Preliminary relative permeability estimates of methanehydrate-bearing sand
Seol, Yongkoo; Kneafsey, Timothy J.; Tomutsa, Liviu; Moridis,George J.
2006-05-08
The relative permeability to fluids in hydrate-bearing sediments is an important parameter for predicting natural gas production from gas hydrate reservoirs. We estimated the relative permeability parameters (van Genuchten alpha and m) in a hydrate-bearing sand by means of inverse modeling, which involved matching water saturation predictions with observations from a controlled waterflood experiment. We used x-ray computed tomography (CT) scanning to determine both the porosity and the hydrate and aqueous phase saturation distributions in the samples. X-ray CT images showed that hydrate and aqueous phase saturations are non-uniform, and that water flow focuses in regions of lower hydrate saturation. The relative permeability parameters were estimated at two locations in each sample. Differences between the estimated parameter sets at the two locations were attributed to heterogeneity in the hydrate saturation. Better estimates of the relative permeability parameters require further refinement of the experimental design, and better description of heterogeneity in the numerical inversions.
Two Relations to Estimate Membrane Permeability Using Milestoning.
Votapka, Lane W; Lee, Christopher T; Amaro, Rommie E
2016-08-25
Prediction of passive permeation rates of solutes across lipid bilayers is important to drug design, toxicology, and other biological processes such as signaling. The inhomogeneous solubility-diffusion (ISD) equation is traditionally used to relate the position-dependent potential of mean force and diffusivity to the permeability coefficient. The ISD equation is derived via the Smoluchowski equation and assumes overdamped system dynamics. It has been suggested that the complex membrane environment may exhibit more complicated damping conditions. Here we derive a variant of the inhomogeneous solubility diffusion equation as a function of the mean first passage time (MFPT) and show how milestoning, a method that can estimate kinetic quantities of interest, can be used to estimate the MFPT of membrane crossing and, by extension, the permeability coefficient. We further describe a second scheme, agnostic to the damping condition, to estimate the permeability coefficient from milestoning results or other methods that compute a probability of membrane crossing. The derived relationships are tested using a one-dimensional Langevin dynamics toy system confirming that the presented theoretical methods can be used to estimate permeabilities given simulation and milestoning results. PMID:27154639
Two Relations to Estimate Membrane Permeability Using Milestoning
2016-01-01
Prediction of passive permeation rates of solutes across lipid bilayers is important to drug design, toxicology, and other biological processes such as signaling. The inhomogeneous solubility-diffusion (ISD) equation is traditionally used to relate the position-dependent potential of mean force and diffusivity to the permeability coefficient. The ISD equation is derived via the Smoluchowski equation and assumes overdamped system dynamics. It has been suggested that the complex membrane environment may exhibit more complicated damping conditions. Here we derive a variant of the inhomogeneous solubility diffusion equation as a function of the mean first passage time (MFPT) and show how milestoning, a method that can estimate kinetic quantities of interest, can be used to estimate the MFPT of membrane crossing and, by extension, the permeability coefficient. We further describe a second scheme, agnostic to the damping condition, to estimate the permeability coefficient from milestoning results or other methods that compute a probability of membrane crossing. The derived relationships are tested using a one-dimensional Langevin dynamics toy system confirming that the presented theoretical methods can be used to estimate permeabilities given simulation and milestoning results. PMID:27154639
Simultaneous estimation of relative permeabilities and capillary pressure
Chardaire-Riviere, C.; Bourbiaux, B.J. , 92 - Rueil-Malmaison ); Chavent, G.; Jaffre, J.; Liu, J. )
1992-12-01
In this paper, an automatic numerical method is proposed for simultaneous determination of relative permeabilities and capillary pressure from the results of a single two-phase flow experiment in a range of velocities representative of field flow conditions. The experiment is a standard imbibition or drainage displacement with an imposed difference of pressure or flow rate. The experimental data used are the outlet production, the pressure drop between the two faces, and local saturation profiles at different times along the core. Relative permeabilities and capillary pressure are estimated with a least-square technique. Use of a high-order numerical scheme significantly reduces the numerical diffusion. The optimal control theory is used to solve the minimization problem. The corresponding FORTRAN code is generated by a symbolic program. The validity of the method first is demonstrated with simulated data, then is tested in tow laboratory experiments: one imbibition and one drainage. Good agreement is obtained for both situations.
Estimating three phase relative permeability based on realistic pore scale configurations
NASA Astrophysics Data System (ADS)
Verma, R.; Prodanovic, M.; Wildenschild, D.
2013-12-01
Multiphase (water, oil, gas) flow in porous media is commonly encountered in subsurface. Study of multiphase flows is important in applications such as hydrocarbon recovery, carbon capture and storage, groundwater flow modeling, flow of non-aqueous phase liquids (NAPL), and many others. The problem is notoriously difficult to study, and much effort has gone into understanding the physics of the multiphase flow on the pore scale. In particular, imaging techniques such as x-ray microtomography can now provide 3D microstructure as well as fluid phase configurations at a very high resolution. Using these images, one can validate simulations done by various techniques, such as pore network modeling, the Lattice-Boltzmann method or computational fluid dynamics to name a few. In this work, we present an analysis of several pore-scale images of multiphase flow as well as comparable multiphase flow simulations and show the distribution of various phases in three phase flow situations. We are particularly interested in quantifying spatial configurations, connectivity and relative permeability of the intermediate wetting phase. The rock wettability is one of the key parameters that determines positioning of the phases within the pore space. The wetting phase sticks closer to the wall, while the non-wetting phase is at the center of the pores. In three phase flow, the intermediate wetting phase exists as a layer between the two phases, and this is often the oil phase that we are trying to drain from the system. At the macro scale, this means that the relative permeability is a function of more than one saturation as well as its often complicated spatial configuration. One of the key observations from experiment is high oil relative permeability even at low oil saturations. It is hypothesized that the oil exists as a very thin layer throughout the core sample, and one of the goals of this work is to validate this hypothesis. This layer is rather difficult to observe even with
Oliveira, Leonardo I; Demond, Avery H
2003-11-01
The modeling of transport of organic liquid contaminants through the vadose zone often requires three-phase relative permeabilities. Since these are difficult to measure, predictive models are usually used. The objective of this study is to assess the ability of eight common models to predict the drainage relative permeability to oil in a three-phase system (water-oil-air). A comparison of the models' estimates using data set from Oak [Oak, M.J., 1990. Three-phase relative permeability of water-wet Berea. In: Seventh Symposium on Enhanced Oil Recovery, Paper SPE/Doe 20183. Tulsa, OK, April 22-25] showed that they provide very different predictions for the same system. The goodness of the models does not increase with the amount of data or computation that the models require. Also, the calculations showed how different interpretations of the models and of the terminology associated with them can significantly impact the predictions. Thus, considerable error may be introduced into the simulations of organic liquid transport in the vadose zone depending on the selection and interpretation of the three-phase relative permeability model.
Permeability and relative permeability in rocks
Blair, S.C.; Berryman, J.G.
1990-10-01
Important features of the topology of the pore space of rocks can be usefully quantified by analyzing digitized images of rock cross sections. One approach computes statistical correlation functions using modern image processing techniques. These correlation functions contain information about porosity, specific surface area, tortuosity, formation factor, and elastic constants, as well as the fluid permeability and relative permeability. The physical basis of this approach is discussed and examples of the results for various sandstones are presented. The analysis shows that Kozeny-Carman relations and Archie's empirical laws must be modified to account for finite percolation thresholds in order to avoid unphysical behavior in the calculated relative permeabilities. 33 refs., 4 figs., 1 tab.
Relative permeability through fractures
Diomampo, Gracel, P.
2001-08-01
The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.
NASA Astrophysics Data System (ADS)
Hiratsuka, Y.; Yamamoto, H.
2014-12-01
CCS (Carbon dioxide Capture and Storage) is a promising option for mitigating climate changes. To predict the behavior of injected CO2 in a deep reservoir, relative permeability of supercritical CO2 and water of the reservoir rock is one of the most fundamental and influential properties. For determining the relative permeability, we employed the unsteady state method, in which the relative permeability is determined based on history matching of transient monitoring data with a multi-phase flow model. The unsteady-state method is relatively simple and short, but obviously its accuracy strongly depends on the flow model assumed in the history matching. In this study, we conducted relative permeability measurements of supercritical CO2-water system for Berea sandstone with the unsteady-state method under a reservoir condition at a 1km depth (P= 9.5MPa, T = 44˚C). Automatic history matching was performed with an inversion simulator iTOUGH2/ECO2N for multi-phase flow system of supercritical CO2, NaCl, and water. A sensitivity analysis of relative permeability parameters for CO2 and water was carried out to better understand the uniqueness and the uncertainty of the optimum solution estimated by the history matching. Among the parameters of the Corey-type curve employed in this study, while the end-point permeability could be optimized in a limited range, the other parameters were correlated and their combinations were not unique. However it was found that any combination of these parameters results in nearly identical shapes of the curve in the range of CO2 saturation in this study (0 to 60%). The optimally estimated curve from the unsteady-method was well comparable with those from the steady-state method acquired in the previous studies. Our experiment also focuses on the impact of injection rate on the estimates of relative permeability, as it is known that the injection rate could have a significant effect on fluid distribution such as viscous fingering with
Relative Permeability of Fractured Rock
Mark D. Habana
2002-06-30
Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.
Permeability relation for periodic structures.
Dunn, K J; LaTorraca, G A; Bergman, D J
1998-01-01
The permeability relation for periodic porous media is studied with respect to other petrophysical parameters such as formation factor, porosity, surface-to-volume ratio, and nuclear magnetic resonance (NMR) relaxation time. All these quantities were computed for periodic structures of simple, body-centered, and face-centered cubic arrays of touching and overlapping spheres. The formation factors were calculated by using a method which is based on a Fourier-space representation of an integral equation for the electric potential in a two-component composite. The nuclear magnetic resonance relaxation time for the case where surface-enchanced relaxation plays a dominant role is known to be V P/rho S (VP is the pore volume, S is the pore surface, is the surface relaxation strength) when rho is not too large. Previously calculated permeabilities for these structures from the literature were used for correlation studies with other petrophysical parameters. Various correlation schemes among these quantities, such as k = aTbFc, and k = aTb phi c, were investigated, where k is permeability, T is the NMR relaxation time, phi is the porosity, and F is the formation factor. PMID:9803908
Steam-water relative permeability
Ambusso, W.; Satik, C.; Home, R.N.
1997-12-31
A set of relative permeability relations for simultaneous flow of steam and water in porous media have been measured in steady state experiments conducted under the conditions that eliminate most errors associated with saturation and pressure measurements. These relations show that the relative permeabilities for steam-water flow in porous media vary approximately linearly with saturation. This departure from the nitrogen/water behavior indicates that there are fundamental differences between steam/water and nitrogen/water flows. The saturations in these experiments were measured by using a high resolution X-ray computer tomography (CT) scanner. In addition the pressure gradients were obtained from the measurements of liquid phase pressure over the portions with flat saturation profiles. These two aspects constitute a major improvement in the experimental method compared to those used in the past. Comparison of the saturation profiles measured by the X-ray CT scanner during the experiments shows a good agreement with those predicted by numerical simulations. To obtain results that are applicable to general flow of steam and water in porous media similar experiments will be conducted at higher temperature and with porous rocks of different wetting characteristics and porosity distribution.
Modeling Hysteresis Effect in Three-Phase Relative Permeability
NASA Astrophysics Data System (ADS)
Kianinejad, A.; Chen, X.; DiCarlo, D. A.
2014-12-01
Simulation and fluid flow prediction of many petroleum enhanced oil recovery methods as well as environmental processes such as carbon dioxide (CO2) geological storage requires accurate modeling and determination of relative permeability under different saturation histories. Based on this critical need, there has been several different three-phase relative permeability models developed to predict the hysteresis effects in relative permeability, most of which requiring many different parameters which introduce extreme complexity to the models for practical purposes. In this work, we experimentally measured three-phase, water/oil/gas, relative permeability in a 1-m long water-wet sand pack, under several different flow histories. We measured the in-situ saturations along the sand pack using a CT scanner. We then determined the relative permeabilities directly from the measured in-situ saturations, using unsteady-state method. Based on our results, good estimation of residual saturations yields in excellent three-phase relative permeability estimations by just using the simple, standard relative permeability models such as, Saturation Weighted Interpolation (SWI), Corey's and Stones. Our results show that, the key parameter to model the hysteresis in three-phase relative permeability (effect of saturation history) is the residual saturations. Once the residual saturations were correctly determined for each specific saturation path, the standard relative permeability models can predict the three-phase relative permeabilities perfectly.
SINGLE-INTERVAL GAS PERMEABILITY ESTIMATION
Single-interval, steady-steady-state gas permeability testing requires estimation of pressure at a screened interval which in turn requires measurement of friction factors as a function of mass flow rate. Friction factors can be obtained by injecting air through a length of pipe...
Characterization and estimation of permeability correlation structure from performance data
Ershaghi, I.; Al-Qahtani, M.
1997-08-01
In this study, the influence of permeability structure and correlation length on the system effective permeability and recovery factors of 2-D cross-sectional reservoir models, under waterflood, is investigated. Reservoirs with identical statistical representation of permeability attributes are shown to exhibit different system effective permeability and production characteristics which can be expressed by a mean and variance. The mean and variance are shown to be significantly influenced by the correlation length. Detailed quantification of the influence of horizontal and vertical correlation lengths for different permeability distributions is presented. The effect of capillary pressure, P{sub c1} on the production characteristics and saturation profiles at different correlation lengths is also investigated. It is observed that neglecting P{sub c} causes considerable error at large horizontal and short vertical correlation lengths. The effect of using constant as opposed to variable relative permeability attributes is also investigated at different correlation lengths. Next we studied the influence of correlation anisotropy in 2-D reservoir models. For a reservoir under five-spot waterflood pattern, it is shown that the ratios of breakthrough times and recovery factors of the wells in each direction of correlation are greatly influenced by the degree of anisotropy. In fully developed fields, performance data can aid in the recognition of reservoir anisotropy. Finally, a procedure for estimating the spatial correlation length from performance data is presented. Both the production performance data and the system`s effective permeability are required in estimating the correlation length.
Accurate determination of characteristic relative permeability curves
NASA Astrophysics Data System (ADS)
Krause, Michael H.; Benson, Sally M.
2015-09-01
A recently developed technique to accurately characterize sub-core scale heterogeneity is applied to investigate the factors responsible for flowrate-dependent effective relative permeability curves measured on core samples in the laboratory. The dependency of laboratory measured relative permeability on flowrate has long been both supported and challenged by a number of investigators. Studies have shown that this apparent flowrate dependency is a result of both sub-core scale heterogeneity and outlet boundary effects. However this has only been demonstrated numerically for highly simplified models of porous media. In this paper, flowrate dependency of effective relative permeability is demonstrated using two rock cores, a Berea Sandstone and a heterogeneous sandstone from the Otway Basin Pilot Project in Australia. Numerical simulations of steady-state coreflooding experiments are conducted at a number of injection rates using a single set of input characteristic relative permeability curves. Effective relative permeability is then calculated from the simulation data using standard interpretation methods for calculating relative permeability from steady-state tests. Results show that simplified approaches may be used to determine flowrate-independent characteristic relative permeability provided flow rate is sufficiently high, and the core heterogeneity is relatively low. It is also shown that characteristic relative permeability can be determined at any typical flowrate, and even for geologically complex models, when using accurate three-dimensional models.
Relative air permeability as function of saturation in soil venting
Stylianou, C.; DeVantier, B.A.
1995-04-01
Traditionally, soil remediation involved soil flushing, or excavation followed by landfilling or treatment. In recent years, recognizing the major environmental problem of soil contamination by VOCs, soil vapor extraction (SVE, also known as soil venting) has been applied as a form of in situ remediation. A key parameter in modeling soil-venting systems is relative air permeability, determined as a function of liquid saturation. The focus of the present study was to characterize the relationship of the relative air permeability as a function of air saturation in soil-venting systems. A new laboratory apparatus was used to simulate the soil venting and measure the air permeability of soil samples. Sand samples wetted with mixtures of water and gasoline at different ratios were used. It was revealed that the prediction of relative air permeability for moist noncohesive soil can be made in terms of intrinsic permeability and air-filled porosity alone, and not the type of liquid present in the pores. Comparisons of measured data with existing relations for relative air permeability as a function of total liquid saturation were made to determine the most accurate and practical forms for engineering applications. For the sand sample used, the evaluation revealed that compared to the existing relations, a derived second-order polynomial expression provides a good estimate of relative air permeability and does not require estimation of soil-water-retention curve parameters.
IMPACT OF CAPILLARY AND BOND NUMBERS ON RELATIVE PERMEABILITY
Kishore K. Mohanty
2002-09-30
Recovery and recovery rate of oil, gas and condensates depend crucially on their relative permeability. Relative permeability in turn depends on the pore structure, wettability and flooding conditions, which can be represented by a set of dimensionless groups including capillary and bond numbers. The effect of flooding conditions on drainage relative permeabilities is not well understood and is the overall goal of this project. This project has three specific objectives: to improve the centrifuge relative permeability method, to measure capillary and bond number effects experimentally, and to develop a pore network model for multiphase flows. A centrifuge has been built that can accommodate high pressure core holders and x-ray saturation monitoring. The centrifuge core holders can operate at a pore pressure of 6.9 MPa (1000 psi) and an overburden pressure of 17 MPa (2500 psi). The effect of capillary number on residual saturation and relative permeability in drainage flow has been measured. A pore network model has been developed to study the effect of capillary numbers and viscosity ratio on drainage relative permeability. Capillary and Reynolds number dependence of gas-condensate flow has been studied during well testing. A method has been developed to estimate relative permeability parameters from gas-condensate well test data.
Relating tortuosity and permeability in microfractured and unfractured porous media
NASA Astrophysics Data System (ADS)
Tokan-Lawal, A.; Wang, W.; Prodanovic, M.
2012-12-01
Permeability estimates are key to any subsurface flow prediction. Several methods are available for estimating (relative) permeability either on Darcy scale (lab measurements) or on pore scale (numerical flow simulation, assuming pore space geometry is known). However, relative permeability measurements in particular can be time consuming, and there is a benefit in having a fast estimate. Thus, a number of permeability estimates are available based on the some known porous medium parameters. The famous Carman Kozeny (1937) model represents the pores as parallel tubes of length equal to the sample length and of a range of radii. This single phase permeability model developed for packings of equal spherical grains relates the absolute permeability to the tortuosity of the medium. Fractures or fracture networks, on the other hand, do not lend themselves to an analytical description akin to pores spaces in-between a packing of spheres. Thus far, the study of flow in fractures has for the most part been limited to fractures in rock with impermeable fractures. The simplest models, such as the cubic law, relate fracture permeability to its average aperture and model fracture as parallel planes which are insufficient to extend to multiphase displacement. In this study, we focus on correlating permeability with geometric tortuosity of both pore space and individual fluid phases for a wide variety of homogeneous as well as microfractured porous samples. We use a combination of lattice-Boltzmann simulation and the level set method based progressive-quasistatic (LSMPQS) algorithm to characterize the capillary dominated flow properties (capillary pressure-saturation and relative permeability-saturation relationships) of the matrix, and when present, the fracture, in samples of different compositions. At the same time, we use image analysis tools to characterize the connectivity and tortuosity of the pore space, as well as individual fluid phases at different saturations
Combining SIP and NMR Measurements to Develop Improved Estimates of Permeability in Sandstone Cores
NASA Astrophysics Data System (ADS)
Keating, K.; Binley, A. M.
2013-12-01
Permeability is traditionally measured in-situ by inducing groundwater flow using pumping, slug, or packer tests; however, these methods require the existence of wells, can be labor intensive and can be constrained by measurement support volumes. Indirect estimates of permeability based on geophysical techniques benefit from relatively short measurement times, do not require fluid extraction, and are non-invasive when made from the surface (or minimally invasive when made in a borehole). However, estimates of permeability based on a single geophysical method often require calibration for rock type, and cannot be used to uniquely determine all of the physical properties required to accurately determine permeability. In this laboratory study we present the first critical step towards developing a method for estimating permeability based on the synergistic coupling of two complementary geophysical methods: spectral induced polarization (SIP) and nuclear magnetic resonance (NMR). To develop an improved model for estimating permeability, laboratory SIP and NMR measurements were collected on a series of sandstone cores, covering a wide range of permeabilities. Current models for estimating permeability from each individual geophysical measurement were compared to independently obtained estimates of permeability. The comparison confirmed previous research showing that estimates from SIP or NMR alone only yield the permeability within order of magnitude accuracy and must be calibrated for rock type. Next, the geophysical parameters determined from SIP and NMR were compared to independent measurements the physical properties of the sandstone cores including gravimetric porosity and pores-size distributions (obtained from mercury injection porosimetry); this comparison was used to evaluate which geophysical parameter more consistently and accurately predicted each physical property. Finally, we present an improved method for estimating permeability in sandstone cores based
Perm-Fit: a new program to estimate permeability at high P-T conditions
NASA Astrophysics Data System (ADS)
Moulas, Evangelos; Madonna, Claudio
2016-04-01
Several geological processes are controlled by porous fluid flow. The circulation of porous fluids influences many physical phenomena and in turn it depends on the rock permeability. The permeability of rocks is a physical property that needs to be measured since it depends on many factors such as secondary porosity (fractures etc). We present a numerical approach to estimate permeability using the transient step method (Brace et al., 1968). When a non-reacting, compressible fluid is considered in a relative incompressible solid matrix, the only unknown parameter in the equations of porous flow is permeability. Porosity is assumed to be known and the physical properties of the fluid (compressibility, density, viscosity) are taken from the NIST database. Forward numerical calculations for different values of permeability are used and the results are compared to experimental measurements. The extracted permeability value is the one that minimizes the misfit between experimental and numerical results. The uncertainty on the value of permeability is estimated using a Monte Carlo method. REFERENCES Brace, W.F., Walsh J.B., & Frangos, W.T. 1968: Permeability of Granite under High Pressure, Journal of Geophysical Research, 73, 6, 2225-2236
Permeability Coefficients of Lipophilic Compounds Estimated by Computer Simulations.
Ghaemi, Zhaleh; Alberga, Domenico; Carloni, Paolo; Laio, Alessandro; Lattanzi, Gianluca
2016-08-01
The ability of a drug to cross the intestine-blood barrier is a key quantity for drug design and employment and is normally quantified by the permeability coefficient P, often evaluated in the so-called Caco-2 assay. This assay is based on measuring the initial growth rate of the concentration of the drug beyond the cellular barrier but not its steady-state flux through the membrane. This might lead to confusion since, in the case of lipophilic drugs, the initial slope is strongly affected by the retention of the drug in the membrane. This effect is well known but seldom considered in the assay. Here, we exploit all-atoms molecular dynamics and bias exchange metadynamics to calculate the concentration of two lipophilic drugs across a model membrane as a function of time. This allows estimating both the steady-state flux and the initial slope of the concentration growth and comparing Caco-2 and steady-state estimates of P. We show that our computational procedure is able to reproduce the experimental values, although these may differ from the permeability coefficients by orders of magnitude. Our findings are generalized by a simplified one-dimensional model of the permeation process that may act as a roadmap to assess which measure of membrane permeability would be more appropriate and, consequently, whether retention corrections should be included in estimates based on Caco-2 assays. PMID:27392273
Estimated bounds on rock permeability changes from THM Processes
Berge, P A; Blair, S C; Wang, H F
1998-08-01
We performed THM modeling to estimate bounds on permeability changes in the NFE. For our modeling, we used the TM three-dimensional (3-D) finite-difference code FLAC{sup 3D} version 2.0 (Itasca Consulting Group Inc. 1997) to compute changes in stress and displacement in an elastic model subjected to temperature changes over time. Output from TH modeling (Hardin et al., 1998, Chapter 3) using the code NUFT (Nitao 1993) provided the temperature changes for input to FLAC{sup 3D}. We then estimated how the stress changes could affect permeability. For this report, we chose to base our 3-D THM modeling on a coarser version of the 2-D model we ran for the work described in Chapter 4 of the Near-Field/Altered Zone Models Report (Hardin et al., 1998, Chapter 4). The grid and temperature field were based on those used by the TH code for 50 yr of heating for the reference Case 1 TH model calculated using Total System Performance Assessment-Viability Assessment (TSPA-VA) base-case properties, nominal infiltration, and a point-load repository design (Hardin et al., 1998, Chapter 3). The stress field rotated in the region between and below the drifts after 50 yr of heating. High vertical shear stresses were computed for these regions. The maximum computed displacement was about 7 cm, mainly vertical. Estimates of permeability changes were obtained by analyzing stresses, following a method we developed previously for 2-D models. In our 3-D modeling for this report, we only considered vertical and horizontal fractures. We extended our 2-D method to a simplified 3-D case. We conclude that widespread permeability enhancement is likely for fractures parallel to NS fracture set No.2, the vertical fractures that strike north-south, for regions above the drifts. In some regions just above the drifts, permeability may increase by a minimum of a factor of two and possibly more than a factor of four if slip also occurs along the vertical fractures in EW set No.1, the east-west fractures
Wettability effects on two- and three-fluid relative permeabilities
NASA Astrophysics Data System (ADS)
Bradford, Scott A.; Abriola, Linda M.; Leij, Feike J.
1997-10-01
Specification of relative permeability ( kr)-saturation ( S) relations for all fluid phases is required for the simulation of multiphase flow and transport in porous media. Indirect methods are frequently employed to estimate these kr- S relations owing to the time, expense, and difficulty associated with direct measurements. A common indirect approach uses capillary pressure data in conjunction with a selected pore-size distribution model to estimate kr- S relations. Such methods typically assume perfect wettability of the solid. Natural porous media, however, are composed of a variety of mineral constituents with different adsorptive properties, which can exhibit non-zero contact angles and/or fractional wettability. Consequently, fluid distributions in natural media may be more complex than those predicted by simple pore-size distribution models and, under such conditions, current estimation approaches for kr may be inadequate. In this work, the pore-size distribution model of N.T. Burdine (1953, Relative permeability calculations from pore-size distribution data. Transactions of the American Institute of Mining, Metallurgical and Petroleum Engineers 198, 71-77) is extended to incorporate wettability variations. In this model, wetting and less wetting (non-wetting or intermediate) fluid pore classes are used to calculate kr for water or organic. The wettability of the porous medium is used to determine the contributions of the pore classes to kr. For both two- and three-fluid systems, the model predicts that an increase in the contact angle (measured through water) or organic-wet fraction of a medium will be accompanied by an increase in the water kr and a decrease in the organic kr. In three-fluid media, kr values for water and organic depend on both liquid saturations when the solid is imperfectly wetted. The model assumes that wettability variation has no influence on the air kr. Model predictions are shown to be consistent with available experimental data.
Effective parameterizations of three nonwetting phase relative permeability models
NASA Astrophysics Data System (ADS)
Yang, Zhenlei; Mohanty, Binayak P.
2015-08-01
Describing convective nonwetting phase flow in unsaturated porous media requires knowledge of the nonwetting phase relative permeability. This study was conducted to formulate and derive a generalized expression for the nonwetting phase relative permeability via combining with the Kosugi water retention function. This generalized formulation is then used to flexibly investigate the Burdine, Mualem, and Alexander and Skaggs models' prediction accuracy for relative nonwetting phase permeability. The model and data comparison results show that these three permeability models, if used in their original form, but applied to the nonwetting phase, could not predict the experimental data well. The optimum pore tortuosity and connectivity value is thus obtained for the improved prediction of relative nonwetting phase permeability. As a result, the effective parameterization of (α,β,η) parameters in the modified Burdine, modified Mualem, and modified Alexander and Skaggs permeability models were found to be (2.5, 2, 1), (2, 1, 2), and (2.5, 1, 1), respectively. These three suggested models display the highest accuracy among the nine relative permeability models investigated in this study. However, the corresponding discontinuous nonwetting phase and the liquid film flow should be accounted for in future for the improved prediction of nonwetting phase relative permeability at very high and very low water saturation range, respectively.
A relative permeability modifier for water control of gas wells in a low-permeability reservoir
Chen Tielong; Zhao Yong; Peng Kezong; Pu Wanfeng
1996-08-01
Water control in gas wells is a major measure to enhance gas recovery. The work is concentrated on finding a highly selective polymer to reduce water production without affecting gas production from gas wells in low-permeability reservoirs. This paper presents the conceptions of residual resistance factors (RRF`s) to both wetting and non-wetting phases and the laboratory experimental and field trial results of relative permeability modifiers for water control in gas wells.
Extending Nuclear Magnetic Resonance Data for Permeability Estimation in Fine-Grained Sediments
NASA Astrophysics Data System (ADS)
Daigle, H.; Dugan, B.
2008-12-01
We developed a method for using nuclear magnetic resonance (NMR) T2 data and gamma ray data to estimate lithology-dependent permeability in silt- and clay-rich sediments. This model, based on the Schlumberger-Doll Research (SDR) model, allows for high resolution (<1 m) permeability estimates throughout a logged interval. Our model was calibrated using direct measurements on core samples from Keathley Canyon Lease Block 151 in the northern Gulf of Mexico. From NMR and gamma ray data we are able to determine permeability from 10-18 to 10-14 m2 (0.001 to 10 millidarcies). Thus from discrete core samples and log data we were able to develop a permeability model for the entire sedimentary column (425 m). Lithologic variation was incorporated into the model by varying the A coefficient based on the gamma ray response. This provides a more accurate permeability model than assigning a constant value to A as is typically done. The relationship between A and intrinsic lithologic properties is unclear; simple pore system models suggest that A may be related to specific surface, tortuosity, and pore structure; we investigate simple models to quantify how these properties vary with sediment consolidation and what their relationship is to A. A comprehensive understanding that links NMR data and A to pore-scale properties will provide new constraints on deformation and flow in porous systems, and will contribute to our understanding of sediment properties for fluid flow modeling at local and regional scales.
Blair, S.C.; Berge, P.A.; Berryman, J.G.
1993-08-01
We have developed an image-processing method for characterizing the microstructure of rock and other porous materials, and for providing a quantitative means for understanding the dependence of physical properties on the pore structure. This method is based upon the statistical properties of the microgeometry as observed in scanning electron micrograph (SEM) images of cross sections of porous materials. The method utilizes a simple statistical function, called the spatial correlation function, which can be used to predict bounds on permeability and other physical properties. We obtain estimates of the porosity and specific surface area of the material from the two-point correlation function. The specific surface area can be related to the permeability of porous materials using a Kozeny-Carman relation, and we show that the specific surface area measured on images of sandstones is consistent with the specific surface area used in a simple flow model for computation of permeability. In this paper, we discuss the two-point spatial correlation function and its use in characterizing microstructure features such as pore and grain sizes. We present estimates of permeabilities found using SEM images of several different synthetic and natural sandstones. Comparison of the estimates to laboratory measurements shows good agreement. Finally, we briefly discuss extension of this technique to two-phase flow.
Estimating changes in rock permeability due to thermal-mechanical effects
Wang, H.F.; Blair, S.C.; Berge, P.A.
1997-10-01
This paper presents results of a modeling study of changes in fracture permeability due to thermal-mechanical effects associated with the potential geological repository at Yucca Mountain. a methodology for estimating changes in permeability is developed and applied to the Drift Scale Test (DST) now being conducted in the Exploratory Studies Facility (ESF) at Yucca Mountain. Temperature, stress, and displacement of rock in the heated zone are presented along with predicted zones where slip on fractures may occur. The zones of predicted fracture slip are used as a basis for predicting where permeability may be changed. this new procedure goes beyond previous models that relate stress to strain or displacement, and provides information about rock response that is needed for design of future tests at Yucca Mountain. Our results also contribute to the understanding of coupled processes in the near-field environment of a repository.
Effective Permeability and Miniaturization Estimation of Ferrite-loaded Microstrip Patch Antenna
NASA Astrophysics Data System (ADS)
Saini, Ashish; Thakur, Atul; Thakur, Preeti
2016-08-01
Miniaturization of a microstrip patch antenna using composite nanosized ferrite material is proposed in this paper. Detailed simulations were performed to analyze the effect of increase in relative permeability of substrate material on physical size and efficiency of a microstrip antenna. An analytical expression for estimation of the effective relative permeability is established here on the basis of the detailed simulation. Composite nano ferrite (Mn0.5Zn0.35Co0.15Fe2O4 + SrFe12O19) with an average crystallite size of 72 nm was synthesized and characterized for electromagnetic properties. The substrate material was prepared by the co-precipitation method. Matching values of complex permittivity ( ɛ* = 4.1-0.1j) and complex permeability ( μ* = 3.72-0.28j) up to 1 GHz were obtained from the electromagnetic characterization. Measurement of the resonant frequency of the fabricated antenna validates the derived expression of effective relative permeability. It reduces the error in calculation of resonant frequency from 10% to 1%. Simulation and measurement results also confirm that an antenna fabricated with the above parameters can reduce the patch size by almost 44% and increases -10 dB reflection loss bandwidth over a pure dielectric FR4 substrate. Therefore, we propose here an analytical expression for estimation of effective relative permeability and Mn0.5Zn0.35Co0.15Fe2O4 + SrFe12O19 composite nano ferrites as suitable candidate for a high-bandwidth miniaturized antenna in the microwave frequency range.
NASA Astrophysics Data System (ADS)
Emanuele Rizzo, Roberto; Healy, David; De Siena, Luca
2016-04-01
The success of any predictive model is largely dependent on the accuracy with which its parameters are known. When characterising fracture networks in fractured rock, one of the main issues is accurately scaling the parameters governing the distribution of fracture attributes. Optimal characterisation and analysis of fracture attributes (lengths, apertures, orientations and densities) is fundamental to the estimation of permeability and fluid flow, which are of primary importance in a number of contexts including: hydrocarbon production from fractured reservoirs; geothermal energy extraction; and deeper Earth systems, such as earthquakes and ocean floor hydrothermal venting. Our work links outcrop fracture data to modelled fracture networks in order to numerically predict bulk permeability. We collected outcrop data from a highly fractured upper Miocene biosiliceous mudstone formation, cropping out along the coastline north of Santa Cruz (California, USA). Using outcrop fracture networks as analogues for subsurface fracture systems has several advantages, because key fracture attributes such as spatial arrangements and lengths can be effectively measured only on outcrops [1]. However, a limitation when dealing with outcrop data is the relative sparseness of natural data due to the intrinsic finite size of the outcrops. We make use of a statistical approach for the overall workflow, starting from data collection with the Circular Windows Method [2]. Then we analyse the data statistically using Maximum Likelihood Estimators, which provide greater accuracy compared to the more commonly used Least Squares linear regression when investigating distribution of fracture attributes. Finally, we estimate the bulk permeability of the fractured rock mass using Oda's tensorial approach [3]. The higher quality of this statistical analysis is fundamental: better statistics of the fracture attributes means more accurate permeability estimation, since the fracture attributes feed
Water retention and gas relative permeability of two industrial concretes
Chen Wei; Liu Jian; Brue, Flore; Skoczylas, Frederic; Davy, C.A.; Bourbon, Xavier; Talandier, Jean
2012-07-15
This experimental study aims at identifying the water retention properties of two industrial concretes to be used for long term underground nuclear waste storage structures. Together with water retention, gas transfer properties are identified at varying water saturation level, i.e. relative gas permeability is assessed directly as a function of water saturation level S{sub w}. The influence of the initial de-sorption path and of the subsequent re-saturation are analysed both in terms of water retention and gas transfer properties. Also, the influence of concrete microstructure upon water retention and relative gas permeability is assessed, using porosity measurements, analysis of the BET theory from water retention properties, and MIP. Finally, a single relative gas permeability curve is proposed for each concrete, based on Van Genuchten-Mualem's statistical model, to be used for continuous modelling approaches of concrete structures, both during drying and imbibition.
The Interfacial-Area-Based Relative Permeability Function
Zhang, Z. F.; Khaleel, Raziuddin
2009-09-25
CH2M Hill Plateau Remediation Company (CHPRC) requested the services of the Pacific Northwest National Laboratory (PNNL) to provide technical support for the Remediation Decision Support (RDS) activity within the Soil & Groundwater Remediation Project. A portion of the support provided in FY2009, was to extend the soil unsaturated hydraulic conductivity using an alternative approach. This alternative approach incorporates the Brooks and Corey (1964), van Genuchten (1980), and a modified van Genuchten water-retention models into the interfacial-area-based relative permeability model presented by Embid (1997). The general performance of the incorporated models is shown using typical hydraulic parameters. The relative permeability models for the wetting phase were further examined using data from literature. Results indicate that the interfacial-area-based model can describe the relative permeability of the wetting phase reasonably well.
Lenormand, R.; Thiele, M.R.
1997-08-01
The paper describes the method and presents preliminary results for the calculation of homogenized relative permeabilities
Simulating residual saturation and relative permeability in heterogeneous formations
Paterson, L.; Painter, S.; Zhang, Xiaodong
1996-12-31
Network models are used to investigate the effect of correlated heterogeneity on capillary dominated displacements in porous media. Residual saturations and relative permeabilities are shown to be sensitive to the degree of correlation and anisotropy but not variability. The network models reproduce the experimental observation that relative permeability is greater in the direction parallel to the bedding compared to perpendicular to the bedding. The scatter commonly observed in core measurements of residual saturation is attributed to the presence of correlated heterogeneity in actual reservoir rocks.
Comparative assessment of three-phase oil relative permeability models
NASA Astrophysics Data System (ADS)
Ranaee, Ehsan; Riva, Monica; Porta, Giovanni M.; Guadagnini, Alberto
2016-07-01
We assess the ability of 11 models to reproduce three-phase oil relative permeability (kro) laboratory data obtained in a water-wet sandstone sample. We do so by considering model performance when (i) solely two-phase data are employed to render predictions of kro and (ii) two and three-phase data are jointly used for model calibration. In the latter case, a Maximum Likelihood (ML) approach is used to estimate model parameters. The tested models are selected among (i) classical models routinely employed in practical applications and implemented in commercial reservoir software and (ii) relatively recent models which are considered to allow overcoming some drawbacks of the classical formulations. Among others, the latter set of models includes the formulation recently proposed by Ranaee et al., which has been shown to embed the critical effects of hysteresis, including the reproduction of oil remobilization induced by gas injection in water-wet media. We employ formal model discrimination criteria to rank models according to their skill to reproduce the observed data and use ML Bayesian model averaging to provide model-averaged estimates (and associated uncertainty bounds) of kro by taking advantage of the diverse interpretive abilities of all models analyzed. The occurrence of elliptic regions is also analyzed for selected models in the framework of the classical fractional flow theory of displacement. Our study confirms that model outcomes based on channel flow theory and classical saturation-weighted interpolation models do not generally yield accurate reproduction of kro data, especially in the regime associated with low oil saturations, where water alternating gas injection (WAG) techniques are usually employed for enhanced oil recovery. This negative feature is not observed in the model of Ranaee et al. (2015) due to its ability to embed key effects of pore-scale phase distributions, such as hysteresis effects and cycle dependency, for modeling kro observed
NASA Astrophysics Data System (ADS)
Rios, Edmilson Helton; Figueiredo, Irineu; Moss, Adam Keith; Pritchard, Timothy Neil; Glassborow, Brent Anthony; Domingues, Ana Beatriz Guedes; Azeredo, Rodrigo Bagueira de Vasconcellos
2016-07-01
The effect of the selection of different nuclear magnetic resonance (NMR) relaxation times for permeability estimation is investigated for a set of fully brine-saturated rocks acquired from Cretaceous carbonate reservoirs in the North Sea and Middle East. Estimators that are obtained from the relaxation times based on the Pythagorean means are compared with estimators that are obtained from the relaxation times based on the concept of a cumulative saturation cut-off. Select portions of the longitudinal (T1) and transverse (T2) relaxation-time distributions are systematically evaluated by applying various cut-offs, analogous to the Winland-Pittman approach for mercury injection capillary pressure (MICP) curves. Finally, different approaches to matching the NMR and MICP distributions using different mean-based scaling factors are validated based on the performance of the related size-scaled estimators. The good results that were obtained demonstrate possible alternatives to the commonly adopted logarithmic mean estimator and reinforce the importance of NMR-MICP integration to improving carbonate permeability estimates.
NASA Astrophysics Data System (ADS)
Rios, Edmilson Helton; Figueiredo, Irineu; Moss, Adam Keith; Pritchard, Timothy Neil; Glassborow, Brent Anthony; Guedes Domingues, Ana Beatriz; Bagueira de Vasconcellos Azeredo, Rodrigo
2016-07-01
The effect of the selection of different nuclear magnetic resonance (NMR) relaxation times for permeability estimation is investigated for a set of fully brine-saturated rocks acquired from Cretaceous carbonate reservoirs in the North Sea and Middle East. Estimators that are obtained from the relaxation times based on the Pythagorean means are compared with estimators that are obtained from the relaxation times based on the concept of a cumulative saturation cut-off. Select portions of the longitudinal (T1) and transverse (T2) relaxation-time distributions are systematically evaluated by applying various cut-offs, analogous to the Winland-Pittman approach for mercury injection capillary pressure (MICP) curves. Finally, different approaches to matching the NMR and MICP distributions using different mean-based scaling factors are validated based on the performance of the related size-scaled estimators. The good results that were obtained demonstrate possible alternatives to the commonly adopted logarithmic mean estimator and reinforce the importance of NMR-MICP integration to improving carbonate permeability estimates.
Tracer kinetic modelling in MRI: estimating perfusion and capillary permeability
NASA Astrophysics Data System (ADS)
Sourbron, S. P.; Buckley, D. L.
2012-01-01
The tracer-kinetic models developed in the early 1990s for dynamic contrast-enhanced MRI (DCE-MRI) have since become a standard in numerous applications. At the same time, the development of MRI hardware has led to increases in image quality and temporal resolution that reveal the limitations of the early models. This in turn has stimulated an interest in the development and application of a second generation of modelling approaches. They are designed to overcome these limitations and produce additional and more accurate information on tissue status. In particular, models of the second generation enable separate estimates of perfusion and capillary permeability rather than a single parameter Ktrans that represents a combination of the two. A variety of such models has been proposed in the literature, and development in the field has been constrained by a lack of transparency regarding terminology, notations and physiological assumptions. In this review, we provide an overview of these models in a manner that is both physically intuitive and mathematically rigourous. All are derived from common first principles, using concepts and notations from general tracer-kinetic theory. Explicit links to their historical origins are included to allow for a transfer of experience obtained in other fields (PET, SPECT, CT). A classification is presented that reveals the links between all models, and with the models of the first generation. Detailed formulae for all solutions are provided to facilitate implementation. Our aim is to encourage the application of these tools to DCE-MRI by offering researchers a clearer understanding of their assumptions and requirements.
NASA Astrophysics Data System (ADS)
Nambi, I.; Mukunda, P.; Kumar N, S.
2009-12-01
Predicting Dissolution of Entrapped NAPL in Heterogeneous Aquifers Using New Relative Permeability Correlations Indumathi M. Nambi1, Pavitra,M2 and Sateesh Kumar N2 1Assistant Professor, 2 PhD Student, 3 Graduate Student Department of Civil Engineering, Indian Institute of Technology Madras, India Non-Aqueous Phase Liquids such as organic compounds are major sources of groundwater contamination throughout the world. The non-uniform distribution of these contaminants as NAPL pools and NAPL residuals introduce additional spatial heterogeneity in the hydrogeological parameters such as porosity and permeability. In addition to this, as the NAPL dissolve over time, the hydrogeological parameter such as relative permeability change as more and more pore space is available for water flow. There are no adequate studies conducted so far to predict the changes taking place in the permeability of a contaminated region. The existing models have repeatedly used models developed based on two phase flow experiments such as Corey’s and Wylie’s equations which relate relative permeability to effective water saturation. It is hypothesized that the pattern of changes in relative permeability as the NAPL pools or residuals dissolve is quite different from the relative permeability variations during two phase flow. Hence the use of these empirical relationships developed for relative permeabilities as a function of effective permeabilities for the case of dissolving NAPL pools is questionable. In this study, column dissolution experiments were conducted in a simplified heterogeneous system and the changes in relative permeabilities were quantified by measuring differential pressures at various time points. The NAPL saturations were also quantified as the NAPL dissolved by estimating aqueous phase concentrations and applying mass balance. These experimental data when compared to the existing correlation predictions proved our hypothesis that the relative permeability variations as
NASA Astrophysics Data System (ADS)
Zambrano, Miller; Tondi, Emanuele; Mancini, Lucia; Trias, F. Xavier; Arzilli, Fabio; Lanzafame, Gabriele; Aibibula, Nijiati
2016-04-01
In porous rocks strain is commonly localized in narrow Deformation Bands (DBs), where the petrophysical properties are significantly modified with respect the pristine rock. As a consequence, DBs could have an important effect on production and development of porous reservoirs representing baffles zones or, in some cases, contribute to reservoir compartmentalization. Taking in consideration that the decrease of permeability within DBs is related to changes in the porous network properties (porosity, connectivity) and the pores morphology (size distribution, specific surface area), an accurate porous network characterization is useful for understanding both the effect of deformation banding on the porous network and their influence upon fluid flow through the deformed rocks. In this work, a 3D characterization of the microstructure and texture of DBs hosted in porous carbonate grainstones was obtained at the Elettra laboratory (Trieste, Italy) by using two different techniques: phase-contrast synchrotron radiation computed microtomography (micro-CT) and microfocus X-ray micro-CT. These techniques are suitable for addressing quantitative analysis of the porous network and implementing Computer Fluid Dynamics (CFD)experiments in porous rocks. Evaluated samples correspond to grainstones highly affected by DBs exposed in San Vito Lo Capo peninsula (Sicily, Italy), Favignana Island (Sicily, Italy) and Majella Mountain (Abruzzo, Italy). For the analysis, the data were segmented in two main components porous and solid phases. The properties of interest are porosity, connectivity, a grain and/or porous textural properties, in order to differentiate host rock and DBs in different zones. Permeability of DB and surrounding host rock were estimated by the implementation of CFD experiments, permeability results are validated by comparing with in situ measurements. In agreement with previous studies, the 3D image analysis and flow simulation indicate that DBs could be constitute
Estimation of In Situ Stress and Permeability from an Extended Leak-off Test
NASA Astrophysics Data System (ADS)
Nghiep Quach, Quoc; Jo, Yeonguk; Chang, Chandong; Song, Insun
2016-04-01
Among many parameters needed to analyze a variety of geomechanical problems related to subsurface CO2 storage projects, two important ones are in situ stress states and permeability of the storage reservoirs and cap rocks. In situ stress is needed for investigating potential risk of fault slip in the reservoir systems and permeability is needed for assessing reservoir flow characteristics and sealing capability of cap rocks. We used an extended leak-off test (XLOT), which is often routinely conducted to assess borehole/casing integrity as well as fracture gradient, to estimate both in situ least principal stress magnitude and in situ permeability in a CO2 storage test site, offshore southeast Korea. The XLOT was conducted at a casing shoe depth (700 m below seafloor) within the cap rock consisting of mudstone, approximately 50 m above the interface between cap rock and storage reservoir. The test depth was cement-grouted and remained for 4 days for curing. Then the hole was further drilled below the casing shoe to create a 4 m open-hole interval at the bottom. Water was injected using hydraulic pump at an approximately constant flowrate into the bottom interval through the casing, during which pressure and flowrate were recorded continuously at the surface. The interval pressure (P) was increased linearly with time (t) as water was injected. At some point, the slope of P-t curve deviated from the linear trend, which indicates leak-off. Pressure reached its peak upon formation breakdown, followed by a gradual pressure decrease. Soon after the formation breakdown, the hole was shut-in by pump shut-off, from which we determined the instantaneous shut-in pressure (ISIP). The ISIP was taken to be the magnitude of the in situ least principal stress (S3), which was determined to be 12.1 MPa. This value is lower than the lithostatic vertical stress, indicating that the S3 is the least horizontal principal stress. The determined S3 magnitude will be used to characterize the
NASA Astrophysics Data System (ADS)
Woith, Heiko; Chiodini, Giovanni; Mangiacapra, Annarita; Wang, Rongjiang
2016-04-01
The hydrothermal system beneath Campi Flegrei is strongly affected by sub-surface processes as manifested by a geothermal "plume" below Solfatara, associated with the formation of mud-pools (Fangaia), fumaroles (Bocca Grande, Pisciarelli), and thermal springs (Agnano). Within the frame of MED-SUV (The MED-SUV project has received funding from the European Union Seventh Framework Programme FP7 under Grant agreement no 308665), pressure transients in the hydrothermal system of Campi Flegrei are being continuously monitored at fumaroles, mudpools, hot springs, and geothermal wells. In total, waterlevel and temperature is recorded at 8 sites across the hydrothermal plume along a profile aligned between Agnano Termal in the East and Fangaia in the West. Autonomous devices are used to record the water level and water temperature at 10 minute intervals. At Fangaia mudpool water level and water temperature are dominantly controlled by rain water. Thus, the pool is refilled episodically. Contrary, the water level at a well producing hot water (82°C) for the Pisciarelli tennis club drops and recovers at nearly regular intervals. The induced water level changes are of the order of 1-2m and 3-4m in case of the mudpool and the hot-water-well, respectively. At first glance, both monitoring sites might seem to be fully useless to access natural changes in the Campi Flegrei fluid system. At a second thought, both timeseries provide a unique opportunity to monitor potential permeability changes in the aquifer system. A similar approach had been proposed to deduce earthquake-related permeability changes from Earth tide variations. Contrary to the indirect Earth tide approach, we have the chance to estimate the hydraulic aquifer properties from our monitoring data directly, since each time series contains a sequence of discrete hydraulic tests - namely drawdown tests and refill experiments. Although our Cooper-Jacob approach is really crude, we obtained reasonable permeability
Measurement of relative Ca²⁺ permeability during sustained activation of TRPV1 receptors.
Samways, Damien S K; Tomkiewicz, Evan; Langevin, Olivia M; Bukhari, Maurish
2016-02-01
Some cation permeable ligand-gated ion channels, including the capsaicin-sensitive TRPV1, have been reported to exhibit a time-dependent increase in permeability to large inorganic cations during sustained activation, a phenomenon termed "pore dilation." TRPV1 conducts substantial Ca(2+) entry, and it has been suggested that this channel undergoes a time-dependent change in Ca(2+) permeability relative to Na(+) (P Ca/P Na) that parallels pore dilation. However, our experiments employing whole cell patch clamp photometry and single channel recordings to directly measure relative Ca(2+) current in TRPV1 expressing HEK293 cells show that relative Ca(2+) influx remains constant for the duration of capsaicin-evoked channel activation. Further, we present evidence from patch clamp photometry experiments suggesting that sustained activation of Ca(2+) permeable ion channels in the voltage-clamp configuration leads to rapid saturation of the pipette Ca(2+) chelator, and that subsequent observed shifts in the current reversal potentials in the presence of extracellular Ca(2+) are likely due to intracellular accumulation of this ion and a movement of the Ca(2+) equilibrium potential (E Ca) towards zero. Finally, using an adapted reversal potential-based protocol in which cells are only exposed to Ca(2+) after sustained capsaicin exposure in the absence of added extracellular Ca(2+), we demonstrate that the calculated P Ca/P Na is unaffected by duration of TRPV1 activation. In conclusion, we find no evidence in support of a time-dependent change in P Ca/P Na for TRPV1. Our data further urges caution in estimating relative Ca(2+) permeability using reversal potentials, as there is a limited time window in which the cytosolic Ca(2+) chelator included in the patch pipette can prevent localised elevations in cytosolic free Ca(2+) and thus allow for an accurate estimate of this important channel permeability parameter.
Use of geophysical logs to estimate the quality of ground water and the permeability of aquifers
Hudson, J.D.
1996-01-01
The relation of formation factor to resistivity of formation water and intergranular permeability has often been investigated, and the general consensus is that this relation is closest when established in a clean-sand aquifer in which water quality does not vary substantially. When these restrictions are applied, the following standard equation is a useful tool in estimating the resistance of the formation water: F = Ro/Rw, where F is the formation factor, which is a function of the effective porosity; Ro is the resistivity of a formation that is 100 percent saturated with interstitial water; and Rw is the resistivity of the water in the saturated zone. However, arenaceous aquifers can have electrical resistivities that are not directly related to resistivity of water or porosity. Surface conductivity and ion exchange are significant factors when the sediments are clay bearing. The solid constituents are a major component of the parameters needed to solve the equation for formation-water resistivity and estimates of aquifer permeability. A correction process needs to be applied to adjust the variables, Ro and F, to the equivalent of clean sand. This report presents an empirical method of using the neutron log and the electrical-resistivity values from long- and short-normal resistivity logs to correct for fine-grained material and the subsequent effects of low impedance to electrical flow that are not related to the resistance of formation water.
PARAMETER ESTIMATION OF TWO-FLUID CAPILLARY PRESSURE-SATURATION AND PERMEABILITY FUNCTIONS
Capillary pressure and permeability functions are crucial to the quantitative description of subsurface flow and transport. Earlier work has demonstrated the feasibility of using the inverse parameter estimation approach in determining these functions if both capillary pressure ...
NASA Astrophysics Data System (ADS)
Rizzo, R. E.; Healy, D.; De Siena, L.
2015-12-01
The success of any model prediction is largely dependent on the accuracy with which its parameters are known. In characterising fracture networks in naturally fractured rocks, the main issues are related with the difficulties in accurately up- and down-scaling the parameters governing the distribution of fracture attributes. Optimal characterisation and analysis of fracture attributes (fracture lengths, apertures, orientations and densities) represents a fundamental step which can aid the estimation of permeability and fluid flow, which are of primary importance in a number of contexts ranging from hydrocarbon production in fractured reservoirs and reservoir stimulation by hydrofracturing, to geothermal energy extraction and deeper Earth systems, such as earthquakes and ocean floor hydrothermal venting. This work focuses on linking fracture data collected directly from outcrops to permeability estimation and fracture network modelling. Outcrop studies can supplement the limited data inherent to natural fractured systems in the subsurface. The study area is a highly fractured upper Miocene biosiliceous mudstone formation cropping out along the coastline north of Santa Cruz (California, USA). These unique outcrops exposes a recently active bitumen-bearing formation representing a geological analogue of a fractured top seal. In order to validate field observations as useful analogues of subsurface reservoirs, we describe a methodology of statistical analysis for more accurate probability distribution of fracture attributes, using Maximum Likelihood Estimators. These procedures aim to understand whether the average permeability of a fracture network can be predicted reducing its uncertainties, and if outcrop measurements of fracture attributes can be used directly to generate statistically identical fracture network models.
NASA Astrophysics Data System (ADS)
Iturrarán-Viveros, Ursula; Parra, Jorge O.
2014-08-01
Permeability and porosity are two fundamental reservoir properties which relate to the amount of fluid contained in a reservoir and its ability to flow. The intrinsic attenuation is another important parameter since it is related to porosity, permeability, oil and gas saturation and these parameters significantly affect the seismic signature of a reservoir. We apply Artificial Neural Network (ANN) models to predict permeability (k) and porosity (ϕ) for a carbonate aquifer in southeastern Florida and to predict intrinsic attenuation (1/Q) for a sand-shale oil reservoir in northeast Texas. In this study, the Gamma test (a revolutionary estimator of the noise in a data set) has been used as a mathematically non-parametric nonlinear smooth modeling tool to choose the best input combination of seismic attributes to estimate k and ϕ, and the best combination of well-logs to estimate 1/Q. This saves time during the construction and training of ANN models and also sets a lower bound for the mean squared error to prevent over-training. The Neural Network method successfully delineates a highly permeable zone that corresponds to a high water production in the aquifer. The Gamma test found nonlinear relations that were not visible to linear regression allowing us to generalize the ANN estimations of k, ϕ and 1/Q for their respective sets of patterns that were not used during the learning phase.
A multiple fractal model for estimating permeability of dual-porosity media
NASA Astrophysics Data System (ADS)
Li, Bo; Liu, Richeng; Jiang, Yujing
2016-09-01
A multiple fractal model that considers the fractal properties of both porous matrices and fracture networks is proposed for the permeability of dual-porosity media embedded with randomly distributed fractures. In this model, the aperture distribution is verified to follow the fractal scaling law, and the porous matrix is assumed to comprise a bundle of tortuous capillaries that also follow the fractal scaling law. Analytical expressions for fractal aperture distribution, total flow rate, total equivalent permeability, and dimensionless permeability are established, where the dimensionless permeability is defined as the ratio of permeability of the porous matrices to that of the fracture networks. The dimensionless permeability is closely correlated to the structural parameters (i.e., α, θ, Dtf, Dtp, De, Dp, emax, λmax) of the dual-porosity media, and it is more sensitive to the fractal dimension for the size distribution of fracture aperture than to that for the size distribution of pore/capillary diameter. The maximum pore/capillary diameter has a greater impact on the dimensionless permeability than that of the maximum fracture aperture. The dimensionless permeability of fracture networks constructed by the fractal aperture distribution has close values with those of models with lognormal aperture distribution. The proposed multiple fractal model does not involve any empirical constants that do not have clear physical meanings, which could serve as a quick estimation method for assessing permeability of dual-porosity media.
Wang, Tsuo-Feng; Kasting, Gerald B; Nitsche, Johannes M
2007-11-01
The full parameterization for the stratum corneum biphasic microtransport model presented previously in this Journal [95:620-648 (2006)] is developed through a combination of fundamental transport theory and calibration with existing data. Of the five microscopic transport properties, four (D(cor), K(cor/w), D(lip), K(lip/w)) are developed from sources independent of the existing steady-state permeability database. The fifth parameter, k(trans) (the mass transfer coefficient for transbilayer hopping), is derived from a fit of the model to the permeability data according to a modified free surface area function of the form log(10) k(trans) = A-B x (MW)(1/3). Examination of the experimental data in terms of the two dimensionless groups, R and sigma, arising from the analysis leads to the conclusion that SC permeation for most compounds is dominated by the transcellular pathway regardless of their lipophilicity, a striking departure from recent skin permeability models. Overall fit of the developed model(s) to the permeability data is somewhat better than for the Potts-Guy equation and variants thereof; however, marked improvement is seen in the estimation of lag times and the related potential for predicting skin hydration effects and transient skin permeation profiles. Simple approximations to the full numerical solution are presented that allow the developed model(s) to be implemented on a spreadsheet.
NASA Astrophysics Data System (ADS)
Mahabadi Mahabad, N.; Jang, J.
2013-12-01
There are several studies of numerical simulation on predicting long-term behavior of hydrate-bearing sediments during gas production. Numerical simulators explore coupled processes that require numerous equations and parameters. Important equations for the estimation of gas production from hydrate-bearing sediments are soil-water characteristic curves and relative permeability equations. These equations require empirical parameters, laboratory and in-situ experiments which are very difficult and expensive. In this research, pore-network model simulation is performed to obtain the fitting parameters for capillary pressure functions and relative permeability equations. First, several sediment packings similar to in-situ sediment are generated by discrete element method. Then, the pore-network model is extracted from the pore space of sediment packing as a system of pores connected at throats. Numerical algorithm to simulate gas hydrate dissociation and gas expansion, and calculate gas and water relative permeability at every saturation is developed for the pore-network model. The assessment of water pore connectivity and the identification of gas clusters are performed using Hoshen-Kopelman algorithm. Finally, reliable fitting parameters for capillary pressure functions and relative permeability equations during gas production will be suggested for further use.
Effect of spreading coefficient on three-phase relative permeability of nonaqueous phase liquids
NASA Astrophysics Data System (ADS)
Keller, Arturo A.; Chen, Mingjie
2003-10-01
Three-phase flow conditions are encountered regularly, for example, during migration of released NAPL through the vadose zone, certain stages of soil vapor extraction, bioslurping, or generation of gases by microbes. To model three-phase flow, a common approach is to construct three-phase relative permeabilities based on a combination of two-phase relative permeabilities. Although this circumvents a lack of experimental data, it can lead to serious underprediction or overprediction of residual NAPL saturation. This can mislead decision makers that need to predict whether a particular spill will reach the water table or predict the speed of a NAPL front or conduct an assessment of the performance of remediation actions. Experimental data to estimate three-phase relative permeabilities is sparse. A study by [2000a] generated significant experimental information. Their analysis focused on the high NAPL saturation region, given their emphasis on oil reservoir engineering. For environmental applications the low saturation region is of more interest. Using this data set, we derived a set of empirical relations that relate NAPL three-phase relative permeability krn to NAPL saturation Sn and spreading coefficient Cs for Sn less than about 0.1, such that krn = ? where A1 = 0.012 exp (-1.3Cs) and A2 = 2.1 - 0.60Cs + 0.036Cs2. At higher Sn, krn ≈ Sn4, independent of Cs. We present a pore-scale conceptual model that provides a phenomenological basis for the use of Cs as a predictor of krn at low Sn. We then present a number of simulated case studies that highlight the effect of these three-phase relative permeabilities on risk assessment or remediation design.
Estimation of Permeability from NMR Logs Based on Formation Classification Method in Tight Gas Sands
NASA Astrophysics Data System (ADS)
Wei, Deng-Feng; Liu, Xiao-Peng; Hu, Xiao-Xin; Xu, Rui; Zhu, Ling-Ling
2015-10-01
The Schlumberger Doll Research (SDR) model and cross plot of porosity versus permeability cannot be directly used in tight gas sands. In this study, the HFU approach is introduced to classify rocks, and determine the involved parameters in the SDR model. Based on the difference of FZI, 87 core samples, drilled from tight gas sandstones reservoirs of E basin in northwest China and applied for laboratory NMR measurements, were classified into three types, and the involved parameters in the SDR model are calibrated separately. Meanwhile, relationships of porosity versus permeability are also established. The statistical model is used to calculate consecutive FZI from conventional logs. Field examples illustrate that the calibrated SDR models are applicable in permeability estimation; models established from routine core analyzed results are effective in reservoirs with permeability lower than 0.3 mD, while the unified SDR model is only valid in reservoirs with permeability ranges from 0.1 to 0.3 mD.
NASA Astrophysics Data System (ADS)
Choi, J.; Keehm, Y.
2011-12-01
Permeability estimation in carbonate reservoirs is quite challenging since they are very heterogeneous. Moreover, the amount of core measurement data is commonly limited. In this paper, we present permeability maps for Grosmont formation in Canada with very limited permeability data, using bi-variated probability density function (porosity and permeability) conditioned to geological information. Grosmont formation consists of four units: Lower Grosmont (LG); Upper Grosmont (UG1); Upper Grosmont 2 (UG2); and Upper Grosmont 3 (UG3). From the previous studies, UG2 and UG3 are more promising reservoir units since they have larger porosity and permeability with vuggy pores and fractures by diagenesis (dolomitization and karstification). Thus, we applied our method to these two units. We first investigated core measurement data (porosity and permeability) and compared them to local geological aspects, such as the degree of diagenesis and vicinity of unconformity. Then we could divide the study area into 6 groups, and we established a bivariated probability density function (pdf) for each group and each unit (total of 12 pdfs) with core measurements of porosity and permeability. In the next step, we created porosity maps using well-log data for UG2 and UG3. The final step is to generate permeability maps for UG2 and UG3 by drawing a permeability value from the bivariated pdf conditioned to porosity. The final results show more realistic permeability maps for Grosmont formation when compared to conventional kriging results. Moreover, the strengths of this approach is (1) that it can use geological information and (2) that it can handle the variability of permeability, which can be naturally occurred in carbonate reservoirs. Acknowledgement: This work was supported by the Energy Resources R&D program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2008RER11P0430302009).
Paillet, Frederick L.
