996-06-01

A new method of formation of non-covalent adducts based on an amphiphilic diblock copolymer of ethylene and propylene oxides with molecular mass of 2 kDa and alpha-chymotrypsin (ChT) under high pressure, has been developed. The composition of the complexes corresponds to seven polymer molecules per one ChT molecule in the pressure range of 1.1 to 400 MPa. The complexes fully retain the catalytic activity. Kinetic constants (Km and kcat) for enzymatic hydrolysis of N-benzoyl-L-tyrosine ethyl ester catalyzed by the complexes are identical with the corresponding values for native ChT. Analysis of kinetics of thermal inactivation of the complexes revealed that the constant of the rate of the slow inactivation step is markedly lower than for ChT.

Discovery of massive star formation quenching by non-thermal effects in the centre of NGC 1097

NASA Astrophysics Data System (ADS)

Tabatabaei, F. S.; Minguez, P.; Prieto, M. A.; Fernández-Ontiveros, J. A.

2018-01-01

Observations show that massive star formation quenches first at the centres of galaxies. To understand quenching mechanisms, we investigate the thermal and non-thermal energy balance in the central kpc of NGC 1097—a prototypical galaxy undergoing quenching—and present a systematic study of the nuclear star formation efficiency and its dependencies. This region is dominated by the non-thermal pressure from the magnetic field, cosmic rays and turbulence. A comparison of the mass-to-magnetic flux ratio of the molecular clouds shows that most of them are magnetically critical or supported against the gravitational collapse needed to form the cores of massive stars. Moreover, the star formation efficiency of the clouds drops with the magnetic field strength. Such an anti-correlation holds with neither the turbulent nor the thermal pressure. Hence, a progressive build up of the magnetic field results in high-mass stars forming inefficiently, and this may be the cause of the low-mass stellar population in the bulges of galaxies.

Fiber optic sensing technology for detecting gas hydrate formation and decomposition.

PubMed

Rawn, C J; Leeman, J R; Ulrich, S M; Alford, J E; Phelps, T J; Madden, M E

2011-02-01

A fiber optic-based distributed sensing system (DSS) has been integrated with a large volume (72 l) pressure vessel providing high spatial resolution, time-resolved, 3D measurement of hybrid temperature-strain (TS) values within experimental sediment-gas hydrate systems. Areas of gas hydrate formation (exothermic) and decomposition (endothermic) can be characterized through this proxy by time series analysis of discrete data points collected along the length of optical fibers placed within a sediment system. Data are visualized as an animation of TS values along the length of each fiber over time. Experiments conducted in the Seafloor Process Simulator at Oak Ridge National Laboratory clearly indicate hydrate formation and dissociation events at expected pressure-temperature conditions given the thermodynamics of the CH(4)-H(2)O system. The high spatial resolution achieved with fiber optic technology makes the DSS a useful tool for visualizing time-resolved formation and dissociation of gas hydrates in large-scale sediment experiments.

Fiber optic sensing technology for detecting gas hydrate formation and decomposition

NASA Astrophysics Data System (ADS)

Rawn, C. J.; Leeman, J. R.; Ulrich, S. M.; Alford, J. E.; Phelps, T. J.; Madden, M. E.

2011-02-01

A fiber optic-based distributed sensing system (DSS) has been integrated with a large volume (72 l) pressure vessel providing high spatial resolution, time-resolved, 3D measurement of hybrid temperature-strain (TS) values within experimental sediment-gas hydrate systems. Areas of gas hydrate formation (exothermic) and decomposition (endothermic) can be characterized through this proxy by time series analysis of discrete data points collected along the length of optical fibers placed within a sediment system. Data are visualized as an animation of TS values along the length of each fiber over time. Experiments conducted in the Seafloor Process Simulator at Oak Ridge National Laboratory clearly indicate hydrate formation and dissociation events at expected pressure-temperature conditions given the thermodynamics of the CH4-H2O system. The high spatial resolution achieved with fiber optic technology makes the DSS a useful tool for visualizing time-resolved formation and dissociation of gas hydrates in large-scale sediment experiments.

Generation of field-aligned current (FAC) and convection through the formation of pressure regimes: Correction for the concept of Dungey's convection

NASA Astrophysics Data System (ADS)

Tanaka, T.; Watanabe, M.; Den, M.; Fujita, S.; Ebihara, Y.; Kikuchi, T.; Hashimoto, K. K.; Kataoka, R.

2016-09-01

In this paper, we try to elucidate the generation mechanism of the field-aligned current (FAC) and coexisting convection. From the comparison between the theoretical prediction and the state of numerical solution from the high-resolution global simulation, we obtain the following conclusions about the distribution of dynamo, the magnetic field structure along the flow path that diverges Poynting flux, and energy conversion promoting the generation of electromagnetic energy. The dynamo for the region 1 FAC, which is in the high-latitude-side cusp-mantle region, has a structure in which magnetic field is compressed along the convection path by the slow mode motion. The dynamo for the region 2 FAC is in the ring current region at the inner edge of the plasma sheet, and has a structure in which magnetic field is curved outward along the convection path. Under these structures, electromagnetic energy is generated from the work done by pressure gradient force, in both dynamos for the region 1 and region 2 FACs. In these generation processes of the FACs, the excitation of convection and the formation of pressure regimes occur as interdependent processes. This structure leads to a modification in the way of understanding the Dungey's convection. Generation of the FAC through the formation of pressure regimes is essential even for the case of substorm onset.

Prebreakdown phenomena and formation process of the glow discharge in low-pressure Ar gas

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

Hosokawa, Tatsuzo; Goto, Kazuhiro; Ohuchi, Mikio

2001-06-01

The prebreakdown phenomena and the formation process of the glow discharge in a low-pressure Ar gas were investigated under a uniform field gap. Prebreakdown phenomena were observed for 0.5Torrcm{le}pd{le}2Torrcm (where p is pressure, d the gap distance) in Ar gas under conditions of a slowly increasing voltage. It was observed that the prebreakdown phenomena formed pulse discharges up to the transition to the glow discharge. The amplitudes of the photon and current pulses due to the pulse discharge increased with time, and then decreased as soon as the transition to a steady glow discharge occurred. When the overvoltage or externalmore » series resistance was increased, the pulse amplitudes increased with the applied voltage and decreased with the resistance. The characteristics of the prebreakdown phenomena were changed by the shape of the electrodes. The formation mechanism of the glow discharge can be qualitatively explained by that of the streamer in a high-pressure discharge. The transient glow discharge was observed, and its duration increased with an increase in resistance. The instability of the glow discharge was controlled by three factors, namely, Kaufmann{close_quote}s criterion, the Child{endash}Langmuir law, and the density balance between the production and removal rates of electrons. {copyright} 2001 American Institute of Physics.« less

Model for the formation of the earth's core

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

McCammon, C.A.; Ringwood, A.E.; Jackson, I.

1983-02-15

The recent discovery of a phase transformation in Fe/sub 0.94/O by Jeanloz and Ahrens has allowed a more detailed development of a model for core formation involving oxygen as the principal light alloying element in the core. It is predicted, based on calculations, that an increasing pressure in the system FeO-MgO will result in a gradual exsolution of an almost pure high-pressure phase FeO(hpp), leaving an iron-depleted (Fe,Mg)O rocksalt (B1) phase. We also predict that FeO(hhp) will form a low-melting point alloy with Fe at high temperature and high pressure. On the basis of our interpretations, we have constructed amore » model for core segregation. Assuming the earth to have accreted from the primordial solar nebula as a relatively homogeneous mixture of metallic iron and silicate-oxide phases, core segregation involving oxygen would commence at a depth where pressure is sufficiently high to cause exsolution of FeO(hpp) from the rocksalt phase, and temperature is sufficiently high to allow formation of an Fe-FeO(hpp) melt. A gravitational instability arises, leading to vertical differentiation of the earth as molten blobs of the metal sink downwards to form the core and the residual depleted silicate material coalesces to form large bodies which rise diapirically upwards to form the mantle.« less

Cosmic ray driven outflows in an ultraluminous galaxy

NASA Astrophysics Data System (ADS)

Fujita, Akimi; Mac Low, Mordecai-Mark

2018-06-01

In models of galaxy formation, feedback driven both by supernova (SN) and active galactic nucleus is not efficient enough to quench star formation in massive galaxies. Models of smaller galaxies have suggested that cosmic rays (CRs) play a major role in expelling material from the star-forming regions by diffusing SN energy to the lower density outskirts. We therefore run gas dynamical simulations of galactic outflows from a galaxy contained in a halo with 5 × 1012 M⊙ that resembles a local ultraluminous galaxy, including both SN thermal energy and a treatment of CRs using the same diffusion approximation as Salem & Bryan. We find that CR pressure drives a low-density bubble beyond the edge of the shell swept up by thermal pressure, but the main bubble driven by SN thermal pressure overtakes it later, which creates a large-scale biconical outflow. CRs diffusing into the disc are unable to entrain its gas in the outflows, yielding a mass-loading rate of only ˜ 0.1 per cent with varied CR diffusion coefficients. We find no significant difference in mass-loading rates in SN-driven outflows with or without CR pressure. Our simulations strongly suggest that it is hard to drive a heavily mass-loaded outflow with CRs from a massive halo potential, although more distributed star formation could lead to a different result.

Transdermal deferoxamine prevents pressure-induced diabetic ulcers

PubMed Central

Duscher, Dominik; Neofytou, Evgenios; Wong, Victor W.; Maan, Zeshaan N.; Rennert, Robert C.; Januszyk, Michael; Rodrigues, Melanie; Malkovskiy, Andrey V.; Whitmore, Arnetha J.; Galvez, Michael G.; Whittam, Alexander J.; Brownlee, Michael; Rajadas, Jayakumar; Gurtner, Geoffrey C.

2015-01-01

There is a high mortality in patients with diabetes and severe pressure ulcers. For example, chronic pressure sores of the heels often lead to limb loss in diabetic patients. A major factor underlying this is reduced neovascularization caused by impaired activity of the transcription factor hypoxia inducible factor-1 alpha (HIF-1α). In diabetes, HIF-1α function is compromised by a high glucose-induced and reactive oxygen species-mediated modification of its coactivator p300, leading to impaired HIF-1α transactivation. We examined whether local enhancement of HIF-1α activity would improve diabetic wound healing and minimize the severity of diabetic ulcers. To improve HIF-1α activity we designed a transdermal drug delivery system (TDDS) containing the FDA-approved small molecule deferoxamine (DFO), an iron chelator that increases HIF-1α transactivation in diabetes by preventing iron-catalyzed reactive oxygen stress. Applying this TDDS to a pressure-induced ulcer model in diabetic mice, we found that transdermal delivery of DFO significantly improved wound healing. Unexpectedly, prophylactic application of this transdermal delivery system also prevented diabetic ulcer formation. DFO-treated wounds demonstrated increased collagen density, improved neovascularization, and reduction of free radical formation, leading to decreased cell death. These findings suggest that transdermal delivery of DFO provides a targeted means to both prevent ulcer formation and accelerate diabetic wound healing with the potential for rapid clinical translation. PMID:25535360

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.

Evolution of Abnormally Low Pressure at Bravo Dome and its Implications for Carbon Capture and Storage (CCS)

NASA Astrophysics Data System (ADS)

Akhbari, D.; Hesse, M. A.

2015-12-01

Carbon capture and storage allows reductions of the rapidly rising CO2 from fossil fuel-based power generation, if large storage rates and capacities can be achieved. The injection of large fluid volumes at high rates leads to a build-up of pore-pressure in the storage formation that may induce seismicity and compromise the storage security. Many natural CO2 fields in midcontinent US, in contrast, are under-pressured rather than over-pressured suggesting that natural processes reduce initial over-pressures and generate significant under-pressures. The question is therefore to understand the sequence of process(es) that allow the initial over-pressure to be eliminated and the under-pressure to be maintained over geological periods of time. We therefore look into pressure evolution in Bravo Dome, one of the largest natural CO2 accumulations in North America, which stores 1.3 Gt of CO2. Bravo Dome is only 580-900 m deep and is divided into several compartments with near gas-static pressure (see Figure). The pre-production gas pressures in the two main compartments that account for 70% of the mass of CO2 stored at Bravo Dome are more than 6 MPa below hydrostatic pressure. Here we show that the under-pressure in the Bravo Dome CO2 reservoir is maintained by hydrological compartmentalization over millennial timescales and generated by a combination of processes including cooling, erosional unloading, limited leakage into overlying formations, and CO2 dissolution into brine. Herein, we introduce CO2 dissolution into brine as a new process that reduce gas pressure in a compartmentalized reservoir and our results suggest that it may contribute significantly to reduce the initial pressure build-up due to injection. Bravo Dome is the first documented case of pressure drop due to CO2 dissolution. To have an accurate prediction of pressure evolution in Bravo Dome, our models must include geomechanics and thermodynamics for the reservoir while they account for the pressure changes due to the CO2 dissolution.

Full paleostress tensor reconstruction using quartz veins of Panasqueira Mine, central Portugal; part I: Paleopressure determination

NASA Astrophysics Data System (ADS)

Jaques, Luís; Pascal, Christophe

2017-09-01

Paleostress tensor restoration methods are traditionally limited to reconstructing geometrical parameters and are unable to resolve stress magnitudes. Based on previous studies we further developed a methodology to restore full paleostress tensors. We concentrated on inversion of Mode I fractures and acquired data in Panasqueira Mine, Portugal, where optimal exposures of mineralized quartz veins can be found. To carry out full paleostress restoration we needed to determine (1) pore (paleo)pressure and (2) vein attitudes. The present contribution focuses specifically on the determination of pore pressure. To these aims we conducted an extensive fluid inclusion study to derive fluid isochores from the quartz of the studied veins. To constrain P-T conditions, we combined these isochores with crystallisation temperatures derived from geochemical analyses of coeval arsenopyrite. We also applied the sphalerite geobarometer and considered two other independent pressure indicators. Our results point to pore pressures of ∼300 MPa and formation depths of ∼10 km. Such formation depths are in good agreement with the regional geological evolution. The obtained pore pressure will be merged with vein inversion results, in order to achieve full paleostress tensor restoration, in a forthcoming companion paper.

Quantitative investigation of the gassing behavior in cylindrical Li4Ti5O12 batteries

NASA Astrophysics Data System (ADS)

Wang, Qian; Zhang, Jian; Liu, Wei; Xie, Xiaohua; Xia, Baojia

2017-03-01

The Li4Ti5O12 gassing behavior is a critical limitation for applications in lithium-ion batteries. The impact of electrode/electrolyte interface, as well as the underlying mechanisms involved during the gassing process, are still debated. Herein, a quantitative evolution of the internal pressure in 18650-type cylindrical Li4Ti5O12 batteries is investigated using a self-designed pressure testing device. The results indicate that the internal pressure significantly increases during the formation cycle and continues growing during the following cycles. After several charge and discharge cycles, the pressure finally reaches constant. Simultaneously, the formation of the solid electrolyte interphase (SEI) film is also investigated. The results suggest that the initial formed SEI film has a thickness of 24 nm, and is observed to shrink during the following cycles. Furthermore, no apparent increase in thickness accompanying the pressure rising is noticed. These comparative investigations reveal a possible mechanism of the gassing behavior. We suggest that the gassing behavior is associated with side reactions which are determined by the potential of the Li4Ti5O12 electrode, where the active sites of the electrode/electrolyte interface manage the extent of the reaction.

The composite Archaean grey gneisses: Petrological significance, and evidence for a non-unique tectonic setting for Archaean crustal growth

NASA Astrophysics Data System (ADS)

Moyen, Jean-François

2011-04-01

The geodynamic context of formation of the Archaean continental crust is a matter of debate. The crust is largely made of grey gneiss complexes, a composite rock assemblage dominated by granitoids that are generally regarded as belonging to the TTG (tonalite-trondhjemite-granodiorite) series. Using a large database of published TTG and grey gneiss compositions, it is possible to show that the granitoids forming grey gneiss complexes actually belong to at least four main geochemical groups: (i) a potassic component made of granodiorites and formed by melting of existing crustal lithologies; and (ii) three sodic groups (TTG proper) that comprise low, medium and high pressure groups. The geochemistry of the low pressure group is consistent with derivation from a plagioclase and garnet-amphibolite; the medium pressure group was formed in equilibrium with a garnet-rich, plagioclase-poor amphibolite, whereas the high pressure group derived from a rutile-bearing eclogite. As the temperature of melting of metamafic rocks is largely independent from pressure, this corresponds to melting along a range of contrasting geothermal gradients, in turn reflecting a range of tectonic sites for the formation of the Archaean continental crust.

Threshold altitude for bubble decay and stabilization in rat adipose tissue at hypobaric exposures.

PubMed

Randsoe, Thomas; Hyldegaard, Ole

2013-07-01

Bubble formation during altitude exposures, causing altitude decompression sickness (aDCS), has been referred to in theoretical models as venous gas embolisms (VGE). This has also been demonstrated by intravascular gas formation. Previous reports indicate that the formation of VGE and aDCS incidence increase abruptly for exposures exceeding 40-44 kPa ambient pressures. Further, extravascular micro air bubbles injected into adipose tissue grow transiently, then shrink and disappear while breathing oxygen (F1O2 = 1.0) at 71 kPa. At 25 kPa similar air bubbles will grow and stabilize during oxygen breathing without disappearing. We hypothesize that an ambient pressure threshold for either extravascular bubble stabilization or disappearance may be identified between 71 and 25 kPa. Whether extravascular bubbles will stabilize above a certain threshold has not been demonstrated before. In anesthetized rats, micro air bubbles (containing 79% nitrogen) of 500 nl were injected into exposed abdominal adipose tissue. Rats were decompressed in 2-35 min to either 60, 47, or 36 kPa and bubbles studied for 215 min during continued oxygen breathing (F1O2 = 1). Significantly more bubbles shrank and disappeared at 60 (14 of 17) and 47 kPa (14 of 15) as compared to bubbles exposed to 36 kPa (3 of 15) ambient pressure. The results indicate that a threshold causing extravascular bubble stabilization or decay is between 47 to 36 kPa. The results are in agreement with previous reports demonstrating an increase in the formation of VGE and symptoms of aDCS at altitudes higher than 44 kPa ambient pressure.

Cardiovascular Deconditioning and Venous Air Embolism in Simulated Microgravity in the Rat

NASA Technical Reports Server (NTRS)

Robinson, R. R.; Doursout, M.-F.; Chelly, J. E.; Powell, M. R.; Little, T. M.; Butler,B. D.

1996-01-01

Astronauts conducting extravehicular activities undergo decompression to a lower ambient pressure, potentially resulting in gas bubble formation within the tissues and venous circulation. Additionally, exposure to microgravity produces fluid shifts within the body leading to cardiovascular deconditioning. A lower incidence of decompression illness in actual spaceflight compared with that in ground-based altitude chamber flights suggests that there is a possible interaction between microgravity exposure and decompression illness. The purpose of this study was to evaluate the cardiovascular and pulmonary effects of simulated hypobaric decompression stress using a tail suspension (head-down tilt) model of microgravity to produce the fluid shifts associated with weightlessness in conscious, chronically instrumented rats. Venous bubble formation resulting from altitude decompression illness was simulated by a 3-h intravenous air infusion. Cardiovascular deconditioning was simulated by 96 h of head-down tilt. Heart rate, mean arterial blood pressure, central venous pressure, left ventricular wall thickening and cardiac output were continuously recorded. Lung studies were performed to evaluate edema formation and compliance measurement. Blood and pleural fluid were examined for changes in white cell counts and protein concentration. Our data demonstrated that in tail-suspended rats subjected to venous air infusions, there was a reduction in pulmonary edema formation and less of a decrease in cardiac output than occurred following venous air infusion alone. Mean arterial blood pressure and myocardial wall thickening fractions were unchanged with either tail-suspension or venous air infusion. Heart rate decreased in both conditions while systemic vascular resistance increased. These differences may be due in part to a change or redistribution of pulmonary blood flow or to a diminished cellular response to the microvascular insult of the venous air embolization.

Geotechnical Feasibility Analysis of Compressed Air Energy Storage (CAES) in Bedded Salt Formations: a Case Study in Huai'an City, China

NASA Astrophysics Data System (ADS)

Zhang, Guimin; Li, Yinping; Daemen, Jaak J. K.; Yang, Chunhe; Wu, Yu; Zhang, Kai; Chen, Yanlong

2015-09-01

The lower reaches of the Yangtze River is one of the most developed regions in China. It is desirable to build compressed air energy storage (CAES) power plants in this area to ensure the safety, stability, and economic operation of the power network. Geotechnical feasibility analysis was carried out for CAES in impure bedded salt formations in Huai'an City, China, located in this region. First, geological investigation revealed that the salt groups in the Zhangxing Block meet the basic geological conditions for CAES storage, even though the possible unfavorable characteristics of the salt formations include bedding and different percentages of impurities. Second, mechanical tests were carried out to determine the mechanical characteristics of the bedded salt formations. It is encouraging that the samples did not fail even when they had undergone large creep deformation. Finally, numerical simulation was performed to evaluate the stability and volume shrinkage of the CAES under the following conditions: the shape of a single cavern is that of a pear; the width of the pillar is adopted as two times the largest diameter; three regular operating patterns were adopted for two operating caverns (internal pressure 9-10.5 MPa, 10-11.5 MPa, and 11-12.5 MPa), while the other two were kept at high pressure (internal pressure 10.5, 11.5, and 12.5 MPa) as backups; an emergency operating pattern in which two operating caverns were kept at atmospheric pressure (0.1 MPa) for emergency while the backups were under operation (9-10.5 MPa), simulated for 12 months at the beginning of the 5th year. The results of the analysis for the plastic zone, displacement, and volume shrinkage support the feasibility of the construction of an underground CAES power station.

In Situ Visualization of the Dynamics in Xylem Embolism Formation and Removal in the Absence of Root Pressure: A Study on Excised Grapevine Stems.

PubMed

Knipfer, Thorsten; Cuneo, Italo F; Brodersen, Craig R; McElrone, Andrew J

2016-06-01

Gas embolisms formed during drought can disrupt long-distance water transport through plant xylem vessels, but some species have the ability to remove these blockages. Despite evidence suggesting that embolism removal is linked to the presence of vessel-associated parenchyma, the underlying mechanism remains controversial and is thought to involve positive pressure generated by roots. Here, we used in situ x-ray microtomography on excised grapevine stems to determine if embolism removal is possible without root pressure, and if the embolism formation/removal affects vessel functional status after sample excision. Our data show that embolism removal in excised stems was driven by water droplet growth and was qualitatively identical to refilling in intact plants. When stem segments were rehydrated with H2O after excision, vessel refilling occurred rapidly (<1 h). The refilling process was substantially slower when polyethylene glycol was added to the H2O source, thereby providing new support for an osmotically driven refilling mechanism. In contrast, segments not supplied with H2O showed no refilling and increased embolism formation. Dynamic changes in liquid/wall contact angles indicated that the processes of embolism removal (i.e. vessel refilling) by water influx and embolism formation by water efflux were directly linked to the activity of vessel-associated living tissue. Overall, our results emphasize that root pressure is not required as a driving force for vessel refilling, and care should be taken when performing hydraulics measurements on excised plant organs containing living vessel-associated tissue, because the vessel behavior may not be static. © 2016 American Society of Plant Biologists. All Rights Reserved.

In Situ Visualization of the Dynamics in Xylem Embolism Formation and Removal in the Absence of Root Pressure: A Study on Excised Grapevine Stems1[OPEN

PubMed Central

Knipfer, Thorsten; Cuneo, Italo F.; Brodersen, Craig R.; McElrone, Andrew J.

2016-01-01

Gas embolisms formed during drought can disrupt long-distance water transport through plant xylem vessels, but some species have the ability to remove these blockages. Despite evidence suggesting that embolism removal is linked to the presence of vessel-associated parenchyma, the underlying mechanism remains controversial and is thought to involve positive pressure generated by roots. Here, we used in situ x-ray microtomography on excised grapevine stems to determine if embolism removal is possible without root pressure, and if the embolism formation/removal affects vessel functional status after sample excision. Our data show that embolism removal in excised stems was driven by water droplet growth and was qualitatively identical to refilling in intact plants. When stem segments were rehydrated with H2O after excision, vessel refilling occurred rapidly (<1 h). The refilling process was substantially slower when polyethylene glycol was added to the H2O source, thereby providing new support for an osmotically driven refilling mechanism. In contrast, segments not supplied with H2O showed no refilling and increased embolism formation. Dynamic changes in liquid/wall contact angles indicated that the processes of embolism removal (i.e. vessel refilling) by water influx and embolism formation by water efflux were directly linked to the activity of vessel-associated living tissue. Overall, our results emphasize that root pressure is not required as a driving force for vessel refilling, and care should be taken when performing hydraulics measurements on excised plant organs containing living vessel-associated tissue, because the vessel behavior may not be static. PMID:27208267

Chlorine gas exposure disrupts nitric oxide homeostasis in the pulmonary vasculature

PubMed Central

Honavar, Jaideep; Bradley, Eddie; Bradley, Kelley; Oh, Joo Yeun; Vallejo, Matthew O.; Kelley, Eric E.; Cantu-Medellin, Nadiezhda; Doran, Stephen; Dell’italia, Louis J.; Matalon, Sadis; Patel, Rakesh P.

2014-01-01

Exposure to chlorine (Cl2) gas during industrial accidents or chemical warfare leads to significant airway and distal lung epithelial injury that continues post exposure. While lung epithelial injury is prevalent, relatively little is known about whether Cl2 gas also promotes injury to the pulmonary vasculature. To determine this, rats were subjected to a sub-lethal Cl2 gas exposure (400ppm, 30min) and then brought back to room air. Pulmonary arteries (PA) were isolated from rats at various times post-exposure and contractile (phenylephrine) and nitric oxide (NO)-dependent vasodilation (acetylcholine and mahmanonoate) responses measured ex-vivo. PA contractility did not change, however significant inhibition of NO-dependent vasodilation was observed that was maximal at 24–48 hours post exposure. Superoxide dismutase restored NO-dependent vasodilation suggesting a role for increased superoxide formation. This was supported by ~2-fold increase in superoxide formation (measured using 2-hydroethidine oxidation to 2-OH-E+) from PA isolated from Cl2 exposed rats. We next measured PA pressures in anesthetized rats. Surprisingly, PA pressures were significantly (~4mmHg) lower in rats that had been exposed to Cl2 gas 24 hours earlier suggesting that deficit in NO-signaling observed in isolated PA experiments did not manifest as increased PA pressures in vivo. Administration of the iNOS selective inhibitor 1400W, restored PA pressures to normal in Cl2 exposed, but not control rats suggesting that any deficit in NO-signaling due to increased superoxide formation in the PA, is offset by increased NO-formation from iNOS. These data indicate that disruption of endogenous NO-signaling mechanisms that maintain PA tone is an important aspect of post-Cl2 gas exposure toxicity. PMID:24769334

Detecting gas hydrate behavior in crude oil using NMR.

PubMed

Gao, Shuqiang; House, Waylon; Chapman, Walter G

2006-04-06

Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions.

FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS IN AN ATMOSPHERIC PRESSURE ETHYLENE DIFFUSION FLAME. (R825412)

EPA Science Inventory

Abstract

The microstructure of an atmospheric pressure, counterflow, sooting, flat, laminar ethylene diffusion flame has been studied experimentally by withdrawing samples from within the flame using a heated quartz microprobe coupled to an online gas chromatograph/mas...

Could some aviation deep vein thrombosis be a form of decompression sickness?

PubMed

Buzzacott, Peter; Mollerlokken, Andreas

2016-10-01

Aviation deep vein thrombosis is a challenge poorly understood in modern aviation. The aim of the present project was to determine if cabin decompression might favor formation of vascular bubbles in commercial air travelers. Thirty commercial flights were taken. Cabin pressure was noted at take-off and at every minute following, until the pressure stabilized. These time-pressure profiles were imported into the statistics program R and analyzed using the package SCUBA. Greatest pressure differentials between tissues and cabin pressures were estimated for 20, 40, 60, 80 and 120 min half-time compartments. Time to decompress ranged from 11 to 47 min. The greatest drop in cabin pressure was from 1022 to 776 mBar, equivalent to a saturated diver ascending from 2.46 msw depth. Mean pressure drop in flights >2 h duration was 193 mBar, while mean pressure drop in flights <2 h was 165 mBar. The greatest drop in pressure over 1 min was 28 mBar. Over 30 commercial flights it was found that the drop in cabin pressure was commensurate with that found to cause bubbles in man. Both the US Navy and the Royal Navy mandate far slower decompression from states of saturation, being 1.7 and 1.9 mBar/min respectively. The median overall rate of decompression found in this study was 8.5 mBar/min, five times the rate prescribed for USN saturation divers. The tissues associated with hypobaric bubble formation are likely slower than those associated with bounce diving, with 60 min a potentially useful index.

Shatter cones formed in large-scale experimental explosion craters

NASA Technical Reports Server (NTRS)

Roddy, D. J.; Davis, L. K.

1977-01-01

In 1968, a series of 0.5-ton and 100-ton TNT explosion experiments were conducted in granitic rock near Cedar City, Utah, as part of a basic research program on cratering and shock wave propagation. Of special interest was the formation of an important type of shock metamorphic feature, shatter cones. A description is presented of the first reported occurrence of shatter cones in high explosion trials. A background to shatter cone studies is presented and attention is given to the test program, geology and physical properties of the test medium, the observed cratering, and the formational pressures for shatter cones. The high explosion trials conducted demonstrate beyond any doubt, that shatter cones can be formed by shock wave processes during cratering and that average formational pressures in these crystalline rocks are in the 20-60 kb range.

Jet formation in cerium metal to examine material strength

DOE PAGES

Jensen, B. J.; Cherne, F. J.; Prime, M. B.; ...

2015-11-18

Examining the evolution of material properties at extreme conditions advances our understanding of numerous high-pressure phenomena from natural events like meteorite impacts to general solid mechanics and fluid flow behavior. Some recent advances in synchrotron diagnostics coupled with dynamic compression platforms have introduced new possibilities for examining in-situ, spatially resolved material response with nanosecond time resolution. In this work, we examined jet formation from a Richtmyer-Meshkov instability in cerium initially shocked into a transient, high-pressure phase, and then released to a low-pressure, higher-temperature state. Cerium's rich phase diagram allows us to study the yield stress following a shock induced solid-solidmore » phase transition. X-ray imaging was used to obtain images of jet formation and evolution with 2–3 μm spatial resolution. And from these images, an analytic method was used to estimate the post-shock yield stress, and these results were compared to continuum calculations that incorporated an experimentally validated equation-of-state (EOS) for cerium coupled with a deviatoric strength model. Reasonable agreement was observed between the calculations and the data illustrating the sensitivity of jet formation on the yield stress values. Finally, the data and analysis shown here provide insight into material strength during dynamic loading which is expected to aid in the development of strength aware multi-phase EOS required to predict the response of matter at extreme conditions.« less

Theoretical assessment of bonaccordite formation in pressurized water reactors

DOE PAGES

Rak, Zsolt; O'Brien, Chris; Shin, Dongwon; ...

2016-03-04

The free energy of formation of bonaccordite (Ni 2FeBO 5) as a function of temperature has been calculated using a technique that combines first principles calculations with experimental free energies of formation of aqueous species. The results suggest that bonaccordite formation from aqueous metal ions (Ni 2+ andFe 3+) and boric acid is thermodynamically favorable at elevated temperature and pH that have been predicted to exist at the CRUD-clad interface in deposits thicker than 60 μm.

Theoretical assessment of bonaccordite formation in pressurized water reactors

NASA Astrophysics Data System (ADS)

Rak, Zs; O'Brien, C. J.; Shin, D.; Andersson, A. D.; Stanek, C. R.; Brenner, D. W.

2016-06-01

The free energy of formation of bonaccordite (Ni2FeBO5) as a function of temperature has been calculated using a technique that combines first principles calculations with experimental free energies of formation of aqueous species. The results suggest that bonaccordite formation from aqueous metal ions (Ni2+ andFe3+) and boric acid is thermodynamically favorable at elevated temperature and pH that have been predicted to exist at the CRUD-clad interface in deposits thicker than 60 μm.

Systems and methods for multi-fluid geothermal energy systems

DOEpatents

Buscheck, Thomas A.

2017-09-19

A method for extracting geothermal energy from a geothermal reservoir formation. A production well is used to extract brine from the reservoir formation. At least one of nitrogen (N.sub.2) and carbon dioxide (CO.sub.2) may be used to form a supplemental working fluid which may be injected into a supplemental working fluid injection well. The supplemental working fluid may be used to augment a pressure of the reservoir formation, to thus drive a flow of the brine out from the reservoir formation.

The Rapid Formation of Localized Compaction Bands Under Hydrostatic Load Leading to Pore-pressure Transients in Compacting Rocks

NASA Astrophysics Data System (ADS)

Faulkner, D.; Leclere, H.; Bedford, J. D.; Behnsen, J.; Wheeler, J.

2017-12-01

Compaction of porous rocks can occur uniformly or within localized deformation bands. The formation of compaction bands and their effects on deformation behaviour are poorly understood. Porosity may be primary and compaction can occur with burial, or it can be produced by metamorphic reactions with a solid volume reduction, that can then undergo collapse. We report results from hydrostatic compaction experiments on porous bassanite (CaSO4.0.5H2O) aggregates. Gypsum (CaSO4.2H2O) is first dehydrated under low effective pressure, 4 MPa, to produce a bassanite aggregate with a porosity of 27%. Compaction is induced by increasing confining pressure at rates from 0.001 MPa/s to 0.02 MPa/s while the sample is maintained at a temperature of 115°C. At slow compaction rates, porosity collapse proceeds smoothly. At higher compaction rates, sudden increases in the pore-fluid pressure occur with a magnitude of 5 MPa. Microstructural investigations using X-ray microtomography and SEM observations show that randomly oriented localized compaction features occur in all samples, where the bulk porosity of 18% outside the band is reduced to 5% inside the band. Previous work on deformation bands has suggested that localized compactive features only form under an elevated differential stress and not under a hydrostatic stress state. The magnitude of the pore-pressure pulses can be explained by the formation of compaction bands. The results indicate that the compaction bands can form by rapid (unstable) propagation across the sample above a critical strain rate, or quasi-statically at low compaction rates without pore-fluid pressure bursts. The absence of pore-fluid pressure bursts at slow compaction rates can be explained by viscous deformation of the bassanite aggregate around the tip of a propagating compaction band, relaxing stress, and promoting stable propagation. Conversely, at higher compaction rates, viscous deformation cannot relax the stress sufficiently and unstable, brittle propagation occurs. In nature, this type of compaction behaviour might result in a mechanism to produce pulses of pore pressure within porous rocks which might have a significant effect on the deformation behaviour at depth.

18 CFR 270.305 - Determination of tight formation areas.

Code of Federal Regulations, 2010 CFR

2010-04-01

... pressure, of wells completed for production in such portion of such formation, without stimulation, is not...). Such expected stabilized, pre-stimulation production rate is to be determined through an arithmetic mean averaging of the known stabilized, pre-stimulation production rates obtained from the wells that...

Development of solar wind shock models with tensor plasma pressure for data analysis

NASA Technical Reports Server (NTRS)

Abraham-Shrauner, B.

1975-01-01

The development of solar wind shock models with tensor plasma pressure and the comparison of some of the shock models with the satellite data from Pioneer 6 through Pioneer 9 are reported. Theoretically, difficulties were found in non-turbulent fluid shock models for tensor pressure plasmas. For microscopic shock theories nonlinear growth caused by plasma instabilities was frequently not clearly demonstrated to lead to the formation of a shock. As a result no clear choice for a shock model for the bow shock or interplanetary tensor pressure shocks emerged.

Microbarograph - ESRL Hi-Res Microbarograph, Goldendale - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Condon - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Troutdale - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Troutdale - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Condon - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Wasco Airport - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Walla Walla - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Goldendale - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Walla Walla - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Wasco Airport - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Boardman - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, John Day - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Hood River - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Umatilla - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Boardman - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Bonneville - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Bonneville - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Umatilla - Raw Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, John Day - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Microbarograph - ESRL Hi-Res Microbarograph, Hood River - Reviewed Data

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

McCaffrey, Katherine

High-precision barometers (Paroscientific 6000-16B-IS) are combined with Nishiyama-Bedard Quad Disk pressure probes, measuring pressure (mb) at the surface, nominally 2 m above ground level. Data are sampled at 20 Hz for potential studies of turbulence. The sensors' high accuracy makes them useful for determining horizontal pressure gradients and their relation to wind ramp events, as well as the temporal variability of pressure associated with mountain wakes and waves. **Note different ASCII file formats for Goldendale (z04) and Walla Walla (z09) sites.**

Phase diagram of the Pr-Mn-O system in composition-temperature-oxygen pressure coordinates

NASA Astrophysics Data System (ADS)

Vedmid', L. B.; Yankin, A. M.; Fedorova, O. M.; Kozin, V. M.

2016-05-01

The phase relations in the Pr-Mn-O system were studied by the static method at lowered oxygen pressure in combination with thermal analysis and high-temperature X-ray diffraction. The equilibrium oxygen pressure in dissociation of PrMn2O5 and PrMnO3 was measured, and the thermodynamic characteristics of formation of these compounds from elements were calculated. The P- T- x phase diagram of the Pr-Mn-O system was constructed in the "composition-oxygen pressure-temperature" coordinates.

Laser plasma at low air pressure

NASA Astrophysics Data System (ADS)

Vas'kovskii, Iu. M.; Moiseev, V. N.; Rovinskii, R. E.; Tsenina, I. S.

1993-01-01

The ambient-pressure dependences of the dynamic and optical characteristics of a laser plasma generated by CO2-laser irradiation of an obstacle are investigated experimentally. The change of the sample's surface roughness after irradiation is investigated as a function of air pressure. It is concluded that the transition from the air plasma to the erosion plasma takes place at an air pressure of about 1 mm Hg. The results confirm the existing theory of plasma formation near the surface of an obstacle under the CO2-laser pulse effect in air.

Characterizing Droplet Formation from Non-Linear Slosh in a Propellant Tank

NASA Technical Reports Server (NTRS)

Brodnick, Jacob; Yang, Hong; West, Jeffrey

2015-01-01

The Fluid Dynamics Branch (ER42) at the Marshall Space Flight Center (MSFC) was tasked with characterizing the formation and evolution of liquid droplets resulting from nonlinear propellant slosh in a storage tank. Lateral excitation of propellant tanks can produce high amplitude nonlinear slosh waves through large amplitude excitations and or excitation frequencies near a resonance frequency of the tank. The high amplitude slosh waves become breaking waves upon attaining a certain amplitude or encountering a contracting geometry such as the upper dome section of a spherical tank. Inherent perturbations in the thinning regions of breaking waves result in alternating regions of high and low pressure within the fluid. Droplets form once the force from the local pressure differential becomes larger than the force maintaining the fluid interface shape due to surface tension. Droplets released from breaking waves in a pressurized tank may lead to ullage collapse given the appropriate conditions due to the increased liquid surface area and thus heat transfer between the fluids. The goal of this project is to create an engineering model that describes droplet formation as a function of propellant slosh for use in the evaluation of ullage collapse during a sloshing event. The Volume of Fluid (VOF) model in the production level Computational Fluid Dynamics (CFD) code Loci-Stream was used to predict droplet formation from breaking waves with realistic surface tension characteristics. Various excitation frequencies and amplitudes were investigated at multiple fill levels for a single storage tank to create the engineering model of droplet formation from lateral propellant slosh.

Real-Time Processing of Pressure-Sensitive Paint Images

DTIC Science & Technology

2006-12-01

intermediate or final data to the hard disk in 3D grid format. In addition to the pressure or pressure coefficient at every grid point, the saved file may...occurs. Nevertheless, to achieve an accurate mapping between 2D image coordinates and 3D spatial coordinates, additional parameters must be introduced. A...improved mapping between the 2D and 3D coordinates. In a more sophisticated approach, additional terms corresponding to specific deformation modes

Gas-blowout control by water injection through relief wells: a theoretical analysis. [Injection of water into the formation through relief wells

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

Lehner, F.; Williamson, A.S.

1974-08-01

Koninklijke/Shell Exploratie en Produktie Laboratorium in The Netherlands suggests bringing a gas blowout under control by injecting water into the formation through relief wells. By avoiding direct contact between relief well and blowout well, this technique reduces the inflow of gas by creating sufficient back pressure in the formation itself. The mechanics of the technique are considered.

From Assessment to Instruction: The Impact of Online Formative Assessment in Reading on Teachers' Planning and Instruction in the Middle School English Language Arts Classroom

ERIC Educational Resources Information Center

Hayes, Ann Milligan

2015-01-01

Over the last two decades, there has been renewed interest in formative assessment, in large part due to the increasing pressures and prevalence of "high stakes" summative assessments. As states try to meet the requirements of the No Child Left Behind law, teachers and administrators are realizing that formative assessment offers an…

Chromospheric dust formation, stellar masers and mass loss

NASA Technical Reports Server (NTRS)

Stencel, R. E.

1986-01-01

A multistep scenario which describes a plausible mass loss mechanism associated with red giant and related stars is outlined. The process involves triggering a condensation instability in an extended chromosphere, leading to the formation of cool, dense clouds which are conducive to the formation of molecules and dust grains. Once formed, the dust can be driven away from the star by radiation pressure. Consistency with various observed phenomena is discussed.

UVIT view of ram-pressure stripping in action: Star formation in the stripped gas of the GASP jellyfish galaxy JO201 in Abell 85

NASA Astrophysics Data System (ADS)

George, K.; Poggianti, B. M.; Gullieuszik, M.; Fasano, G.; Bellhouse, C.; Postma, J.; Moretti, A.; Jaffé, Y.; Vulcani, B.; Bettoni, D.; Fritz, J.; Côté, P.; Ghosh, S. K.; Hutchings, J. B.; Mohan, R.; Sreekumar, P.; Stalin, C. S.; Subramaniam, A.; Tandon, S. N.

2018-06-01

Jellyfish are cluster galaxies that experience strong ram-pressure effects that strip their gas. Their Hα images reveal ionized gas tails up to 100 kpc, which could be hosting ongoing star formation. Here we report the ultraviolet (UV) imaging observation of the jellyfish galaxy JO201 obtained at a spatial resolution ˜ 1.3 kpc. The intense burst of star formation happening in the tentacles is the focus of the present study. JO201 is the "UV-brightest cluster galaxy" in Abell 85 (z ˜ 0.056) with knots and streams of star formation in the ultraviolet. We identify star forming knots both in the stripped gas and in the galaxy disk and compare the UV features with the ones traced by Hα emission. Overall, the two emissions remarkably correlate, both in the main body and along the tentacles. Similarly, also the star formation rates of individual knots derived from the extinction-corrected FUV emission agree with those derived from the Hα emission and range from ˜ 0.01 -to- 2.07 M⊙ yr-1. The integrated star formation rate from FUV flux is ˜ 15 M⊙ yr-1. The unprecedented deep UV imaging study of the jellyfish galaxy JO201 shows clear signs of extraplanar star-formation activity due to a recent/ongoing gas stripping event.

Fresh Water Generation from Aquifer-Pressured Carbon Storage: Interim Progress Report

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

Aines, R D; Wolery, T J; Hao, Y

2009-07-22

This project is establishing the potential for using brine pressurized by Carbon Capture and Storage (CCS) operations in saline formations as the feedstock for desalination and water treatment technologies including nanofiltration (NF) and reverse osmosis (RO). The aquifer pressure resulting from the energy required to inject the carbon dioxide provides all or part of the inlet pressure for the desalination system. Residual brine would be reinjected into the formation at net volume reduction. This process provides additional storage space (capacity) in the aquifer, reduces operational risks by relieving overpressure in the aquifer, and provides a source of low-cost fresh watermore » to offset costs or operational water needs. Computer modeling and laboratory-scale experimentation are being used to examine mineral scaling and osmotic pressure limitations for brines typical of CCS sites. Computer modeling is being used to evaluate processes in the aquifer, including the evolution of the pressure field. This progress report deals mainly with our geochemical modeling of high-salinity brines and covers the first six months of project execution (September, 2008 to March, 2009). Costs and implementation results will be presented in the annual report. The brines typical of sequestration sites can be several times more concentrated than seawater, requiring specialized modeling codes typical of those developed for nuclear waste disposal calculations. The osmotic pressure developed as the brines are concentrated is of particular concern, as are precipitates that can cause fouling of reverse osmosis membranes and other types of membranes (e.g., NF). We have now completed the development associated with tasks (1) and (2) of the work plan. We now have a contract with Perlorica, Inc., to provide support to the cost analysis and nanofiltration evaluation. We have also conducted several preliminary analyses of the pressure effect in the reservoir in order to confirm that reservoir pressure can indeed be used to drive the reverse osmosis process. Our initial conclusions from the work to date are encouraging: (1) The concept of aquifer-pressured RO to provide fresh water associated with carbon dioxide storage appears feasible. (2) Concentrated brines such as those found in Wyoming are amenable to RO treatment. We have looked at sodium chloride brines from the Nugget Formation in Sublette County. 20-25% removal with conventional methods is realistic; higher removal appears achievable with NF. The less concentrated sulfate-rich brines from the Tensleep Formation in Sublette County would support >80% removal with conventional RO. (3) Brines from other proposed sequestration sites can now be analyzed readily. An osmotic pressure curve appropriate to these brines can be used to evaluate cost and equipment specifications. (4) We have examined a range of subsurface brine compositions that is potentially pertinent to carbon sequestration and noted the principal compositional trends pertinent to evaluating the feasibility of freshwater extraction. We have proposed a general categorization for the feasibility of the process based on total dissolved solids (TDS). (5) Withdrawing pressurized brine can have a very beneficial effect on reservoir pressure and total available storage capacity. Brine must be extracted from a deeper location in the aquifer than the point of CO{sub 2} injection to prevent CO{sub 2} from migrating to the brine extraction well.« less

POLYCYCLIC AROMATIC HYDROCARBON FORMATION IN OPPOSED FLOW DIFFUSION FLAMES OF ETHANE. (R825412)

EPA Science Inventory

Abstract

The effect of fuel-side carbon density on the levels of polycyclic aromatic hydrocarbon (PAH) formation in atmospheric pressure, opposed flow, ethane diffusion flames has been studied using heated micro-probe sampling and gas chromatography/mass spectrometry (...

Commentary: Evaluating the Validity of Formative and Interim Assessment

ERIC Educational Resources Information Center

Shepard, Lorrie A.

2009-01-01

In many school districts, the pressure to raise test scores has created overnight celebrity status for formative assessment. Its powers to raise student achievement have been touted, however, without attending to the research on which these claims were based. Sociocultural learning theory provides theoretical grounding for understanding how…

Tulip flames: changes in shape of premixed flames propagating in closed tubes

NASA Astrophysics Data System (ADS)

Dunn-Rankin, D.; Sawyer, R. F.

The experimental results that are the subject of this communication provide high-speed schlieren images of the closed-tube flame shape that has come to be known as the tulip flame. The schlieren images, along with in-chamber pressure records, help demonstrate the effects of chamber length, equivalence ratio, and igniter geometry on formation of the tulip flame. The pressure/time records show distinct features which correlate with flame shape changes during the transition to tulip. The measurements indicate that the basic tulip flame formation is a robust phenomenon that depends on little except the overall geometry of the combustion vessel.

Pressure broadening of the ((dt. mu. )dee)* formation resonances

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

Cohen, J.S.; Leon, M.; Padial, N.T.

1988-12-27

The treatment of ((dt..mu..)dee)* formation at high densities as a pressure broadening process is discussed. Cross sections for collisions of the complex (dt..mu..)dee, and of the D/sub 2/ molecule from which it is formed, with the bath molecules have been accurately calculated. These cross sections are used to calculate the collisional width in three variations of the impact approximation that have been proposed for this problem. In general, the quasistatic approximation is shown to satisfy the usual conditions of muon-catalyzed fusion better than does the impact approximation. A preliminary rough treatment is presented to illustrate the quasistatic approximation.

Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

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

Tang, Jie, E-mail: tangjie1979@opt.ac.cn; Jiang, Weiman; Wang, Yishan

2015-08-24

A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

Electrostrictive Mechanism of Nanostructure Formation at Solid Surfaces Irradiated by Femtosecond Laser Pulses.