1988-01-01
Various conventional geophysical well logs were obtained in conjunction with acoustic tube-wave amplitude and experimental heat-pulse flowmeter measurements in two deep boreholes in granitic rocks on the Canadian shield in southeastern Manitoba. The objective of this study is the development of measurement techniques and data processing methods for characterization of rock volumes that might be suitable for hosting a nuclear waste repository. One borehole, WRA1, intersected several major fracture zones, and was suitable for testing quantitative permeability estimation methods. The other borehole, URL13, appeared to intersect almost no permeable fractures; it was suitable for testing methods for the characterization of rocks of very small permeability and uniform thermo-mechanical properties in a potential repository horizon. Epithermal neutron , acoustic transit time, and single-point resistance logs provided useful, qualitative indications of fractures in the extensively fractured borehole, WRA1. A single-point log indicates both weathering and the degree of opening of a fracture-borehole intersection. All logs indicate the large intervals of mechanically and geochemically uniform, unfractured granite below depths of 300 m in the relatively unfractured borehole, URL13. Some indications of minor fracturing were identified in that borehole, with one possible fracture at a depth of about 914 m, producing a major acoustic waveform anomaly. Comparison of acoustic tube-wave attenuation with models of tube-wave attenuation in infinite fractures of given aperture provide permeability estimates ranging from equivalent single-fractured apertures of less than 0.01 mm to apertures of > 0.5 mm. One possible fracture anomaly in borehole URL13 at a depth of about 914 m corresponds with a thin mafic dike on the core where unusually large acoustic contrast may have produced the observed waveform anomaly. No indications of naturally occurring flow existed in borehole URL13; however
Relative Permeabilities: a pore-level model study of the capillary number dependence
Ferer, M.V.; Mason, G.; Bromhal, G.S.; Smith, D.H.
2008-03-01
Relative permeabilities are widely used by the petroleum industry in reservoir simulations of recovery strategies. In recent years, pore level modeling has been used to determine relative permeabilities at zero capillary number for a variety of more and more realistic model porous media. Unfortunately, these studies cannot address the issue of the observed capillary number dependence of the relative permeabilities. Several years ago, we presented a method for determining the relative permeabilities from pore-level modeling at general capillary number. We have used this method to determine the relative permeabilities at several capillary numbers and stable viscosity ratios. In addition, we have determined these relative permeabilities using one of the standard dynamic methods for determining relative permeabilities from core flood experiments. Our results from the two methods are compared with each other and with experimental results.
The effects of viscous forces on three-phase relative permeability
Maloney, D.R.; Mahmood, S.M.; Honarpour, M.M.
1989-04-01
The overall objective of Three-Phase Relative Permeability Project (BE9) is to develop guidelines for improving the accuracy of three-phase relative permeability determinations. This report summarizes previous studies and explains the progress made at NIPER on studying the effect of variations in viscous forces on three-phase relative permeabilities by changing the viscosity of both wetting and nonwetting phases. Significant changes were observed due to viscosity variations. An increase in oil viscosity reduced the relative permeability to gas; an increase in brine/(wetting-phase) viscosity reduced the relative permeability to brine. A slight increase in gas relative permeability was also observed. These observations suggest that the viscosities of both oil and water influence three-phase permeability data. During this study, data scatter was sometimes encountered which was comparable to that of published results. The causes of this scatter are outlined in this report and remedial attempts are discussed. 20 refs., 16 figs., 5 tabs.
Permeability estimation from log-derived porosity II. Via co-kriging
Fang, Jen Ho; Pu, Zhi Wei . Dept. of Geology)
1993-03-01
In paper (I) (given at this meeting), the authors applied fuzzy regression to the problem of permeability estimation from porosity-log data. In this paper, they introduce another novel approach, co-kriging. Co-kriging is a multivariate geostatistical technique designed for characterizing joint spatial correlations between pairs of variables (log-derived porosity vs. core-derived permeability in the context of this paper). In other words, co-kriging yields estimates that use not only the information from direct measurements of the variables being estimated, but also the information from measurements of a second variable. Thus, co-kriging can be used to predict permeability at uncored wells. This is a powerful technique because they usually have more log data than core data. By making use of co-kriging they can make good use of the log-derived porosity data. Results of the study using the data from Chunchula field illustrate the power of this technique.
NASA Astrophysics Data System (ADS)
Jia, W.; Pan, F.; McPherson, B. J. O. L.
2015-12-01
Due to the presence of multiple phases in a given system, CO2 sequestration with enhanced oil recovery (CO2-EOR) includes complex multiphase flow processes compared to CO2 sequestration in deep saline aquifers (no hydrocarbons). Two of the most important factors are three-phase relative permeability and hysteresis effects, both of which are difficult to measure and are usually represented by numerical interpolation models. The purposes of this study included quantification of impacts of different three-phase relative permeability models and hysteresis models on CO2 sequestration simulation results, and associated quantitative estimation of uncertainty. Four three-phase relative permeability models and three hysteresis models were applied to a model of an active CO2-EOR site, the SACROC unit located in western Texas. To eliminate possible bias of deterministic parameters on the evaluation, a sequential Gaussian simulation technique was utilized to generate 50 realizations to describe heterogeneity of porosity and permeability, initially obtained from well logs and seismic survey data. Simulation results of forecasted pressure distributions and CO2 storage suggest that (1) the choice of three-phase relative permeability model and hysteresis model have noticeable impacts on CO2 sequestration simulation results; (2) influences of both factors are observed in all 50 realizations; and (3) the specific choice of hysteresis model appears to be somewhat more important relative to the choice of three-phase relative permeability model in terms of model uncertainty.
NASA Astrophysics Data System (ADS)
Chen, X.; Kianinejad, A.; DiCarlo, D. A.
2014-12-01
CO2-brine relative permeability relations are important parameters in modeling scenarios such as CO2 sequestration in saline aquifers and CO2 enhanced recovery in oil reservoir. Many steady-state experimental studies on CO2-brine relative permeability showed that the CO2-brine relative permeability differs greatly from typical oil-brine relative permeability. Particularly, they reported a very small endpoint CO2 relative permeability of 0.1~0.2 at a relative high residual water saturation of 0.4~0.6. In this study, we hypothesize the measured low endpoint CO2 relative permeability in previous studies was an experimental artifact that is primary due to low CO2 viscosity. We conducted steady-state CO2 drainage experiments by co-injecting equlibrated CO2 and brine into a long (60.8 cm) and low permeability (116-mD) Berea sandstone core at 20 °C and 1500 psi. During every experiment, both the overall pressure drop across the core and the pressure drops of the five independent and continuous sections of the core were monitored. The in-situ saturation was measured with a medical X-ray Computed Tomography (CT) scanner. In the center three sections where saturation was uniform, we determined the relative permeability to both brine and CO2 phases. In the entrance and exit sections, both measured pressure gradients and saturation were non-uniform. To cope with this, we make several self-consistent assumptions that reveal the nature of capillary entrance and effect in steady-state two-phase core flooding experiments. Based on these assumptions we determined the relative permeability to CO2 and CO2-brine capillary pressure simultaneously using measured pressure drops. We found: (1) a much higher endpoint CO2 relative permeability of 0.58 at a water saturation of 48%, (2) the entrance region with non-uniform saturation expanded CO2 relative permeability data to much lower water saturation, (3) the determined CO2-brine capillary pressure curve is self-consistent and matches
Experimental investigation the effect of nanoparticles on the oil-water relative permeability
NASA Astrophysics Data System (ADS)
Amedi, Hamidreza; Ahmadi, Mohammad-Ali
2016-05-01
This paper presents the effects of the nanosilica particles on the water and oil relative permeability curves at reservoir conditions. Real reservoir crude oil sample was employed as an oil phase in relative permeability measurements. In addition, real carbonate reservoir rock samples were employed as a porous media in core displacement experiments. To determine relative permeability curves, the unsteady-state approach was employed in which Toth et al. method was applied to the recovery data points. By increasing the nanosilica content of the aqueous phase the oil relative permeability increased while the residual oil saturation decreased; however, by increasing the nanosilica concentration in the aqueous solution the water relative permeability decreased. The outcomes of this paper can provide a better understanding regarding chemically enhanced oil recovery (EOR) by nanoparticles. Moreover, relative permeability curves help us in the history matching section of reservoir simulation for any further EOR scenarios.
A fast nonlinear regression method for estimating permeability in CT perfusion imaging
Bennink, Edwin; Riordan, Alan J; Horsch, Alexander D; Dankbaar, Jan Willem; Velthuis, Birgitta K; de Jong, Hugo W
2013-01-01
Blood–brain barrier damage, which can be quantified by measuring vascular permeability, is a potential predictor for hemorrhagic transformation in acute ischemic stroke. Permeability is commonly estimated by applying Patlak analysis to computed tomography (CT) perfusion data, but this method lacks precision. Applying more elaborate kinetic models by means of nonlinear regression (NLR) may improve precision, but is more time consuming and therefore less appropriate in an acute stroke setting. We propose a simplified NLR method that may be faster and still precise enough for clinical use. The aim of this study is to evaluate the reliability of in total 12 variations of Patlak analysis and NLR methods, including the simplified NLR method. Confidence intervals for the permeability estimates were evaluated using simulated CT attenuation–time curves with realistic noise, and clinical data from 20 patients. Although fixating the blood volume improved Patlak analysis, the NLR methods yielded significantly more reliable estimates, but took up to 12 × longer to calculate. The simplified NLR method was ∼4 × faster than other NLR methods, while maintaining the same confidence intervals (CIs). In conclusion, the simplified NLR method is a new, reliable way to estimate permeability in stroke, fast enough for clinical application in an acute stroke setting. PMID:23881247
Estimation of soil air permeability components at a laboratory-scale pilot.
Boudouch, Otmane; Esrael, Daoud; Kacem, Mariem; Benadda, Belkacem
2012-01-01
Soil air permeability is a key parameter in the design of soil vapour extraction. The purpose of this study is to verify the applicability of different analytical solutions, developed to determine soil characteristics in field conditions, to estimate soil air permeability in a small-scale pilot, since field testing may be expensive. A laboratory tridirectional pilot and a unidirectional column were designed in order to achieve the objectives of this work. Use of a steady-state unconfined analytical solution was found to be an appropriate method to determine soil air permeability components for the pilot conditions. Using pressure data collected under open, steady-state conditions, the average values of radial and vertical permeability were found to be, respectively, 9.97 x 10(-7) and 8.74 x 10(-7) cm2. The use of semi-confined analytical solutions may not be suitable to estimate soil parameters since a significant difference was observed between simulated and observed vacuums. Air permeability was underestimated when transient solutions were used, in comparison with methods based on steady-state solutions. The air radial and vertical permeability was found to be, respectively, 7.06 x 10(-7) and 4.93 x 10(-7) cm2, in the open scenario, and 2.30 x 10(-7) and 1.51 x 10(-7) cm2 in the semi-confined scenario. However, a good estimate of soil porosity was achieved using the two transient methods. The average values were predicted to be 0.482, in the open scenario, and 0.451 in the semi-confined scenario, which was in good agreement with the real value.
A probabilistic approach for estimating water permeability in pressure-driven membranes.
Boateng, Linkel K; Madarshahian, Ramin; Yoon, Yeomin; Caicedo, Juan M; Flora, Joseph R V
2016-08-01
A probabilistic approach is proposed to estimate water permeability in a cellulose triacetate (CTA) membrane. Water transport across the membrane is simulated in reverse osmosis mode by means of non-equilibrium molecular dynamics (MD) simulations. Different membrane configurations obtained by an annealing MD simulation are considered and simulation results are analyzed by using a hierarchical Bayesian model to obtain the permeability of the different membranes. The estimated membrane permeability is used to predict full-scale water flux by means of a process-level Monte Carlo simulation. Based on the results, the parameters of the model are observed to converge within 5-ns total simulation time. The results also indicate that the use of unique structural configurations in MD simulations is essential to capture realistic membrane properties at the molecular scale. Furthermore, the predicted full-scale water flux based on the estimated permeability is within the same order of magnitude of bench-scale experimental measurement of 1.72×10(-5) m/s. PMID:27444876
Estimating large-scale fracture permeability of unsaturatedrockusing barometric pressure data
Wu, Yu-Shu; Zhang, Keni; Liu, Hui-Hai
2005-05-17
We present a three-dimensional modeling study of gas flow inthe unsaturated fractured rock of Yucca Mountain. Our objective is toestimate large-scale fracture permeability, using the changes insubsurface pneumatic pressure in response to barometric pressure changesat the land surface. We incorporate the field-measured pneumatic datainto a multiphase flow model for describing the coupled processes ofliquid and gas flow under ambient geothermal conditions. Comparison offield-measured pneumatic data with model-predicted gas pressures is foundto be a powerful technique for estimating the fracture permeability ofthe unsaturated fractured rock, which is otherwise extremely difficult todetermine on the large scales of interest. In addition, this studydemonstrates that the multi-dimensional-flow effect on estimatedpermeability values is significant and should be included whendetermining fracture permeability in heterogeneous fracturedmedia.
NASA Astrophysics Data System (ADS)
GéRard-Marchant, P.; Angulo-Jaramillo, R.; Haverkamp, R.; Vauclin, M.; Groenevelt, P.; Elrick, D. E.
1997-06-01
The in situ determination of the field-saturated hydraulic conductivity of low-permeability porous materials is a major concern for both geotechnics and soil physics with regards to environmental protection or water resources management. Recent early-time single-ring infiltration experiments, involving sequential constant head and falling head conditions, allow its efficient estimation. Nevertheless, the theory on which the interpretation was based was still strictly valid to nondeformable soils and implicity relied on a particular form of the hydraulic conductivity-soil water pressure head relationship. This theory is now extended to deformable materials, without any restrictive hypothesis. A new concept, bulk sorptivity, which characterizes the solid phase movement, is introduced. Field experiments, conducted on two liners of swelling and slowly permeable materials, revealed that neglecting the soil deformation induces an underestimation of the actual coefficient of permeability of the soil.
NASA Astrophysics Data System (ADS)
Hwang, Sang Il; Lee, Kwang Pyo; Lee, Dong Soo; Powers, Susan E.
2006-02-01
Capillary pressure ( Pc)-saturation ( S)-relative permeability ( kr) relationships must be quantified to accurately predict non-aqueous phase liquid (NAPL) distribution in the subsurface. Several experimental techniques are presented here for two-fluid Pc- S- kr relationships for various saturation paths to better define the effect of fractional wettability on these relationships. During the primary drainage path of the Pc- S curves, the air-water system showed no distinct trend as a function of the fraction of sand treated by organosilane (S) to render it non-water wetting. In a NAPL-water system, however, a consistent decrease of capillary pressure with increase of the fraction of non-water wetting sands was observed. The much lower contact angle for air-water (a-w) system may result in the observed insensitivity of the a-w Pc- S curves to fractional wettability, at least for the PD pathway. For the main imbibition path of NAPL-water system, capillary pressure decreased as the fraction of the S component increased, requiring forced imbibition (negative capillary pressures) for a certain range of saturations. Systems with an increasing percentage of the S component also exhibited a higher water kr and lower NAPL or air kr at a given saturation for the primary drainage and main imbibition paths in both air-water and NAPL-water systems. The increase of water kr with increase of the fraction of the S component can be explained by the ability of water to occupy larger and highly conductive pores in such a system. Experimental kr- S data for the primary drainage path of NAPL-water system presented here were used to test the Bradford et al. [Bradford SA, Abriola LM, Leij FJ. Wettability effects on two- and three-fluid relative permeabilities. J Contam Hydrol 1997;28:171-91] model and the modified Mualem model for estimating the kr- S curves from measured Pc- S data as a function of fractional wettability. Both models predicted significantly less variation in the kr- S
NASA Astrophysics Data System (ADS)
Bolève, A.; Vandemeulebrouck, J.; Grangeon, J.
2012-11-01
In the present study, we propose the combination of two geophysical techniques, which we have applied to a dyke located in southeastern France that has a visible downstream flood area: the self-potential (SP) and hydro-acoustic methods. These methods are sensitive to two different types of signals: electric signals and water-soil pressure disturbances, respectively. The advantages of the SP technique lie in the high rate of data acquisition, which allows assessment of long dykes, and direct diagnosis in terms of leakage area delimitation and quantification. Coupled with punctual hydro-acoustic cartography, a leakage position can be precisely located, therefore allowing specific remediation decisions with regard to the results of the geophysical investigation. Here, the precise localization of leakage from an earth dyke has been identified using SP and hydro-acoustic signals, with the permeability of the preferential fluid flow area estimated by forward SP modeling. Moreover, we propose a general 'abacus' diagram for the estimation of hydraulic permeability of dyke leakage according to the magnitude of over water SP anomalies and the associated uncertainty.
The effect of saturation path on three-phase relative permeability
NASA Astrophysics Data System (ADS)
Kianinejad, Amir; Chen, Xiongyu; DiCarlo, David A.
2015-11-01
Simulation and fluid flow prediction of many petroleum-enhanced oil recovery methods as well as environmental processes such as carbon dioxide (CO2) geological storage or underground water resources remediation requires accurate modeling and determination of relative permeability under different saturation histories. Based on this critical need, several three-phase relative permeability models were developed to predict relative permeability; however, for practical purposes most of them require a variety of parameters introducing undesired complexity to the models. In this work, we attempt to find out if there is a simpler way to express this functionality. To do so, we experimentally measure three-phase, water/oil/gas, relative permeability in a 1 m long water-wet sand pack, under several saturation flow paths to cover the entire three-phase saturation space. We obtain the in situ saturations along the sand pack using a CT scanner and then determine the relative permeabilities of liquid phases directly from the measured in situ saturations using an unsteady state method. The measured data show that at a specific saturation, the oil relative permeability varies significantly (up to two orders of magnitude), depending on the path through saturation space. The three-phase relative permeability data are modeled using standard relative permeability models, Corey-type, and Saturation Weighted Interpolation (SWI). Our measured data suggest that three-phase oil relative permeability in water-wet media is only a function of its own saturation if the residual oil saturation is treated as a function of two saturations. We determine that residual saturation is the key parameter in modeling three-phase relative permeability (effect of saturation history).
Maloney, D.
1993-11-01
This report describes the results from special core analyses and relative permeability measurements conducted on Almond formation and Fontainebleu sandstone plugs. Almond formation plug tests were performed to evaluate multiphase, steady-state,reservoir-condition relative permeability measurement techniques and to examine the effect of temperature on relative permeability characteristics. Some conclusions from this project are as follows: An increase in temperature appeared to cause an increase in brine relative permeability results for an Almond formation plug compared to room temperature results. The plug was tested using steady-state oil/brine methods. The oil was a low-viscosity, isoparaffinic refined oil. Fontainebleu sandstone rock and fluid flow characteristics were measured and are reported. Most of the relative permeability versus saturation results could be represented by one of two trends -- either a k{sub rx} versus S{sub x} or k{sub rx} versus Sy trend where x and y are fluid phases (gas, oil, or brine). An oil/surfactant-brine steady-state relative permeability test was performed to examine changes in oil/brine relative permeability characteristics from changes in fluid IFTS. It appeared that, while low interfacial tension increased the aqueous phase relative permeability, it had no effect on the oil relative permeability. The BOAST simulator was modified for coreflood simulation. The simulator was useful for examining effects of variations in relative permeability and capillary pressure functions. Coreflood production monitoring and separator interface level measurement techniques were developed using X-ray absorption, weight methods, and RF admittance technologies. The three types of separators should be useful for routine and specialized core analysis applications.
Image-based relative permeability upscaling from the pore scale
NASA Astrophysics Data System (ADS)
Norouzi Apourvari, Saeid; Arns, Christoph H.
2016-09-01
High resolution images acquired from X-ray μ-CT are able to map the internal structure of porous media on which multiphase flow properties can be computed. While the resolution of a few micrometers may be sufficient for capturing the pore space of many sandstones, most carbonates exhibit a large amount of microporosity; pores which are below the image resolution and are not resolved at specific resolution. Neglecting the effect of micropores on fluid flow and transport properties of these rocks can cause erroneous results in particular at partial saturations. Current image-based pore scale models typically only consider macropores for simulating fluid flow. In this paper, we quantify the effect of microporosity on the effective permeability of the wetting phase for heterogeneous model structures with varying amount of micro-to-macro porosity. A multi-scale numerical approach is proposed to couple an average effect of micropores with an explicit representation of macropores. The Brinkman equation is solved using a lattice Boltzmann formulation to facilitate the coupling of Darcy and Stokes equations in micropores and macropores, respectively. The results show good agreement between the fine scale solution and the results of the upscaled models in which microporous regions are homogenised. The paper analyses in particular the choice of the momentum sink parameter at low wetting phase saturations. It is shown that this parameter can be found using either a flux-based calculation of permeability of microporous regions or chosen purely on the basis of the effective permeability of these regions.
Review: Mathematical expressions for estimating equivalent permeability of rock fracture networks
NASA Astrophysics Data System (ADS)
Liu, Richeng; Li, Bo; Jiang, Yujing; Huang, Na
2016-06-01
Fracture networks play a more significant role in conducting fluid flow and solute transport in fractured rock masses, comparing with that of the rock matrix. Accurate estimation of the permeability of fracture networks would help researchers and engineers better assess the performance of projects associated with fluid flow in fractured rock masses. This study provides a review of previous works that have focused on the estimation of equivalent permeability of two-dimensional (2-D) discrete fracture networks (DFNs) considering the influences of geometric properties of fractured rock masses. Mathematical expressions for the effects of nine important parameters that significantly impact on the equivalent permeability of DFNs are summarized, including (1) fracture-length distribution, (2) aperture distribution, (3) fracture surface roughness, (4) fracture dead-end, (5) number of intersections, (6) hydraulic gradient, (7) boundary stress, (8) anisotropy, and (9) scale. Recent developments of 3-D fracture networks are briefly reviewed to underline the importance of utilizing 3-D models in future research.
Effects of heterogeneities on capillary pressure-saturation-relative permeability relationships.
Ataie-Ashtiani, Behzad; Hassanizadeh, S Majid; Celia, Michael A
2002-06-01
In theories of multiphase flow through porous media, capillary pressure-saturation and relative permeability-saturation curves are assumed to be intrinsic properties of the medium. Moreover, relative permeability is assumed to be a scalar property. However, numerous theoretical and experimental works have shown that these basic assumptions may not be valid. For example, relative permeability is known to be affected by the flow velocity (or pressure gradient) at which the measurements are carried out. In this article, it is suggested that the nonuniqueness of capillary pressure-relative permeability-saturation relationships is due to the presence of microheterogeneities within a laboratory sample. In order to investigate this hypothesis, a large number of "numerical experiments" are carried out. A numerical multiphase flow model is used to simulate the procedures that are commonly used in the laboratory for the measurement of capillary pressure and relative permeability curves. The dimensions of the simulation domain are similar to those of a typical laboratory sample (a few centimeters in each direction). Various combinations of boundary conditions and soil heterogeneity are simulated and average capillary pressure, saturation, and relative permeability for the "soil sample" are obtained. It is found that the irreducible water saturation is a function of the capillary number; the smaller the capillary number, the larger the irreducible water saturation. Both drainage and imbibition capillary pressure curves are found to be strongly affected by heterogeneities and boundary conditions. Relative permeability is also found to be affected by the boundary conditions; this is especially true about the nonaqueous phase permeability. Our results reveal that there is much need for laboratory experiments aimed at investigating the interplay of boundary conditions and microheterogeneities and their effect on capillary pressure and relative permeability.
Chih-Ying Chen
2005-06-30
Two-phase flow through fractured media is important in petroleum, geothermal, and environmental applications. However, the actual physics and phenomena that occur inside fractures are poorly understood, and oversimplified relative permeability curves are commonly used in fractured reservoir simulations. In this work, an experimental apparatus equipped with a high-speed data acquisition system, real-time visualization, and automated image processing technology was constructed to study three transparent analog fractures with distinct surface roughnesses: smooth, homogeneously rough, and randomly rough. Air-water relative permeability measurements obtained in this study were compared with models suggested by earlier studies and analyzed by examining the flow structures. A method to evaluate the tortuosities induced by the blocking phase, namely the channel tortuosity, was proposed from observations of the flow structure images. The relationship between the coefficients of channel tortuosity and the relative permeabilities was studied with the aid of laboratory experiments and visualizations. Experimental data from these fractures were used to develop a broad approach for modeling two-phase flow behavior based on the flow structures. Finally, a general model deduced from these data was proposed to describe two-phase relative permeabilities in both smooth and rough fractures. For the theoretical analysis of liquid-vapor relative permeabilities, accounting for phase transformations, the inviscid bubble train models coupled with relative permeability concepts were developed. The phase transformation effects were evaluated by accounting for the molecular transport through liquid-vapor interfaces. For the steam water relative permeabilities, we conducted steam-water flow experiments in the same fractures as used for air-water experiments. We compared the flow behavior and relative permeability differences between two-phase flow with and without phase transformation effects
Obtaining permeability estimates from NMR logging data in an unconsolidated groundwater aquifer
NASA Astrophysics Data System (ADS)
Dlubac, K.; Knight, R. J.; Song, Y.; Bachman, N.; Grau, B.; Cannia, J. C.; Williams, J.
2011-12-01
There is growing interest in the use of proton nuclear magnetic resonance (NMR) logging for aquifer characterization because it provides information about water-filled porosity and pore space geometry that can be used to estimate permeability (k). Hydrologists estimate hydraulic conductivity, from which k can be calculated, using wellbore flow (WBF) logging. WBF logging data distributes the total hydraulic conductivity, determined from aquifer testing, throughout the aquifer. However, this method is time consuming and has relatively low vertical resolution. If reliable estimates of k can be obtained from NMR logging data, this would provide hydrologists with an efficient alternate method for characterizing aquifer properties. The Schlumberger Doll Research (SDR) and Timur-Coates (T-C) equations are widely used in petroleum applications to obtain k from NMR logging measurements of the relaxation time T2. In this abstract, we focus on the SDR equation which takes the form kSDR=aφ mT2MLn where a, m and n are empirical constants, T2ML is the mean log of the T2 distribution and φ is porosity. The constants have been empirically determined in consolidated materials and are typically assumed to have the following values: a=4, m=4 and n=2. The use of the SDR equation with these values has been found to yield reliable estimates of k in consolidated materials. However, this same equation underestimates k in unconsolidated materials. In this study, we collected NMR logging, aquifer-test, and WBF data from a 150-m deep well that penetrated the High Plains aquifer in central Nebraska. We then worked with a generalized form of the SDR equation: kSDR Generalized =aφ mT2AVG2, where we allowed T2AVG to be calculated as the mean log and arithmetic mean (T2AM) of the T2 distribution. We elected to set the exponent n on the T2 term equal to 2, which results in a k estimate that has the appropriate units of length squared. We used a semi-constrained least squares inversion to
Direct measurement of relative permeability in rocks from unsteady-state saturation profiles
NASA Astrophysics Data System (ADS)
Kianinejad, Amir; Chen, Xiongyu; DiCarlo, David A.
2016-08-01
We develop a method to measure liquid relative permeability in rocks directly from transient in situ saturation profiles during gravity drainage experiments. Previously, similar methods have been used for sandpacks; here, this method is extended to rocks by applying a slight overpressure of gas at the inlet. Relative permeabilities are obtained in a 60 cm long vertical Berea sandstone core during gravity drainage, directly from the measured unsteady-state in situ saturations along the core at different times. It is shown that for obtaining relative permeability using this method, if certain criteria are met, the capillary pressure of the rock can be neglected. However, it is essential to use a correct gas pressure gradient along the core. This involves incorporating the pressure drop at the outlet of the core due to capillary discontinuity effects. The method developed in this work obtains relative permeabilities in unsteady-state fashion over a wide range of saturations quickly and accurately.
Factors influencing unsteady relative permeability of a mixed-wet reservoir rock
Mohanty, K.K.; Miller, A.E. )
1991-09-01
Capillarity, viscous fingering, and heterogeneity influence the flow in a core plug and hence affect the relative permeability determined from an unsteady test. Several unsteady water/oil relative permeability tests were carried out in a mixed-wet core while in-situ 3D saturation distribution was monitored by a computerized-tomography (CT) scanner. Results illustrate included in this paper that, in the early part of the Johnson-Bossler-Naumann (JBN) method, relative permeability is dominated by fingering and heterogeneity effects. The later part of this method ({gt}1 PV), however, represents the relative permeability of the end-face saturation and is influenced by the capillary number and throughput. Thus, laboratory results must be scaled to the field on the basis of the flow parameters: end-effect, capillary, instability, and heterogeneity numbers.
NASA Astrophysics Data System (ADS)
Tichauer, Kenneth M.; Osswald, Christian R.; Dosmar, Emily; Guthrie, Micah J.; Hones, Logan; Sinha, Lagnojita; Xu, Xiaochun; Mieler, William F.; St. Lawrence, Keith; Kang-Mieler, Jennifer J.
2015-06-01
Clinical symptoms of diabetic retinopathy are not detectable until damage to the retina reaches an irreversible stage, at least by today's treatment standards. As a result, there is a push to develop new, "sub-clinical" methods of predicting the onset of diabetic retinopathy before the onset of irreversible damage. With diabetic retinopathy being associated with the accumulation of long-term mild damage to the retinal vasculature, retinal blood vessel permeability has been proposed as a key parameter for detecting preclinical stages of retinopathy. In this study, a kinetic modeling approach used to quantify vascular permeability in dynamic contrast-enhanced medical imaging was evaluated in noise simulations and then applied to retinal videoangiography data in a diabetic rat for the first time to determine the potential for this approach to be employed clinically as an early indicator of diabetic retinopathy. Experimental levels of noise were found to introduce errors of less than 15% in estimates of blood flow and extraction fraction (a marker of vascular permeability), and fitting of rat retinal fluorescein angiography data provided stable maps of both parameters.
Vasco, D.W.; Ferretti, Alessandro; Novali, Fabrizio
2008-05-01
Transient pressure variations within a reservoir can be treated as a propagating front and analyzed using an asymptotic formulation. From this perspective one can define a pressure 'arrival time' and formulate solutions along trajectories, in the manner of ray theory. We combine this methodology and a technique for mapping overburden deformation into reservoir volume change as a means to estimate reservoir flow properties, such as permeability. Given the entire 'travel time' or phase field, obtained from the deformation data, we can construct the trajectories directly, there-by linearizing the inverse problem. A numerical study indicates that, using this approach, we can infer large-scale variations in flow properties. In an application to Interferometric Synthetic Aperture (InSAR) observations associated with a CO{sub 2} injection at the Krechba field, Algeria, we image pressure propagation to the northwest. An inversion for flow properties indicates a linear trend of high permeability. The high permeability correlates with a northwest trending fault on the flank of the anticline which defines the field.
Kumar, Niyanta N; Gautam, Mohan; Lochhead, Jeffrey J; Wolak, Daniel J; Ithapu, Vamsi; Singh, Vikas; Thorne, Robert G
2016-01-01
Intranasal administration provides a non-invasive drug delivery route that has been proposed to target macromolecules either to the brain via direct extracellular cranial nerve-associated pathways or to the periphery via absorption into the systemic circulation. Delivering drugs to nasal regions that have lower vascular density and/or permeability may allow more drug to access the extracellular cranial nerve-associated pathways and therefore favor delivery to the brain. However, relative vascular permeabilities of the different nasal mucosal sites have not yet been reported. Here, we determined that the relative capillary permeability to hydrophilic macromolecule tracers is significantly greater in nasal respiratory regions than in olfactory regions. Mean capillary density in the nasal mucosa was also approximately 5-fold higher in nasal respiratory regions than in olfactory regions. Applying capillary pore theory and normalization to our permeability data yielded mean pore diameter estimates ranging from 13-17 nm for the nasal respiratory vasculature compared to <10 nm for the vasculature in olfactory regions. The results suggest lymphatic drainage for CNS immune responses may be favored in olfactory regions due to relatively lower clearance to the bloodstream. Lower blood clearance may also provide a reason to target the olfactory area for drug delivery to the brain. PMID:27558973
Kumar, Niyanta N.; Gautam, Mohan; Lochhead, Jeffrey J.; Wolak, Daniel J.; Ithapu, Vamsi; Singh, Vikas; Thorne, Robert G.
2016-01-01
Intranasal administration provides a non-invasive drug delivery route that has been proposed to target macromolecules either to the brain via direct extracellular cranial nerve-associated pathways or to the periphery via absorption into the systemic circulation. Delivering drugs to nasal regions that have lower vascular density and/or permeability may allow more drug to access the extracellular cranial nerve-associated pathways and therefore favor delivery to the brain. However, relative vascular permeabilities of the different nasal mucosal sites have not yet been reported. Here, we determined that the relative capillary permeability to hydrophilic macromolecule tracers is significantly greater in nasal respiratory regions than in olfactory regions. Mean capillary density in the nasal mucosa was also approximately 5-fold higher in nasal respiratory regions than in olfactory regions. Applying capillary pore theory and normalization to our permeability data yielded mean pore diameter estimates ranging from 13–17 nm for the nasal respiratory vasculature compared to <10 nm for the vasculature in olfactory regions. The results suggest lymphatic drainage for CNS immune responses may be favored in olfactory regions due to relatively lower clearance to the bloodstream. Lower blood clearance may also provide a reason to target the olfactory area for drug delivery to the brain. PMID:27558973
Special core analyses and relative permeability measurement on Almond formation reservoir rocks
Maloney, D.; Doggett, K.; Brinkmeyer, A.
1993-02-01
This report describes the results from special core analyses and relative permeability measurements conducted on samples of rock from the Almond Formation in Greater Green River Basin of southwestern Wyoming. The core was from Arch Unit Well 121 of Patrick Draw field. Samples were taken from the 4,950 to 4,965 ft depth interval. Thin section evaluation, X-ray diffraction, routine permeability and porosity, capillary pressure and wettability tests were performed to characterize the samples. Fluid flow capacity characteristics were measured during two-phase unsteady- and steady-state and three-phase steady-state relative permeability tests. Test results are presented in tables and graphs. Relative permeability results are compared with those of a 260-mD, fired Berea sandstone sample which was previously subjected to similar tests. Brine relative permeabilities were similar for the two samples, whereas oil and gas relative permeabilities for the Almond formation rock were higher at equivalent saturation conditions compared to Berea results. Most of the tests described in this report were conducted at 74[degrees]F laboratory temperature. Additional tests are planned at 150[degrees]F temperature. Equipment and procedural modifications to perform the elevated temperature tests are described.
Special core analyses and relative permeability measurement on Almond formation reservoir rocks
Maloney, D.; Doggett, K.; Brinkmeyer, A.
1993-02-01
This report describes the results from special core analyses and relative permeability measurements conducted on samples of rock from the Almond Formation in Greater Green River Basin of southwestern Wyoming. The core was from Arch Unit Well 121 of Patrick Draw field. Samples were taken from the 4,950 to 4,965 ft depth interval. Thin section evaluation, X-ray diffraction, routine permeability and porosity, capillary pressure and wettability tests were performed to characterize the samples. Fluid flow capacity characteristics were measured during two-phase unsteady- and steady-state and three-phase steady-state relative permeability tests. Test results are presented in tables and graphs. Relative permeability results are compared with those of a 260-mD, fired Berea sandstone sample which was previously subjected to similar tests. Brine relative permeabilities were similar for the two samples, whereas oil and gas relative permeabilities for the Almond formation rock were higher at equivalent saturation conditions compared to Berea results. Most of the tests described in this report were conducted at 74{degrees}F laboratory temperature. Additional tests are planned at 150{degrees}F temperature. Equipment and procedural modifications to perform the elevated temperature tests are described.
NASA Astrophysics Data System (ADS)
Zisser, N.; Kemna, A.; Nover, G.
2010-09-01
The possibility to estimate permeability from the electrical spectral induced polarization (SIP) response might be the most important benefit offered by SIP measurements. It can thus be deduced that, in the future, SIP measurements will be carried out more frequently at the field scale or in a well-logging context to estimate permeability. In the shallow subsurface, however, the temperature generally exhibits seasonal variability, and in the deeper subsurface, it usually increases with depth. Hence, knowledge about the dependence of the SIP response on temperature is necessary in order to avoid possible misinterpretation of datasets impacted by thermal effects. In our study, we present a semiempirical framework to describe the temperature dependence of the SIP response. We briefly introduce the SIP response and its relation to permeability in terms of an electrochemical polarization mechanism and combine this formulation with relationships for the dependence of ionic mobility on temperature. We compare the predictions of our formulation with the experimental data from SIP measurements performed on sandstone at temperatures from 0°C to 80°C. The measured SIP response was transformed into a relaxation time distribution, using the empirical Cole-Cole model and a regularized Debye decomposition procedure. The SIP response was found to be in good agreement with the theoretical model. The temperature dependence of both direct current conductivity and relaxation time is controlled mainly by the dependence of ionic mobility on temperature, and the shape of the relaxation time distribution of the investigated sandstone is almost independent of temperature. The temperature effect on the SIP response can therefore be easily corrected.
NASA Astrophysics Data System (ADS)
Ghanbarian, Behzad; Sahimi, Muhammad; Daigle, Hugh
2016-07-01
Accurate prediction of the relative permeability to water under partially saturated condition has broad applications and has been studied intensively since the 1940s by petroleum, chemical, and civil engineers, as well as hydrologists and soil scientists. Many models have been developed for this purpose, ranging from those that represent the pore space as a bundle of capillary tubes, to those that utilize complex networks of interconnected pore bodies and pore throats with various cross-section shapes. In this paper, we propose an approach based on the effective-medium approximation (EMA) and percolation theory in order to predict the water relative permeability. The approach is general and applicable to any type of porous media. We use the method to compute the water relative permeability in porous media whose pore-size distribution follows a power law. The EMA is invoked to predict the relative permeability from the fully saturated pore space to some intermediate water saturation that represents a crossover from the EMA to what we refer to as the "critical region." In the critical region below the crossover water saturation Swx, but still above the critical water saturation Swc (the residual saturation or the percolation threshold of the water phase), the universal power law predicted by percolation theory is used to compute the relative permeability. To evaluate the accuracy of the approach, data for 21 sets of undisturbed laboratory samples were selected from the UNSODA database. For 14 cases, the predicted relative permeabilities are in good agreement with the data. For the remaining seven samples, however, the theory underestimates the relative permeabilities. Some plausible sources of the discrepancy are discussed.
An Experimental Study of CO2-Brine Relative Permeability in Sandstone
NASA Astrophysics Data System (ADS)
Chen, X.; DiCarlo, D. A.
2013-12-01
Accurate determinations of CO2-brine relative permeability are important for modeling potential CO2 storage scenarios. The most common assumption is that CO2-brine relative permeability is likely to be similar to oil-brine relative permeability for water-wet rocks. But recent measurements of CO2-brine relative permeability have differed greatly from oil-brine relative permeability; particularly, the measurements show a very low CO2 end point relative permeability (kr,CO2=0.1~0.2) and a relatively high residual water saturation (Swr>0.4) ( Lee et al. 2010, Zuo et al. 2012, Akbarabadi et al. 2013 and etc.). It has been hypothesized that the differences are related to CO2-brine having a different contact angle from oil-brine. In this study, we hypothesize that the differences are caused by large capillary end effects resulted from the very low CO2 viscosity. We conduct steady-state CO2-brine flow experiments in 2-foot-long and 2.8-inch-diamter Berea sandstone cores at 20 °C and 1500 psi. Four pressure taps drilled on a core allow both the total pressure drop and that across five individual sections to be measured. Three experiments, two drainage and one imbibition, have been conducted so far. Our results show: (1) The relative permeability to both brine and CO2 of the last section (downstream, 15 cm long) is significantly smaller than that of any of the middle three sections. This testifies that the capillary end effect makes the relative permeability under-measured at the end of a core. (2) The values of the middle three sections are very close to each other, which indicate the middle part of our core is free of capillary end effect. (3) The CO2 end point relative permeability is 0.3~0.5, which is much higher than the recent measurements. (4) The brine end point relative permeability during imbibition is about 0.08, which is close to literature data. Reference: Lee, Y.S, Kim, K. H. and Lee, T.H. et al. Analysis of CO2 Endpoint Relative Permeability and Injectivity
Numerical-Simulation-Based Determination of Relative Permeability in Laminated Rocks
NASA Astrophysics Data System (ADS)
Sedaghat, Mohammad H.; Gerke, Kirill; Azizmohammadi, Siroos; Matthai, Stephan
2016-04-01
Reservoir simulation using the extended Darcy's law approach requires relative permeability curves derived either via analytic saturation functions (Corey models etc.) or from special core analysis (SCAL). Since such experimental exploration of the space of influential parameters (pore geometry and wettability) is costly and time consuming, establishing ways to extract ensemble relative permeability from numerical simulation, kri, over the entire range of water saturation is highly desirable. Recent work has highlighted that the shape of relative permeability strongly depends on the balance between viscous, gravitational, and capillary forces. Our work focuses on finding accurate ways to compute ensemble kri(sw) for layered rocks when both capillary and viscous forces are strong. Two methods are proposed: an unsteady state saturation variation (USSV) method and a steady state saturation variation (SSSV) technique. To evaluate these approaches, SCAL data was extracted numerically from a real mm-scale layered sample. Results obtained with a Finite Element-Centered Finite Volume (FECFM) simulator, suggest that either of the approaches work significantly better than conventional unsteady state and JBN (Johnson-Bossler-Naumann) methods. Also, investigating saturation and velocity profiles within the sample indicates that bed-by-bed variations in wettability influence the flow pattern along/across interfaces making equipermeable layers behave like zones with different flow velocity. This dramatically challenges conventional relative permeability models and is addressed in terms of a new variable called relative permeability index.
Liu, Qingjie; Shen, Pingping; Wu, Yu-Shu
2004-03-15
A dynamic pore-scale network model is presented for investigating the effects of interfacial tension and oil-water viscosity on relative permeability during chemical flooding. This model takes into account both viscous and capillary forces in analyzing the impact of chemical properties on flow behavior or displacement configuration, as opposed to the conventional or invasion percolation algorithm which incorporates capillary pressure only. The study results indicate that both water and oil relative-permeability curves are dependent strongly on interfacial tension as well as an oil-water viscosity ratio. In particular, water and oil relative-permeability curves are both found to shift upward as interfacial tension is reduced, and they both tend to become linear versus saturation once interfacial tension is at low values. In addition, the oil-water viscosity ratio appears to have only a small effect under conditions of high interfacial tension. When the interfacial tension is low, however, water relative permeability decreases more rapidly (with the increase in the aqueous-phase viscosity) than oil relative permeability. The breakthrough saturation of the aqueous phase during chemical flooding tends to decrease with the reduction of interfacial tension and may also be affected by the oil-water viscosity ratio.
Age-related changes in endothelial permeability and distribution volume of albumin in rat aorta.
Belmin, J; Corman, B; Merval, R; Tedgui, A
1993-03-01
Age-related changes in macromolecular transport across the arterial wall were investigated in 10-, 20-, and 30-mo-old WAG/Rij rats. Animals were injected with 125I- and 131I-labeled albumin, 90 and 5 min before they were killed, respectively. The transmural distribution of relative concentration of tracers in the aortic wall was obtained using en face serial sectioning technique. The apparent endothelial permeability to albumin calculated from the distribution of 5-min 131I-labeled albumin concentrations was significantly enhanced in 20- and 30-mo-old rats compared with 10-mo-old rats. The apparent distribution volume of albumin within the media, estimated as the mean medial 125I-labeled albumin concentration, was not significantly changed in 20-mo-old rats but was significantly decreased in the 30-mo-old animals. These age-related changes in the macromolecular transport suggest that the entry of plasma macromolecules in the aged arterial wall might be enhanced, whereas the efflux through the media may be impeded, possibly contributing to their trapping in the subendothelium. PMID:8456970
Flow visualization and relative permeability measurements in rough-walled fractures
Persoff, P.; Pruess, K.
1993-01-01
Two-phase (gas-liquid) flow experiments were done in a natural rock fracture and transparent replicas of natural fractures. Liquid was injected at constant volume flow rate, and gas was injected at either constant mass flow rate or constant pressure. When gas was injected at constant mass flow rate, the gas inlet pressure, and inlet and outlet capillary pressures, generally did not reach steady state but cycled irregularly. Flow visualization showed that this cycling was due to repeated blocking and unblocking of gas flow paths by liquid. Relative permeabilities calculated from flow rate and pressure data show that the sum of the relative permeabilities of the two phases is much less than 1, indicating that each phase interferes strongly with the flow of the other. Comparison of the relative permeability curves with typical curves for porous media (Corey curves) show that the phase interference is stronger in fractures than in typical porous media.
Water Retention Curve and Relative Permeability for Gas Production from Hydrate-Bearing Sediments
NASA Astrophysics Data System (ADS)
Mahabadi, N.; Dai, S.; Seol, Y.; Jang, J.
2014-12-01
Water retention curve (soil water characteristic curve SWCC) and relative permeability equations are important to determine gas and water production for gas hydrate development. However, experimental studies to determine fitting parameters of those equations are not available in the literature. The objective of this research is to obtain reliable parameters for capillary pressure functions and relative permeability equations applicable to hydrate dissociation and gas production. In order to achieve this goal, (1) micro X-ray Computer Tomography (CT) is used to scan the specimen under 10MPa effective stress, (2) a pore network model is extracted from the CT image, (3) hydrate dissociation and gas expansion are simulated in the pore network model, (4) the parameters for the van Genuchten-type soil water characteristic curve and relative permeability equation during gas expansion are suggested. The research outcome will enhance the ability of numerical simulators to predict gas and water production rate.
NASA Astrophysics Data System (ADS)
Popov, Evgeny; Popov, Yury; Spasennykh, Mikhail; Kozlova, Elena; Chekhonin, Evgeny; Zagranovskaya, Dzhuliya; Belenkaya, Irina; Alekseev, Aleksey
2016-04-01
A practical method of organic-rich intervals identifying within the low-permeable dispersive rocks based on thermal conductivity measurements along the core is presented. Non-destructive non-contact thermal core logging was performed with optical scanning technique on 4 685 full size core samples from 7 wells drilled in four low-permeable zones of the Bazhen formation (B.fm.) in the Western Siberia (Russia). The method employs continuous simultaneous measurements of rock anisotropy, volumetric heat capacity, thermal anisotropy coefficient and thermal heterogeneity factor along the cores allowing the high vertical resolution (of up to 1-2 mm). B.fm. rock matrix thermal conductivity was observed to be essentially stable within the range of 2.5-2.7 W/(m*K). However, stable matrix thermal conductivity along with the high thermal anisotropy coefficient is characteristic for B.fm. sediments due to the low rock porosity values. It is shown experimentally that thermal parameters measured relate linearly to organic richness rather than to porosity coefficient deviations. Thus, a new technique employing the transformation of the thermal conductivity profiles into continuous profiles of total organic carbon (TOC) values along the core was developed. Comparison of TOC values, estimated from the thermal conductivity values, with experimental pyrolytic TOC estimations of 665 samples from the cores using the Rock-Eval and HAWK instruments demonstrated high efficiency of the new technique for the organic rich intervals separation. The data obtained with the new technique are essential for the SR hydrocarbon generation potential, for basin and petroleum system modeling application, and estimation of hydrocarbon reserves. The method allows for the TOC richness to be accurately assessed using the thermal well logs. The research work was done with financial support of the Russian Ministry of Education and Science (unique identification number RFMEFI58114X0008).
Impacts of relative permeability on CO2 phase behavior, phase distribution, and trapping mechanisms
NASA Astrophysics Data System (ADS)
Moodie, N.; McPherson, B. J. O. L.; Pan, F.
2015-12-01
A critical aspect of geologic carbon storage, a carbon-emissions reduction method under extensive review and testing, is effective multiphase CO2 flow and transport simulation. Relative permeability is a flow parameter particularly critical for accurate forecasting of multiphase behavior of CO2 in the subsurface. The relative permeability relationship assumed and especially the irreducible saturation of the gas phase greatly impacts predicted CO2 trapping mechanisms and long-term plume migration behavior. A primary goal of this study was to evaluate the impact of relative permeability on efficacy of regional-scale CO2 sequestration models. To accomplish this we built a 2-D vertical cross-section of the San Rafael Swell area of East-central Utah. This model simulated injection of CO2 into a brine aquifer for 30 years. The well was then shut-in and the CO2 plume behavior monitored for another 970 years. We evaluated five different relative permeability relationships to quantify their relative impacts on forecasted flow results of the model, with all other parameters maintained uniform and constant. Results of this analysis suggest that CO2 plume movement and behavior are significantly dependent on the specific relative permeability formulation assigned, including the assumed irreducible saturation values of CO2 and brine. More specifically, different relative permeability relationships translate to significant differences in CO2 plume behavior and corresponding trapping mechanisms.
A study of relative permeability for steam-water flow in porous media
Ambusso, Willis; Satik, Cengiz; Horne, Roland
1996-01-24
We report on continuing experimental and numerical efforts to obtain steam-water relative permeability functions and to assess effect of heat transfer and phase change. To achieve these, two sets of steady-state flow experiments were conducted: one with nitrogen and water and another with steam and water. During these experiments, a mixture of nitrogen-water (or steam-water) was injected into a Berea sandstone core. At the onset of steady state conditions, three-dimensional saturation distributions were obtained by using a high resolution X-ray computer tomography scanner. By identifying a length of the core over which a flat saturation profile exists and measuring the pressure gradient associated with this length, we calculated relative permeabilities for nitrogen-water flow experiments. The relative permeability relations obtained in this case were in good agreement with those reported by other investigators. Another attempt was also made to conduct a steam-water flow experiment under adiabatic conditions. This experiment was completed with partial success due to the difficulties encountered during the experiment. The results of this experiment showed that a flat saturation profile actually developed over a substantial length of the core even at a comparatively modest injection rate (6 grams per minute) with low steam quality (4% by mass). The completion of this set of experiments should yield steam-water relative permeability relations in the near future.
Changes in pore geometry and relative permeability caused by carbonate precipitation in porous media
NASA Astrophysics Data System (ADS)
Jiang, Fei; Tsuji, Takeshi
2014-11-01
The C O2 behavior within the reservoirs of carbon capture and storage projects is usually predicted from large-scale simulations of the reservoir. A key parameter in reservoir simulation is relative permeability. However, mineral precipitation alters the pore structure over time, and leads correspondingly to permeability changing with time. In this study, we numerically investigate the influence of carbonate precipitation on relative permeability during C O2 storage. The pore spaces in rock samples were extracted by high-resolution microcomputed tomography (CT) scanned images. The fluid velocity field within the three-dimensional pore spaces was calculated by the lattice Boltzmann method, while reactive transport with calcite deposition was modeled by an advection-reaction formulation solved by the finite volume method. To increase the computational efficiency and reduce the processing time, we adopted a graphics processing unit parallel computing technique. The relative permeability of the sample rock was then calculated by a highly optimized two-phase lattice Boltzmann model. We also proposed two pore clogging models. In the first model, the clogging processes are modeled by transforming fluid nodes to solid nodes based on their precipitated mass level. In the second model, the porosity is artificially reduced by adjusting the gray scale threshold of the CT images. The developed method accurately simulates the mineralization process observed in laboratory experiment. Precipitation-induced evolution of pore structure significantly influenced the absolute permeability. The relative permeability, however, was much more influenced by pore reduction in the nonwetting phase than in the wetting phase. The output of the structural changes in pore geometry by this model could be input to C O2 reservoir simulators to investigate the outcome of sequestered C O2 .
Jiang, Fei; Tsuji, Takeshi
2014-11-01
The CO_{2} behavior within the reservoirs of carbon capture and storage projects is usually predicted from large-scale simulations of the reservoir. A key parameter in reservoir simulation is relative permeability. However, mineral precipitation alters the pore structure over time, and leads correspondingly to permeability changing with time. In this study, we numerically investigate the influence of carbonate precipitation on relative permeability during CO_{2} storage. The pore spaces in rock samples were extracted by high-resolution microcomputed tomography (CT) scanned images. The fluid velocity field within the three-dimensional pore spaces was calculated by the lattice Boltzmann method, while reactive transport with calcite deposition was modeled by an advection-reaction formulation solved by the finite volume method. To increase the computational efficiency and reduce the processing time, we adopted a graphics processing unit parallel computing technique. The relative permeability of the sample rock was then calculated by a highly optimized two-phase lattice Boltzmann model. We also proposed two pore clogging models. In the first model, the clogging processes are modeled by transforming fluid nodes to solid nodes based on their precipitated mass level. In the second model, the porosity is artificially reduced by adjusting the gray scale threshold of the CT images. The developed method accurately simulates the mineralization process observed in laboratory experiment. Precipitation-induced evolution of pore structure significantly influenced the absolute permeability. The relative permeability, however, was much more influenced by pore reduction in the nonwetting phase than in the wetting phase. The output of the structural changes in pore geometry by this model could be input to CO_{2} reservoir simulators to investigate the outcome of sequestered CO_{2}. PMID:25493903
Jiang, Fei; Tsuji, Takeshi
2014-11-01
The CO_{2} behavior within the reservoirs of carbon capture and storage projects is usually predicted from large-scale simulations of the reservoir. A key parameter in reservoir simulation is relative permeability. However, mineral precipitation alters the pore structure over time, and leads correspondingly to permeability changing with time. In this study, we numerically investigate the influence of carbonate precipitation on relative permeability during CO_{2} storage. The pore spaces in rock samples were extracted by high-resolution microcomputed tomography (CT) scanned images. The fluid velocity field within the three-dimensional pore spaces was calculated by the lattice Boltzmann method, while reactive transport with calcite deposition was modeled by an advection-reaction formulation solved by the finite volume method. To increase the computational efficiency and reduce the processing time, we adopted a graphics processing unit parallel computing technique. The relative permeability of the sample rock was then calculated by a highly optimized two-phase lattice Boltzmann model. We also proposed two pore clogging models. In the first model, the clogging processes are modeled by transforming fluid nodes to solid nodes based on their precipitated mass level. In the second model, the porosity is artificially reduced by adjusting the gray scale threshold of the CT images. The developed method accurately simulates the mineralization process observed in laboratory experiment. Precipitation-induced evolution of pore structure significantly influenced the absolute permeability. The relative permeability, however, was much more influenced by pore reduction in the nonwetting phase than in the wetting phase. The output of the structural changes in pore geometry by this model could be input to CO_{2} reservoir simulators to investigate the outcome of sequestered CO_{2}.
NASA Astrophysics Data System (ADS)
Ocarroll, D. M.; Polityka, C. A.; Phelan, T. J.; Abriola, L. M.
2003-04-01
Alhough it is commonly assumed that subsurface soils are completely water-wet, variations in wettability are likely in the contaminated subsurface. Dense nonaqueous phase liquids (DNAPLs) have often been released as part of acidic or basic mixtures containing surface active compounds. These mixtures can render subsurface soils intermediate to organic-wet. In addition natural soils have a variety of wetting characteristics. This works explores the effects of solid wettability on capillary pressure/saturation and relative permeability/saturation constitutive relationships for DNAPL/water systems. Tetrachloroethene (PCE) is used as a representative DNAPL in these experiments. A series of capillary pressure/saturation experiments and multistep column outflow experiments were conducted to estimate capillary retention and relative permeability functions for PCE in media with various wetting properties. Relative permeability/saturation parameters were quantified utilizing a multiphase flow simulator coupled with an inverse optimization routine. The optimization routine minimizes the square difference between experimental and simulated outflow by varying the constitutive parameters. Capillary pressure/saturation data, generated in small pressure cell experiments, facilitate independent verification of the retention functions fit to the multistep outflow experiments. Primary drainage, imbibition, and scanning curves are presented for water, intermediate and organic-wet F35/F50/F70/F110 sand. The utility of using Leverett scaling, in conjunction with independently measured contact angles, to scale primary drainage curves is assessed for these sands. Finally, results from the outflow experiments indicate that traditional capillary-based predictive models fail to capture observed relative permeability behavior at endpoint saturations.
NASA Astrophysics Data System (ADS)
Osterman, Gordon; Keating, Kristina; Binley, Andrew; Slater, Lee
2016-06-01
We estimate parameters from the Katz and Thompson permeability model using laboratory complex electrical conductivity (CC) and nuclear magnetic resonance (NMR) data to build permeability models parameterized with geophysical measurements. We use the Katz and Thompson model based on the characteristic hydraulic length scale, determined from mercury injection capillary pressure estimates of pore throat size, and the intrinsic formation factor, determined from multisalinity conductivity measurements, for this purpose. Two new permeability models are tested, one based on CC data and another that incorporates CC and NMR data. From measurements made on forty-five sandstone cores collected from fifteen different formations, we evaluate how well the CC relaxation time and the NMR transverse relaxation times compare to the characteristic hydraulic length scale and how well the formation factor estimated from CC parameters compares to the intrinsic formation factor. We find: (1) the NMR transverse relaxation time models the characteristic hydraulic length scale more accurately than the CC relaxation time (R2 of 0.69 and 0.33 and normalized root mean square errors (NRMSE) of 0.16 and 0.21, respectively); (2) the CC estimated formation factor is well correlated with the intrinsic formation factor (NRMSE=0.23). We demonstrate that that permeability estimates from the joint-NMR-CC model (NRMSE=0.13) compare favorably to estimates from the Katz and Thompson model (NRMSE=0.074). This model advances the capability of the Katz and Thompson model by employing parameters measureable in the field giving it the potential to more accurately estimate permeability using geophysical measurements than are currently possible.
Estimating permeability using median pore-throat radius obtained from mercury intrusion porosimetry
NASA Astrophysics Data System (ADS)
Gao, Zhiye; Hu, Qinhong
2013-04-01
Mercury intrusion porosimetry (MIP) has been widely used to characterize the pore structure for various types of porous media. Several relationships between permeability and pore structure information (e.g., porosity and pore-size distribution) have been developed in the literature. This work is to introduce a new, and simpler, empirical equation to predict permeability by solely using the median pore-throat radius (r50), which is the pore-throat radius corresponding to 50% mercury saturation. The total of 18 samples used in this work have a wide range of permeability, from 10-6 to 103 mD, which makes the new equation more applicable. The predicted permeabilities by using the new equation are comparable with permeability values obtained from other measurement methods, as shown from ten samples with permeability data measured with nitrogen.
NASA Astrophysics Data System (ADS)
Osterman, G. K.; Keating, K.; Binley, A. M.; Slater, L. D.; McDonald, R.
2014-12-01
In spite of the importance of permeability in controlling numerous hydrogeological and biogeochemical processes, the property can be exceptionally difficult to measure directly in the field. Recently, nuclear magnetic resonance (NMR) has become an increasingly popular method, both in the lab and the field, for hydrogeophysical investigations due to its sensitivity to water content and pore surface area. Additionally, previous work has shown that the electrical formation factor can be used as a proxy for the tortuosity of the pore space—a parameter NMR is incapable of detecting—in permeability models. However, the formation factor is impossible to accurately measure in the field using DC electrical methods, as the measured conductivity cannot be decomposed into the fluid and surface conduction components. Therefore, our approach is to use induced polarization (IP) and spectral induced polarization (SIP) in the laboratory to correct for the influence of surface conductivity in the formation factor calculation. The corrected formation factor can then be used along with NMR parameters for more accurate permeability estimation. Laboratory SIP and NMR datasets were acquired on 40 sandstone cores with a range of permeabilities spanning six orders of magnitude as estimated from gas permeameter measurements. We examine how different estimates of the electrical formation factor can be combined with the NMR transverse relaxation time to estimate permeability. Specifically, we compare the electrical formation factor measured at high and low pore-fluid salinity with the formation factor derived using IP and SIP. Using both empirical and mechanistic petrophysical relationships, we explore the utility of IP- and SIP-corrected formation factors in tandem with NMR parameters for permeability prediction as compared to the low-salinity formation factor typically measured in the field. Furthermore, we develop our models using IP and SIP data that may be acquired in the field
Connected pathway relative permeability from pore-scale imaging of imbibition
NASA Astrophysics Data System (ADS)
Berg, S.; Rücker, M.; Ott, H.; Georgiadis, A.; van der Linde, H.; Enzmann, F.; Kersten, M.; Armstrong, R. T.; de With, S.; Becker, J.; Wiegmann, A.
2016-04-01
Pore-scale images obtained from a synchrotron-based X-ray computed micro-tomography (μCT) imbibition experiment in sandstone rock were used to conduct Navier-Stokes flow simulations on the connected pathways of water and oil phases. The resulting relative permeability was compared with steady-state Darcy-scale imbibition experiments on 5 cm large twin samples from the same outcrop sandstone material. While the relative permeability curves display a large degree of similarity, the endpoint saturations for the μCT data are 10% in saturation units higher than the experimental data. However, the two datasets match well when normalizing to the mobile saturation range. The agreement is particularly good at low water saturations, where the oil is predominantly connected. Apart from different saturation endpoints, in this particular experiment where connected pathway flow dominates, the discrepancies between pore-scale connected pathway flow simulations and Darcy-scale steady-state data are minor overall and have very little impact on fractional flow. The results also indicate that if the pore-scale fluid distributions are available and the amount of disconnected non-wetting phase is low, quasi-static flow simulations may be sufficient to compute relative permeability. When pore-scale fluid distributions are not available, fluid distributions can be obtained from a morphological approach, which approximates capillary-dominated displacement. The relative permeability obtained from the morphological approach compare well to drainage steady state whereas major discrepancies to the imbibition steady-state experimental data are observed. The morphological approach does not represent the imbibition process very well and experimental data for the spatial arrangement of the phases are required. Presumably for modeling imbibition relative permeability an approach is needed that captures moving liquid-liquid interfaces, which requires viscous and capillary forces simultaneously.
Munkholm, P; Langholz, E; Hollander, D; Thornberg, K; Orholm, M; Katz, K D; Binder, V
1994-01-01
Increased intestinal permeability in patients with Crohn's disease and their first degree relatives has been proposed as an aetiological factor. The nine hour overnight urinary excretion of polyethyleneglycol-400 (PEG-400) and three inert sugars (lactulose, l-rhamnose, and mannitol) was used to test the permeation in 47 patients with Crohn's disease of whom 18 had at least one first degree relative with inflammatory bowel disease (2BD) and 52 patients with ulcerative colitis of whom 16 had at least one first degree relative with IBD. A total of 17 first degree relatives with IBD and 56 healthy first degree relatives were included. Thirty one healthy subjects not related to patients with IBD served as controls. No significant differences in PEG-400 permeation were found between the groups of patients, relatives, and controls, or between diseased and healthy relatives. The permeability to lactulose, rhamnose, and mannitol similarly did not differ between the three groups. This study challenges the previously reported findings of increased PEG-400 permeation in patients with Crohn's disease and in their healthy and diseased first degree relatives. There was no increase in permeability in a similar group of ulcerative colitis patients and their families. PMID:8307453
Schlueter, E.M.; Cook, N.G.W. |; Witherspoon, P.A.; Myer, L.R.
1994-04-01
Experiments to study relative permeabilities of a partially saturated rock have been carried out in Berea sandstone using fluids that can be solidified in place. The effective permeability of the spaces not occupied by the wetting fluid (paraffin wax) or the nonwetting fluid (Wood`s metal), have been measured at various saturations after solidifying each of the phases. The tests were conducted on Berea sandstone samples that had an absolute permeability of about 600 md. The shape of the laboratory-derived relative permeability vs. saturation curves measured with the other phase solidified conforms well with typical curves obtained using conventional experimental methods. The corresponding wetting and nonwetting fluid distributions at different saturations are presented and analyzed in light of the role of the pore structure in the invasion process, and their impact on relative permeability and capillary pressure. Irreducible wetting and nonwetting phase fluid distributions are studied. The effect of clay minerals on permeability is also assessed.
Quantifying Evaporation and Evaluating Runoff Estimation Methods in a Permeable Pavement System
The U.S. Environmental Protection Agency constructed a 0.4-ha parking lot in Edison, New Jersey, that incorporated permeable pavement in the parking lanes which were designed to receive run-on from the impervious hot-mix asphalt driving lanes. Twelve lined permeable pavement sec...