PubMed

Pavlyniuk, Oleg R; Datsyuk, Vitaly V

2016-12-01

The significance of the mechanical pressure of light in creation of laser-induced periodic surface structures (LIPSSs) is investigated. Distributions of the electrically induced normal pressure and tangential stress at the illuminated solid surface, as well as the field of volume electrostrictive forces, are calculated taking into account surface plasmon polariton (SPP) excitation. Based on these calculations, we predict surface destruction and structure formation due to inelastic deformations during single femtosecond pulses. The calculated fields of the electromagnetic forces are found to agree well with the experimental ripple structures. We thus conclude that the electrostrictive forces can explain the origin of the periodic ripple structures.

The role of non-ionizing radiation pressure in star formation: the stability of cores and filaments

NASA Astrophysics Data System (ADS)

Seo, Young Min; Youdin, Andrew N.

2016-09-01

Stars form when filaments and dense cores in molecular clouds fragment and collapse due to self-gravity. In the most basic analyses of gravitational stability, the competition between self-gravity and thermal pressure sets the critical (I.e. maximum stable) mass of spheres and the critical line density of cylinders. Previous work has considered additional support from magnetic fields and turbulence. Here, we consider the effects of non-ionizing radiation, specifically the inward radiation pressure force that acts on dense structures embedded in an isotropic radiation field. Using hydrostatic, isothermal models, we find that irradiation lowers the critical mass and line density for gravitational collapse, and can thus act as a trigger for star formation. For structures with moderate central densities, ˜103 cm-3, the interstellar radiation field in the Solar vicinity has an order unity effect on stability thresholds. For more evolved objects with higher central densities, a significant lowering of stability thresholds requires stronger irradiation, as can be found closer to the Galactic centre or near stellar associations. Even when strong sources of ionizing radiation are absent or extincted, our study shows that interstellar irradiation can significantly influence the star formation process.

Onset of magnetic reconnection in a weakly collisional, high- β plasma

NASA Astrophysics Data System (ADS)

Alt, Andrew; Kunz, Matthew

2017-10-01

In a magnetized, weakly collisional plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase of the magnetic-field strength in such a plasma thus leads to an increase in the thermal pressure perpendicular to the field lines. Above a β-dependent threshold, this pressure anisotropy drives the mirror instability, which produces strong distortions in the field lines and traps particles on ion-Larmor scales. The impact of this instability on magnetic reconnection is investigated using simple analytical and numerical models for the formation of a current sheet and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a current sheet in a weakly collisional plasma, coupled with the low threshold for the mirror instability in a high- β plasma, imply that the topology of reconnecting magnetic fields can radically differ from the standard Harris-sheet profile often used in kinetic simulations of collisionless reconnection. Depending on the rate of current-sheet formation, this mirror-induced disruption may occur before standard tearing modes are able to develop. This work was supported by U.S. DOE contract DE-AC02-09CH11466.

High Pressure and Temperature Core Formation as an Alternative to the "Late Veneer" Hypothesis

NASA Technical Reports Server (NTRS)

Righter, Kevin; Pando, K.; Humayun, M.; Danielson, L.

2011-01-01

The highly siderophile elements (HSE; Re, Au and the Platinum Group Elements - Pd Pt, Rh, Ru, Ir, Os) are commonly utilized to constrain accretion processes in terrestrial differentiated bodies due to their affinity for FeNi metal [1]. These eight elements exhibit highly siderophile behavior, but nonetheless have highly diverse metal-silicate partition coefficients [2]. Therefore the near chondritic relative concentrations of HSEs in the terrestrial and lunar mantles, as well as some other bodies, are attributed to late accretion rather than core formation [1]. Evaluation of competing theories, such as high pressure metal-silicate partitioning or magma ocean hypotheses has been hindered by a lack of relevant partitioning data for this group of eight elements. In particular, systematic studies isolating the effect of one variable (e.g. temperature or melt compositions) are lacking. Here we undertake new experiments on all eight elements, using Fe metal and FeO-bearing silicate melts at fixed pressure, but variable temperatures. These experiments, as well as some additional planned experiments should allow partition coefficients to be more accurately calculated or estimated at the PT conditions and compositions at which core formation is thought to have occurred.

Low-pressure clathrate-hydrate formation in amorphous astrophysical ice analogs

NASA Technical Reports Server (NTRS)

Blake, D. F.; Allamandola, L. J.; Sandford, S.; Hudgins, D.; Freund, F.

1991-01-01

In modeling cometary ice, the properties of clathrate hydrates were used to explain anomalous gas release at large radial distances from the Sun, and the retention of particular gas inventories at elevated temperatures. Clathrates may also have been important early in solar system history. However, there has never been a reasonable mechanism proposed for clathrate formation under the low pressures typical of these environments. For the first time, it was shown that clathrate hydrates can be formed by warming and annealing amorphous mixed molecular ices at low pressures. The complex microstructures which occur as a result of clathrate formation from the solid state may provide an explanation for a variety of unexplained phenomena. The vacuum and imaging systems of an Hitachi H-500H Analytical Electron Microscope was modified to study mixed molecular ices at temperatures between 12 and 373 K. The resulting ices are characterized by low-electron dose Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). The implications of these results for the mechanical and gas release properties of comets are discussed. Laboratory IR data from similar ices are presented which suggest the possibility of remotely observing and identifying clathrates in astrophysical objects.

Single-crystal diffraction at the Extreme Conditions beamline P02.2: procedure for collecting and analyzing high-pressure single-crystal data.

PubMed

Rothkirch, André; Gatta, G Diego; Meyer, Mathias; Merkel, Sébastien; Merlini, Marco; Liermann, Hanns Peter

2013-09-01

Fast detectors employed at third-generation synchrotrons have reduced collection times significantly and require the optimization of commercial as well as customized software packages for data reduction and analysis. In this paper a procedure to collect, process and analyze single-crystal data sets collected at high pressure at the Extreme Conditions beamline (P02.2) at PETRA III, DESY, is presented. A new data image format called `Esperanto' is introduced that is supported by the commercial software package CrysAlis(Pro) (Agilent Technologies UK Ltd). The new format acts as a vehicle to transform the most common area-detector data formats via a translator software. Such a conversion tool has been developed and converts tiff data collected on a Perkin Elmer detector, as well as data collected on a MAR345/555, to be imported into the CrysAlis(Pro) software. In order to demonstrate the validity of the new approach, a complete structure refinement of boron-mullite (Al5BO9) collected at a pressure of 19.4 (2) GPa is presented. Details pertaining to the data collections and refinements of B-mullite are presented.

In situ recovery from residually heated sections in a hydrocarbon containing formation

DOEpatents

Vinegar, Harold J.; Karanikas, John Michael; Ryan, Robert Charles

2010-12-14

Methods of treating a tar sands formation is described herein. The methods may include providing heat to a first section of a hydrocarbon layer in the formation from a plurality of heaters located in the first section of the formation. Heat is transferred from the heaters so that at least a first section of the formation reaches a selected temperature. At least a portion of residual heat from the first section transfers from the first section to a second section of the formation. At least a portion of hydrocarbons in the second section are mobilized by providing a solvation fluid and/or a pressurizing fluid to the second section of the formation.

Phase formation polycrystalline vanadium oxide via thermal annealing process under controlled nitrogen pressure

NASA Astrophysics Data System (ADS)

Jessadaluk, S.; Khemasiri, N.; Rahong, S.; Rangkasikorn, A.; Kayunkid, N.; Wirunchit, S.; Horprathum, M.; Chananonnawathron, C.; Klamchuen, A.; Nukeaw, J.

2017-09-01

This article provides an approach to improve and control crystal phases of the sputtering vanadium oxide (VxOy) thin films by post-thermal annealing process. Usually, as-deposited VxOy thin films at room temperature are amorphous phase: post-thermal annealing processes (400 °C, 2 hrs) under the various nitrogen (N2) pressures are applied to improve and control the crystal phase of VxOy thin films. The crystallinity of VxOy thin films changes from amorphous to α-V2O5 phase or V9O17 polycrystalline, which depend on the pressure of N2 carrier during annealing process. Moreover, the electrical resistivity of the VxOy thin films decrease from 105 Ω cm (amorphous) to 6×10-1 Ω cm (V9O17). Base on the results, our study show a simply method to improve and control phase formation of VxOy thin films.

Flux-trapping during the formation of field-reversed configurations

NASA Astrophysics Data System (ADS)

Armstrong, W. T.; Harding, D. G.; Crawford, E. A.; Hoffman, A. L.

1982-11-01

Flux-trapping during the early formation phases of a field-reversed configuration has been studied experimentally on the field-reversed theta-pinch TRX-1. An annular z-pinch preionizer was employed to permit ionization at high values of reverse-bias flux. Contrary to previous analysis, the rate of flux loss was not governed exclusively by inertially limited plasma convection to the tube walls. At high reverse flux levels, a pressure bearing sheath was observed to form at the tube walls and the flux loss was restricted by resistive diffusion across this sheath. The characteristic time for flux loss was 0.08rt (cm) μsec, independent of the bias field and independent of the fill pressure for fill pressures above 15 mTorr D2. Octopole barrier fields were found to be effective in limiting the inertially governed flux loss at very early times before the wall sheath formed.

Quantitative Experimental Study of Defects Induced by Process Parameters in the High-Pressure Die Cast Process

NASA Astrophysics Data System (ADS)

Sharifi, P.; Jamali, J.; Sadayappan, K.; Wood, J. T.

2018-05-01

A quantitative experimental study of the effects of process parameters on the formation of defects during solidification of high-pressure die cast magnesium alloy components is presented. The parameters studied are slow-stage velocity, fast-stage velocity, intensification pressure, and die temperature. The amount of various defects are quantitatively characterized. Multiple runs of the commercial casting simulation package, ProCAST™, are used to model the mold-filling and solidification events. Several locations in the component including knit lines, last-to-fill region, and last-to-solidify region are identified as the critical regions that have a high concentration of defects. The area fractions of total porosity, shrinkage porosity, gas porosity, and externally solidified grains are separately measured. This study shows that the process parameters, fluid flow and local solidification conditions, play major roles in the formation of defects during HPDC process.

Chromia refractory brick with carbon treatment

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

Bennett, James P.; Kwong, Kyei-Sing

The disclosure provides a refractory brick system comprising a chromia refractory brick for operation in the slagging environment of an air-cooled gasifier. The chromia refractory brick comprises a ceramically-bonded porous chromia refractory having a porosity greater than 9% and having carbon deposits residing within the pores. The brick may be further comprised of Al.sub.2O.sub.3. The air-cooled gasifier generates a liquefied slag in contact with the refractory brick and generally operates at temperatures between 1250.degree. C. and 1575.degree. C. and pressures between 300 psi to 1000 psi, with oxygen partial pressures generally between 10.sup.-4 and 10.sup.-10 atm. The refractory brick performsmore » without substantial chromium carbide or chromium metal formation in the low oxygen partial pressure environment. The inclusion of carbon without chromium carbide formation provides for significant mitigation of slag penetration and significantly reduced refractory wear.« less

Wind ripples in low density atmospheres

NASA Technical Reports Server (NTRS)

Miller, J. S.; Marshall, J. R.; Greeley, R.

1987-01-01

The effect of varying fluid density (rho) on particle transport was examined by conducting tests at atmospheric pressures between 1 and 0.004 bar in the Martian Surface Wind Tunnel (MARSWIT). This study specifically concerns the effect of varying rho on the character of wind ripples, and elicits information concerning generalized ripple models as well as specific geological circumstances for ripple formation such as those prevailing on Mars. Tests were conducted primarily with 95 micron quartz sand, and for each atmospheric pressure chosen, tests were conducted at two freestream wind speeds: 1.1 U*(t) and 1.5 U*(t), where U*(t) is saltation threshold. Preliminary analysis of the data suggests: (1) ballistic ripple wavelength is not at variance with model predictions; (2) an atmospheric pressure of approximately 0.2 bar could represent a discontinuity in ripple behavior; and (4) ripple formation on Mars may not be readily predicted by extrapolation of terrestrial observations.

Influence of a Polymer Coating and the Compacting Pressure on the Magnetic Properties of Cobalt-Based Amorphous Alloys

NASA Astrophysics Data System (ADS)

Skulkina, N. A.; Ivanov, O. A.; Mazeeva, A. K.; Kuznetsov, P. A.; Stepanova, E. A.; Blinova, O. V.; Mikhalitsyna, E. A.; Denisov, N. D.; Chekis, V. I.

2017-12-01

The influence of a polymer coating applied in the manufacture of magnetic shields on magnetic properties has been studied based on the example of ribbons of a cobalt-based soft magnetic alloy (Co-Fe-Ni-Cr-Mn-Si-B) with the saturation magnetostriction close to zero. The influence of polymer coating has been separated from the effect of the compacting pressure applied upon its formation. The polymer coating was formed on the ribbon in the states with different signs of the saturation magnetostriction. It has been shown that the compacting pressure and the polymer coating have opposite effects on the properties of the ribbon and that these impacts partly level off upon the formation of the coating. The degree of the influence of the polymer coating on the magnetic properties depends on the state of the ribbon and on the sign of the saturation magnetostriction in this state.

A large planetary body inferred from diamond inclusions in a ureilite meteorite.

PubMed

Nabiei, Farhang; Badro, James; Dennenwaldt, Teresa; Oveisi, Emad; Cantoni, Marco; Hébert, Cécile; El Goresy, Ahmed; Barrat, Jean-Alix; Gillet, Philippe

2018-04-17

Planetary formation models show that terrestrial planets are formed by the accretion of tens of Moon- to Mars-sized planetary embryos through energetic giant impacts. However, relics of these large proto-planets are yet to be found. Ureilites are one of the main families of achondritic meteorites and their parent body is believed to have been catastrophically disrupted by an impact during the first 10 million years of the solar system. Here we studied a section of the Almahata Sitta ureilite using transmission electron microscopy, where large diamonds were formed at high pressure inside the parent body. We discovered chromite, phosphate, and (Fe,Ni)-sulfide inclusions embedded in diamond. The composition and morphology of the inclusions can only be explained if the formation pressure was higher than 20 GPa. Such pressures suggest that the ureilite parent body was a Mercury- to Mars-sized planetary embryo.

The influence of hold time on the onset of plastic deformation in silicon

DOE PAGES

Wong, Sherman; Haberl, Bianca; Bradby, Jodie E.; ...

2015-12-24

Here, the formation of silicon (Si) in its -Sn form is known to be nucleation limited, with an undetermined period of time between when critical pressure for the trans- formation is reached and when the transformation actually occurs. In this letter, we use nanoindentation to apply critical pressure to diamond cubic Si and hold the sample under pressure to promote deformation via phase transformation and crystalline defects. We report that the number of indents in which phase transformation is observed increases with increasing hold time. Interestingly, the number of indents in which crystalline defects are observed also increase with increasingmore » hold time, suggesting crystalline defects are also nucleation limited. Raman spectroscopy and cross-sectional transmission electron microscopy is used to show that these two deformation mechanisms are mutually exclusive under the indentation conditions used within this letter.« less

Magma ocean formation due to giant impacts

NASA Technical Reports Server (NTRS)

Tonks, W. B.; Melosh, H. J.

1993-01-01

The thermal effects of giant impacts are studied by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths. Additionally, the effects of the planet's initial temperature on the generated melt volume are examined. The shock pressure required to completely melt the material is determined using the Hugoniot curve plotted in pressure-entropy space. Once the melting pressure is known, an impact melting model is used to estimate the radial distance melting occurred from the impact site. The melt region's geometry then determines the associated melt volume. The model is also used to estimate the partial melt volume. Magma ocean depths resulting from both excavated and retained melt are calculated, and the melt fraction not excavated during the formation of the crater is estimated. The fraction of a planet melted by the initial shock wave is also estimated using the model.

Yield-stress fluids foams: flow patterns and controlled production in T-junction and flow-focusing devices.

PubMed

Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E; Lorenceau, Elise

2016-11-23

We study the formation of yield-stress fluid foams in millifluidic flow-focusing and T-junction devices. First, we provide a phase diagram for the unsteady operating regimes of bubble production when the gas pressure and the yield-stress fluid flow rate are imposed. Three regimes are identified: a co-flow of gas and yield-stress fluid, a transient production of bubble and a flow of yield-stress fluid only. Taking wall slip into account, we provide a model for the pressure at the onset of bubble formation. Then, we detail and compare two simple methods to ensure steady bubble production: regulation of the gas pressure or flow-rate. These techniques, which are easy to implement, thus open pathways for controlled production of dry yield-stress fluid foams as shown at the end of this article.

Fracking in Tight Shales: What Is It, What Does It Accomplish, and What Are Its Consequences?

NASA Astrophysics Data System (ADS)

Norris, J. Quinn; Turcotte, Donald L.; Moores, Eldridge M.; Brodsky, Emily E.; Rundle, John B.

2016-06-01

Fracking is a popular term referring to hydraulic fracturing when it is used to extract hydrocarbons. We distinguish between low-volume traditional fracking and the high-volume modern fracking used to recover large volumes of hydrocarbons from shales. Shales are fine-grained rocks with low granular permeabilities. During the formation of oil and gas, large fluid pressures are generated. These pressures result in natural fracking, and the resulting fracture permeability allows oil and gas to escape, reducing the fluid pressures. These fractures may subsequently be sealed by mineral deposition, resulting in tight shale formations. The objective of modern fracking is to reopen these fractures and/or create new fractures on a wide range of scales. Modern fracking has had a major impact on the availability of oil and gas globally; however, there are serious environmental objections to modern fracking, which should be weighed carefully against its benefits.

Controlled Expansion of Supercritical Solution: A Robust Method to Produce Pure Drug Nanoparticles With Narrow Size-Distribution.

PubMed

Pessi, Jenni; Lassila, Ilkka; Meriläinen, Antti; Räikkönen, Heikki; Hæggström, Edward; Yliruusi, Jouko

2016-08-01

We introduce a robust, stable, and reproducible method to produce nanoparticles based on expansion of supercritical solutions using carbon dioxide as a solvent. The method, controlled expansion of supercritical solution (CESS), uses controlled mass transfer, flow, pressure reduction, and particle collection in dry ice. CESS offers control over the crystallization process as the pressure in the system is reduced according to a specific profile. Particle formation takes place before the exit nozzle, and condensation is the main mechanism for postnucleation particle growth. A 2-step gradient pressure reduction is used to prevent Mach disk formation and particle growth by coagulation. Controlled particle growth keeps the production process stable. With CESS, we produced piroxicam nanoparticles, 60 mg/h, featuring narrow size distribution (176 ± 53 nm). Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

REVIEWS OF TOPICAL PROBLEMS: Large-scale star formation in galaxies

NASA Astrophysics Data System (ADS)

Efremov, Yurii N.; Chernin, Artur D.

2003-01-01

A brief review is given of the history of modern ideas on the ongoing star formation process in the gaseous disks of galaxies. Recent studies demonstrate the key role of the interplay between the gas self-gravitation and its turbulent motions. The large scale supersonic gas flows create structures of enhanced density which then give rise to the gravitational condensation of gas into stars and star clusters. Formation of star clusters, associations and complexes is considered, as well as the possibility of isolated star formation. Special emphasis is placed on star formation under the action of ram pressure.

Spinal subarachnoid space pressure measurements in an in vitro spinal stenosis model: implications on syringomyelia theories.

PubMed

Martin, Bryn A; Labuda, Richard; Royston, Thomas J; Oshinski, John N; Iskandar, Bermans; Loth, Francis

2010-11-01

Full explanation for the pathogenesis of syringomyelia (SM), a neuropathology characterized by the formation of a cystic cavity (syrinx) in the spinal cord (SC), has not yet been provided. It has been hypothesized that abnormal cerebrospinal fluid (CSF) pressure, caused by subarachnoid space (SAS) flow blockage (stenosis), is an underlying cause of syrinx formation and subsequent pain in the patient. However, paucity in detailed in vivo pressure data has made theoretical explanations for the syrinx difficult to reconcile. In order to understand the complex pressure environment, four simplified in vitro models were constructed to have anatomical similarities with post-traumatic SM and Chiari malformation related SM. Experimental geometry and properties were based on in vivo data and incorporated pertinent elements such as a realistic CSF flow waveform, spinal stenosis, syrinx, flexible SC, and flexible spinal column. The presence of a spinal stenosis in the SAS caused peak-to-peak cerebrospinal fluid CSF pressure fluctuations to increase rostral to the stenosis. Pressure with both stenosis and syrinx present was complex. Overall, the interaction of the syrinx and stenosis resulted in a diastolic valve mechanism and rostral tensioning of the SC. In all experiments, the blockage was shown to increase and dissociate SAS pressure, while the axial pressure distribution in the syrinx remained uniform. These results highlight the importance of the properties of the SC and spinal SAS, such as compliance and permeability, and provide data for comparison with computational models. Further research examining the influence of stenosis size and location, and the importance of tissue properties, is warranted.

Formic Acid Formation by Clostridium ljungdahlii at Elevated Pressures of Carbon Dioxide and Hydrogen

PubMed Central

Oswald, Florian; Stoll, I. Katharina; Zwick, Michaela; Herbig, Sophia; Sauer, Jörg; Boukis, Nikolaos; Neumann, Anke

2018-01-01

Low productivities of bioprocesses using gaseous carbon and energy sources are usually caused by the low solubility of those gases (e.g., H2 and CO). It has been suggested that increasing the partial pressure of those gases will result in higher dissolved concentrations and should, therefore, be helpful to overcome this obstacle. Investigations of the late 1980s with mixtures of hydrogen and carbon monoxide showed inhibitory effects of carbon monoxide partial pressures above 0.8 bar. Avoiding any effects of carbon monoxide, we investigate growth and product formation of Clostridium ljungdahlii at absolute process pressures of 1, 4, and 7 bar in batch stirred tank reactor cultivations with carbon dioxide and hydrogen as sole gaseous carbon and energy source. With increasing process pressure, the product spectrum shifts from mainly acetic acid and ethanol to almost only formic acid at a total system pressure of 7 bar. On the other hand, no significant changes in overall product yield can be observed. By keeping the amount of substance flow rate constant instead of the volumetric gas feed rate when increasing the process pressure, we increased the overall product yield of 7.5 times of what has been previously reported in the literature. After 90 h of cultivation at a total pressure of 7 bar a total of 4 g L−1 of products is produced consisting of 82.7 % formic acid, 15.6 % acetic acid, and 1.7 % ethanol. PMID:29484294

Review of A 2B 2O 7 Pyrochlore Response to Irradiation and Pressure

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

Lang, Maik; Zhang, Fuxiang; Zhang, Jiaming

2010-10-01

This article reviews recent research on swift heavy-ion irradiations and high-pressure studies on pyrochlores of the Gd 2Zr 2-xTi xO 7 binary. Applying three complementary analytical techniques (synchrotron X-ray diffraction, Raman spectroscopy and transmission electron microscopy) allowed for the investigation of the response of pyrochlore to irradiation and/or pressure. The chemical composition of pyrochlore has a strong effect on the character and energetics of the type of structural modifications that can be obtained under pressure or irradiation: For Ti-rich pyrochlores, the crystalline-to-amorphous transition is the dominant process. When Zr is substituted for Ti, an order–disorder transformation to the defect-fluorite structuremore » becomes the increasingly dominant process. Except for Gd 2Zr 2O 7, single ion tracks in pyrochlore consist of an amorphous core, surrounded by a crystalline, but disordered, defect-fluorite shell. This shell is surrounded by a defect-rich pyrochlore region. In contrast to similar effects observed when pressure or irradiation are applied separately, the response of the pyrochlore structure is significantly different when it is exposed simultaneously to pressure and irradiation. The combination of relativistic heavy ions with high pressure results in the formation of a new metastable pyrochlore phase. TEM and quantum–mechanical calculations suggest that these novel structural modifications are caused by the formation of nanocrystals and the modified energetics of nanomaterials.« less

Review of A2B2O7 Pyrochlore Response to Irradiation and Pressure

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

Lang, M.; Zhang, F; Zhang, J

2010-01-01

This article reviews recent research on swift heavy-ion irradiations and high-pressure studies on pyrochlores of the Gd{sub 2}Zr{sub 2-x}Ti{sub x}O{sub 7} binary. Applying three complementary analytical techniques (synchrotron X-ray diffraction, Raman spectroscopy and transmission electron microscopy) allowed for the investigation of the response of pyrochlore to irradiation and/or pressure. The chemical composition of pyrochlore has a strong effect on the character and energetics of the type of structural modifications that can be obtained under pressure or irradiation: For Ti-rich pyrochlores, the crystalline-to-amorphous transition is the dominant process. When Zr is substituted for Ti, an order-disorder transformation to the defect-fluorite structuremore » becomes the increasingly dominant process. Except for Gd{sub 2}Zr{sub 2}O{sub 7}, single ion tracks in pyrochlore consist of an amorphous core, surrounded by a crystalline, but disordered, defect-fluorite shell. This shell is surrounded by a defect-rich pyrochlore region. In contrast to similar effects observed when pressure or irradiation are applied separately, the response of the pyrochlore structure is significantly different when it is exposed simultaneously to pressure and irradiation. The combination of relativistic heavy ions with high pressure results in the formation of a new metastable pyrochlore phase. TEM and quantum-mechanical calculations suggest that these novel structural modifications are caused by the formation of nanocrystals and the modified energetics of nanomaterials.« less

Phase formation in the (1-y)BiFeO{sub 3}-yBiScO{sub 3} system under ambient and high pressure

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

Salak, A.N., E-mail: salak@ua.pt; Khalyavin, D.D., E-mail: dmitry.khalyavin@stfc.ac.uk; Pushkarev, A.V.

Formation and thermal stability of perovskite phases in the BiFe{sub 1-y}Sc{sub y}O{sub 3} system (0≤y≤0.70) were studied. When the iron-to-scandium substitution rate does not exceed about 15 at%, the single-phase perovskite ceramics with the rhombohedral R3c symmetry (as that of the parent compound, BiFeO{sub 3}) can be prepared from the stoichiometric mixture of the respective oxides at ambient pressure. Thermal treatment of the oxide mixtures with a higher content of scandium results in formation of two main phases, namely a BiFeO{sub 3}-like R3c phase and a cubic (I23) sillenite-type phase based on γ-Bi{sub 2}O{sub 3}. Single-phase perovskite ceramics of themore » BiFe{sub 1-y}Sc{sub y}O{sub 3} composition were synthesized under high pressure from the thermally treated oxide mixtures. When y is between 0 and 0.25 the high-pressure prepared phase is the rhombohedral R3c with the √2a{sub p}×√2a{sub p}×2√3a{sub p} superstructure (a{sub p} ~ 4 Å is the pseudocubic perovskite unit-cell parameter). The orthorhombic Pnma phase (√2a{sub p}×4a{sub p}×2√2a{sub p}) was obtained in the range of 0.30≤y≤0.60, while the monoclinic C2/c phase (√6a{sub p}×√2a{sub p}×√6a{sub p}) is formed when y=0.70. The normalized unit-cell volume drops at the crossover from the rhombohedral to the orthorhombic composition range. The perovskite BiFe{sub 1-y}Sc{sub y}O{sub 3} phases prepared under high pressure are metastable regardless of their symmetry. At ambient pressure, the phases with the compositions in the ranges of 0.20≤y≤0.25, 0.30≤y<0.50 and 0.50≤y≤0.70 start to decompose above 970, 920 and 870 K, respectively. - Graphical abstract: Formation of perovskite phases in the BiFe{sub 1-y}Sc{sub y}O{sub 3} system when y≥0.15 requires application of pressure of several GPa. The phases formed under high pressure: R3c (0.20≤y≤0.25), Pnma (0.30≤y≤0.60) and C2/c (y≥0.70) are metastable. - Highlights: • Maximal Fe-to-Sc substitution rate in BiFeO{sub 3} at ambient pressure is about 15 at%. • R3c → Pnma → C2/c phase sequence in high-pressure prepared BiFe{sub 1-y}Sc{sub y}O{sub 3} ceramics. • The perovskite BiFe{sub 1-y}Sc{sub y}O{sub 3} phases formed under high pressure are metastable.« less

Cost and Performance Report In-Situ Remediation of MTBE Contaminated Aquifers Using Propane Biosparging

DTIC Science & Technology

2003-12-01

by pneumatic or hydraulic fracturing . Pneumatic fracturing (PF) uses the injection of pressurized air 47 (up to 175 psi) in to the formation that...contaminants. Hydraulic fracturing is similar to PF with the exception that water is used and at pressures as high as 2000 psi. Technical questions

Pressure Groups and Education Policy and Administration in Australia.

ERIC Educational Resources Information Center

Harman, G. S.

This report discusses the role and function of pressure groups with regard to policy formation and implementation in Australian education. It is addressed to the scholar interested in gaining further insight into the structure and operation of the political and educational systems, as well as to those engaged or involved in the whole educational…

Non-solar noble gas abundances in the atmosphere of Jupiter

NASA Technical Reports Server (NTRS)

Lunine, Jonathan I.; Stevenson, David J.

1986-01-01

The thermodynamic stability of clathrate hydrate is calculated to predict the formation conditions corresponding to a range of solar system parameters. The calculations were performed using the statistical mechanical theory developed by van der Waals and Platteeuw (1959) and existing experimental data concerning clathrate hydrate and its components. Dissociation pressures and partition functions (Langmuir constants) are predicted at low pressure for CO clathrate (hydrate) using the properties of chemicals similar to CO. It is argued that nonsolar but well constrained noble gas abundances may be measurable by the Galileo spacecraft in the Jovian atmosphere if the observed carbon enhancement is due to bombardment of the atmosphere by clathrate-bearing planetesimals sometime after planetary formation. The noble gas abundances of the Jovian satellite Titan are predicted, assuming that most of the methane in Titan is accreted as clathrate. It is suggested that under thermodynamically appropriate conditions, complete clathration of water ice could have occurred in high-pressure nebulas around giant planets, but probably not in the outer solar nebula. The stability of clathrate in other pressure ranges is also discussed.

Piezochromism and structural and electronic properties of benz[a]anthracene under pressure

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

Cai, Weizhao; Zhang, Rong; Yao, Yansun

2017-01-31

We report a combined experimental and theoretical study of the high pressure behavior of a herringbone-type hydrocarbon benz[a]anthracene (BaA) using fluorescence spectroscopy, X-ray diffraction, optical absorption, photoconductivity measurements, and first-principles density functional theory (DFT) calculations. The ambient-pressure molecular solid phase of BaA was found to be stable up to ~15.0 GPa. Increasing the external pressure within this region would induce a reversible piezochromic colour change in the sample, from yellow-green to light brown. The reversibility of the colour change was confirmed by both optical observations and fluorescence measurements. Further compression beyond 15 GPa leads to polymerization of the sample andmore » formation of an amorphous hydrogenated carbon. The low pressure crystalline phase is not recoverable when the sample is decompressed from pressure above 15 GPa. DFT investigation of the structures at zero temperature suggests that the formation of a crystalline polymeric phase can take place between 30 and 117 GPa, however the kinetic barriers hinder the process at low pressure regions. The phase transition is therefore suggested to proceed along a gradual transition path to an amorphous phase at a lower reaction threshold, activated by finite temperature effects. Optical absorption measurements reveal that the band gap of BaA decreases at high pressure, from 2.4 eV at 0.5 GPa to 1.0 eV at 50.6 GPa. The DFT calculations further suggest that the band gap of BaA in the molecular phase could reduce to ~0.1 eV at 117 GPa. Photoconductivity measurements show a continuous increase of photocurrent in the molecular phase region, which most likely originated from the increase of carrier mobility under pressure.« less

A comparative study on the analytical utility of atmospheric and low-pressure MALDI sources for the mass spectrometric characterization of peptides.

PubMed

Moskovets, Eugene; Misharin, Alexander; Laiko, Viktor; Doroshenko, Vladimir

2016-07-15

A comparative MS study was conducted on the analytical performance of two matrix-assisted laser desorption/ionization (MALDI) sources that operated at either low pressure (∼1Torr) or at atmospheric pressure. In both cases, the MALDI sources were attached to a linear ion trap mass spectrometer equipped with a two-stage ion funnel. The obtained results indicate that the limits of detection, in the analysis of identical peptide samples, were much lower with the source that was operated slightly below the 1-Torr pressure. In the low-pressure (LP) MALDI source, ion signals were observed at a laser fluence that was considerably lower than the one determining the appearance of ion signals in the atmospheric pressure (AP) MALDI source. When the near-threshold laser fluences were used to record MALDI MS spectra at 1-Torr and 750-Torr pressures, the level of chemical noise at the 1-Torr pressure was much lower compared to that at AP. The dependency of the analyte ion signals on the accelerating field which dragged the ions from the MALDI plate to the MS analyzer are presented for the LP and AP MALDI sources. The study indicates that the laser fluence, background gas pressure, and field accelerating the ions away from a MALDI plate were the main parameters which determined the ion yield, signal-to-noise (S/N) ratios, the fragmentation of the analyte ions, and adduct formation in the LP and AP MALDI MS methods. The presented results can be helpful for a deeper insight into the mechanisms responsible for the ion formation in MALDI. Copyright © 2016 Elsevier Inc. All rights reserved.

Creating potentiometric surfaces from combined water well and oil well data in the midcontinent of the United States

USGS Publications Warehouse

Gianoutsos, Nicholas J.; Nelson, Philip H.

2013-01-01

For years, hydrologists have defined potentiometric surfaces using measured hydraulic-head values in water wells from aquifers. Down-dip, the oil and gas industry is also interested in the formation pressures of many of the same geologic formations for the purpose of hydrocarbon recovery. In oil and gas exploration, drillstem tests (DSTs) provide the formation pressure for a given depth interval in a well. These DST measurements can be used to calculate hydraulic-head values in deep hydrocarbon-bearing formations in areas where water wells do not exist. Unlike hydraulic-head measurements in water wells, which have a low number of problematic data points (outliers), only a small subset of the DST data measure true formation pressures. Using 3D imaging capabilities to view and clean the data, we have developed a process to estimate potentiometric surfaces from erratic DST data sets of hydrocarbon-bearing formations in the midcontinent of the U.S. The analysis indicates that the potentiometric surface is more readily defined through human interpretation of the chaotic DST data sets rather than through the application of filtering and geostatistical analysis. The data are viewed as a series of narrow, 400-mile-long swaths and a 2D viewer is used to select a subset of hydraulic-head values that represent the potentiometric surface. The user-selected subsets for each swath are then combined into one data set for each formation. These data are then joined with the hydraulic-head values from water wells to define the 3D potentiometric surfaces. The final product is an interactive, 3D digital display containing: (1) the subsurface structure of the formation, (2) the cluster of DST-derived hydraulic head values, (3) the user-selected subset of hydraulic-head values that define the potentiometric surface, (4) the hydraulic-head measurements from the corresponding shallow aquifer, (5) the resulting potentiometric surface encompassing both oil and gas and water wells, and (6) the land surface elevation of the region. Examples from the midcontinent of the United States, specifically Kansas, Oklahoma, and parts of adjacent states illustrate the process.

Fallon, Nevada FORGE Well 21-31 Wireline Logs

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

Blankenship, Doug

Included are the following wireline logs from the Fallon FORGE Well 21-31. Ormat_Forge 21-31_8.5 inch section: FMI data in PDF and DLIS formats; MSCT data in PDF format; Pressure and Temperature data in PDF, LAS, and DLIS formats; Sonic Scanner data in PDF, DLIS, and LAS formats (LAS format contains Stoneley Slowness, Shear Slowness, and Compressional Slowness logs); Triple Combo in PDF, DLIS, and LAS formats; and USIT data in DLIS and PDF formats. Ormat_Forge_21-31_12.25 inch section: Resistivity data in PDF and LAS formats; Sonic Scanner data in PDF, DLIS, and LAS formats (LAS format contains Stoneley Slowness, Shear Slowness,more » and Compressional Slowness logs); Triple Combo in PDF and LAS formats; and Caliper data in PDF format (DLIS format for caliper data is included in the Sonic Scanner DLIS).« less

Oscillation-Mark Formation and Liquid-Slag Consumption in Continuous Casting Mold

NASA Astrophysics Data System (ADS)

Yang, Jie; Meng, Xiangning; Wang, Ning; Zhu, Miaoyong

2017-04-01

Traditional understanding on the complex multiphysics phenomenon of the meniscus in the oscillating mold for continuously cast steel, including oscillation-mark formation and liquid-slag consumption, has never considered the shape influence of the flux channel between the mold wall and the solidifying shell surface. Based on the reciprocating oscillation of mold, this study was carried out to calculate theoretically the periodic pressure and the liquid-slag layer thickness in the flux channel for the upper and the lower meniscus that possess different shapes in combination with a transient equilibrium profile of the flux channel as well as the sinusoidal and the nonsinusoidal oscillation modes of mold. The effect of flux channel shape on the multiphysics phenomenon in the meniscus was determined by the physical oscillation simulation by using an experimental cold model mold. The results show that the shape difference between the upper and the lower meniscus leads to the opposite direction of pressure in the flux channel. The pressure in the opposite direction plays a respective role in oscillation-mark formation and liquid-slag consumption in an oscillation cycle of mold, and thus, it makes a new mechanism for explaining the multiphysics phenomenon in the meniscus. The oscillation mark is initially formed by the rapid increase of positive channel pressure in the upper meniscus, and most of the liquid slag is infiltrated into the flux channel by the negative channel pressure in the lower meniscus from the end of a positive strip time to the beginning of the next positive strip time, including the negative strip time in between. Furthermore, the physical characteristics of the lubrication behavior in the meniscus are summarized, including liquid-slag infiltration, solidifying shell deformation, and the thickness change of the liquid-slag layer.

Negative pressure ventilation decreases inflammation and lung edema during normothermic ex-vivo lung perfusion.

PubMed

Aboelnazar, Nader S; Himmat, Sayed; Hatami, Sanaz; White, Christopher W; Burhani, Mohamad S; Dromparis, Peter; Matsumura, Nobutoshi; Tian, Ganghong; Dyck, Jason R B; Mengel, Michael; Freed, Darren H; Nagendran, Jayan

2018-04-01

Normothermic ex-vivo lung perfusion (EVLP) using positive pressure ventilation (PPV) and both acellular and red blood cell (RBC)-based perfusate solutions have increased the rate of donor organ utilization. We sought to determine whether a negative pressure ventilation (NPV) strategy would improve donor lung assessment during EVLP. Thirty-two pig lungs were perfused ex vivo for 12 hours in a normothermic state, and were allocated equally to 4 groups according to the mode of ventilation (positive pressure ventilation [PPV] vs NPV) and perfusate composition (acellular vs RBC). The impact of ventilation strategy on the preservation of 6 unutilized human donor lungs was also evaluated. Physiologic parameters, cytokine profiles, lung injury, bullae and edema formation were compared between treatment groups. Perfused lungs demonstrated acceptable oxygenation (partial pressure of arterial oxygen/fraction of inspired oxygen ratio >350 mm Hg) and physiologic parameters. However, there was less generation of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interleukin-8) in human and pig lungs perfused, irrespective of perfusate solution used, when comparing NPV with PPV (p < 0.05), and a reduction in bullae formation with an NPV modality (p = 0.02). Pig lungs developed less edema with NPV (p < 0.01), and EVLP using an acellular perfusate solution had greater edema formation, irrespective of ventilation strategy (p = 0.01). Interestingly, human lungs perfused with NPV developed negative edema, or "drying" (p < 0.01), and lower composite acute lung injury (p < 0.01). Utilization of an NPV strategy during extended EVLP is associated with significantly less inflammation, and lung injury, irrespective of perfusate solution composition. Copyright © 2018 International Society for the Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.

Therapeutic Effect of External Application of Ligustrazine Combined with Holistic Nursing on Pressure Sores.

PubMed

Niu, Junzhi; Han, Lin; Gong, Fen

2016-08-15

BACKGROUND This study aimed to explore the therapeutic effect of external application of ligustrazine combined with holistic nursing on pressure sores, as well as the underlying mechanism. MATERIAL AND METHODS From February 2014 to March 2015, a total of 32 patients with Phase II and Phase III pressure sores were enrolled and randomly assigned to an experimental group or a control group. The clinical data were comparable between the 2 groups. In addition to holistic nursing, the patients in the experimental group received 4 weeks of continuous external application of ligustrazine, whereas patients in the control group received compound clotrimazole cream. Therapeutic effect and healing time were recorded. HaCaT cells were used as an in vitro model for mechanism analysis of the effect of ligustrazine in treating pressure sores. After culturing with different concentrations of ligustrazine or the inhibitor of AKT (LY294002) for 72 h, cell viability, clone formation numbers, and levels of phosphatidyl inositol 3-kinase (PI3K), p-AKT, and p-mammalian target of rapamycin (mTOR) were determined. RESULTS Compared to the control group, the total effective rate in the experimental group was significantly higher, and the healing time was significantly reduced. Cell viability and clone formation numbers were significantly upregulated by ligustrazine in a dose-dependent manner. Both the cell viability and clone formation numbers were significantly inhibited by application of LY294002. CONCLUSIONS Our results suggest that ligustrazine combined with holistic nursing is an effective treatment of pressure sores. The protective effect may be associated with the promotion of cell growth by activation of the PI3K/AKT pathway.

Therapeutic Effect of External Application of Ligustrazine Combined with Holistic Nursing on Pressure Sores

PubMed Central

Niu, Junzhi; Han, Lin; Gong, Fen

2016-01-01

Background This study aimed to explore the therapeutic effect of external application of ligustrazine combined with holistic nursing on pressure sores, as well as the underlying mechanism. Material/Methods From February 2014 to March 2015, a total of 32 patients with Phase II and Phase III pressure sores were enrolled and randomly assigned to an experimental group or a control group. The clinical data were comparable between the 2 groups. In addition to holistic nursing, the patients in the experimental group received 4 weeks of continuous external application of ligustrazine, whereas patients in the control group received compound clotrimazole cream. Therapeutic effect and healing time were recorded. HaCaT cells were used as an in vitro model for mechanism analysis of the effect of ligustrazine in treating pressure sores. After culturing with different concentrations of ligustrazine or the inhibitor of AKT (LY294002) for 72 h, cell viability, clone formation numbers, and levels of phosphatidyl inositol 3-kinase (PI3K), p-AKT, and p-mammalian target of rapamycin (mTOR) were determined. Results Compared to the control group, the total effective rate in the experimental group was significantly higher, and the healing time was significantly reduced. Cell viability and clone formation numbers were significantly upregulated by ligustrazine in a dose-dependent manner. Both the cell viability and clone formation numbers were significantly inhibited by application of LY294002. Conclusions Our results suggest that ligustrazine combined with holistic nursing is an effective treatment of pressure sores. The protective effect may be associated with the promotion of cell growth by activation of the PI3K/AKT pathway. PMID:27523814

Quenching star formation with quasar outflows launched by trapped IR radiation

NASA Astrophysics Data System (ADS)

Costa, Tiago; Rosdahl, Joakim; Sijacki, Debora; Haehnelt, Martin G.

2018-06-01

We present cosmological radiation-hydrodynamic simulations, performed with the code RAMSES-RT, of radiatively-driven outflows in a massive quasar host halo at z = 6. Our simulations include both single- and multi-scattered radiation pressure on dust from a quasar and are compared against simulations performed with thermal feedback. For radiation pressure-driving, we show that there is a critical quasar luminosity above which a galactic outflow is launched, set by the equilibrium of gravitational and radiation forces. While this critical luminosity is unrealistically high in the single-scattering limit for plausible black hole masses, it is in line with a ≈ 3 × 10^9 M_⊙ black hole accreting at its Eddington limit, if infrared (IR) multi-scattering radiation pressure is included. The outflows are fast (v ≳ 1000 km s^{-1}) and strongly mass-loaded with peak mass outflow rates ≈ 10^3 - 10^4 M_⊙ yr^{-1}, but short-lived (< 10 Myr). Outflowing material is multi-phase, though predominantly composed of cool gas, forming via a thermal instability in the shocked swept-up component. Radiation pressure- and thermally-driven outflows both affect their host galaxies significantly, but in different, complementary ways. Thermally-driven outflows couple more efficiently to diffuse halo gas, generating more powerful, hotter and more volume-filling outflows. IR radiation, through its ability to penetrate dense gas via diffusion, is more efficient at ejecting gas from the bulge. The combination of gas ejection through outflows with internal pressurisation by trapped IR radiation leads to a complete shut down of star formation in the bulge. We hence argue that radiation pressure-driven feedback may be an important ingredient in regulating star formation in compact starbursts, especially during the quasar's `obscured' phase.

Stem Hydraulic Conductivity depends on the Pressure at Which It Is Measured and How This Dependence Can Be Used to Assess the Tempo of Bubble Pressurization in Recently Cavitated Vessels1[OPEN

PubMed Central

Liu, Jinyu; Tyree, Melvin T.

2015-01-01

Cavitation of water in xylem vessels followed by embolism formation has been authenticated for more than 40 years. Embolism formation involves the gradual buildup of bubble pressure (air) to atmospheric pressure as demanded by Henry’s law of equilibrium between gaseous and liquid phases. However, the tempo of pressure increase has not been quantified. In this report, we show that the rate of pressurization of embolized vessels is controlled by both fast and slow kinetics, where both tempos are controlled by diffusion but over different spatial scales. The fast tempo involves a localized diffusion from endogenous sources: over a distance of about 0.05 mm from water-filled wood to the nearest embolized vessels; this process, in theory, should take <2 min. The slow tempo involves diffusion of air from exogenous sources (outside the stem). The latter diffusion process is slower because of the increased distance of diffusion of up to 4 mm. Radial diffusion models and experimental measurements both confirm that the average time constant is >17 h, with complete equilibrium requiring 1 to 2 d. The implications of these timescales for the standard methods of measuring percentage loss of hydraulic conductivity are discussed in theory and deserve more research in future. PMID:26468516

Stem Hydraulic Conductivity depends on the Pressure at Which It Is Measured and How This Dependence Can Be Used to Assess the Tempo of Bubble Pressurization in Recently Cavitated Vessels.

PubMed

Wang, Yujie; Liu, Jinyu; Tyree, Melvin T

2015-12-01

Cavitation of water in xylem vessels followed by embolism formation has been authenticated for more than 40 years. Embolism formation involves the gradual buildup of bubble pressure (air) to atmospheric pressure as demanded by Henry's law of equilibrium between gaseous and liquid phases. However, the tempo of pressure increase has not been quantified. In this report, we show that the rate of pressurization of embolized vessels is controlled by both fast and slow kinetics, where both tempos are controlled by diffusion but over different spatial scales. The fast tempo involves a localized diffusion from endogenous sources: over a distance of about 0.05 mm from water-filled wood to the nearest embolized vessels; this process, in theory, should take <2 min. The slow tempo involves diffusion of air from exogenous sources (outside the stem). The latter diffusion process is slower because of the increased distance of diffusion of up to 4 mm. Radial diffusion models and experimental measurements both confirm that the average time constant is >17 h, with complete equilibrium requiring 1 to 2 d. The implications of these timescales for the standard methods of measuring percentage loss of hydraulic conductivity are discussed in theory and deserve more research in future. © 2015 American Society of Plant Biologists. All Rights Reserved.

Galactic star formation enhanced and quenched by ram pressure in groups and clusters

NASA Astrophysics Data System (ADS)

Bekki, Kenji

2014-02-01

We investigate how ram pressure of intragroup and intracluster medium can influence the spatial and temporal variations of star formation (SF) of disc galaxies with halo masses (Mh) ranging from 1010 to 1012 M⊙ (i.e. from dwarf irregular to Milky Way-type) in groups and clusters with 1013 ≤ Mh/M⊙ ≤ 1015 by using numerical simulations with a new model for time-varying ram pressure. The long-term evolution of SF rates and Hα morphologies corresponding to the distributions of star-forming regions are particularly investigated for different model parameters. The principal results are as follows. Whether ram pressure can enhance or reduce SF depends on Mh of disc galaxies and inclination angles of gas discs with respect to their orbital directions for a given orbit and a given environment. For example, SF can be moderately enhanced in disc galaxies with Mh = 1012 M⊙ at the pericentre passages in a cluster with Mh = 1014 M⊙ whereas it can be completely shut down (`quenching') for low-mass discs with Mh = 1010 M⊙. Ram pressure can reduce the Hα-to-optical-disc-size ratios of discs and the level of the reduction depends on Mh and orbits of disc galaxies for a given environment. Disc galaxies under strong ram pressure show characteristic Hα morphologies such as ring-like, one-sided and crescent-like distributions.

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.