NASA Astrophysics Data System (ADS)
Lamorski, Krzysztof; Sławiński, Cezary; Barna, Gyöngyi
2014-05-01
There are some important macroscopic properties of the soil porous media such as: saturated permeability and water retention characteristics. These soil characteristics are very important as they determine soil transport processes and are commonly used as a parameters of general models of soil transport processes used extensively for scientific developments and engineering practise. These characteristics are usually measured or estimated using some statistical or phenomenological modelling, i.e. pedotransfer functions. On the physical basis, saturated soil permeability arises from physical transport processes occurring at the pore level. Current progress in modelling techniques, computational methods and X-ray micro-tomographic technology gives opportunity to use direct methods of physical modelling for pore level transport processes. Physically valid description of transport processes at micro-scale based on Navier-Stokes type modelling approach gives chance to recover macroscopic porous medium characteristics from micro-flow modelling. Water microflow transport processes occurring at the pore level are dependent on the microstructure of porous body and interactions between the fluid and the medium. In case of soils, i.e. the medium there exist relatively big pores in which water can move easily but also finer pores are present in which water transport processes are dominated by strong interactions between the medium and the fluid - full physical description of these phenomena is a challenge. Ten samples of different soils were scanned using X-ray computational microtomograph. The diameter of samples was 5 mm. The voxel resolution of CT scan was 2.5 µm. Resulting 3D soil samples images were used for reconstruction of the pore space for further modelling. 3D image threshholding was made to determine the soil grain surface. This surface was triangulated and used for computational mesh construction for the pore space. Numerical modelling of water flow through the
Design and development of an artificial neural network for estimation of formation permeability
Mohaghegh, S.; Arefi, R.; Ameri, S.; Rose, D.
1994-12-31
Permeability is one of the most important characteristics of hydrocarbon bearing formations. An accurate knowledge of permeability gives petroleum engineers a tool for efficiently managing the production processes of a field. It is also one of the most important pieces of information in the design and management of enhanced recovery operations. Formation permeability is often measured in the laboratory from cores or evaluated from well test data. Core analysis and well test data, however, are only available from a few wells in a field. On the other hand, almost all wells are logged. In this study an artificial neural network has been designed that is able to predict the permeability of the formations using the data provided by geophysical well logs with good accuracy. Artificial neural network, a biologically inspired computing method, with its ability to learn, self-adjust, and be trained provide a powerful tool to solve problems that involve pattern recognition. Using well logs to predict permeability has been attempted in the past. The problems with previous approaches were mainly two-fold, namely, the number of variables used (only one variable-porosity), and using regression analysis as the main tool for correlations. The approach introduced in this paper is an attempt to overcome these short comings. This is done, first, by using many variables from well logs that may provide information about the permeability. Second, by recognizing the existence of possible patterns between these variables and formation permeability using artificial neural networks. Neural nets are analog, inherently parallel and distributive systems. These characteristics, which will be discussed in the paper, are the main characteristics that enable artificial neural networks to be successful in predicting the permeability in rocks using well log information.
NASA Astrophysics Data System (ADS)
Daigle, H.; Rice, M. A.
2015-12-01
Relative permeabilities to water and gas are important parameters for accurate modeling of the formation of methane hydrate deposits and production of methane from hydrate reservoirs. Experimental measurements of gas and water permeability in the presence of hydrate are difficult to obtain. The few datasets that do exist suggest that relative permeability obeys a power law relationship with water or gas saturation with exponents ranging from around 2 to greater than 10. Critical path analysis and percolation theory provide a framework for interpreting the saturation-dependence of relative permeability based on percolation thresholds and the breadth of pore size distributions, which may be determined easily from 3-D images or gas adsorption-desorption hysteresis. We show that the exponent of the permeability-saturation relationship for relative permeability to water is related to the breadth of the pore size distribution, with broader pore size distributions corresponding to larger exponents. Relative permeability to water in well-sorted sediments with narrow pore size distributions, such as Berea sandstone or Toyoura sand, follows percolation scaling with an exponent of 2. On the other hand, pore-size distributions determined from argon adsorption measurements we performed on clays from the Nankai Trough suggest that relative permeability to water in fine-grained intervals may be characterized by exponents as large as 10 as determined from critical path analysis. We also show that relative permeability to the gas phase follows percolation scaling with a quadratic dependence on gas saturation, but the threshold gas saturation for percolation changes with hydrate saturation, which is an important consideration in systems in which both hydrate and gas are present, such as during production from a hydrate reservoir. Our work shows how measurements of pore size distributions from 3-D imaging or gas adsorption may be used to determine relative permeabilities.
Christiansen, R.L.; Kalbus, J.S.; Howarth, S.M.
1997-05-01
This report documents, demonstrates, evaluates, and provides theoretical justification for methods used to convert experimental data into relative permeability relationships. The report facilities accurate determination of relative permeabilities of anhydride rock samples from the Salado Formation at the Waste Isolation Pilot Plant (WIPP). Relative permeability characteristic curves are necessary for WIPP Performance Assessment (PA) predictions of the potential for flow of waste-generated gas from the repository and brine flow into repository. This report follows Christiansen and Howarth (1995), a comprehensive literature review of methods for measuring relative permeability. It focuses on unsteady-state experiments and describes five methods for obtaining relative permeability relationships from unsteady-state experiments. Unsteady-state experimental methods were recommended for relative permeability measurements of low-permeability anhydrite rock samples form the Salado Formation because these tests produce accurate relative permeability information and take significantly less time to complete than steady-state tests. Five methods for obtaining relative permeability relationships from unsteady-state experiments are described: the Welge method, the Johnson-Bossler-Naumann method, the Jones-Roszelle method, the Ramakrishnan-Cappiello method, and the Hagoort method. A summary, an example of the calculations, and a theoretical justification are provided for each of the five methods. Displacements in porous media are numerically simulated for the calculation examples. The simulated product data were processed using the methods, and the relative permeabilities obtained were compared with those input to the numerical model. A variety of operating conditions were simulated to show sensitivity of production behavior to rock-fluid properties.
Daigle, Hugh; Rice, Mary Anna; Daigle, Hugh
2015-12-14
Relative permeabilities to water and gas are important parameters for accurate modeling of the formation of methane hydrate deposits and production of methane from hydrate reservoirs. Experimental measurements of gas and water permeability in the presence of hydrate are difficult to obtain. The few datasets that do exist suggest that relative permeability obeys a power law relationship with water or gas saturation with exponents ranging from around 2 to greater than 10. Critical path analysis and percolation theory provide a framework for interpreting the saturation-dependence of relative permeability based on percolation thresholds and the breadth of pore size distributions, which may be determined easily from 3-D images or gas adsorption-desorption hysteresis. We show that the exponent of the permeability-saturation relationship for relative permeability to water is related to the breadth of the pore size distribution, with broader pore size distributions corresponding to larger exponents. Relative permeability to water in well-sorted sediments with narrow pore size distributions, such as Berea sandstone or Toyoura sand, follows percolation scaling with an exponent of 2. On the other hand, pore-size distributions determined from argon adsorption measurements we performed on clays from the Nankai Trough suggest that relative permeability to water in fine-grained intervals may be characterized by exponents as large as 10 as determined from critical path analysis. We also show that relative permeability to the gas phase follows percolation scaling with a quadratic dependence on gas saturation, but the threshold gas saturation for percolation changes with hydrate saturation, which is an important consideration in systems in which both hydrate and gas are present, such as during production from a hydrate reservoir. Our work shows how measurements of pore size distributions from 3-D imaging or gas adsorption may be used to determine relative permeabilities.
Flow Rate- and Fracture Property Dependence of Fracture-Matrix Ensemble Relative Permeability
NASA Astrophysics Data System (ADS)
Matthai, S. K.; Lang, P.; Bazrafkan, S.
2012-12-01
The grid-block scale ensemble relative permeability, kri of fractured porous rock with appreciable matrix permeability is of decisive interest to reservoir simulation and the prediction of production, injector-producer water breakthrough, and ultimate recovery. While the dynamic behaviour of naturally fractured reservoirs (NFR) already provides many clues about (pseudo) kri on the inter-well length scale, such data are difficult to interpret because, in the subsurface, the exact fracture geometry is unknown. Here we present numerical simulation results from discrete fracture and matrix (DFM) unstructured grid hybrid FEM-FVM simulation models, predicting the shape of fracture-matrix kri curves. In contrast to our earlier work, we also simulate capillary fracture matrix transfer (CFMT) and without relying the frequently made simplifying assumption that fracture saturation reflects fracture-matrix capillary pressure equilibrium. We also employ a novel discretization of saturation which permits jump discontinuities to develop across the fracture-matrix interface. This increased physical realism permits - for the first time - to test our earlier semi-analytical model of the flow rate dependence of relative permeability, ensuing from CFMT. The sensitivity analysis presented here constrains CMFT-related flow rate dependence of kri and illustrates how it manifests itself in two geometries of layer-restricted well-developed fracture patterns mapped in the field. We have also investigated the dependence of kri on fracture aperture as computed using discrete element analysis for plausible states of in situ stress. Our results indicate that fracture-matrix ensemble relative permeability can be matched with a new semi-analytic model taking into account the fracture-matrix flux ratio, the wetted fracture-matrix interface area as a function of saturation and the breakthrough saturation. However, we also detect a scale dependence of kri requiring a more elaborate treatment.
Two Phase Flow in Porous Media and the Concept of Relative Permeabilities
Eliasson, Jonas; Kjaran, Snorri Pall; Gunnarsson, Gestur
1980-12-16
New equations for the two phase flow of water and steam are presented. The new equations coincide with those already in use for the case of horizontal flow but are different from those for vertical flow. It is shown that the usual equations can only be valid when the two phases are flowing in separate channels, where the channel dimensions are large compared with the grain size of the porous media, and in such a case the relative permeabilities should vary only slightly with the saturation ratio. It is shown that the actual variation of relative permeabilities with saturation ratio suggests a flow model where the flow channel dimensions are of the same order of magnitude as the grain size. On this basis a new set of equations is proposed, which with the associated flow model explain relative permeabilities qualitatively. In addition they show that water can flow upwards in two phase flow where the pressure gradient is less than hydrostatic. In a simple two phase flow test it is demonstrated that this happens as predicted by the new equation set.
NASA Astrophysics Data System (ADS)
Lee, S. H.; Efendiev, Y.
2016-10-01
Three-phase flow in a reservoir model has been a major challenge in simulation studies due to slowly convergent iterations in Newton solution of nonlinear transport equations. In this paper, we examine the numerical characteristics of three-phase flow and propose a consistent, "C1-continuous discretization" (to be clarified later) of transport equations that ensures a convergent solution in finite difference approximation. First, we examine three-phase relative permeabilities that are critical in solving nonlinear transport equations. Three-phase relative permeabilities are difficult to measure in the laboratory, and they are often correlated with two-phase relative permeabilities (e.g., oil-gas and water-oil systems). Numerical convergence of non-linear transport equations entails that three-phase relative permeability correlations are a monotonically increasing function of the phase saturation and the consistency conditions of phase transitions are satisfied. The Modified Stone's Method II and the Linear Interpolation Method for three-phase relative permeability are closely examined for their mathematical properties. We show that the Linear Interpolation Method yields C1-continuous three-phase relative permeabilities for smooth solutions if the two phase relative permeabilities are monotonic and continuously differentiable. In the second part of the paper, we extend a Hybrid-Upwinding (HU) method of two-phase flow (Lee, Efendiev and Tchelepi, ADWR 82 (2015) 27-38) to three phase flow. In the HU method, the phase flux is divided into two parts based on the driving forces (in general, it can be divided into several parts): viscous and buoyancy. The viscous-driven and buoyancy-driven fluxes are upwinded differently. Specifically, the viscous flux, which is always co-current, is upwinded based on the direction of the total velocity. The pure buoyancy-induced flux is shown to be only dependent on saturation distributions and counter-current. In three-phase flow, the
Persoff, P.; Pruess, K.; Myer, L.
1991-01-01
Understanding and quantifying multi-phase flow in fractures is important for mathematical and numerical simulation of geothermal reservoirs, nuclear waste repositories, and petroleum reservoirs. While the cubic law for single-phase flow has been well established for parallel-plate fractures theoretically and experimentally, no reliable measurements of multi-phase flow in fractures have been reported. This work reports the design and fabrication of an apparatus for visualization of two-phase flow and for measurement of gas-liquid relative permeability in realistic rough-walled rock fractures. A transparent replica of a natural rock fracture from a core specimen is fabricated by molding and casting in clear epoxy. Simultaneous flow of gas and liquid with control of capillary pressure at inlet and outlet is achieved with the Hassler ''sandwich'' design: liquid is injected to the fracture through a porous block, while gas is injected directly to the edge of the fracture through channels in the porous block. A similar arrangement maintains capillary separation of the two phases at the outlet. Pressure drops in each phase across the fracture, and capillary pressures at the inlet and outlet, are controlled by means of pumps and needle valves, and are measured by differential and absolute pressure transducers. The clear epoxy cast of the natural fracture preserves the geometry of the fracture and permits visual observation of phase distributions. The fracture aperture distribution can be estimated by filling the fracture with a dyed liquid, and making pointwise measurements of the intensity of transmitted light. A set of two-phase flow experiments has been performed which has proven the viability of the basic experimental design, while also suggesting further improvements in the apparatus. Preliminary measurements are presented for single-phase permeability to liquid, and for relative permeabilities in simultaneous flow of liquid and gas.
Soderholm, J; Olaison, G; Lindberg, E; Hannestad, U; Vindels, A; Tysk, C; Jarnerot, G; Sjodahl, R
1999-01-01
Background—A familial defect in intestinal barrier function has been found in Crohn's disease. Aim—To investigate possible genetic and environmental influences on this barrier defect by studying intestinal permeability in both relatives and spouses of patients with Crohn's disease. Subjects—The study included 39 patients with Crohn's disease, 34 healthy first degree relatives, and 22 spouses. Twenty nine healthy volunteers served as controls. Methods—Intestinal permeability was assessed as the lactulose:mannitol ratio in five hour urinary excretion after oral load, both before (baseline) and after ingestion of acetylsalicylic acid. The permeability response represents the difference between the two tests. A ratio above the 95th percentile for controls was classified as abnormal. Results—Baseline permeability was higher in patients and spouses than in controls. An abnormal baseline permeability was seen in 36% of the patients, 23% of the spouses, 18% of the relatives, and 3% of the controls. After ingestion of acetylsalicylic acid, permeability increased significantly in all groups. Relatives were similar to patients with regard to permeability after exposure to acetylsalicylic acid, whereas spouses were similar to controls. The proportions with an abnormal permeability response to acetylsalicylic acid were 32% in patients, 14% in spouses, 41% in relatives, and 3% in controls. Conclusion—The findings suggest that baseline permeability is determined by environmental factors, whereas permeability provoked by acetylsalicylic acid is a function of the genetically determined state of the mucosal barrier, and support the notion that environmental and hereditary factors interact in the pathogenesis of Crohn's disease. Keywords: acetylsalicylic acid; environment; genetics; inflammatory bowel disease; lactulose; mannitol PMID:9862833
NASA Astrophysics Data System (ADS)
Jiang, Lanlan; Liu, Yu; Teng, Ying; Zhao, Jiafei; Zhang, Yi; Yang, Mingjun; Song, Yongchen
2016-03-01
The purpose of this work is to develop a permeability estimation method for porous media. This method is based on an improved capillary bundle model by introducing some pore geometries. We firstly carried out micro-CT scans to extract the 3D digital model of porous media. Then we applied a maximum ball extraction method to the digital model to obtain the topological and geometrical pore parameters such as the pore radius, the throat radius and length and the average coordination number. We also applied a random walker method to calculate the tortuosity factors of porous media. We improved the capillary bundle model by introducing the pore geometries and tortuosity factors. Finally, we calculated the absolute permeabilities of four kinds of porous media formed of glass beads and compared the results with experiments and several other models to verify the improved model. We found that the calculated permeabilities using this improved capillary bundle model show better agreement with the measured permeabilities than the other methods.
Studies on quantifying evaporation in permeable pavement systems are limited to few laboratory studies that used a scale to weigh evaporative losses and a field application with a tunnel-evaporation gauge. A primary objective of this research was to quantify evaporation for a la...
Sambandam, Satheesh; Parrondo, Javier; Ramani, Vijay
2013-09-28
The oxygen permeability of perfluorinated and hydrocarbon polymer electrolyte membranes (PEMs; Nafion®, SPEEK and SPSU), which are used as electrolytes and electrode ionomers in polymer electrolyte fuel cells (PEFCs), was estimated using chronoamperometry using a modified fuel cell set-up. A thin, cylindrical microelectrode was embedded into the PEM and used as the working electrode. The PEM was sandwiched between 2 gas diffusion electrodes, one of which was catalyzed and served as the counter and pseudo-reference electrode. Independently, from fuel cell experiments, the oxygen transport resistance arising due to transport through the ionomer film covering the catalyst active sites was estimated at the limiting current and decoupled from the overall mass transport resistance. The in situ oxygen permeability measured at 80 °C and 75% RH of perfluorinated ionomers such as Nafion® (3.85 × 10(12) mol cm(-1) s(-1)) was observed to be an order of magnitude higher than that of hydrocarbon-based PEMs such as SPEEK (0.27 × 10(12) mol cm(-1) s(-1)) and SPSU (0.15 × 10(12) mol cm(-1) s(-1)). The obtained oxygen transport (through ionomer film) resistance values (Nafion® - 1.6 s cm(-1), SPEEK - 2.2 s cm(-1) and SPSU - 3.0 s cm(-1); at 80 °C and 75% RH) correlated well with the measured oxygen permeabilities in these ion-containing polymers.
NASA Astrophysics Data System (ADS)
Hosa, Aleksandra; Curtis, Andrew; Wood, Rachel
2016-08-01
A common way to simulate fluid flow in porous media is to use Lattice Boltzmann (LB) methods. Permeability predictions from such flow simulations are controlled by parameters whose settings must be calibrated in order to produce realistic modelling results. Herein we focus on the simplest and most commonly used implementation of the LB method: the single-relaxation-time BGK model. A key parameter in the BGK model is the relaxation time τ which controls flow velocity and has a substantial influence on the permeability calculation. Currently there is no rigorous scheme to calibrate its value for models of real media. We show that the standard method of calibration, by matching the flow profile of the analytic Hagen-Poiseuille pipe-flow model, results in a BGK-LB model that is unable to accurately predict permeability even in simple realistic porous media (herein, Fontainebleau sandstone). In order to reconcile the differences between predicted permeability and experimental data, we propose a method to calibrate τ using an enhanced Transitional Markov Chain Monte Carlo method, which is suitable for parallel computer architectures. We also propose a porosity-dependent τ calibration that provides an excellent fit to experimental data and which creates an empirical model that can be used to choose τ for new samples of known porosity. Our Bayesian framework thus provides robust predictions of permeability of realistic porous media, herein demonstrated on the BGK-LB model, and should therefore replace the standard pipe-flow based methods of calibration for more complex media. The calibration methodology can also be extended to more advanced LB methods.
Larson, Judd; Kumar, Sendhil; Gale, S Adrian; Jain, Pradeep; Townsend, Timothy
2012-03-01
The measurement of vertical gas diffusivity and permeability of compacted municipal solid waste (MSW) using an analytical gas flow and transport model was evaluated. A series of pressure transducers were buried in a MSW landfill and in situ pressures were modelled using an algorithm that predicts soil-gas pressures based on field-measured barometric pressure data and vertical diffusivity. The vertical gas diffusivity that represented the best-fit of the measured pressures was estimated at 20 locations and ranged from 0.002 to 0.052 m2 s(-1). The vertical gas permeability ranged from 3.3 × 10(-14) to 4.5 × 10(-12) m2 for the upper-most 3 to 6 m of compacted MSW. The shortfalls of applying this method to landfill conditions are also discussed.
NASA Astrophysics Data System (ADS)
Hyun Jo, Dong; Lee, Rimi; Hyoung Kim, Jin; Oh Jun, Hyoung; Geol Lee, Tae; Hun Kim, Jeong
2015-06-01
Vascular integrity is important in maintaining homeostasis of brain microenvironments. In various brain diseases including Alzheimer’s disease, stroke, and multiple sclerosis, increased paracellular permeability due to breakdown of blood-brain barrier is linked with initiation and progression of pathological conditions. We developed a capacitance sensor array to monitor dielectric responses of cerebral endothelial cell monolayer, which could be utilized to evaluate the integrity of brain microvasculature. Our system measured real-time capacitance values which demonstrated frequency- and time-dependent variations. With the measurement of capacitance at the frequency of 100 Hz, we could differentiate the effects of vascular endothelial growth factor (VEGF), a representative permeability-inducing factor, on endothelial cells and quantitatively analyse the normalized values. Interestingly, we showed differential capacitance values according to the status of endothelial cell monolayer, confluent or sparse, evidencing that the integrity of monolayer was associated with capacitance values. Another notable feature was that we could evaluate the expression of molecules in samples in our system with the reference of real-time capacitance values. We suggest that this dielectric spectroscopy system could be successfully implanted as a novel in vitro assay in the investigation of the roles of paracellular permeability in various brain diseases.
NASA Astrophysics Data System (ADS)
Gomila, Rodrigo; Arancibia, Gloria; Nehler, Mathias; Bracke, Rolf; Stöckhert, Ferdinand
2016-04-01
Fault zones and their related structural permeability play a leading role in the migration of fluids through the continental crust. A first approximation to understanding the structural permeability conditions, and the estimation of its hydraulic properties (i.e. palaeopermeability and fracture porosity conditions) of the fault-related fracture mesh is the 2D analysis of its veinlets, usually made in thin-section. Those estimations are based in the geometrical parameters of the veinlets, such as average fracture density, length and aperture, which can be statistically modelled assuming penny-shaped fractures of constant radius and aperture within an anisotropic fracture system. Thus, this model is related to fracture connectivity, its length and to the cube of the fracture apertures. In this way, the estimated values presents their own inaccuracies owing to the method used. Therefore, the study of the real spatial distribution of the veinlets of the fault-related fracture mesh (3D), feasible with the use of micro-CT analyses, is a first order factor to unravel both, the real structural permeability conditions of a fault-zone, together with the validation of previous estimations made in 2D analyses in thin-sections. This early contribution shows the preliminary results of a fault-related fracture mesh and its 3D spatial distribution in the damage zone of the Jorgillo Fault (JF), an ancient subvertical left-lateral strike-slip fault exposed in the Atacama Fault System in northern Chile. The JF is a ca. 20 km long NNW-striking strike-slip fault with sinistral displacement of ca. 4 km. The methodology consisted of the drilling of vertically oriented plugs of 5 mm in diameter located at different distances from the JF core - damage zone boundary. Each specimen was, then, scanned with an x-ray micro-CT scanner (ProCon X-Ray CTalpha) in order to assess the fracture mesh. X-rays were generated in a transmission target x-ray tube with acceleration voltages ranging from 90
NASA Astrophysics Data System (ADS)
Peters, C. A.; Crandell, L. E.; Um, W.; Jones, K. W.; Lindquist, W. B.
2011-12-01
Geochemical reactions in the subsurface can alter the porosity and permeability of a porous medium through mineral precipitation and dissolution. While effects on porosity are relatively well understood, changes in permeability are more difficult to estimate. In this work, pore-network modeling is used to estimate the permeability of a porous medium using pore and throat size distributions. These distributions can be determined from 2D Scanning Electron Microscopy (SEM) images of thin sections or from 3D X-ray Computed Tomography (CT) images of small cores. Each method has unique advantages as well as unique sources of error. 3D CT imaging has the advantage of reconstructing a 3D pore network without the inherent geometry-based biases of 2D images but is limited by resolutions around 1 μm. 2D SEM imaging has the advantage of higher resolution, and the ability to examine sub-grain scale variations in porosity and mineralogy, but is limited by the small size of the sample of pores that are quantified. A pore network model was created to estimate flow permeability in a sand-packed experimental column investigating reaction of sediments with caustic radioactive tank wastes in the context of the Hanford, WA site. Before, periodically during, and after reaction, 3D images of the porous medium in the column were produced using the X2B beam line facility at the National Synchrotron Light Source (NSLS) at Brookhaven National Lab. These images were interpreted using 3DMA-Rock to characterize the pore and throat size distributions. After completion of the experiment, the column was sectioned and imaged using 2D SEM in backscattered electron mode. The 2D images were interpreted using erosion-dilation to estimate the pore and throat size distributions. A bias correction was determined by comparison with the 3D image data. A special image processing method was developed to infer the pore space before reaction by digitally removing the precipitate. The different sets of pore
Electrokinetic effects and fluid permeability
NASA Astrophysics Data System (ADS)
G. Berryman, James
2003-10-01
Fluid permeability of porous media depends mainly on connectivity of the pore space and two physical parameters: porosity and a pertinent length-scale parameter. Electrical imaging methods typically establish connectivity and directly measure electrical conductivity, which can then often be related to porosity by Archie's law. When electrical phase measurements are made in addition to the amplitude measurements, information about the pertinent length scale can then be obtained. Since fluid permeability controls the ability to flush unwanted fluid contaminants from the subsurface, inexpensive maps of permeability could improve planning strategies for remediation efforts. Detailed knowledge of fluid permeability is also important for oil field exploitation, where knowledge of permeability distribution in three dimensions is a common requirement for petroleum reservoir simulation and analysis, as well as for estimates on the economics of recovery.
Kelly, John R.; Kennedy, Paul J.; Cryan, John F.; Dinan, Timothy G.; Clarke, Gerard; Hyland, Niall P.
2015-01-01
The emerging links between our gut microbiome and the central nervous system (CNS) are regarded as a paradigm shift in neuroscience with possible implications for not only understanding the pathophysiology of stress-related psychiatric disorders, but also their treatment. Thus the gut microbiome and its influence on host barrier function is positioned to be a critical node within the brain-gut axis. Mounting preclinical evidence broadly suggests that the gut microbiota can modulate brain development, function and behavior by immune, endocrine and neural pathways of the brain-gut-microbiota axis. Detailed mechanistic insights explaining these specific interactions are currently underdeveloped. However, the concept that a “leaky gut” may facilitate communication between the microbiota and these key signaling pathways has gained traction. Deficits in intestinal permeability may underpin the chronic low-grade inflammation observed in disorders such as depression and the gut microbiome plays a critical role in regulating intestinal permeability. In this review we will discuss the possible role played by the gut microbiota in maintaining intestinal barrier function and the CNS consequences when it becomes disrupted. We will draw on both clinical and preclinical evidence to support this concept as well as the key features of the gut microbiota which are necessary for normal intestinal barrier function. PMID:26528128
Evaluating the relative air permeability of porous media from their water retention curves
NASA Astrophysics Data System (ADS)
Assouline, S.; Tuli, A.; Hopmans, J. W.
2016-05-01
Accurate modeling of water and air flow in porous media requires the definition of the relevant hydraulic properties, namely, the water retention curve (WRC) and the relative hydraulic conductivity function (RHC), as well as the definition of the relative air permeability function (RAP). Capitalizing on the approach developed previously to represent the RHC, a new model allowing the prediction of RAP based on information resulting from the WRC is proposed. The power value ηa in the model is a decreasing exponential function of the coefficient of variation, ɛ, characterizing the pore size distribution of the porous medium, and derived from its WRC. The model was calibrated using data from 22 disturbed and undisturbed soil samples and was validated using data from eight soil types ranging from quartz sand to silty clay loam. The proposed model provided accurate prediction of the soil RAP and performed in some cases (sandy loam and silty clay loam soils) better than available alternative models.
Papiernik, Sharon K; Yates, Scott R; Chellemi, Daniel O
2011-01-01
Minimizing atmospheric emissions of soil fumigants is critical for protecting human and environmental health. Covering the soil surface with a plastic tarp is a common approach to restrict fumigant emissions. The mass transfer of the fumigant vapors through the tarp is often the rate-limiting factor in fumigant emissions. An approach for standardizing measurements of film permeability is proposed that is based on determining the resistance (R) of films to diffusion of fumigants. Using this approach, values were determined for more than 200 film-chemical combinations under a range of temperature, relative humidity, and film handling conditions. Resistance to diffusion was specific for each fumigant/film combination, with the largest range of values observed for the fumigant chloropicrin. For each fumigant, decreased with increasing temperature. Changes in film permeability due to increases in temperature or field installation were generally less than a factor of five. For one film, values determined under conditions of very high relative humidity (approximately 100%) were at least 100 times lower than when humidity was very low (approximately 2%). This approach simplifies the selection of appropriate films for soil fumigation by providing rapid, reproducible, and precise measurements of their permeability to specific fumigants and application conditions.
NASA Astrophysics Data System (ADS)
Hale, V. Cody; McDonnell, Jeffrey J.
2016-02-01
The effect of bedrock permeability and underlying catchment boundaries on stream base flow mean transit time (MTT) and MTT scaling relationships in headwater catchments is poorly understood. Here we examine the effect of bedrock permeability on MTT and MTT scaling relations by comparing 15 nested research catchments in western Oregon; half within the HJ Andrews Experimental Forest and half at the site of the Alsea Watershed Study. The two sites share remarkably similar vegetation, topography, and climate and differ only in bedrock permeability (one poorly permeable volcanic rock and the other more permeable sandstone). We found longer MTTs in the catchments with more permeable fractured and weathered sandstone bedrock than in the catchments with tight, volcanic bedrock (on average, 6.2 versus 1.8 years, respectively). At the permeable bedrock site, 67% of the variance in MTT across catchments scales was explained by drainage area, with no significant correlation to topographic characteristics. The poorly permeable site had opposite scaling relations, where MTT showed no correlation to drainage area but the ratio of median flow path length to median flow path gradient explained 91% of the variance in MTT across seven catchment scales. Despite these differences, hydrometric analyses, including flow duration and recession analysis, and storm response analysis, show that the two sites share relatively indistinguishable hydrodynamic behavior. These results show that similar catchment forms and hydrologic regimes hide different subsurface routing, storage, and scaling behavior—a major issue if only hydrometric data are used to define hydrological similarity for assessing land use or climate change response.
Laura J. Pyrak-Nolte; Nicholas J. Giordano; David D. Nolte
2004-03-01
The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements of interfacial area per volume. This project on the experimental investigation of relative permeability upscaling has produced a unique combination of three quite different technical approaches to the upscaling problem of obtaining pore-related microscopic properties and using them to predict macroscopic behavior. Several important ''firsts'' have been achieved during the course of the project. (1) Optical coherence imaging, a laser-based ranging and imaging technique, has produced the first images of grain and pore structure up to 1 mm beneath the surface of the sandstone and in a laboratory borehole. (2) Woods metal injection has connected for the first time microscopic pore-scale geometric measurements with macroscopic saturation in real sandstone cores. (3) The micro-model technique has produced the first invertible relationship between saturation and capillary pressure--showing that interfacial area per volume (IAV) provides the linking parameter. IAV is a key element in upscaling theories, so this experimental finding may represent the most important result of this project, with wide ramifications for predictions of fluid behavior in porous media.
NASA Astrophysics Data System (ADS)
Boles, J. R.; Horner, S.
2003-12-01
Methane has leaked from the offshore South Ellwood fault at least since discovery of the South Ellwood field at Platform Holly. The fault bounds the north side of the field and has 600 meters of normal offset. The reservoir, which is fractured Monterey shale at one kilometer depth, was initially 5% over hydrostatic pressure, but is currently at 25% below hydrostatic pressure. Production fluid in well tubing that connects the platform and reservoir is isolated from the ocean. New data indicate that the ocean is in direct hydraulic communication with the reservoir in the vicinity of the fault. Quartz pressure sensors were installed at about one km depth in five wells during a 15 day production shut down. A well that intersects the fault at reservoir depth (about one km subsea), shows a pressure variation that matches the frequency of the ocean tide. Within +/- 1 minute, there is no lag between the predicted tide signal and the pressure variation in the well. The pressure change is less than predicted from sea heights, which we attribute to compressibility of the gas in the fault zone. The other wells (160m-1 km from the fault) do not show the tidal signal, indicating that pressure change is not a general effect of the tide on the earth's crust. During testing, fluid pressures increased at a rate of 55 Pa/hr (0.008 psi/hr) in the well adjacent to the fault. We conclude that the pressure recovery from sub-hydrostatic conditions is due to sea water flowing down the fault into the under pressured reservoir. From this data we calculate the permeability of the South Ellwood Fault to be about 20 md, a value similar to the overall field permeability in the fractured Monterey reservoir.
NASA Astrophysics Data System (ADS)
Reynolds, C. A.; Krevor, S.
2015-12-01
We provide a comprehensive experimental study of steady state, drainage relative permeability curves with CO2-brine and N2-deionized water, on a single Bentheimer sandstone core with a simple two-layer heterogeneity. We demonstrate that, if measured in the viscous limit, relative permeability is invariant with changing reservoir conditions, and is consistent with the continuum-scale multiphase flow theory for water wet systems. Furthermore, we show that under capillary limited conditions, the CO2-brine system is very sensitive to heterogeneity in capillary pressure, and by performing core floods under capillary limited conditions, we produce effective relative permeability curves that are flow rate and fluid parameter dependent. We suggest that the major uncertainty in past observations of CO2-brine relative permeability curves is due to the interaction of CO2 flow with pore space heterogeneity under capillary limited conditions and is not due to the effects of changing reservoir conditions. We show that the appropriate conditions for measuring intrinsic or effective relative permeability curves can be selected simply by scaling the driving force for flow by a quantification of capillary heterogeneity. Measuring one or two effective curves on a core with capillary heterogeneity that is representative of the reservoir will be sufficient for reservoir simulation.
Fairstein, Moran; Swissa, Rotem; Dahan, Arik
2013-04-01
Based on its lower Log P value relative to metoprolol, a marker for the low/high-permeability (P(eff)) class boundary, pseudoephedrine was provisionally classified as BCS low-permeability compound. On the other hand, following oral administration, pseudoephedrine fraction dose absorbed (F(abs)) and systemic bioavailability approaches 100%. This represents a challenge to the generally recognized P(eff)-F(abs) correlation. The purpose of this study was to elucidate the underlying mechanisms behind the confusion in pseudoephedrine's BCS classification. Pseudoephedrine's BCS solubility class was determined, and its physicochemical properties and intestinal permeability were thoroughly investigated, both in vitro and in vivo in rats, considering the complexity of the whole of the small intestine. Pseudoephedrine was found to be unequivocally a high-solubility compound. All of the permeability studies revealed similar phenomenon; at any given intestinal segment/pH, the permeability of metoprolol was higher than that of pseudoephedrine, however, as the intestinal region becomes progressively distal, and the pH gradually increases, pseudoephedrine's permeability rises above that of metoprolol in the former segment. This unique permeability pattern likely explains pseudoephedrine's complete absorption. In conclusion, pseudoephedrine is a BCS Class I compound; no discrepancy between P(eff) and F(abs) is involved in its absorption. Rather, it reflects the complexity behind P(eff) when considering the whole of the intestine. We propose to allow high-permeability classification to drugs with P(eff) that matches/exceeds the low/high class benchmark anywhere throughout the intestinal tract and not restricted necessarily to the jejunum.
System response as a function of relative permeability in geologic CO2 sequestration
NASA Astrophysics Data System (ADS)
Pollyea, R.
2015-12-01
Within the portfolio of risk assessment strategies for carbon capture and sequestration projects, numerical modeling and simulation is frequently utilized for predicting CO2 storage capacity, leakage potential, and geomechanical reservoir integrity. In numerical CO2 injection models, one commonly used approach for simulating the effects of relative permeability (krel) is to apply the van Genuchten (1980) model to the wetting phase and the Corey (1954) model to the non-wetting phase. In this formulation, wetting phase permeability decay is controlled by a phase interference parameter (m), and non-wetting phase permeability decay is controlled by irreducible non-wetting phase saturation (Sgr). Although krel is a well-known phenomenon, there exists much uncertainty in parameterizing krel models and little is known about the influence of parameter space on reservoir performance. This work presents results from a numerical modeling experiment designed to isolate the effects of variability in krel parameters, m and Sgr. A series of CO2 injection simulations is performed for 399 unique combinations of m and Sgr, which vary systematically over a range of 0.1 - 0.99 and 0.01 - 0.50, respectively. CO2 is injected at modest 2.78 kg/s for 10 years into a radially symmetric grid using a beta version of TOUGH3/ECO2N, and all reservoir properties remain constant across the ensemble of 399 simulations. Results from this work show the injection pressure response ranging from ~10 MPa to >60 MPa, where the high end of this range is focused on a narrow portion of the parameter space corresponding to m < 0.3 for all Sgr. Additionally, the maximum CO2 plume radius (defined as CO2 saturation > 0.01) ranges from 550 m to 1250 m, where the high end of this range corresponds with low m and low Sgr. Although the model geometry is quite simple, these results demonstrate enormous variability in the both injection pressure and CO2 plume dimension solely as a function of krel.
Uncertainty relation revisited from quantum estimation theory
Watanabe, Yu; Sagawa, Takahiro; Ueda, Masahito
2011-10-15
We use quantum estimation theory to formulate bounds of errors in quantum measurement for arbitrary quantum states and observables in a finite-dimensional Hilbert space. We prove that the measurement errors of two noncommuting observables satisfy Heisenberg-type uncertainty relation, find the achievable bound, and propose a strategy to achieve it.
NASA Astrophysics Data System (ADS)
Lipsey, Lindsay; Pluymaekers, Maarten; van Wees, Jan-Diederik; Limberger, Jon; Cloetingh, Sierd
2016-04-01
The presence of convective fluid flow in permeable layers can create zones of anomalously high temperature which can be exploited for geothermal energy. Temperature measurements from the Luttelgeest-01 (LTG-01) well in the northern onshore region of the Netherlands indicate variations in the thermal regime that could be indicative of convection. This thermal anomaly coincides with a 600 m interval (4600 - 5200 m) of Dinantian carbonates showing signs of increased fracture permeability of ~60 mD. For the purpose of geothermal energy exploration, it is of interest to know whether or not convection can occur in a particular reservoir, where convection cells are likely to develop and the temperature enhancements in convective upwellings. Three-dimensional numerical simulations provide insight on possible flow and thermal structures within the fractured carbonate interval. The development and number of convection cells is very much a time dependent process. First longitudinal rolls fill the domain, increasing in width until ultimately transforming into a more complex polyhedral structure. The model relaxes into a steady-state five-cell convection pattern. Furthermore, geometric aspects of the carbonate platform itself likely control the shape and location of upwellings. Convective upwellings can create significant temperature enhancements relative to the conductive profile and in agreement with the observations in the Luttelgeest carbonate platform. This enhancement is critically dependent on the aquifer thickness and geothermal gradient. Given a gradient of 39 °C/km and an aquifer thickness of 600 m, a temperature of 203 °C can be obtained at a depth of 4600 m directly above upwelling zones. Contrarily, downwelling zones result in a temperature of 185 °C at the same depth. This demonstrates the strong spatial variability of thermal anomalies in convective fractures aquifers at large depth, which can have a strong effect on exploration opportunity and risk of
Permeability of filter cakes of palm oil in relation to mechanical expression
Kamst, G.F.; Bruinsma, O.S.L.; Graauw, J. de
1997-03-01
Permeability and compressibility data are required for an adequate process model for compressible-cake filtration and mechanical expression. Experimental and modeling results of the permeability of palm-oil filter cakes (a highly compressible viscoelastic material) are combined with compressibility data, leading to a model for the expression step. Permeability measurements show that permeability depends strongly on the quantity of fine particles in the cake. Removal of fine particles from the slurry before expression significantly increases the solid-phase content during expression due to higher permeability. Modeling results of the expression step show that for palm-oil filter cakes there is a pressure above which the attainable mass fraction of solids becomes independent of pressure. Decrease in specific cake resistance has two effects: a higher mass fraction of solids at the same pressure and a higher pressure at which the mass fraction of solids is not affected further.
Berge, P A; Blair, S C; Shaffer, R J; Wang, H F
1997-02-18
We provide in this report a methodology to estimate bounds on the changes in fracture permeability due to thermal-mechanical processes associated with excavation of drifts and emplacement of waste. This report is the first milestone associated with Task A of the LLNL initiative to evaluate available methods for estimating chamges in fracture permeability surrounding drifts in the Exploratory Studies Facility (ESF) and the potential repository at Yucca Mountain in response to (1) construction-induced stress changes and (2) subsequent thermal pulse effects due to waste emplacement. These results are needed for modeling changes in repository-level moisture movement and seepage.
JiangTao Cheng; Ping Yu; William Headley; Nicholas Giordao; Mirela Mustata; Daiquan Chen; Nathan Cooper; David D. Nolte; Laura J. Pyrak-Nolte
2001-12-01
The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements of interfacial area per volume. During this reporting period, we have shown experimentally and theoretically that the optical coherence imaging system is optimized for sandstone. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures that are statistically similar to real porous media has shown the existence of a unique relationship among these hydraulic parameters. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, has the same length-scale as the values of IAV determined for the two-dimensional micro-models.
Laura J. Pyrak-Nolte; Ping Yu; JiangTao Cheng; Daiquan Chen; Nicholas Giordano; Mirela Mustata; John Coy; Nathan Cooper; David D. Nolte
2002-12-01
The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements of interfacial area per volume. During this reporting period, we have shown experimentally that the coherence detection can be performed in a borescope. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures has shown the existence of a unique relationship among these hydraulic parameters for different pore geometry. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, is essentially completed for imbibition conditions.
Persoff, P.; Pruess, K.; Myer, L.
1991-01-01
Understanding and quantifying multi-phase flow in fractures is important for mathematical and numerical simulation of geothermal reservoirs, nuclear waste repositories, and petroleum reservoirs. While the cubic law for single-phase flow has been well established for parallel-plate fractures theoretically and experimentally, no reliable measurements of multi-phase flow in fractures have been reported. This work reports the design and fabrication of an apparatus for visualization of two-phase flow and for measurement of gas-liquid relative permeability in realistic rough-walled rock fractures. A transparent replica of a natural rock fracture from a core specimen is fabricated by molding and casting in clear epoxy. Simultaneous flow of gas and liquid with control of capillary pressure at inlet and outlet is achieved with the Hassler sandwich'' design: liquid is injected to the fracture through a porous block, while gas is injected directly to the edge of the fracture through channels in the porous block. A similar arrangement maintains capillary separation of the two phases at the outlet. Pressure drops in each phase across the fracture, and capillary pressures at the inlet and outlet, are controlled by means of pumps and needle valves, and are measured by differential and absolute pressure transducers. The clear epoxy cast of the natural fracture preserves the geometry of the fracture and permits visual observation of phase distributions. The fracture aperture distribution can be estimated by filling the fracture with a dyed liquid, and making pointwise measurements of the intensity of transmitted light.
Factoring Algebraic Error for Relative Pose Estimation
Lindstrom, P; Duchaineau, M
2009-03-09
We address the problem of estimating the relative pose, i.e. translation and rotation, of two calibrated cameras from image point correspondences. Our approach is to factor the nonlinear algebraic pose error functional into translational and rotational components, and to optimize translation and rotation independently. This factorization admits subproblems that can be solved using direct methods with practical guarantees on global optimality. That is, for a given translation, the corresponding optimal rotation can directly be determined, and vice versa. We show that these subproblems are equivalent to computing the least eigenvector of second- and fourth-order symmetric tensors. When neither translation or rotation is known, alternating translation and rotation optimization leads to a simple, efficient, and robust algorithm for pose estimation that improves on the well-known 5- and 8-point methods.
Paillet, Frederick L.
1998-01-01
A numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high-resolution flowmeters. The model is designed to (1) precisely compute flow in a borehole, (2) approximate the effects of flow in surrounding aquifers on the measured borehole flow, (3) allow for an arbitrary number (N) of entry/exit points connected to M < N far-field aquifers, and (4) be consistent with the practical limitations of flowmeter measurements such as limits of resolution, typical measurement error, and finite measurement periods. The model is used in three modes: (1) a quasi-steady pumping mode where there is no ambient flow, (2) a steady flow mode where ambient differences in far-field water levels drive flow between fracture zones in the borehole, and (3) a cross-borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole. The model gives estimates of transmissivity for any number of fractures in steady or quasi-steady flow experiments that agree with straddle-packer test data. Field examples show how these cross-borehole-type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass.
Corticosterone mediates stress-related increased intestinal permeability in a region-specific manner
Zheng, Gen; Wu, Shu-Pei; Hu, Yongjun; Smith, David E; Wiley, John W.; Hong, Shuangsong
2012-01-01
Background Chronic psychological stress (CPS) is associated with increased intestinal epithelial permeability and visceral hyperalgesia. It is unknown whether corticosterone (CORT) plays a role in mediating alterations of epithelial permeability in response to CPS. Methods Male rats were subjected to 1-hour water avoidance (WA) stress or subcutaneous CORT injection daily for 10 consecutive days in the presence or absence of corticoid-receptor antagonist RU-486. The visceromotor response (VMR) to colorectal distension (CRD) was measured. The in situ single-pass intestinal perfusion was used to measure intestinal permeability in jejunum and colon simultaneously. Key Results We observed significant decreases in the levels of glucocorticoid receptor (GR) and tight junction proteins in the colon but not the jejunum in stressed rats. These changes were largely reproduced by serial CORT injections in control rats and were significantly reversed by RU-486. Stressed and CORT-injected rats demonstrated a 3-fold increase in permeability for PEG-400 (MW) in colon but not jejunum and significant increase in VMR to CRD, which was significantly reversed by RU-486. In addition, no differences in permeability to PEG-4,000 and PEG-35,000 were detected between control and WA groups. Conclusions & Inferences Our findings indicate that CPS was associated with region-specific decrease in epithelial tight junction protein levels in the colon, increased colon epithelial permeability to low-molecular weight macromolecules which were largely reproduced by CORT treatment in control rats and prevented by RU-486. These observations implicate a novel, region-specific role for CORT as a mediator of CPS-induced increased permeability to macromolecules across the colon epithelium. PMID:23336591
Max Magnitude of Induced Seismic Events Within CCS Projects, Related to the Permeability of Faults
NASA Astrophysics Data System (ADS)
Mazzoldi, A.; Rinaldi, A. P.; Rutqvist, J.
2011-12-01
The evaluation of the potential for induced seismicity and its effects on the surface is critical for public acceptance of geologic carbon sequestration. According to the Coulomb criterion, τ = C + μ (σn - p), seismic events can be induced by reactivation of existing faults due to enhancement in pore pressure (p) when the left-hand term (shear stress) of the equation is equal to or greater than the right-hand side (shear strength). However, large uncertainties exist in the values of in situ stress (σn) and fault properties; plus, faults may be below the detection limit and not identified prior to the start of a CO2 injection. In this study we discuss methods for bounding the earthquake magnitudes that could be induced during CO2 injection, focusing the attention on buried, undetectable faults (D < 10 m). We evaluate the maximum magnitude of a seismic event potentially due to a fault with these characteristics, theoretically, using empirical magnitude-versus-size formulas and allowing the whole fault plane to slip, and with the aid of a coupled multiphase fluid flow and geo-mechanical numerical model, for investigating the degree of conservatisms in the empirical approach. Faults can also act as preferential leaking paths, for brine and CO2, in a CCS reservoir. Permeability of fault planes during and after slip is a parameter that needs to be estimated in order to run computer-based simulations on the hydro-mechanical response of geological features to a pressure buildup due to a fluid injection. This parameter is variable and it can range between values orders of magnitude higher than the seal rocks, and comparable with this last. Both cases are present in nature: if on the one hand fluid flow through fractures and fault planes is the main path for water in intrusive rocks, on the other hand, over-pressurized porous reservoirs are easily found in sedimentary basins, bounded by growth-faults (Ref, ref). These last are known to be mechanically active, presenting
NASA Astrophysics Data System (ADS)
Jiang, F.
2015-12-01
Wettability is one of the most important factors influencing the multi-phase fluid flow behavior in porous media. However, the role of wettability at pore-scale still remains poorly understood. In this study, we carried out a series of pore-scale simulations of multiphase displacement process to investigate the impact of wettability heterogeneity on trapping, sweep efficiency and relative permeability using lattice Boltzmann method. We first artificially generated mixed-wet bead pack models with varying degree of wettability by introducing spatial heterogeneity. Based on these models, we then calculated the relative permeability curves and performed the drainage and imbibition simulations to obtain the residual non-wetting phase distributions. The results indicate that strong wettability heterogeneity results in a decrease of non-wetting phase permeability due to the pinned interfaces at wettability discontinuities. The wetting phase permeability as well as the sweep efficiency are largely influenced by the degree of wettability rather than the wettability heterogeneity. The non-wetting phase is observed to be less trapped with strong heterogeneity conditions.
Relation between first arrival time and permeability in self-affine fractures with areas in contact
NASA Astrophysics Data System (ADS)
Talon, L.; Auradou, H.; Hansen, A.
2012-03-01
We demonstrate that the first arrival times in dispersive processes in self-affine fractures are governed by the same length scale characterizing the fractures as that which controls their permeability. In one-dimensional channel flow this length scale is the aperture of the bottle neck, i.e., the region having the smallest aperture. In two dimensions, the concept of a bottle neck is generalized to that of a minimal path normal to the flow. The length scale is then the average aperture along this path. There is a linear relationship between the first arrival time and this length scale, even when there is strong overlap between the fracture surfaces creating areas with zero permeability. We express the first arrival time directly in terms of the permeability.
Field-scale estimation of gas permeability and subsequent computation of pore-gas velocity profiles are critical elements of sound soil venting design. It has been our experience however in U.S. EPA's technical assistance program, provided by the Office of Research and Developme...
Byrnes, Alan P.; Bhattacharya, Saibal; Victorine, John; Stalder, Ken
2007-09-30
Thin (3-40 ft thick), heterogeneous, limestone and dolomite reservoirs, deposited in shallow-shelf environments, represent a significant fraction of the reservoirs in the U.S. midcontinent and worldwide. In Kansas, reservoirs of the Arbuckle, Mississippian, and Lansing-Kansas City formations account for over 73% of the 6.3 BBO cumulative oil produced over the last century. For these reservoirs basic petrophysical properties (e.g., porosity, absolute permeability, capillary pressure, residual oil saturation to waterflood, resistivity, and relative permeability) vary significantly horizontally, vertically, and with scale of measurement. Many of these reservoirs produce from structures of less than 30-60 ft, and being located in the capillary pressure transition zone, exhibit vertically variable initial saturations and relative permeability properties. Rather than being simpler to model because of their small size, these reservoirs challenge characterization and simulation methodology and illustrate issues that are less apparent in larger reservoirs where transition zone effects are minor and most of the reservoir is at saturations near S{sub wirr}. These issues are further augmented by the presence of variable moldic porosity and possible intermediate to mixed wettability and the influence of these on capillary pressure and relative permeability. Understanding how capillary-pressure properties change with rock lithology and, in turn, within transition zones, and how relative permeability and residual oil saturation to waterflood change through the transition zone is critical to successful reservoir management and as advanced waterflood and improved and enhanced recovery methods are planned and implemented. Major aspects of the proposed study involve a series of tasks to measure data to reveal the nature of how wettability and drainage and imbibition oil-water relative permeability change with pore architecture and initial water saturation. Focus is placed on
NASA Astrophysics Data System (ADS)
Dadashpour, Mohsen; Echeverria Ciaurri, David; Mukerji, Tapan; Kleppe, Jon; Landrø, Martin
2010-12-01
In this study, we apply a derivative-free optimization algorithm to estimate porosity and permeability from time-lapse seismic data and production data from a real reservoir (Norne field). In some circumstances, obtaining gradient information (exact and/or approximate) can be problematic e.g. derivatives are not available from a commercial simulator, or results are needed within a very short time frame. Derivative-free optimization approaches can be very time consuming because they often require many simulations. Typically, one iteration roughly needs as many simulations as the number of optimization variables. In this work, we propose two ways to significantly increase the efficiency of an optimization methodology in model inversion problems. First, by principal component analysis we decrease the number of optimization variables while keeping geostatistical consistency, and second, noticing that some optimization methods are very amenable to being parallelized, we apply them within a distributed computing framework. If we combine all this, the model inversion approach can be robust, fairly efficient and very simple to implement. In this paper, we apply the methodology to two cases: a semi-synthetic model with noisy data, and a case based entirely on field data. The results show that the derivative-free approach presented is robust against noise in the data.
Dehoff, Karl J.; Oostrom, Martinus; Zhang, Changyong; Grate, Jay W.
2012-10-29
A series of displacement experiments was conducted using five wetting-nonwetting immiscible fluid pairs in a homogenous and uniform pore network. The micromodel was initially saturated with either polyethylene glycol 200 (PEG) or water as a wetting fluid, which was subsequently displaced by a nonwetting fluid (dodecane, hexadecane, or mineral oil) at different flow rates. The experiments were designed to allow determinations of nonwetting fluid relative permeabilities ( ), fluid saturations ( ), and capillary pressure heads ( ). In the displacements, nonwetting fluid saturations increased with increasing flow rates for all five fluid pairs, and viscous fingering, capillary fingering, and stable displacement were observed. Viscous fingering occurred when PEG was displaced by either dodecane or hexadecane. For the water displacements, capillary fingers were observed at low capillary numbers. Due to unstable fingering phenomena, values for the PEG displacements were smaller than for the water displacements. A fitting exercise using the Brooks-Corey (1964) relationship showed that the fitted entry pressure heads are reasonably close to the computed entry pressure head. The fitted pore geometry factor, S_{n} values for the displacements are considerably lower than what is expected for displacements in homogeneous, highly uniform, porous systems, demonstrating the impact of unstable displacement on the apparent value of S_{n}. It was shown that a continuum-based multiphase model could be used to predict the average behavior for wetting fluid drainage in a pore network as long as independently fitted - and - relations are used. The use of a coupled approach through the Brooks-Corey pore geometry factor underpredicts observed values.
Christiansen, R.L.; Howarth, S.M.
1995-08-01
This report documents a literature review of methods for measuring relative permeability as applied to low permeability anhydrite rock samples from the Salado Formation. About one hundred papers were reviewed, and four methods were identified as promising techniques for measuring the relative permeability of the Salado anhydrite: (1) the unsteady-state high-rate method, (2) the unsteady-state stationary-liquid method, (3) the unsteady-state centrifuge method, and (4) the unsteady-state low-rate method. Except for the centrifuge method, all have been used for low permeability rocks. The unsteady-state high-rate method is preferred for measuring relative permeability of Salado anhydrite, and the unsteady-state stationary-liquid method could be well suited for measuring gas relative permeability of Salado anhydrite. The unsteady-state low-rate method, which combines capillary pressure effects with relative permeability concepts may also prove effective. Likewise, the unsteady-state centrifuge method may be an efficient means for measuring brine relative permeability for Salado anhydrite, especially at high gas saturations.
Udegbunam, E.O.
1991-01-01
This paper presents a FORTRAN program for the determination of two-phase relative permeabilities from unsteady-state displacement data with capillary pressure terms included. The interpretative model employed in this program combines the simultaneous solution of a variant of the fractional flow equation which includes a capillary pressure term and an integro-differential equation derived from Darcy's law without assuming the simplified Buckley-Leverett flow. The incorporation of capillary pressure in the governing equations dispenses with the high flowrate experimental requirements normally employed to overcome capillarity effects. An illustrative example is presented herein which implements this program for the determination of oil/water relative permeabilities from a sandstone core sample. Results obtained compares favorably with results previously given in the literature. ?? 1991.
Persoff, P.; Pruess, K.; Petersen, L.P.
1995-01-01
Small sections (75 mm x 75 mm) of two natural rock fractures from outcrop boulders of Tiva Canyon tuff have been reproduced as transparent replicas. Aperture maps were drawn from images of the replicas filled with dye. Apertures were measured by the areas occupied by liquid drops of known volume. For both these fractures, the average aperture is about 350 {mu}m, while the hydraulic aperture is less (72 and 130 {mu}m). Two-phase (air-water) flow experiments have been conducted in these replicas to measure relative permeability and capillary pressures. The results obtained confirm the results of previous fracture experiments, and theoretical analysis, that the sum of relative permeabilities is much less than 1 at intermediate saturations. The welded tuffs in the vadose zone of Yucca Mountain, Nevada, are being investigated as the potential site of a geological repository for high-level nuclear wastes.
User's Guide for Hysteretic Capillary Pressure and Relative Permeability Functions in iTOUGH2
Doughty, C.A.
2009-08-01
The precursor of TOUGH2, TOUGH, was originally developed with non-hysteretic characteristic curves. Hysteretic capillary pressure functions were implemented in TOUGH in the late 1980s by Niemi and Bodvarsson (1988), and hysteretic capillary pressure and relative permeability functions were added to iTOUGH2 about ten years later by Finsterle et al. (1998). Recently, modifications were made to the iTOUGH2 hysteretic formulation to make it more robust and efficient (Doughty, 2007). Code development is still underway, with the ultimate goal being a hysteretic module that fits into the standard TOUGH2 (Pruess et al., 1991) framework. This document provides a user's guide for the most recent version of the hysteretic code, which runs within iTOUGH2 (Finsterle, 1999a,b,c). The current code differs only slightly from what was presented in Doughty (2007), hence that document provides the basic information on the processes being modeled and how they are conceptualized. This document focuses on a description of the user-specified parameters required to run hysteretic iTOUGH2. In the few instances where the conceptualization differs from that of Doughty (2007), the features described here are the current ones. Sample problems presented in this user's guide use the equation-of-state module ECO2N (Pruess, 2005). The components present in ECO2N are H{sub 2}O, NaCl, and CO{sub 2}. Two fluid phases and one solid phase are considered: an aqueous phase, which primarily consists of liquid H2O and may contain dissolved NaCl and CO{sub 2}; a supercritical phase which primarily consists of CO{sub 2}, but also includes a small amount of gaseous H{sub 2}O; and a solid phase consisting of precipitated NaCl. Details of the ECO2N formulation may be found in Pruess (2005). The aqueous phase is the wetting phase and is denoted ''liquid'', whereas the supercritical phase is the non-wetting phase and is denoted ''gas''. The hysteretic formalism may be applied to other iTOUGH2 equation
Estimating the severity of safety related behaviour.
Svensson, Ase; Hydén, Christer
2006-03-01
The aim of this work is to be a starting point for a more thorough description and analysis of safety related road user behaviour in order to better understand the different parts forming the traffic safety processes. The background is that it is problematic to use analysis of crash data and conflict data in the everyday traffic safety work due to low occurrence rates and the focus on rather exceptional and unsuccessful events. A new framework must consider the following aspects: (1) The importance of feedback to the road users. (2) Inclusion of more frequent events, "normal" road user behaviours and the possibility to link them to a severity dimension. (3) Prediction of safety/unsafety based on the more frequent events. By constructing severity hierarchies based on a uniform severity dimension (Time to Accident/Conflicting Speed value) it is possible to both describe the closeness to a crash and to get a comprehensive understanding of the connection between behaviour and safety by both considering unsuccessful and successful interactive situations. These severity hierarchies would make it possible to consider road users' expectations due to feedback and estimate its safety relevance.
NASA Astrophysics Data System (ADS)
Jang, Jaewon; Santamarina, J. Carlos
2014-01-01
Capillarity and both gas and water permeabilities change as a function of gas saturation. Typical trends established in the discipline of unsaturated soil behavior are used when simulating gas production from hydrate-bearing sediments. However, the evolution of gas saturation and water drainage in gas invasion (i.e., classical soil behavior) and gas nucleation (i.e., gas production) is inherently different: micromodel experimental results show that gas invasion forms a continuous flow path while gas nucleation forms isolated gas clusters. Complementary simulations conducted using tube networks explore the implications of the two different desaturation processes. In spite of their distinct morphological differences in fluid displacement, numerical results show that the computed capillarity-saturation curves are very similar in gas invasion and nucleation (the gas-water interface confronts similar pore throat size distribution in both cases); the relative water permeability trends are similar (the mean free path for water flow is not affected by the topology of the gas phase); and the relative gas permeability is slightly lower in nucleation (delayed percolation of initially isolated gas-filled pores that do not contribute to gas conductivity). Models developed for unsaturated sediments can be used for reservoir simulation in the context of gas production from hydrate-bearing sediments, with minor adjustments to accommodate a lower gas invasion pressure Po and a higher gas percolation threshold.
Relating damage evolution of concrete cooled to cryogenic temperatures to permeability
NASA Astrophysics Data System (ADS)
Kogbara, Reginald B.; Iyengar, Srinath R.; Grasley, Zachary C.; Rahman, Syeda; Masad, Eyad A.; Zollinger, Dan G.
2014-11-01
Typically, 9% Ni steel is used for primary containment of liquefied natural gas (LNG). Utilization of concrete in place of 9% Ni steel for primary containment would lead to significant cost savings. Hence, this study investigates changes in the microstructure of concrete due to cryogenic freezing that would affect its relevant engineering properties for containment. The study also evaluates the effect of aggregate type on the damage potential of concrete subjected to cryogenic freezing. The aim is to investigate design methodologies to produce damage-resistant cryogenic concrete. The study employed four concrete mixture designs involving river sand as fine aggregate, and coarse aggregates with different coefficient of thermal expansion (CTE) values. Specifically, the coarse aggregates were limestone, sandstone, trap rock and lightweight aggregate. Concrete cubes were cured under water for at least 28 days and thereafter frozen from ambient (20 °C) to cryogenic temperature (-165 °C). Acoustic emission (AE) sensors were placed on the concrete cubes during freezing. X-ray computed tomography (XRCT) was employed to study the microstructure of concrete cores, before and after cryogenic freezing. The impact of the microstructural evolution thus obtained from AE and XRCT on relevant engineering properties was determined via water and chloride permeability tests. Microcrack propagation determined from AE correlated with changes in permeability. There were no observable cracks in majority of the concrete mixtures after freezing. This implies that microcracks detected via AE and increased permeability was very well distributed and smaller than the XRCT's resolution. Damage (microcracking) resistance of the concrete with different aggregates was in the order limestone ⩾ trap rock ≫ lightweight aggregate ⩾ sandstone.
Oláh, Gáspár; Herédi, Judit; Menyhárt, Ákos; Czinege, Zsolt; Nagy, Dávid; Fuzik, János; Kocsis, Kitti; Knapp, Levente; Krucsó, Erika; Gellért, Levente; Kis, Zsolt; Farkas, Tamás; Fülöp, Ferenc; Párdutz, Árpád; Tajti, János; Vécsei, László; Toldi, József
2013-01-01
Cortical spreading depression (CSD) involves a slowly-propagating depolarization wave in the cortex, which can appear in numerous pathophysiological conditions, such as migraine with aura, stroke, and traumatic brain injury. Neurons and glial cells are also depolarized transiently during the phenomena. CSD is followed by a massive increase in glutamate release and by changes in the brain microcirculation. The aim of this study was to investigate the effects of two N-methyl-D-aspartate receptor antagonists, endogenous kynurenic acid (KYNA) and dizocilpine, on CSD and the related blood–brain barrier (BBB) permeability in rats. In intact animals, KYNA hardly crosses the BBB but has some positive features as compared with its precursor L-Kynurenine, which is frequently used in animal studies (KYNA cannot be metabolized to excitotoxic agents such as 3-hydroxy-L-kynurenine and quinolinic acid). We therefore investigated the possible effects of peripherally administered KYNA. Repetitive CSD waves were elicited by the application of 1 M KCl solution to the cortex. Direct current-electrocorticograms were measured for 1 hour. Four parameters of the waves were compared. Evans blue dye and fluorescent microscopy were used to study the possible changes in the permeability of the BBB. The results demonstrated that N-methyl-D-aspartate receptor antagonists can reduce the number of CSD waves and decrease the permeability of the BBB during CSD. These results suggest that KYNA itself or its derivatives may offer a new approach in the therapy of migraines. PMID:24068867
Cancer Related-Knowledge - Small Area Estimates
These model-based estimates are produced using statistical models that combine data from the Health Information National Trends Survey, and auxiliary variables obtained from relevant sources and borrow strength from other areas with similar characteristics.