Mechanism and Kinetics of Ethanol Coupling to Butanol over Hydroxyapatite

DOE PAGES

Ho, Christopher R.; Shylesh, Sankaranarayanapillai; Bell, Alexis T.

2015-12-23

The mechanism and kinetics for ethanol coupling to n-butanol over hydroxyapatite (HAP) were investigated at 573-613 K. In situ titration experiments show that the active sites for acetaldehyde and butanol formation are different. In combination with FTIR studies, it was found that ethanol dehydrogenation is catalyzed by Ca-O sites, whereas condensation of acetaldehyde is catalyzed by CaO/PO 4 3- pairs. Measurements of the reaction kinetics at various ethanol (3.5-9.4 kPa) and acetaldehyde (0.055-0.12 kPa) partial pressures reveal that direct condensation involving two ethanol molecules does not play a significant role in butanol formation; instead, n-butanol is formed via a Guerbetmore » pathway. At a constant acetaldehyde pressure, enolate formation is rate-limiting, and ethanol inhibits acetaldehyde condensation rates by competitive adsorption. A model of the reaction kinetics consistent with all experimental observations is developed.« less

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

Ho, Christopher R.; Shylesh, Sankaranarayanapillai; Bell, Alexis T.

The mechanism and kinetics for ethanol coupling to n-butanol over hydroxyapatite (HAP) were investigated at 573-613 K. In situ titration experiments show that the active sites for acetaldehyde and butanol formation are different. In combination with FTIR studies, it was found that ethanol dehydrogenation is catalyzed by Ca-O sites, whereas condensation of acetaldehyde is catalyzed by CaO/PO 4 3- pairs. Measurements of the reaction kinetics at various ethanol (3.5-9.4 kPa) and acetaldehyde (0.055-0.12 kPa) partial pressures reveal that direct condensation involving two ethanol molecules does not play a significant role in butanol formation; instead, n-butanol is formed via a Guerbetmore » pathway. At a constant acetaldehyde pressure, enolate formation is rate-limiting, and ethanol inhibits acetaldehyde condensation rates by competitive adsorption. A model of the reaction kinetics consistent with all experimental observations is developed.« less

a Fractal Permeability Model Coupling Boundary-Layer Effect for Tight Oil Reservoirs

NASA Astrophysics Data System (ADS)

Wang, Fuyong; Liu, Zhichao; Jiao, Liang; Wang, Congle; Guo, Hu

A fractal permeability model coupling non-flowing boundary-layer effect for tight oil reservoirs was proposed. Firstly, pore structures of tight formations were characterized with fractal theory. Then, with the empirical equation of boundary-layer thickness, Hagen-Poiseuille equation and fractal theory, a fractal torturous capillary tube model coupled with boundary-layer effect was developed, and verified with experimental data. Finally, the parameters influencing effective liquid permeability were quantitatively investigated. The research results show that effective liquid permeability of tight formations is not only decided by pore structures, but also affected by boundary-layer distributions, and effective liquid permeability is the function of fluid type, fluid viscosity, pressure gradient, fractal dimension, tortuosity fractal dimension, minimum pore radius and maximum pore radius. For the tight formations dominated with nanoscale pores, boundary-layer effect can significantly reduce effective liquid permeability, especially under low pressure gradient.

Automated X-Ray Diffraction of Irradiated Materials

DOE PAGES

Rodman, John; Lin, Yuewei; Sprouster, David; ...

2017-10-26

Synchrotron-based X-ray diffraction (XRD) and small-angle Xray scattering (SAXS) characterization techniques used on unirradiated and irradiated reactor pressure vessel steels yield large amounts of data. Machine learning techniques, including PCA, offer a novel method of analyzing and visualizing these large data sets in order to determine the effects of chemistry and irradiation conditions on the formation of radiation induced precipitates. In order to run analysis on these data sets, preprocessing must be carried out to convert the data to a usable format and mask the 2-D detector images to account for experimental variations. Once the data has been preprocessed, itmore » can be organized and visualized using principal component analysis (PCA), multi-dimensional scaling, and k-means clustering. In conclusion, from these techniques, it is shown that sample chemistry has a notable effect on the formation of the radiation induced precipitates in reactor pressure vessel steels.« less

Tendon–bone contact pressure and biomechanical evaluation of a modified suture-bridge technique for rotator cuff repair

PubMed Central

Geyer, Michael; Büschken, Meike; Buchhorn, Gottfried H.; Spahn, Gunter; Klinger, Hans-Michael

2009-01-01

The aim of the study was to evaluate the time-zero mechanical and footprint properties of a suture-bridge technique for rotator cuff repair in an animal model. Thirty fresh-frozen sheep shoulders were randomly assigned among three investigation groups: (1) cyclic loading, (2) load-to-failure testing, and (3) tendon–bone interface contact pressure measurement. Shoulders were cyclically loaded from 10 to 180 N and displacement to gap formation of 5- and 10-mm at the repair site. Cycles to failure were determined. Additionally, the ultimate tensile strength and stiffness were verified along with the mode of failure. The average contact pressure and pressure pattern were investigated using a pressure-sensitive film system. All of the specimens resisted against 3,000 cycles and none of them reached a gap formation of 10 mm. The number of cycles to 5-mm gap formation was 2,884.5 ± 96.8 cycles. The ultimate tensile strength was 565.8 ± 17.8 N and stiffness was 173.7 ± 9.9 N/mm. The entire specimen presented a unique mode of failure as it is well known in using high strength sutures by pulling them through the tendon. We observed a mean contact pressure of 1.19 ± 0.03 MPa, applied on the footprint area. The fundamental results of our study support the use of a suture-bridge technique for optimising the conditions of the healing biology of a reconstructed rotator cuff tendon. Nevertheless, an individual estimation has to be done if using the suture-bridge technique clinically. Further investigation is necessary to evaluate the cell biological healing process in order to achieve further sufficient advancements in rotator cuff repair. PMID:19826786

Solitary waves: a possible mechanism for rapid fluid transport in low permeability porous media

NASA Astrophysics Data System (ADS)

Appold, Martin; Joshi, Ajit

2014-05-01

Elastic porous media in which the rate of fluid pressure generation is high relative to the rate of fluid pressure diffusion and whose permeabilities are a sensitive function of effective stress may generate solitary waves manifest as discrete pulses of elevated pore pressure and porosity that can travel at velocities that are orders of magnitude greater than the velocities of the pore fluids in the background Darcian flow regime. Solitary waves may thus be important vehicles for fluid transport through porous media whose permeabilities are otherwise too low to allow significant rates of flow. Solitary waves have been hypothesized for diverse geologic settings and processes, including magmatic hydrothermal ore formation, magma transport, fault slip in accretionary wedges and at transform plate boundaries, and primary hydrocarbon migration in sedimentary basins. The present study has focused on solitary waves as agents of oil and methane transport through numerical simulation of their origin and behavior. The results show solitary waves to have limited capacity for transporting oil for several reasons: (1) the rate of fluid pressure generation by typical mechanisms like compaction disequilibrium and hydrocarbon formation is too low to allow solitary waves to form unless permeability is exceptionally low (10-24 to 10-25 m2), (2) solitary waves are only able to ascend no more than 1-2 km before dissipating to ambient pressure and porosity values, (3) the waves are too small and the frequency of their formation is too low to account for the amount of oil observed in the reservoirs that they have been hypothesized to feed. Solitary waves have been found to be more effective at transporting methane because of its lower density and viscosity compared to oil, provided that a mechanism for rapid pressure generation exists and permeabilities are very low. If those conditions exist, then solitary waves can ascend over two kilometers at rates on the order of 100's of meters per year compared to millimeters per year for solitary waves transporting oil.

Experimental study of cake formation on heat treated and membrane coated needle felts in a pilot scale pulse jet bag filter using optical in-situ cake height measurement

PubMed Central

Saleem, Mahmood; Khan, Rafi Ullah; Tahir, M. Suleman; Krammer, Gernot

2011-01-01

Pulse-jet bag filters are frequently employed for particle removal from off gases. Separated solids form a layer on the permeable filter media called filter cake. The cake is responsible for increasing pressure drop. Therefore, the cake has to be detached at a predefined upper pressure drop limit or at predefined time intervals. Thus the process is intrinsically semi-continuous. The cake formation and cake detachment are interdependent and may influence the performance of the filter. Therefore, understanding formation and detachment of filter cake is important. In this regard, the filter media is the key component in the system. Needle felts are the most commonly used media in bag filters. Cake formation studies with heat treated and membrane coated needle felts in pilot scale pulse jet bag filter were carried out. The data is processed according to the procedures that were published already [Powder Technology, Volume 173, Issue 2, 19 April 2007, Pages 93–106]. Pressure drop evolution, cake height distribution evolution, cake patches area distribution and their characterization using fractal analysis on different needle felts are presented here. It is observed that concavity of pressure drop curve for membrane coated needle felt is principally caused by presence of inhomogeneous cake area load whereas it is inherent for heat treated media. Presence of residual cake enhances the concavity of pressure drop at the start of filtration cycle. Patchy cleaning is observed only when jet pulse pressure is too low and unable to provide the necessary force to detach the cake. The border line is very sharp. Based on experiments with limestone dust and three types of needle felts, for the jet pulse pressure above 4 bar and filtration velocity below 50 mm/s, cake is detached completely except a thin residual layer (100–200 μm). Uniformity and smoothness of residual cake depends on the surface characteristics of the filter media. Cake height distribution of residual cake and newly formed cake during filtration prevails. The patch size analysis and fractal analysis reveal that residual cake grow in size (latterly) following regeneration initially on the base with edges smearing out, however, the cake heights are not leveled off. Fractal dimension of cake patches boundary falls in the range of 1–1.4 and depends on vertical position as well as time of filtration. Cake height measurements with Polyimide (PI) needle felts were hampered on account of its photosensitive nature. PMID:24415801

Diaphragm opening effects on shock wave formation and acceleration in a rectangular cross section channel

NASA Astrophysics Data System (ADS)

Pakdaman, S. A.; Garcia, M.; Teh, E.; Lincoln, D.; Trivedi, M.; Alves, M.; Johansen, C.

2016-11-01

Shock wave formation and acceleration in a high-aspect ratio cross section shock tube were studied experimentally and numerically. The relative importance of geometric effects and diaphragm opening time on shock formation are assessed. The diaphragm opening time was controlled through the use of slit-type (fast opening time) and petal-type (slow opening time) diaphragms. A novel method of fabricating the petal-type diaphragms, which results in a consistent burst pressure and symmetric opening without fragmentation, is presented. High-speed schlieren photography was used to visualize the unsteady propagation of the lead shock wave and trailing gas dynamic structures. Surface-mounted pressure sensors were used to capture the spatial and temporal development of the pressure field. Unsteady Reynolds-Averaged Navier-Stokes simulation predictions using the shear-stress-transport turbulence model are compared to the experimental data. Simulation results are used to explain the presence of high-frequency pressure oscillations observed experimentally in the driver section as well as the cause of the initial acceleration and subsequent rapid decay of shock velocity measured along the top and bottom channel surfaces. A one-dimensional theoretical model predicting the effect of the finite opening time of the diaphragm on the rate of driver depressurization and shock acceleration is proposed. The model removes the large amount of empiricism that accompanies existing models published in the literature. Model accuracy is assessed through comparisons with experiments and simulations. Limitations of and potential improvements in the model are discussed.

Laboratory experiments simulating poroelastic stress changes associated with depletion and injection in low-porosity sedimentary rocks

NASA Astrophysics Data System (ADS)

Ma, Xiaodong; Zoback, Mark D.

2017-04-01

We characterized the poroelastic deformation of six cores from three formations associated with the Bakken play in the Williston Basin (the Lodgepole, Middle Bakken, and Three Forks formations). All are low-porosity, low-permeability formations, but vary considerably in clay, kerogen, and carbonate content. The experimental program simulated reservoir stress changes associated with depletion and injection via cycling both the confining pressure (Pc) and pore pressure (Pp). We measured volumetric strain, derived the corresponding bulk modulus, and calculated the Biot coefficient (α). We found α, which generally ranges between 0.3 and 0.9, to vary systematically with Pc and Pp for each of the specimens tested. The effect of pore pressure on α is much larger at low simple effective stress (σ = Pc-Pp) during depletion than injection. The α decreases with σ for all pore pressures. For the same Pc and Pp, the Biot coefficient is consistently higher during injection than during depletion. Given the observed variations of α with Pc and Pp, the modeling of reservoir stress changes using a constant α could be problematic as poroelastic stress changes during depletion and injection are not likely to follow the same path. Scanning electron microscope examination of microstructures suggests that the variations of the bulk modulus and the Biot coefficient can be attributed to the abundance of compliant components (pores, microcracks, clays, and organic matter) and how they are distributed throughout the rock matrix.

Mechanisms of rubbing-related corneal trauma in keratoconus.

PubMed

McMonnies, Charles W

2009-07-01

Corneal scarring in keratoconus, which is observed prior to contact lens wear and in association with a chronic habit of abnormal rubbing, suggests a keratocyte change to a repair phenotype in response to rubbing trauma. This review examines known and putative mechanisms for rubbing-related corneal trauma and cone formation. Responses to eye rubbing (and possible causal links) may include increased corneal temperature, epithelial thinning, increased concentrations of inflammatory mediators in the precorneal tears, abnormal enzyme activity, large intraocular pressure spikes, high hydrostatic tissue pressure, thixotropically reduced ground substance viscosity, temporary displacement of ground substance from the corneal apex, buckling and flexure of fibrils associated with waves of corneal indentation, biomechanically coupled curvature transfer to the cone apex, slippage between collagen fibrils at the cone apex, and changes to keratocytes due to mechanical trauma and/or high hydrostatic pressure, in addition to scar formation. Cone formation appears to depend on a loss of shear strength and may be a consequence of a reduction in ground substance viscosity and glue function, which could allow the cornea to bend and yield to intraocular pressure. For some forms of keratoconus, a reduction in shear strength and cone-forming deformation may be responses to rubbing trauma. Some of the mechanisms for corneal rubbing trauma may be relevant to post-laser-assisted in situ keratomileusis ectasia or complications following other types of corneal surgery. There appear to be indications for the control of chronic habits of abnormal rubbing.

Evolution of Multiple Double Layer in Glow discharge and its inherent Properties

NASA Astrophysics Data System (ADS)

Alex, Prince; A, Saravanan; Sinha, Suraj

2016-10-01

Formation and evolution of multiple anodic double layers (MADLs) were experimentally studied in glow discharge plasma. The boundary condition for the existence of MADL was identified in terms of threshold bias and ambient working pressure. The MADL formation is accompanied by an explosive growth in anode current and consequent current-voltage characteristics follows a hysteresis loop. The analysis yield that stable MADLs is only observed when the control voltage V2 is between a certain critical values (Vq > νte MADL completely transforms to an intense high current carrying unstable anode glow. The floating potential analysis carried out using three axially positioned electrostatic probes shows a bipolar signature of DL with as the control parameter is varied. The floating potential analysis also shows that hysteresis arises due to the difference in magnitude of electric field required to align the space charges in the DL sheet at the control voltage changes forward and backward. The effect of pressure on MADL indicates that the MADL structure advances towards anode surface as the pressure is increases. The power dumped (W) in the MADL is estimated to decrease with increase in pressure while the same increase in the anode glow.

Pressure enhanced penetration with shaped charge perforators

DOEpatents

Glenn, Lewis A.

2001-01-01

A downhole tool, adapted to retain a shaped charge surrounded by a superatmospherically pressurized light gas, is employed in a method for perforating a casing and penetrating reservoir rock around a wellbore. Penetration of a shaped charge jet can be enhanced by at least 40% by imploding a liner in the high pressure, light gas atmosphere. The gas pressure helps confine the jet on the axis of penetration in the latter stages of formation. The light gas, such as helium or hydrogen, is employed to keep the gas density low enough so as not to inhibit liner collapse.

A high-pressure premixed flat-flame burner for chemical process studies. [of pollutant formation in hydrocarbon flames

NASA Technical Reports Server (NTRS)

Miller, I. M.

1978-01-01

A premixed flat-flame burner was designed and tested with methane-air mixtures at pressures from 1.1 to 20 atm and equivalence ratios from 0.7 to 1.1. Reactant velocity in the burner mixing chamber was used to characterize the range of stable flames at each pressure-equivalence-ratio condition. Color photographs of the flames were used to determine flame zone thickness and flame height. The results show that this burner can be used for chemical process studies in premixed high pressure methane-air flames up to 20 atm.

RAPID FORMATION OF SATURN AFTER JUPITER COMPLETION

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

Kobayashi, Hiroshi; Ormel, Chris W.; Ida, Shigeru, E-mail: hkobayas@nagoya-u.jp, E-mail: ormel@astro.berkeley.edu, E-mail: ida@geo.titech.ac.jp

We have investigated Saturn's core formation at a radial pressure maximum in a protoplanetary disk, which is created by gap opening by Jupiter. A core formed via planetesimal accretion induces the fragmentation of surrounding planetesimals, which generally inhibits further growth of the core by removal of the resulting fragments due to radial drift caused by gas drag. However, the emergence of the pressure maximum halts the drift of the fragments, while their orbital eccentricities and inclinations are efficiently damped by gas drag. As a result, the core of Saturn rapidly grows via accretion of the fragments near the pressure maximum.more » We have found that in the minimum-mass solar nebula, kilometer-sized planetesimals can produce a core exceeding 10 Earth masses within two million years. Since Jupiter may not have undergone significant type II inward migration, it is likely that Jupiter's formation was completed when the local disk mass has already decayed to a value comparable to or less than Jovian mass. The expected rapid growth of Saturn's core on a timescale comparable to or shorter than the observationally inferred disk lifetime enables Saturn to acquire the current amount of envelope gas before the disk gas is completely depleted. The high heat energy release rate onto the core surface due to the rapid accretion of the fragments delays onset of runaway gas accretion until the core mass becomes somewhat larger than that of Jupiter, which is consistent with the estimate based on interior modeling. Therefore, the rapid formation of Saturn induced by gap opening of Jupiter can account for the formation of multiple gas giants (Jupiter and Saturn) without significant inward migration and larger core mass of Saturn than that of Jupiter.« less

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.

THE OZONE REACTION WITH BUTADIENE: FORMATION OF TOXIC PRODUCTS. (R826236)

EPA Science Inventory

Abstract

The formation yields of acrolein, 1,2-epoxy-3-butene and OH radicals have been measured from reaction of ozone with 1,3-butadiene at room temperature and atmosphere pressure. 1,3,5-Trimethyl benzene was added to scavenge OH radicals in measurements of product ...

THE EFFECTS OF EQUIVALENCE RATIO ON THE FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND SOOT IN PREMIXED ETHANE FLAMES. (R825412)

EPA Science Inventory

Abstract

The formation of polycyclic aromatic hydrocarbons (PAH) and soot has been investigated in atmospheric-pressure, laminar, ethane/oxygen/argon premixed flames as a function of mixture equivalence ratio. Mole fraction profiles of major products, trace aromatics, ...

Method for selectively orienting induced fractures in subterranean earth formations

DOEpatents

Shuck, Lowell Z.

1977-02-01

The orientation of hydraulically-induced fractures in relatively deep subterranean earth formations is normally confined to vertical projections along a plane parallel to the maximum naturally occurring (tectonic) compressive stress field. It was found that this plane of maximum compressive stress may be negated and, in effect, re-oriented in a plane projecting generally orthogonal to the original tectonic stress plane by injecting liquid at a sufficiently high pressure into a wellbore fracture oriented in a plane parallel to the plane of tectonic stress for the purpose of stressing the surrounding earth formation in a plane generally orthogonal to the plane of tectonic stress. With the plane of maximum compressive stress re-oriented due to the presence of the induced compressive stress, liquid under pressure is injected into a second wellbore disposed within the zone influenced by the induced compressive stress but at a location in the earth formation laterally spaced from the fracture in the first wellbore for effecting a fracture in the second wellbore along a plane generally orthogonal to the fracture in the first wellbore.

Dependence of negative ion formation on inhomogeneous electric field strength in atmospheric pressure negative corona discharge

NASA Astrophysics Data System (ADS)

Sekimoto, K.; Takayama, M.

2008-12-01

The dependence of negative ion formation on the inhomogeneous electric field strength in atmospheric pressure negative corona discharge with point-to-plane electrodes has been described. The distribution of negative ions HO-, NOx - and COx - and their abundances on the plane electrode was obtained with a mass spectrometer. The ion distribution on the plane was divided into two regions, the center region on the needle axis and peripheral region occurring the dominant NOx - and COx - ions and HO- ion, respectively. The calculated electric field strength in inhomogeneous electric field established on the needle tip surface suggested that the abundant formation of NOx - and COx - ions and HO- ion is attributed to the high field strength at the tip apex region over 108 Vm-1 and the low field strength at the tip peripheral region of the order of 107 Vm-1, respectively. The formation of HO-, NOx - and COx - has been discussed from the standpoint of negative ion evolution based on the thermochemical reaction and the kinetic energy of electron emitted from the needle tip.

Renal tissue damage induced by focused shock waves

NASA Astrophysics Data System (ADS)

Ioritani, N.; Kuwahara, M.; Kambe, K.; Taguchi, K.; Saitoh, T.; Shirai, S.; Orikasa, S.; Takayama, K.; Lush, P. A.

1990-07-01

Biological evidence of renal arterial wall damage induced by the microjet due to shock wave-cavitation bubble interaction was demonstrated in living dog kidneys. We also intended to clarify the mechanism of renal tissue damage and the effects of different conditions of shock wave exposure (peak pressure of focused area, number of shots, exposure rate) on the renal tissue damage in comparison to stone disintegration. Disruption of arterial wall was the most remarkable histological change in the focused area of the kidneys. This lesion appeared as if the wall had been punctured by a needle. Large hematoma formation in the renal parenchym, and interstitial hemorrhage seemed to be the results of the arterial lesion. This arterial disorder also led to ischemic necrosis of the tubules surrounding the hematoma. Micro-angiographic examination of extracted kidneys also proved such arterial puncture lesions and ischemic lesions. The number of shots required for model stone disintegration was not inversely proportional to peak pressure. It decreased markedly when peak pressure was above 700 bar. Similarly thenumber of shots for hematoma formation was not inversely proportional to peak pressure, however, this decreased markedly above 500 bar. These results suggested that a hematoma could be formed under a lower peak pressure than that required for stone disintegration.

Functional properties and in vitro trypsin digestibility of red kidney bean (Phaseolus vulgaris L.) protein isolate: Effect of high-pressure treatment.

PubMed

Yin, Shou-Wei; Tang, Chuan-He; Wen, Qi-Biao; Yang, Xiao-Quan; Li, Lin

2008-10-15

The effects of high-pressure (HP) treatment at 200-600MPa, prior to freeze-drying, on some functional properties and in vitro trypsin digestibility of vicilin-rich red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) were investigated. Surface hydrophobicity and free sulfhydryl (SH) and disulfide bond (SS) contents were also evaluated. HP treatment resulted in gradual unfolding of protein structure, as evidenced by gradual increases in fluorescence strength and SS formation from SH groups, and decrease in denaturation enthalpy change. The protein solubility of KPI was significantly improved at pressures of 400MPa or higher, possibly due to formation of soluble aggregate from insoluble precipitate. HP treatment at 200 and 400MPa significantly increased emulsifying activity index (EAI) and emulsion stability index (ESI); however, EAI was significantly decreased at 600MPa (relative to untreated KPI). The thermal stability of the vicilin component was not affected by HP treatment. Additionally, in vitro trypsin digestibility of KPI was decreased only at a pressure above 200MPa and for long incubation time (e.g., 120min). The data suggest that some physiochemical and functional properties of vicilin-rich kidney proteins can be improved by means of high-pressure treatment. Copyright © 2008 Elsevier Ltd. All rights reserved.