Malykh, O V; Golub, A Yu; Teplyakov, V V
2011-05-11
Membrane gas separation technologies (air separation, hydrogen recovery from dehydrogenation processes, etc.) use traditionally the glassy polymer membranes with dominating permeability of "small" gas molecules. For this purposes the membranes based on the low free volume glassy polymers (e.g., polysulfone, tetrabromopolycarbonate and polyimides) are used. On the other hand, an application of membrane methods for VOCs and some toxic gas recovery from air, separation of the lower hydrocarbons containing mixtures (in petrochemistry and oil refining) needs the membranes with preferable penetration of components with relatively larger molecular sizes. In general, this kind of permeability is characterized for rubbers and for the high free volume glassy polymers. Data files accumulated (more than 1500 polymeric materials) represent the region of parameters "inside" of these "boundaries." Two main approaches to the prediction of gas permeability of polymers are considered in this paper: (1) the statistical treatment of published transport parameters of polymers and (2) the prediction using model of ≪diffusion jump≫ with consideration of the key properties of the diffusing molecule and polymeric matrix. In the frames of (1) the paper presents N-dimensional methods of the gas permeability estimation of polymers using the correlations "selectivity/permeability." It is found that the optimal accuracy of prediction is provided at n=4. In the frames of the solution-diffusion mechanism (2) the key properties include the effective molecular cross-section of penetrating species to be responsible for molecular transportation in polymeric matrix and the well known force constant (ε/k)(eff i) of {6-12} potential for gas-gas interaction. Set of corrected effective molecular cross-section of penetrant including noble gases (He, Ne, Ar, Kr, Xe), permanent gases (H(2), O(2), N(2), CO), ballast and toxic gases (CO(2), NO(,) NO(2), SO(2), H(2)S) and linear lower hydrocarbons (CH(4
Lin, Shingjong.
1989-01-01
To test the hypothesis that transiently open junctions around the endothelial cells undergoing turnover are the large pores through which macromolecules (with the size of albumin or larger) cross the endothelium in large arteries, experiments were performed on Sprague-Dawley, spontaneously hypertensive (SHR), and Wistar-Kyoto (WKY) rats under anesthesia. Endothelial macromolecular permeability was studied in both en face and cross-sectional preparations of the thoracic aorta by using fluorescence-labeled albumin and low density lipoprotein (LDL). Foci of macromolecular leakage in the aorta were visualized and mapped with fluorescence microscopy. Replicating endothelial cells were identified by {sup 3}H-thymidine autoradiography and hemotoxylin staining, and dead endothelia cells were detected by IgG immunocytochemistry. The occurrence of cell replication or death was correlated with macromolecular leakage in the aorta. Under the fluorescence microscope, endothelial macromolecular leakage was clearly identified as discrete spots or larger foci. Both the number density and the size of tracer leaky foci increased with time. A higher number density of leaky foci was found in branching areas. A high degree of correlation was found between macromolecular permeability and endothelial cell mitosis or death at the cellular level. A significantly higher density of tracer leaky foci was noted in SHR than in WKY, which was accompanied by greater frequencies of both endothelial cell mitosis and death. During cell turnover, aortic endothelial cells continuously undergo structural remodeling, including cell junctions. Poorly organized clefts associated with the remodeling provide the pathway through which macromolecules enter the arterial wall.
Li, Xiaolong; Lu, Yan; Sun, Yi; Zhang, Qi
2015-01-01
Objective: Our objective is to explore the effect of curcumin on permeability of coronary artery and expression of related proteins in rat coronary atherosclerosis heart disease model. Methods: 45 healthy male Wistar rats of clean grade were selected and divided into treatment group, model control group and blank control group. The rats in the treatment group and model control group received high-fat diet for 12 weeks and intraperitoneal injection of VD3 to establish rat coronary atherosclerosis heart disease model. After modeling, the rats in the treatment group received gavage of 100 mg/(kg·d) curcimin, and the rats in the model control group and blank control group received gavage of 5 ml/(kg·d) distilled water, the intervention time was 4 weeks. After intervention, the rats were killed, and the hearts were dissected to obtain the samples of coronary artery. After embedding and frozen section, immunofluorescence method was used to detect the change of endarterium permeability in 3 groups, Western blot was used to detect matrix metalloproteinase-9 (MMP-9) and CD40L in coronary artery tissue, and enzyme linked immunosorbent assay (ELISA) was used to detect serum tumor necrosis factor-α (TNF-α) and C reaction protein (CRP). Results: After modeling, compared with the blank control group, total cholesterol (TC), triglyceride (TG) and low density lipoprotein cholesterin (LDL-c) in the treatment group and model control group were significantly higher (P<0.05), however, high density lipoprotein cholesterin (HDL-c) was significantly lower. The pathological sections showed that there was lipidosis in rat coronary artery in treatment group and model control group, indicating that the modeling was successful. Immunofluorescence showed that there was only a little fluorochrome permeability in artery in blank control group, there was some fluorochrome permeability in artery in the treatment group and there was a lot of fluorochrome permeability in artery in the model
EXPOSURE RELATED DOSE ESTIMATING MODEL (ERDEM)
ERDEM is a physiologically-based pharmacokinetic (PBPK) model with a graphical user interface (GUI) front end. Such a mathematical model was needed to make reliable estimates of the chemical dose to organs of animals or humans because of uncertainties of making route-to route, lo...
Dunn, T.L.
1996-03-01
This research is to provide improved strategies for enhanced oil recovery from the Tensleep Sandstone oil reservoirs in the Bighorn and Wind River basins, Wyoming. Because of the great range of API gravities of the oils produced from these reservoirs, the proposed study concentrates on understanding the spatial variation and anisotropy of relative permeability within the Tensleep Sandstone. This research will associate those spatial distributions and anisotropies with the depositional subfacies and zones of diagenetic alteration found within the sandstone. The associations of the above with pore geometry will link relative permeability with the dimensions of lithofacies and authigenic mineral facies. Hence, the study is to provide criteria for scaling this parameter on a range of scales, from the laboratory to the basin-wide scale of subfacies distribution. Effects of depositional processes and burial diagenesis will be investigated. Image analysis of pore systems will be done to produce algorithms for estimating relative permeability from petrographic analyses of core and well cuttings. In addition, these studies are being coupled with geochemical modeling and coreflood experiments to investigate the potential for wellbore scaling and formation damage anticipated during EOR, eg., CO{sub 2} flooding. This will provide a regional basis for EOR strategies for the largest potential target reservoir in Wyoming; results will have application to all eolian reservoirs through correlations of relative permeability variation and anisotropy with eolian depositional lithofacies.
NASA Astrophysics Data System (ADS)
Konno, Y.; Jin, Y.; Nagao, J.
2012-04-01
Oceanic gas hydrate deposits at high saturations have been found within sandy sediments in areas such as the Eastern Nankai Trough and the Gulf of Mexico. The recent discovery of these deposits has stimulated research and development programs exploring the use of gas hydrates as energy resources. Depressurization is thought to be a promising method for gas recovery from gas hydrates deposits; however, considerable water production is expected when this method is applied for oceanic gas hydrate deposits. The prediction of water production is a critical problem for successful gas production from these deposits. The gas-water relative permeability of gas-hydrate-bearing sediments is a key parameter to predict gas-water-ratio (GWR) during gas production. However, the experimental measurement of gas-water relative permeability for gas-hydrate-bearing sediments is a challenging problem due to a phase change (gas hydrate formation/dissociation) during gas-water flooding test. We used X-ray computed tomography (CT) and a newly-developed core holder to measure gas-water relative permeability for gas-hydrate-bearing sediments. X-ray CT was used to image a displacement front and quantify density changes during water flooding test in methane-hydrate-bearing cores. We obtained CT images every two minutes during a water flooding test for a gas-saturated methane-hydrate-bearing core. The movement of displacement front was captured from these CT images. Quantitative analysis of density change was also done to analyze the change of gas/water saturations. We developed a multi-sensor-tap core holder to minimize capillary end effect on the pressure measurements. To be able to obtain CT images by X-ray, the core holder was made of aluminum alloy. We successfully measured pressure differences of the intermediate section of the core during water flooding test. The change of pressure differences during water flooding test showed strong correlation with the movement of displacement front
Relating space radiation environments to risk estimates
NASA Technical Reports Server (NTRS)
Curtis, Stanley B.
1993-01-01
A number of considerations must go into the process of determining the risk of deleterious effects of space radiation to travelers. Among them are (1) determination of the components of the radiation environment (particle species, fluxes and energy spectra) which will encounter, (2) determination of the effects of shielding provided by the spacecraft and the bodies of the travelers which modify the incident particle spectra and mix of particles, and (3) determination of relevant biological effects of the radiation in the organs of interest. The latter can then lead to an estimation of risk from a given space scenario. Clearly, the process spans many scientific disciplines from solar and cosmic ray physics to radiation transport theeory to the multistage problem of the induction by radiation of initial lesions in living material and their evolution via physical, chemical, and biological processes at the molecular, cellular, and tissue levels to produce the end point of importance.
Membrane water permeability related to antigen-presenting function of dendritic cells
Wang, G F; Dong, C L; Tang, G S; Shen, Q; Bai, C X
2008-01-01
Aquaporin 5 (AQP5) is one of the water channel proteins which participate in a wide array of physiological processes and are primary determinants of membrane osmotic water permeability. The AQP5 gene is located in human chromosome 12q, the same region as the location of the major asthma susceptibility loci. In this study we try to determine whether the AQP5 knock-out has some effect on allergen-induced asthma. With a mouse asthma model induced by ovalbumin (OVA), we found that deletion of AQP5 reduced some major characteristic features of asthma, such as less inflammation cell infiltration in lung tissues, lower cytokine expression and fewer inflammation cells in bronchoalveolar lavage fluids compared with those from wild-type (WT) mice. Because it was found that mice injected intratracheally with OVA-pulsed dendritic cells (DCs), the AQP5 gene knock-out (AQP5−/−) ones presented fewer inflammation cells. Because DCs are major antigen-presenting cells that play an important role in antigen-induced asthma, we also probed into the possible effect of gene knock-out on DCs. Surprisingly, reverse transcription–polymerase chain reaction and fluorescence activated cell sorter analysis showed high levels of AQP5 on the surface of DCs from in vivo or bone marrow monocyte-derived DCs (mDC) in vitro. Immature mDC from AQP5 knock-out mice (AQP5−/−) showed decreased expression of CD80 and CD86 and endocytosis ability compared with that from WT, but the difference disappeared after mDCs matured with lipopolysaccharide. AQP5-mediated water transmembrane may play some role in the function of DCs. However, the mechanism of the effect of AQP5 on the DCs' function needs to be investigated further. PMID:18647319
1976-01-01
In artificial lipid bilayer membranes, the ratio of the water permeability coefficient (Pd(water)) to the permeability coefficient of an arbitrary nonelectrolyte such as n-butyramide (Pd(n-butyramide)) remains relatively constant with changes in lipid composition and temperature, even though the individual Pd's increase more than 100- fold. I propose that this is a general rule that also holds for the lipid bilayers of cells and tissues, and that therefore if Pd(water)/Pd(solute greatly exceeds the value found for artifical lipid bilayers (where "solute" is a molecule, such as 1,6 hexanediol or n- butyramide, that crosses the cell membrane by a solubility-diffusion mechanism without the aid of a special transporting system), then water crosses the cell membrane via aqueous pores. Applying this criterion to the toad urinary bladder, we find that even in the unstimulated bladder, water probably crosses the luminal membrane primarily through small aqueous pores, and that this almost certainly the case after antidiuretic hormone (ADH) stimulation. I suggest that ADH stimulation ultimately leads either to formation (or enlargement) of pores, by the rearrangement of preexisting subunits, or to an unplugging of these pores. PMID:956768
Finkelstein, A
1976-08-01
In artificial lipid bilayer membranes, the ratio of the water permeability coefficient (Pd(water)) to the permeability coefficient of an arbitrary nonelectrolyte such as n-butyramide (Pd(n-butyramide)) remains relatively constant with changes in lipid composition and temperature, even though the individual Pd's increase more than 100-fold. I propose that this is a general rule that also holds for the lipid bilayers of cells and tissues, and that therefore if Pd(water)/Pd(solute greatly exceeds the value found for artifical lipid bilayers (where "solute" is a molecule, such as 1,6 hexanediol or n-butyramide, that crosses the cell membrane by a solubility-diffusion mechanism without the aid of a special transporting system), then water crosses the cell membrane via aqueous pores. Applying this criterion to the toad urinary bladder, we find that even in the unstimulated bladder, water probably crosses the luminal membrane primarily through small aqueous pores, and that this almost certainly the case after antidiuretic hormone (ADH) stimulation. I suggest that ADH stimulation ultimately leads either to formation (or enlargement) of pores, by the rearrangement of preexisting subunits, or to an unplugging of these pores.
Relating space radiation environments to risk estimates
Curtis, S.B.
1991-10-01
This lecture will provide a bridge from the physical energy or LET spectra as might be calculated in an organ to the risk of carcinogenesis, a particular concern for extended missions to the moon or beyond to Mars. Topics covered will include (1) LET spectra expected from galactic cosmic rays, (2) probabilities that individual cell nuclei in the body will be hit by heavy galactic cosmic ray particles, (3) the conventional methods of calculating risks from a mixed environment of high and low LET radiation, (4) an alternate method which provides certain advantages using fluence-related risk coefficients (risk cross sections), and (5) directions for future research and development of these ideas.
NASA Astrophysics Data System (ADS)
Darwish, M. A.; Saafan, S. A.; El-Kony, D.; Salahuddin, N. A.
2015-07-01
Ferrite nanoparticles - having the compositions Li(x/2)(Ni0.5Zn0.5)(1-x)Fe(2+x/2)O4 (x=0, 0.2, 0.3) - have been prepared by the co-precipitation method. The prepared powders have been divided into groups and sintered at different temperatures (373 K, 1074 K and 1473 K). X-Ray diffraction analysis (XRD) for all samples has confirmed the formation of the desired ferrites with crystallite sizes within the nanoscale (<100 nm). The dc conductivity, the relative permeability and the magnetization of the ferrite samples have been investigated and according to the results, the sample Li0.15(Ni0.5Zn0.5)0.7 Fe2.15O4 sintered at 1473 K has been chosen to prepare the composites. The particle size of this sample has been recalculated by using JEOL JEM-100SX transmission electron microscope and it has been found about 64.7 nm. Then, a pure epoxy sample and four pristine epoxy resin /Li0.15(Ni0.5Zn0.5)0.7 Fe2.15O4 composites have been prepared using different ferrite contents (20%, 30%, 40%, and 50%) wt.%. These samples have been characterized by Fourier transform infrared (FTIR) spectroscopy and their dc conductivity, relative permeability and magnetization have also been investigated. The obtained results indicate that the investigated composites may be promising candidates for practical applications such as EMI suppressor and high frequency applications.
Cavé, Lisa; Al, Tom; Xiang, Yan; Vilks, Peter
2009-01-01
The measurement of diffusive properties of low-permeability rocks is of interest to the nuclear power industry, which is considering the option of deep geologic repositories for management of radioactive waste. We present a simple, non-destructive, constant source in-diffusion method for estimating one-dimensional pore diffusion coefficients (D(p)) in geologic materials based on X-ray radiography. Changes in X-ray absorption coefficient (Deltamicro) are used to quantify changes in relative concentration (C/C(0)) of an X-ray attenuating iodide tracer as the tracer solution diffuses through the rock pores. Estimated values of D(p) are then obtained by fitting an analytical solution to the measured concentration profiles over time. Measurements on samples before and after saturation with iodide can also be used to determine iodide-accessible porosity (phi(I)). To evaluate the radiography method, results were compared with traditional steady-state through-diffusion measurements on two rock types: shale and limestone. Values of D(p) of (4.8+/-2.5)x10(-11) m(2).s(-1) (mean+/-standard deviation) were measured for samples of Queenston Formation shale and (2.6+/-1.0)x10(-11) m(2).s(-1) for samples of Cobourg Formation limestone using the radiography method. The range of results for each rock type agree well with D(p) values of (4.6+/-2.0)x10(-11) m(2).s(-1) for shale and (3.5+/-1.8)x10(-11) m(2).s(-1) for limestone, calculated from through-diffusion experiments on adjacent rock samples. Low porosity (0.01 to 0.03) and heterogeneous distribution of porosity in the Cobourg Formation may be responsible for the slightly poorer agreement between radiography and through-diffusion results for limestones. Mean values of phi(I) for shales (0.060) and limestones (0.028) were close to mean porosity measurements made on bulk samples by the independent water loss technique (0.062 and 0.020 for shales and limestones, respectively). Radiography measurements offer the advantage of time
Soil Water Retention and Relative Permeability for Full Range of Saturation
Zhang, Z. F.
2010-09-28
Common conceptual models for unsaturated flow often rely on the oversimplified representation of medium pores as a bundle of cylindrical capillaries and assume that the matric potential is attributed to capillary forces only. The adsorptive surface forces are ignored. It is often assumed that aqueous flow is negligible when a soil is near or at the residual water content. These models are successful at high and medium water contents but often give poor results at low water contents. These models do not apply to conditions at which water content is less than the residual water content. We extend the lower bound of existing water-retention functions and conductivity models from residual water content to the oven-dry condition (i.e., zero water content) by defining a state-dependent, residual-water content for a soil drier than a critical value. Furthermore, a hydraulic conductivity model for smooth uniform spheres was modified by introducing a correction factor to describe the film flow-induced hydraulic conductivity for natural porous media. The total unsaturated hydraulic conductivity is the sum of those due to capillary and film flow. The extended retention and conductivity models were verified with six datasets from the literature. Results show that, when the soil is at high and intermediate water content, there is no difference between the un-extended and the extended models; when the soil is at low water content, the un-extended models overestimate the water content but under-estimate the conductivity while the extended models match the retention and conductivity measurements well.
The relative performance of targeted maximum likelihood estimators.
Porter, Kristin E; Gruber, Susan; van der Laan, Mark J; Sekhon, Jasjeet S
2011-01-01
There is an active debate in the literature on censored data about the relative performance of model based maximum likelihood estimators, IPCW-estimators, and a variety of double robust semiparametric efficient estimators. Kang and Schafer (2007) demonstrate the fragility of double robust and IPCW-estimators in a simulation study with positivity violations. They focus on a simple missing data problem with covariates where one desires to estimate the mean of an outcome that is subject to missingness. Responses by Robins, et al. (2007), Tsiatis and Davidian (2007), Tan (2007) and Ridgeway and McCaffrey (2007) further explore the challenges faced by double robust estimators and offer suggestions for improving their stability. In this article, we join the debate by presenting targeted maximum likelihood estimators (TMLEs). We demonstrate that TMLEs that guarantee that the parametric submodel employed by the TMLE procedure respects the global bounds on the continuous outcomes, are especially suitable for dealing with positivity violations because in addition to being double robust and semiparametric efficient, they are substitution estimators. We demonstrate the practical performance of TMLEs relative to other estimators in the simulations designed by Kang and Schafer (2007) and in modified simulations with even greater estimation challenges. PMID:21931570
Estimates of Preventability and Their Relation to Health Behavior.
ERIC Educational Resources Information Center
Poole, Gary D.
It was hypothesized that a person's estimates of the preventability of health problems would be related to health behaviors such that a person who engages in healthful behavior should make higher estimates of preventability. A study was conducted to investigate the relationship between causal attribution of health problems and health-related…
The pH dependency of relative ion permeabilities in the crayfish giant axon.
Strickholm, A; Wallin, B G; Shrager, P
1969-07-01
The dependence of the membrane potential on potassium, chloride, and sodium ions, was determined at the pH's of 6.0, 7.5, and 9.0 for the resting and depolarized crayfish ventral nerve cord giant axon. In normal saline (external potassium = 5.4 mM), the dependence of the membrane potential on the external potassium ions decreased with lowered pH while that for chloride increased. In contrast, in the potassium depolarized axon (external potassium = 25 mM), the dependence of the membrane potential on external potassium was minimum around pH 7.5 and increased in either more acidic or basic pH. In addition, the dependence of the membrane potential on external chloride in the depolarized axon was maximum at pH 7.5 and decreased in either more acidic or basic pH. The sodium dependency of the membrane potential was small and relatively unaffected by pH or depolarization. The data are interpreted as indicating a reversible surface membrane protein-phospholipid conformation change which occurs in the transition from the resting to the depolarized axon. PMID:5791546
Wang, Yusong; Bradford, Scott A; Šimůnek, Jiří
2014-04-01
Dual-permeability models are increasingly used to quantify the transport of solutes and microorganisms in soils with preferential flow. An ability to accurately determine the model parameters and their variation with preferential pathway characteristics is crucial for predicting the transport of microorganisms in the field. The dual-permeability model with optimized parameters was able to accurately describe the transport of E. coli D21g in columns with artificial macropores of different configurations and lengths at two ionic strength levels (1 and 20mM NaCl). Correlations between the model parameters and the structural geometry of the preferential flow path were subsequently investigated. Decreasing the macropore length produced a decrease in the apparent saturated hydraulic conductivity of the macropore domain and an increase in the mass transfer between the macropore and matrix domains. The mass transfer coefficient was also found to be dependent on the configuration of the preferential flow pathway. A linear superposition approach was used to estimate field-scale preferential transport behavior for hypothetical fields with different amounts and configurations of macropores. Upscaling procedures were numerically investigated to predict this field-scale transport behavior from column-scale parameters. The upscaling method provided a satisfactory prediction of the field results under the tested scenarios. This information will be useful in assessing the risks of microbial transport due to preferential flow. PMID:24589387
Wang, Yusong; Bradford, Scott A; Šimůnek, Jiří
2014-04-01
Dual-permeability models are increasingly used to quantify the transport of solutes and microorganisms in soils with preferential flow. An ability to accurately determine the model parameters and their variation with preferential pathway characteristics is crucial for predicting the transport of microorganisms in the field. The dual-permeability model with optimized parameters was able to accurately describe the transport of E. coli D21g in columns with artificial macropores of different configurations and lengths at two ionic strength levels (1 and 20mM NaCl). Correlations between the model parameters and the structural geometry of the preferential flow path were subsequently investigated. Decreasing the macropore length produced a decrease in the apparent saturated hydraulic conductivity of the macropore domain and an increase in the mass transfer between the macropore and matrix domains. The mass transfer coefficient was also found to be dependent on the configuration of the preferential flow pathway. A linear superposition approach was used to estimate field-scale preferential transport behavior for hypothetical fields with different amounts and configurations of macropores. Upscaling procedures were numerically investigated to predict this field-scale transport behavior from column-scale parameters. The upscaling method provided a satisfactory prediction of the field results under the tested scenarios. This information will be useful in assessing the risks of microbial transport due to preferential flow.
Pascoe, Robert J; Masucci, John A; Foley, Joe P
2006-02-01
As the pharmaceutical industry continues the daunting search for novel drug candidates, there remains a need for rapid screening methods not only for biological activity, but for physiochemical properties as well. It is invaluable that adequate model systems for absorption and/or bioavailability be developed early in the drug evaluation process to avoid the loss of promising compounds late in development. The focus of this paper is the use of vesicle EKC (VEKC) as a high-throughput, easy, cost-effective, and predictive model for the passive transcellular diffusion of drug candidates in the intestinal epithelium. Vesicles are large aggregates of molecules containing a spherical bilayer structure encapsulating an internal cavity of solvent. It is this bilayer structure that makes vesicles attractive as model membranes. In this study, vesicles were synthesized from both phospholipids and surfactant aggregates, and then employed as pseudostationary phases in EKC (VEKC). The interaction of drug molecules with vesicles in EKC was then used as the basis for an in vitro assay to evaluate passive diffusion. The VEKC technique showed a statistical correlation between the retention of drug candidates using surfactant and phospholipid vesicles and passive diffusion data (log Pow and colon adenocarcinoma). VEKC analysis offers high-throughput capabilities due to the short run times, low sample, and solvent volumes necessary, as well as instrument automation. However, due to the complexity of drug absorption in the intestine, difficulty arises when a single in vitro model is used to predict in vivo absorption characteristics. Therefore, the retention of drug candidates using VEKC in conjunction with other permeability prediction methods can provide a primary screen for a large number of drug candidates early in the drug discovery process with minimal resources.
NASA Astrophysics Data System (ADS)
Hsu, S. Y.; Tsai, J. P.; Chang, L. C.
2014-12-01
The flow of three immiscible fluids - water, NAPL, air - in porous media is important in many subsurface processes. To model the three-fluid flow, the relation of relative permeability-saturation-capillary pressure (k-S-P) of three fluids is of central importance. In this experimental study, we directly measure the k-S-P of the water (wetting phase) when three fluids are coexist in a micromodel during the water drainage and imbibition. The results show that the sequence of the non-wetting fluids (air and NAPL) entering into the micromodel affects the fluid distributions as well as the relative permeability of water. During the drainage process, the relative permeability of water dropped drastically when the pathway of water from inlet to outlet of the micromodel was visually blocked by the non-wetting fluids. At this stage, the relative permeability of water was low but not down to zero. The water was still able to move via corner flows or thin-film flows. During the imbibition process, the water displaced two non-wetting liquids via both "snap-off" and "piston-type" motions. The relative permeability of water jumped when the water pathway was formed again. In addition, we found that the well-known scaling format proposed by Parker et al. [1] might fail when the interfaces between the most non-wetting (air) and the most wetting (water) fluids occurs in the three-fluids system. References[1] J. C. Parker, R. J. Lenhard, and T. Kuppusamy, Water Resources Research, 23, 4, 618-624 (1987)
NASA Astrophysics Data System (ADS)
Chen, Xiongyu; DiCarlo, David A.
2016-10-01
This study presents a new unsteady-state method for measuring two-phase relative permeability by obtaining local values of the three key parameters (saturation, pressure drop, and phase flux) versus time during a displacement. These three parameters can be substituted to two-phase Darcy Buckingham equation to directly determine relative permeability. To obtain the first two, we use a medical X-ray Computed Tomography (CT) scanner to monitor saturation in time and space, and six differential pressure transducers to measure the overall pressure drop and the pressure drops of five individual sections (divided by four pressure taps on the core) continuously. At each scanning time, the local phase flux is obtained by spatially integrating the saturation profile and converting this to the flux using a fractional flow framework. One advantage of this local method over most previous methods is that the capillary end effect is experimentally avoided; this improvement is crucial for experiments using low viscosity fluids such as supercritical and gas phases. To illustrate the new method, we conduct five CO2-brine primary drainage experiments in a 60.8 cm long and 116 mD Berea sandstone core at 20 °C and 1500 psi. In return, we obtain hundreds of unsteady-state CO2 and brine relative permeability data points that are consistent with steady-state relative permeability data from the same experiments. Due to the large amount of relative permeability data obtained by the new unsteady-state method, the uncertainties of the exponents in the Corey-type fits decrease by up to 90% compared with the steady-state method.
Minimax Quantum Tomography: Estimators and Relative Entropy Bounds.
Ferrie, Christopher; Blume-Kohout, Robin
2016-03-01
A minimax estimator has the minimum possible error ("risk") in the worst case. We construct the first minimax estimators for quantum state tomography with relative entropy risk. The minimax risk of nonadaptive tomography scales as O(1/sqrt[N])-in contrast to that of classical probability estimation, which is O(1/N)-where N is the number of copies of the quantum state used. We trace this deficiency to sampling mismatch: future observations that determine risk may come from a different sample space than the past data that determine the estimate. This makes minimax estimators very biased, and we propose a computationally tractable alternative with similar behavior in the worst case, but superior accuracy on most states. PMID:26991163
Estimating Relative Positions of Outer-Space Structures
NASA Technical Reports Server (NTRS)
Balian, Harry; Breckenridge, William; Brugarolas, Paul
2009-01-01
A computer program estimates the relative position and orientation of two structures from measurements, made by use of electronic cameras and laser range finders on one structure, of distances and angular positions of fiducial objects on the other structure. The program was written specifically for use in determining errors in the alignment of large structures deployed in outer space from a space shuttle. The program is based partly on equations for transformations among the various coordinate systems involved in the measurements and on equations that account for errors in the transformation operators. It computes a least-squares estimate of the relative position and orientation. Sequential least-squares estimates, acquired at a measurement rate of 4 Hz, are averaged by passing them through a fourth-order Butterworth filter. The program is executed in a computer aboard the space shuttle, and its position and orientation estimates are displayed to astronauts on a graphical user interface.
Surprise Calculator: Estimating relative entropy and Surprise between samples
NASA Astrophysics Data System (ADS)
Seehars, Sebastian
2016-05-01
The Surprise is a measure for consistency between posterior distributions and operates in parameter space. It can be used to analyze either the compatibility of separately analyzed posteriors from two datasets, or the posteriors from a Bayesian update. The Surprise Calculator estimates relative entropy and Surprise between two samples, assuming they are Gaussian. The software requires the R package CompQuadForm to estimate the significance of the Surprise, and rpy2 to interface R with Python.
Huber's M-estimation in relative GPS positioning: computational aspects
NASA Astrophysics Data System (ADS)
Chang, X.-W.; Guo, Y.
2005-08-01
When GPS signal measurements have outliers, using least squares (LS) estimation is likely to give poor position estimates. One of the typical approaches to handle this problem is to use robust estimation techniques. We study the computational issues of Huber’s M-estimation applied to relative GPS positioning. First for code-based relative positioning, we use simulation results to show that Newton’s method usually converges faster than the iteratively reweighted least squares (IRLS) method, which is often used in geodesy for computing robust estimates of parameters. Then for code- and carrier-phase-based relative positioning, we present a recursive modified Newton method to compute Huber’s M-estimates of the positions. The structures of the model are exploited to make the method efficient, and orthogonal transformations are used to ensure numerical reliability of the method. Economical use of computer memory is also taken into account in designing the method. Simulation results show that the method is effective.
Permeability extraction: A sonic log inversion
Akbar, N.; Kim, J.J.
1994-12-31
In this paper the authors provide the missing important link between permeability and acoustic velocities by generating a permeability-dependent synthetic sonic log in a carbonate reservoir. The computations are based on Akbar`s theory that relates wave velocity to frequency, rock properties (e.g., lithology, permeability, and porosity), and fluid saturation and properties (viscosity, density, and compressibility). An inverted analytical expression of the theory is used to extract permeability from sonic velocity. The synthetic sonic and the computed permeability are compared with the observed sonic log and with plug permeability, respectively. The results demonstrate, as predicted by theory, that permeability can be related directly to acoustic velocities.
Estimating relative demand for wildlife: Conservation activity indicators
NASA Astrophysics Data System (ADS)
Gray, Gary G.; Larson, Joseph S.
1982-09-01
An alternative method of estimating relative demand among nonconsumptive uses of wildlife and among wildlife species is proposed. A demand intensity score (DIS), derived from the relative extent of an individual's involvement in outdoor recreation and conservation activities, is used as a weighting device to adjust the importance of preference rankings for wildlife uses and wildlife species relative to other members of a survey population. These adjusted preference rankings were considered to reflect relative demand levels (RDLs) for wildlife uses and for species by the survey population. This technique may be useful where it is not possible or desirable to estimate demand using traditional economic means. In one of the findings from a survey of municipal conservation commission members in Massachusetts, presented as an illustration of this methodology, poisonous snakes were ranked third in preference among five groups of reptiles. The relative demand level for poisonous snakes, however, was last among the five groups.
Relative azimuth inversion by way of damped maximum correlation estimates
Ringler, A.T.; Edwards, J.D.; Hutt, C.R.; Shelly, F.
2012-01-01
Horizontal seismic data are utilized in a large number of Earth studies. Such work depends on the published orientations of the sensitive axes of seismic sensors relative to true North. These orientations can be estimated using a number of different techniques: SensOrLoc (Sensitivity, Orientation and Location), comparison to synthetics (Ekstrom and Busby, 2008), or by way of magnetic compass. Current methods for finding relative station azimuths are unable to do so with arbitrary precision quickly because of limitations in the algorithms (e.g. grid search methods). Furthermore, in order to determine instrument orientations during station visits, it is critical that any analysis software be easily run on a large number of different computer platforms and the results be obtained quickly while on site. We developed a new technique for estimating relative sensor azimuths by inverting for the orientation with the maximum correlation to a reference instrument, using a non-linear parameter estimation routine. By making use of overlapping windows, we are able to make multiple azimuth estimates, which helps to identify the confidence of our azimuth estimate, even when the signal-to-noise ratio (SNR) is low. Finally, our algorithm has been written as a stand-alone, platform independent, Java software package with a graphical user interface for reading and selecting data segments to be analyzed.
Estimating body related soft biometric traits in video frames.
Arigbabu, Olasimbo Ayodeji; Ahmad, Sharifah Mumtazah Syed; Adnan, Wan Azizun Wan; Yussof, Salman; Iranmanesh, Vahab; Malallah, Fahad Layth
2014-01-01
Soft biometrics can be used as a prescreening filter, either by using single trait or by combining several traits to aid the performance of recognition systems in an unobtrusive way. In many practical visual surveillance scenarios, facial information becomes difficult to be effectively constructed due to several varying challenges. However, from distance the visual appearance of an object can be efficiently inferred, thereby providing the possibility of estimating body related information. This paper presents an approach for estimating body related soft biometrics; specifically we propose a new approach based on body measurement and artificial neural network for predicting body weight of subjects and incorporate the existing technique on single view metrology for height estimation in videos with low frame rate. Our evaluation on 1120 frame sets of 80 subjects from a newly compiled dataset shows that the mentioned soft biometric information of human subjects can be adequately predicted from set of frames. PMID:25121120
Estimating Body Related Soft Biometric Traits in Video Frames
Arigbabu, Olasimbo Ayodeji; Ahmad, Sharifah Mumtazah Syed; Adnan, Wan Azizun Wan; Yussof, Salman; Iranmanesh, Vahab; Malallah, Fahad Layth
2014-01-01
Soft biometrics can be used as a prescreening filter, either by using single trait or by combining several traits to aid the performance of recognition systems in an unobtrusive way. In many practical visual surveillance scenarios, facial information becomes difficult to be effectively constructed due to several varying challenges. However, from distance the visual appearance of an object can be efficiently inferred, thereby providing the possibility of estimating body related information. This paper presents an approach for estimating body related soft biometrics; specifically we propose a new approach based on body measurement and artificial neural network for predicting body weight of subjects and incorporate the existing technique on single view metrology for height estimation in videos with low frame rate. Our evaluation on 1120 frame sets of 80 subjects from a newly compiled dataset shows that the mentioned soft biometric information of human subjects can be adequately predicted from set of frames. PMID:25121120
Estimating body related soft biometric traits in video frames.
Arigbabu, Olasimbo Ayodeji; Ahmad, Sharifah Mumtazah Syed; Adnan, Wan Azizun Wan; Yussof, Salman; Iranmanesh, Vahab; Malallah, Fahad Layth
2014-01-01
Soft biometrics can be used as a prescreening filter, either by using single trait or by combining several traits to aid the performance of recognition systems in an unobtrusive way. In many practical visual surveillance scenarios, facial information becomes difficult to be effectively constructed due to several varying challenges. However, from distance the visual appearance of an object can be efficiently inferred, thereby providing the possibility of estimating body related information. This paper presents an approach for estimating body related soft biometrics; specifically we propose a new approach based on body measurement and artificial neural network for predicting body weight of subjects and incorporate the existing technique on single view metrology for height estimation in videos with low frame rate. Our evaluation on 1120 frame sets of 80 subjects from a newly compiled dataset shows that the mentioned soft biometric information of human subjects can be adequately predicted from set of frames.
NASA Astrophysics Data System (ADS)
Wassermann, Jérôme; Sabroux, Jean-Christophe; Richon, Patrick; Pontreau, Sébastien; Guillon, Sophie; Pili, Eric
2010-05-01
The Roselend tunnel was drilled in the fifties by blasting in the micashists, granites and gneisses of the Méraillet massif (French Alps). It is situated on the shore of the Roselend reservoir Lake near its dam. Several tectonic shear fractures related to the Alpine orogeny intersect the dead end tunnel (with length of 128 m and section about 2 m), indeed the fracture density varies from 0.45 to 1 fracture per meter along the tunnel (Dezayes and Villemin 2002). Some fractures are partially or totally filled with secondary minerals. The flow rates of percolating water through the fractured medium are seasonal dependent. Large fractures drain a large fluid volume unlike small ones that drain limited fluid volume (Patriarche et al. 2007). The Roselend underground laboratory allows the study of the geochemical and geophysical responses of a fractured rock mass to periodic sollicitations due to water level variations of the nearby Roselend reservoir Lake. The tunnel was instrumented in the nineties to understand the relationship between radon (Rn-222) concentration and water level variations of the Roselend reservoir Lake (Trique et al. 1999). In order to characterize the geometry and the extent of the EDZ, core drilling and permeability measurements through pneumatic testing are performed along the Roselend tunnel. Drilled core analysis consists of direct observations at a macroscopic scale of fractures (density of fractures from EDZ) and also at a microscopic scale via thin sections. Method of pressure build-up in wells (Jakubick and Franz 1993, Bossart et al. 2002) is used to determine permeability profile along each borehole and hence to precise the extent and geometry of the EDZ. A strong correlation is observed between permeability profiles and the density of fractures estimated from core analysis. The extent of the EDZ appears to be about one tunnel radius i.e. one meter around the tunnel corridor. Another experiment consisting of continuous differential
Ranathunge, Kosala; Schreiber, Lukas
2011-01-01
Although it is implied that suberized apoplastic barriers of roots negatively correlate with water and solute permeabilities, direct transport measurements across roots with altered amounts and compositions of aliphatic suberin are scarce. In the present study, hydroponically grown Arabidopsis wild types (Col8 and Col0) and different suberin mutants with altered amounts and/or compositions (horst, esb1-1, and esb1-2) were used to test this hypothesis. Detailed histochemical studies revealed late development of Casparian bands and suberin lamellae in the horst mutant compared with wild types and esb mutants. Suberin analysis with gas chromatography and mass spectrometry (GC-MS) showed that the horst mutant had ∼33% lower amounts of aliphatic monomers than Col8 and Col0. In contrast, enhanced suberin mutants (esb1-1 and esb1-2) had twice the amount of suberin as the wild types. Correlative permeability measurements, which were carried out for the first time with a root pressure probe for Arabidopsis, revealed that the hydraulic conductivity (Lpr) and NaCl permeability (Psr) of the whole root system of the horst mutant were markedly greater than in the respective wild types. This was reflected by the total amounts of aliphatic suberin determined in the roots. However, increased levels of aliphatic suberin in esb mutants failed to reduce either water or NaCl permeabilities below those of the wild types. It was concluded that the simple view and the conventional assumption that the amount of root suberin negatively correlates with permeability may not always be true. The aliphatic monomer arrangement in the suberin biopolymer and its microstructure also play a role in apoplastic barrier formation. PMID:21421706
NASA Astrophysics Data System (ADS)
Zhang, Duo; Papadikis, K.; Gu, Sai
2016-09-01
In the current paper, the effect of the geometrical characteristics of 2-D porous media on the relative permeability in immiscible two-phase flows is studied. The generation of the different artificial porous media is performed using a Boolean model based on a random distribution of overlapping circles/ellipses, the size and shape of which are chosen to satisfy the specific Minkowski functionals (i.e. volume fraction, solid line contour length, connectivity). The study aims to identify how each different Minkowski functional affects the relative permeability of each phase at various saturations of the non-wetting phase. A 2-D multi-relaxation time (MRT) lattice Boltzmann model (LBM) that can handle high density ratios is employed in the simulation. The relationship between the driving forces G and the relative permeabilities of the two phases for every artificial structure is quantified. It is found that for high non-wetting phase saturations (fully connected flow), a non-linear relationship exists between the non-wetting phase flow rate and the driving force, whilst this relationship becomes linear at higher magnitudes of the latter. The force magnitude required to approach the linear region is highly influenced by the pore size distribution and the connectivity of the solid phase. For lower non-wetting phase saturation values, its relative permeability in the linear regime decreases as the fraction of small pores in the structure increases and the non-wetting phase flow becomes disconnected. A strong influence of the solid phase connectivity is also observed.
Chinma, C E; Ariahu, C C; Alakali, J S
2015-04-01
The effect of temperature and relative humidity on the water vapour permeability (WVP) and mechanical properties of cassava starch and soy protein concentrate (SPC) based edible films containing 20 % glycerol level were studied. Tensile strength and elastic modulus of edible films increased with increase in temperature and decreased with increase in relative humidity, while elongation at break decreased. Water vapour permeability of the films increased (2.6-4.3 g.mm/m(2).day.kPa) with increase in temperature and relative humidity. The temperature dependence of water vapour permeation of cassava starch-soy protein concentrate films followed Arrhenius relationship. Activation energy (Ea) of water vapour permeation of cassava starch-soy protein concentrate edible films ranged from 1.9 to 5.3 kJ/mol (R (2) ≥ 0.93) and increased with increase in SPC addition. The Ea values were lower for the bio-films than for polyvinylidene chloride, polypropylene and polyethylene which are an indication of low water vapour permeability of the developed biofilms compared to those synthetic films.
NASA Astrophysics Data System (ADS)
Liu, Hui-Hai
2014-05-01
In clay or other low-permeability media, water flow becomes non-Darcian and characterized by the non-linear relationship between water flux and hydraulic gradient. This work is devoted to addressing a number of key issues related to geological disposal of high-level nuclear waste in clay/shale formations. It is demonstrated that water flow velocity in the damaged zone (often considered as a potential preferential advection paths in a repository) surrounding the tunnel is extremely small, as a result of non-Darcian flow behavior, such that solute transport is dominated by diffusion, rather than advection. The finding is also consistent with the often-observed existence of persistent abnormal pressures in shale formations. While relative permeability is the key parameter for modeling the unsaturated flow process, without incorporating non-Darcian flow behavior, significant errors can occur in the determination of relative permeability values from traditional measurement methods. An approach for dealing with temperature impact on non-Darcian flow and a formulation to calculate non-Darcian water flux in an anisotropic medium are presented, taking into consideration that a geological repository is subject to temperature evolution in the near field as a result of heat generated by nuclear waste, and that shale formations are generally anisotropic.
Worldwide Estimates Relative to Five Continental-Scale Populations
Steele, Christopher D; Court, Denise Syndercombe; Balding, David J
2014-01-01
We estimate the population genetics parameter (also referred to as the fixation index) from short tandem repeat (STR) allele frequencies, comparing many worldwide human subpopulations at approximately the national level with continental-scale populations. is commonly used to measure population differentiation, and is important in forensic DNA analysis to account for remote shared ancestry between a suspect and an alternative source of the DNA. We estimate comparing subpopulations with a hypothetical ancestral population, which is the approach most widely used in population genetics, and also compare a subpopulation with a sampled reference population, which is more appropriate for forensic applications. Both estimation methods are likelihood-based, in which is related to the variance of the multinomial-Dirichlet distribution for allele counts. Overall, we find low values, with posterior 97.5 percentiles when comparing a subpopulation with the most appropriate population, and even for inter-population comparisons we find . These are much smaller than single nucleotide polymorphism-based inter-continental estimates, and are also about half the magnitude of STR-based estimates from population genetics surveys that focus on distinct ethnic groups rather than a general population. Our findings support the use of up to 3% in forensic calculations, which corresponds to some current practice. PMID:26460400
Multiple Component Event-Related Potential (mcERP) Estimation
NASA Technical Reports Server (NTRS)
Knuth, K. H.; Clanton, S. T.; Shah, A. S.; Truccolo, W. A.; Ding, M.; Bressler, S. L.; Trejo, L. J.; Schroeder, C. E.; Clancy, Daniel (Technical Monitor)
2002-01-01
We show how model-based estimation of the neural sources responsible for transient neuroelectric signals can be improved by the analysis of single trial data. Previously, we showed that a multiple component event-related potential (mcERP) algorithm can extract the responses of individual sources from recordings of a mixture of multiple, possibly interacting, neural ensembles. McERP also estimated single-trial amplitudes and onset latencies, thus allowing more accurate estimation of ongoing neural activity during an experimental trial. The mcERP algorithm is related to informax independent component analysis (ICA); however, the underlying signal model is more physiologically realistic in that a component is modeled as a stereotypic waveshape varying both in amplitude and onset latency from trial to trial. The result is a model that reflects quantities of interest to the neuroscientist. Here we demonstrate that the mcERP algorithm provides more accurate results than more traditional methods such as factor analysis and the more recent ICA. Whereas factor analysis assumes the sources are orthogonal and ICA assumes the sources are statistically independent, the mcERP algorithm makes no such assumptions thus allowing investigators to examine interactions among components by estimating the properties of single-trial responses.
Seismic waves increase permeability.
Elkhoury, Jean E; Brodsky, Emily E; Agnew, Duncan C
2006-06-29
Earthquakes have been observed to affect hydrological systems in a variety of ways--water well levels can change dramatically, streams can become fuller and spring discharges can increase at the time of earthquakes. Distant earthquakes may even increase the permeability in faults. Most of these hydrological observations can be explained by some form of permeability increase. Here we use the response of water well levels to solid Earth tides to measure permeability over a 20-year period. At the time of each of seven earthquakes in Southern California, we observe transient changes of up to 24 degrees in the phase of the water level response to the dilatational volumetric strain of the semidiurnal tidal components of wells at the Piñon Flat Observatory in Southern California. After the earthquakes, the phase gradually returns to the background value at a rate of less than 0.1 degrees per day. We use a model of axisymmetric flow driven by an imposed head oscillation through a single, laterally extensive, confined, homogeneous and isotropic aquifer to relate the phase response to aquifer properties. We interpret the changes in phase response as due to changes in permeability. At the time of the earthquakes, the permeability at the site increases by a factor as high as three. The permeability increase depends roughly linearly on the amplitude of seismic-wave peak ground velocity in the range of 0.21-2.1 cm s(-1). Such permeability increases are of interest to hydrologists and oil reservoir engineers as they affect fluid flow and might determine long-term evolution of hydrological and oil-bearing systems. They may also be interesting to seismologists, as the resulting pore pressure changes can affect earthquakes by changing normal stresses on faults.
Estimating relative risks for common outcome using PROC NLP.
Yu, Binbing; Wang, Zhuoqiao
2008-05-01
In cross-sectional or cohort studies with binary outcomes, it is biologically interpretable and of interest to estimate the relative risk or prevalence ratio, especially when the response rates are not rare. Several methods have been used to estimate the relative risk, among which the log-binomial models yield the maximum likelihood estimate (MLE) of the parameters. Because of restrictions on the parameter space, the log-binomial models often run into convergence problems. Some remedies, e.g., the Poisson and Cox regressions, have been proposed. However, these methods may give out-of-bound predicted response probabilities. In this paper, a new computation method using the SAS Nonlinear Programming (NLP) procedure is proposed to find the MLEs. The proposed NLP method was compared to the COPY method, a modified method to fit the log-binomial model. Issues in the implementation are discussed. For illustration, both methods were applied to data on the prevalence of microalbuminuria (micro-protein leakage into urine) for kidney disease patients from the Diabetes Control and Complications Trial. The sample SAS macro for calculating relative risk is provided in the appendix.
NASA Astrophysics Data System (ADS)
Diliberto, Iole Serena; Cangemi, Marianna; Gagliano, Antonina Lisa; Inguaggiato, Salvatore; Madonia, Paolo; Pedone, Maria; Fabio Pisciotta, Antonino
2016-04-01
Vulcano, the southernmost island of the Aeolian archipelago (Italy), is presently characterized by active fumarolic fields located along the rim of La Fossa cone and the shoreline of the Baia di Levante beach, in the northern portion of the island.The Baia di Levante fumarolic vents are fed by a shallow hydrothermal aquifer heated by magmatic gases rising from the deep down, with a spatial distribution strongly affected by the local fracture network. These fractures are the expression of a deformation field, dominated by a northward motion to Lipari, abruptly decaying to the Vulcanello peninsula, immediately northward of the Baia di Levante beach. Variable rates of fluid transfer to the surface, following permeability changes affecting the fracture network are among the results of stress field variations over time which induce fluctuations in the pressure state of the hydrothermal system. Under these conditions, increments in hydrothermal gas flow, able to cause an increase of gas hazard, could be determined by a rearrangement of the shallow permeability distribution induced by changes in the deformation field. In this case not associated to any variation in the volcanic activity state. Since 2009 an huge gas flow increment has been noticed in some undersea vents of the Baia di Levante area, leading to increase of gas hazard in their immediate surroundings. On the contrary, the acquired data from the INGV volcanic surveillance program didn't suggest any correlated increase of the magmatic fluid component in the degassing activity.In July 2015, we carried out multi-parametric geochemical surveys in this area, based on direct (thermocouple) and indirect (thermal infrared camera and pyrometer) soil temperature, soil CO2 flux, atmospheric concentration of CO2 and H2S measurements at low elevation (one meter a.s.l.). The chemical and isotopic composition of low temperature fumarole gases was determined too.The comparison of the new data with previous surveys carried out
Quasi-likelihood estimation for relative risk regression models.
Carter, Rickey E; Lipsitz, Stuart R; Tilley, Barbara C
2005-01-01
For a prospective randomized clinical trial with two groups, the relative risk can be used as a measure of treatment effect and is directly interpretable as the ratio of success probabilities in the new treatment group versus the placebo group. For a prospective study with many covariates and a binary outcome (success or failure), relative risk regression may be of interest. If we model the log of the success probability as a linear function of covariates, the regression coefficients are log-relative risks. However, using such a log-linear model with a Bernoulli likelihood can lead to convergence problems in the Newton-Raphson algorithm. This is likely to occur when the success probabilities are close to one. A constrained likelihood method proposed by Wacholder (1986, American Journal of Epidemiology 123, 174-184), also has convergence problems. We propose a quasi-likelihood method of moments technique in which we naively assume the Bernoulli outcome is Poisson, with the mean (success probability) following a log-linear model. We use the Poisson maximum likelihood equations to estimate the regression coefficients without constraints. Using method of moment ideas, one can show that the estimates using the Poisson likelihood will be consistent and asymptotically normal. We apply these methods to a double-blinded randomized trial in primary biliary cirrhosis of the liver (Markus et al., 1989, New England Journal of Medicine 320, 1709-1713). PMID:15618526
Surface gas permeability of porous building materials: measurement, analysis and applications
NASA Astrophysics Data System (ADS)
Grover, David K. W.
In many events affecting our civil infrastructure, such as contamination or weathering, it is likely that only the surfaces of the affected building materials will be available for non-destructive measurements. In this work, we describe and analyze surface gas permeability measurements on a variety of natural and engineered building materials using two types of relatively new, non-destructive surface permeameters. It is shown that the surface gas permeability measurements correlate well with each other and could provide rapid estimates of macroscopic gas permeability and degradation of materials due to weathering. It is hypothesized that surface permeability can be used to predict macroscopic wicking of water. The results indicated that macroscopic wicking correlated reasonably well with surface permeability measurements of uniform materials with low permeabilities such as sandstones and clay brick.
Prediction of permeability change at high ambient stresses via the isotropic Skempton coefficient B
NASA Astrophysics Data System (ADS)
Zimmermann, G.; Bloecher, M. G.; Milsch, H.
2006-12-01
For gas, oil and water exploration reservoir permeability as a function of effective stress is one of the most important hydraulic parameters. Estimation of permeability, especially in deep reservoirs, is very difficult and time-consuming. Therefore, permeability is often estimated in laboratory experiments under simulated in-situ conditions. Under these experimental conditions with a flow across the sample, many effects lead to changes in permeability. Besides the flow paths reduction as a function of effective pressure, plugging of the sample and filters by fines migration or rust and a swelling of the clay content can occur, which results in a decrease in permeability. All these non-mechanical effects are time dependent and affect the permeability measurements, hence a separation of all these influences is hard to achieve. To avoid these problems we estimated the permeability pressure dependence with the isotropic Skempton coefficient. The Skempton coefficient is defined as undrained pore pressure change due to ambient stress changes B=dpu/dσm. We could show that a heterogeneous deformation of pore space geometry led to a decrease of the Skempton coefficient with increasing confining pressure. The mechanisms which influence the Skempton coefficient are similar to the behavior of the sandstone sample during the permeability measurements. In both cases we consider a change in pore pressure and an adjacent equalization across the flow channels at the micro-scale. These flow channels change their geometry depending on the applied stresses. Therefore, the reduction of the Skempton coefficient should be comparable to the reduction of permeability. To validate this assumption we present experiments on Lower Permian sandstone (Rotliegend) samples from the NE German Basin and compared Skempton coefficient and permeability measurements to find a coherence of both rock properties. Applying this relation of Skempton coefficient and permeability, we can predict rock
Maximum Correntropy Unscented Kalman Filter for Spacecraft Relative State Estimation
Liu, Xi; Qu, Hua; Zhao, Jihong; Yue, Pengcheng; Wang, Meng
2016-01-01
A new algorithm called maximum correntropy unscented Kalman filter (MCUKF) is proposed and applied to relative state estimation in space communication networks. As is well known, the unscented Kalman filter (UKF) provides an efficient tool to solve the non-linear state estimate problem. However, the UKF usually plays well in Gaussian noises. Its performance may deteriorate substantially in the presence of non-Gaussian noises, especially when the measurements are disturbed by some heavy-tailed impulsive noises. By making use of the maximum correntropy criterion (MCC), the proposed algorithm can enhance the robustness of UKF against impulsive noises. In the MCUKF, the unscented transformation (UT) is applied to obtain a predicted state estimation and covariance matrix, and a nonlinear regression method with the MCC cost is then used to reformulate the measurement information. Finally, the UT is adopted to the measurement equation to obtain the filter state and covariance matrix. Illustrative examples demonstrate the superior performance of the new algorithm. PMID:27657069
Permeability equipment for porous friction surfaces
NASA Astrophysics Data System (ADS)
Standiford, D. L.; Graul, R. A.; Lenke, L. R.
1985-04-01
Hydroplaning is the loss of traction between tires and pavement due to the presence of a layer of water. This loss of traction can result in loss of vehicle control. A porous friction surface (PFS) applied over an existing pavement permits the water to drain laterally and vertically away from the tire path, effectively lowering hydroplaning potential. Equipment used to measure pavement drainage (permeability) is discussed with respect to usage on porous friction surface. Background information on hydroplaning, flow theory, and PFS field performance as they are affected by permeability are also presented. Two dynamic test devices and four static devices are considered for measuring PFS permeability. Permeability tests are recommended to measure PFS permeability for maintenance purposes and construction control. Dynamic devices cited could possibly estimate hydroplaning potential; further research must be done to determine this. Permeability devices cannot be used to accurately estimate friction of a pavement surface, however, decreased permeability of a pavement infers a decrease in friction.
Durell, Gregory; Utvik, Toril Røe; Johnsen, Ståle; Frost, Tone; Neff, Jerry
2006-09-01
The oil companies operating in the Norwegian sector of the North Sea have conducted field studies since the mid-1990s to monitor produced water discharges to the ocean. These studies have been used to refine monitoring methods, and to develop and validate a dispersion and impact assessment model. This paper summarizes monitoring data from surveys conducted in two major oil and gas production areas, and compares the results to concentrations of polycyclic aromatic hydrocarbons (PAH) in surface waters predicted by the dose-related risk and effect assessment model (DREAM). Blue mussels and semi-permeable membrane devices (SPMDs) were deployed in the Ekofisk and Tampen Regions and analyzed for more than 50 PAH. PAH concentrations in ambient seawater were estimated based on the mussels and SPMD concentrations, and compared to model predictions. Surface water total PAH concentrations ranged from 25 to 350 ng/L within 1 km of the platform discharges and reached background levels of 4-8 ng/L within 5-10 km of the discharge; a 100,000-fold dilution of the PAH in the discharge water. The PAH concentrations in surface water, predicted by three methods, compared well for the Ekofisk Region. The model predicted higher concentrations than the field-based methods for parts of the Tampen Region; particularly the most tidally influenced areas. Tidally-mediated fluctuations in PAH concentrations in surface water must be considered because they affect the estimation of PAH concentrations from mussel and SPMD residue data, and the predictions by the DREAM model. Predictions using mussels, SPMDs, and modeling support and complement each other; all are valuable tools for estimating the fate and impact of chemical contaminants in produced water that are discharged to the ocean.
Alvarez-Figueroa, M Javiera; Pessoa-Mahana, C David; Palavecino-González, M Elisa; Mella-Raipán, Jaime; Espinosa-Bustos, Cristián; Lagos-Muñoz, Manuel E
2011-06-01
The permeability of five benzimidazole derivates with potential cannabinoid activity was determined in two models of membranes, parallel artificial membrane permeability assay (PAMPA) and skin, in order to study the relationship of the physicochemical properties of the molecules and characteristics of the membranes with the permeability defined by the Biopharmaceutics Classification System. It was established that the PAMPA intestinal absorption method is a good predictor for classifying these molecules as very permeable, independent of their thermodynamic solubility, if and only if these have a Log P(oct) value <3.0. In contrast, transdermal permeability is conditioned on the solubility of the molecule so that it can only serve as a model for classifying the permeability of molecules that possess high solubility (class I: high solubility, high permeability; class III: high solubility, low permeability).
Being surveyed can change later behavior and related parameter estimates.
Zwane, Alix Peterson; Zinman, Jonathan; Van Dusen, Eric; Pariente, William; Null, Clair; Miguel, Edward; Kremer, Michael; Karlan, Dean S; Hornbeck, Richard; Giné, Xavier; Duflo, Esther; Devoto, Florencia; Crepon, Bruno; Banerjee, Abhijit
2011-02-01
Does completing a household survey change the later behavior of those surveyed? In three field studies of health and two of microlending, we randomly assigned subjects to be surveyed about health and/or household finances and then measured subsequent use of a related product with data that does not rely on subjects' self-reports. In the three health experiments, we find that being surveyed increases use of water treatment products and take-up of medical insurance. Frequent surveys on reported diarrhea also led to biased estimates of the impact of improved source water quality. In two microlending studies, we do not find an effect of being surveyed on borrowing behavior. The results suggest that limited attention could play an important but context-dependent role in consumer choice, with the implication that researchers should reconsider whether, how, and how much to survey their subjects. PMID:21245314
Being surveyed can change later behavior and related parameter estimates
Zwane, Alix Peterson; Zinman, Jonathan; Van Dusen, Eric; Pariente, William; Null, Clair; Miguel, Edward; Kremer, Michael; Hornbeck, Richard; Giné, Xavier; Duflo, Esther; Devoto, Florencia; Crepon, Bruno; Banerjee, Abhijit
2011-01-01
Does completing a household survey change the later behavior of those surveyed? In three field studies of health and two of microlending, we randomly assigned subjects to be surveyed about health and/or household finances and then measured subsequent use of a related product with data that does not rely on subjects' self-reports. In the three health experiments, we find that being surveyed increases use of water treatment products and take-up of medical insurance. Frequent surveys on reported diarrhea also led to biased estimates of the impact of improved source water quality. In two microlending studies, we do not find an effect of being surveyed on borrowing behavior. The results suggest that limited attention could play an important but context-dependent role in consumer choice, with the implication that researchers should reconsider whether, how, and how much to survey their subjects. PMID:21245314
NASA Astrophysics Data System (ADS)
Niu, B.; Al-Menhali, A.; Krevor, S. C.
2014-12-01
Successful industrial scale carbon dioxide injection into deep saline aquifers will be dependent on the ability to model the flow of the fluid and to quantify the impact of various trapping mechanisms. The effectiveness of the models is in turn dependent on high quality laboratory measurements of basic multiphase flow properties such as relative permeability and residual trapping at reservoir conditions. Compared with typical oil-brine systems, however, a unique defining characteristic of the CO2-brine system is its combination of high viscosity ratio and low density ratio. This combination of properties results in unique complications for experiments with CO2 and brine and unique flow conditions must be used to achieve the combined goals of observations across a large saturation range and the avoidance of the effects of heterogeneity as well as capillary forces and gravity segregation. We have simulated the corefloods experiments at various conditions and calculated with different interpretation techniques: Steady state method, JBN-type method and history matching. As one of the essential mechanisms for CO2 storage underground, residual trapping refers to the trapping of CO2 through capillary forces within the pore space of a permeable aquifer. There are few studies that have observed the trapping characteristics for CO2-brine systems in permeable rocks, including the impact of reservoir conditions, and this remains a major uncertainty for geologic CO2 storage. This work presents results from a core-flooding laboratory that has been recently developed at Imperial College dedicated to observations of CO2-brine systems. The apparatus includes high precision pumps, accurate temperature control and a rotating X-ray CT scanner that allows experiments to be performed in both vertical and horizontal directions. The proper approach to measuring relative permeability for CO2-brine system is proposed and demonstrated. The changes in residual trapping correlated to pressure
Buchenauer, Dean A.; Karnesky, Richard A.
2015-09-01
An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.
Whenham, Natasha; Wilson, Peter W; Bain, Maureen M; Stevenson, Lynn; Dunn, Ian C
2014-03-15
The 'transiently expressed in neural precursors' (TENP) gene product is a member of the bacterial/permeability-increasing (BPI) family of antimicrobial proteins but was first identified as having a role in an early neurological event occurring in post-mitotic cells. However, recent characterisation of the egg white proteome has shown that TENP is an important egg component constituting ~0.1-0.5% of the total protein and suggesting it is expressed in the adult oviduct. In this study we confirmed quantitatively that the expression of TENP is largely confined to the tubular glands of the magnum of the oviduct, where egg white synthesis occurs, with around 10,000 times more expression than in the embryo where TENP was first identified. TENP expression is significantly increased with the administration of oestrogen or progesterone (P<0.001) and is reduced in regressed oviducts (P<0.001) demonstrating gonadal steroid control, typical of an oviduct and egg specific gene. A putative translational start site for TENP has been characterised and the evidence indicates that it is expressed as one predominant transcript. In comparison with the published sequence, insertion and deletion events have been identified causing a partial frame-shift that results in an altered amino acid sequence to that previously documented. TENP is conserved across divergent avian species being found in chicken, turkey, duck and zebra finch and its expression profile confirmed in both chicken and duck. Similarity searches have shown homology with the BPI-like family of innate immune genes, particularly with palate, lung and nasal epithelial clone (PLUNC) members of this family. We therefore believe that at least in adults the role of TENP is as a major component of egg, particularly the white and it is probable that it contributes to its antimicrobial function.
Relative potency estimation for synthetic petroleum skin carcinogens.
Holland, J M; Wolf, D A; Clark, B R
1981-01-01
A procedure for quantitative analysis of skin carcinogenesis data, for the purpose of establishing carcinogenic potency, has been applied to observations obtained from C3H mice exposed continuously to synthetic and natural petroleums. The importance of total polynuclear aromatic (PNA) content to the skin carcinogenic activity of the crude materials was also examined. Of three synthetic petroleums evaluated, all were shown capable of inducing skin neoplasms within a two-year exposure period. Under comparable exposure conditions a composite sample of five natural petroleums was noncarcinogenic. Comparison of the distributions of times to initial skin neoplasm versus dose rate, for groups exposed to synthetic fossil liquids and the reference skin carcinogen, benzo(a)pyrene, provided estimates of relative carcinotenic potency for the synthetic petroleums ranging from 1/500 to 1/1400 the potency of benzo(a)pyrene. The carcinogenic activity of a chemically isolated PNA fraction versus the crude from which it was derived suggested that this fraction was responsible for the carcinogenic activity of these synthetic petroleums in mouse skin. PMID:7238444
Relating the Hadamard Variance to MCS Kalman Filter Clock Estimation
NASA Technical Reports Server (NTRS)
Hutsell, Steven T.
1996-01-01
The Global Positioning System (GPS) Master Control Station (MCS) currently makes significant use of the Allan Variance. This two-sample variance equation has proven excellent as a handy, understandable tool, both for time domain analysis of GPS cesium frequency standards, and for fine tuning the MCS's state estimation of these atomic clocks. The Allan Variance does not explicitly converge for the nose types of alpha less than or equal to minus 3 and can be greatly affected by frequency drift. Because GPS rubidium frequency standards exhibit non-trivial aging and aging noise characteristics, the basic Allan Variance analysis must be augmented in order to (a) compensate for a dynamic frequency drift, and (b) characterize two additional noise types, specifically alpha = minus 3, and alpha = minus 4. As the GPS program progresses, we will utilize a larger percentage of rubidium frequency standards than ever before. Hence, GPS rubidium clock characterization will require more attention than ever before. The three sample variance, commonly referred to as a renormalized Hadamard Variance, is unaffected by linear frequency drift, converges for alpha is greater than minus 5, and thus has utility for modeling noise in GPS rubidium frequency standards. This paper demonstrates the potential of Hadamard Variance analysis in GPS operations, and presents an equation that relates the Hadamard Variance to the MCS's Kalman filter process noises.
Exposure corrected risk estimates for childhood product related injuries.
Senturia, Y D; Binns, H J; Christoffel, K K; Tanz, R R
1993-08-01
This study assesses the effect of exposure correction on injury risk estimates for children, using Chicago-area survey data on age-specific exposure of children to seven products: amusement park rides, sleds, bunkbeds, skateboards, fireworks, toboggans, and air guns and rifles. National Electronic Injury Surveillance System estimates for 1987 were used as numerators with two denominators: (i) uncorrected age-specific U.S. Census estimates for 1987 and (ii) these estimates corrected for exposure. Except for bunkbeds, skateboards and sleds, corrected injury risk decreased as age increased. Uncorrected population injury rates underestimated the risk posed to product-using children, especially those who are youngest and those who use skateboards.
Dunn, T.L.
1993-12-14
This multidisciplinary study is designed to provide improvements in advanced reservoir characterization techniques. This goal is to be accomplished through: (1) an examination of the spatial variation and anisotropy of relative permeability in the Tensleep Sandstone reservoirs of Wyoming; (2) the placement of that variation and anisotropy into paleogeographic, depositional, and diagenetic frameworks; (3) the development of pore-system imagery techniques for the calculation of relative permeability; and (4) reservoir simulations testing the impact of relative permeability anisotropy and spatial variation on Tensleep Sandstone reservoir enhanced oil recovery. Concurrent efforts are aimed at understanding the spatial and dynamic alteration in sandstone reservoirs that is caused by rock-fluid interaction during CO{sub 2} enhanced oil recovery processes. The work focuses on quantifying the interrelationship of fluid-rock interaction with lithologic characterization in terms of changes in relative permeability, wettability, and pore structure, and with fluid characterization in terms of changes in chemical composition and fluid properties. This work will establish new criteria for the susceptibility of Tensleep Sandstone reservoirs to formation alteration that results in a change in relative permeability and wellbore scale damage. This task will be accomplished by flow experiments using core material; examination of regional trends in water chemistry; examination of local water chemistry trends on the scale of a field; and chemical modeling of the reservoir and experimental systems in order to scale-up the experiments to reservoir conditions.
Estimated Perennial Streams of Idaho and Related Geospatial Datasets
Rea, Alan; Skinner, Kenneth D.
2009-01-01
The perennial or intermittent status of a stream has bearing on many regulatory requirements. Because of changing technologies over time, cartographic representation of perennial/intermittent status of streams on U.S. Geological Survey (USGS) topographic maps is not always accurate and (or) consistent from one map sheet to another. Idaho Administrative Code defines an intermittent stream as one having a 7-day, 2-year low flow (7Q2) less than 0.1 cubic feet per second. To establish consistency with the Idaho Administrative Code, the USGS developed regional regression equations for Idaho streams for several low-flow statistics, including 7Q2. Using these regression equations, the 7Q2 streamflow may be estimated for naturally flowing streams anywhere in Idaho to help determine perennial/intermittent status of streams. Using these equations in conjunction with a Geographic Information System (GIS) technique known as weighted flow accumulation allows for an automated and continuous estimation of 7Q2 streamflow at all points along a stream, which in turn can be used to determine if a stream is intermittent or perennial according to the Idaho Administrative Code operational definition. The selected regression equations were applied to create continuous grids of 7Q2 estimates for the eight low-flow regression regions of Idaho. By applying the 0.1 ft3/s criterion, the perennial streams have been estimated in each low-flow region. Uncertainty in the estimates is shown by identifying a 'transitional' zone, corresponding to flow estimates of 0.1 ft3/s plus and minus one standard error. Considerable additional uncertainty exists in the model of perennial streams presented in this report. The regression models provide overall estimates based on general trends within each regression region. These models do not include local factors such as a large spring or a losing reach that may greatly affect flows at any given point. Site-specific flow data, assuming a sufficient period of
The HINTS is designed to produce reliable estimates at the national and regional levels. GIS maps using HINTS data have been used to provide a visual representation of possible geographic relationships in HINTS cancer-related variables.
EPA Permeable Surface Research
EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...
Changes in airway permeability and responsiveness after exposure to ozone. [Sheep
Abraham, W.M.; Delehunt, J.C.; Yerger, L.; Marchette, B.; Oliver, W. Jr.
1984-06-01
The relationship between airway responsiveness and the permeability of histamine through the airways in conscious sheep after exposure to ozone (O/sub 3/ was examined). Airway responsiveness was assessed by measuring the change from baseline in mean pulmonary flow resistance following a controlled 2-min inhalation challenge with 1% histamine, containing 200 ..mu..Ci/ml of (/sup 3/H)histamine. The rate of appearance of the (/sup 3/H)histamine in the plasma during inhalation challenge was used to estimate airway permeability. To perturb the airways, conscious sheep were exposed to either 0.5 or 1.0 ppm O/sub 3/ for 2 hr via an endotracheal tube. Airway responsiveness and airway permeability were measured prior to and 1 day after exposure. In six sheep exposed to 0.5 ppm O/sub 3/, increased airway responsiveness and airway permeability were obseved 1 day after exposure. Four of seven sheep exposed to 1.0 ppm O/sub 3/ had enhanced airway responsiveness and airway permeability, while the remaining three sheep showed corresponding decreases in airway responsiveness and airway permeability. Since the O/sub 3/-induced directional changes in airway responsiveness paralleled the directional changes in airway permeability in both the positive and negative directions, it was concluded that changes in airway responsiveness to inhaled histamine following exposure to O/sub 3/ may be related to concomitant changes in airway permeability to this agent.
NASA Astrophysics Data System (ADS)
Austin Suthanthiraraj, Pearlson Prashanth
We present the results of an extensive experimental study on the effects of hysteresis on permanent capillary trapping and relative permeability of CO2/brine and supercritical (sc)CO2+SO2/brine systems. We performed numerous unsteady- and steady-state drainage and imbibition full-recirculation flow experiments in three different sandstone rock samples, i.e., low and high-permeability Berea, Nugget sandstones, and Madison limestone carbonate rock sample. A state-of-the-art reservoir conditions core-flooding system was used to perform the tests. The core-flooding apparatus included a medical CT scanner to measure in-situ saturations. The scanner was rotated to the horizontal orientation allowing flow tests through vertically-placed core samples with about 3.8 cm diameter and 15 cm length. Both scCO2 /brine and gaseous CO2 (gCO2)/brine fluid systems were studied. The gaseous and supercritical CO2/brine experiments were carried out at 3.46 and 11 MPa back pressures and 20 and 55°C temperatures, respectively. Under the above-mentioned conditions, the gCO2 and scCO2 have 0.081 and 0.393 gr/cm3 densities, respectively. During unsteady-state tests, the samples were first saturated with brine and then flooded with CO2 (drainage) at different maximum flow rates. The drainage process was then followed by a low flow rate (0.375 cm 3/min) imbibition until residual CO2 saturation was achieved. Wide flow rate ranges of 0.25 to 20 cm3/min for scCO2 and 0.125 to 120 cm3min for gCO2 were used to investigate the variation of initial brine saturation (Swi) with maximum CO2 flow rate and variation of trapped CO2 saturation (SCO2r) with Swi. For a given Swi, the trapped scCO2 saturation was less than that of gCO2 in the same sample. This was attributed to brine being less wetting in the presence of scCO2 than in the presence of gCO 2. During the steady-state experiments, after providing of fully-brine saturated core, scCO2 was injected along with brine to find the drainage curve and as
Calabrò, P S; Moraci, N; Suraci, P
2012-03-15
This paper presents the results of laboratory column tests aimed at defining the optimum weight ratio of zero-valent iron (ZVI)/pumice granular mixtures to be used in permeable reactive barriers (PRBs) for the removal of nickel from contaminated groundwater. The tests were carried out feeding the columns with aqueous solutions of nickel nitrate at concentrations of 5 and 50 mg/l using three ZVI/pumice granular mixtures at various weight ratios (10/90, 30/70 and 50/50), for a total of six column tests; two additional tests were carried out using ZVI alone. The most successful compromise between reactivity (higher ZVI content) and long-term hydraulic performance (higher Pumice content) seems to be given by the ZVI/pumice granular mixture with a 30/70 weight ratio.
Theoretical studies of permeability inversion from seismoelectric logs
NASA Astrophysics Data System (ADS)
Hu, H.; Guan, W.; Zhao, W.
2012-04-01
Permeability is one of the most important parameters for evaluating the level of difficulty in oil and gas exploitation. A quick, continuous and accurate in-situ estimate of reservoir permeability is highly significant. Stoneley wave logs have been used to determine formation permeability (Tang and Cheng, 1996). However, the inversion errors of this method are too big in low-permeability formations, especially in high-porosity and low-permeability formations resulting from the high clay content in pores. In this study, we propose to invert permeability by using the full waveforms of seismoelectric logs with low frequencies. This method is based on the relationship of permeability with the ratio of the electric excitation intensity to the pressure field's (REP) with respect to the Stoneley wave in seismoelectric logs. By solving the governing equations for electrokinetic coupled wavefields in homogeneous fluid-saturated porous media (Pride, 1994), we calculate the full waveforms of the borehole seismoelectric wavefields excited by a point pressure source and investigate frequency-dependent excitation intensities of the mode waves and excitation intensities of the real branch points in seismoelectric logs. It is found that the REP's phase, which reflects the phase discrepancy between the Stoneley-wave-induced electric field and the acoustic pressure, is sensitive to formation permeability. To check the relation between permeability and REP's phase qualitatively, an approximate expression of the tangent of the REP's argument is derived theoretically as tan(θEP) ≈-ωc/ω = -φη/ (2πfα ∞ρfκ0), where θEPdenotes the arguments of the REP and their principal value is the REP's phase,ω is the angular frequency,ωc is a critical angular frequency that separates the low-frequency viscous flow from the high-frequency inertial flow, φ is the porosity, α∞ is the tortuosity, κ0 is the Darcy permeability, ρf and η are the density and the viscosity of the pore
Leaf Relative Water Content Estimated from Leaf Reflectance and Transmittance
NASA Technical Reports Server (NTRS)
Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert
2016-01-01
Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. In the research we report here, we used optical polarization techniques to monitor the light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both change nonlinearly. The result show that the nonlinearities cancel in the ratio R/T, which appears linearly related to RWC for RWC less than 90%. The results suggest that potentially leaf water status and perhaps even canopy water status could be monitored starting from leaf and canopy optical measurements.
2D and 3D imaging resolution trade-offs in quantifying pore throats for prediction of permeability
Beckingham, Lauren E.; Peters, Catherine A.; Um, Wooyong; Jones, Keith W.; Lindquist, W.Brent
2013-09-03
Although the impact of subsurface geochemical reactions on porosity is relatively well understood, changes in permeability remain difficult to estimate. In this work, pore-network modeling was used to predict permeability based on pore- and pore-throat size distributions determined from analysis of 2D scanning electron microscopy (SEM) images of thin sections and 3D X-ray computed microtomography (CMT) data. The analyzed specimens were a Viking sandstone sample from the Alberta sedimentary basin and an experimental column of reacted Hanford sediments. For the column, a decrease in permeability due to mineral precipitation was estimated, but the permeability estimates were dependent on imaging technique and resolution. X-ray CT imaging has the advantage of reconstructing a 3D pore network while 2D SEM imaging can easily analyze sub-grain and intragranular variations in mineralogy. Pore network models informed by analyses of 2D and 3D images at comparable resolutions produced permeability esti- mates with relatively good agreement. Large discrepancies in predicted permeabilities resulted from small variations in image resolution. Images with resolutions 0.4 to 4 lm predicted permeabilities differ- ing by orders of magnitude. While lower-resolution scans can analyze larger specimens, small pore throats may be missed due to resolution limitations, which in turn overestimates permeability in a pore-network model in which pore-to-pore conductances are statistically assigned. Conversely, high-res- olution scans are capable of capturing small pore throats, but if they are not actually flow-conducting predicted permeabilities will be below expected values. In addition, permeability is underestimated due to misinterpreting surface-roughness features as small pore throats. Comparison of permeability pre- dictions with expected and measured permeability values showed that the largest discrepancies resulted from the highest resolution images and the best predictions of
NASA Astrophysics Data System (ADS)
Pape, H.; Clauser, C.; Iffland, J.
Permeability is one of the key rock properties for the management of hydrocarbon and geothermal reservoirs as well as for aquifers. The fundamental equation for estimating permeability is the Kozeny-Carman equation. It is based on a capillary bundle model and relates permeability to porosity, tortuosity and an effective hydraulic pore radius which is defined by this equation. Whereas in clean sands the effective pore radius can be replaced by the specific surface or by the grain radius in a simple way, the resulting equations for permeability cannot be applied to consolidated rocks. Based on a fractal model for porous media, equations were therefore developed which adjust the measure of the specific surface and of the grain radius to the resolution length appropriate for the hydraulic process. These equations are calibrated by a large data set for permeability, formation factor, and porosity determined on sedimentary rocks. This fractal model yields tortuosity and effective pore radius as functions of porosity as well as a general permeability-porosity relationship, the coefficients of which are characteristic for different rock types. It can be applied to interpret the diagenetic evolution of the pore space of sedimentary rocks due to mechanical and chemical compaction with respect to porosity and permeability.
Committee neural network model for rock permeability prediction
NASA Astrophysics Data System (ADS)
Bagheripour, Parisa
2014-05-01
Quantitative formulation between conventional well log data and rock permeability, undoubtedly the most critical parameter of hydrocarbon reservoir, could be a potent tool for solving problems associated with almost all tasks involved in petroleum engineering. The present study proposes a novel approach in charge of the quest for high-accuracy method of permeability prediction. At the first stage, overlapping of conventional well log data (inputs) was eliminated by means of principal component analysis (PCA). Subsequently, rock permeability was predicted from extracted PCs using multi-layer perceptron (MLP), radial basis function (RBF), and generalized regression neural network (GRNN). Eventually, a committee neural network (CNN) was constructed by virtue of genetic algorithm (GA) to enhance the precision of ultimate permeability prediction. The values of rock permeability, derived from the MPL, RBF, and GRNN models, were used as inputs of CNN. The proposed CNN combines results of different ANNs to reap beneficial advantages of all models and consequently producing more accurate estimations. The GA, embedded in the structure of the CNN assigns a weight factor to each ANN which shows relative involvement of each ANN in overall prediction of rock permeability from PCs of conventional well logs. The proposed methodology was applied in Kangan and Dalan Formations, which are the major carbonate reservoir rocks of South Pars Gas Field-Iran. A group of 350 data points was used to establish the CNN model, and a group of 245 data points was employed to assess the reliability of constructed CNN model. Results showed that the CNN method performed better than individual intelligent systems performing alone.
Anderson, L.A.
1994-09-01
Core samples were measured for bulk density, grain density, porosity, resistivity, and water permeability as part of a comprehensive geologic investigation designed to determine the suitability of Yucca Mountain as a site for the containment of high-level radioactive waste products. The cores were selected at the drill sites so as to be representative of the major lithologic variations observed within stratigraphic units of the Paintbrush Tuff, Calico Hills Tuff, Crater Flat Tuff, Lithic Ridge Tuff, and Older Tuffs. Dry and saturated bulk density, grain density, and porosity measurements were made on the core samples principally to establish that a reasonable uniformity exists in the textural and mineral character of the sample pairs. Electrical resistivity measured on sample pairs tended to be lower along the plane transverse to the vertical axis of the drill core herein referred to as the horizontal plane. Permeability values, ranging from virtually zero (<.02 microdarcies) to over 200 millidarcies, also indicate a preferential flow direction along the horizontal plane of the individual tuff units. Permeability decreases with flow duration in all but the non-welded tuffs as unconsolidated particles within the pore network are repositioned so as to impede the continued flow of water through the rock. Reversing flow direction initially restores the permeability of the rock to its original or maximum value.
Compact rock material gas permeability properties
NASA Astrophysics Data System (ADS)
Wang, Huanling; Xu, Weiya; Zuo, Jing
2014-09-01
Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO2, shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10-19 m2; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10-17 m2; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens' permeability evolution is related to the relative particle movements and microcrack closure.
Pressure sensitivity of low permeability sandstones
Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.
1987-01-01
Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.
Inference of permeability heterogeneity from joint inversion of transient flow and temperature data
NASA Astrophysics Data System (ADS)
Zhang, Zhishuai; Jafarpour, Behnam; Li, Lianlin
2014-06-01
Characterization of the rock permeability distribution in compartmentalized deep aquifers, enhanced geothermal systems, and hydrocarbon reservoirs is important for predicting the flow and transport behavior in these formations. Reliable prediction of the fluid flow and transport processes can, in turn, lead to effective development of the subsurface energy and environmental resources. In deep formations where thermal gradients are significant, the transient temperature data can provide valuable information about the permeability distribution with depth and about the vertical fluid displacement. This paper examines the importance of temperature data in resolving the distribution of permeability with depth by jointly, and individually, integrating the transient temperature and flow data. We demonstrate that when estimating permeability distributions in deep geothermal reservoirs, incorporating temperature data can increase the resolution of the permeability distribution profile with depth. To illustrate the importance of temperature measurements, we adopt a coupled transient heat and fluid flow as a forward model to predict the heat and fluid transport in a geothermal reservoir and develop an adjoint model for efficient computation of the gradient information for model calibration. We perform a series of numerical experiments for integration of flow and pressure data alone, temperature data alone, and flow and pressure jointly with temperature data. In each case, we apply the maximum A-posteriori (MAP) method and the randomized maximum likelihood (RML) method for inversion and uncertainty quantification. Analysis of the sensitivity of temperature and production data to heterogeneous permeability distributions reveals that the temperature of fluid, even when measured at the surface, is sensitive to the permeability distribution in the vertical extent of the reservoir. Hence, temperature measurements can be augmented with flow-related data to enhance the resolution of
Dunn, T.L.
1996-10-01
This multidisciplinary study was designed to provide improvements in advanced reservoir characterization techniques. This goal was accomplished through: (1) an examination of the spatial variation and anisotropy of relative permeability in the Tensleep Sandstone reservoirs of Wyoming; (2) the placement of that variation and anisotropy into paleogeographic, and depositional regional frameworks; (3) the development of pore-system imagery techniques for the calculation of relative permeability; and (4) reservoir simulations testing the impact of relative permeability anisotropy and spatial variation on Tensleep Sandstone reservoir enhanced oil recovery. Concurrent efforts were aimed at understanding the spatial and dynamic alteration in sandstone reservoirs that is caused by rock-fluid interaction during CO{sub 2} enhanced oil recovery processes. The work focused on quantifying the interrelationship of fluid-rock interaction with lithologic characterization and with fluid characterization in terms of changes in chemical composition and fluid properties. This work establishes new criteria for the susceptibility of Tensleep Sandstone reservoirs to formation alteration that results in wellbore scale damage. This task was accomplished by flow experiments using core material; examination of regional trends in water chemistry; examination of local water chemistry trends the at field scale; and chemical modeling of both the experimental and reservoir systems.
Dunn, T.L.
1995-07-01
The principal focus of this project is to evaluate the importance of relative permeability anisotropy with respect to other known geologic and engineering production concepts. This research is to provide improved strategies for enhanced oil recovery from the Tensleep Sandstone oil reservoirs in the Bighorn and Wind River basins, Wyoming. The Tensleep Sandstone contains the largest potential reserves within reservoirs which are candidates for EOR processes in the State of Wyoming. Although this formation has produced billions of barrels of oil, in some fields, as little as one in seven barrels of discovered oil is recoverable by current primary and secondary techniques. Because of the great range of {degree}API gravities of the oils produced from the Tensleep Sandstone reservoirs, the proposed study concentrates on establishing an understanding of the spatial variation and anisotropy of relative permeability within the Tensleep Sandstone. This research is to associate those spatial distributions and anisotropies with the depositional subfacies and zones of diagenetic alteration found within the Tensleep Sandstone. In addition, these studies are being coupled with geochemical modeling and coreflood experiments to investigate the potential for wellbore scaling and formation damage anticipated during EOR processes (e.g., C0{sub 2} flooding). This multidisciplinary project will provide a regional basis for EOR strategies which can be clearly mapped and efficiently applied to the largest potential target reservoir in the State of Wyoming. Additionally, the results of this study have application to all eolian reservoirs through the correlations of relative permeability variation and anisotropy with eolian depositional lithofacies.
Cheng, Hao; Wang, You-Shao; Ye, Zhi-Hong; Chen, Dan-Ting; Wang, Yu-Tu; Peng, Ya-Lan; Wang, Li-Ying
2012-05-01
Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface. PMID:22361050
Cheng, Hao; Wang, You-Shao; Ye, Zhi-Hong; Chen, Dan-Ting; Wang, Yu-Tu; Peng, Ya-Lan; Wang, Li-Ying
2012-05-01
Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface.
The Relation between Factor Score Estimates, Image Scores, and Principal Component Scores
ERIC Educational Resources Information Center
Velicer, Wayne F.
1976-01-01
Investigates the relation between factor score estimates, principal component scores, and image scores. The three methods compared are maximum likelihood factor analysis, principal component analysis, and a variant of rescaled image analysis. (RC)
Permeability Barrier Generation in the Martian Lithosphere
NASA Astrophysics Data System (ADS)
Schools, Joe; Montési, Laurent
2015-11-01
Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability
Lunar electrical conductivity and magnetic permeability
NASA Technical Reports Server (NTRS)
Dyal, P.; Parkin, C. W.; Daily, W. D.
1975-01-01
Improved analytical techniques are applied to a large Apollo magnetometer data set to yield values of electroconductivity, temperature, magnetic permeability, and iron abundance. Average bulk electroconductivity of the moon is calculated to be .0007 mho/m; a rapid increase with depth to about .003 mho/m within 250 km is indicated. The temperature profile, obtained from the electroconductivity profile for olivine, indicates high lunar temperatures at relatively shallow depths. Magnetic permeability of the moon relative to its environment is calculated to be 1.008 plus or minus .005; a permeability relative to free space of 1.012 plus 0.011, minus 0.008 is obtained. Lunar iron abundances corresponding to this permeability value are 2.5 plus 2.3, minus 1.7 wt% free iron and 5.0-13.5 wt% total iron for a moon composed of a combination of free iron, olivine, and orthopyroxene.
Permeability of edible coatings.
Mishra, B; Khatkar, B S; Garg, M K; Wilson, L A
2010-01-01
The permeabilities of water vapour, O2 and CO2 were determined for 18 coating formulations. Water vapour transmission rate ranged from 98.8 g/m(2).day (6% beeswax) to 758.0 g/m(2).day (1.5% carboxymethyl cellulose with glycerol). O2 permeability at 14 ± 1°C and 55 ± 5% RH ranged from 1.50 to 7.95 cm(3)cm cm(-2)s(-1)Pa(-1), with CO2 permeability 2 to 6 times as high. Permeability to noncondensable gases (O2 and CO2) was higher for hydrophobic (peanut oil followed by beeswax) coatings as compared to hydrophilic (whey protein concentrate and carboxymethyl cellulose).
Particle filter-based relative rolling estimation algorithm for non-cooperative infrared spacecraft
NASA Astrophysics Data System (ADS)
Li, Zhengzhou; Ge, Fengzeng; Chen, Wenhao; Shao, Wanxing; Liu, Bing; Cheng, Bei
2016-09-01
The issue of feature point mismatching among infrared image sequence would bring big challenge to estimating the relative motion of non-cooperative spacecraft for it couldn't provide the prior knowledge about its geometric structure and motion pattern. The paper introduces particle filter to precisely match the feature points within a desired region predicted by a kinetic equation, and presents a least square estimation-based algorithm to measure the relative rolling motion of non-cooperative spacecraft. The state transition equation and the measurement update equation of non-cooperative spacecraft are represented by establishing its kinetic equations, and then the relative pose measurement is converted to the maximum posteriori probability estimation via assuming the uncertainties about geometric structure and motion pattern as random and time-varying variables. These uncertainties would be interpreted and even solved through continuously measuring the image feature points of the rotating non-cooperative infrared spacecraft. Subsequently, the feature point is matched within a predicted region among sequence infrared image using particle filter algorithm to overcome the position estimation noise caused by the uncertainties of geometric structure and motion pattern. Finally, the position parameters including rotation motion are estimated by means of solving the minimum error of feature point mismatching using least square estimate theory. Both simulated and real infrared image sequences are induced in the experiment to evaluate the performance of the relative rolling estimation, and the experimental data show that the rolling motion estimated by the proposed algorithm is more robust to the feature extraction noise and various rotation speed. Meanwhile, the relative rolling estimation error would increase dramatically with distance and rotation speed increasing.
[Application of spatial relative risk estimation in communicable disease risk evaluation].
Zhang, Yewu; Guo, Qing; Wang, Xiaofeng; Yu, Meng; Su, Xuemei; Dong, Yan; Zhang, Chunxi
2015-05-01
This paper summaries the application of adaptive kernel density algorithm in the spatial relative risk estimation of communicable diseases by using the reported data of infectious diarrhea (other than cholera, dysentery, typhoid and paratyphoid) in Ludian county and surrounding area in Yunnan province in 2013. Statistically significant fluctuations in an estimated risk function were identified through the use of asymptotic tolerance contours, and finally these data were visualized though disease mapping. The results of spatial relative risk estimation and disease mapping showed that high risk areas were in southeastern Shaoyang next to Ludian. Therefore, the spatial relative risk estimation of disease by using adaptive kernel density algorithm and disease mapping technique is a powerful method in identifying high risk population and areas.
[Application of spatial relative risk estimation in communicable disease risk evaluation].
Zhang, Yewu; Guo, Qing; Wang, Xiaofeng; Yu, Meng; Su, Xuemei; Dong, Yan; Zhang, Chunxi
2015-05-01
This paper summaries the application of adaptive kernel density algorithm in the spatial relative risk estimation of communicable diseases by using the reported data of infectious diarrhea (other than cholera, dysentery, typhoid and paratyphoid) in Ludian county and surrounding area in Yunnan province in 2013. Statistically significant fluctuations in an estimated risk function were identified through the use of asymptotic tolerance contours, and finally these data were visualized though disease mapping. The results of spatial relative risk estimation and disease mapping showed that high risk areas were in southeastern Shaoyang next to Ludian. Therefore, the spatial relative risk estimation of disease by using adaptive kernel density algorithm and disease mapping technique is a powerful method in identifying high risk population and areas. PMID:26080648
Cárdenas-Rodríguez, Julio; Howison, Christine M.; Matsunaga, Terry O.; Pagel, Mark D.
2013-01-01
Dynamic Contrast Enhancement (DCE) MRI has been used to measure the kinetic transport constant, Ktrans, which is used to assess tumor angiogenesis and the effects of anti-angiogenic therapies. Standard DCE MRI methods must measure the pharmacokinetics of a contrast agent in the blood stream, known as the Arterial Input Function (AIF), which is then used as a reference for the pharmacokinetics of the agent in tumor tissue. However, the AIF is difficult to measure in pre-clinical tumor models and in patients. Moreover the AIF is dependent on the Fahraeus effect that causes a highly variable hematocrit (Hct) in tumor microvasculature, leading to erroneous estimates of Ktrans. To overcome these problems, we have developed the Reference Agent Model (RAM) for DCE MRI analyses, which determines the ratio of Ktrans values of two contrast agents that are simultaneously co-injected and detected during a single DCE-MRI scan session. The RAM obviates the need to monitor the AIF because one contrast agent effectively serves as an internal reference in the tumor tissue for the other agent, and it also eliminates the systematic errors in the estimated Ktrans caused by assuming an erroneous Hct. Simulations demonstrated that the RAM can accurately and precisely estimate the relative Ktrans (RKtrans) of two agents. To experimentally evaluate the utility of RAM for analyzing DCE MRI results, we optimized a previously reported multiecho 19F MRI method to detect two perfluorocarbon contrast agents that were co-injected during a single in vivo study and selectively detected in the same tumor location. The results demonstrated that RAM determined RKtrans with excellent accuracy and precision. PMID:23583323
Exploring the scale-dependent permeability of fractured andesite
NASA Astrophysics Data System (ADS)
Heap, Michael J.; Kennedy, Ben M.
2016-08-01
Extension fractures in volcanic systems exist on all scales, from microscopic fractures to large fissures. They play a fundamental role in the movement of fluids and distribution of pore pressure, and therefore exert considerable influence over volcanic eruption recurrence. We present here laboratory permeability measurements for porous (porosity = 0.03-0.6) andesites before (i.e., intact) and after failure in tension (i.e., the samples host a throughgoing tensile fracture). The permeability of the intact andesites increases with increasing porosity, from 2 ×10-17 to 5 ×10-11 m2. Following fracture formation, the permeability of the samples (the equivalent permeability) falls within a narrow range, 2- 6 ×10-11 m2, regardless of their initial porosity. However, laboratory measurements on fractured samples likely overestimate the equivalent permeability due to the inherent scale-dependence of permeability. To explore this scale-dependence, we first determined the permeability of the tensile fractures using a two-dimensional model that considers flow in parallel layers. Our calculations highlight that tensile fractures in low-porosity samples are more permeable (as high as 3.5 ×10-9 m2) than those in high-porosity samples (as low as 4.1 ×10-10 m2), a difference that can be explained by an increase in fracture tortuosity with porosity. We then use our fracture permeability data to model the equivalent permeability of fractured rock (with different host rock permeabilities, from 10-17 to 10-11 m2) with increasing lengthscale. We highlight that our modelling approach can be used to estimate the equivalent permeability of numerous scenarios at andesitic stratovolcanoes in which the fracture density and width and host rock porosity or permeability are known. The model shows that the equivalent permeability of fractured andesite depends heavily on the initial host rock permeability and the scale of interest. At a given lengthscale, the equivalent permeability of high-permeability
NASA Astrophysics Data System (ADS)
Gibbons, S. J.; Pabian, F.; Näsholm, S. P.; Kværna', T.; Mykkeltveit, S.
2016-10-01
Declared North Korean nuclear tests in 2006, 2009, 2013, and 2016 were observed seismically at regional and teleseismic distances. Waveform similarity allows the events to be located relatively with far greater accuracy than the absolute locations can be determined from seismic data alone. There is now significant redundancy in the data given the large number of regional and teleseismic stations that have recorded multiple events, and relative location estimates can be confirmed independently by performing calculations on many mutually exclusive sets of measurements. Using a 1-dimensional global velocity model, the distances between the events estimated using teleseismic P phases are found to be approximately 25% shorter than the distances between events estimated using regional Pn phases. The 2009, 2013, and 2016 events all take place within 1 km of each other and the discrepancy between the regional and teleseismic relative location estimates is no more than about 150 m. The discrepancy is much more significant when estimating the location of the more distant 2006 event relative to the later explosions with regional and teleseismic estimates varying by many hundreds of meters. The relative location of the 2006 event is challenging given the smaller number of observing stations, the lower signal-to-noise ratio, and significant waveform dissimilarity at some regional stations. The 2006 event is however highly significant in constraining the absolute locations in the terrain at the Punggye-ri test-site in relation to observed surface infrastructure. For each seismic arrival used to estimate the relative locations, we define a slowness scaling factor which multiplies the gradient of seismic traveltime versus distance, evaluated at the source, relative to the applied 1-d velocity model. A procedure for estimating correction terms which reduce the double-difference time residual vector norms is presented together with a discussion of the associated uncertainty. The
Fluid permeability of deformable fracture networks
Brown, S.R.; Bruhn, R.L.
1997-04-01
The authors consider the problem of defining the fracture permeability tensor for each grid lock in a rock mass from maps of natural fractures. For this purpose they implement a statistical model of cracked rock due to M. Oda [1985], where the permeability tensor is related to the crack geometry via a volume average of the contribution from each crack in the population. In this model tectonic stress is implicitly coupled to fluid flow through an assumed relationship between crack aperture and normal stress across the crack. The authors have included the following enhancements to the basic model: (1) a realistic model of crack closure under stress has been added along with the provision to apply tectonic stresses to the fracture system in any orientation, the application of stress results in fracture closure and consequently a reduction in permeability; (2) the fracture permeability can be superimposed onto an arbitrary anisotropic matrix permeability; (3) the fracture surfaces are allowed to slide under the application of shear stress, causing fractures to dilate and result in a permeability increase. Through an example, the authors demonstrate that significant changes in permeability magnitudes and orientations are possible when tectonic stress is applied to a fracture system.
Oxygen Evolution and the Permeability of the Outer Envelope of Isolated Whole Chloroplasts 1
Robinson, J. Michael; Stocking, C. R.
1968-01-01
A rapid oxygraph method of studying the permeability of the envelope of isolated chloroplasts was used. The outer envelope of aqueously isolated whole spinach (Spinacia oleracea L.) chloroplasts in buffer is readily permeable to 3-phosphoglyceric acid, which induces an immediate light dependent oxygen evolution. This light dependent oxygen evolution was completely eliminated by swelling these plastids in an osmotically dilute solution. Exogenous adenosine diphosphate, but not inorganic phosphate, strongly stimulated this oxygen evolution. This indicated that the chloroplast envelope is relatively permeable to adenosine diphosphate. Oxygen evolution and swelling studies indicated that the chloroplast envelope is relatively impermeable to NADP and to ferredoxin. A method is described whereby the percent of whole chloroplasts present in a chloroplast preparation may be rapidly estimated. PMID:16656943
Skewness of cloud droplet spectrum and an improved estimation for its relative dispersion
NASA Astrophysics Data System (ADS)
Liu, Yu; Lu, Chunsong; Li, Weiliang
2016-05-01
The relative dispersion of the cloud droplet spectrum is a very important parameter in describing and modeling cloud microphysical processes. Based on the definition of skewness as well as theoretical and data analyses, a linear fitting relationship (α = 2.91ɛ-0.59) between skewness (α) and relative dispersion (ɛ) is established and a new method is developed to estimate the relative dispersion of the cloud droplet spectrum. The new method does not depend on any assumption of a particular distribution for the cloud droplet spectrum and has broader applicability than the previous methods. Comparisons of the three methods for the relative dispersion with the observed data supported the following conclusions. (1) The skewness of the cloud droplet spectrum is asymmetrically distributed. An assumption of zero skewness in quantifying the relative dispersion inevitably results in relatively large deviations from the observations. Errors of the estimated relative dispersion due to the omission of the skewness term are not solely related to the skewness, but rather to the product of the skewness and relative dispersion. (2) The use of the assumption that the cloud droplet spectrum takes a gamma distribution is similar to the assumption that the skewness is twice the relative dispersion. This leads to a better accuracy in estimating the relative dispersion than that with zero skewness assumption. (3) Comparisons with observations show that the new method is more accurate than the one under gamma distribution assumption and is the best among all the three methods. (4) It is believed that finding a better correlation between the skewness and the relative dispersion would further reduce the deviations for the estimated relative dispersion.
NASA Technical Reports Server (NTRS)
Wahba, Grace; Deepak, A. (Editor)
1988-01-01
The problem of merging direct and remotely sensed (indirect) data with forecast data to get an estimate of the present state of the atmosphere for the purpose of numerical weather prediction is examined. To carry out this merging optimally, it is necessary to provide an estimate of the relative weights to be given to the observations and forecast. It is possible to do this dynamically from the information to be merged, if the correlation structure of the errors from the various sources is sufficiently different. Some new statistical approaches to doing this are described, and conditions quantified in which such estimates are likely to be good.
Estimation of straylight in the eye and its relation to visual function
NASA Astrophysics Data System (ADS)
Ayama, Miyoshi; Yamazaki, Ryosuke; Nakanoya, Shin-ichi; Tashiro, Tomonori; Ishikawa, Tomoharu; Ohnuma, Kazuhiko; Shinoda, Hiroyuki; Araki, Keisuke
2015-04-01
Relative amount of straylight in the eye of individual observers was estimated using a psychophysical method proposed by Shinoda et al. Asymptotic illuminance of disturbing light presented in front of observer's eye to blur different sizes of the gap in the Landolt C was measured with the haze filters of which haze factors were known. From the relation between the haze factor and the asymptotic illuminance of the disturbing light for the average observer, the relative haze factor of each observer's eye was estimated. White and colored LEDs ( λ p = 645, 530, and 480 nm) were used as the disturbing lights. The four different disturbing lights showed similar tendencies among nine young observers with healthy eyes. The ability to read colored characters was also examined for six observers in the same group. A negative correlation was found between the estimation of straylight in the eye and reading performance.
Permeability of Two Parachute Fabrics - Measurements, Modeling, and Application
NASA Technical Reports Server (NTRS)
Cruz, Juan R.; O'Farrell, Clara; Hennings, Elsa; Runnells, Paul
2016-01-01
Two parachute fabrics, described by Parachute Industry Specifications PIA-C-7020D Type I and PIA-C-44378D Type I, were tested to obtain their permeabilities in air (i.e., flow-through volume of air per area per time) over the range of differential pressures from 0.146 psf (7 Pa) to 25 psf (1197 Pa). Both fabrics met their specification permeabilities at the standard differential pressure of 0.5 inch of water (2.60 psf, 124 Pa). The permeability results were transformed into an effective porosity for use in calculations related to parachutes. Models were created that related the effective porosity to the unit Reynolds number for each of the fabrics. As an application example, these models were used to calculate the total porosities for two geometrically-equivalent subscale Disk-Gap-Band (DGB) parachutes fabricated from each of the two fabrics, and tested at the same operating conditions in a wind tunnel. Using the calculated total porosities and the results of the wind tunnel tests, the drag coefficient of a geometrically-equivalent full-scale DGB operating on Mars was estimated.
Dexter, Troy A; Kowalewski, Michał
2013-12-01
Quantitative estimates of growth rates can augment ecological and paleontological applications of body-size data. However, in contrast to body-size estimates, assessing growth rates is often time-consuming, expensive, or unattainable. Here we use an indirect approach, a jackknife-corrected parametric bootstrap, for efficient approximation of growth rates using nearest living relatives with known age-size relationships. The estimate is developed by (1) collecting a sample of published growth rates of closely related species, (2) calculating the average growth curve using those published age-size relationships, (3) resampling iteratively these empirically known growth curves to estimate the standard errors and confidence bands around the average growth curve, and (4) applying the resulting estimate of uncertainty to bracket age-size relationships of the species of interest. This approach was applied to three monophyletic families (Donacidae, Mactridae, and Semelidae) of mollusk bivalves, a group characterized by indeterministic shell growth, but widely used in ecological, paleontological, and geochemical research. The resulting indirect estimates were tested against two previously published geochemical studies and, in both cases, yielded highly congruent age estimates. In addition, a case study in applied fisheries was used to illustrate the potential of the proposed approach for augmenting aquaculture management practices. The resulting estimates of growth rates place body size data in a constrained temporal context and confidence intervals associated with resampling estimates allow for assessing the statistical uncertainty around derived temporal ranges. The indirect approach should allow for improved evaluation of diverse research questions, from sustainability of industrial shellfish harvesting to climatic interpretations of stable isotope proxies extracted from fossil skeletons.
Fracture and healing in magmas: a dual role on permeability evolution
NASA Astrophysics Data System (ADS)
Lamur, Anthony; Lavallée, Yan; Wall, Richard; Ashworth, James; Kendrick, Jackie; Wadsworth, Fabian
2016-04-01
The development of a permeable network in silicic volcanic conduits controls outgassing and plays a major role on the subsequent eruptive behaviour. Efficient outgassing, at higher permeabilities, is achieved through the coalescence of pores and fractures. Whilst the relationship between permeability and increasing connected porosity is now relatively well constrained, the effects of fractures have, on the other hand, rarely been investigated. Here, we present the results of an experimental study focusing on the impacts of tensile fracturing and healing on permeability. Permeability measurements have been performed on over 60 disk-shaped samples (26 mm diameter, 13 mm thickness) with connected porosities ranging from 2 to 45%. Our results for unfractured samples display the same porosity-permeability trend as previous studies and permeabilities span from 10-15 at low porosities to over 5x10-12 m2 at higher porosities. These samples were then broken via Brazilian tests and the resultant permeability of the rocks were then measured across the fracture zone. Whilst high porosity samples reached permeabilities of about 5x10-10 m2 (2 orders of magnitude higher than intact samples), low porosity samples, on the other hand, reached permeabilities around 5x10-12 m2 (more than 3 orders of magnitude above intact samples). Our results show that fracturing favours the development of a permeable network that adheres to a different permeability-porosity relationship than previously presented, and that this effect is emphasized in magmas with low connected porosities. The effect of fracture healing by diffusion on permeability has been investigated through a series of experiments on borosilicate standard glass (NIST 717a). These experiments were conducted at 560oC (viscosity of 1010.33 Pa.s) on pairs of columns pressed and held in contact at constant load for times varying between 0.5s and 15000 s before being pulled apart at a strain rate of 10-3s-1. Using Maxwell's theory of
Mowers, T.T.; Budd, D.A.
1996-03-01
Calcite cementation is often an important factor in the evolution of reservoir pore systems. Although petrographically obvious, the effect that cementation has had on the petrophysical properties of a pore system may be difficult to evaluate quantitatively. To this end, a computer-assisted petrographic image analysis (PIA) technique was developed to quantify porosity and permeability reduction due to calcite cementation. With this technique, pore area and specific surface of the extant pore system are measured from digital images of core-plug thin sections. Porosity is estimated from the measurements of pore area, and an empirical equation relating pore area and specific surface to core permeability is derived using the Kozeny-Carman expression. In this manner, a permeability model is developed for the pore system in question, thus providing a means of estimating permeability from PIA measurements. To estimate the porosity and permeability of the precalcite pore system, calcite cement is discriminated from the same digital images and analyzed as pore space. This effectively backstrips calcite from the extant pore network to yield the precursor pore network. A comparison of the porosity and permeability of the extant and precalcite pore networks shows the quantitative significance of calcite cementation. This technique is demonstrated using two dolomite reservoirs that exhibit varying amounts of late-stage calcite cements: Little Sand Draw field, Wyoming, and Bindley field, Kansas. Calcite cement was found to be minor and restricted to moldic pores in Little Sand Draw dolomites, resulting in less than a twofold change in permeability. In contrast, late calcite cements are somewhat more abundant in Bindley dolomites, but more importantly, they occupy intercrystalline pores as well as moldic pores. The net effect was a 10- to 1000-fold decrease in permeability and the localized destruction of reservoir-quality rocks in Bindley field.
NASA Astrophysics Data System (ADS)
Peng, Sheng; Marone, Federica; Dultz, Stefan
2014-03-01
Resolution selection when using X-ray microcomputed tomography should be made based on the compromise between accuracy and representativeness. The question is then how accurate is accurate enough, that is, how small a pore is small enough to be ignored without generating misleading results on pore representation and subsequent flow properties such as permeability. In this study, synchrotron X-ray microcomputed tomographic scans of a Berea sandstone sample were acquired for two resolutions (with 1.85 and 5.92 μm pixel width). Higher resolution images resolve more small pores, and have similar large pores as the lower resolution images. Pore characterization and permeability estimation were conducted based on these two sets of images. The pore parameters and permeability were also measured for another larger sample from the same rock fragment through laboratory experiments. The comparison between the different resolution image analyses and the laboratory measurement indicates that small pores contribute to larger porosity, smaller tortuosity, and larger surface area, but do not influence permeability significantly. Therefore, relatively low resolution (pixel width up to 5.92 μm) can be used for Berea sandstone when permeability is the focus. However, use of even lower resolution needs to be careful since lower resolution not only excludes more small pores, but also has the potential to overestimate the pore size and thereby the permeability. Kozeny-Carman equation was used to estimate the permeability with geometric and diffusional tortuosity. The results indicate that the latter tortuosity can serve better for the permeability estimation than the former.
Variability of permeability with diameter of conduit
NASA Astrophysics Data System (ADS)
Adegoke, J. A.; Olowofela, J. A.
2008-05-01
An entry length is always observed before laminar flow is achieved in fluid flowing in a conduit. This depends on the Reynolds number of the flow and the degree of smoothness of the conduit. This work examined this region and the point where laminar flow commences in the context of flow through conduit packed with porous material like beads, of known porosity. Using some theoretical assumptions, it is demonstrated that permeability varies from zero at wall-fluid boundary to maximum at mid-stream, creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus porosity revealed that they are linearly related.
Permeability of rayon based polymer composites
NASA Technical Reports Server (NTRS)
Stokes, E. H.
1992-01-01
Several types of anomalous rayon based phenolic behavior have been observed in post-fired nozzles and exit cones. Many of these events have been shown to be related to the development of internal gas pressure within the material. The development of internal gas pressure is a function of the amount of gas produced within the material and the rate at which that gas is allowed to escape. The latter property of the material is referred to as the material's permeability. The permeability of two dimensional carbonized rayon based phenolic composites is a function of material direction, temperature, and stress/strain state. Recently significant differences in the permeability of these materials has been uncovered which may explain their inconsistent performance. This paper summarizes what is known about the permeability of these materials to date and gives possible implications of these finding to the performance of these materials in an ablative environment.
Permeability-porosity relationships of subduction zone sediments
Gamage, K.; Screaton, E.; Bekins, B.; Aiello, I.
2011-01-01
Permeability-porosity relationships for sediments from the northern Barbados, Costa Rica, Nankai, and Peru subduction zones were examined based on sediment type, grain size distribution, and general mechanical and chemical compaction history. Greater correlation was observed between permeability and porosity in siliciclastic sediments, diatom oozes, and nannofossil chalks than in nannofossil oozes. For siliciclastic sediments, grouping of sediments by percentage of clay-sized material yields relationships that are generally consistent with results from other marine settings and suggests decreasing permeability as percentage of clay-sized material increases. Correction of measured porosities for smectite content improved the correlation of permeability-porosity relationships for siliciclastic sediments and diatom oozes. The relationship between permeability and porosity for diatom oozes is very similar to the relationship in siliciclastic sediments, and permeabilities of both sediment types are related to the amount of clay-size particles. In contrast, nannofossil oozes have higher permeability values by 1.5 orders of magnitude than siliciclastic sediments of the same porosity and show poor correlation between permeability and porosity. More indurated calcareous sediments, nannofossil chalks, overlap siliciclastic permeabilities at the lower end of their measured permeability range, suggesting similar consolidation patterns at depth. Thus, the lack of correlation between permeability and porosity for nannofossil oozes is likely related to variations in mechanical and chemical compaction at shallow depths. This study provides the foundation for a much-needed global database with fundamental properties that relate to permeability in marine settings. Further progress in delineating controls on permeability requires additional carefully documented permeability measurements on well-characterized samples. ?? 2010 Elsevier B.V.
Estimating one's own and one's relatives' multiple intelligence: a study from Argentina.
Furnham, Adrian; Chamorro-Premuzic, Tomas
2005-05-01
Participants from Argentina (N = 217) estimated their own, their partner's, their parents' and their grandparents' overall and multiple intelligences. The Argentinean data showed that men gave higher overall estimates than women (M = 110.4 vs. 105.1) as well as higher estimates on mathematical and spatial intelligence. Participants thought themselves slightly less bright than their fathers (2 IQ points) but brighter than their mothers (6 points), their grandfathers (8 points), but especially their grandmothers (11 points). Regressions showed that participants thought verbal and mathematical IQ to be the best predictors of overall IQ. Results were broadly in agreement with other studies in the area. A comparison was also made with British data using the same questionnaire. British participants tended to give significantly higher self-estimates than for relatives, though the pattern was generally similar. Results are discussed in terms of the studies in the field.
Estimating one's own and one's relatives' multiple intelligence: a study from Argentina.
Furnham, Adrian; Chamorro-Premuzic, Tomas
2005-05-01
Participants from Argentina (N = 217) estimated their own, their partner's, their parents' and their grandparents' overall and multiple intelligences. The Argentinean data showed that men gave higher overall estimates than women (M = 110.4 vs. 105.1) as well as higher estimates on mathematical and spatial intelligence. Participants thought themselves slightly less bright than their fathers (2 IQ points) but brighter than their mothers (6 points), their grandfathers (8 points), but especially their grandmothers (11 points). Regressions showed that participants thought verbal and mathematical IQ to be the best predictors of overall IQ. Results were broadly in agreement with other studies in the area. A comparison was also made with British data using the same questionnaire. British participants tended to give significantly higher self-estimates than for relatives, though the pattern was generally similar. Results are discussed in terms of the studies in the field. PMID:15875453
Friedman, Alinda; Montello, Daniel R
2006-03-01
The authors examined whether absolute and relative judgments about global-scale locations and distances were generated from common representations. At the end of a 10-week class on the regional geography of the United States, participants estimated the latitudes of 16 North American cities and all possible pairwise distances between them. Although participants were relative experts, their latitude estimates revealed the presence of psychologically based regions with large gaps between them and a tendency to stretch North America southward toward the equator. The distance estimates revealed the same properties in the representation recovered via multidimensional scaling. Though the aggregated within- and between-regions distance estimates were fitted by Stevens's law (S. S. Stevens, 1957), this was an averaging artifact: The appropriateness of a power function to describe distance estimates depended on the regional membership of the cities. The authors conclude that plausible reasoning strategies, combined with regionalized representations and beliefs about the location of these relative to global landmarks, underlie global-scale latitude and distance judgments.
Estimating the cost related to surveillance of colorectal cancer in a French population
Lejeune, Catherine; Binquet, Christine; Bonnetain, Franck; Mahboubi, Amel; Abrahamowicz, Michal; Moreau, Thierry; Raikou, Maria; Bedenne, Laurent; Quantin, Catherine; Bonithon-Kopp, Claire
2009-01-01
Little is known about costs related to the surveillance of patients that have undergone curative resection of colorectal cancer. The aim of this study was to calculate the observed surveillance costs for 385 patients followed-up over a 3-year period, to estimate surveillance costs if French guidelines are respected, and to identify the determinants related to surveillance costs to derive a global estimation for France, using a linear mixed model. The observed mean surveillance cost was € 713. If French recommendations were strictly applied, the estimated mean cost would vary between € 680 and € 1 069 according to the frequency of abdominal ultrasound. The predicted determinants of the cost were: age, recurrence, duration of surveillance since diagnosis, and adjuvant treatments. For France, the surveillance cost represented 4.4% of the cost of colorectal cancer management. The cost of surveillance should now be balanced with its effectiveness and compared with surveillance alternatives. PMID:19259712
Yousefi, Siavash
2014-01-01
In an optical coherence tomography (OCT) scan from a living tissue, red blood cells (RBCs) are the major source of backscattering signal from moving particles within microcirculatory system. Measuring the concentration and velocity of RBC particles allows assessment of RBC flux and flow, respectively, to assess tissue perfusion and oxygen/nutrition exchange rates within micro-structures. In this paper, we propose utilizing spectral estimation techniques to simultaneously quantify bi-directional particle flow and relative flux by spectral estimation of the received OCT signal from moving particles within capillary tubes embedded in tissue mimicking phantoms. The proposed method can be directly utilized for in vivo quantification of capillaries and microvessels. Compared to the existing methods in the literature that can either quantify flow direction or power, our proposed method allows simultaneous flow (velocity) direction and relative flux (power) estimation. PMID:25327449
NASA Astrophysics Data System (ADS)
Yousefi, Siavash; Wang, Ruikang K.
2014-11-01
In an optical coherence tomography (OCT) scan from a living tissue, red blood cells (RBCs) are the major source of backscattering signal from moving particles within microcirculatory system. Measuring the concentration and velocity of RBC particles allows assessment of RBC flux and flow, respectively, to assess tissue perfusion and oxygen/nutrition exchange rates within micro-structures. In this paper, we propose utilizing spectral estimation techniques to simultaneously quantify bi-directional particle flow and relative flux by spectral estimation of the received OCT signal from moving particles within capillary tubes embedded in tissue mimicking phantoms. The proposed method can be directly utilized for in vivo quantification of capillaries and microvessels. Compared to the existing methods in the literature that can either quantify flow direction or power, our proposed method allows simultaneous flow (velocity) direction and relative flux (power) estimation.
Estimation of salient regions related to chronic gastritis using gastric X-ray images.
Togo, Ren; Ishihara, Kenta; Ogawa, Takahiro; Haseyama, Miki
2016-10-01
Since technical knowledge and a high degree of experience are necessary for diagnosis of chronic gastritis, computer-aided diagnosis (CAD) systems that analyze gastric X-ray images are desirable in the field of medicine. Therefore, a new method that estimates salient regions related to chronic gastritis/non-gastritis for supporting diagnosis is presented in this paper. In order to estimate salient regions related to chronic gastritis/non-gastritis, the proposed method monitors the distance between a target image feature and Support Vector Machine (SVM)-based hyperplane for its classification. Furthermore, our method realizes removal of the influence of regions outside the stomach by using positional relationships between the stomach and other organs. Consequently, since the proposed method successfully estimates salient regions of gastric X-ray images for which chronic gastritis and non-gastritis are unknown, visual support for inexperienced clinicians becomes feasible. PMID:27494090
Lee, Eugenia E.; Stewart, Barclay; Zha, Yuanting A.; Groen, Thomas A.; Burkle, Frederick M.; Kushner, Adam L.
2016-01-01
Background: Climate extremes will increase the frequency and severity of natural disasters worldwide. Climate-related natural disasters were anticipated to affect 375 million people in 2015, more than 50% greater than the yearly average in the previous decade. To inform surgical assistance preparedness, we estimated the number of surgical procedures needed. Methods: The numbers of people affected by climate-related disasters from 2004 to 2014 were obtained from the Centre for Research of the Epidemiology of Disasters database. Using 5,000 procedures per 100,000 persons as the minimum, baseline estimates were calculated. A linear regression of the number of surgical procedures performed annually and the estimated number of surgical procedures required for climate-related natural disasters was performed. Results: Approximately 140 million people were affected by climate-related natural disasters annually requiring 7.0 million surgical procedures. The greatest need for surgical care was in the People’s Republic of China, India, and the Philippines. Linear regression demonstrated a poor relationship between national surgical capacity and estimated need for surgical care resulting from natural disaster, but countries with the least surgical capacity will have the greatest need for surgical care for persons affected by climate-related natural disasters. Conclusion: As climate extremes increase the frequency and severity of natural disasters, millions will need surgical care beyond baseline needs. Countries with insufficient surgical capacity will have the most need for surgical care for persons affected by climate-related natural disasters. Estimates of surgical are particularly important for countries least equipped to meet surgical care demands given critical human and physical resource deficiencies.
Lee, Eugenia E.; Stewart, Barclay; Zha, Yuanting A.; Groen, Thomas A.; Burkle, Frederick M.; Kushner, Adam L.
2016-01-01
Background: Climate extremes will increase the frequency and severity of natural disasters worldwide. Climate-related natural disasters were anticipated to affect 375 million people in 2015, more than 50% greater than the yearly average in the previous decade. To inform surgical assistance preparedness, we estimated the number of surgical procedures needed. Methods: The numbers of people affected by climate-related disasters from 2004 to 2014 were obtained from the Centre for Research of the Epidemiology of Disasters database. Using 5,000 procedures per 100,000 persons as the minimum, baseline estimates were calculated. A linear regression of the number of surgical procedures performed annually and the estimated number of surgical procedures required for climate-related natural disasters was performed. Results: Approximately 140 million people were affected by climate-related natural disasters annually requiring 7.0 million surgical procedures. The greatest need for surgical care was in the People’s Republic of China, India, and the Philippines. Linear regression demonstrated a poor relationship between national surgical capacity and estimated need for surgical care resulting from natural disaster, but countries with the least surgical capacity will have the greatest need for surgical care for persons affected by climate-related natural disasters. Conclusion: As climate extremes increase the frequency and severity of natural disasters, millions will need surgical care beyond baseline needs. Countries with insufficient surgical capacity will have the most need for surgical care for persons affected by climate-related natural disasters. Estimates of surgical are particularly important for countries least equipped to meet surgical care demands given critical human and physical resource deficiencies. PMID:27617165
Reanalysis of in situ permeability measurements in the Barbados décollement
Bekins, B.A.; Matmon, D.; Screaton, E.J.; Brown, K.M.
2011-01-01
A cased and sealed borehole in the Northern Barbados accretionary complex was the site of the first attempts to measure permeability in situ along a plate boundary décollement. Three separate efforts at Hole 949C yielded permeability estimates for the décollement spanning four orders of magnitude. An analysis of problems encountered during installation of the casing and seals provides insights into how the borehole conditions may have led to the wide range of results. During the installation, sediments from the surrounding formation repeatedly intruded into the borehole and casing. Stress analysis shows that the weak sediments were deforming plastically and the radial and tangential stresses around the borehole were significantly lower than lithostatic. This perturbed stress state may explain why the test pressure records showed indications of hydrofracture at pressures below lithostatic, and permeabilities rose rapidly as the estimated effective stress dropped below 0.8 MPa. Even after the borehole was sealed, the plastic deformation of the formation and relatively large gap of the wire wrapped screen allowed sediment to flow into the casing. Force equilibrium calculations predict sediment would have filled the borehole to 10 cm above the top of the screen by the time slug tests were conducted 1.5 years after the borehole was sealed. Reanalysis of the slug test results with these conditions yields several orders of magnitude higher permeability estimates than the original analysis which assumed an open casing. Overall the results based on only the tests with no sign of hydrofracture yield a permeability range of 10−14–10−15 m2 and a rate of increase in permeability with decreasing effective stress consistent with laboratory tests on samples from the décollement zone.
Frutiger, Jérôme; Marcarie, Camille; Abildskov, Jens; Sin, Gürkan
2016-11-15
This study presents new group contribution (GC) models for the prediction of Lower and Upper Flammability Limits (LFL and UFL), Flash Point (FP) and Auto Ignition Temperature (AIT) of organic chemicals applying the Marrero/Gani (MG) method. Advanced methods for parameter estimation using robust regression and outlier treatment have been applied to achieve high accuracy. Furthermore, linear error propagation based on covariance matrix of estimated parameters was performed. Therefore, every estimated property value of the flammability-related properties is reported together with its corresponding 95%-confidence interval of the prediction. Compared to existing models the developed ones have a higher accuracy, are simple to apply and provide uncertainty information on the calculated prediction. The average relative error and correlation coefficient are 11.5% and 0.99 for LFL, 15.9% and 0.91 for UFL, 2.0% and 0.99 for FP as well as 6.4% and 0.76 for AIT. Moreover, the temperature-dependence of LFL property was studied. A compound specific proportionality constant (K(LFL)) between LFL and temperature is introduced and an MG GC model to estimate K(LFL) is developed. Overall the ability to predict flammability-related properties including the corresponding uncertainty of the prediction can provide important information for a qualitative and quantitative safety-related risk assessment studies. PMID:27453258
A General and Flexible Approach to Estimating the Social Relations Model Using Bayesian Methods
ERIC Educational Resources Information Center
Ludtke, Oliver; Robitzsch, Alexander; Kenny, David A.; Trautwein, Ulrich
2013-01-01
The social relations model (SRM) is a conceptual, methodological, and analytical approach that is widely used to examine dyadic behaviors and interpersonal perception within groups. This article introduces a general and flexible approach to estimating the parameters of the SRM that is based on Bayesian methods using Markov chain Monte Carlo…
Effect of geocoding errors on traffic-related air pollutant exposure and concentration estimates
Exposure to traffic-related air pollutants is highest very near roads, and thus exposure estimates are sensitive to positional errors. This study evaluates positional and PM2.5 concentration errors that result from the use of automated geocoding methods and from linearized approx...
Martínez-Martínez, Víctor; Baladrón, Carlos; Gomez-Gil, Jaime; Ruiz-Ruiz, Gonzalo; Navas-Gracia, Luis M.; Aguiar, Javier M.; Carro, Belén
2012-01-01
This paper presents a system based on an Artificial Neural Network (ANN) for estimating and predicting environmental variables related to tobacco drying processes. This system has been validated with temperature and relative humidity data obtained from a real tobacco dryer with a Wireless Sensor Network (WSN). A fitting ANN was used to estimate temperature and relative humidity in different locations inside the tobacco dryer and to predict them with different time horizons. An error under 2% can be achieved when estimating temperature as a function of temperature and relative humidity in other locations. Moreover, an error around 1.5 times lower than that obtained with an interpolation method can be achieved when predicting the temperature inside the tobacco mass as a function of its present and past values with time horizons over 150 minutes. These results show that the tobacco drying process can be improved taking into account the predicted future value of the monitored variables and the estimated actual value of other variables using a fitting ANN as proposed. PMID:23202032
Federal Register 2010, 2011, 2012, 2013, 2014
2011-01-19
... opportunity to participate in a voluntary consent agreement (70 FR 4958) referred to as the Air Compliance... AGENCY 40 CFR Part 60 Call for Information: Information Related to the Development of Emission-Estimating... quality-assured emissions and process data that are relevant to developing...
ERIC Educational Resources Information Center
Friedman, Alinda; Montello, Daniel R.
2006-01-01
The authors examined whether absolute and relative judgments about global-scale locations and distances were generated from common representations. At the end of a 10-week class on the regional geography of the United States, participants estimated the latitudes of 16 North American cities and all possible pairwise distances between them. Although…
Longitudinal and Concurrent Relations among Temperament, Ability Estimation, and Injury Proneness.
ERIC Educational Resources Information Center
Schwebel, David C.; Plumert, Jodie M.
1999-01-01
Examined relations between temperament, ability estimation, and injury proneness from toddlerhood through school age. Found that children scoring high on Extroversion and low on Inhibitory Control as toddlers and preschoolers tended to overestimate their physical abilities and have more unintentional injuries at age 6. Children low on Extroversion…
ERIC Educational Resources Information Center
Sandy, Leo R.
1998-01-01
Discusses the concept of permeability as knowledge flow into and out of the classroom and applies it to three college courses taught by the author at Plymouth State College (New Hampshire). Experiential knowledge comes into the classroom through interviews, guest speakers, and panel presentations, and flows out through service-learning students…
NASA Astrophysics Data System (ADS)
Guéguen, Y.; Gavrilenko, P.; Le Ravalec, M.
1996-05-01
Permeability is a transport property which is currently measured in Darcy units. Although this unit is very convenient for most purposes, its use prevents from recognizing that permeability has units of length squared. Physically, the square root of permeability can thus be seen as a characteristic length or a characteristic pore size. At the laboratory scale, the identification of this characteristic length is a good example of how experimental measurements and theoretical modelling can be integrated. Three distinct identifications are of current use, relying on three different techniques: image analysis of thin sections, mercury porosimetry and nitrogen adsorption. In each case, one or several theoretical models allow us to derive permeability from the experimental data (equivalent channel models, statistical models, effective media models, percolation and network models). Permeability varies with pressure and temperature and this is a decisive point for any extrapolation to crustal conditions. As far as pressure is concerned, most of the effect is due to cracks and a model which does not incorporate this fact will miss its goal. Temperature induced modifications can be the result of several processes: thermal cracking (due to thermal expansion mismatch and anisotropy, or to fluid pressure build up), and pressure solution are the two main ones. Experimental data on pressure and temperature effects are difficult to obtain but they are urgently needed. Finally, an important issue is: up to which point are these small scale data and models relevant when considering formations at the oil reservoir scale, or at the crust scale? At larger scales the identification of the characteristic scale is also a major goal which is examined.