Rowan Gorilla I rigged up, heads for eastern Canada

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

Not Available

1984-03-01

Designed to operate in very hostile offshore environments, the first of the Rowan Gorilla class of self-elevating drilling rigs has been towed to its drilling assignment offshore Nova Scotia. About 40% larger than other jackups, these rigs can operate in 300 ft of water, drilling holes as deep as 30,000 ft. They also feature unique high-pressure and solids control systems that are expected to improve drilling procedures and efficiencies. A quantitative formation pressure evaluation program for the Hewlett-Packard HP-41 handheld calculator computes formation pressures by three independent methods - the corrected d exponent, Bourgoyne and Young, and normalized penetration ratemore » techniques for abnormal pressure detection and computation. Based on empirically derived drilling rate equations, each of the methods can be calculated separately, without being dependent on or influenced by the results or stored data from the other two subprograms. The quantitative interpretation procedure involves establishing a normal drilling rate trend and calculating the pore pressure from the magnitude of the drilling rate trend or plotting parameter increases above the trend line. Mobil's quick, accurate program could aid drilling operators in selecting the casing point, minimizing differential sticking, maintaining the proper mud weights to avoid kicks and lost circulation, and maximizing penetration rates.« less

Shock-activated reaction synthesis and high pressure response of titanium-based ternary carbide and nitride ceramics

NASA Astrophysics Data System (ADS)

Jordan, Jennifer Lynn

The objectives of this study were to (a) investigate the effect of shock activation of precursor powders for solid-state reaction synthesis of Ti-based ternary ceramics and (b) to determine the high pressure phase stability and Hugoniot properties of Ti3SiC2. Dynamically densified compacts of Ti, SiC, and graphite precursor powders and Ti and AlN precursor powders were used to study the shock-activated formation of Ti 3SiC2 and Ti2AlN ternary compounds, respectively, which are considered to be novel ceramics having high stiffness but low hardness. Gas gun and explosive loading techniques were used to obtain a range of loading conditions resulting in densification and activation. Measurements of fraction reacted as a function of time and temperature and activation energies obtained from DTA experiments were used to determine the degree of activation caused by shock compression and its subsequent effect on the reaction mechanisms and kinetics. In both systems, shock activation led to an accelerated rate of reaction at temperatures less than 1600°C and, above that temperature, it promoted the formation of almost 100% of the ternary compound. A kinetics-based mathematical model based on mass and thermal transport was developed to predict the effect of shock activation and reaction synthesis conditions that ensure formation of the ternary compounds. Model predictions revealed a transition temperature above which the reaction is taken over by the "run-away" combustion-type mode. The high pressure phase stability of pre-alloyed Ti 3SiC2 compound was investigated by performing Hugoniot shock and particle velocity measurements using the facilities at the National Institute for Materials Science (Tsukuba, Japan). Experiments performed at pressures of 95--120 GPa showed that the compressibility of Ti3SiC 2 at these pressures deviates from the previously reported compressibility of the material under static high pressure loading. The deviation in compressibility behavior is indicative of the transformation of the Ti3 SiC2 ceramic to a high pressure, high density phase.

Effects of Sweep Angle on the Boundary-Layer Stability Characteristics of an Untapered Wing at Low Speeds

NASA Technical Reports Server (NTRS)

Boltz, Frederick W.; Kenyon, George C.; Allen, Clyde Q.

1960-01-01

An investigation was conducted in the Ames 12-Foot Low-Turbulence Pressure Tunnel to determine the effects of sweep on the boundary-layer stability characteristics of an untapered variable-sweep wing having an NACA 64(2)A015 section normal to the leading edge. Pressure distribution and transition were measured on the wing at low speeds at sweep angles of 0, 10, 20, 30, 40, and 50 deg. and at angles of attack from -3 to 3 deg. The investigation also included flow-visualization studies on the surface at sweep angles from 0 to 50 deg. and total pressure surveys in the boundary layer at a sweep angle of 30 deg. for angles of attack from -12 to 0 deg. It was found that sweep caused premature transition on the wing under certain conditions. This effect resulted from the formation of vortices in the boundary layer when a critical combination of sweep angle, pressure gradient, and stream Reynolds number was attained. A useful parameter in indicating the combined effect of these flow variables on vortex formation and on beginning transition is the crossflow Reynolds number. The critical values of crossflow Reynolds number for vortex formation found in this investigation range from about 135 to 190 and are in good agreement with those reported in previous investigations. The values of crossflow Reynolds number for beginning transitions were found to be between 190 and 260. For each condition (i.e., development of vortices and initiation of transition at a given location) the lower values in the specified ranges were obtained with a light coating of flow-visualization material on the surface. A method is presented for the rapid computation of crossflow Reynolds number on any swept surface for which the pressure distribution is known. From calculations based on this method, it was found that the maximum values of crossflow Reynolds number are attained under conditions of a strong pressure gradient and at a sweep angle of about 50 deg. Due to the primary dependence on pressure gradient, effects of sweep in causing premature transition are generally first encountered on the lower surfaces of wings operating at positive angles of attack.

Fault reactivation and seismicity risk from CO2 sequestration in the Chinshui gas field, NW Taiwan

NASA Astrophysics Data System (ADS)

Sung, Chia-Yu; Hung, Jih-Hao

2015-04-01

The Chinshui gas field located in the fold-thrust belt of western Taiwan was a depleted reservoir. Recently, CO2 sequestration has been planned at shallower depths of this structure. CO2 injection into reservoir will generate high fluid pressure and trigger slip on reservoir-bounding faults. We present detailed in-situ stresses from deep wells in the Chinshui gas field and evaluated the risk of fault reactivation for underground CO2 injection. The magnitudes of vertical stress (Sv), formation pore pressure (Pf) and minimum horizontal stress (Shmin) were obtained from formation density logs, repeat formation tests, sonic logs, mud weight, and hydraulic fracturing including leak-off tests and hydraulic fracturing. The magnitude of maximum horizontal stress (SHmax) was constrained by frictional limit of critically stressed faults. Results show that vertical stress gradient is about 23.02 MPa/km (1.02 psi/ft), and minimum horizontal stress gradient is 18.05 MPa/km (0.80 psi/ft). Formation pore pressures were hydrostatic at depths 2 km, and increase with a gradient of 16.62 MPa/km (0.73 psi/ft). The ratio of fluid pressure and overburden pressure (λp) is 0.65. The upper bound of maximum horizontal stress constrained by strike-slip fault stress regime (SHmax>Sv>Shmin) and coefficient of friction (μ=0.6) is about 18.55 MPa/km (0.82 psi/ft). The orientation of maximum horizontal stresses was calculated from four-arm caliper tools through the methodology suggested by World Stress Map (WMS). The mean azimuth of preferred orientation of borehole breakouts are in ~65。N. Consequently, the maximum horizontal stress axis trends in 155。N and sub-parallel to the far-field plate-convergence direction. Geomechanical analyses of the reactivation of pre-existing faults was assessed using 3DStress and Traptester software. Under current in-situ stress, the middle block fault has higher slip tendency, but still less than frictional coefficient of 0.6 a common threshold value for motion on incohesive faults. The results also indicate that CO2 injection in the Chinshui gas field will not compromise the stability of faults.

High pressure flame system for pollution studies with results for methane-air diffusion flames

NASA Technical Reports Server (NTRS)

Miller, I. M.; Maahs, H. G.

1977-01-01

A high pressure flame system was designed and constructed for studying nitrogen oxide formation in fuel air combustion. Its advantages and limitations were demonstrated by tests with a confined laminar methane air diffusion flame over the pressure range from 1 to 50 atm. The methane issued from a 3.06 mm diameter port concentrically into a stream of air contained within a 20.5 mm diameter chimney. As the combustion pressure is increased, the flame changes in shape from wide and convex to slender and concave, and there is a marked increase in the amount of luminous carbon. The height of the flame changes only moderately with pressure.

Downhole steam generator using low-pressure fuel and air supply

DOEpatents

Fox, R.L.

1981-01-07

For tertiary oil recovery, an apparatus for downhole steam generation is designed in which water is not injected directly onto the flame in the combustor, the combustion process is isolated from the reservoir pressure, the fuel and oxidant are supplied to the combustor at relatively low pressures, and the hot exhaust gases is prevented from entering the earth formation but is used to preheat the fuel and oxidant and water. The combustion process is isolated from the steam generation process. (DLC)

A Demands-Resources Model of Work Pressure in IT Student Task Groups

ERIC Educational Resources Information Center

Wilson, E. Vance; Sheetz, Steven D.

2010-01-01

This paper presents an initial test of the group task demands-resources (GTD-R) model of group task performance among IT students. We theorize that demands and resources in group work influence formation of perceived group work pressure (GWP) and that heightened levels of GWP inhibit group task performance. A prior study identified 11 factors…

JPRS Report - Science & Technology Japan: New Functional Materials.

DTIC Science & Technology

1989-12-27

Using Modified and Controlled High Pressure Environments [Masao Wakatsuki, Kaoru J. Takano] 21 Molecular Design, Synthesis, and Evaluation of High...Crystals [ Shigetoshi Takahashi ] 51 Synthesis of New Organosilicon Polymers and Their Functionalities [Mitsuo Ishikawa , Joji Ohshita] 52...Analysis of The Formation Mechanisms Using Modified and Controlled High Pressure Environments Masao Wakatsuki and Kaoru J. Takano Institute of

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

McNesby, Kevin L.; Homan, Barrie E.; Benjamin, Richard A.

Here, the techniques presented in this paper allow for mapping of temperature, pressure, chemical species, and energy deposition during and following detonations of explosives, using high speed cameras as the main diagnostic tool. Additionally, this work provides measurement in the explosive near to far-field (0-500 charge diameters) of surface temperatures, peak air-shock pressures, some chemical species signatures, shock energy deposition, and air shock formation.

Thermodynamic Models for Aqueous Alteration Coupled with Volume and Pressure Changes in Asteroids

NASA Technical Reports Server (NTRS)

Mironenko, M. V.; Zolotov, M. Y.

2005-01-01

All major classes of chondrites show signs of alteration on their parent bodies (asteroids). The prevalence of oxidation and hydration in alteration pathways implies that water was the major reactant. Sublimation and melting of water ice, generation of gases, formation of aqueous solutions, alteration of primary minerals and glasses and formation of secondary solids in interior parts of asteroids was likely to be driven by heat from the radioactive decay of short-lived radionuclides. Progress of alteration reactions should have affected masses and volumes of solids, and aqueous and gas phases. In turn, pressure evolution should have been controlled by changes in volumes and temperatures, escape processes, and production/ consumption of gases.

Redifferentiation of chondrocytes and cartilage formation under intermittent hydrostatic pressure.

PubMed

Heyland, Jan; Wiegandt, Katharina; Goepfert, Christiane; Nagel-Heyer, Stefanie; Ilinich, Eduard; Schumacher, Udo; Pörtner, Ralf

2006-10-01

Since articular cartilage is subjected to varying loads in vivo and undergoes cyclic hydrostatic pressure during periods of loading, it is hypothesized that mimicking these in vivo conditions can enhance synthesis of important matrix components during cultivation in vitro. Thus, the influence of intermittent loading during redifferentiation of chondrocytes in alginate beads, and during cartilage formation was investigated. A statistically significant increased synthesis of glycosaminoglycan and collagen type II during redifferentiation of chondrocytes embedded in alginate beads, as well as an increase in glycosaminoglycan content of tissue-engineered cartilage, was found compared to control without load. Immunohistological staining indicated qualitatively a high expression of collagen type II for both cases.

Investigation of soot and carbon formation in small gas turbine combustors

NASA Technical Reports Server (NTRS)

Rosfjord, T. J.

1982-01-01

An investigation of hardware configurations which attempt to minimize carbon and soot-production without sacrificing performance in small gas turbine combustors was conducted. Four fuel injectors, employing either airblast atomization, pressure atomization, or fuel vaporization techniques were combined with nozzle air swirlers and injector sheaths. Eight configurations were screened at sea-level takeoff and idle test conditions. Selected configurations were focused upon in an attempt to quantify the influence of combustor pressure, inlet temperature, primary zone operation, and combustor loading on soot and carbon formation. Cycle tests were also performed. It was found that smoke emission levels depended on the combustor fluid mechanics, the atomization quality of the injector and the fuel hydrogen content.

Potential of select intermediate-volatility organic compounds and consumer products for secondary organic aerosol and ozone formation under relevant urban conditions

NASA Astrophysics Data System (ADS)

Li, Weihua; Li, Lijie; Chen, Chia-li; Kacarab, Mary; Peng, Weihan; Price, Derek; Xu, Jin; Cocker, David R.

2018-04-01

Emissions of certain low vapor pressure-volatile organic compounds (LVP-VOCs) are considered exempt to volatile organic compounds (VOC) regulations due to their low evaporation rates. However, these compounds may still play a role in ambient secondary organic aerosol (SOA) and ozone formation. The LVP-VOCs selected for this work are categorized as intermediate-volatility organic compounds (IVOCs) according to their vapor pressures and molecular formulas. In this study, the evaporation rates of 14 select IVOCs are investigated with half of them losing more than 95% of their mass in less than one month. Further, SOA and ozone formation are presented from 11 select IVOCs and 5 IVOC-containing generic consumer products under atmospherically relevant conditions using varying radical sources (NOx and/or H2O2) and a surrogate reactive organic gas (ROG) mixture. Benzyl alcohol (0.41), n-heptadecane (0.38), and diethylene glycol monobutyl ether (0.16) are determined to have SOA yields greater than 0.1 in the presence of NOx and a surrogate urban hydrocarbon mixture. IVOCs also influence ozone formation from the surrogate urban mixture by impacting radical levels and NOx availability. The addition of lab created generic consumer products has a weak influence on ozone formation from the surrogate mixture but strongly affects SOA formation. The overall SOA and ozone formation of the generic consumer products could not be explained solely by the results of the pure IVOC experiments.

Zinc-blende to rocksalt transition in SiC in a laser-heated diamond-anvil cell

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

Daviau, Kierstin; Lee, Kanani K. M.

2017-04-18

We explore the stability of the ambient pressure zinc-blende polymorph (B3) structure of silicon carbide (SiC) at high pressures and temperatures where it transforms to the rocksalt (B1) structure. We find that the transition occurs ~40 GPa lower than previously measured when heated to moderately high temperatures. A lower transition pressure is consistent with the transition pressures predicted in numerous ab initio computations. We find a large volume decrease across the transition of ~17%, with the volume drop increasing at higher formation pressures, suggesting this transition is volume driven yielding a nearly pressure-independent Clapeyron slope. Such a dramatic density increasemore » occurring at pressure is important to consider in applications where SiC is exposed to extreme conditions, such as in industrial applications or planetary interiors.« less

Evidence of a Nonphotochemical Mechanism for the Solid-State Formation of Uranyl Peroxide.

PubMed

Kirkegaard, Marie C; Miskowiec, Andrew; Ambrogio, Michael W; Anderson, Brian B

2018-05-21

We have demonstrated the solid-state formation of a uranyl peroxide (UP) species from hydrated uranyl fluoride via a uranyl hydroxide intermediate, the first observation of a UP species formed in a solid-state reaction. Water vapor pressure is shown to be a driving factor of both the loss of fluorine and the subsequent formation of peroxo units. We have ruled out a photochemical mechanism for formation of the UP species by demonstrating that the same reaction occurs in the dark. A radiolytic mechanism is unlikely because of the low radioactivity of the sample material, suggesting the existence of a novel UP formation mechanism.

Soot Formation in Freely-Propagating Laminar Premixed Flames

NASA Technical Reports Server (NTRS)

Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

1997-01-01

Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

Cyclic hydrostatic pressure stimulates enhanced bone development in the foetal chick femur in vitro.

PubMed

Henstock, J R; Rotherham, M; Rose, J B; El Haj, A J

2013-04-01

Mechanical loading of bone and cartilage in vivo results in the generation of cyclic hydrostatic forces as bone compression is transduced to fluid pressure in the canalicular network and the joint synovium. It has therefore been suggested that hydrostatic pressure is an important stimulus by which osteochondral cells and their progenitors sense and respond to mechanical loading in vivo. In this study, hydrostatic pressure regimes of 0-279kPa at 0.005-2Hz were applied to organotypically cultured ex vivo chick foetal femurs (e11) for 1hour per day in a custom designed bioreactor for 14days and bone formation assessed by X-ray microtomography and qualified by histology. We found that the mineralised portion of the developing femur cultured under any cyclic hydrostatic pressure regime was significantly larger and/or denser than unstimulated controls but that constant (non-cycling) hydrostatic pressure had no effect on bone growth. Further experiments showed that the increase in bone formation was directly proportional to stimulation frequency (R(2)=0.917), but independent of the magnitude of the pressure applied, whilst even very low frequencies of stimulation (0.005Hz) had significant effects on bone growth. Expression of Type-II collagen in both epiphyses and diaphysis was significantly upregulated (1.48-fold and 1.95-fold respectively), together with osteogenic genes (osteonectin and osteopontin) and the osteocyte maturation marker CD44. This work demonstrates that cyclic hydrostatic pressure promotes bone growth and mineralisation in a developmental model and supports the hypothesis that hydrostatic forces play an important role in regulating bone growth and remodelling in vivo. Copyright © 2013 Elsevier Inc. All rights reserved.

The use of pneumatically generated water pressure signals for aquifer characterization

NASA Astrophysics Data System (ADS)

Fort, M.; Roberts, R.; Chace, D.

2013-12-01

The use of pneumatically generated pressure signals for aquifer characterization Hydraulic tests are the most reliable method of obtaining estimates of hydrologic properties, such as conductivity, that are essential for flow and transport modeling. The use of a sinusoidal signal for hydraulic testing is well established, with Streltsova (1988), Rasmussen (2003) and others having developed analytic solutions. Sinusoidal tests provide a unique easily distinguished signal that reduces ambiguity during analysis and we show that a sinusoidal pressure signal propagates farther into the formation than a standard slug-test signal. If a sinusoidal test is combined with a slug and/or a constant rate test, it can further reduce uncertainty in the estimated parameter values. We demonstrate how pneumatic pressure can be used to generate all three of these signals. By positioning pressure transducers both below the water level and in the head space above the water, we can monitor the total pressure acting on the formation and the changes in water level. From the changes in water level, it is possible to calculate the flow rate in and out of the well, assuming that the well diameter and water density are known. Using gas flow controllers with a Supervisory Control And Data Acquisition (SCADA) system we are able to precisely control the pressures in the well. The use of pneumatic pressure has the advantage that it requires less equipment (no pumps) and produces no water. We also show how the numerical well test analysis program nSIGHTS can be used to analyze all three types of tests simultaneously and to assess the relative contribution of each type of test to the parameter estimation. nSIGHTS was recently released as open source by Sandia National Laboratories and is available for free.

Hydraulic pressure inducing renal tubular epithelial-myofibroblast transdifferentiation in vitro.

PubMed

Li, Fei-yan; Xie, Xi-sheng; Fan, Jun-ming; Li, Zi; Wu, Jiang; Zheng, Rong

2009-09-01

The effects of hydraulic pressure on renal tubular epithelial-myofibroblast transdifferentiation (TEMT) were investigated. We applied hydraulic pressure (50 cm H2O) to normal rat kidney tubular epithelial cells (NRK52E) for different durations. Furthermore, different pressure magnitudes were applied to cells. The morphology, cytoskeleton, and expression of myofibroblastic marker protein and transforming growth factor-beta1 (TGF-beta1) of NRK52E cells were examined. Disorganized actin filaments and formation of curling clusters in actin were seen in the cytoplasm of pressurized cells. We verified that de novo expression of alpha-smooth muscle actin induced by pressure, which indicated TEMT, was dependent on both the magnitude and duration of pressure. TGF-beta1 expression was significantly upregulated under certain conditions, which implies that the induction of TEMT by hydraulic pressure is related with TGF-beta1. We illustrate for the first time that hydraulic pressure can induce TEMT in a pressure magnitude- and duration-dependent manner, and that this TEMT is accompanied by TGF-beta1 secretion.

Detecting Pore Fluid Pressure Changes by Using the Vp/Vs Ratio

NASA Astrophysics Data System (ADS)

Vanorio, T.; Mavko, G.

2006-12-01

A central problem in studies aimed at predicting the dynamic behavior of faults is monitoring and quantifying fluid changes in areas prone to overpressure. Experimental and modeling studies show the Vp/Vs ratio to be a good determinant of the saturation state of a rock formation as well as of its inner pore pressure condition. Dectecting pore pressure changes depends, among other causes, on the reliability of laboratory data to calibrate the in-situ measured velocities. Ideally, laboratory experiments performed under controlled conditions would identify the fundamental mechanisms responsible for changes in the measured acoustic properties. However, technical limitations in the laboratory together with the assumptions driving the experimental and modeling approaches rise spouriuos mechanisms which hinder our present understanding of the actual role of high pore pressure on the elastic and poroelastic parameters. Critical issues unclude: a) the frequencies used in the laboratory are responsible for high-frequency fluid effects which induce velocity dispersion. As a result, both the effective stress parameter and velocities (and their pressure-dependence) estimated from high- frequency ultrasonic data are different from those applicable to crustal low frequency wave propagation; b) laboratory measurements made at dry, drained conditions are assumed to mimic those in gas pressured rocks. However, in dry, drained conditions, no pore pressure is exerted in the pore space, and the pore gas is infinitely compressible; c) when using room-dry, drained measurements as the baseline to model pressured rock formations, the unloading path (i.e. decreasing confining pressure) is supposed to mimic the inflationary path due to pore pressure increase. Doing so, it is assumed that the amount of crack opening due to pore pressure is equal to that of crack closure caused by the overburden stress and thus, the effective stress coefficient is implicitely assumed equal to 1. To minimize the assumptions and limitations described above, we designed a laboratory experiment which used gas as pore fluid medium. Experimental results show that in gas-pressured saturated rocks the Vp/Vs ratio, while remaining lower than values reported for liquid saturation conditions, increases with decreasing differential pressure, similarly to the trend observed in liquid saturated rocks.

Visible/near-infrared spectra of experimentally shocked plagioclase feldspars

USGS Publications Warehouse

Johnson, J. R.; Horz, F.

2003-01-01

High shock pressures cause structural changes in plagioclase feldspars such as mechanical fracturing and disaggregation of the crystal lattice at submicron scales, the formation of diaplectic glass (maskelynite), and genuine melting. Past studies of visible/ near-infrared spectra of shocked feldspars demonstrated few spectral variations with pressure except for a decrease in the depth of the absorption feature near 1250-1300 nm and an overall decrease in reflectance. New visible/near-infrared spectra (400-2500 nm) of experimentally shocked (17-56 GPa) albite- and anorthite-rich rock powders demonstrate similar trends, including the loss of minor hydrated mineral bands near 1410, 1930, 2250, and 2350 nm. However, the most interesting new observations are increases in reflectance at intermediate pressures, followed by subsequent decreases in reflectance at higher pressures. The amount of internal scattering and overall sample reflectance is controlled by the relative proportions of micro-fractures, submicron grains, diaplectic glass, and melts formed during shock metamorphism. We interpret the observed reflectance increases at intermediate pressures to result from progressively larger proportions of submicron feldspar grains and diaplectic glass. The ensuing decreases in reflectance occur after diaplectic glass formation is complete and the proportion of genuine melt inclusions increases. The pressure regimes over which these reflectance variations occur differ between albite and anorthite, consistent with thermal infrared spectra of these samples and previous studies of shocked feldspars. These types of spectral variations associated with different peak shock pressures should be considered during interpretation and modeling of visible/near-infrared remotely sensed spectra of planetary and asteroidal surfaces.

Metal/Silicate Partitioning at High Pressures and Temperatures

NASA Technical Reports Server (NTRS)

Shofner, G.; Campbell, A.; Danielson, L.; Righter, K.; Rahman, Z.

2010-01-01

The behavior of siderophile elements during metal-silicate segregation, and their resulting distributions provide insight into core formation processes. Determination of partition coefficients allows the calculation of element distributions that can be compared to established values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Moderately siderophile elements, including W, are particularly useful in constraining core formation conditions because they are sensitive to variations in T, P, oxygen fugacity (fO2), and silicate composition. To constrain the effect of pressure on W metal/silicate partitioning, we performed experiments at high pressures and temperatures using a multi anvil press (MAP) at NASA Johnson Space Center and laser-heated diamond anvil cells (LHDAC) at the University of Maryland. Starting materials consisted of natural peridotite mixed with Fe and W metals. Pressure conditions in the MAP experiments ranged from 10 to 16 GPa at 2400 K. Pressures in the LHDAC experiments ranged from 26 to 58 GPa, and peak temperatures ranged up to 5000 K. LHDAC experimental run products were sectioned by focused ion beam (FIB) at NASA JSC. Run products were analyzed by electron microprobe using wavelength dispersive spectroscopy. Liquid metal/liquid silicate partition coefficients for W were calculated from element abundances determined by microprobe analyses, and corrected to a common fO2 condition of IW-2 assuming +4 valence for W. Within analytical uncertainties, W partitioning shows a flat trend with increasing pressure from 10 to 16 GPa. At higher pressures, W becomes more siderophile, with an increase in partition coefficient of approximately 0.5 log units.