Estimation of insurance-related losses resulting from coastal flooding in France
NASA Astrophysics Data System (ADS)
Naulin, J. P.; Moncoulon, D.; Le Roy, S.; Pedreros, R.; Idier, D.; Oliveros, C.
2016-01-01
A model has been developed in order to estimate insurance-related losses caused by coastal flooding in France. The deterministic part of the model aims at identifying the potentially flood-impacted sectors and the subsequent insured losses a few days after the occurrence of a storm surge event on any part of the French coast. This deterministic component is a combination of three models: a hazard model, a vulnerability model, and a damage model. The first model uses the PREVIMER system to estimate the water level resulting from the simultaneous occurrence of a high tide and a surge caused by a meteorological event along the coast. A storage-cell flood model propagates these water levels over the land and thus determines the probable inundated areas. The vulnerability model, for its part, is derived from the insurance schedules and claims database, combining information such as risk type, class of business, and insured values. The outcome of the vulnerability and hazard models are then combined with the damage model to estimate the event damage and potential insured losses. This system shows satisfactory results in the estimation of the magnitude of the known losses related to the flood caused by the Xynthia storm. However, it also appears very sensitive to the water height estimated during the flood period, conditioned by the junction between seawater levels and coastal topography, the accuracy for which is still limited by the amount of information in the system.
Estimation of insurance related losses resulting from coastal flooding in France
NASA Astrophysics Data System (ADS)
Naulin, J. P.; Moncoulon, D.; Le Roy, S.; Pedreros, R.; Idier, D.; Oliveros, C.
2015-04-01
A model has been developed in order to estimate insurance-related losses caused by coastal flooding in France. The deterministic part of the model aims at identifying the potentially flood-impacted sectors and the subsequent insured losses a few days after the occurrence of a storm surge event on any part of the French coast. This deterministic component is a combination of three models: a hazard model, a vulnerability model and a damage model. The first model uses the PREVIMER system to estimate the water level along the coast. A storage-cell flood model propagates these water levels over the land and thus determines the probable inundated areas. The vulnerability model, for its part, is derived from the insurance schedules and claims database; combining information such as risk type, class of business and insured values. The outcome of the vulnerability and hazard models are then combined with the damage model to estimate the event damage and potential insured losses. This system shows satisfactory results in the estimation of the magnitude of the known losses related to the flood caused by the Xynthia storm. However, it also appears very sensitive to the water height estimated during the flood period, conditioned by the junction between sea water levels and coastal topography for which the accuracy is still limited in the system.
NASA Astrophysics Data System (ADS)
Muraoka, H.; Sakaguchi, K.; Nakao, S.; Kimbara, K.
2006-05-01
A bi-logarithmic plot of the discharge temperature versus flow rate of 3,686 hot springs in Japan shows a broad but positive correlation. This correlation is semiquantitatively explained as buoyancy-driven Darcy flow using a one-dimensional advection flow equation for hot water in a porous media assuming a 1 km reservoir depth and 104 m2 discharge area for each hot spring. The permeability of the best fit curve to the relation is 10-13 m2 that is a typical value for relatively low-temperature geothermal fields at a reservoir temperature less than 260°C. This is consistent with the relatively low reservoir temperature for these hot springs. Based on the relation, the permeability of each hot spring area can be estimated from the discharge temperature and discharge rate values, and permeability mapping for the 1 km skin depth is performed for almost all of Japan.
Kernel PLS Estimation of Single-trial Event-related Potentials
NASA Technical Reports Server (NTRS)
Rosipal, Roman; Trejo, Leonard J.
2004-01-01
Nonlinear kernel partial least squaes (KPLS) regressior, is a novel smoothing approach to nonparametric regression curve fitting. We have developed a KPLS approach to the estimation of single-trial event related potentials (ERPs). For improved accuracy of estimation, we also developed a local KPLS method for situations in which there exists prior knowledge about the approximate latency of individual ERP components. To assess the utility of the KPLS approach, we compared non-local KPLS and local KPLS smoothing with other nonparametric signal processing and smoothing methods. In particular, we examined wavelet denoising, smoothing splines, and localized smoothing splines. We applied these methods to the estimation of simulated mixtures of human ERPs and ongoing electroencephalogram (EEG) activity using a dipole simulator (BESA). In this scenario we considered ongoing EEG to represent spatially and temporally correlated noise added to the ERPs. This simulation provided a reasonable but simplified model of real-world ERP measurements. For estimation of the simulated single-trial ERPs, local KPLS provided a level of accuracy that was comparable with or better than the other methods. We also applied the local KPLS method to the estimation of human ERPs recorded in an experiment on co,onitive fatigue. For these data, the local KPLS method provided a clear improvement in visualization of single-trial ERPs as well as their averages. The local KPLS method may serve as a new alternative to the estimation of single-trial ERPs and improvement of ERP averages.
Colloid transport in dual-permeability media.
Leij, Feike J; Bradford, Scott A
2013-07-01
It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the increased risks for disease caused by microorganisms and colloid-associated contaminants. This study presents a model for colloid transport in dual-permeability media that includes reversible and irreversible retention of colloids and first-order exchange between the aqueous phases of the two regions. The model may also be used to describe transport of other reactive solutes in dual-permeability media. Analytical solutions for colloid concentrations in aqueous and solid phases were obtained using Laplace transformation and matrix decomposition. The solutions proved convenient to assess the effect of model parameters on the colloid distribution. The analytical model was used to describe effluent concentrations for a bromide tracer and 3.2- or 1-μm-colloids that were observed after transport through a composite 10-cm long porous medium made up of a cylindrical lens or core of sand and a surrounding matrix with sand of a different grain size. The tracer data were described very well and realistic estimates were obtained for the pore-water velocity in the two flow domains. An accurate description was also achieved for most colloid breakthrough curves. Dispersivity and retention parameters were typically greater for the larger 3.2-μm-colloids while both reversible and irreversible retention rates tended to be higher for the finer sands than the coarser sand. The relatively small sample size and the complex flow pattern in the composite medium made it difficult to reach definitive conclusions regarding transport parameters for colloid transport.
Colloid transport in dual-permeability media
NASA Astrophysics Data System (ADS)
Leij, Feike J.; Bradford, Scott A.
2013-07-01
It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the increased risks for disease caused by microorganisms and colloid-associated contaminants. This study presents a model for colloid transport in dual-permeability media that includes reversible and irreversible retention of colloids and first-order exchange between the aqueous phases of the two regions. The model may also be used to describe transport of other reactive solutes in dual-permeability media. Analytical solutions for colloid concentrations in aqueous and solid phases were obtained using Laplace transformation and matrix decomposition. The solutions proved convenient to assess the effect of model parameters on the colloid distribution. The analytical model was used to describe effluent concentrations for a bromide tracer and 3.2- or 1-μm-colloids that were observed after transport through a composite 10-cm long porous medium made up of a cylindrical lens or core of sand and a surrounding matrix with sand of a different grain size. The tracer data were described very well and realistic estimates were obtained for the pore-water velocity in the two flow domains. An accurate description was also achieved for most colloid breakthrough curves. Dispersivity and retention parameters were typically greater for the larger 3.2-μm-colloids while both reversible and irreversible retention rates tended to be higher for the finer sands than the coarser sand. The relatively small sample size and the complex flow pattern in the composite medium made it difficult to reach definitive conclusions regarding transport parameters for colloid transport.
Effects of a limited class of nonlinearities on estimates of relative weights
NASA Astrophysics Data System (ADS)
Richards, Virginia M.
2002-02-01
Perturbation analyses have been applied in recent years to determine the relative contribution of individual stimulus components in detection and discrimination tasks. Responses to stimulus samples are compared to stimulus parameters to determine the details of the decision rule. Often, a linear model is assumed and it is of interest to determine the relative contribution of different stimulus elements to the decision. Here, biases in estimated relative weights are considered for the case where the decision variable is given by D=(∑(αiXin)k)m and the stimulus components, the Xi, are normally distributed, of equal variance, and mutually independent. The αi are the ``true'' combination weights, and n, k, and m are positive reals. The method used to estimate relative weights is the correlation coefficient between the Xi and the observer's responses. Estimates of relative αi do not depend on m but may depend on the mean values of the Xi and the values of n and k (a dependence on the variance, σi2, holds even for linear transformations).
Comparison of structural and least-squares lines for estimating geologic relations
Williams, G.P.; Troutman, B.M.
1990-01-01
Two different goals in fitting straight lines to data are to estimate a "true" linear relation (physical law) and to predict values of the dependent variable with the smallest possible error. Regarding the first goal, a Monte Carlo study indicated that the structural-analysis (SA) method of fitting straight lines to data is superior to the ordinary least-squares (OLS) method for estimating "true" straight-line relations. Number of data points, slope and intercept of the true relation, and variances of the errors associated with the independent (X) and dependent (Y) variables influence the degree of agreement. For example, differences between the two line-fitting methods decrease as error in X becomes small relative to error in Y. Regarding the second goal-predicting the dependent variable-OLS is better than SA. Again, the difference diminishes as X takes on less error relative to Y. With respect to estimation of slope and intercept and prediction of Y, agreement between Monte Carlo results and large-sample theory was very good for sample sizes of 100, and fair to good for sample sizes of 20. The procedures and error measures are illustrated with two geologic examples. ?? 1990 International Association for Mathematical Geology.
NASA Technical Reports Server (NTRS)
Galante, Joseph M.; Van Eepoel, John; D'Souza, Chris; Patrick, Bryan
2016-01-01
The Raven ISS Hosted Payload will feature several pose measurement sensors on a pan/tilt gimbal which will be used to autonomously track resupply vehicles as they approach and depart the International Space Station. This paper discusses the derivation of a Relative Navigation Filter (RNF) to fuse measurements from the different pose measurement sensors to produce relative position and attitude estimates. The RNF relies on relative translation and orientation kinematics and careful pose sensor modeling to eliminate dependence on orbital position information and associated orbital dynamics models. The filter state is augmented with sensor biases to provide a mechanism for the filter to estimate and mitigate the offset between the measurements from different pose sensors
NASA Technical Reports Server (NTRS)
Galante, Joseph M.; Van Eepoel, John; D' Souza, Chris; Patrick, Bryan
2016-01-01
The Raven ISS Hosted Payload will feature several pose measurement sensors on a pan/tilt gimbal which will be used to autonomously track resupply vehicles as they approach and depart the International Space Station. This paper discusses the derivation of a Relative Navigation Filter (RNF) to fuse measurements from the different pose measurement sensors to produce relative position and attitude estimates. The RNF relies on relative translation and orientation kinematics and careful pose sensor modeling to eliminate dependence on orbital position information and associated orbital dynamics models. The filter state is augmented with sensor biases to provide a mechanism for the filter to estimate and mitigate the offset between the measurements from different pose sensors.
Absolute magnitude estimation and relative judgement approaches to subjective workload assessment
NASA Technical Reports Server (NTRS)
Vidulich, Michael A.; Tsang, Pamela S.
1987-01-01
Two rating scale techniques employing an absolute magnitude estimation method, were compared to a relative judgment method for assessing subjective workload. One of the absolute estimation techniques used was an unidimensional overall workload scale and the other was the multidimensional NASA-Task Load Index technique. Thomas Saaty's Analytic Hierarchy Process was the unidimensional relative judgment method used. These techniques were used to assess the subjective workload of various single- and dual-tracking conditions. The validity of the techniques was defined as their ability to detect the same phenomena observed in the tracking performance. Reliability was assessed by calculating test-retest correlations. Within the context of the experiment, the Saaty Analytic Hierarchy Process was found to be superior in validity and reliability. These findings suggest that the relative judgment method would be an effective addition to the currently available subjective workload assessment techniques.
Use of soil catena field data for estimating relative ages of moraines
Birkeland, P.W.; Berry, M.E. ); Swanson, D.K. )
1991-03-01
Soils at the crests of moraines are commonly used to estimate the relative ages of moraines. However, for various pedologic and geomorphic reasons, soil development at crest sites may not truly reflect the time since moraine formation; for example, some crest soils on moraines of greatly different age are similar in morphology and development. Soil catena data for soils at several sites aligned downslope from the crest can greatly improve on the usefulness of soil data for estimating moraine ages. For this purpose, the authors use the weighted mean catena profile development index, which condenses field data for all of the soils in each catena into a single value.
Parameter estimation and tests of General Relativity with GW transients in Advanced LIGO
NASA Astrophysics Data System (ADS)
Vitale, Salvatore
2016-03-01
The Advanced LIGO observatories have successfully completed their first observation run. Data were collected from September 2015 to January 2016, with a sensitivity a few times better than initial instruments in the hundreds of Hertz band. Bayesian parameter estimation and model selection algorithms can be used to estimate the astrophysical parameters of gravitational-wave sources, as well as to perform tests of General Relativity in its strong-field dynamical regime. In this talk we will describe the methods devised to characterize transient gravitational wave sources and their applications in the advanced gravitational-wave detector era.
Permeability evolution in sandstone: Digital rock approach
NASA Astrophysics Data System (ADS)
Kameda, Ayako
Permeability is perhaps one of the most important yet elusive reservoir properties, since it poorly correlates with elastic properties, and as a result, cannot be mapped remotely. Physical permeability measurements may be augmented or even partially replaced by numerical experiments, provided that a numerical simulation accurately mimics the physical process. Numerical simulation of laboratory experiments on rocks, or digital rock physics, is an emerging field that may benefit the petroleum industry. For numerical experimentation to find its way into the mainstream, it has to be practical and easily repeatable, i.e., implemented on standard hardware and in real time. This condition reduces the feasible size of a digital sample to just a few grains across. Will the results be meaningful for a larger rock volume? The answer is that small fragments of medium- to high-porosity sandstone, such as cuttings, which are not statistically representative of a larger sample, cannot be used to numerically calculate the exact porosity and permeability of the sample. However, by using a significant number of such small fragments, it may be possible to establish a site-specific permeability-porosity trend, which can be used to estimate the absolute permeability from independent porosity data, obtained in the well or inferred from seismic measurements.
Weech, A A; Michaelis, L
1928-11-20
The flat type of dried collodion membrane used by Michaelis and his associates in numerous investigations has been subjected to mensuration in order that the dimensions of these membranes may be placed on record. The membranes had a functioning area of about 30 cm., were approximately 0.1 mm. in thickness and were composed on the average of 87 per cent by volume of collodion and 13 per cent by volume of pores. In reviewing some of the previously reported results of diffusion experiments with non-electrolytes in the light of the calculated values for the total pore area for the same membranes additional evidence was presented to show that a smaller molecule (acetone) probably utilizes a much larger percentage of the total pore area for its diffusion than is available for a larger molecule (glycerol). By using the figures of Fricke and McClendon for the thickness of the membrane of the red blood cell some comparisons were drawn between the dried collodion membrane as a model for certain biological membranes and the red blood cell membrane. In these comparisons emphasis was placed on the exaggerated importance of small electromotive forces and very slight permeabilities when these were associated with membranes of such extreme thinness as the red blood cell membrane.
EPA Permeable Surface Research - Poster
EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...
The estimation of age-related rates of infection from case notifications and serological data.
Grenfell, B. T.; Anderson, R. M.
1985-01-01
The paper describes a maximum-likelihood method for the estimation of age-related changes in the per capita rate of infection, from case notification records or serological data. The methods are applied to records of measles incidence in the UK and USA, for which the estimated rates of infection tend to rise to a maximum value at around 10 years of age and then to decline in the older age-classes. Longer-term and seasonal trends are analysed by reference to changes in the estimated average age at infection; a statistic derived from a knowledge of the age-specific rates of infection. Future data needs in the epidemiological study of directly transmitted viral and bacterial diseases are discussed with reference to the detection and interpretation of age-dependent rates of disease transmission. PMID:4067297
Han, Min; Fu, Shao; Gao, Jian-Qing; Fang, Xiao-Ling
2009-06-01
In the present study, ginsenoside Rg(1) (Rg(1)), a naturally occurring drug which is hardly absorbed in gastrointestinal (GI) tract due to its high hydrophilicity and low membrane permeability, was incorporated in different compositions of water-in-oil microemulsions (MEs). And parallel artificial membrane permeability assay (PAMPA) that have been mainly utilized for the evaluation of in vitro permeability of early drug candidates was introduced in present study, as well as rat in vivo pharmacokinetics and in vitro permeability measurements, to investigate the effect of w/o ME on Rg(1) absorption. Correlation between various models as mentioned above was further performed to estimate the feasibility of PAMPA in the application of pharmaceutical preparation studies. After being administrated intraduodenally to rats, most of MEs can enhance the intestinal absorption of Rg(1) to various extents with relative bioavailability (F(re)) ranging from 268 to 1270% using drug solution as control. This enhanced absorption of Rg(1) may be related to its increased membrane permeability induced by ME as exhibited in the PAMPA and rat in vitro permeability measurements. Meanwhile, rat in vivo pharmacokinetics-PAMPA correlation (r(2)=0.6082) is significant (p<0.05) for ME, representing a potential prospect for the application of PAMPA in the study of pharmaceutical preparation in some conditions. PMID:19483317
NASA Astrophysics Data System (ADS)
Cao, Lu; Chen, Xiaoqian; Misra, Arun K.
2015-07-01
This paper presents a novel sigma-point unscented predictive filter (UPF) for relative position and attitude estimation of satellite formation taking into account the influence of J2. A coupled relative translational dynamics model is formulated to represent orbital motion of arbitrary feature points on the deputy spacecraft, and the relative attitude motion is formulated by considering a rotational dynamics for a satellite without gyros. Based on the proposed coupled dynamic model, the UPF is developed based on unscented transformation technique, extending the capability of a traditional predictive filter (PF). The algorithm flow of the UPF is described first. Then it is demonstrated that the estimation accuracy of the model error and system state for UPF is higher than that of the traditional PF. In addition, the unscented Kalman filter (UKF) is also employed in order to compare the performance of the proposed UPF with that of the UKF. Several different scenarios are simulated to validate the effectiveness of the coupled dynamics model and the performance of the proposed UPF. Through comparisons, the proposed UPF is shown to yield highly accurate estimation of relative position and attitude during satellite formation flying.
Lipponen, Jukka A; Tarvainen, Mika P; Laitinen, Tomi; Karjalainen, Pasi A; Vanninen, Joonas; Koponen, Timo; Laitinen, Tiina M
2013-12-01
Continuous electrocardiogram, blood pressure and carotid artery ultrasound video were analyzed from 15 diabetics and 28 healthy controls. By using these measurements artery elasticity, overall baroreflex sensitivity (BRS) assessed between RR and systolic blood pressure variation, and neural BRS assessed between RR and artery diameter variation were estimated. In addition, BRS was estimated using traditional and causal methods which enable separation of feedforward and feedback variation. The aim of this study was to analyze overall and neural BRS in relation to artery stiffness and to validate the causal BRS estimation method in assessing these two types of BRS within the study population. The most significant difference between the healthy and diabetic groups (p < 0.0007) was found for the overall BRS estimated using the causal method. The difference between the groups was also significant for neural BRS (p < 0.0018). However neural BRS was normal in some old diabetics, which indicates normal functioning of autonomic nervous system (ANS), even though the elasticity in arteries of these subjects was reduced. The noncausal method overestimated neural BRS in low BRS values when compared to causal BRS. In conclusion, neural BRS estimated using the causal method is proposed as the best marker of ANS functioning. PMID:24168896
Folser, George R.
1980-01-01
Electrodes for use in an electrolytic cell, which are liquid-permeable and have low electrical resistance and high internal surface area are provided of a rigid, porous, carbonaceous matrix having activated carbon uniformly embedded throughout. The activated carbon may be catalyzed with platinum for improved electron transfer between electrode and electrolyte. Activated carbon is mixed with a powdered thermosetting phenolic resin and compacted to the desired shape in a heated mold to melt the resin and form the green electrode. The compact is then heated to a pyrolyzing temperature to carbonize and volatilize the resin, forming a rigid, porous structure. The permeable structure and high internal surface area are useful in electrolytic cells where it is necessary to continuously remove the products of the electrochemical reaction.
[Venoruton and capillary permeability].
Cesarone, M R; Laurora, G; Gabini, M; Errichi, B M; Candiani, C; Belcaro, G
1989-05-01
A new system to evaluate capillary permeability, the vacuum suction chamber (VSC) device, was used to assess the effects of Venoruton in patients with venous hypertension. A temporary, superficial skin lesion (wheal) was produced with the VSC device by negative pressure (30 mmHg) applied for 10 minutes on the internal, perimalleolar region. Wheals disappear in less than 60 minutes in normals while in patients with venous hypertension the wheal is more persistent, requiring a significantly longer time to disappear. This new technique was used in association with laser-Doppler flowmetry to evaluate the efficacy of Venoruton (1000 mgs t.i.d.) administered for 2 weeks on venous hypertension. Results indicate a positive effect of Venoruton in reducing the abnormally increased capillary permeability in venous hypertension and are proportional to the changes observed in signs and symptoms after treatment.
Permeability of continental crust influenced by internal and external forcing
Rojstaczer, S.A.; Ingebritsen, S.E.; Hayba, D.O.
2008-01-01
The permeability of continental crust is so highly variable that it is often considered to defy systematic characterization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability-depth relations) on a very large scale? Here we argue that large-scale crustal permeability adjusts to accommodate rates of internal and external forcing. In the deeper crust, internal forcing - fluxes induced by metamorphism, magmatism, and mantle degassing - is dominant, whereas in the shallow crust, external forcing - the vigor of the hydrologic cycle - is a primary control. Crustal petrologists have long recognized the likelihood of a causal relation between fluid flux and permeability in the deep, ductile crust, where fluid pressures are typically near-lithostatic. It is less obvious that such a relation should pertain in the relatively cool, brittle upper crust, where near-hydrostatic fluid pressures are the norm. We use first-order calculations and numerical modeling to explore the hypothesis that upper-crustal permeability is influenced by the magnitude of external fluid sources, much as lower-crustal permeability is influenced by the magnitude of internal fluid sources. We compare model-generated permeability structures with various observations of crustal permeability. ?? 2008 The Authors Journal compilation ?? 2008 Blackwell Publishing Ltd.
Use of artifical neural nets to predict permeability in Hugoton Field
Thompson, K.A.; Franklin, M.H.; Olson, T.M.
1996-12-31
One of the most difficult tasks in petrophysics is establishing a quantitative relationship between core permeability and wireline logs. This is a tough problem in Hugoton Field, where a complicated mix of carbonates and clastics further obscure the correlation. One can successfully model complex relationships such as permeability-to-logs using artificial neural networks. Mind and Vision, Inc.`s neural net software was used because of its orientation toward depth-related data (such as logs) and its ability to run on a variety of log analysis platforms. This type of neural net program allows the expert geologist to select a few (10-100) points of control to train the {open_quotes}brainstate{close_quotes} using logs as predicters and core permeability as {open_quotes}truth{close_quotes}. In Hugoton Field, the brainstate provides an estimate of permeability at each depth in 474 logged wells. These neural net-derived permeabilities are being used in reservoir characterization models for fluid saturations. Other applications of this artificial neural network technique include deterministic relationships of logs to: core lithology, core porosity, pore type, and other wireline logs (e.g., predicting a sonic log from a density log).
Use of artifical neural nets to predict permeability in Hugoton Field
Thompson, K.A.; Franklin, M.H.; Olson, T.M. )
1996-01-01
One of the most difficult tasks in petrophysics is establishing a quantitative relationship between core permeability and wireline logs. This is a tough problem in Hugoton Field, where a complicated mix of carbonates and clastics further obscure the correlation. One can successfully model complex relationships such as permeability-to-logs using artificial neural networks. Mind and Vision, Inc.'s neural net software was used because of its orientation toward depth-related data (such as logs) and its ability to run on a variety of log analysis platforms. This type of neural net program allows the expert geologist to select a few (10-100) points of control to train the [open quotes]brainstate[close quotes] using logs as predicters and core permeability as [open quotes]truth[close quotes]. In Hugoton Field, the brainstate provides an estimate of permeability at each depth in 474 logged wells. These neural net-derived permeabilities are being used in reservoir characterization models for fluid saturations. Other applications of this artificial neural network technique include deterministic relationships of logs to: core lithology, core porosity, pore type, and other wireline logs (e.g., predicting a sonic log from a density log).
Permeability and selectivity of reverse osmosis membranes: correlation to swelling revisited.
Dražević, Emil; Košutić, Krešimir; Freger, Viatcheslav
2014-02-01
Membrane swelling governs both rejection of solutes and permeability of polymeric membranes, however very few data have been available on swelling in water of salt-rejecting reverse osmosis (RO) membranes. This study assesses swelling, thickness and their relation to water permeability for four commercial polyamide (PA) RO membranes (SWC4+, ESPA1, XLE and BW30) using atomic force microscopy (AFM) and attenuated total reflection Fourier transform IR spectroscopy (ATR-FTIR). ATR-FTIR offered a significantly improved estimate of the actual barrier thickness of PA, given AFM is biased by porosity ("fluffy parts") or wiggling of the active layer or presence of a coating layer. Thus obtained intrinsic permeability (permeability times thickness) and selectivity of aromatic polyamides plotted versus swelling falls well on a general trend, along with previously reported data on several common materials showing RO and NF selectivity. The observed general trend may be rationalized by viewing the polymers as a random composite medium containing molecularly small pores. The results suggest that the combination of a rigid low dielectric matrix, limiting the pore size, with multiple hydrophilic H-bonding sites may be a common feature of RO/NF membranes, allowing both high permeability and selectivity.
Permeability and selectivity of reverse osmosis membranes: correlation to swelling revisited.
Dražević, Emil; Košutić, Krešimir; Freger, Viatcheslav
2014-02-01
Membrane swelling governs both rejection of solutes and permeability of polymeric membranes, however very few data have been available on swelling in water of salt-rejecting reverse osmosis (RO) membranes. This study assesses swelling, thickness and their relation to water permeability for four commercial polyamide (PA) RO membranes (SWC4+, ESPA1, XLE and BW30) using atomic force microscopy (AFM) and attenuated total reflection Fourier transform IR spectroscopy (ATR-FTIR). ATR-FTIR offered a significantly improved estimate of the actual barrier thickness of PA, given AFM is biased by porosity ("fluffy parts") or wiggling of the active layer or presence of a coating layer. Thus obtained intrinsic permeability (permeability times thickness) and selectivity of aromatic polyamides plotted versus swelling falls well on a general trend, along with previously reported data on several common materials showing RO and NF selectivity. The observed general trend may be rationalized by viewing the polymers as a random composite medium containing molecularly small pores. The results suggest that the combination of a rigid low dielectric matrix, limiting the pore size, with multiple hydrophilic H-bonding sites may be a common feature of RO/NF membranes, allowing both high permeability and selectivity. PMID:24216230
Using 7Be measurements to estimate the relative contributions of interrill and rill erosion
NASA Astrophysics Data System (ADS)
Zhang, Feng-Bao; Yang, Ming-Yi; Walling, Des E.; Zhang, Bo
2014-02-01
Rapid and reliable methods for estimating the relative contribution of interrill and rill erosion during a rainfall event are needed to provide an improved understanding of soil erosion processes and to develop process-based soil erosion prediction models. Use of the radionuclide 7Be in controlled experiments provides a means of addressing this need and this paper reports an experimental study aimed at refining and testing procedures employed to estimate the relative contribution of the two components of erosion. Four experimental plots (area 5 × 2 m and 10°, 15°, 20°, and 25° slope), filled with a loessial soil, manually tilled, and kept free of weeds with herbicides, were subjected to high intensity rainfall (91.8-120.6 mm h- 1), in order to induce rill development. The evolution of the rill network was documented photographically during the rainfall events and the runoff and sediment output from the plots were collected and measured. The sediment was recovered from the runoff and its mass and 7Be activity were measured. The Yang model, reported previously, was used to estimate the relative contributions of interrill and rill erosion from the 7Be activity of the exported sediment and this model was further refined to take account of the dynamic growth of the rills during the rainfall event. The results from the experiments were also used to develop a simple empirical linear model for estimating the relative contributions of interrill and rill erosion from the 7Be measurements. A comparison of the results provided by the three models showed some differences in the estimates of the magnitude of the relative contributions, although their trend during the event was similar. The estimates provided by the empirical linear model tended to be higher than those obtained using the refined model and lower than those generated by the Yang model, but were closer to those provided by the refined model which was seen as being theoretically the most accurate model. The
Techniques for estimating peak-flow frequency relations for North Dakota streams
Williams-Sether, Tara
1992-01-01
This report presents techniques for estimating peak-flow frequency relations for North Dakota streams. In addition, a generalized skew coefficient analysis was completed for North Dakota to test the validity of using the generalized skew coefficient map in Bulletin 17B of the Hydrology Subcommittee of the Interagency Advisory Committee on Water Data, 1982, 'Guidelines for Determining Flood Flow Frequency.' The analysis indicates that the generalized skew coefficient map in Bulletin 17B provides accurate estimates of generalized skew coefficient values for natural-flow streams in North Dakota. Peak-flow records through 1988 for 192 continuous- and partial-record streamflow gaging stations that had 10 or more years of record were used in a generalized least-squares regression analysis that relates peak flows for selected recurrence intervals to selected basin characteristics. Peak-flow equations were developed for recurrence intervals of 2, 10, 15, 25, 50, 100, and 500 years for three hydrologic regions in North Dakota. The peak-flow equations are applicable to natural-flow streams that have drainage areas of less than or equal to 1,000 square miles. The standard error of estimate for the three hydrologic regions ranges from 60 to 70 percent for the 100-year peak-flow equations. Methods are presented for transferring peak-flow data from gaging stations to ungaged sites on the same stream and for determining peak flows for ungaged sites on ungaged streams. Peak-flow relations, weighted estimates of peak flow, and selected basin characteristics are tabulated for the 192 gaging stations used in the generalized skew coefficient and regression analyses. Peak-flow relations also are provided for 63 additional gaging stations that were not used in the generalized skew coefficient and regression analyses. These 63 gaging stations generally represent streams that are significantly controlled by regulation and those that have drainage areas greater than 1,000 square miles.
Estimation of Relative Protein-RNA Binding Strengths from Fluctuations in the Bound State.
Ghaemi, Zhaleh; Guzman, Irisbel; Baek, Jung-Un Julia; Gruebele, Martin; Luthey-Schulten, Zaida
2016-09-13
Protein-RNA complexes are increasingly important in our understanding of cell signaling, metabolism, and transcription. Electrostatic interactions play dominant role in stabilizing such complexes. Using conventional computational approaches, very long simulations of both bound and unbound states are required to obtain accurate estimates of complex dissociation constants (Kd). Here, we derive a simple formula that offers an alternative approach based on the theory of fluctuations. Our method extracts a strong correlate to experimental Kd values using short molecular dynamics simulations of the bound complex only. To test our method, we compared the computed relative Kd values to our experimentally measured values for the U1A-Stem Loop 2 (SL2) RNA complex, which is one of the most-studied protein-RNA complexes. Additionally we also included several experimental values from the literature, to enlarge the data set. We obtain a correlation of r = 0.93 between theoretical and measured estimates of Kd values of the mutated U1A protein-RNA complexes relative to the wild type dissociation constant. The proposed method increases the efficiency of relative Kd values estimation for multiple protein mutants, allowing its applicability to protein engineering projects. PMID:27529183
Estimation of air pollution-related mortality for the Ohio River Basin Energy Study Region
Arbogast, G.L.
1982-01-01
A cross-section analysis for 1976 is performed by estimating conventional health-damage specifications. Better air-quality data are used and socio-economic controls are instituted to derive a more-accurate estimate of the air pollution-related mortality by disease that is attributable to the residuals discharge by the coal-fired electric-utility sector of the Ohio River Basin Energy Study Region (ORBES). Diseases suspected of being sensitively associated with air pollution as mortality responses are categorized as cancer, cardiovascular, and respiratory. Air pollutants are SO/sub 2/, SO/sub 4/, and particulates for years 1976, 1985, and 2000 and for scenarios of utility compliance and noncompliance to state air-pollution regulations. The empirical results reveal that SO/sub 2/, particulates, and SO/sub 4/ are pernicious in that order and that noncompliance-related mortality is 1.6 times the compliance-related mortality. Most important is that logit and ridge regression, respectively, indicate in many instances that stochastic bio-responses to air pollution and multicollinearity among the data vectors strongly bias (overestimate) the linear least-squares estimates.
Methodology to estimate the relative pressure field from noisy experimental velocity data
NASA Astrophysics Data System (ADS)
Bolin, C. D.; Raguin, L. G.
2008-11-01
The determination of intravascular pressure fields is important to the characterization of cardiovascular pathology. We present a two-stage method that solves the inverse problem of estimating the relative pressure field from noisy velocity fields measured by phase contrast magnetic resonance imaging (PC-MRI) on an irregular domain with limited spatial resolution, and includes a filter for the experimental noise. For the pressure calculation, the Poisson pressure equation is solved by embedding the irregular flow domain into a regular domain. To lessen the propagation of the noise inherent to the velocity measurements, three filters - a median filter and two physics-based filters - are evaluated using a 2-D Couette flow. The two physics-based filters outperform the median filter for the estimation of the relative pressure field for realistic signal-to-noise ratios (SNR = 5 to 30). The most accurate pressure field results from a filter that applies in a least-squares sense three constraints simultaneously: consistency between measured and filtered velocity fields, divergence-free and additional smoothness conditions. This filter leads to a 5-fold gain in accuracy for the estimated relative pressure field compared to without noise filtering, in conditions consistent with PC-MRI of the carotid artery: SNR = 5, 20 x 20 discretized flow domain (25 X 25 computational domain).
Species Tree Estimation for the Late Blight Pathogen, Phytophthora infestans, and Close Relatives
Blair, Jaime E.; Coffey, Michael D.; Martin, Frank N.
2012-01-01
To better understand the evolutionary history of a group of organisms, an accurate estimate of the species phylogeny must be known. Traditionally, gene trees have served as a proxy for the species tree, although it was acknowledged early on that these trees represented different evolutionary processes. Discordances among gene trees and between the gene trees and the species tree are also expected in closely related species that have rapidly diverged, due to processes such as the incomplete sorting of ancestral polymorphisms. Recently, methods have been developed for the explicit estimation of species trees, using information from multilocus gene trees while accommodating heterogeneity among them. Here we have used three distinct approaches to estimate the species tree for five Phytophthora pathogens, including P. infestans, the causal agent of late blight disease in potato and tomato. Our concatenation-based “supergene” approach was unable to resolve relationships even with data from both the nuclear and mitochondrial genomes, and from multiple isolates per species. Our multispecies coalescent approach using both Bayesian and maximum likelihood methods was able to estimate a moderately supported species tree showing a close relationship among P. infestans, P. andina, and P. ipomoeae. The topology of the species tree was also identical to the dominant phylogenetic history estimated in our third approach, Bayesian concordance analysis. Our results support previous suggestions that P. andina is a hybrid species, with P. infestans representing one parental lineage. The other parental lineage is not known, but represents an independent evolutionary lineage more closely related to P. ipomoeae. While all five species likely originated in the New World, further study is needed to determine when and under what conditions this hybridization event may have occurred. PMID:22615869
The model-based estimates of important cancer risk factors and screening behaviors are obtained by combining the responses to the Behavioral Risk Factor Surveillance System (BRFSS) and the National Health Interview Survey (NHIS).
Mulholland, J.A.; Mukherjee, J.; Wornat, M.J.; Sarofim, A.F.; Rutledge, G.C. . Dept. of Chemical Engineering)
1993-08-01
The pyrolysis of pure anthracene at temperatures between 1,200 and 1,500 K produced all six bianthryl isomers whose relative yields appear to be related to steric factors. To evaluate the hypothesis that thermodynamic factors govern the product distribution of bianthryls in this system, the relative enthalpies and entropies of biaryl isomers were estimated by molecular orbital modeling, using the semiempirical AM1 (Austin Model 1). Computational analysis of several isomer sets demonstrates that the relative stabilities of a large number of biaryl isomers are determined largely by steric interactions caused by structural features defined as bays, coves, and fjords. These steric factors affect both the degree of biaryl twist in the preferred conformation and the freedom of internal rotation. Molecular orbital modeling supports the hypothesis that a thermodynamic distribution of bianthryl isomers is produced by anthracene pyrolysis.
Relative seismic receiver coupling estimation: a method using a probabilistic approach
NASA Astrophysics Data System (ADS)
Landschulze, Marcus; Mjelde, Rolf
2016-09-01
This paper describes a new method called Relative seismic receiver coupling estimation (RCE), a probabilistic approach with ground noise as source signal. The significant benefit of the RCE method is the possibility to obtain a qualitative measurement of the amplitude and phase response of the frequency-band of interest prior to shooting or after installation of the receivers in the field. We derive the RCE function and present measurements with synthetic and field data to validate the usefulness of the method. The method extracts information about the relative ground coupling by comparing two receiver components, or one receiver against a spatially separated receiver to detect relative changes in the soil conditions. This method can also be used to evaluate faulty receiver response. The main advantage of this method is that the receiver response and relative coupling to the ground can be assessed without knowing the receiver transfer-function.
Permeability of the landscape matrix between amphibian breeding sites
Buskirk, Josh
2012-01-01
For organisms that reproduce in discrete habitat patches, land cover between patches (known as the matrix) is important for dispersal among breeding sites. Models of patchy populations often incorporate information on the permeability of the matrix to dispersal, sometimes based on expert opinion. I estimated the relative resistance to gene flow of land cover types and barriers using FST calculated from microsatellite markers in two amphibians, within an 800-km2 area in northern Switzerland. The species included a frog (Rana temporaria: 996 individuals, 48 populations, seven markers) and a newt (Triturus alpestris: 816 individuals, 41 populations, seven markers). Open fields and urban areas were more resistant to gene flow than forested land; roads and highways also reduced permeability. Results were similar for the two species. However, differences in resistance among matrix elements were relatively low: gene flow through urban areas was reduced by only 24–42% relative to forest; a divided highway reduced gene flow by 11–40% and was 7–8 times more resistant than a secondary road. These data offer an empirically based alternative to expert opinion for setting relative resistance values in landscape models. PMID:23301180
Permeability reduction in granite under hydrothermal conditions
Morrow, C.A.; Moore, Diane E.; Lockner, D.A.
2001-01-01
The formation of impermeable fault seals between earthquake events is a feature of many models of earthquake generation, suggesting that earthquake recurrence may depend in part on the rate of permeability reduction of fault zone materials under hydrothermal conditions. In this study, permeability measurements were conducted on intact, fractured, and gouge-bearing Westerly granite at an effective pressure of 50 MPa and at temperatures from 150?? to 500??C, simulating conditions in the earthquake-generating portions of fault zones. Pore fluids were cycled back and forth under a 2 MPa pressure differential for periods of up to 40 days. Permeability of the granite decreased with time t, following the exponential relation k = c(10-rt). For intact samples run between 250?? and 500??C the time constant for permeability decrease r was proportional to temperature and ranged between 0.001 and 0.1 days-1 (i.e., between 0.4 and 40 decades year-1 loss of permeability). Values of r for the lower-temperature experiments differed little from the 250??C runs. In contrast, prefractured samples showed higher rates of permeability decrease at a given temperature. The surfaces of the fractured samples showed evidence of dissolution and mineral growth that increased in abundance with both temperature and time. The experimentally grown mineral assemblages varied with temperature and were consistent with a rock-dominated hydrothermal system. As such mineral deposits progressively seal the fractured samples, their rates of permeability decrease approach the rates for intact rocks at the same temperature. These results place constraints on models of precipitation sealing and suggest that fault rocks may seal at a rate consistent with earthquake recurrence intervals of typical fault zones.
Effect of geocoding errors on traffic-related air pollutant exposure and concentration estimates.
Ganguly, Rajiv; Batterman, Stuart; Isakov, Vlad; Snyder, Michelle; Breen, Michael; Brakefield-Caldwell, Wilma
2015-01-01
Exposure to traffic-related air pollutants is highest very near roads, and thus exposure estimates are sensitive to positional errors. This study evaluates positional and PM2.5 concentration errors that result from the use of automated geocoding methods and from linearized approximations of roads in link-based emission inventories. Two automated geocoders (Bing Map and ArcGIS) along with handheld GPS instruments were used to geocode 160 home locations of children enrolled in an air pollution study investigating effects of traffic-related pollutants in Detroit, Michigan. The average and maximum positional errors using the automated geocoders were 35 and 196 m, respectively. Comparing road edge and road centerline, differences in house-to-highway distances averaged 23 m and reached 82 m. These differences were attributable to road curvature, road width and the presence of ramps, factors that should be considered in proximity measures used either directly as an exposure metric or as inputs to dispersion or other models. Effects of positional errors for the 160 homes on PM2.5 concentrations resulting from traffic-related emissions were predicted using a detailed road network and the RLINE dispersion model. Concentration errors averaged only 9%, but maximum errors reached 54% for annual averages and 87% for maximum 24-h averages. Whereas most geocoding errors appear modest in magnitude, 5% to 20% of residences are expected to have positional errors exceeding 100 m. Such errors can substantially alter exposure estimates near roads because of the dramatic spatial gradients of traffic-related pollutant concentrations. To ensure the accuracy of exposure estimates for traffic-related air pollutants, especially near roads, confirmation of geocoordinates is recommended.
Effect of geocoding errors on traffic-related air pollutant exposure and concentration estimates
Ganguly, Rajiv; Batterman, Stuart; Isakov, Vlad; Snyder, Michelle; Breen, Michael; Brakefield-Caldwell, Wilma
2015-01-01
Exposure to traffic-related air pollutants is highest very near roads, and thus exposure estimates are sensitive to positional errors. This study evaluates positional and PM2.5 concentration errors that result from the use of automated geocoding methods and from linearized approximations of roads in link-based emission inventories. Two automated geocoders (Bing Map and ArcGIS) along with handheld GPS instruments were used to geocode 160 home locations of children enrolled in an air pollution study investigating effects of traffic-related pollutants in Detroit, Michigan. The average and maximum positional errors using the automated geocoders were 35 and 196 m, respectively. Comparing road edge and road centerline, differences in house-to-highway distances averaged 23 m and reached 82 m. These differences were attributable to road curvature, road width and the presence of ramps, factors that should be considered in proximity measures used either directly as an exposure metric or as inputs to dispersion or other models. Effects of positional errors for the 160 homes on PM2.5 concentrations resulting from traffic-related emissions were predicted using a detailed road network and the RLINE dispersion model. Concentration errors averaged only 9%, but maximum errors reached 54% for annual averages and 87% for maximum 24-h averages. Whereas most geocoding errors appear modest in magnitude, 5% to 20% of residences are expected to have positional errors exceeding 100 m. Such errors can substantially alter exposure estimates near roads because of the dramatic spatial gradients of traffic-related pollutant concentrations. To ensure the accuracy of exposure estimates for traffic-related air pollutants, especially near roads, confirmation of geocoordinates is recommended. PMID:25670023
Point Cloud Based Relative Pose Estimation of a Satellite in Close Range.
Liu, Lujiang; Zhao, Gaopeng; Bo, Yuming
2016-06-04
Determination of the relative pose of satellites is essential in space rendezvous operations and on-orbit servicing missions. The key problems are the adoption of suitable sensor on board of a chaser and efficient techniques for pose estimation. This paper aims to estimate the pose of a target satellite in close range on the basis of its known model by using point cloud data generated by a flash LIDAR sensor. A novel model based pose estimation method is proposed; it includes a fast and reliable pose initial acquisition method based on global optimal searching by processing the dense point cloud data directly, and a pose tracking method based on Iterative Closest Point algorithm. Also, a simulation system is presented in this paper in order to evaluate the performance of the sensor and generate simulated sensor point cloud data. It also provides truth pose of the test target so that the pose estimation error can be quantified. To investigate the effectiveness of the proposed approach and achievable pose accuracy, numerical simulation experiments are performed; results demonstrate algorithm capability of operating with point cloud directly and large pose variations. Also, a field testing experiment is conducted and results show that the proposed method is effective.
Point Cloud Based Relative Pose Estimation of a Satellite in Close Range
Liu, Lujiang; Zhao, Gaopeng; Bo, Yuming
2016-01-01
Determination of the relative pose of satellites is essential in space rendezvous operations and on-orbit servicing missions. The key problems are the adoption of suitable sensor on board of a chaser and efficient techniques for pose estimation. This paper aims to estimate the pose of a target satellite in close range on the basis of its known model by using point cloud data generated by a flash LIDAR sensor. A novel model based pose estimation method is proposed; it includes a fast and reliable pose initial acquisition method based on global optimal searching by processing the dense point cloud data directly, and a pose tracking method based on Iterative Closest Point algorithm. Also, a simulation system is presented in this paper in order to evaluate the performance of the sensor and generate simulated sensor point cloud data. It also provides truth pose of the test target so that the pose estimation error can be quantified. To investigate the effectiveness of the proposed approach and achievable pose accuracy, numerical simulation experiments are performed; results demonstrate algorithm capability of operating with point cloud directly and large pose variations. Also, a field testing experiment is conducted and results show that the proposed method is effective. PMID:27271633
Relative pose estimation of satellites using PMD-/CCD-sensor data fusion
NASA Astrophysics Data System (ADS)
Tzschichholz, Tristan; Boge, Toralf; Schilling, Klaus
2015-04-01
Rendezvous & Docking to passive objects, as of relevance for space debris removal, raises new challenges with respect to relative navigation. Whenever the position and orientation (pose) of an object is required in terrestrial and in space applications, sensor systems such as laser scanners and stereo vision systems are often employed. This paper presents an approach to pose estimation using a 3D time-of-flight camera for ranging information in combination with a high resolution grayscale camera. We have designed a pose estimation method that fuses the data streams of the two sensors in order to benefit from each sensors' advantages. A rigorous test campaign on a Real-Time Hardware-In-The-Loop Rendezvous and Docking Simulator - the European Proximity Operations Simulator (EPOS) - was performed in order to evaluate the performance of the resulting algorithm. The proposed pose estimation method does not exceed an average distance error of 3 cm while being capable of providing pose estimates at up to 60 FPS on recent hardware. Thus, when regarding proximity operations, an attractive sensor system is used to characterize the dynamics of the target object for safe approach results.
Point Cloud Based Relative Pose Estimation of a Satellite in Close Range.
Liu, Lujiang; Zhao, Gaopeng; Bo, Yuming
2016-01-01
Determination of the relative pose of satellites is essential in space rendezvous operations and on-orbit servicing missions. The key problems are the adoption of suitable sensor on board of a chaser and efficient techniques for pose estimation. This paper aims to estimate the pose of a target satellite in close range on the basis of its known model by using point cloud data generated by a flash LIDAR sensor. A novel model based pose estimation method is proposed; it includes a fast and reliable pose initial acquisition method based on global optimal searching by processing the dense point cloud data directly, and a pose tracking method based on Iterative Closest Point algorithm. Also, a simulation system is presented in this paper in order to evaluate the performance of the sensor and generate simulated sensor point cloud data. It also provides truth pose of the test target so that the pose estimation error can be quantified. To investigate the effectiveness of the proposed approach and achievable pose accuracy, numerical simulation experiments are performed; results demonstrate algorithm capability of operating with point cloud directly and large pose variations. Also, a field testing experiment is conducted and results show that the proposed method is effective. PMID:27271633
Polygenic heritability estimates in pharmacogenetics: focus on asthma and related phenotypes.
McGeachie, Michael J; Stahl, Eli A; Himes, Blanca E; Pendergrass, Sarah A; Lima, John J; Irvin, Charles G; Peters, Stephen P; Ritchie, Marylyn D; Plenge, Robert M; Tantisira, Kelan G
2013-06-01
Although accurate measures of heritability are required to understand the pharmacogenetic basis of drug treatment response, these are generally not available, as it is unfeasible to give medications to individuals for which treatment is not indicated. Using a polygenic linear mixed modeling approach, we estimated lower bounds on the heritability of asthma and the heritability of two related drug-response phenotypes, bronchodilator response and airway hyperreactivity, using genome-wide single nucleotide polymorphism (SNP) data from existing asthma cohorts. Our estimate of the heritability for bronchodilator response is 28.5% (SE 16%, P=0.043) and airway hyperresponsiveness is 51.1% (SE 34%, P=0.064), whereas we estimate asthma genetic liability at 61.5% (SE 16%, P<0.001). Our results agree with the previously published estimates of the heritability of these traits, suggesting that the linear mixed modeling method is useful for computing the heritability of other pharmacogenetic traits. Furthermore, our results indicate that multiple SNP main effects, including SNPs as yet unidentified by genome-wide association study methods, together explain a sizable portion of the heritability of these traits. PMID:23532052
Strain-dependent permeability of volcanic rocks.
NASA Astrophysics Data System (ADS)
Farquharson, Jamie; Heap, Michael; Baud, Patrick
2016-04-01
We explore permeability evolution during deformation of volcanic materials using a suite of rocks with varying compositions and physical properties (such as porosity ϕ). 40 mm × 20 mm cylindrical samples were made from a range of extrusive rocks, including andesites from Colima, Mexico (ϕ˜0.08; 0.18; 0.21), Kumamoto, Japan (ϕ˜0.13), and Ruapehu, New Zealand (ϕ˜0.15), and basalt from Mt Etna, Italy (ϕ˜0.04). Gas permeability of each sample was measured before and after triaxial deformation using a steady-state benchtop permeameter. To study the strain-dependence of permeability in volcanic rocks, we deformed samples to 2, 3, 4, 6, and 12 % axial strain at a constant strain rate of 10‑5 s‑1. Further, the influence of failure mode - dilatant or compactant - on permeability was assessed by repeating experiments at different confining pressures. During triaxial deformation, porosity change of the samples was monitored by a servo-controlled pore fluid pump. Below an initial porosity of ˜0.18, and at low confining pressures (≤ 20 MPa), we observe a dilatant failure mode (shear fracture formation). With increasing axial strain, stress is accommodated by fault sliding and the generation of ash-sized gouge between the fracture planes. In higher-porosity samples, or at relatively higher confining pressures (≥ 60 MPa), we observe compactant deformation characterised by a monotonous decrease in porosity with increasing axial strain. The relative permeability k' is given by the change in permeability divided by the initial reference state. When behaviour is dilatant, k' tends to be positive: permeability increases with progressive deformation. However, results suggest that after a threshold amount of strain, k' can decrease. k' always is negative (permeability decreases during deformation) when compaction is the dominant behaviour. Our results show that - in the absence of a sealing or healing process - the efficiency of a fault to transmit fluids is
Evaluation of air permeability in layered unsaturated materials.
Switzer, Christine; Kosson, David S
2007-03-20
Field estimation of air permeability is important in the design and operation of soil-vapor extraction systems. Previous models have examined airflow in homogenous soils, incorporating leakage through a low-permeability cap either as a correction to the airflow equation or as a boundary condition. The dual leakage model solution developed here improves upon the previous efforts by adding a leaky lower boundary condition, allowing for the examination of airflow in heterogeneous layered soils. The dual leakage model is applied to the evaluation of pump tests at a pilot soil-vapor extraction system at the Savannah River Site in South Carolina. A thick, low-permeability, stiff clay layer divides the stratigraphy at the site into two units for evaluation. A modified version of the previous model, using the water table as the impermeable lower boundary, is used to evaluate the permeability of the low-permeability stiff clay layer (3.2 x 10(-10) cm(2)) and permeable sand (7.2 x 10(-7) cm(2)) beneath it. The stiff clay permeability estimate is used in the evaluation of the shallow unit. Permeability estimates of the shallow sand (3.8 x 10(-7) cm(2)) and kaolin cap (1.5 x 10(-9)cm(2)) were obtained with the dual leakage model. The shallow unit was evaluated using the previous model for comparison. The effects of anisotropy were investigated with a series of model simulations based on the shallow unit solution. The anisotropy sensitivity analysis suggests that increased anisotropy ratio or decreased axial permeability has a significant impact on the velocity profile at the lower boundary, especially at high values of the anisotropy ratio. This result may increase estimates of SVE removal rates for contaminants located at the interface of the lower boundary, typical of chlorinated solvent contamination.
A method for estimating the relative degree of saponification of xanthophyll sources and feedstuffs.
Fletcher, D L
2006-05-01
Saponification of xanthophyll esters in various feed sources has been shown to improve pigmentation efficiency in broiler skin and egg yolks. Three trials were conducted to evaluate a rapid liquid chromatography procedure for estimating the relative degree of xanthophyll saponification using samples of yellow corn, corn gluten meal, alfalfa, and 6 commercially available marigold meal concentrates. In each trial, samples were extracted using a modification of the 1984 Association of Official Analytical Chemists hot saponification procedure with and without the addition of KOH. A comparison of the chromatography results was used to estimate percent saponification of the original sample by dividing the nonsaponified extraction values by the saponified extraction values. A comparison of the percent saponified xanthophylls for each product (mg/kg) was: yellow corn, 101; corn gluten meal, 78; alfalfa, 97.9; and marigold concentrates A through F, 99.8, 4.6, 99.0, 95.6, 96.8, and 6.6, respectively. These results indicate that a modification of the 1984 Association of Official Analytical Chemists procedure and liquid column chromatography can be used to quickly verify saponification and can be used to estimate the relative degree of saponification of an unknown xanthophyll source.
Efficient and accurate estimation of relative order tensors from λ- maps
NASA Astrophysics Data System (ADS)
Mukhopadhyay, Rishi; Miao, Xijiang; Shealy, Paul; Valafar, Homayoun
2009-06-01
The rapid increase in the availability of RDC data from multiple alignment media in recent years has necessitated the development of more sophisticated analyses that extract the RDC data's full information content. This article presents an analysis of the distribution of RDCs from two media (2D-RDC data), using the information obtained from a λ-map. This article also introduces an efficient algorithm, which leverages these findings to extract the order tensors for each alignment medium using unassigned RDC data in the absence of any structural information. The results of applying this 2D-RDC analysis method to synthetic and experimental data are reported in this article. The relative order tensor estimates obtained from the 2D-RDC analysis are compared to order tensors obtained from the program REDCAT after using assignment and structural information. The final comparisons indicate that the relative order tensors estimated from the unassigned 2D-RDC method very closely match the results from methods that require assignment and structural information. The presented method is successful even in cases with small datasets. The results of analyzing experimental RDC data for the protein 1P7E are presented to demonstrate the potential of the presented work in accurately estimating the principal order parameters from RDC data that incompletely sample the RDC space. In addition to the new algorithm, a discussion of the uniqueness of the solutions is presented; no more than two clusters of distinct solutions have been shown to satisfy each λ-map.
Estimation of Heterogeneity in Diagnostic Parameters of Age-related Diseases.
Blokh, David; Stambler, Ilia
2014-08-01
The heterogeneity of parameters is a ubiquitous biological phenomenon, with critical implications for biological systems functioning in normal and diseased states. We developed a method to estimate the level of objects set heterogeneity with reference to particular parameters and applied it to type II diabetes and heart disease, as examples of age-related systemic dysfunctions. The Friedman test was used to establish the existence of heterogeneity. The Newman-Keuls multiple comparison method was used to determine clusters. The normalized Shannon entropy was used to provide the quantitative evaluation of heterogeneity. There was obtained an estimate for the heterogeneity of the diagnostic parameters in healthy subjects, as well as in heart disease and type II diabetes patients, which was strongly related to their age. With aging, as with the diseases, the level of heterogeneity (entropy) was reduced, indicating a formal analogy between these phenomena. The similarity of the patterns in aging and disease suggested a kind of "early aging" of the diseased subjects, or alternatively a "disease-like" aging process, with reference to these particular parameters. The proposed method and its validation on the chronic age-related disease samples may support a way toward a formal mathematical relation between aging and chronic diseases and a formal definition of aging and disease, as determined by particular heterogeneity (entropy) changes. PMID:25110613
Runtime and Inversion Impacts on Estimation of Moisture Retention Relations by Centrifuge
NASA Astrophysics Data System (ADS)
Sigda, J. M.; Wilson, J. L.
2003-12-01
the impact of different runtimes and different inversion techniques on estimated moisture retention parameters. Moisture retention data were collected for a number of poorly lithified sands and indurated deformed sands using the UFA centrifuge system (Conca and Wright, 1990). Parameters for the van Genuchten model were estimated for short and long runtimes with one inversion technique. Model parameters were re-estimated for one other inversion technique and a simple averaging approach which does not involve inversion. Our results demonstrate that the averaging approach greatly underestimates the van Genuchten n parameter relative to the inversion techniques. Insufficient runtimes also have a significant impact on estimated parameters. Our analysis indicates a need, barring method standardization, for practitioners to include information about inversion technique and runtime criteria when presenting centrifuge moisture retention results.
NASA Astrophysics Data System (ADS)
Kumar, Vikas; Kumar, Dinesh; Chopra, Sumer
2016-10-01
The scaling relation and self similarity of earthquake process have been investigated by estimating the source parameters of 34 moderate size earthquakes (mb 3.4-5.8) occurred in the NW Himalaya. The spectral analysis of body waves of 217 accelerograms recorded at 48 sites have been carried out using in the present analysis. The Brune's ω-2 model has been adopted for this purpose. The average ratio of the P-wave corner frequency, fc(P), to the S-wave corner frequency, fc(S), has been found to be 1.39 with fc(P) > fc(S) for 90% of the events analyzed here. This implies the shift in the corner frequency in agreement with many other similar studies done for different regions. The static stress drop values for all the events analyzed here lie in the range 10-100 bars average stress drop value of the order of 43 ± 19 bars for the region. This suggests the likely estimate of the dynamic stress drop, which is 2-3 times the static stress drop, is in the range of about 80-120 bars. This suggests the relatively high seismic hazard in the NW Himalaya as high frequency strong ground motions are governed by the stress drop. The estimated values of stress drop do not show significant variation with seismic moment for the range 5 × 1014-2 × 1017 N m. This observation along with the cube root scaling of corner frequencies suggests the self similarity of the moderate size earthquakes in the region. The scaling relation between seismic moment and corner frequency Mo fc3 = 3.47 ×1016Nm /s3 estimated in the present study can be utilized to estimate the source dimension given the seismic moment of the earthquake for the hazard assessment. The present study puts the constrains on the important parameters stress drop and source dimension required for the synthesis of strong ground motion from the future expected earthquakes in the region. Therefore, the present study is useful for the seismic hazard and risk related studies for NW Himalaya.
Modeling and syndromic surveillance for estimating weather-induced heat-related illness.
Perry, Alexander G; Korenberg, Michael J; Hall, Geoffrey G; Moore, Kieran M
2011-01-01
This paper compares syndromic surveillance and predictive weather-based models for estimating emergency department (ED) visits for Heat-Related Illness (HRI). A retrospective time-series analysis of weather station observations and ICD-coded HRI ED visits to ten hospitals in south eastern Ontario, Canada, was performed from April 2003 to December 2008 using hospital data from the National Ambulatory Care Reporting System (NACRS) database, ED patient chief complaint data collected by a syndromic surveillance system, and weather data from Environment Canada. Poisson regression and Fast Orthogonal Search (FOS), a nonlinear time series modeling technique, were used to construct models for the expected number of HRI ED visits using weather predictor variables (temperature, humidity, and wind speed). Estimates of HRI visits from regression models using both weather variables and visit counts captured by syndromic surveillance as predictors were slightly more highly correlated with NACRS HRI ED visits than either regression models using only weather predictors or syndromic surveillance counts.
Pulmonary function of U. S. coal miners related to dust exposure estimates
Attfield, M.D.; Hodous, T.K. )
1992-03-01
This study of 7,139 U.S. coal miners used linear regression analysis to relate estimates of cumulative dust exposure to several pulmonary function variables measured during medical examinations undertaken between 1969 and 1971. The exposure data included newly derived cumulative dust exposure estimates for the period up to time of examination based on large data bases of underground airborne dust sampling measurements. Negative associations were found between measures of cumulative exposure and FEV1, FVC, and the FEV1/FVC ratio (p less than 0.001). In general, the relationships were similar to those reported for British coal miners. Overall, the results demonstrate an adverse effect of coal mine dust exposure on pulmonary function that occurs even in the absence of radiographically detected pneumoconiosis.
Measured GFR Does Not Outperform Estimated GFR in Predicting CKD-related Complications
Propert, Kathleen; Xie, Dawei; Hamm, Lee; He, Jiang; Miller, Edgar; Ojo, Akinlolu; Shlipak, Michael; Teal, Valerie; Townsend, Raymond; Weir, Matthew; Wilson, Jillian; Feldman, Harold
2011-01-01
Although many assume that measurement of glomerular filtration rate (GFR) using a marker such as iothalamate (iGFR) is superior to equation-estimated GFR (eGFR), each of these methods has distinct disadvantages. Because physicians often use renal function to guide the screening for various CKD-associated complications, one method to compare the clinical utility of iGFR and eGFR is to determine the strength of their association with CKD-associated comorbidities. Using a subset of 1214 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study, we determined the cross-sectional associations between known complications of CKD and iGFR, eGFR estimated from serum creatinine (eGFR_Cr), and eGFR estimated from cystatin C (eGFR_cysC). We found that none of the measures of renal function strongly associated with CKD complications and that the relative strengths of associations varied according to the outcome of interest. For example, iGFR demonstrated better discrimination than eGFR_Cr and eGFR_cysC for outcomes of anemia and hemoglobin concentration; however, both eGFR_Cr and eGFR_cysC demonstrated better discrimination than iGFR for outcomes of hyperphosphatemia and phosphorus level. iGFR and eGFR had similar strengths of association with hyperkalemia/potassium level and with metabolic acidosis/bicarbonate level. In conclusion, iothalamate measurement of GFR is not consistently superior to equation-based estimations of GFR in explaining CKD-related comorbidities. These results raise questions regarding the conventional view that iGFR is the “gold standard” measure of kidney function. PMID:21921144
Virtual screening of intestinal drug permeability.
Stenberg, P; Luthman, K; Artursson, P
2000-03-01
Lead compounds generated in high throughput drug discovery programmes often have unfavorable biopharmaceutical properties, resulting in a low success rate of such drug candidates in clinical development. Drug companies and researchers would thus like to have methods of predicting biopharmaceutical properties accurately. The intestinal permeability to a lead compound is one such property which is particularly important. Therefore, access to methods to accurately predict biopharmaceutical properties, such as the intestinal permeability of a large series of compounds, is of particular importance. This review deals with new theoretical methods used to predict intestinal drug permeability. There are several possible transport routes across the intestine, but theoretical methods generally deal with only one of them, the passive transcellular route. Therefore, this review will also discuss the relative importance of passive and active drug transport and efflux routes using recent data generated in cell cultures, animal models and human subjects.
NASA Astrophysics Data System (ADS)
Samat, N. A.; Ma'arof, S. H. Mohd Imam
2015-05-01
Disease mapping is a method to display the geographical distribution of disease occurrence, which generally involves the usage and interpretation of a map to show the incidence of certain diseases. Relative risk (RR) estimation is one of the most important issues in disease mapping. This paper begins by providing a brief overview of Chikungunya disease. This is followed by a review of the classical model used in disease mapping, based on the standardized morbidity ratio (SMR), which we then apply to our Chikungunya data. We then fit an extension of the classical model, which we refer to as a Poisson-Gamma model, when prior distributions for the relative risks are assumed known. Both results are displayed and compared using maps and we reveal a smoother map with fewer extremes values of estimated relative risk. The extensions of this paper will consider other methods that are relevant to overcome the drawbacks of the existing methods, in order to inform and direct government strategy for monitoring and controlling Chikungunya disease.
NASA Astrophysics Data System (ADS)
Blackman, Jonathan; Field, Scott; Galley, Chad; Hemberger, Daniel; Scheel, Mark; Schmidt, Patricia; Smith, Rory; SXS Collaboration Collaboration
2016-03-01
We are now in the advanced detector era of gravitational wave astronomy, and the merger of two black holes (BHs) is one of the most promising sources of gravitational waves that could be detected on earth. To infer the BH masses and spins, the observed signal must be compared to waveforms predicted by general relativity for millions of binary configurations. Numerical relativity (NR) simulations can produce accurate waveforms, but are prohibitively expensive to use for parameter estimation. Other waveform models are fast enough but may lack accuracy in portions of the parameter space. Numerical relativity surrogate models attempt to rapidly predict the results of a NR code with a small or negligible modeling error, after being trained on a set of input waveforms. Such surrogate models are ideal for parameter estimation, as they are both fast and accurate, and have already been built for the case of non-spinning BHs. Using 250 input waveforms, we build a surrogate model for waveforms from the Spectral Einstein Code (SpEC) for a subspace of precessing systems.
An Investigation of Quantile Function Estimators Relative to Quantile Confidence Interval Coverage
Wei, Lai; Wang, Dongliang; Hutson, Alan D.
2016-01-01
In this article, we investigate the limitations of traditional quantile function estimators and introduce a new class of quantile function estimators, namely, the semi-parametric tail-extrapolated quantile estimators, which has excellent performance for estimating the extreme tails with finite sample sizes. The smoothed bootstrap and direct density estimation via the characteristic function methods are developed for the estimation of confidence intervals. Through a comprehensive simulation study to compare the confidence interval estimations of various quantile estimators, we discuss the preferred quantile estimator in conjunction with the confidence interval estimation method to use under different circumstances. Data examples are given to illustrate the superiority of the semi-parametric tail-extrapolated quantile estimators. The new class of quantile estimators is obtained by slight modification of traditional quantile estimators, and therefore, should be specifically appealing to researchers in estimating the extreme tails. PMID:26924881
The Permeability of Territorial Space: Some Evidence from Military Warfare.
ERIC Educational Resources Information Center
Khoury, Robert M.
1984-01-01
Investigated military invasions (N=58) of the territorial boundaries of nation-states, and attempted to document empirically the territorial space permeability function. Results showed that the function relating intrusion to discomfort was found to be conspicuously similar to the personal space permeability function described by Hayduk (1981).…
Uchiyama, T; Bessho, T; Akazawa, K
1998-06-01
Static relations between elbow joint angle and torque at constant muscle activity in normal volunteers were investigated with the aid of an artificial neural network technique. A subject sat on a chair and moved his upper- and forearm in a horizontal plane at the height of his shoulder. The subject was instructed to maintain the elbow joint at a pre-determined angle. The wrist was then pulled to extend the elbow joint by the gravitational force of a weight hanging from a pulley. Integrated electromyograms (IEMGs), elbow and shoulder joint angles and elbow joint torque were measured. Then the relation among IEMGs, joint angles and torque was modeled with the aid of the artificial neural network, where IEMGs and joint angles were the inputs and torque was the output. After back propagation learning, we presented various combinations of IEMGs, shoulder and elbow joint angles to the model and estimated the elbow joint torque to obtain the torque-angle relation for constant muscle activation. The elbow joint torque increased and then decreased with extension of the elbow joint. This suggests that if the forearm is displaced from an equilibrium point, the torque angle relation would not act like a simple spring. In a view of the musculoskeletal structure of the elbow joint, the relation between the elbow joint angle and the moment arm of the elbow flexor muscles seems to have a dominant effect on the torque-angle relation. PMID:9755039
Rashid, Mamoon; Pain, Arnab
2013-01-01
Summary: READSCAN is a highly scalable parallel program to identify non-host sequences (of potential pathogen origin) and estimate their genome relative abundance in high-throughput sequence datasets. READSCAN accurately classified human and viral sequences on a 20.1 million reads simulated dataset in <27 min using a small Beowulf compute cluster with 16 nodes (Supplementary Material). Availability: http://cbrc.kaust.edu.sa/readscan Contact: arnab.pain@kaust.edu.sa or raeece.naeem@gmail.com Supplementary information: Supplementary data are available at Bioinformatics online. PMID:23193222
Prevalence estimates of combat-related post-traumatic stress disorder: critical review.
Richardson, Lisa K; Frueh, B Christopher; Acierno, Ronald
2010-01-01
The aim of the present study was to provide a critical review of prevalence estimates of combat-related post-traumatic stress disorder (PTSD) among military personnel and veterans, and of the relevant factors that may account for the variability of estimates within and across cohorts, including methodological and conceptual factors accounting for differences in prevalence rates across nations, conflicts/wars, and studies. MEDLINE and PsycINFO databases were examined for literature on combat-related PTSD. The following terms were used independently and in combinations in this search: PTSD, combat, veterans, military, epidemiology, prevalence. The point prevalence of combat-related PTSD in US military veterans since the Vietnam War ranged from approximately 2% to 17%. Studies of recent conflicts suggest that combat-related PTSD afflicts between 4% and 17% of US Iraq War veterans, but only 3-6% of returning UK Iraq War veterans. Thus, the prevalence range is narrower and tends to have a lower ceiling among combat veterans of non-US Western nations. Variability in prevalence is likely due to differences in sampling strategies; measurement strategies; inclusion and measurement of the DSM-IV clinically significant impairment criterion; timing and latency of assessment and potential for recall bias; and combat experiences. Prevalence rates are also likely affected by issues related to PTSD course, chronicity, and comorbidity; symptom overlap with other psychiatric disorders; and sociopolitical and cultural factors that may vary over time and by nation. The disorder represents a significant and costly illness to veterans, their families, and society as a whole. Further carefully conceptualized research, however, is needed to advance our understanding of disorder prevalence, as well as associated information on course, phenomenology, protective factors, treatment, and economic costs.
A tool for computing time-dependent permeability reduction of fractured volcanic conduit margins.
NASA Astrophysics Data System (ADS)
Farquharson, Jamie; Wadsworth, Fabian; Heap, Michael; Baud, Patrick
2016-04-01
Laterally-oriented fractures within volcanic conduit margins are thought to play an important role in tempering eruption explosivity by allowing magmatic volatiles to outgas. The permeability of a fractured conduit margin - the equivalent permeability - can be modelled as the sum of permeability contributions of the edifice host rock and the fracture(s) within it. We present here a flexible MATLAB® tool which computes the time-dependent equivalent permeability of a volcanic conduit margin containing ash-filled fractures. The tool is designed so that the end-user can define a wide range of input parameters to yield equivalent permeability estimates for their application. The time-dependence of the equivalent permeability is incorporated by considering permeability decrease as a function of porosity loss in the ash-filled fractures due to viscous sintering (after Russell and Quane, 2005), which is in turn dependent on the depth and temperature of each fracture and the crystal-content of the magma (all user-defined variables). The initial viscosity of the granular material filling the fracture is dependent on the water content (Hess and Dingwell, 1996), which is computed assuming equilibrium depth-dependent water content (Liu et al., 2005). Crystallinity is subsequently accounted for by employing the particle-suspension rheological model of Mueller et al. (2010). The user then defines the number of fractures, their widths, and their depths, and the lengthscale of interest (e.g. the length of the conduit). Using these data, the combined influence of transient fractures on the equivalent permeability of the conduit margin is then calculated by adapting a parallel-plate flow model (developed by Baud et al., 2012 for porous sandstones), for host rock permeabilities from 10-11 to 10-22 m2. The calculated values of porosity and equivalent permeability with time for each host rock permeability is then output in text and worksheet file formats. We introduce two dimensionless
Methods for estimating dispersal probabilities and related parameters using marked animals
Bennetts, R.E.; Nichols, J.D.; Pradel, R.; Lebreton, J.D.; Kitchens, W.M.; Clobert, Jean; Danchin, Etienne; Dhondt, Andre A.; Nichols, James D.
2001-01-01
Deriving valid inferences about the causes and consequences of dispersal from empirical studies depends largely on our ability reliably to estimate parameters associated with dispersal. Here, we present a review of the methods available for estimating dispersal and related parameters using marked individuals. We emphasize methods that place dispersal in a probabilistic framework. In this context, we define a dispersal event as a movement of a specified distance or from one predefined patch to another, the magnitude of the distance or the definition of a `patch? depending on the ecological or evolutionary question(s) being addressed. We have organized the chapter based on four general classes of data for animals that are captured, marked, and released alive: (1) recovery data, in which animals are recovered dead at a subsequent time, (2) recapture/resighting data, in which animals are either recaptured or resighted alive on subsequent sampling occasions, (3) known-status data, in which marked animals are reobserved alive or dead at specified times with probability 1.0, and (4) combined data, in which data are of more than one type (e.g., live recapture and ring recovery). For each data type, we discuss the data required, the estimation techniques, and the types of questions that might be addressed from studies conducted at single and multiple sites.
Evaluation of the permeability of agricultural films to various fumigants.
Qian, Yaorong; Kamel, Alaa; Stafford, Charles; Nguyen, Thuy; Chism, William J; Dawson, Jeffrey; Smith, Charles W
2011-11-15
A variety of agricultural films are commercially available for managing emissions and enhancing pest control during soil fumigation. These films are manufactured using different materials and processes which can ultimately result in different permeability to fumigants. A systematic laboratory study of the permeability of the agricultural films to nine fumigants was conducted to evaluate the performance of commonly used film products, including polyethylene, metalized, and high-barrier films. The permeability, as expressed by mass transfer coefficient (cm/h), of 27 different films from 13 manufacturers ranged from below 1 × 10(-4) cm/h to above 10 cm/h at 25 °C under ambient relative humidity test conditions. The wide range in permeability of commercially available films demonstrates the need to use films which are appropriate for the fumigation application. The effects of environmental factors, such as temperature and humidity, on the film permeability were also investigated. It was found that high relative humidity could drastically increase the permeability of the high-barrier films. The permeability of some high-barrier films was increased by 2-3 orders of magnitude when the films were tested at high relative humidity. Increasing the temperature from 25 to 40 °C increased the permeability for some high-barrier films up to 10 times more than the permeability at 25 °C, although the effect was minimal for several of these films. Analysis of the distribution of the permeability of the films under ambient humidity conditions to nine fumigants indicated that the 27 films largely followed the material type, although the permeability varied considerably among the films of similar material.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-03-13
... Estimating Methodologies for Broiler Animal Feeding Operations and Lagoons and Basins for Swine and Dairy... Estimating Methodologies for Broiler Animal Feeding Operations'' and ``Development of Emissions Estimating...'s draft emissions estimating methodologies for determining daily and annual emissions from a...
Influence of decenylsuccinic Acid on water permeability of plant cells.
Lee, O Y; Stadelmann, E J; Weiser, C J
1972-11-01
Decenylsuccinic acid altered permeability to water of epidermal cells of bulb scales of Allium cepa and of the leaf midrib of Rhoeo discolor. Water permeability, as determined by deplasmolysis time measurements, was related to the dose of undissociated decenylsuccinic acid (mm undissociated decenylsuccinic acid x minute). No relationship was found between permeability and total dose of decenylsuccinic acid, or dose of dissociated decenylsuccinic acid, suggesting that the undissociated molecule was the active factor in permeability changes and injury.At doses which did not damage cells (0.0008 to 0.6 [mm of the undissociated molecule x minute]) decenylsuccinic acid decreased water permeability. At higher doses (e.g., 4 to 8 [mm x minute]) injury to cells was common and decenylsuccinic acid increased permeability. Doses above the 10 to 20 (mm x minute) range were generally lethal. The plasmolysis form of uninjured cells was altered and protoplasmic swelling occasionally was observed. The dose-dependent reversal of water permeability changes (decreased to increased permeability) may reflect decenylsuccinic acid-induced changes in membrane structure. Reported effects of decenylsuccinic acid on temperature dependence of permeability and frost resistance were not verified. PMID:16658227
IMPACT OF CURING TEMPERATURE ON THE SATURATED LIQUID PERMEABILITY OF SALTSTONE
Williams, F.; Harbour, J.
2011-02-14
E and hydraulic conductivity. Therefore, it is possible to use E values to estimate the values of hydraulic conductivity. Measurement of Young's modulus is much easier than the measurement of permeability of Saltstone mixes and facilitates the measurement of the time dependence hydraulic conductivity. The results presented in this report show that changes in permeability as a function of curing temperature appear to be related to microstructural changes in the cured Saltstone mixes. Backscattered electron microscopy images revealed significant differences between the samples cured at different temperatures.
The geometric mean concept for interpreting the permeability of heterogeneous geomaterials
NASA Astrophysics Data System (ADS)
Selvadurai, Patrick; Selvadurai, Paul
2015-04-01
Naturally occurring geomaterials are heterogeneous and the estimation of the effective permeability characteristics of such geomaterials presents a challenge not only in terms of the experimental procedures that should be used to ensure flow through the porous medium but also in the correct use of the theoretical concepts needed to accurately interpret the data. The general consensus is that the flow path in a test needs to be drastically reduced if steady state tests are considered as a suitable experimental technique. The disadvantage of flow path reduction is that the tested volume may not be altogether representative of the rock, particularly if it displays heterogeneity in the scale of the sample being tested. Also, if the sample is not correctly restrained, the differential pressures needed to initiate steady flow can introduce damage in the sample leading to erroneous estimates of permeability. The alternative approach is to use large enough samples that can capture the spatial heterogeneity but develop testing procedures that can test examine the steady state flow process as a problem in three-dimensional fluid flow that can capture the spatial distribution of permeability. The paper discusses theoretical and computational approaches that have been developed for the estimation of the spatial distribution of permeability in a cuboidal Indiana Limestone sample measuring 450 mm. The "Patch Permeability Test" developed in connection with the research allows the measurements of the surface permeability of the block and through kriging techniques estimate the permeability within the block sample. The research promotes the use of the "Geometric Mean" concept for the description of the effective permeability of the heterogeneous porous medium where the spatial distribution conforms to a lognormal pattern. The effectiveness of the approach is that the techniques can be applied to examine the effective permeability of heterogeneous low permeability materials such as
Permeability of alkaline magmas: a study from Campi Flegrei, Italy
NASA Astrophysics Data System (ADS)
Polacci, M.; Bouvet de Maissoneuve, C.; Giordano, D.; Piochi, M.; Degruyter, W.; Bachmann, O.; Mancini, L.
2012-04-01
Knowledge of permeability is of paramount importance for understanding the evolution of magma degassing during pre-, syn- and post-eruptive volcanic processes. Most permeability estimates existing to date refer to magmas of calc-alkaline compositions. We report here the preliminary results of permeability measurements performed on alkali-trachyte products erupted from the Campanian Ignimbrite (CI) and Monte Nuovo (MTN), two explosive eruptions from Campi Flegrei (CF), an active, hazardous caldera west of Naples, Southern Italy. Darcian (viscous) permeability spans a wide range between 10^-11 and 10^-14 m^2. We observe that the most permeable samples are the scoria clasts from the upper units of MTN; pumice samples from the Breccia Museo facies of CI are instead the least permeable. Non-Darcian (inertial) permeability follows the same trend as Darcian permeability. The first implication of this study is that porosity in alkaline as well as calc-alkaline magmas does not exert a first order control on permeability (e.g. the MTN samples are the most permeable but not the most porous). Second, sample geometry exhibits permeability anisotropy (higher permeability in the direction of vesicle elongation), suggesting stronger degassing in the vertical direction in the conduit. In addition, inertial effects are higher across the sample. As inertial effects are potentially generated by tortuosity (or tortuous vesicle paths), tortuosity is likely higher horizontally than vertically in the conduit. Finally, the measured CF permeability values overlap with those of rhyolitic pumice clasts from the Kos Plateau Tuff (Bouvet de Maisonneuve et al., 2009), together with CI one of the major Quaternary explosive eruptions of the Mediterranean region. This indicates that gas flow is strongly controlled by the geometry of the porous media, which is generated by the bubble dynamics during magma ascent. Therefore, permeability will depend on composition through the rheological properties
NASA Astrophysics Data System (ADS)
Taylor, Bettina B.; Taylor, Marc H.; Dinter, Tilman; Bracher, Astrid
2013-06-01
Phycobiliproteins are a family of water-soluble pigment proteins that play an important role as accessory or antenna pigments and absorb in the green part of the light spectrum poorly used by chlorophyll a. The phycoerythrins (PEs) are one of four types of phycobiliproteins that are generally distinguished based on their absorption properties. As PEs are water soluble, they are generally not captured with conventional pigment analysis. Here we present a statistical model based on in situ measurements of three transatlantic cruises which allows us to derive relative PE concentration from standardized hyperspectral underwater radiance measurements (Lu). The model relies on Empirical Orthogonal Function (EOF) analysis of Lu spectra and, subsequently, a Generalized Linear Model with measured PE concentrations as the response variable and EOF loadings as predictor variables. The method is used to predict relative PE concentrations throughout the water column and to calculate integrated PE estimates based on those profiles.
1999-05-19
Version 00 RELAP4/MOD7/101 performs best estimate analyses of nuclear reactors or related systems undergoing a transient. Transient thermal-hydraulic, two-phase phenomena are calculated from formulations of one-dimensional, homogeneous, equilibrium conservation equations for water mass, momentum, and energy. Heat structures are modeled using a transient one-dimensional heat conduction solution that is coupled to the fluid through heat transfer relations. Various explicit models are used to calculate nonhomogeneous, nonequilibrium behavior including a phase separation model, a vertical slipmore » model, and a nonequilibrium model. Other models are used to represent critical flow, reactor kinetics, pressurized water reactor reflood behavior, nuclear fuel rod swelling and blockage, and components such as pumps, valves, and accumulators.« less
White, Erick A; Horne, Alan; Runciman, Jill; Orazem, Mark E; Navidi, William C; Roper, Clive S; Bunge, Annette L
2011-12-01
The objective of this study was to quantitatively compare measurements of tritiated water permeability with impedance determined at either 100 or 1000 Hz using an LCR databridge on the same pieces of skin. A previously published expression based on a simple circuit of a parallel resistor and constant phase element (CPE) was used to relate (RPARA) measured at different frequencies to the DC resistance (RskinA) and the steady-state skin permeability of tritiated water (kp). Using this analysis, kp and (RPARA) data from three laboratories were shown to be consistent with each other, and kp and (RskinA) estimated from (RPARA) were linearly correlated. Compared with urea and mannitol, which are known to permeate skin through a polar pathway, the value of kp for water was found to be about two times larger than expected for transport through only the polar pathway, suggesting an approximately equal contribution from the lipophilic pathway. Equations relating kp to (RPARA) and (RskinA) were used to compare on a consistent basis proposed tests for identifying and excluding damaged skin from chemical absorption studies. The criterion of 20 kΩ cm2 for (RskinA) corresponds to a tritiated water permeability of 3.2×10(-3) cm/h, which should exclude damaged skin without screening undamaged but higher permeability skin samples from study.
Effect of distance-related heterogeneity on population size estimates from point counts
Efford, Murray G.; Dawson, Deanna K.
2009-01-01
Point counts are used widely to index bird populations. Variation in the proportion of birds counted is a known source of error, and for robust inference it has been advocated that counts be converted to estimates of absolute population size. We used simulation to assess nine methods for the conduct and analysis of point counts when the data included distance-related heterogeneity of individual detection probability. Distance from the observer is a ubiquitous source of heterogeneity, because nearby birds are more easily detected than distant ones. Several recent methods (dependent double-observer, time of first detection, time of detection, independent multiple-observer, and repeated counts) do not account for distance-related heterogeneity, at least in their simpler forms. We assessed bias in estimates of population size by simulating counts with fixed radius w over four time intervals (occasions). Detection probability per occasion was modeled as a half-normal function of distance with scale parameter sigma and intercept g(0) = 1.0. Bias varied with sigma/w; values of sigma inferred from published studies were often 50% for a 100-m fixed-radius count. More critically, the bias of adjusted counts sometimes varied more than that of unadjusted counts, and inference from adjusted counts would be less robust. The problem was not solved by using mixture models or including distance as a covariate. Conventional distance sampling performed well in simulations, but its assumptions are difficult to meet in the field. We conclude that no existing method allows effective estimation of population size from point counts.
Source estimation with surface-related multiples—fast ambiguity-resolved seismic imaging
NASA Astrophysics Data System (ADS)
Tu, Ning; Aravkin, Aleksandr; van Leeuwen, Tristan; Lin, Tim; Herrmann, Felix J.
2016-06-01
We address the problem of obtaining a reliable seismic image without prior knowledge of the source wavelet, especially from data that contain strong surface-related multiples. Conventional reverse-time migration requires prior knowledge of the source wavelet, which is either technically or computationally challenging to accurately determine; inaccurate estimates of the source wavelet can result in seriously degraded reverse-time migrated images, and therefore wrong geological interpretations. To solve this problem, we present a `wavelet-free' imaging procedure that simultaneously inverts for the source wavelet and the seismic image, by tightly integrating source estimation into a fast least-squares imaging framework, namely compressive imaging, given a reasonably accurate background velocity model. However, this joint inversion problem is difficult to solve as it is plagued with local minima and the ambiguity with respect to amplitude scalings because of the multiplicative, and therefore nonlinear, appearance of the source wavelet in the otherwise linear formalism. We have found a way to solve this nonlinear joint-inversion problem using a technique called variable projection, and a way to overcome the scaling ambiguity by including surface-related multiples in our imaging procedure following recent developments in surface-related multiple prediction by sparse inversion. As a result, we obtain without prior knowledge of the source wavelet high-resolution seismic images, comparable in quality to images obtained assuming the true source wavelet is known. By leveraging the computationally efficient compressive-imaging methodology, these results are obtained at affordable computational costs compared with conventional processing work flows that include surface-related multiple removal and reverse-time migration.
How should detection probability be incorporated into estimates of relative abundance?
MacKenzie, D.I.; Kendall, W.L.
2002-01-01
Determination of the relative abundance of two populations, separated by time or space, is of interest in many ecological situations. We focus on two estimators of relative abundance, which assume that the probability that an individual is detected at least once in the survey is either equal or unequal for the two populations. We present three methods for incorporating the collected information into our inference. The first method, proposed previously, is a traditional hypothesis test for evidence that detection probabilities are unequal. However, we feel that, a priori, it is more likely that detection probabilities are actually different; hence, the burden of proof should be shifted, requiring evidence that detection probabilities are practically equivalent. The second method we present, equivalence testing, is one approach to doing so. Third, we suggest that model averaging could be used by combining the two estimators according to derived model weights. These differing approaches are applied to a mark-recapture experiment on Nuttail's cottontail rabbit (Sylvilagus nuttallii) conducted in central Oregon during 1974 and 1975, which has been previously analyzed by other authors.
Surficial permeability of the axial valley seafloor: Endeavour Segment, Juan de Fuca Ridge
NASA Astrophysics Data System (ADS)
Hearn, Casey K.; Homola, Kira L.; Johnson, H. Paul
2013-09-01
Hydrothermal systems at mid-ocean spreading centers play a fundamental role in Earth's geothermal budget. One underexamined facet of marine hydrothermal systems is the role that permeability of the uppermost seafloor veneer plays in the distribution of hydrothermal fluid. As both the initial and final vertical gateway for subsurface fluid circulation, uppermost seafloor permeability may influence the local spatial distribution of hydrothermal flow. A method of deriving a photomosaic from seafloor video was developed and utilized to estimate relative surface permeability in an active hydrothermal area on the Endeavour Segment of the Juan de Fuca Ridge. The mosaic resolves seafloor geology of the axial valley seafloor at submeter resolution over an area greater than 1 km2. Results indicate that the valley walls and basal talus slope are topographically rugged and unsedimented, providing minimal resistance to fluid transmission. Elsewhere, the axial valley floor is capped by an unbroken blanket of low-permeability sediment, resisting fluid exchange with the subsurface reservoir. Active fluid emission sites were restricted to the high-permeability zone at the base of the western wall. A series of inactive fossil hydrothermal structures form a linear trend along the western bounding wall, oriented orthogonal to the spreading axis. High-temperature vent locations appear to have migrated over 100 m along-ridge-strike over the decade between surveys. While initially an expression of subsurface faulting, this spatial pattern suggests that increases in seafloor permeability from sedimentation may be at least a secondary contributing factor in regulating fluid flow across the seafloor interface.
NASA Astrophysics Data System (ADS)
Chapman, Steven W.; Parker, Beth L.; Sale, Tom C.; Doner, Lee Ann
2012-08-01
It is now widely recognized that contaminant release from low permeability zones can sustain plumes long after primary sources are depleted, particularly for chlorinated solvents where regulatory limits are orders of magnitude below source concentrations. This has led to efforts to appropriately characterize sites and apply models for prediction incorporating these effects. A primary challenge is that diffusion processes are controlled by small-scale concentration gradients and capturing mass distribution in low permeability zones requires much higher resolution than commonly practiced. This paper explores validity of using numerical models (HydroGeoSphere, FEFLOW, MODFLOW/MT3DMS) in high resolution mode to simulate scenarios involving diffusion into and out of low permeability zones: 1) a laboratory tank study involving a continuous sand body with suspended clay layers which was 'loaded' with bromide and fluorescein (for visualization) tracers followed by clean water flushing, and 2) the two-layer analytical solution of Sale et al. (2008) involving a relatively simple scenario with an aquifer and underlying low permeability layer. All three models are shown to provide close agreement when adequate spatial and temporal discretization are applied to represent problem geometry, resolve flow fields and capture advective transport in the sands and diffusive transfer with low permeability layers and minimize numerical dispersion. The challenge for application at field sites then becomes appropriate site characterization to inform the models, capturing the style of the low permeability zone geometry and incorporating reasonable hydrogeologic parameters and estimates of source history, for scenario testing and more accurate prediction of plume response, leading to better site decision making.
Chapman, Steven W; Parker, Beth L; Sale, Tom C; Doner, Lee Ann
2012-08-01
It is now widely recognized that contaminant release from low permeability zones can sustain plumes long after primary sources are depleted, particularly for chlorinated solvents where regulatory limits are orders of magnitude below source concentrations. This has led to efforts to appropriately characterize sites and apply models for prediction incorporating these effects. A primary challenge is that diffusion processes are controlled by small-scale concentration gradients and capturing mass distribution in low permeability zones requires much higher resolution than commonly practiced. This paper explores validity of using numerical models (HydroGeoSphere, FEFLOW, MODFLOW/MT3DMS) in high resolution mode to simulate scenarios involving diffusion into and out of low permeability zones: 1) a laboratory tank study involving a continuous sand body with suspended clay layers which was 'loaded' with bromide and fluorescein (for visualization) tracers followed by clean water flushing, and 2) the two-layer analytical solution of Sale et al. (2008) involving a relatively simple scenario with an aquifer and underlying low permeability layer. All three models are shown to provide close agreement when adequate spatial and temporal discretization are applied to represent problem geometry, resolve flow fields and capture advective transport in the sands and diffusive transfer with low permeability layers and minimize numerical dispersion. The challenge for application at field sites then becomes appropriate site characterization to inform the models, capturing the style of the low permeability zone geometry and incorporating reasonable hydrogeologic parameters and estimates of source history, for scenario testing and more accurate prediction of plume response, leading to better site decision making. PMID:22750557
Singh, Gitanjali M.; Micha, Renata; Khatibzadeh, Shahab; Lim, Stephen; Ezzati, Majid; Mozaffarian, Dariush
2015-01-01
Background Sugar-sweetened beverages (SSBs) are consumed globally and contribute to adiposity. However, the worldwide impact of SSBs on burdens of adiposity-related cardiovascular diseases (CVD), cancers, and diabetes has not been assessed by nation, age, and sex. Methods and Results We modeled global, regional, and national burdens of disease associated with SSB consumption by age/sex in 2010. Data on SSB consumption levels were pooled from national dietary surveys worldwide. The effects of SSB intake on BMI and diabetes, and of elevated BMI on CVD, diabetes, and cancers were derived from large prospective cohort pooling studies. Disease-specific mortality/morbidity data were obtained from Global Burden of Diseases, Injuries, and Risk Factors 2010 Study. We computed cause-specific population-attributable fractions for SSB consumption, which were multiplied by cause-specific mortality/morbidity to compute estimates of SSB-attributable death/disability. Analyses were done by country/age/sex; uncertainties of all input data were propagated into final estimates. Worldwide, the model estimated 184,000(95%UI=161,000–208,000) deaths/year attributable to SSB consumption: 133,000(126,000–139,000) from diabetes, 45,000(26,000–61,000) from CVD, and 6,450(4,300–8,600) from cancers. 5.0% of SSB-related deaths occurred in low-income, 70.9% in middle-income, and 24.1% in high-income countries. Proportional mortality due to SSBs ranged from <1% in Japanese >65y to 30% in Mexicans <45y. Among the 20 most populous countries, Mexico had largest absolute (405 deaths/million adults) and proportional (12.1%) deaths from SSBs. A total of 8.5(2.8, 19.2) million disability-adjusted life years (DALYs) were related to SSB intake (4.5% of diabetes-related DALYs). Conclusions SSBs, are a single, modifiable component of diet, that can impact preventable death/disability in adults in high, middle, and low-income countries, indicating an urgent need for strong global prevention programs
Comparability of National Estimates for Traumatic Brain Injury-Related Medical Encounters
Taylor, Christopher A.; Greenspan, Arlene I.; Xu, Likang; Kresnow, Marcie-jo
2015-01-01
Objective To describe similarities and differences in the number of civilian traumatic brain injury (TBI)-related hospitalizations and emergency department visits between national databases that capture US hospital data. Participants TBI-related hospitalizations included in the National Hospital Discharge Survey (NHDS) and Healthcare Cost and Utilization Project Nationwide Inpatient Sample (HCUP-NIS) and emergency department visits in the National Hospital Ambulatory Medical Care Survey (NHAMCS) and HCUP Nationwide Emergency Department Sample (HCUP-NEDS) for 2006–2010. Design Cross-sectional design. Main Measures Nationwide counts of TBI-related medical encounters. Results Overall, the frequency of TBI is comparable when comparing NHDS with HCUP-NIS and NHAMCS with HCUP-NEDS. However, annual counts in both NHDS and NHAMCS are consistently unstable when examined in smaller subgroups, such as by age group and injury mechanism. Injury mechanism is consistently missing from many more records in NHDS compared with HCUP-NIS. Conclusion Given the large sample size of HCUP-NIS and HCUP-NEDS, these data can offer a valuable resource for examining TBI-related hospitalization and emergency department visits, especially by subgroup. These data hold promise for future examinations of annual TBI counts, but ongoing comparisons with national probability samples will be necessary to ensure that HCUP continues to track with estimates from these data. PMID:25955702
2013-01-01
Background HPV is related to a number of cancer types, causing a considerable burden in both genders in Europe. Female vaccination programs can substantially reduce the incidence of HPV-related diseases in women and, to some extent, men through herd immunity. The objective was to estimate the incremental benefit of vaccinating boys and girls using the quadrivalent HPV vaccine in Europe versus girls-only vaccination. Incremental benefits in terms of reduction in the incidence of HPV 6, 11, 16 and 18-related diseases (including cervical, vaginal, vulvar, anal, penile, and head and neck carcinomas and genital warts) were assessed. Methods The analysis was performed using a model constructed in Microsoft®Excel, based on a previously-published dynamic transmission model of HPV vaccination and published European epidemiological data on incidence of HPV-related diseases. The incremental benefits of vaccinating 12-year old girls and boys versus girls-only vaccination was assessed (70% vaccine coverage were assumed for both). Sensitivity analyses around vaccine coverage and duration of protection were performed. Results Compared with screening alone, girls-only vaccination led to 84% reduction in HPV 16/18-related carcinomas in females and a 61% reduction in males. Vaccination of girls and boys led to a 90% reduction in HPV 16/18-related carcinomas in females and 86% reduction in males versus screening alone. Relative to a girls-only program, vaccination of girls and boys led to a reduction in female and male HPV-related carcinomas of 40% and 65%, respectively and a reduction in the incidence of HPV 6/11-related genital warts of 58% for females and 71% for males versus girls-only vaccination. Conclusions In Europe, the vaccination of 12-year old boys and girls against HPV 6, 11, 16 and 18 would be associated with substantial additional clinical benefits in terms of reduced incidence of HPV-related genital warts and carcinomas versus girls-only vaccination. The incremental
Quantifying tight-gas sandstone permeability via critical path analysis
Technology Transfer Automated Retrieval System (TEKTRAN)
Rock permeability has been actively investigated over the past several decades by the geosciences community. However, its accurate estimation still presents significant technical challenges, especially in spatially complex rocks. In this letter, we apply critical path analysis (CPA) to estimate perm...
Inter-system biases estimation in multi-GNSS relative positioning with GPS and Galileo
NASA Astrophysics Data System (ADS)
Deprez, Cecile; Warnant, Rene
2016-04-01
The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the European Galileo program has experienced major progress in 2015 with the launch of 6 satellites belonging to the new Full Operational Capability (FOC) generation. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on GPS and Galileo overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. Once these biases estimated and removed from the model, a solution involving a unique pivot satellite for the two considered constellations can be obtained. Such an approach implies that the addition of even one single Galileo satellite to the GPS-only model will strengthen it. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependant error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs is conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 5 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS and Galileo standalone solutions.
NASA Astrophysics Data System (ADS)
Misra, Gaurav; Izadi, Maziar; Sanyal, Amit; Scheeres, Daniel
2016-04-01
The effects of dynamical coupling between the rotational (attitude) and translational (orbital) motion of spacecraft near small Solar System bodies is investigated. This coupling arises due to the weak gravity of these bodies, as well as solar radiation pressure. The traditional approach assumes a point-mass spacecraft model to describe the translational motion of the spacecraft, while the attitude motion is considered to be completely decoupled from the translational motion. The model used here to describe the rigid-body spacecraft dynamics includes the non-uniform rotating gravity field of the small body up to second degree and order along with the attitude dependent terms, solar tide, and solar radiation pressure. This model shows that the second degree and order gravity terms due to the small body affect the dynamics of the spacecraft to the same extent as the orbit-attitude coupling due to the primary gravity (zeroth order) term. Variational integrators are used to simulate the dynamics of both the rigid spacecraft and the point mass. The small bodies considered here are modeled after Near-Earth Objects (NEO) 101955 Bennu, and 25143 Itokawa, and are assumed to be triaxial ellipsoids with uniform density. Differences in the numerically obtained trajectories of a rigid spacecraft and a point mass are then compared, to illustrate the impact of the orbit-attitude coupling on spacecraft dynamics in proximity of small bodies. Possible implications on the performance of model-based spacecraft control and on the station-keeping budget, if the orbit-attitude coupling is not accounted for in the model of the dynamics, are also discussed. An almost globally asymptotically stable motion estimation scheme based solely on visual/optical feedback that estimates the relative motion of the asteroid with respect to the spacecraft is also obtained. This estimation scheme does not require a model of the dynamics of the asteroid, which makes it perfectly suited for asteroids whose
Estimating head-related transfer functions of human subjects from pressure-velocity measurements.
Hiipakka, Marko; Kinnari, Teemu; Pulkki, Ville
2012-05-01
Direct measurements of individual head-related transfer functions (HRTFs) with a probe microphone at the eardrum are unpleasant, risky, and unreliable and therefore have not been widely used. Instead, the HRTFs are commonly measured from the blocked ear canal entrance, which excludes the effects of the individual ear canals and eardrums. This paper presents a method that allows obtaining individually correct magnitude frequency responses of HRTFs at the eardrum from pressure-velocity (PU) measurements at the ear canal entrance with a miniature PU sensor. The HRTFs of 25 test subjects with nine directions of sound incidence were estimated using real anechoic measurements and an energy-based estimation method. To validate the approach, measurements were also conducted with probe microphones near the eardrums as well as at blocked ear canal entrances. Comparisons between the different methods show that the method presented is a valid and reliable technique for obtaining magnitude frequency responses of HRTFs. The HRTF filters designed using the PU measurements are also shown to yield more correct frequency responses at the eardrum than the filters designed using measurements from the blocked ear canal entrance.
But other than mesothelioma? An estimate of the proportion of work-related cancers in Quebec
Labrèche, F.; Duguay, P.; Boucher, A.; Arcand, R.
2016-01-01
Background More than 30 exposures in the workplace are proven carcinogens. In the present study, we aimed to estimate the burden of occupational cancer in Quebec so as to increase awareness among stakeholders and to prioritize research activities. Methods Work-attributable fractions—that is, the proportions of cancers attributable to work—as published in Finland and the United Kingdom were applied to Quebec 2002–2006 cancer incidence and mortality data to estimate the number of work-related cases for 28 cancer sites. Results Overall, 6.0% of incident cancers (men: 9.1%; women: 2.7%) and 7.6% of cancer deaths (men: 11.8%; women: 2.8%) could be attributable to work, resulting annually in an average of 2160 new cancer diagnoses and 1190 cancer deaths in Quebec. Incident cancers of the lung, prostate, skin, bladder, and (female) breast were the most numerous; cancer sites resulting in more deaths were lung, (female) breast, and pleura. During the same period, compensation statistics reported annual averages of 94.3 incident cancers and 61.9 cancer deaths, mostly involving mesothelioma (64% of compensated incident cancers) and lung cancer (30% of compensated incident cancers). Conclusions Increased recognition of workplace cancers by all stakeholders, from workers and employers to treating physicians, will foster appropriate preventive measures for safer workplaces. PMID:27122983
Estimation of single event-related potentials utilizing the Prony method.
Hansson, M; Gänsler, T; Salomonsson, G
1996-10-01
This paper deals with estimation of the waveform of a single event-related potential, sERP. An additive noise model is used for the measured signal and the SNR of the disturbed sERP is approximately 0 dB. The sERP is described by a series expansion where the basis functions are damped sinusoids. The fundamental basis function is estimated by the least squares Prony method, derived for colored noise. The performance of the Prony method for different forms of the power density spectrum of the noise is investigated. A white noise approximation can be used at a low signal-to-noise (SNR). The basis functions change slowly but the waveform of the sERP may vary from one stimulus to another, thus we average a small number of correlation functions in order to increase the SNR. The method is evaluated by using measurements from four subjects and the results confirm the variability of the sERP.
Estimation of building-related construction and demolition waste in Shanghai.
Ding, Tao; Xiao, Jianzhuang
2014-11-01
One methodology is proposed to estimate the quantification and composition of building-related construction and demolition (C&D) waste in a fast developing region like Shanghai, PR China. The varieties of structure types and building waste intensities due to the requirement of progressive building design and structure codes in different decades are considered in this regional C&D waste estimation study. It is concluded that approximately 13.71 million tons of C&D waste was generated in 2012 in Shanghai, of which more than 80% of this C&D waste was concrete, bricks and blocks. Analysis from this study can be applied to facilitate C&D waste governors and researchers the duty of formulating precise policies and specifications. As a matter of fact, at least a half of the enormous amount of C&D waste could be recycled if implementing proper recycling technologies and measures. The appropriate managements would be economically and environmentally beneficial to Shanghai where the per capita per year output of C&D waste has been as high as 842 kg in 2010. PMID:25164857
Modeling and Syndromic Surveillance for Estimating Weather-Induced Heat-Related Illness
Perry, Alexander G.; Korenberg, Michael J.; Hall, Geoffrey G.; Moore, Kieran M.
2011-01-01
This paper compares syndromic surveillance and predictive weather-based models for estimating emergency department (ED) visits for Heat-Related Illness (HRI). A retrospective time-series analysis of weather station observations and ICD-coded HRI ED visits to ten hospitals in south eastern Ontario, Canada, was performed from April 2003 to December 2008 using hospital data from the National Ambulatory Care Reporting System (NACRS) database, ED patient chief complaint data collected by a syndromic surveillance system, and weather data from Environment Canada. Poisson regression and Fast Orthogonal Search (FOS), a nonlinear time series modeling technique, were used to construct models for the expected number of HRI ED visits using weather predictor variables (temperature, humidity, and wind speed). Estimates of HRI visits from regression models using both weather variables and visit counts captured by syndromic surveillance as predictors were slightly more highly correlated with NACRS HRI ED visits than either regression models using only weather predictors or syndromic surveillance counts. PMID:21647355
Observation to empirical PGA ratio estimates the relative thickness of sediment
NASA Astrophysics Data System (ADS)
Muzli, M.; Abidin, Z.; Sunarjo
2016-05-01
The amplification of earthquake seismic waves near the surface can vary significantly spatially due to differences in the thickness of sediments above the bedrock. Normally, the determination of sediment thickness is done by comparing the amplitude of the earthquake waveform recorded on the surface with the waveforms recorded on the sensors located on bedrock or borehole. This method, however, is still difficult to use, especially in Indonesia due to the small number of borehole sensors. As an alternative we propose a method to estimate the relative thickness of sediment in a region. It can be done by calculating the PGA ratio between the waveform recorded on the surface with the one calculated using an empirical formula. We then validate these results using the Horizontal to Vertical Spectral Ratio (HVSR) method.
A method for estimating the relative importance of characters in cladistic analyses.
DeGusta, David
2004-08-01
The method of character importance ranking (CIR) is proposed here as a means for estimating the relative "importance" of characters in cladistic analyses, especially those based on morphological features. CIR uses the weighting variable to incrementally remove one character at a time from the analysis, and then evaluates the impact of the removal on the shape of the cladogram. The greater the impact, the more important the character. The CIR method for determining which characters drive the shape of a particular cladogram has several applications. It identifies the characters with the strongest (though not necessarily most accurate) signal in a cladistic analysis; it permits the informed prioritization of characters for further investigation via genetic, developmental, and functional approaches; and it highlights characters whose definition, scoring, independence, and variation should be reviewed with particular care. The application of CIR reveals that at least some cladograms depend entirely on a single character.
Longitudinal and concurrent relations among temperament, ability estimation, and injury proneness.
Schwebel, D C; Plumert, J M
1999-01-01
This study examined longitudinal and concurrent relations between temperament, ability estimation, and injury proneness. Longitudinal assessments of Inhibitory Control were collected through a behavioral battery at toddler (33 months) and preschool ages (46 months). Parent-reported measures of Inhibitory Control and Extraversion also were obtained at those ages. At school age (76 months), children participated in a set of tasks to assess overestimation and underestimation of physical abilities. Parents provided reports of children's temperament and injury history at school age. Results showed that children who were high on Extraversion and low on Inhibitory Control as toddlers and preschoolers tended to overestimate their physical abilities and to have more unintentional injuries at age 6. Children low on Extraversion and high on Inhibitory Control tended to underestimate their physical abilities. Implications for injury prevention are discussed. PMID:10368916
Porosity and permeability evolution of clay faults: in situ experiments
NASA Astrophysics Data System (ADS)
Henry, P.; Guglielmi, Y.; Seguy, S.; Lefevre, M.; Ghani, I.; Gent, G.; Castilla, R.; Gout, C.; Dick, P.; Nussbaum, C.; Durand, J.
2015-12-01
Fault models associating low permeability cores with high permeability damage zones are widely accepted, however, constitutive laws relating permeability with fault structure, stress, and strain remain poorly constrained. We here present preliminary results of hydromechanical experiments performed at the 10 m scale in fault zones in Toarcian and Aalenian black shale formations. Intact formations have a very low permeability (10-19 to 10-22 m2). One case (in IRSN's Tournemire Underground Research Laboratory) displays a porosity increase in and around the fault core and abundant veins and calcite cemented small faults in the damage zone. The other case (Mont Terri Swisstopo Underground Research Laboratory) displays a porosity decrease in the fault core zone and few veins. However, under the present stress state, the static permeability of the fractured zones at both locations is higher than that of the intact formation by up to 3 orders of magnitude. During borehole pressurization tests three regimes of permeability variations are observed. (1) Fracture permeability first increases progressively as a function of fluid pressure (2) When a threshold is reached, permeability further increases by 100 or more, but strain as well as permeability variations remain in most part reversible. (3) When a steady pressure is maintained in the injection borehole (from 20 minutes to several days) flow rate tends to decrease with time. These results show that high transient permeability may locally occur in a fault zone under conditions when most of the deformation is reversible, opening the possibility of transient fluid migration decoupled from slip along faults that are not favorably oriented. However, during one test, more than 1 mm of irreversible slip occurred along one of the main interfaces, associated with a sudden increase in flow rate (from 11 to more than 40 l/min). This suggests that when slip occurs, it could result in permeability variations that may remain difficult
NASA Astrophysics Data System (ADS)
Grimwood, A.; Messa, A.; Bamber, J. C.
2015-03-01
A combined correlation method is introduced to optical coherence elastography for axial displacement estimation. Its performance is compared with that of amplitude correlation tracking and phase shift estimation. Relative sensitivities to small (sub-micron), and large (pixel-scale) axial displacements are analysed for a Perspex test object and gelatine phantom. The combined correlation method exhibited good overall performance, with a larger dynamic range than phase shift estimation and higher sensitivity than amplitude correlation tracking.
Erickson, Marilyn C; Ma, Li M; Doyle, Michael P
2015-11-01
Shelf life of fish packaged under modified atmosphere (MA) is extended, but within the United States, commercial application of MA with impermeable packaging films is restricted due to concerns that botulinum toxin production would precede spoilage when contaminated fish are held at abusive storage temperatures. Use of semipermeable packaging films has been advocated; however, previous studies are inconclusive in determining the oxygen transmission rate (OTR) of a film that is needed to achieve an acceptable margin of safety (i.e., toxin production occurs only after spoilage). This study was conducted to determine the influence of OTR (target OTRs of 3 to 15,000) on the development of spoilage volatiles and toxin in salmon inoculated with type E Clostridium botulinum and subjected to air, vacuum, or 75:25 CO2:N2 MA and storage temperatures of 4, 8, 12, or 16°C. The most dominant headspace volatile peak that was produced during spoilage of samples at 4, 8 or 12°C was a peak, having a Kovats retention index (KI) of 753, and at which external standards of 2- or 3-methyl 1-butanol also eluted. Under anaerobic conditions, both the aerobic microbial populations and the size of the KI 753 spoilage peak were less in inoculated samples compared with uninoculated samples. C. botulinum-inoculated samples that were stored at 12 or 16°C under conditions favorable for anaerobic growth were also characterized by a KI 688 peak. Using a previously developed model that related the percentage of elderly consumers who would prepare a sample having the KI 753 spoilage peak of a specific size, it was determined that for salmon packaged with 3 or 3,000 OTR films under any atmosphere and stored at 12 or 16°C, 2 to 61% of the consumers could potentially prepare toxin-contaminated samples. Hence, when abusive storage conditions are suspected, the fish should not be consumed.
Erickson, Marilyn C; Ma, Li M; Doyle, Michael P
2015-11-01
Shelf life of fish packaged under modified atmosphere (MA) is extended, but within the United States, commercial application of MA with impermeable packaging films is restricted due to concerns that botulinum toxin production would precede spoilage when contaminated fish are held at abusive storage temperatures. Use of semipermeable packaging films has been advocated; however, previous studies are inconclusive in determining the oxygen transmission rate (OTR) of a film that is needed to achieve an acceptable margin of safety (i.e., toxin production occurs only after spoilage). This study was conducted to determine the influence of OTR (target OTRs of 3 to 15,000) on the development of spoilage volatiles and toxin in salmon inoculated with type E Clostridium botulinum and subjected to air, vacuum, or 75:25 CO2:N2 MA and storage temperatures of 4, 8, 12, or 16°C. The most dominant headspace volatile peak that was produced during spoilage of samples at 4, 8 or 12°C was a peak, having a Kovats retention index (KI) of 753, and at which external standards of 2- or 3-methyl 1-butanol also eluted. Under anaerobic conditions, both the aerobic microbial populations and the size of the KI 753 spoilage peak were less in inoculated samples compared with uninoculated samples. C. botulinum-inoculated samples that were stored at 12 or 16°C under conditions favorable for anaerobic growth were also characterized by a KI 688 peak. Using a previously developed model that related the percentage of elderly consumers who would prepare a sample having the KI 753 spoilage peak of a specific size, it was determined that for salmon packaged with 3 or 3,000 OTR films under any atmosphere and stored at 12 or 16°C, 2 to 61% of the consumers could potentially prepare toxin-contaminated samples. Hence, when abusive storage conditions are suspected, the fish should not be consumed. PMID:26555524
Comparative skin permeability of neonatal and adult timber rattlesnakes (Crotalus horridus).
Agugliaro, Joseph; Reinert, Howard K
2005-05-01
Skin permeability and lipid content were determined using shed epidermis of neonatal and adult timber rattlesnakes (Crotalus horridus) from the Coastal Plain Pine Barrens of New Jersey and from the Appalachian Mountains of northern Pennsylvania. Differences between populations due to habitat and within populations due to age were tested. Skin permeability was not found to differ according to locality (P>0.05), but rates were significantly different for age. Permeability of adult epidermis was greater than that of neonates (P<0.01). Lipid content did not differ by locality (P>0.05), but differed between ages, paralleling the results found for permeation rates. Neonate sheds had a greater amount of extractable lipids than adult sheds (P<0.01). Despite the lower skin permeability of neonates, our estimates indicate that the percentage of their total body water content lost per hour may still be 2.2 times that of adults. Resistance to cutaneous water loss may be advantageous to neonates given their relatively large surface area-to-volume ratio. PMID:15893947
Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities
Lee, Myung W.
2008-01-01
Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.
Comparative skin permeability of neonatal and adult timber rattlesnakes (Crotalus horridus).
Agugliaro, Joseph; Reinert, Howard K
2005-05-01
Skin permeability and lipid content were determined using shed epidermis of neonatal and adult timber rattlesnakes (Crotalus horridus) from the Coastal Plain Pine Barrens of New Jersey and from the Appalachian Mountains of northern Pennsylvania. Differences between populations due to habitat and within populations due to age were tested. Skin permeability was not found to differ according to locality (P>0.05), but rates were significantly different for age. Permeability of adult epidermis was greater than that of neonates (P<0.01). Lipid content did not differ by locality (P>0.05), but differed between ages, paralleling the results found for permeation rates. Neonate sheds had a greater amount of extractable lipids than adult sheds (P<0.01). Despite the lower skin permeability of neonates, our estimates indicate that the percentage of their total body water content lost per hour may still be 2.2 times that of adults. Resistance to cutaneous water loss may be advantageous to neonates given their relatively large surface area-to-volume ratio.
Permeability Measurements in Carbon-Epoxy Composites
NASA Technical Reports Server (NTRS)
Zdenek, Michael J.
1999-01-01
To determine the permeability of the composite feedline, that is proposed to be used in the X-33 Reusable Launch Vehicle (RLV), three 8 x 8-in. coupons were constructed. Two of the coupons were layed-up with 4 plies of plain weave prepreg [0/90, plus or minus 45, plus or minus 45, 0/90] and the other one layed-up with 4 plies of unidirectional prepreg [0, 90, 90, 0]. The coupons were vacuumed bagged and cured to manufactures specifications. The coupons were then placed in an apparatus to test for permeability. Nitrogen gas was used to permeate through the coupons at a pressure of 5 psig. A manometer was placed on the opposite side of the coupons and was used to measure the height of the fluid with respect to time. From this data the mass flow rate of the gas could be calculated since the area of the manometer and the density of the gas is known. The results of the test are given. The permeability constant was calculated using Darcy's law, which related the pressure drop, flow rate of the permeating gas and resistance to flow through the coupon created. To put the results into prospective the permeability of sand stone and granite is 1E-15 and 1E-20 respectively.
Human Disc Nucleus Properties and Vertebral Endplate Permeability
Rodriguez, Azucena G.; Slichter, Chloe K.; Acosta, Frank L.; Rodriguez-Soto, Ana E.; Burghardt, Andrew J.; Majumdar, Sharmila; Lotz, Jeffrey C.
2010-01-01
Study of human cadaveric discs quantifying endplate permeability and porosity and correlating these with measures of disc quality: cell density, proteoglycan content, and overall degeneration. Permeability and porosity increased with age and were not correlated with cell density or overall degeneration, suggesting that endplate calcification may not accelerate disc degeneration. Study Design Experimental quantification of relationships between vertebral endplate morphology, permeability, disc cell density, glycosaminoglycan content and degeneration in samples harvested from human cadaveric spines. Objective To test the hypothesis that variation in endplate permeability and porosity contribute to changes in intervertebral disc cell density and overall degeneration. Summary of Background Data Cells within the intervertebral disc are dependent on diffusive exchange with capillaries in the adjacent vertebral bone. Previous findings suggest that blocked routes of transport negatively affect disc quality, yet there are no quantitative relationships between human vertebral endplate permeability, porosity, cell density and disc degeneration. Such relationships would be valuable for clarifying degeneration risk factors, and patient features that may impede efforts at disc tissue engineering. Methods Fifty-one motion segments were harvested from 13 frozen cadaveric human lumbar spines (32 to 85 years) and classified for degeneration using the MRI-based Pfirrmann scale. A cylindrical core was harvested from the center of each motion segment that included vertebral bony and cartilage endplates along with adjacent nucleus tissue. The endplate mobility, a type of permeability, was measured directly using a custom-made permeameter before and after the cartilage endplate was removed. Cell density within the nucleus tissue was estimated using the picogreen method while the nuclear GAG content was quantified using the DMMB technique. Specimens were imaged at 8 μm resolution using
Estimating relative paleolongitudes with the assumption of middle Paleozoic true polar wander
NASA Astrophysics Data System (ADS)
van der Voo, R.; Bazhenov, M.
2003-04-01
Three new paleomagnetic poles have been obtained from Lower Ordovician, Lower Silurian, and Middle Devonian rocks in the Chingiz Range, Kazakhstan (see Bazhenov et al. presentation in session MG3, this meeting). They form an apparent polar wander (APW) loop that resembles similar loops for Ordovician through Devonian poles from Baltica, Laurentia and Gondwana. The latter have previously been attributed to true polar wander (TPW) in an admittedly speculative paper (Van der Voo, 1994, EPSL, vol. 122, pp. 239-243). A characteristic of TPW is that all continents should see its expression manifested in their APW paths, especially if relative plate velocities were much less than TPW rates. Paleopoles from Siberia and the China blocks do not contradict a TPW signature for the Ordovician through Devonian interval, but the results are not complete enough to establish a loop in the APW paths. However, the paleopoles from the Chingiz block in Kazakhstan fit the requisite looping pattern. Even though TPW remains speculative for this interval until it has been shown that all continents have similarly shaped APW paths, there are two interesting issues that are related to TPW. (1) If TPW occurred, similarly shaped APW paths from all continents can be superposed and the Euler rotations necessary for this superposition place the continents in their ancient relative positions to first approximation. This implies that a rough estimate of relative paleolongitudes can be obtained. (2) Superposition of the APW paths should not lead to overlap in continental positions, so that the absence of overlaps constitutes one possible test of the TPW hypothesis. The currently available data from the major continents pass this test.
NASA Technical Reports Server (NTRS)
Slavin, Thomas J.; Cao, Tuan Q.; Kliss, Mark H.
1993-01-01
The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) Liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understaning the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted micrograviity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay. One experiment is conducted for each of the three membrane performance areas under study. These experiments are discussed in this paper.
Unsaturated and Saturated Permeabilities of Fiber Reinforcement: Critics and Suggestions
NASA Astrophysics Data System (ADS)
Park, Chung Hae; Krawczak, Patricia
2015-04-01
In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.
Correlation of Three Techniques for Determining Soil Permeability
ERIC Educational Resources Information Center
Winneberger, John T.
1974-01-01
Discusses problems of acquiring adequate results when measuring for soil permeability. Correlates three relatively simple techniques that could be helpful to the inexperienced technician dealing with septic tank practices. An appendix includes procedures for valid percolation tests. (MLB)
Technology Transfer Automated Retrieval System (TEKTRAN)
Background: Several observational studies have investigated the relation of dietary phylloquinone and menaquinone intake with occurrence of chronic diseases. Most of these studies relied on food frequency questionnaires (FFQ) to estimate the intake of phylloquinone and menaquinones. However, none of...
Relative Scale Estimation and 3D Registration of Multi-Modal Geometry Using Growing Least Squares.
Mellado, Nicolas; Dellepiane, Matteo; Scopigno, Roberto
2016-09-01
The advent of low cost scanning devices and the improvement of multi-view stereo techniques have made the acquisition of 3D geometry ubiquitous. Data gathered from different devices, however, result in large variations in detail, scale, and coverage. Registration of such data is essential before visualizing, comparing and archiving them. However, state-of-the-art methods for geometry registration cannot be directly applied due to intrinsic differences between the models, e.g., sampling, scale, noise. In this paper we present a method for the automatic registration of multi-modal geometric data, i.e., acquired by devices with different properties (e.g., resolution, noise, data scaling). The method uses a descriptor based on Growing Least Squares, and is robust to noise, variation in sampling density, details, and enables scale-invariant matching. It allows not only the measurement of the similarity between the geometry surrounding two points, but also the estimation of their relative scale. As it is computed locally, it can be used to analyze large point clouds composed of millions of points. We implemented our approach in two registration procedures (assisted and automatic) and applied them successfully on a number of synthetic and real cases. We show that using our method, multi-modal models can be automatically registered, regardless of their differences in noise, detail, scale, and unknown relative coverage.
Estimation of Relative Bioavailability of Lead in Soil and Soil-Like Materials Using Young Swine
Casteel, Stan W.; Weis, Christopher P.; Henningsen, Gerry M.; Brattin, William J.
2006-01-01
In this article we summarize the results of a series of studies that measured the relative bioavailability (RBA) of lead in a variety of soil and soil-like test materials. Reference material (Pb acetate) or Pb-contaminated soils were administered orally to juvenile swine twice a day for 15 days. Blood samples were collected from each animal at multiple times during the course of the study, and samples of liver, kidney, and bone were collected at sacrifice. All samples were analyzed for Pb. We estimated the RBA of a test material by fitting mathematical models to the dose–response curves for each measurement end point and finding the ratio of doses that gave equal responses. The final RBA for a test material is the simple average of the four end point–specific RBA values. Results from 19 different test materials reveal a wide range of RBA values across different exposure materials, ranging from 6 to 105%. This variability in RBA between different samples highlights the importance of reliable RBA data to help improve risk assessments for Pb in soil. Although the RBA value for a sample depends on the relative amounts of the different chemical and physical forms of Pb present, data are not yet adequate to allow reliable quantitative predictions of RBA from chemical speciation data alone. PMID:16882520
Parental Estimates of Their Own and Their Relatives' Intelligence. A Spanish Replication
ERIC Educational Resources Information Center
Perez, Luz F.; Gonzalez, Coral; Beltran, Jesus A.
2010-01-01
In this study, Spanish mothers and fathers (N = 108) estimated their own general and multiple intelligences, as well as those of their children and of their own parents. The mothers' self-estimates of their verbal, logical-mathematical, spatial, and corporal intelligence were lower than the fathers'. The mothers made lower estimates of their…
Estimating return periods of extreme values from relatively short time series of winds
NASA Astrophysics Data System (ADS)
Jonasson, Kristjan; Agustsson, Halfdan; Rognvaldsson, Olafur; Arfeuille, Gilles
2013-04-01
An important factor for determining the prospect of individual wind farm sites is the frequency of extreme winds at hub height. Here, extreme winds are defined as the value of the highest 10 minutes averaged wind speed with a 50 year return period, i.e. annual exceeding probability of 2% (Rodrigo, 2010). A frequently applied method to estimate winds in the lowest few hundred meters above ground is to extrapolate observed 10-meter winds logarithmically to higher altitudes. Recent study by Drechsel et al. (2012) showed however that this methodology is not as accurate as interpolating simulated results from the global ECMWF numerical weather prediction (NWP) model to the desired height. Observations of persistent low level jets near Colima in SW-Mexico also show that the logarithmic approach can give highly inaccurate results for some regions (Arfeuille et al., 2012). To address these shortcomings of limited, and/or poorly representative, observations and extrapolations of winds one can use NWP models to dynamically scale down relatively coarse resolution atmospheric analysis. In the case of limited computing resources one has typically to make a compromise between spatial resolution and the duration of the simulated period, both of which can limit the quality of the wind farm siting. A common method to estimate maximum winds is to fit an extreme value distribution (e.g. Gumbel, gev or Pareto) to the maximum values of each year of available data, or the tail of these values. If data are only available for a short period, e.g. 10 or 15 years, then this will give a rather inaccurate estimate. It is possible to deal with this problem by utilizing monthly or weekly maxima, but this introduces new problems: seasonal variation, autocorrelation of neighboring values, and increased discrepancy between data and fitted distribution. We introduce a new method to estimate return periods of extreme values of winds at hub height from relatively short time series of winds, simulated
Waldman, John R.; Fabrizio, Mary C.
1994-01-01
Stock contribution studies of mixed-stock fisheries rely on the application of classification algorithms to samples of unknown origin. Although the performance of these algorithms can be assessed, there are no guidelines regarding decisions about including minor stocks, pooling stocks into regional groups, or sampling discrete substocks to adequately characterize a stock. We examined these questions for striped bass Morone saxatilis of the U.S. Atlantic coast by applying linear discriminant functions to meristic and morphometric data from fish collected from spawning areas. Some of our samples were from the Hudson and Roanoke rivers and four tributaries of the Chesapeake Bay. We also collected fish of mixed-stock origin from the Atlantic Ocean near Montauk, New York. Inclusion of the minor stock from the Roanoke River in the classification algorithm decreased the correct-classification rate, whereas grouping of the Roanoke River and Chesapeake Bay stock into a regional (''southern'') group increased the overall resolution. The increased resolution was offset by our inability to obtain separate contribution estimates of the groups that were pooled. Although multivariate analysis of variance indicated significant differences among Chesapeake Bay substocks, increasing the number of substocks in the discriminant analysis decreased the overall correct-classification rate. Although the inclusion of one, two, three, or four substocks in the classification algorithm did not greatly affect the overall correct-classification rates, the specific combination of substocks significantly affected the relative contribution estimates derived from the mixed-stock sample. Future studies of this kind must balance the costs and benefits of including minor stocks and would profit from examination of the variation in discriminant characters among all Chesapeake Bay substocks.
Morrow, C.A.; Lockner, D.A.
1997-01-01
Permeability, porosity, and volumetric strain measurements were conducted on granite cores obtained at depths of 0.7 to 1.6 km from the Illinois UPH 3 drillhole at effective confining pressures from 5 to 100 MPa. Initial permeabilities were in the range of 10-17 to 10-19 m2 and dropped rapidly with applied pressure to values between 10-20 and 10-24 m2 at 100 MPa, typical of other deep granite core samples. These values are several decades lower than equivalent weathered surface granites at comparable effective confining pressures, where weathering products in cracks and pores inhibit crack closure with applied pressure. Permeabilities of the Illinois cores were inversely related to sample depth, suggesting that stress relief and thermal microfractures induced during core retrieval dominated the fluid flow. Thus these samples provide an upper bound on in situ matrix permeability values. A comparison of core permeability from UPH 3 and other deep drillholes shows that stress relief damage can often dominate laboratory permeability measurements. We conclude that it may be difficult to make meaningful estimates of in situ permeability based on either borehole samples (possible damage during retrieval) or surface-derived analogs (altered by weathering). Volumetric strain determined from porosity measurements was compared with differential strain analysis (DSA) data reported by other investigators on samples from the same depths in the drillhole. Our strain measurements (0.002 to 0.005 at 100 MPa) were nearly twice as large as the DSA values, probably because of the crack-enhancing effects of fluids present in our samples that are absent in the dry DSA cores, as well as other time-dependent deformation effects. This difference in observed strain magnitudes between the two measurement methods may be an important consideration if strain and/or porosity data from deep core samples are used in models of stress, fluid circulation, and excess fluid pressure generation in the
Estimating relative sea-level rise and submergence potential at a coastal wetland
Cahoon, Donald R.