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel.

PubMed

Yang, Zixuan; Kan, Bo; Li, Jinxu; Qiao, Lijie; Volinsky, Alex A; Su, Yanjing

2017-11-14

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance.

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel

PubMed Central

Yang, Zixuan; Kan, Bo; Li, Jinxu; Su, Yanjing; Qiao, Lijie; Volinsky, Alex A.

2017-01-01

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance. PMID:29135912

Hydrogen gas storage in fluorinated ultramicroporous tunnel crystal

NASA Astrophysics Data System (ADS)

Kataoka, Keisuke; Katagiri, Toshimasa

2012-07-01

We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder.We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder. Electronic supplementary information (ESI) available. CCDC 246922. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30940h

HIGH PRESSURE COAL COMBUSTON KINETICS PROJECT

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

Stefano Orsino

As part of the U.S. Department of Energy (DoE) initiative to improve the efficiency of coal-fired power plants and reduce the pollution generated by these facilities, DOE has funded the High-Pressure Coal Combustion Kinetics (HPCCK) Projects. A series of laboratory experiments were conducted on selected pulverized coals at elevated pressures with the specific goals to provide new data for pressurized coal combustion that will help extend to high pressure and validate models for burnout, pollutant formation, and generate samples of solid combustion products for analyses to fill crucial gaps in knowledge of char morphology and fly ash formation. Two seriesmore » of high-pressure coal combustion experiments were performed using SRI's pressurized radiant coal flow reactor. The first series of tests characterized the near burner flame zone (NBFZ). Three coals were tested, two high volatile bituminous (Pittsburgh No.8 and Illinois No.6), and one sub-bituminous (Powder River Basin), at pressures of 1, 2, and 3 MPa (10, 20, and 30 atm). The second series of experiments, which covered high-pressure burnout (HPBO) conditions, utilized a range of substantially longer combustion residence times to produce char burnout levels from 50% to 100%. The same three coals were tested at 1, 2, and 3 MPa, as well as at 0.2 MPa. Tests were also conducted on Pittsburgh No.8 coal in CO2 entrainment gas at 0.2, 1, and 2 MPa to begin establishing a database of experiments relevant to carbon sequestration techniques. The HPBO test series included use of an impactor-type particle sampler to measure the particle size distribution of fly ash produced under complete burnout conditions. The collected data have been interpreted with the help of CFD and detailed kinetics simulation to extend and validate devolatilization, char combustion and pollutant model at elevated pressure. A global NOX production sub-model has been proposed. The submodel reproduces the performance of the detailed chemical reaction mechanism for the NBFZ tests.« less

Thermally-driven Coupled THM Processes in Shales

NASA Astrophysics Data System (ADS)

Rutqvist, J.

2017-12-01

Temperature changes can trigger strongly coupled thermal-hydrological-mechanical (THM) processes in shales that are important to a number of subsurface energy applications, including geologic nuclear waste disposal and hydrocarbon extraction. These coupled processes include (1) direct pore-volume couplings, by thermal expansion of trapped pore-fluid that triggers instantaneous two-way couplings between pore fluid pressure and mechanical deformation, and (2) indirect couplings in terms of property changes, such as changes in mechanical stiffness, strength, and permeability. Direct pore-volume couplings have been studied in situ during borehole heating experiments in shale (or clay stone) formations at Mont Terri and Bure underground research laboratories in Switzerland and France. Typically, the temperature changes are accompanied with a rapid increase in pore pressure followed by a slower decrease towards initial (pre-heating) pore pressure. Coupled THM modeling of these heater tests shows that the pore pressure increases because the thermal expansion coefficient of the fluid is much higher than that of the porous clay stone. Such thermal pressurization induces fluid flow away from the pressurized area towards areas of lower pressure. The rate of pressure increase and magnitude of peak pressure depends on the rate of heating, pore-compressibility, and permeability of the shale. Modeling as well as laboratory experiments have shown that if the pore pressure increase is sufficiently large it could lead to fracturing of the shale or shear slip along pre-existing bedding planes. Another set of data and observations have been collected associated with studies related to concentrated heating and cooling of oil-shales and shale-gas formations. Heating may be used to enhance production from tight oil-shale, whereas thermal stimulation has been attempted for enhanced shale-gas extraction. Laboratory experiments on shale have shown that strength and elastic deformation modulus decreases with temperature while the rate creep deformations increase with temperature. Such temperature dependency also affects the well stability and zonal sealing across shale layers.

Gas Hydrate Formation Probability Distributions: The Effect of Shear and Comparisons with Nucleation Theory.

PubMed

May, Eric F; Lim, Vincent W; Metaxas, Peter J; Du, Jianwei; Stanwix, Paul L; Rowland, Darren; Johns, Michael L; Haandrikman, Gert; Crosby, Daniel; Aman, Zachary M

2018-03-13

Gas hydrate formation is a stochastic phenomenon of considerable significance for any risk-based approach to flow assurance in the oil and gas industry. In principle, well-established results from nucleation theory offer the prospect of predictive models for hydrate formation probability in industrial production systems. In practice, however, heuristics are relied on when estimating formation risk for a given flowline subcooling or when quantifying kinetic hydrate inhibitor (KHI) performance. Here, we present statistically significant measurements of formation probability distributions for natural gas hydrate systems under shear, which are quantitatively compared with theoretical predictions. Distributions with over 100 points were generated using low-mass, Peltier-cooled pressure cells, cycled in temperature between 40 and -5 °C at up to 2 K·min -1 and analyzed with robust algorithms that automatically identify hydrate formation and initial growth rates from dynamic pressure data. The application of shear had a significant influence on the measured distributions: at 700 rpm mass-transfer limitations were minimal, as demonstrated by the kinetic growth rates observed. The formation probability distributions measured at this shear rate had mean subcoolings consistent with theoretical predictions and steel-hydrate-water contact angles of 14-26°. However, the experimental distributions were substantially wider than predicted, suggesting that phenomena acting on macroscopic length scales are responsible for much of the observed stochastic formation. Performance tests of a KHI provided new insights into how such chemicals can reduce the risk of hydrate blockage in flowlines. Our data demonstrate that the KHI not only reduces the probability of formation (by both shifting and sharpening the distribution) but also reduces hydrate growth rates by a factor of 2.

Oxidation of SiC/BN/SiC Composites in Reduced Oxygen Partial Pressures

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Boyd, Meredith

2010-01-01

SiC fiber-reinforced SiC composites with a BN interphase are proposed for use as leading edge structures of hypersonic vehicles. The durability of these materials under hypersonic flight conditions is therefore of interest. Thermogravimetric analysis was used to characterize the oxidation kinetics of both the constituent fibers and composite coupons at four temperatures: 816, 1149, 1343, and 1538 C (1500, 2100, 2450, and 2800 F) and in oxygen partial pressures between 5% and 0.1% (balance argon) at 1 atm total pressure. One edge of the coupons was ground off so the effects of oxygen ingress into the composite could be monitored by post-test SEM and EDS. Additional characterization of the oxidation products was conducted by XPS and TOF-SIMS. Under most conditions, the BN oxidized rapidly, leading to the formation of borosilicate glass. Rapid initial oxidation followed by volatilization of boria lead to protective oxide formation and further oxidation was slow. At 1538C in 5% oxygen, both the fibers and coupons exhibited borosilicate glass formation and bubbling. At 1538C in 0.1% oxygen, active oxidation of both the fibers and the composites was observed leading to rapid SiC degradation. BN oxidation at 1538C in 0.1% oxygen was not significant.

Constraints on Grain Formation Around Carbon Stars from Laboratory Studies of Presolar Graphite

NASA Technical Reports Server (NTRS)

Bernatowicz, T. J.; Akande, O. W.; Croat, T. K.; Cowsik, R.

2005-01-01

We report the results of an investigation into the physical conditions in the mass outflows of asymptotic giant branch (AGB) carbon stars that are required for the formation of micron-sized presolar graphite grains, either with or without internal crystals of titanium carbide (TiC). In addition to providing detailed information about stellar nucleosynthesis, the structure and composition of presolar grains give unique information about the conditions of grain formation. In the present work we use laboratory observations of presolar graphite to gain insight into the physical conditions in circumstellar outflows from carbon AGB stars. The periodic pulsation of AGB stars enhances the gas density through shocks in the stellar atmosphere above the photosphere, promoting the condensation of dust grains. Copious mass outflow occurs largely because grains are coupled to the radiation field of the star, which accelerates them by radiation pressure; momentum is in turn transferred to gas molecules by collisions with grains. The dust/gas mixture is effectively a two-component fluid whose motion depends on atmospheric structure and which, in turn, influences that structure. In particular, the radiation pressure on the grains determines the velocity field of the outflow and thus the density distribution, while the density distribution itself determines the conditions of radiative transfer within the outflow and thus the effective radiation pressure.

A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury.

PubMed

Ziraldo, Cordelia; Solovyev, Alexey; Allegretti, Ana; Krishnan, Shilpa; Henzel, M Kristi; Sowa, Gwendolyn A; Brienza, David; An, Gary; Mi, Qi; Vodovotz, Yoram

2015-06-01

People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to "better" vs. "worse" outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU.

A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury

PubMed Central

Ziraldo, Cordelia; Solovyev, Alexey; Allegretti, Ana; Krishnan, Shilpa; Henzel, M. Kristi; Sowa, Gwendolyn A.; Brienza, David; An, Gary; Mi, Qi; Vodovotz, Yoram

2015-01-01

People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to “better” vs. “worse” outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU. PMID:26111346

Geopressure modeling from petrophysical data: An example from East Kalimantan

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

Herkommer, M.A.

1994-07-01

Localized models of abnormal formation pressure (geopressure) are important economic and safety tools frequently used for well planning and drilling operations. Simplified computer-based procedures have been developed that permit these models to be developed more rapidly and with greater accuracy. These techniques are broadly applicable to basins throughout the world where abnormal formation pressures occur. An example from the Attaka field of East Kalimantan, southeast Asia, shows how geopressure models are developed. Using petrophysical and engineering data, empirical correlations between observed pressure and petrophysical logs can be created by computer-assisted data-fitting techniques. These correlations serve as the basis for modelsmore » of the geopressure. By performing repeated analyses on wells at various locations, contour maps on the top of abnormal geopressure can be created. Methods that are simple in their development and application make the task of geopressure estimation less formidable to the geologist and petroleum engineer. Further, more accurate estimates can significantly improve drilling speeds while reducing the incidence of stuck pipe, kicks, and blowouts. In general, geopressure estimates are used in all phases of drilling operations: To develop mud plans and specify equipment ratings, to assist in the recognition of geopressured formations and determination of mud weights, and to improve predictions at offset locations and geologically comparable areas.« less

A molecular beam mass spectrometric study of the formation and photolysis of C(lc)lO dimer

NASA Technical Reports Server (NTRS)

Greene, Frank T.; Robaugh, David A.

1992-01-01

A study of the chlorine oxides present at temperatures and pressures typical of the Antarctic stratosphere was carried out. A series of low temperature flow reactors was constructed and used in conjunction with molecular beam mass spectrometric techniques to identify species and characterize their kinetic behavior at temperatures of -20 to -70 C and pressures of from 30 to 130 Torr. It was found that the gas phase chlorine-oxygen system was quite complex at low temperatures. ClO dimer was identified and found to be thermodynamically very stable under stratospheric conditions. It was also found that any system which contained ClO also contained a larger oxide. The oxide was identified as Cl2O3. A survey of possible higher oxides, which have been postulated as possible chlorine sinks in the stratosphere, was also carried out. The rate of formation of ClO dimer was measured as a function of temperature and pressure. Measurements were made of both the decay of ClO and the formation of the dimer. By comparing these rates it was determined that virtually all of the ClO was converted to the dimer under stratospheric conditions, and that the other ClO reactions were not important under these conditions.

On the Experimental and Theoretical Investigations of Lean Partially Premixed Combustion, Burning Speed, Flame Instability and Plasma Formation of Alternative Fuels at High Temperatures and Pressures

NASA Astrophysics Data System (ADS)

Askari, Omid

This dissertation investigates the combustion and injection fundamental characteristics of different alternative fuels both experimentally and theoretically. The subjects such as lean partially premixed combustion of methane/hydrogen/air/diluent, methane high pressure direct-injection, thermal plasma formation, thermodynamic properties of hydrocarbon/air mixtures at high temperatures, laminar flames and flame morphology of synthetic gas (syngas) and Gas-to-Liquid (GTL) fuels were extensively studied in this work. These subjects will be summarized in three following paragraphs. The fundamentals of spray and partially premixed combustion characteristics of directly injected methane in a constant volume combustion chamber have been experimentally studied. The injected fuel jet generates turbulence in the vessel and forms a turbulent heterogeneous fuel-air mixture in the vessel, similar to that in a Compressed Natural Gas (CNG) Direct-Injection (DI) engines. The effect of different characteristics parameters such as spark delay time, stratification ratio, turbulence intensity, fuel injection pressure, chamber pressure, chamber temperature, Exhaust Gas recirculation (EGR) addition, hydrogen addition and equivalence ratio on flame propagation and emission concentrations were analyzed. As a part of this work and for the purpose of control and calibration of high pressure injector, spray development and characteristics including spray tip penetration, spray cone angle and overall equivalence ratio were evaluated under a wide range of fuel injection pressures of 30 to 90 atm and different chamber pressures of 1 to 5 atm. Thermodynamic properties of hydrocarbon/air plasma mixtures at ultra-high temperatures must be precisely calculated due to important influence on the flame kernel formation and propagation in combusting flows and spark discharge applications. A new algorithm based on the statistical thermodynamics was developed to calculate the ultra-high temperature plasma composition and thermodynamic properties. The method was applied to compute the thermodynamic properties of hydrogen/air and methane/air plasma mixtures for a wide range of temperatures (1,000-100,000 K), pressures (10-6-100 atm) and different equivalence ratios within flammability limit. In calculating the individual thermodynamic properties of the atomic species, the Debye-Huckel cutoff criterion has been used for terminating the series expression of the electronic partition function. A new differential-based multi-shell model was developed in conjunction with Schlieren photography to measure laminar burning speed and to study the flame instabilities for different alternative fuels such as syngas and GTL. Flame instabilities such as cracking and wrinkling were observed during flame propagation and discussed in terms of the hydrodynamic and thermo-diffusive effects. Laminar burning speeds were measured using pressure rise data during flame propagation and power law correlations were developed over a wide range of temperatures, pressures and equivalence ratios. As a part of this work, the effect of EGR addition and substitution of nitrogen with helium in air on flame morphology and laminar burning speed were extensively investigated. The effect of cell formation on flame surface area of syngas fuel in terms of a newly defined parameter called cellularity factor was also evaluated. In addition to that the experimental onset of auto-ignition and theoretical ignition delay times of premixed GTL/air mixture were determined at high pressures and low temperatures over a wide range of equivalence ratios.

Using comics to increase literacy and assess student learning

NASA Astrophysics Data System (ADS)

Schwaller, Terry

2013-02-01

Formative assessment strategies and the integration of literacy pose two of the many hurdles teachers face. With the pressure of standardized test scores hanging over everyone's heads, finding class time to integrate these essential strategies is at a premium. By integrating comics with quick, formative written assessment, you can kill the proverbial two birds with one stone.

THE GAS PHASE REACTION OF OZONE WITH 1,3-BUTADIENE: FORMATION YIELDS OF SOME TOXIC PRODUCTS. (R826236)

EPA Science Inventory

The formation yields of acrolein, 1,2-epoxy-3-butene and OH radicals have been measured from reaction of ozone with 1,3-butadiene at room temperature and atmosphere pressure. 1,3,5-Trimethyl benzene was added to scavenge OH radicals in measurements of product yields. In separa...

Numerical simulation of water and sand blowouts when penetrating through shallow water flow formations in deep water drilling

NASA Astrophysics Data System (ADS)

Ren, Shaoran; Liu, Yanmin; Gong, Zhiwu; Yuan, Yujie; Yu, Lu; Wang, Yanyong; Xu, Yan; Deng, Junyu

2018-02-01

In this study, we applied a two-phase flow model to simulate water and sand blowout processes when penetrating shallow water flow (SWF) formations during deepwater drilling. We define `sand' as a pseudo-component with high density and viscosity, which can begin to flow with water when a critical pressure difference is attained. We calculated the water and sand blowout rates and analyzed the influencing factors from them, including overpressure of the SWF formation, as well as its zone size, porosity and permeability, and drilling speed (penetration rate). The obtained data can be used for the quantitative assessment of the potential severity of SWF hazards. The results indicate that overpressure of the SWF formation and its zone size have significant effects on SWF blowout. A 10% increase in the SWF formation overpressure can result in a more than 90% increase in the cumulative water blowout and a 150% increase in the sand blowout when a typical SWF sediment is drilled. Along with the conventional methods of well flow and pressure control, chemical plugging, and the application of multi-layer casing, water and sand blowouts can be effectively reduced by increasing the penetration rate. As such, increasing the penetration rate can be a useful measure for controlling SWF hazards during deepwater drilling.

Experimental and numerical investigations of resonant acoustic waves in near-critical carbon dioxide.

PubMed

Hasan, Nusair; Farouk, Bakhtier

2015-10-01

Flow and transport induced by resonant acoustic waves in a near-critical fluid filled cylindrical enclosure is investigated both experimentally and numerically. Supercritical carbon dioxide (near the critical or the pseudo-critical states) in a confined resonator is subjected to acoustic field created by an electro-mechanical acoustic transducer and the induced pressure waves are measured by a fast response pressure field microphone. The frequency of the acoustic transducer is chosen such that the lowest acoustic mode propagates along the enclosure. For numerical simulations, a real-fluid computational fluid dynamics model representing the thermo-physical and transport properties of the supercritical fluid is considered. The simulated acoustic field in the resonator is compared with measurements. The formation of acoustic streaming structures in the highly compressible medium is revealed by time-averaging the numerical solutions over a given period. Due to diverging thermo-physical properties of supercritical fluid near the critical point, large scale oscillations are generated even for small sound field intensity. The strength of the acoustic wave field is found to be in direct relation with the thermodynamic state of the fluid. The effects of near-critical property variations and the operating pressure on the formation process of the streaming structures are also investigated. Irregular streaming patterns with significantly higher streaming velocities are observed for near-pseudo-critical states at operating pressures close to the critical pressure. However, these structures quickly re-orient to the typical Rayleigh streaming patterns with the increase operating pressure.

Inhibition of coronary blood flow by a vascular waterfall mechanism.

PubMed

Downey, J M; Kirk, E S

1975-06-01

The mechanism whereby systole inhibits coronary blood flow was examined. A branch of the left coronary artery was maximally dilated with an adenosine infusion, and the pressure-flow relationship was obtained for beating and arrested states. The pressure-flow curve for the arrested state was shifted toward higher pressures and in the range of pressures above peak ventricular pressure was linear and parallel to that for the arrested state. Below this range the curve for the beating state converged toward that for the arrested state and was convex to the pressure axis. These results were compared with a model of the coronary vasculature that consisted of numerous parallel channels, each responding to local intramyocardial pressure by forming vascular waterfalls. When intramyocardial pressure in the model was assigned values from zero at the epicardium to peak ventricular pressure at the endocardium, pressure-flow curves similar to the experimental ones resulted. Thus, we conclude that systole inhibits coronary perfusion by the formation of vascular waterfalls and that the intramyocardial pressures responsible for this inhibition do not significantly exceed peak ventricular pressure.

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

Malhotra, Vivak

The USA is embarking upon tackling the serious environmental challenges posed to the world by greenhouse gases, especially carbon dioxide (CO2). The dimension of the problem is daunting. In fact, according to the Energy Information Agency, nearly 6 billion metric tons of CO2 were produced in the USA in 2007 with coal-burning power plants contributing about 2 billion metric tons. To mitigate the concerns associated with CO2 emission, geological sequestration holds promise. Among the potential geological storage sites, unmineable coal seams and shale formations in particular show promise because of the probability of methane recovery while sequestering the CO2. However.more » the success of large-scale sequestration of CO2 in coal and shale would hinge on a thorough understanding of CO2's interactions with host reservoirs. An important parameter for successful storage of CO2 reservoirs would be whether the pressurized CO2 would remain invariant in coal and shale formations under reasonable internal and/or external perturbations. Recent research has brought to the fore the potential of induced seismicity, which may result in caprock compromise. Therefore, to evaluate the potential risks involved in sequestering CO2 in Illinois bituminous coal seams and shale, we studied: (i) the mechanical behavior of Murphysboro (Illinois) and Houchin Creek (Illinois) coals, (ii) thermodynamic behavior of Illinois bituminous coal at - 100oC ≤ T ≤ 300oC, (iii) how high pressure CO2 (up to 20.7 MPa) modifies the viscosity of the host, (iv) the rate of emission of CO2 from Illinois bituminous coal and shale cores if the cores, which were pressurized with high pressure (≤ 20.7 MPa) CO2, were exposed to an atmospheric pressure, simulating the development of leakage pathways, (v) whether there are any fractions of CO2 stored in these hosts which are resistance to emission by simply exposing the cores to atmospheric pressure, and (vi) how compressive shockwaves applied to the coal and shale cores, which were pressurized with high pressure CO2, determine the fate of sequestered CO2 in these cores. Our results suggested that Illinois bituminous coal in its unperturbed state, i.e., when not pressurized with CO2, showed large variations in the mechanical properties. Modulus varied from 0.7 GPa to 3.4 GPa even though samples were extracted from a single large chunk of coal. We did not observe any glass transition for Illinois bituminous coal at - 100oC ≤ T ≤ 300oC, however, when the coal was pressurized with CO2 at ambient ≤ P ≤ 20.7 MPa, the viscosity of the coal decreased and inversely scaled with the CO2 pressure. The decrease in viscosity as a function of pressure could pose CO2 injection problems for coal as lower viscosity would allow the solid coal to flow to plug the fractures, fissures, and cleats. Our experiments also showed a very small fraction of CO2 was absorbed in coal; and when CO2 pressurized coals were exposed to atmospheric conditions, the loss of CO2 from coals was massive. Half of the sequestered gas from the coal cores was lost in less than 20 minutes. Our shockwave experiments on Illinois bituminous coal, New Albany shale (Illinois), Devonian shale (Ohio), and Utica shale (Ohio) presented clear evidence that the significant emission of the sequestered CO2 from these formations cannot be discounted during seismic activity, especially if caprock is compromised. It is argued that additional shockwave studies, both compressive and transverse, would be required for successfully mapping the risks associated with sequestering high pressure CO2 in coal and shale formations.« less

Nonlinear Fluid Migration Patterns in Fractured Reservoirs due to Stress-Pressure Coupling induced Changes in Reservoir Permeabilities

NASA Astrophysics Data System (ADS)

Annewandter, R.; Geiger, S.; Main, I. G.

2011-12-01

Sustainable storage of carbon dioxide (CO2) requires a thorough understanding of injection induced pressure build-up and its effects on the storage formation's integrity, since it determines the cap rock's sealing properties as well as the total storable amount of carbon dioxide. Fractures are abundant in the subsurface and difficult to detect due to their subseismic characteristic. If present in the cap during injection, they can be primary pathways for CO2 leakage. The North Sea is considered as Europe's most important carbon dioxide storage area. However, almost all of the potential storage formations have been exposed to post-glacial lithospheric flexure, possibly causing the generation of new fracture networks in the overburden whilst rebounding. Drawing upon, fast carbon dioxide uprise can be facilitated due to opening of fractures caused by changes in the stress field over time. The overall effective permeability, and hence possible leakage rates, of a fractured storage formation is highly sensitive to the fracture aperture which itself depends on the far field and in situ stress field. For this reason, our in-house general purpose reservoir simulator Complex System Modeling Platform (CSMP++) has been expanded, which is particularly designed to simulate multiphase flow on fractured porous media. It combines finite element (FE) and finite volume (FV) methods on mixed-dimensional hybrid-element meshes. The unstructured FE-FV based scheme allows us to model complex geological structures, such as fractures, at great detail. The simulator uses a compositional model for NaCl-H2O-CO2-systems for compressible fluids for computing thermophysical properties as a function of formation pressure and temperature. A fixed stress-split sequential procedure is being used to calculate coupled fluid flow and geomechanics. Numerical proof of concept studies will be presented showing the impact of fracture opening and closure on fluid migration patterns due to coupled stress-pressure induced changes in effective permeabilities.

Ambient pressure process for preparing aerogel thin films reliquified sols useful in preparing aerogel thin films

DOEpatents

Brinker, Charles Jeffrey; Prakash, Sai Sivasankaran

1999-01-01

A method for preparing aerogel thin films by an ambient-pressure, continuous process. The method of this invention obviates the use of an autoclave and is amenable to the formation of thin films by operations such as dip coating. The method is less energy intensive and less dangerous than conventional supercritical aerogel processing techniques.

Teaching the Pressure-Flow Hypothesis of Phloem Transport in a Problem-Solving Session

ERIC Educational Resources Information Center

Clifford, Paul

2004-01-01

Problem solving is an ideal learning strategy, especially for topics that are perceived as difficult to teach. As an example, a format is described for a problem-solving session designed to help students understand the pressure-flow hypothesis of phloem transport in plants. Five key facts and their discussion can lead to the conclusion that a…

Decarboxylase inhibition and blood pressure reduction by alpha-methyl-3,4-dihydroxy-DL-phenylalanine.

PubMed

OATES, J A; GILLESPIE, L; UDENFRIEND, S; SJOERDSMA, A

1960-06-24

alpha-Methyl-3,4-dihydroxy-DLphenylalanine has been found to be an effective inhibitor of aromatic amino acid decarboxylation in man. This was shown by decreased formation of serotonin, tryptamine, and tyramine from the precursor amino acids. Reduction of amine biosynthesis is associated with lowering of blood pressure in hypertensive patients and a transient sedative effect.

Focusing on the Nature of Causality in a Unit on Pressure: How Does It Affect Student Understanding?

ERIC Educational Resources Information Center

Basca, Belinda B.; Grotzer, Tina A.

Although pressure forms the basis for understanding topics such as the internal structure of the earth, weather cycles, rock formation, Bernoulli's principle, and plate tectonics, the presence of this concept in the school curriculum is at a minimal level. This paper suggests that the ideas, misconceptions, and perceptions of students have to do…

Preliminary investigation of the performance of a single tubular combustor at pressure up to 12 atmospheres

NASA Technical Reports Server (NTRS)

Wear, Jerrold D; Butze, Helmut F

1954-01-01

The effects of combustor operation at conditions representative of those encountered in high pressure-ratio turbojet engines or at high flight speeds on carbon deposition, exhaust smoke, and combustion efficiency were studied in a single tubular combustor. Carbon deposition and smoke formation tests were conducted over a range of combustor-inlet pressures from 33 to 173 pounds per square inch absolute and combustor reference velocities from 78 to 143 feet per second. Combustion efficiency tests were conducted over a range of pressures from 58 to 117 pounds per square inch absolute and velocities from 89 to 172 feet per second.

Method and apparatus for producing thermal vapor stream

DOEpatents

Cradeur, Robert R.; Sperry, John S.; Krajicek, Richard W.

1979-01-01

Method and apparatus for producing a thermal vapor stream for injecting into a subterranean formation for the recovery of liquefiable minerals therefrom, including a pressure vessel containing a high pressure combustion chamber for producing a heating gas for introduction into a heating gas injector. The heating gas injector is partly immersed in a steam generating section of the pressure vessel such that the heating gas is passed through the steam generating section to produce steam and combustion products which are directed between the pressure vessel and the combustion chamber for simultaneously cooling of the combustion chamber by further heating of the steam and combustion gases.

Voltage and partial pressure dependent defect chemistry in (La,Sr)FeO3–δ thin films investigated by chemical capacitance measurements

PubMed Central

Rupp, Ghislain M.; Fleig, Jürgen

2018-01-01

La0.6Sr0.4FeO3–δ (LSF) thin films of different thickness were prepared by pulsed laser deposition on yttria stabilized zirconia (YSZ) and characterized by using three electrode impedance spectroscopy. Electrochemical film capacitance was analyzed in relation to oxygen partial pressure (0.25 mbar to 1 bar), DC polarization (0 m to –600 m) and temperature (500 to 650 °C). For most measurement parameters, the chemical bulk capacitance dominates the overall capacitive properties and the corresponding defect chemical state depends solely on the oxygen chemical potential inside the film, independent of atmospheric oxygen pressure and DC polarization. Thus, defect chemical properties (defect concentrations and defect formation enthalpies) could be deduced from such measurements. Comparison with LSF defect chemical bulk data from the literature showed good agreement for vacancy formation energies but suggested larger electronic defect concentrations in the films. From thickness-dependent measurements at lower oxygen chemical potentials, an additional capacitive contribution could be identified and attributed to the LSF|YSZ interface. Deviations from simple chemical capacitance models at high pressures are most probably due to defect interactions. PMID:29671421

Voltage and partial pressure dependent defect chemistry in (La,Sr)FeO3-δ thin films investigated by chemical capacitance measurements.

PubMed

Schmid, Alexander; Rupp, Ghislain M; Fleig, Jürgen

2018-05-03

La0.6Sr0.4FeO3-δ (LSF) thin films of different thickness were prepared by pulsed laser deposition on yttria stabilized zirconia (YSZ) and characterized by using three electrode impedance spectroscopy. Electrochemical film capacitance was analyzed in relation to oxygen partial pressure (0.25 mbar to 1 bar), DC polarization (0 m to -600 m) and temperature (500 to 650 °C). For most measurement parameters, the chemical bulk capacitance dominates the overall capacitive properties and the corresponding defect chemical state depends solely on the oxygen chemical potential inside the film, independent of atmospheric oxygen pressure and DC polarization. Thus, defect chemical properties (defect concentrations and defect formation enthalpies) could be deduced from such measurements. Comparison with LSF defect chemical bulk data from the literature showed good agreement for vacancy formation energies but suggested larger electronic defect concentrations in the films. From thickness-dependent measurements at lower oxygen chemical potentials, an additional capacitive contribution could be identified and attributed to the LSF|YSZ interface. Deviations from simple chemical capacitance models at high pressures are most probably due to defect interactions.

Design of experimental system for supercritical CO2 fracturing under confining pressure conditions

NASA Astrophysics Data System (ADS)

Wang, H.; Lu, Q.; Li, X.; Yang, B.; Zheng, Y.; Shi, L.; Shi, X.

2018-03-01

Supercritical CO2 has the characteristics of low viscosity, high diffusion and zero surface tension, and it is considered as a new fluid for non-polluting and non-aqueous fracturing which can be used for shale gas development. Fracturing refers to a method of utilizing the high-pressure fluid to generate fractures in the rock formation so as to improve the oil and gas flow conditions and increase the oil and gas production. In this article, a new type of experimental system for supercritical CO2 fracturing under confining pressure conditions is designed, which is based on characteristics of supercritical CO2, shale reservoir and down-hole environment. The experimental system consists of three sub-systems, including supercritical CO2 generation system, supercritical CO2 fracturing system and data analysis system. It can be used to simulate supercritical CO2 fracturing under geo-stress conditions, thus to study the rock initiation pressure, the formation of the rock fractures, fractured surface morphology and so on. The experimental system has successfully carried out a series of supercritical CO2 fracturing experiments. The experimental results confirm the feasibility of the experimental system and the high efficiency of supercritical CO2 in fracturing tight rocks.

Effect of laser fluence and ambient gas pressure on surface morphology and chemical composition of hydroxyapatite thin films deposited using pulsed laser deposition

NASA Astrophysics Data System (ADS)

Nishikawa, Hiroaki; Hasegawa, Tsukasa; Miyake, Akiko; Tashiro, Yuichiro; Komasa, Satoshi; Hashimoto, Yoshiya

2018-01-01

The dependence of the surface morphology and chemical composition of hydroxyapatite (HA) thin films on the laser fluence and ambient gas pressure during their formation by pulsed laser deposition was studied as the first step to investigate the effect of physical and chemical interactions between the ablated chemical species and ambient gas molecules on HA film formation. It was found that a higher fluence could decrease the number of large protrusions on the surface of HA thin films. However, too high a fluence caused a phosphorus deficiency from the stoichiometric value, particularly in the case of lower ambient gas pressure. It was also found that for lower fluences, the atomic species among the ablated chemical species were easily scattered by collision processes with ambient gas molecules. This was caused by the lower velocity of the ablated chemical species and higher ambient gas pressure, which induced a shorter mean free path. In addition, these collision processes played an important role in the adsorption, migration, and re-evaporation of the ablated chemical species on the substrate via chemical reactions.

Pressure-induced structural transformations of the Zintl phase sodium silicide

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

Cabrera, Raul Quesada; Salamat, Ashkan; Barkalov, Oleg I.

The high-pressure behaviour of NaSi has been studied using Raman spectroscopy and angle-dispersive synchrotron X-ray diffraction to observe the onset of structural phase transformations and potential oligomerisation into anionic Si nanoclusters with extended dimensionality. Our studies reveal a first structural transformation occurring at 8-10 GPa, followed by irreversible amorphisation above 15 GPa, suggesting the formation of Si-Si bonds with oxidation of the Si{sup -} species and reduction of Na{sup +} to metallic sodium. We have combined our experimental studies with DFT calculations to assist in the analysis of the structural behaviour of NaSi at high pressure. - Abstract: The high-pressuremore » behaviour of NaSi has been studied using Raman spectroscopy and angle-dispersive synchrotron X-ray diffraction. Our studies reveal a first structural transformation occurring at 8-10 GPa, followed by irreversible amorphisation, suggesting the formation of Si-Si bonds with oxidation of the Si{sup -} species and reduction of Na{sup +} to metallic sodium. We have combined our experimental studies with DFT calculations to assist in the analysis of the structural behaviour of NaSi at high pressure. Display Omitted« less

Ozone kinetics in low-pressure discharges

NASA Astrophysics Data System (ADS)

Guerra, Vasco; Marinov, Daniil; Guaitella, Olivier; Rousseau, Antoine

2012-10-01

Ozone kinetics is quite well established at atmospheric pressure, due to the importance of ozone in atmospheric chemistry and to the development of industrial ozone reactors. However, as the pressure is decreased and the dominant three-body reactions lose importance, the main mechanisms involved in the creation and destruction of ozone are still surrounded by important uncertainties. In this work we develop a self-consistent model for a pulsed discharge and its afterglow operating in a Pyrex reactor with inner radius 1 cm, at pressures in the range 1-5 Torr and discharge currents of 40-120 mA. The model couples the electron Boltzmann equation with a system of equations for the time evolution of the heavy particles. The calculations are compared with time-dependent measurements of ozone and atomic oxygen. Parametric studies are performed in order to clarify the role of vibrationally excited ozone in the overall kinetics and to establish the conditions where ozone production on the surface may become important. It is shown that vibrationally excited ozone does play a significant role, by increasing the time constants of ozone formation. Moreover, an upper limit for the ozone formation at the wall in these conditions is set at 10(-4).

Modeling of Laser Vaporization and Plume Chemistry in a Boron Nitride Nanotube Production Rig

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Fay, Catharine C.

2012-01-01

Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

Cold-gas experiments to study the flow separation characteristics of a dual-bell nozzle during its transition modes

NASA Astrophysics Data System (ADS)

Verma, S. B.; Stark, R.; Nuerenberger-Genin, C.; Haidn, O.

2010-06-01

An experimental investigation has been carried out to study the effect of test environment on transition characteristics and the flow unsteadiness associated with the transition modes of a dual-bell nozzle. Cold-gas tests using gaseous nitrogen were carried out in (i) a horizontal test-rig with nozzle exhausting into atmospheric conditions and, (ii) a high altitude simulation chamber with nozzle operation under self-evacuation mode. Transient tests indicate that increasing δP 0/ δt (the rate of stagnation chamber pressure change) reduces the amplitude of pressure fluctuations of the separation shock at the wall inflection point. This is preferable from the viewpoint of lowering the possible risk of any structural failure during the transition mode. Sea-level tests show 15-17% decrease in the transition nozzle pressure ratio (NPR) during subsequent tests in a single run primarily due to frost formation in the nozzle extension up to the wall inflection location. Frost reduces the wall inflection angle and hence, the transition NPR. However, tests inside the altitude chamber show nearly constant NPR value during subsequent runs primarily due to decrease in back temperature with decrease in back pressure that prevents any frost formation.

Aromatic ring generation as a dust precursor in acetylene discharges

NASA Astrophysics Data System (ADS)

De Bleecker, Kathleen; Bogaerts, Annemie; Goedheer, Wim

2006-04-01

Production of aromatic hydrocarbon compounds as an intermediate step for particle formation in low-pressure acetylene discharges is investigated via a kinetic approach. The detailed chemical reaction mechanism contains 140 reactions among 55 species. The cyclic hydrocarbon chemistry is mainly based on studies of polycyclic aromatic hydrocarbon formation in cosmic environments. The model explicitly includes organic chain, cyclic molecules, radicals, and ions up to a size of 12 carbon atoms. The calculated density profiles show that the aromatic formation yields are quite significant, suggesting that aromatic compounds play a role in the underlying mechanisms of particle formation in hydrocarbon plasmas.

Measurements of electron avalanche formation time in W-band microwave air breakdown

NASA Astrophysics Data System (ADS)

Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

2011-08-01

We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ˜0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

Impact of the hydrogen partial pressure on lactate degradation in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1.

PubMed

Junicke, H; Feldman, H; van Loosdrecht, M C M; Kleerebezem, R

2015-04-01

In this study, the impact of the hydrogen partial pressure on lactate degradation was investigated in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1. To impose a change of the hydrogen partial pressure, formate was added to the reactor. Hydrogen results from the bioconversion of formate besides lactate in the liquid phase. In the presence of a hydrogen-consuming methanogen, this approach allows for a better estimation of low dissolved hydrogen concentrations than under conditions where hydrogen is supplied externally from the gas phase, resulting in a more accurate determination of kinetic parameters. A change of the hydrogen partial pressure from 1,200 to 250 ppm resulted in a threefold increase of the biomass-specific lactate consumption rate. The 50 % inhibition constant of hydrogen on lactate degradation was determined as 0.692 ± 0.064 μM dissolved hydrogen (831 ± 77 ppm hydrogen in the gas phase). Moreover, for the first time, the maximum biomass-specific lactate consumption rate of Desulfovibrio sp. G11 (0.083 ± 0.006 mol-Lac/mol-XG11/h) and the affinity constant for hydrogen uptake of Methanobrevibacter arboriphilus DH1 (0.601 ± 0.022 μM dissolved hydrogen) were determined. Contrary to the widely established view that the biomass-specific growth rate of a methanogenic coculture is determined by the hydrogen-utilizing partner; here, it was found that the hydrogen-producing bacterium determined the biomass-specific growth rate of the coculture grown on lactate and formate.

Lunar floor-fractured craters as magmatic intrusions: Geometry, modes of emplacement, associated tectonic and volcanic features, and implications for gravity anomalies

NASA Astrophysics Data System (ADS)

Jozwiak, Lauren M.; Head, James W.; Wilson, Lionel

2015-03-01

Lunar floor-fractured craters are a class of 170 lunar craters with anomalously shallow, fractured floors. Two end-member processes have been proposed for the floor formation: viscous relaxation, and subcrater magmatic intrusion and sill formation. Recent morphometric analysis with new Lunar Reconnaissance Orbiter Laser Altimeter (LOLA) and image (LROC) data supports an origin related to shallow magmatic intrusion and uplift. We find that the distribution and characteristics of the FFC population correlates strongly with crustal thickness and the predicted frequency distribution of overpressurization values of magmatic dikes. For a typical nearside lunar crustal thickness, dikes with high overpressurization values favor surface effusive eruptions, medium values favor intrusion and sill formation, and low values favor formation of solidified dikes concentrated lower in the crust. We develop a model for this process, make predictions for the morphologic, morphometric, volcanic, and geophysical consequences of the process and then compare these predictions with the population of observed floor-fractured craters. In our model, the process of magmatic intrusion and sill formation begins when a dike propagates vertically towards the surface; as the dike encounters the underdense brecciated region beneath the crater, the magmatic driving pressure is insufficient to continue vertical propagation, but pressure in the stalled dike exceeds the local lithostatic pressure. The dike then begins to propagate laterally forming a sill which does not propagate past the crater floor region because increased overburden pressure from the crater wall and rim crest pinch off the dike at this boundary; the sill then continues to inflate, further raising and fracturing the brittle crater floor. When the intrusion diameter to intrusion depth ratio is smaller than a critical value, the intrusion assumes a laccolith shape with a domed central region. When the ratio exceeds a critical value, the intrusion concentrates bending primarily at the periphery, resulting in a flat, tabular intrusion. We predict that this process will result in concentric fractures over the region of greatest bending. This location is close to the crater wall in large, flat-floored craters, as observed in the crater Humboldt, and interior to the crater over the domed floor in smaller craters, as observed in the crater Vitello. A variety of volcanic features are predicted to be associated with the solidification and degassing of the intrusion; these include: (1) surface lava flows associated with concentric fractures (e.g., in the crater Humboldt); (2) vents with no associated pyroclastic material, from the deflation of under-pressurized magmatic foam (e.g., the crater Damoiseau); and (3) vents with associated pyroclastic deposits from vulcanian eruptions of highly pressurized magmatic foam (e.g., the crater Alphonsus). The intrusion of basaltic magma beneath the crater is predicted to contribute a positive component to the Bouguer gravity anomaly; we assess the predicted Bouguer anomalies associated with FFCs and outline a process for their future interpretation. We conclude that our proposed mechanism serves as a viable formation process for FFCs and accurately predicts numerous morphologic, morphometric, and geophysical features associated with FFCs. These predictions can be further tested using GRAIL (Gravity Recovery and Interior Laboratory) data.

High-pressure microscopy for tracking dynamic properties of molecular machines.

PubMed

Nishiyama, Masayoshi

2017-12-01

High-pressure microscopy is one of the powerful techniques to visualize the effects of hydrostatic pressures on research targets. It could be used for monitoring the pressure-induced changes in the structure and function of molecular machines in vitro and in vivo. This review focuses on the dynamic properties of the assemblies and machines, analyzed by means of high-pressure microscopy measurement. We developed a high-pressure microscope that is optimized both for the best image formation and for the stability to hydrostatic pressure up to 150 MPa. Application of pressure could change polymerization and depolymerization processes of the microtubule cytoskeleton, suggesting a modulation of the intermolecular interaction between tubulin molecules. A novel motility assay demonstrated that high hydrostatic pressure induces counterclockwise (CCW) to clockwise (CW) reversals of the Escherichia coli flagellar motor. The present techniques could be extended to study how molecular machines in complicated systems respond to mechanical stimuli. Copyright © 2017 Elsevier B.V. All rights reserved.

Formation of polycrystalline-silicon films with hemispherical grains for capacitor structures with increased capacitance

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

Novak, A. V., E-mail: novak-andrei@mail.ru

2014-12-15

The effect of formation conditions on the morphology of silicon films with hemispherical grains (HSG-Si) obtained by the method of low-pressure chemical vapor deposition (LPCVD) is investigated by atomic-force microscopy. The formation conditions for HSG-Si films with a large surface area are found. The obtained HSG-Si films make it possible to fabricate capacitor structures, the electric capacitance of which is twice as large in comparison to that of capacitors with “smooth” electrodes from polycrystalline silicon.

Iron-catalyzed hydrogenation of bicarbonates and carbon dioxide to formates.

PubMed

Zhu, Fengxiang; Zhu-Ge, Ling; Yang, Guangfu; Zhou, Shaolin

2015-02-01

The catalytic hydrogenation of carbon dioxide and bicarbonate to formate has been explored extensively. The vast majority of the known active catalyst systems are based on precious metals. Herein, we describe an effective, phosphine-free, air- and moisture-tolerant catalyst system based on Knölker's iron complex for the hydrogenation of bicarbonate and carbon dioxide to formate. The catalyst system can hydrogenate bicarbonate at remarkably low hydrogen pressures (1-5 bar). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effects of shock wave compaction on the transition temperatures of A15 structure superconductors

NASA Technical Reports Server (NTRS)

Otto, G. H.

1974-01-01

Several superconductors with the A15 structure exhibit a positive pressure coefficient, indicating that their transition temperatures increase with applied pressure. Powders of the composition Nb3Al, Nb3Ge, Nb3(Al0.75Ge0.25), and V3Si were compacted by explosive shock waves. The superconducting properties of these materials were measured before and after compaction and it was found that regardless of the sign of the pressure coefficient, the transition temperature is always lowered. The decrease in transition temperature is associated with a decrease in the particle diameter. The shock wave passage through a 3Nb:1Ge powder mixture leads to the formation of at least one compound (probably Nb5Ge3). However, the formation of the A15 compound Nb3Ge is not observed. Elemental niobium powder can be compacted by converging shock waves close to the expected value of the bulk density. Under special circumstances a partial remelting in the center of the sample is observed.

Formation of Nanofoam carbon and re-emergence of Superconductivity in compressed CaC6.

PubMed

Li, Yan-Ling; Luo, Wei; Chen, Xiao-Jia; Zeng, Zhi; Lin, Hai-Qing; Ahuja, Rajeev

2013-11-26

Pressure can tune material's electronic properties and control its quantum state, making some systems present disconnected superconducting region as observed in iron chalcogenides and heavy fermion CeCu2Si2. For CaC6 superconductor (Tc of 11.5 K), applying pressure first Tc increases and then suppresses and the superconductivity of this compound is eventually disappeared at about 18 GPa. Here, we report a theoretical finding of the re-emergence of superconductivity in heavily compressed CaC6. The predicted phase III (space group Pmmn) with formation of carbon nanofoam is found to be stable at wide pressure range with a Tc up to 14.7 K at 78 GPa. Diamond-like carbon structure is adhered to the phase IV (Cmcm) for compressed CaC6 after 126 GPa, which has bad metallic behavior, indicating again departure from superconductivity. Re-emerged superconductivity in compressed CaC6 paves a new way to design new-type superconductor by inserting metal into nanoporous host lattice.

Formation mechanisms and characteristics of transition patterns in oblique detonations

NASA Astrophysics Data System (ADS)

Miao, Shikun; Zhou, Jin; Liu, Shijie; Cai, Xiaodong

2018-01-01

The transition structures of wedge-induced oblique detonation waves (ODWs) in high-enthalpy supersonic combustible mixtures are studied with two-dimensional reactive Euler simulations based on the open-source program AMROC (Adaptive Mesh Refinement in Object-oriented C++). The formation mechanisms of different transition patterns are investigated through theoretical analysis and numerical simulations. Results show that transition patterns of ODWs depend on the pressure ratio Pd/Ps, (Pd, Ps are the pressure behind the ODW and the pressure behind the induced shock, respectively). When Pd/Ps > 1.3, an abrupt transition occurs, while when Pd/Ps < 1.3, a smooth transition appears. A parameter ε is introduced to describe the transition patterns quantitatively. Besides, a criterion based on the velocity ratio Φ=U0/UCJ is proposed to predict the transition patterns based on the inflow conditions. It is concluded that an abrupt transition appears when Φ < 0.98Φ*, while a smooth transition occurs when Φ > 1.02Φ∗ (Φ∗ is the critical velocity ratio calculated with an empirical formula).

The Outsized Influence of a Primordial Lunar Atmosphere

NASA Astrophysics Data System (ADS)

Saxena, Prabal; Elkins-Tanton, Linda T.; Petro, Noah; Mandell, Avi

2016-10-01

Immediately following formation of the moon, its surface was subject to radiative influences from the Lunar Magma Ocean, an early Earth that radiated like a mid type M Dwarf Star, and the early Sun. These contributions have been hypothesized to have produced a vapor pressure atmosphere on the Moon. We model the early atmosphere of the Moon using an atmospheric model originally developed for Io. We also use a magma ocean crystallization model that finds that heating from the early Earth delays crystallization of the Lunar Magma Ocean and contributes to a moderate pressure and collapsing metal-dominated atmosphere on the earthside of the Moon until lid formation. The atmosphere is characterized by maximum pressures ~1 bar and strong horizontal supersonic winds that decreased as the Moon's orbital separation increased. Crustal and other compositional asymmetries may have been influenced by this atmosphere. The atmosphere transported significant amounts of mass horizontally and may have been a source for present day depletions and heterogeneities of moderately volatile elements on the lunar surface.