2015-01-01
A tide gauge records a combined signal of the vertical change (positive or negative) in the level of both the sea and the land to which the gauge is affixed; or relative sea-level change, which is typically referred to as relative sea-level rise (RSLR). Complicating this situation, coastal wetlands exhibit dynamic surface elevation change (both positive and negative), as revealed by surface elevation table (SET) measurements, that is not recorded at tide gauges. Because the usefulness of RSLR is in the ability to tie the change in sea level to the local topography, it is important that RSLR be calculated at a wetland that reflects these local dynamic surface elevation changes in order to better estimate wetland submergence potential. A rationale is described for calculating wetland RSLR (RSLRwet) by subtracting the SET wetland elevation change from the tide gauge RSLR. The calculation is possible because the SET and tide gauge independently measure vertical land motion in different portions of the substrate. For 89 wetlands where RSLRwet was evaluated, wetland elevation change differed significantly from zero for 80 % of them, indicating that RSLRwet at these wetlands differed from the local tide gauge RSLR. When compared to tide gauge RSLR, about 39 % of wetlands experienced an elevation rate surplus and 58 % an elevation rate deficit (i.e., sea level becoming lower and higher, respectively, relative to the wetland surface). These proportions were consistent across saltmarsh, mangrove, and freshwater wetland types. Comparison of wetland elevation change and RSLR is confounded by high levels of temporal and spatial variability, and would be improved by co-locating tide gauge and SET stations near each other and obtaining long-term records for both.
Edge type affects leaf-level water relations and estimated transpiration of Eucalyptus arenacea.
Wright, Thomas E; Tausz, Michael; Kasel, Sabine; Volkova, Liubov; Merchant, Andrew; Bennett, Lauren T
2012-03-01
While edge effects on tree water relations are well described for closed forests, they remain under-examined in more open forest types. Similarly, there has been minimal evaluation of the effects of contrasting land uses on the water relations of open forest types in highly fragmented landscapes. We examined edge effects on the water relations and gas exchange of a dominant tree (Eucalyptus arenacea Marginson & Ladiges) in an open forest type (temperate woodland) of south-eastern Australia. Edge effects in replicate woodlands adjoined by cleared agricultural land (pasture edges) were compared with those adjoined by 7- to 9-year-old eucalypt plantation with a 25m fire break (plantation edges). Consistent with studies in closed forest types, edge effects were pronounced at pasture edges where photosynthesis, transpiration and stomatal conductance were greater for edge trees than interior trees (75m into woodlands), and were related to greater light availability and significantly higher branch water potentials at woodland edges than interiors. Nonetheless, gas exchange values were only ∼50% greater for edge than interior trees, compared with ∼200% previously found in closed forest types. In contrast to woodlands adjoined by pasture, gas exchange in winter was significantly lower for edge than interior trees in woodlands adjoined by plantations, consistent with shading and buffering effects of plantations on edge microclimate. Plantation edge effects were less pronounced in summer, although higher water use efficiency of edge than interior woodland trees indicated possible competition for water between plantation trees and woodland edge trees in the drier months (an effect that might have been more pronounced were there no firebreak between the two land uses). Scaling up of leaf-level water relations to stand transpiration using a Jarvis-type phenomenological model indicated similar differences between edge types. That is, transpiration was greater at pasture than
Geothermal Permeability Enhancement - Final Report
Joe Beall; Mark Walters
2009-06-30
The overall objective is to apply known permeability enhancement techniques to reduce the number of wells needed and demonstrate the applicability of the techniques to other undeveloped or under-developed fields. The Enhanced Geothermal System (EGS) concept presented in this project enhances energy extraction from reduced permeability zones in the super-heated, vapor-dominated Aidlin Field of the The Geysers geothermal reservoir. Numerous geothermal reservoirs worldwide, over a wide temperature range, contain zones of low permeability which limit the development potential and the efficient recovery of heat from these reservoirs. Low permeability results from poorly connected fractures or the lack of fractures. The Enhanced Geothermal System concept presented here expands these technologies by applying and evaluating them in a systematic, integrated program.
Cardoso, Luis; Fritton, Susannah P.; Gailani, Gaffar; Benalla, Mohammed; Cowin, Stephen C.
2012-01-01
This contribution reviews recent research performed to assess the porosity and permeability of bone tissue with the objective of understanding interstitial fluid movement. Bone tissue mechanotransduction is considered to occur due to the passage of interstitial pore fluid adjacent to dendritic cell structures in the lacunar-canalicular porosity. The movement of interstitial fluid is also necessary for the nutrition of osteocytes. This review will focus on four topics related to improved assessment of bone interstitial fluid flow. First, the advantages and limitations of imaging technologies to visualize bone porosities and architecture at several length scales are summarized. Second, recent efforts to measure the vascular porosity and lacunar-canalicular microarchitecture are discussed. Third, studies associated with the measurement and estimation of the fluid pressure and permeability in the vascular and lacunar-canalicular domains are summarized. Fourth, the development of recent models to represent the interchange of fluids between the bone porosities is described. PMID:23174418
Gundel, L.; McKone, T.; Daisey, J.
1995-12-31
The purpose of this presentation is to show how advanced measurement technologies for determination of the gas and particulate phase distributions of persistent organic pollutants (POPs) can, with appropriate modeling efforts, lead to better understanding of how atmospheric phase distribution impacts exposure persistence or half-life. New data collected in California with both conventional and diffusion-denuder-based samplers are used to (1) assess the direction and magnitude of sampling biases in existing databases of POPs including organochlorines and polycyclic aromatic hydrocarbons, and (2) compare predictions of persistence and half life using a regional fugacity exposure model (CalTOX). For many POPs, there are data quality problems in measurements of the partitioning between the gas phase and airborne particulate matter, between the gas phase and soils, and between the gas phase and vegetation. Whether intermedia transport takes place in gas or particulate phase can have a strong impact of the estimated persistence of potential human and ecosystem exposure. Most phase distribution measurements use filters followed by adsorbents to determining the relative concentrations of particulate-phase and gas-phase SVOC. In these measurements use filters followed by adsorbents to determining the relative concentrations of particulate-phase and gas-phase SVOC. In these systems, desorption of semi-volatile compounds form the particles on the filters, or adsorption of gases by the filter materials can lead to incorrect measurements of gas- and particulate-phase concentrations. Because the gas phase is collected before the particulate phase, diffusion denuder technology provides a less artifact-encumbered approach for accurate determination of phase distributions of semivolatile species.
Direct estimation of QBO-related gravity wave drag from satellite observations
NASA Astrophysics Data System (ADS)
Ern, Manfred; Ploeger, Felix; Preusse, Peter; Kalisch, Silvio; Riese, Martin
2014-05-01
The quasi-biennial oscillation (QBO) of the zonal wind in the tropical stratosphere is an important process in atmospheric dynamics. Effects of the QBO are found also in the mesosphere and in the extra-tropics. The QBO even has influence on the surface weather and climate, for example during winter in the northern hemisphere at midlatitudes. Still, climate models have large difficulties in reproducing a realistic QBO. The QBO is driven by atmospheric waves. Both global scale waves and mesoscale gravity waves (GWs) contribute. It has been proposed that the driving of the QBO by GWs is more important than that of the global scale waves. The relative importance of GWs is however still highly uncertain, and a direct estimation of the QBO driving by GWs from global observations is still missing. We derive GW temperature variances, GW momentum fluxes and GW drag from three years of High Resolution Dynamics Limb Sounder (HIRDLS) and from 11 years of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. These observations are compared with the drag that is still missing in the tropical momentum budget of the ECMWF ERA Interim (ERAI) reanalysis after considering zonal wind tendency, Coriolis force, advection terms and drag of resolved global-scale waves. The meteorological fields of ERAI are quite realistic because ERAI is strongly constrained by data assimilation. Therefore this missing drag can be attributed to GWs not resolved by the model. We find good qualitative agreement between observed GW drag and the missing drag in ERAI. During eastward QBO wind shear even the magnitude of observed and ERAI missing drag are in good agreement. During westward shear, however, observed drag is much lower than the ERAI missing drag. This asymmetry might hint at uncertainties in the advection terms of ERAI. Further, observed GW spectra indicate that QBO-related GW dissipation is mainly due to critical level filtering.
Relative potency estimates of acceptable residues and reentry intervals after nerve agent release
Watson, A.P.; Jones, T.D.; Adams, J.D. )
1992-06-01
In the event of an unplanned release of a chemical warfare agent during any stage of the Chemical Stockpile Disposal Program, the potential exists for off-post contamination of drinking water, forage crops, grains, garden produce, and livestock. The more persistent agents, such as the organophosphate nerve agent VX, pose the greatest human health concern for reentry. A relative potency approach comparing the toxicity of VX to organophosphate insecticide analogues is developed and used to estimate allowable residues for VX in agricultural products and reentry intervals for public access to contaminated areas. Analysis of mammalian LD50 data by all exposure routes indicates that VX is 10(3) to 10(4) times more toxic than most commercially available organophosphate insecticides. Thus, allowable residues of VX could be considered at concentration levels 10(3) to 10(4) lower than those established for certain insecticides by the U.S. EPA. Evaluation of reentry intervals developed for these organophosphate analogues indicate that, if environmental monitoring cannot reliably demonstrate acceptable levels of VX, restricted access to suspect or contaminated areas may be on the order of weeks to months following agent release. Planning for relocation, mass care centers, and quarantine should take this time period into account.
Kasa, Srinivasulu; Raja Sekhar Reddy, M; Kadaboina, Raja Sekhar; Murki, Veerender; Mulukutla, Venkata Suryanarayana
2014-08-01
A novel, simple, sensitive and stability-indicating high-performance liquid chromatography method was developed and validated for the quantification of impurities (process related and degradants) and the assay determination of Bendamustine hydrochloride. A chromatographic separation of Bendamustine and its impurities was achieved with an Inertsil ODS-2 analytical column, 250 × 4.6 mm, 5 µm, using gradient elution with mobile phase A consisting of a mixture of water and trifluoroacetic acid (1000:1, v/v) and mobile phase B consisting of acetonitrile. The instrumental settings included a flow rate of 1.0 mL/min, column temperature of 27°C and a detector wavelength of 233 nm, using a photodiode array detector. The tailing factor for Bendamustine was 1.10. Bendamustine hydrochloride was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions and the stressed samples were analyzed by the proposed method. Peak homogeneity data of Bendamustine were obtained by using a photodiode array detector in the stressed sample chromatograms, which demonstrated the specificity of the method for estimation in the presence of degradants. The developed method was validated for parameters such as precision, accuracy, linearity, limit of detection, limit of quantification, ruggedness and robustness. The stability tests were also performed on drug substances as per International Conference on Harmonization guidelines. PMID:23825351
Permeability of soils in Mississippi
O'Hara, Charles G.
1994-01-01
The permeability of soils in Mississippi was determined and mapped using a geographic information system (GIS). Soil permeabilities in Mississippi were determined to range in value from nearly 0.0 to values exceeding 5.0 inches per hour. The U.S. Soil Conservation Service's State Soil Geographic Data Base (STATSGO) was used as the primary source of data for the determination of area-weighted soil permeability. STATSGO provides soil layer properties that are spatially referenced to mapped areas. These mapped areas are referred to as polygons in the GIS. The polygons arc boundaries of soils mapped as a group and are given unique Map Unit Identifiers (MUIDs). The data describing the physical characteristics of the soils within each polygon are stored in a tabular data base format and are referred to as attributes. The U.S. Soil Conservation Service developed STATSGO to be primarily used as a guide for regional resource planning, management, and monitoring. STATSGO was designed so that soil information could be extracted from properties tables at the layer level, combined by component, and statistically expanded to cover the entire map unit. The results of this study provide a mapped value for permeability which is representative of the vertical permeability of soils in that area. The resultant permeability map provides a representative vertical soil permeability for a given area sufficient for county, multi- county, and area planning, and will be used as the soil permeability data component in the evaluation of the susceptibility of major aquifers to contami- nation in Mississippi.
Mayorga-Vega, Daniel; Merino-Marban, Rafael; Viciana, Jesús
2014-01-01
The main purpose of the present meta-analysis was to examine the scientific literature on the criterion-related validity of sit-and-reach tests for estimating hamstring and lumbar extensibility. For this purpose relevant studies were searched from seven electronic databases dated up through December 2012. Primary outcomes of criterion-related validity were Pearson´s zero-order correlation coefficients (r) between sit-and-reach tests and hamstrings and/or lumbar extensibility criterion measures. Then, from the included studies, the Hunter- Schmidt´s psychometric meta-analysis approach was conducted to estimate population criterion- related validity of sit-and-reach tests. Firstly, the corrected correlation mean (rp), unaffected by statistical artefacts (i.e., sampling error and measurement error), was calculated separately for each sit-and-reach test. Subsequently, the three potential moderator variables (sex of participants, age of participants, and level of hamstring extensibility) were examined by a partially hierarchical analysis. Of the 34 studies included in the present meta-analysis, 99 correlations values across eight sit-and-reach tests and 51 across seven sit-and-reach tests were retrieved for hamstring and lumbar extensibility, respectively. The overall results showed that all sit-and-reach tests had a moderate mean criterion-related validity for estimating hamstring extensibility (rp = 0.46-0.67), but they had a low mean for estimating lumbar extensibility (rp = 0. 16-0.35). Generally, females, adults and participants with high levels of hamstring extensibility tended to have greater mean values of criterion-related validity for estimating hamstring extensibility. When the use of angular tests is limited such as in a school setting or in large scale studies, scientists and practitioners could use the sit-and-reach tests as a useful alternative for hamstring extensibility estimation, but not for estimating lumbar extensibility. Key Points Overall sit
Murray, Regan; Flockhart, Logan; Pintar, Katarina; Fazil, Aamir; Nesbitt, Andrea; Marshall, Barbara; Tataryn, Joanne; Pollari, Frank
2015-01-01
Abstract Foodborne illness estimates help to set food safety priorities and create public health policies. The Public Health Agency of Canada estimates that 4 million episodes of foodborne illness occur each year in Canada due to 30 known pathogens and unspecified agents. The main objective of this study was to estimate the number of domestically acquired foodborne illness–related hospitalizations and deaths. Using the estimates of foodborne illness for Canada along with data from the Canadian Hospitalization Morbidity Database (for years 2000–2010) and relevant international literature, the number of hospitalizations and deaths for 30 pathogens and unspecified agents were calculated. Analysis accounted for under-reporting and underdiagnosis. Estimates of the proportion foodborne and the proportion travel-related were incorporated for each pathogen. Monte Carlo simulations were performed to account for uncertainty generating mean estimates and 90% probability intervals. It is estimated that each year there are 4000 hospitalizations (range 3200–4800) and 105 (range 75–139) deaths associated with domestically acquired foodborne illness related to 30 known pathogens and 7600 (range 5900–9650) hospitalizations and 133 (range 77–192) deaths associated with unspecified agents, for a total estimate of 11,600 (range 9250–14,150) hospitalizations and 238 (range 155–323) deaths associated with domestically acquired foodborne illness in Canada. Key pathogens associated with these hospitalizations or deaths include norovirus, nontyphoidal Salmonella spp., Campylobacter spp., VTEC O157 and Listeria monocytogenes. This is the first time Canada has established pathogen-specific estimates of domestically acquired foodborne illness–related hospitalizations and deaths. This information illustrates the substantial burden of foodborne illness in Canada. PMID:26259128
Fractal Analysis of Stress Sensitivity of Permeability in Porous Media
NASA Astrophysics Data System (ADS)
Tan, Xiao-Hua; Li, Xiao-Ping; Liu, Jian-Yi; Zhang, Lie-Hui; Cai, Jianchao
2015-12-01
A permeability model for porous media considering the stress sensitivity is derived based on mechanics of materials and the fractal characteristics of solid cluster size distribution. The permeability of porous media considering the stress sensitivity is related to solid cluster fractal dimension, solid cluster fractal tortuosity dimension, solid cluster minimum diameter and solid cluster maximum diameter, Young's modulus, Poisson's ratio, as well as power index. Every parameter has clear physical meaning without the use of empirical constants. The model predictions of permeability show good agreement with those obtained by the available experimental expression. The proposed model may be conducible to a better understanding of the mechanism for flow in elastic porous media.
Insights into reptile dermal contaminant exposure: Reptile skin permeability to pesticides.
Weir, Scott M; Talent, Larry G; Anderson, Todd A; Salice, Christopher J
2016-07-01
There is growing interest in improving ecological risk assessment exposure estimation, specifically by incorporating dermal exposure. At the same time, there is a growing interest in amphibians and reptiles as receptors in ecological risk assessment, despite generally receiving less research than more traditional receptors. Previous research has suggested that dermal exposure may be more important than previously considered for reptiles. We measured reptile skin permeability to four pesticides (thiamethoxam, malathion, tebuthiuron, trifluralin) using ventral skin samples. All four pesticides penetrated the skin but generally had low permeability. There was no apparent relationship between physicochemical properties and permeability coefficients. Malathion had a significantly greater permeability rate at all time points compared to the other pesticides. Tebuthiuron had a greater permeability than thiamethoxam. Reptiles and mammals appear to have similar skin permeability suggesting that dermal exposure estimates for mammals may be representative of reptiles.
Insights into reptile dermal contaminant exposure: Reptile skin permeability to pesticides.
Weir, Scott M; Talent, Larry G; Anderson, Todd A; Salice, Christopher J
2016-07-01
There is growing interest in improving ecological risk assessment exposure estimation, specifically by incorporating dermal exposure. At the same time, there is a growing interest in amphibians and reptiles as receptors in ecological risk assessment, despite generally receiving less research than more traditional receptors. Previous research has suggested that dermal exposure may be more important than previously considered for reptiles. We measured reptile skin permeability to four pesticides (thiamethoxam, malathion, tebuthiuron, trifluralin) using ventral skin samples. All four pesticides penetrated the skin but generally had low permeability. There was no apparent relationship between physicochemical properties and permeability coefficients. Malathion had a significantly greater permeability rate at all time points compared to the other pesticides. Tebuthiuron had a greater permeability than thiamethoxam. Reptiles and mammals appear to have similar skin permeability suggesting that dermal exposure estimates for mammals may be representative of reptiles. PMID:27037770
Calibrated Tully-Fisher relations for improved estimates of disc rotation velocities
NASA Astrophysics Data System (ADS)
Reyes, R.; Mandelbaum, R.; Gunn, J. E.; Pizagno, J.; Lackner, C. N.
2011-11-01
In this paper, we derive scaling relations between photometric observable quantities and disc galaxy rotation velocity Vrot or Tully-Fisher relations (TFRs). Our methodology is dictated by our purpose of obtaining purely photometric, minimal-scatter estimators of Vrot applicable to large galaxy samples from imaging surveys. To achieve this goal, we have constructed a sample of 189 disc galaxies at redshifts z < 0.1 with long-slit Hα spectroscopy from Pizagno et al. and new observations. By construction, this sample is a fair subsample of a large, well-defined parent disc sample of ˜170 000 galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). The optimal photometric estimator of Vrot we find is stellar mass M★ from Bell et al., based on the linear combination of a luminosity and a colour. Assuming a Kroupa initial mass function (IMF), we find: log [V80/(km s-1)] = (2.142 ± 0.004) + (0.278 ± 0.010)[log (M★/M⊙) - 10.10], where V80 is the rotation velocity measured at the radius R80 containing 80 per cent of the i-band galaxy light. This relation has an intrinsic Gaussian scatter ? dex and a measured scatter σmeas= 0.056 dex in log V80. For a fixed IMF, we find that the dynamical-to-stellar mass ratios within R80, (Mdyn/M★)(R80), decrease from approximately 10 to 3, as stellar mass increases from M★≈ 109 to 1011 M⊙. At a fixed stellar mass, (Mdyn/M★)(R80) increases with disc size, so that it correlates more tightly with stellar surface density than with stellar mass or disc size alone. We interpret the observed variation in (Mdyn/M★)(R80) with disc size as a reflection of the fact that disc size dictates the radius at which Mdyn/M★ is measured, and consequently, the fraction of the dark matter 'seen' by the gas at that radius. For the lowest M★ galaxies, we find a positive correlation between TFR residuals and disc sizes, indicating that the total density profile is dominated by dark matter on these scales. For the
Estimation of desert-dust-related ice nuclei profiles from polarization lidar
NASA Astrophysics Data System (ADS)
Mamouri, Rodanthi-Elisavet; Nisantzi, Argyro; Hadjimitsis, Diofantos; Ansmann, Albert
2015-04-01
This paper presents a methodology based on the use of active remote sensing techniques for the estimation of ice nuclei concentrations (INC) for desert dust plumes. Although this method can be applied to other aerosol components, in this study we focus on desert dust. The method makes use of the polarization lidar technique for the separation of dust and non-dust contributions to the particle backscatter and extinction coefficients. The profile of the dust extinction coefficient is converted to APC280 (dust particles with radius larger than 280 nm) and, in a second step, APC280 is converted to INC by means of an APC-INC relationship from the literature. The observed close relationship between dust extinction at 500 nm and APC280 is the key to a successful INC retrieval. The correlation between dust extinction coefficient and APC280 is studied by means of AERONET sun/sky photometer at Morocco, Cape Verde, Barbados, and Cyprus, during situations dominated by desert dust outbreaks. In the present study, polarization lidar observations of the EARLINET (European Aerosol Research Lidar Network) lidar at the Cyprus University of Technology (CUT), Limassol (34.7o N, 33o E), Cyprus were used together with spaceborne lidar observations during CALIPSO satellite overpasses to demonstrate the potential of the new INC retrieval method. A good agreement between the CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization) and our CUT lidar observations regarding the retrieval of dust extinction coefficient, APC280, and INC profiles were found and corroborate the potential of CALIOP to provide 3-D global desert-dust-related INC data sets. In the next step, efforts should be undertaken towards the establishment of a global, height-resolved INC climatology for desert dust plumes. Realistic global INC distributions are required for an improved estimation of aerosol effects on cloud formation and the better quantification of the indirect aerosol effect on climate. Acknowledgements
Timescales for permeability reduction and strength recovery in densifying magma
NASA Astrophysics Data System (ADS)
Heap, M. J.; Farquharson, J. I.; Wadsworth, F. B.; Kolzenburg, S.; Russell, J. K.
2015-11-01
Transitions between effusive and explosive behaviour are routine for many active volcanoes. The permeability of the system, thought to help regulate eruption style, is likely therefore in a state of constant change. Viscous densification of conduit magma during effusive periods, resulting in physical and textural property modifications, may reduce permeability to that preparatory for an explosive eruption. We present here a study designed to estimate timescales of permeability reduction and strength recovery during viscous magma densification by coupling measurements of permeability and strength (using samples from a suite of variably welded, yet compositionally identical, volcanic deposits) with a rheological model for viscous compaction and a micromechanical model, respectively. Bayesian Information Criterion analysis confirms that our porosity-permeability data are best described by two power laws that intersect at a porosity of 0.155 (the "changepoint" porosity). Above and below this changepoint, the permeability-porosity relationship has a power law exponent of 8.8 and 1.0, respectively. Quantitative pore size analysis and micromechanical modelling highlight that the high exponent above the changepoint is due to the closure of wide (∼200-300 μm) inter-granular flow channels during viscous densification and that, below the changepoint, the fluid pathway is restricted to narrow (∼50 μm) channels. The large number of such narrow channels allows porosity loss without considerable permeability reduction, explaining the switch to a lower exponent. Using these data, our modelling predicts a permeability reduction of four orders of magnitude (for volcanically relevant temperatures and depths) and a strength increase of a factor of six on the order of days to weeks. This discrepancy suggests that, while the viscous densification of conduit magma will inhibit outgassing efficiency over time, the regions of the conduit prone to fracturing, such as the margins, will
We describe a framework for estimating the human dose at which a chemical significantly alters a biological pathway in vivo, making use of in vitro assay data and an in vitro derived pharmacokinetic model, coupled with estimates of population variability and uncertainty. The q...
ERIC Educational Resources Information Center
Phillips, Daniel W.; Montello, Daniel R.
2015-01-01
Previous research has examined heuristics--simplified decision-making rules-of-thumb--for geospatial reasoning. This study examined at two locations the influence of beliefs about local coastline orientation on estimated directions to local and distant places; estimates were made immediately or after fifteen seconds. This study goes beyond…
ERIC Educational Resources Information Center
Schochet, Peter; Burghardt, John
2007-01-01
This article discusses the use of propensity scoring in experimental program evaluations to estimate impacts for subgroups defined by program features and participants' program experiences. The authors discuss estimation issues and provide specification tests. They also discuss the use of an overlooked data collection design--obtaining predictions…
Varma, Manthena V S; Panchagnula, Ramesh
2005-01-01
Solubility and permeability being important determinants of oral drug absorption, this study was aimed to investigate the effect of D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) on the solubility and intestinal permeability of paclitaxel in vitro, in situ and in vivo, in order to estimate the absorption enhancement ability of TPGS. Aqueous solubility of paclitaxel is significantly enhanced by TPGS, where a linear increase was demonstrated above a TPGS concentration of 0.1 mg/ml. Paclitaxel demonstrated asymmetric transport across rat ileum with significantly greater (26-fold) basolateral-to-apical (B-A) permeability than that in apical-to-basolateral (A-B) direction. Presence of P-glycoprotein (P-gp) inhibitor, verapamil (200 microM), diminished asymmetric transport of paclitaxel suggesting the role of P-gp-mediated efflux. TPGS showed a concentration-dependent increase in A-B permeability and decreased B-A permeability. The maximum efflux inhibition activity was found at a minimum TPGS concentration of 0.1 mg/ml, however, further increase in TPGS concentration resulted in decreased A-B permeability with no change in B-A permeability. Thus, the maximum paclitaxel permeability attained with 0.1 mg/ml TPGS was attributed to the interplay between TPGS concentration dependent P-gp inhibition activity and miceller formation. In situ permeability studies in rats also demonstrated the role of efflux in limiting permeability of paclitaxel and inhibitory efficiency of TPGS. The plasma concentration of [14C]paclitaxel following oral administration (25 mg/kg) was significantly increased by coadministration of TPGS at a dose of 50 mg/kg in rats. Bioavailability is enhanced about 4.2- and 6.3-fold when [14C]paclitaxel was administrated with verapamil (25 mg/kg) and TPGS, respectively, as compared to [14C]paclitaxel administered alone. The effect of verapamil on oral bioavailability of [14C]paclitaxel was limited relative to the TPGS, consistent with the in vitro
Graff, John J; Sathiakumar, Nalini; Macaluso, Maurizio; Maldonado, George; Matthews, Robert; Delzell, Elizabeth
2009-09-01
In a follow-up study of mortality among North American synthetic rubber industry workers, cumulative exposure to 1,3-butadiene was positively associated with leukemia. Problems with historical exposure estimation, however, may have distorted the association. To evaluate the impact of potential inaccuracies in exposure estimation, we conducted uncertainty analyses of the relation between cumulative exposure to butadiene and leukemia. We created the 1,000 sets of butadiene estimates using job-exposure matrices consisting of exposure values that corresponded to randomly selected percentiles of the approximate probability distribution of plant-, work area/job group-, and year specific butadiene ppm. We then analyzed the relation between cumulative exposure to butadiene and leukemia for each of the 1,000 sets of butadiene estimates. In the uncertainty analysis, the point estimate of the RR for the first non zero exposure category (>0-<37.5 ppm-years) was most likely to be about 1.5. The rate ratio for the second exposure category (37.5-<184.7 ppm-years) was most likely to range from 1.5 to 1.8. The RR for category 3 of exposure (184.7-<425.0 ppm-years) was most likely between 2.1 and 3.0. The RR for the highest exposure category (425.0+ ppm-years) was likely to be between 2.9 and 3.7. This range off RR point estimates can best be interpreted as a probability distribution that describes our uncertainty in RR point estimates due to uncertainty in exposure estimation. After considering the complete probability distributions of butadiene exposure estimates, the exposure-response association of butadiene and leukemia was maintained. This exercise was a unique example of how uncertainty analyses can be used to investigate and support an observed measure of effect when occupational exposure estimates are employed in the absence of direct exposure measurements.
Graff, John J.; Sathiakumar, Nalini; Macaluso, Maurizio; Maldonado, George; Matthews, Robert; Delzell, Elizabeth
2009-01-01
In a follow-up study of mortality among North American synthetic rubber industry workers, cumulative exposure to 1,3-butadiene was positively associated with leukemia. Problems with historical exposure estimation, however, may have distorted the association. To evaluate the impact of potential inaccuracies in exposure estimation, we conducted uncertainty analyses of the relation between cumulative exposure to butadiene and leukemia. We created the 1,000 sets of butadiene estimates using job-exposure matrices consisting of exposure values that corresponded to randomly selected percentiles of the approximate probability distribution of plant-, work area/job group-, and year specific butadiene ppm. We then analyzed the relation between cumulative exposure to butadiene and leukemia for each of the 1,000 sets of butadiene estimates. In the uncertainty analysis, the point estimate of the RR for the first non zero exposure category (>0–<37.5 ppm-years) was most likely to be about 1.5. The rate ratio for the second exposure category (37.5–<184.7 ppm-years) was most likely to range from 1.5 to 1.8. The RR for category 3 of exposure (184.7–<425.0 ppm-years) was most likely between 2.1 and 3.0. The RR for the highest exposure category (425.0+ ppm-years) was likely to be between 2.9 and 3.7. This range off RR point estimates can best be interpreted as a probability distribution that describes our uncertainty in RR point estimates due to uncertainty in exposure estimation. After considering the complete probability distributions of butadiene exposure estimates, the exposure-response association of butadiene and leukemia was maintained. This exercise was a unique example of how uncertainty analyses can be used to investigate and support an observed measure of effect when occupational exposure estimates are employed in the absence of direct exposure measurements. PMID:19826555
Johnston, Michael F; Hays, Ron D; Hui, Ka-Kit
2009-01-01
Background Estimating a realistic effect size is an important issue in the planning of clinical studies of complementary and alternative medicine therapies. When a minimally important difference is not available, researchers may estimate effect size using the published literature. This evidence-based effect size estimation may be used to produce a range of empirically-informed effect size and consequent sample size estimates. We provide an illustration of deriving plausible effect size ranges for a study of acupuncture in the relief of post-chemotherapy fatigue in breast cancer patients. Methods A PubMed search identified three uncontrolled studies reporting the effect of acupuncture in relieving fatigue. A separate search identified five randomized controlled trials (RCTs) with a wait-list control of breast cancer patients receiving standard care that reported data on fatigue. We use these published data to produce best, average, and worst-case effect size estimates and related sample size estimates for a trial of acupuncture in the relief of cancer-related fatigue relative to a wait-list control receiving standard care. Results Use of evidence-based effect size estimation to calculate sample size requirements for a study of acupuncture in relieving fatigue in breast cancer survivors relative to a wait-list control receiving standard care suggests that an adequately-powered phase III randomized controlled trial comprised of two arms would require at least 101 subjects (52 per arm) if a strong effect is assumed for acupuncture and 235 (118 per arm) if a moderate effect is assumed. Conclusion Evidence-based effect size estimation helps justify assumptions in light of empirical evidence and can lead to more realistic sample size calculations, an outcome that would be of great benefit for the field of complementary and alternative medicine. PMID:19144128
Permeability of WIPP Salt During Damage Evolution and Healing
BODNER,SOL R.; CHAN,KWAI S.; MUNSON,DARRELL E.
1999-12-03
The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering.
Number of trials required to estimate a free-energy difference, using fluctuation relations.
Yunger Halpern, Nicole; Jarzynski, Christopher
2016-05-01
The difference ΔF between free energies has applications in biology, chemistry, and pharmacology. The value of ΔF can be estimated from experiments or simulations, via fluctuation theorems developed in statistical mechanics. Calculating the error in a ΔF estimate is difficult. Worse, atypical trials dominate estimates. How many trials one should perform was estimated roughly by Jarzynski [Phys. Rev. E 73, 046105 (2006)PLEEE81539-375510.1103/PhysRevE.73.046105]. We enhance the approximation with the following information-theoretic strategies. We quantify "dominance" with a tolerance parameter chosen by the experimenter or simulator. We bound the number of trials one should expect to perform, using the order-∞ Rényi entropy. The bound can be estimated if one implements the "good practice" of bidirectionality, known to improve estimates of ΔF. Estimating ΔF from this number of trials leads to an error that we bound approximately. Numerical experiments on a weakly interacting dilute classical gas support our analytical calculations.
Number of trials required to estimate a free-energy difference, using fluctuation relations.
Yunger Halpern, Nicole; Jarzynski, Christopher
2016-05-01
The difference ΔF between free energies has applications in biology, chemistry, and pharmacology. The value of ΔF can be estimated from experiments or simulations, via fluctuation theorems developed in statistical mechanics. Calculating the error in a ΔF estimate is difficult. Worse, atypical trials dominate estimates. How many trials one should perform was estimated roughly by Jarzynski [Phys. Rev. E 73, 046105 (2006)PLEEE81539-375510.1103/PhysRevE.73.046105]. We enhance the approximation with the following information-theoretic strategies. We quantify "dominance" with a tolerance parameter chosen by the experimenter or simulator. We bound the number of trials one should expect to perform, using the order-∞ Rényi entropy. The bound can be estimated if one implements the "good practice" of bidirectionality, known to improve estimates of ΔF. Estimating ΔF from this number of trials leads to an error that we bound approximately. Numerical experiments on a weakly interacting dilute classical gas support our analytical calculations. PMID:27300866
Number of trials required to estimate a free-energy difference, using fluctuation relations
NASA Astrophysics Data System (ADS)
Yunger Halpern, Nicole; Jarzynski, Christopher
2016-05-01
The difference Δ F between free energies has applications in biology, chemistry, and pharmacology. The value of Δ F can be estimated from experiments or simulations, via fluctuation theorems developed in statistical mechanics. Calculating the error in a Δ F estimate is difficult. Worse, atypical trials dominate estimates. How many trials one should perform was estimated roughly by Jarzynski [Phys. Rev. E 73, 046105 (2006), 10.1103/PhysRevE.73.046105]. We enhance the approximation with the following information-theoretic strategies. We quantify "dominance" with a tolerance parameter chosen by the experimenter or simulator. We bound the number of trials one should expect to perform, using the order-∞ Rényi entropy. The bound can be estimated if one implements the "good practice" of bidirectionality, known to improve estimates of Δ F . Estimating Δ F from this number of trials leads to an error that we bound approximately. Numerical experiments on a weakly interacting dilute classical gas support our analytical calculations.
Slade, Jeffrey W.; Adams, Jean V.; Cuddy, Douglas W.; Neave, Fraser B.; Sullivan, W. Paul; Young, Robert J.; Fodale, Michael F.; Jones, Michael L.
2003-01-01
We developed two weight-length models from 231 populations of larval sea lampreys (Petromyzon marinus) collected from tributaries of the Great Lakes: Lake Ontario (21), Lake Erie (6), Lake Huron (67), Lake Michigan (76), and Lake Superior (61). Both models were mixed models, which used population as a random effect and additional environmental factors as fixed effects. We resampled weights and lengths 1,000 times from data collected in each of 14 other populations not used to develop the models, obtaining a weight and length distribution from reach resampling. To test model performance, we applied the two weight-length models to the resampled length distributions and calculated the predicted mean weights. We also calculated the observed mean weight for each resampling and for each of the original 14 data sets. When the average of predicted means was compared to means from the original data in each stream, inclusion of environmental factors did not consistently improve the performance of the weight-length model. We estimated the variance associated with measures of abundance and mean weight for each of the 14 selected populations and determined that a conservative estimate of the proportional contribution to variance associated with estimating abundance accounted for 32% to 95% of the variance (mean = 66%). Variability in the biomass estimate appears more affected by variability in estimating abundance than in converting length to weight. Hence, efforts to improve the precision of biomass estimates would be aided most by reducing the variability associated with estimating abundance.
Plio-Pleistocene stratigraphy and relative sea level estimates: an emerging global perspective
NASA Astrophysics Data System (ADS)
Hearty, Paul; O'Leary, Michael; Rovere, Alessio; Raymo, Maureen; Sandstrom, Michael
2015-04-01
The historical rise of atmospheric CO2 to over 400 ppmv amplifies the need to better understand natural systems during past warmer interglacials. This change over the past 150 years approximates the CO2 range of full glacial-interglacial cycles. Resulting future global impacts are likely, and accurate geological field data would help us better understand the past behavior of sea level (SL) and ice sheets. The middle Pliocene warm period (MPWP) offers an approximate analogue for a 400-ppmv world. Before PLIOMAX (www.pliomax.org), only a handful of estimates of relative sea levels (RSL) along with considerable uncertainties were available for the MPWP. Precise elevations of Plio-Pleistocene RSL indicators were measured with decimeter accuracy using an OmniStar dGPS at sites in Australia, South Africa, Argentina, and other seemingly stable locations. High-resolution SL indicators include wave abrasion surfaces, sub- and intertidal sedimentary structures, and in situ marine invertebrates such as shallow water oysters and barnacles. In addition, thousands of km of terraced coastline was surveyed with dGPS between study sites. The coastal geomorphic expression of Pliocene SL is profound. From ~5 to 3 Ma, high frequency orbitally-paced, low amplitude SL oscillations acted as a shoreline "buzz saw" on hard bedrock, forming extensive high terraces. In high sediment environments such as that of the southeast US Atlantic Coastal Plain, relatively stable Pliocene ocean levels trapped huge volumes of fluvial sediments in the coastal zone, resulting in broad sandy terraces and extensive dune fields. However, glacio-isostatic adjustment (GIA), dynamic topography (DT), and other post-depositional processes have warped these marine terraces by tens of meters since the Pliocene (Raymo et al. 2011, Rovere et al 2014). The PLIOMAX team has documented precise RSLs from numerous global sites that clearly indicate that global ice volume was significantly reduced during intervals of the
Diffusion of DNAPL Components into Low Permeability Soils
NASA Astrophysics Data System (ADS)
Ayral, D.; Demond, A. H.
2013-12-01
Hazardous waste sites contaminated with dense non-aqueous phase liquids (DNAPLs) have proven difficult to remediate. Even though DNAPLs may be removed from high permeability subsurface strata, the storage of compounds making up DNAPLs in low permeability strata constitutes a secondary source that contributes to a dissolved phase plume over an extended period of time. The movement of DNAPL constituents into and out of low permeable strata is considered to occur through diffusion. However, there are few experimentally measured effective diffusion coefficients for DNAPL components in low permeability soils. Thus, the effective diffusion coefficient is commonly estimated from the aqueous phase diffusion coefficient as a function of the porosity of the soil. This study presents measurements of effective diffusion coefficients of chlorinated solvents and an anionic surfactant dioctyl sodium sulfosuccinate (AOT) in silt and clay-silt mixtures. The experimental results are compared with estimated values to evaluate the performance of commonly used methods to estimate effective diffusion coefficients of DNAPL components. These estimation models generally suggest an increase in the effective diffusion coefficient with an increase in porosity. Yet, in low permeable soils with a substantial fraction of clay, the effective diffusion coefficient for chlorinated solutes decreases, although the porosity increases. Thus, calculations of the quantity of mass stored in low permeable strata may be in error if based on rates of diffusion calculated using such models. In addition to chlorinated solvents, DNAPLs often contain surfactants. The high molecular weight of these solutes results in problems when estimating their effective diffusion coefficient in low permeability soils, since commonly models were formulated for use with low molecular weight compounds. Furthermore, some clay minerals present in low permeable soils have a flexible structure which enables them to expand or
Permeability Asymmetry in Composite Porous Ceramic Membranes
NASA Astrophysics Data System (ADS)
Kurcharov, I. M.; Laguntsov, N. I.; Uvarov, V. I.; Kurchatova, O. V.
The results from the investigation of transport characteristics and gas transport asymmetry in bilayer composite membranes are submitted. These membranes are produced by SHS method. Asymmetric effect and hysteresis of permeability in nanoporous membranes are detected. It's shown, that permeability ratio (asymmetry value of permeability) increases up to several times. The asymmetry of permeability usually decreases monotonically with the pressure decrease.
Petrophysics of low-permeability medina sandstone, northwestern Pennsylvania, Appalachian Basin
Castle, J.W.; Byrnes, A.P.
1998-01-01
Petrophysical core testing combined with geophysical log analysis of low-permeability, Lower Silurian sandstones of the Appalachian basin provides guidelines and equations for predicting gas producibility. Permeability values are predictable from the borehole logs by applying empirically derived equations based on correlation between in-situ porosity and in-situ effective gas permeability. An Archie-form equation provides reasonable accuracy of log-derived water saturations because of saturated brine salinities and low clay content in the sands. Although measured porosity and permeability average less than 6% and 0.1 mD, infrequent values as high as 18% and 1,048 mD occur. Values of effective gas permeability at irreducible water saturation (Swi) range from 60% to 99% of routine values for the highest permeability rocks to several orders of magnitude less for the lowest permeability rocks. Sandstones having porosity greater than 6% and effective gas permeability greater than 0.01 mD exhibit Swi less than 20%. With decreasing porosity, Swi sharply increases to values near 40% at 3 porosity%. Analysis of cumulative storage and flow capacity indicates zones with porosity greater than 6% generally contain over 90% of flow capacity and hold a major portion of storage capacity. For rocks with Swi < 20%, gas relative permeabilities exceed 45%. Gas relative permeability and hydrocarbon volume decrease rapidly with increasing Swi as porosity drops below 6%. At Swi above 40%, gas relative permeabilities are less than approximately 10%.
Ferrario, Carrie R; Loweth, Jessica A; Milovanovic, Mike; Ford, Kerstin A; Galiñanes, Gregorio L; Heng, Li-Jun; Tseng, Kuei Y; Wolf, Marina E
2011-12-01
Cue-induced cocaine seeking intensifies or incubates after withdrawal from extended access cocaine self-administration, a phenomenon termed incubation of cocaine craving. The expression of incubated craving is mediated by Ca²⁺-permeable AMPA receptors (CP-AMPARs) in the nucleus accumbens (NAc). Thus, CP-AMPARs are a potential target for therapeutic intervention, making it important to understand mechanisms that govern their accumulation. Here we used subcellular fractionation and biotinylation of NAc tissue to examine the abundance and distribution of AMPAR subunits, and GluA1 phosphorylation, in the incubation model. We also studied two transmembrane AMPA receptor regulatory proteins (TARPs), γ-2 and γ-4. Our results, together with earlier findings, suggest that some of the new CP-AMPARs are synaptic. These are probably associated with γ-2, but they are loosely tethered to the PSD. Levels of GluA1 phosphorylated at serine 845 (pS845 GluA1) were significantly increased in biotinylated tissue and in an extrasynaptic membrane-enriched fraction. These results suggest that increased synaptic levels of CP-AMPARs may result in part from an increase in pS845 GluA1 in extrasynaptic membranes, given that S845 phosphorylation primes GluA1-containing AMPARs for synaptic insertion and extrasynaptic AMPARs supply the synapse. Some of the new extrasynaptic CP-AMPARs are likely associated with γ-4, rather than γ-2. The maintenance of CP-AMPARs in NAc synapses during withdrawal is accompanied by activation of CaMKII and ERK2 but not CaMKI. Overall, AMPAR plasticity in the incubation model shares some features with better described forms of synaptic plasticity, although the timing of the phenomenon and the persistence of related neuroadaptations are significantly different. PMID:21276808
Gaohua, Lu; Neuhoff, Sibylle; Johnson, Trevor N; Rostami-Hodjegan, Amin; Jamei, Masoud
2016-06-01
A 4-compartment permeability-limited brain (4Brain) model consisting of brain blood, brain mass, cranial and spinal cerebrospinal fluid (CSF) compartments has been developed and incorporated into a whole body physiologically-based pharmacokinetic (PBPK) model within the Simcyp Simulator. The model assumptions, structure, governing equations and system parameters are described. The model in particular considers the anatomy and physiology of the brain and CSF, including CSF secretion, circulation and absorption, as well as the function of various efflux and uptake transporters existing on the blood-brain barrier (BBB) and blood-CSF barrier (BCSFB), together with the known parameter variability. The model performance was verified using in vitro data and clinical observations for paracetamol and phenytoin. The simulated paracetamol spinal CSF concentration is comparable with clinical lumbar CSF data for both intravenous and oral doses. Phenytoin CSF concentration-time profiles in epileptic patients were simulated after accounting for disease-induced over-expression of efflux transporters within the BBB. Various 'what-if' scenarios, involving variation of specific drug and system parameters of the model, demonstrated that the 4Brain model is able to simulate the possible impact of transporter-mediated drug-drug interactions, the lumbar puncture process and the age-dependent change in the CSF turnover rate on the local PK within the brain. PMID:27236639
Permeability of stylolite-bearing chalk
Lind, I.; Nykjaer, O.; Priisholm, S. ); Springer, N.
1994-11-01
Permeabilities were measured on core plugs from stylolite-bearing chalk of the Gorm field in the Danish North Sea. Air and liquid permeabilities were measured in directions parallel to and perpendicular to the stylolite surface. Permeability was measured with sleeve pressure equal to in-situ reservoir stress. Permeabilities of plugs with stylolites but without stylolite-associated fractures were equal in the two directions. The permeability is equal to the matrix permeability of non-stylolite-bearing chalk. In contrast, when fractures were associated with the stylolites, permeability was enhanced. The enhancement was most significant in the horizontal direction parallel to the stylolites.
Mayorga-Vega, Daniel; Aguilar-Soto, Pablo; Viciana, Jesús
2015-01-01
The main purpose of the present meta-analysis was to examine the criterion-related validity of the 20-m shuttle run test for estimating cardiorespiratory fitness. Relevant studies were searched from twelve electronic databases up to December 2014, as well as from several alternative modes of searching. The Hunter-Schmidt’s psychometric meta-analysis approach was conducted to estimate the population criterion-related validity of the 20-m shuttle run test. From 57 studies that were included in the present meta-analysis, a total of 78 correlation values were analyzed. The overall results showed that the performance score of the 20-m shuttle run test had a moderate-to-high criterion-related validity for estimating maximum oxygen uptake (rp = 0.66-0.84), being higher when other variables (e.g. sex, age or body mass) were used (rp = 0.78-0.95). The present meta-analysis also showed that the criterion-related validity of Léger’s protocol was statistically higher for adults (rp = 0.94, 0.87-1.00) than for children (rp = 0.78, 0.72-0.85). However, sex and maximum oxygen uptake level do not seem to affect the criterion-related validity values. When an individual’s maximum oxygen uptake attained during a laboratory-based test is not feasible, the 20-m shuttle run test seems to be a useful alternative for estimating cardiorespiratory fitness. In adults the performance score only seems to be a strong estimator of cardiorespiratory fitness, in contrast among children the performance score should be combined with other variables. Nevertheless, as in the application of any physical fitness field test, evaluators must be aware that the performance score of the 20-m shuttle run test is simply an estimation and not a direct measure of cardiorespiratory fitness. Key points Overall the 20-m shuttle run test has a moderate-to-high mean criterion-related validity for estimating cardiorespiratory fitness. The criterion-related validity of the 20-m shuttle run test is significantly
Paranodal permeability in `myelin mutants'
Shroff, S.; Mierzwa, A.; Scherer, S.S.; Peles, E.; Arevalo, J.C.; Chao, M.V.; Rosenbluth, J.
2011-01-01
Fluorescent dextran tracers of varying sizes have been used to assess paranodal permeability in myelinated sciatic nerve fibers from control and three `myelin mutant' mice, Caspr-null, cst-null and shaking. We demonstrate that in all of these the paranode is permeable to small tracers (3kDa, 10kDa), which penetrate most fibers, and to larger tracers (40kDa, 70kDa), which penetrate far fewer fibers and move shorter distances over longer periods of time. Despite gross diminution in transverse bands in the Caspr-null and cst-null mice, the permeability of their paranodal junctions is equivalent to that in controls. Thus, deficiency of transverse bands in these mutants does not increase the permeability of their paranodal junctions to the dextrans we used, moving from the perinodal space through the paranode to the internodal periaxonal space. In addition, we show that the shaking mice, which have thinner myelin and shorter paranodes, show increased permeability to the same tracers despite the presence of transverse bands. We conclude that the extent of penetration of these tracers does not depend on the presence or absence of transverse bands but does depend on the length of the paranode and, in turn, on the length of `pathway 3', the helical extracellular pathway that passes through the paranode parallel to the lateral edge of the myelin sheath. PMID:21618613
Paranodal permeability in "myelin mutants".
Shroff, Seema; Mierzwa, Amanda; Scherer, Steven S; Peles, Elior; Arevalo, Juan C; Chao, Moses V; Rosenbluth, Jack
2011-10-01
Fluorescent dextran tracers of varying sizes have been used to assess paranodal permeability in myelinated sciatic nerve fibers from control and three "myelin mutant" mice, Caspr-null, cst-null, and shaking. We demonstrate that in all of these the paranode is permeable to small tracers (3 kDa and 10 kDa), which penetrate most fibers, and to larger tracers (40 kDa and 70 kDa), which penetrate far fewer fibers and move shorter distances over longer periods of time. Despite gross diminution in transverse bands (TBs) in the Caspr-null and cst-null mice, the permeability of their paranodal junctions is equivalent to that in controls. Thus, deficiency of TBs in these mutants does not increase the permeability of their paranodal junctions to the dextrans we used, moving from the perinodal space through the paranode to the internodal periaxonal space. In addition, we show that the shaking mice, which have thinner myelin and shorter paranodes, show increased permeability to the same tracers despite the presence of TBs. We conclude that the extent of penetration of these tracers does not depend on the presence or absence of TBs but does depend on the length of the paranode and, in turn, on the length of "pathway 3," the helical extracellular pathway that passes through the paranode parallel to the lateral edge of the myelin sheath. PMID:21618613
Use of permeability surface area-product to differentiate intracranial tumours from abscess
Ramli, N; Rahmat, K; Mah, E; Waran, V; Tan, LK; Chong, HT
2009-01-01
Background and Purpose Clinical and radiological findings of intracranial abscesses may mimic the findings of brain tumours and vice versa. However, the discrimination is of great clinical importance in planning treatment and in following prognosis and response to therapy. This study evaluates the Computed Tomography (CT) perfusion parameters, especially the permeability index, with the aim of evaluating the usefulness of dynamic CT perfusion imaging as an alternative tool to differentiate necrotic brain tumours and intracerebral abscesses. Materials and Methods A total of 21 patients underwent perfusion CT study and were divided into 2 groups: Group 1, patients with necrotic brain tumours (n=13); and Group 2, patients with cerebral abscesses (n=8). The mean perfusion parameters were obtained from the enhancing part of the lesion. The relative ratios were then calculated by using the results from mirrored regions within the contralateral hemisphere as reference. Results The results of this study showed that there was significant difference in the relative permeability surface values between necrotic brain tumours and cerebral abscesses (p=0.005). By applying the ROC curve, a value of 25.1 for rPS was found to be the best estimate to distinguish necrotic brain tumours from cerebral abscesses with a specificity of 88 % and sensitivity of 70 %. Conclusion CT perfusion, especially permeability surface, may allow for better differentiation of cerebral abscesses from brain tumours, making it a strong additional imaging modality in the early diagnosis of these two entities. PMID:21611026
Han, S.R.
1988-01-01
The primary aim of this study was to develop non-invasive, physical means to quantitatively assess the epidermal turnover kinetics and barrier properties of the skin and relate these to the cutaneous irritation which results from ultraviolet light irradiation and mold thermal burns. After systematically injecting radiolabeled glycine, the appearance of radioactivity at the skin's surface indicated the transit time of radiolabeled cells through the skin. By plotting the data as the cumulative specific activity against time and then fitting them with a third order polynomial equation, it is possible to estimate the turnover time of the stratum corneum. The skin turnover was coordinated with non-invasive transepidermal water loss (TEWL) studies determined with an evaporimeter. In vitro diffusion studies of the permeability of hydrocortisone through UVB irradiated and thermally burned skin were also performed. The studies indicated that irritated skin offers a relatively low diffusional resistance to hydrocortisone. Depending on the severity of the trauma, the increases in hydrocortisone's permeability coefficient through irritated skin ranged from a low of about 2 times normal to a high of about 210 times normal. Trauma-induced changes in hydrocortisone permeability parallel changes in TEWL, proving that the barrier deficient state resulting from rapid epidermal turnover is a general phenomenon.
Anisotropic Hydraulic Permeability Under Finite Deformation
Ateshian, Gerard A.; Weiss, Jeffrey A.
2011-01-01
The structural organization of biological tissues and cells often produces anisotropic transport properties. These tissues may also undergo large deformations under normal function, potentially inducing further anisotropy. A general framework for formulating constitutive relations for anisotropic transport properties under finite deformation is lacking in the literature. This study presents an approach based on representation theorems for symmetric tensor-valued functions and provides conditions to enforce positive semi-definiteness of the permeability or diffusivity tensor. Formulations are presented which describe materials that are orthotropic, transversely isotropic, or isotropic in the reference state, and where large strains induce greater anisotropy. Strain-induced anisotropy of the permeability of a solid-fluid mixture is illustrated for finite torsion of a cylinder subjected to axial permeation. It is shown that, in general, torsion can produce a helical flow pattern, rather than the rectilinear pattern observed when adopting a more specialized, unconditionally isotropic spatial permeability tensor commonly used in biomechanics. The general formulation presented in this study can produce both affine and non-affine reorientation of the preferred directions of material symmetry with strain, depending on the choice of material functions. This study addresses a need in the biomechanics literature by providing guidelines and formulations for anisotropic strain-dependent transport properties in porous-deformable media undergoing large deformations. PMID:21034145
Dodd, Katelynn E.; Mazurek, Jacek M.
2016-01-01
Objective Asthma Call-back Survey methodology has been changed recently, as a new sampling design, weights calculation (2011–2012), and revised work-related asthma (WRA) section (2012) were implemented. To assess the effect of these changes on the WRA and possible WRA estimates among ever-employed adults with current asthma, we analyzed 2007– 2012 data for 37 505 ever-employed adults (≥18 years) collected from 19 US states (representing an estimated 10 million adults each year). Methods Using data from landline telephone (LLP) households, we calculated estimates applying poststratification weights (2007– 2010) and “raking” weights (2011–2012). Also, using data from LLP/cellular telephone (CP) households combined, we calculated estimates applying “raking” weights (2012). Results Based on LLP household data, the WRA estimates ranged from 7.8% to 9.7% during 2007–2010, was 9.1% in 2011 and 15.4% in 2012. Possible WRA estimates ranged from 35.1% to 38.1% during 2007–2010, was 38.1% in 2011 and 39.8% in 2012. Using the 2012 LLP/CP household data, the WRA and possible WRA estimates were 15.4% and 38.9%, respectively. Conclusions Implementation of “raking” weights did not substantially change the WRA or possible WRA estimates among ever-employed adults with current asthma. The WRA and possible WRA estimates based on LLP and LLP/CP samples in 2012 were comparable, as CP users are younger and less likely to have WRA. The substantial upward shift in the 2012 WRA estimates likely was associated with the revision to the WRA section. PMID:26865467
Finucane, Kevin E; Singh, Bhajan
2009-11-01
Hyperpnea with exercise or hypercapnia causes phasic contraction of abdominal muscles, potentially lengthening the diaphragm at end expiration and unloading it during inspiration. Muscle efficiency in vitro varies with load, fiber length, and precontraction stretch. To examine whether these properties of muscle contractility determine diaphragm efficiency (Eff(di)) in vivo, we measured Eff(di) in six healthy adults breathing air and during progressive hypercapnia at three levels of end-tidal Pco(2) with mean values of 48 (SD 2), 55 (SD 2), and 61 (SD 1) Torr. Eff(di) was estimated as the ratio of diaphragm power (Wdi) [the product of mean inspiratory transdiaphragmatic pressure, diaphragm volume change (DeltaVdi) measured fluoroscopically, and 1/inspiratory duration (Ti(-1))] to activation [root mean square values of inspiratory diaphragm electromyogram (RMS(di)) measured from esophageal electrodes]. At maximum hypercapnea relative to breathing air, 1) gastric pressure and diaphragm length at end expiration (Pg(ee) and Ldi(ee), respectively) increased 1.4 (SD 0.2) and 1.13 (SD 0.08) times, (P < 0.01 for both); 2) inspiratory change (Delta) in Pg decreased from 4.5 (SD 2.2) to -7.7 (SD 3.8) cmH(2)O (P < 0.001); 3) DeltaVdi.Ti(-1), Wdi, RMS(di), and Eff(di) increased 2.7 (SD 0.6), 4.9 (SD 1.8), 2.6 (SD 0.9), and 1.8 (SD 0.3) times, respectively (P < 0.01 for all); and 4) net and inspiratory Wdi were not different (P = 0.4). Eff(di) was predicted from Ldi(ee) (P < 0.001), Pg(ee) (P < 0.001), DeltaPg.Ti(-1) (P = 0.03), and DeltaPg (P = 0.04) (r(2) = 0.52) (multivariate regression analysis). We conclude that, with hypercapnic hyperpnea, 1) approximately 47% of the maximum increase of Wdi was attributable to increased Eff(di); 2) Eff(di) increased due to preinspiratory lengthening and inspiratory unloading of the diaphragm, consistent with muscle behavior in vitro; 3) passive recoil of the diaphragm did not contribute to inspiratory Wdi or Eff(di); and 4) phasic
A Large Block Experiment for Measurement of the Effective Permeability of Indiana Limestone
NASA Astrophysics Data System (ADS)
Selvadurai, P. A.; Selvadurai, A. P.
2009-12-01
The measurement of permeability of large specimens of a rock specimen is bound to provide a clearer picture of the distribution of permeability of predominantly sedimentary rocks. Such distributions can be the basis for evaluating the effective permeability of the rock specimen in the presence of permeability inhomogeneity. This paper discusses the development of a patch permeability test that can be used to measure the near surface permeability characteristics of a large cuboidal block of Indiana Limestone measuring 508 mm. The test is used to generate the near surface permeability of six faces of the cuboid and these estimates are used to generate, via a kriging procedure, the interior permeability distributions of permeability. These permeability distributions are used to examine the validity of theoretical estimates that have been developed in the literature to determine the effective permeability of the material. The classical Wiener (1912) bounds, the estimates provided by Matheron (1967) and Journel et al. (1993) are developed using the experimentally derived data. The procedure is also validated by conducting computational experiments involving one-dimensional flow along three orthogonal directions. References: Wiener, O. (1912) Die Theorie des Mischkörpers für das Feld des stationaären Strömung. Erste Abhandlung die Mittelswertesätsze für Kraft, Polarisation und Energie. Abh. Math.-Physischen Klasse Königl. Säcsh Gesell. Wissen, 32: 509-604. Matheron, G. (1967) Eléments pour une Théorie des Milieux Poroeux, Masson, Paris. Journel, A.G, Deutsch, C.V. and Desbrats, A.J. (1986) Power averaging for block effective permeability, SPE 15128, Society of Petroleum Engineers.
Measuring Vascular Permeability In Vivo.
Meijer, Eelco F J; Baish, James W; Padera, Timothy P; Fukumura, Dai
2016-01-01
Over the past decades, in vivo vascular permeability measurements have provided significant insight into vascular functions in physiological and pathophysiological conditions such as the response to pro- and anti-angiogenic signaling, abnormality of tumor vasculature and its normalization, and delivery and efficacy of therapeutic agents. Different approaches for vascular permeability measurements have been established. Here, we describe and discuss a conventional 2D imaging method to measure vascular permeability, which was originally documented by Gerlowski and Jain in 1986 (Microvasc Res 31:288-305, 1986) and further developed by Yuan et al. in the early 1990s (Microvasc Res 45:269-289, 1993; Cancer Res 54:352-3356, 1994), and our recently developed 3D imaging method, which advances the approach originally described by Brown et al. in 2001 (Nat Med 7:864-868, 2001). PMID:27581015
Heat exchange in boundary layer on permeable plate at injection and combustion
NASA Astrophysics Data System (ADS)
Lukashov, V. V.; Terekhov, V. V.; Hanjalič, K.
2014-12-01
The peculiarities of the heat and mass exchange in a laminar boundary layer with combustion at the injection of the fuel mixture H2/N2 through the permeable surface are considered. It is shown that at a certain value of the injection parameter, the value of the heat flux into the wall averaged over the length has a maximum. An analytic estimate is proposed for determining the maximum heat flux at the combustion depending on the injection intensity. The obtained relations agree with the results of experimental studies and numerical modelling.
Heat exchange in boundary layer on permeable plate at injection and combustion
NASA Astrophysics Data System (ADS)
Lukashov, V. V.; Terekhov, V. V.; Hanjalič, K.
2013-12-01
The peculiarities of the heat and mass exchange in a laminar boundary layer with combustion at the injection of the fuel mixture H2/N2 through the permeable surface are considered. It is shown that at a certain value of the injection parameter, the value of the heat flux into the wall averaged over the length has a maximum. An analytic estimate is proposed for determining the maximum heat flux at the combustion depending on the injection intensity. The obtained relations agree with the results of experimental studies and numerical modelling.
NASA Astrophysics Data System (ADS)
Armitage, P. J.; Faulkner, D. R.; Worden, R. H.; Illife, J.
2008-12-01
Caprock properties play a crucial role in determining the seal capacity of a structure and so are important during exploration, appraisal and field development. Less attention has been paid to caprocks than reservoirs since if petroleum is present, then the seal must be working. However, injection of CO2 to underlying reservoirs will alter the reservoir conditions from those against which the caprock was previously effective. Increased knowledge of the petrological and petrophysical characteristics of caprocks is required in order to lay a foundation to predict the effect of the altered conditions caused by CO2 injection. Vertical (kv) and horizontal (kh) permeability were measured experimentally across a range of effective pressures for an unusually coarse grained, heterogeneous caprock (siltstone) to a natural gas reservoir and current CO2 storage reservoir, from the Krechba Field, Algeria. Permeabilities as low as 10-23m2 were recorded and were in the range of, or lower than typical fine grained siliciclastic caprock lithologies. The permeability was analysed in conjunction with mercury injection porosimetry data, and textural and mineralogical data from traditional light microscopy, backscatter secondary electron microscopy (BSEM) and cathode luminescence (CL) techniques as well as new QEMSCAN techniques to elucidate the controls on permeability. As predicted and measured by previous experimental work on fine grained siliciclastic lithologies, permeability is effectively controlled by porosity, pore size distribution and clay fraction. Permeability generally decreases with decreasing porosity and poresize distribution and increasing clay content. However, scatter in the trends was caused by heterogeneity of the sample leading to large kv and kh ratios. Primary depositional features led to layers of relatively low and high permeability in the samples, with kv controlled by the lowest permeability layer, and kh controlled by highest permeability layer. Thus kh
Permeability enhancement by shock cooling
NASA Astrophysics Data System (ADS)
Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean
2015-04-01
The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of
Air permeability and trapped-air content in two soils
Stonestrom, D.A.; Rubin, J.
1989-01-01
To improve understanding of hysteretic air permeability relations, a need exists for data on the water content dependence of air permeability, matric pressure, and air trapping (especially for wetting-drying cycles). To obtain these data, a special instrument was designed. The instrument is a combination of a gas permeameter (for air permeability determination), a suction plate apparatus (for retentivity curve determination), and an air pycnometer (for trapped-air-volume determination). This design allowed values of air permeability, matric pressure, and air trapping to be codetermined, i.e., determined at the same values of water content using the same sample and the same inflow-outflow boundaries. Such data were obtained for two nonswelling soils. -from Authors
Frog striated muscle is permeable to hydroxide and buffer anions.
Venosa, R A; Kotsias, B A; Horowicz, P
1994-04-01
Hydroxide, bicarbonate and buffer anion permeabilities in semitendinosus muscle fibers of Rana pipiens were measured. In all experiments, the fibers were initially equilibrated in isotonic, high K2SO4 solutions at pHo = 7.2 buffered with phosphate. Two different methods were used to estimate permeabilities: (i) membrane potential changes were recorded in response to changes in external ion concentrations, and (ii) intracellular pH changes were recorded in response to changes in external concentrations of ions that alter intracellular pH. Constant field equations were used to calculate relative or absolute permeabilities. In the first method, to increase the size of the membrane potential change produced by a sudden change in anion entry, external K+ was replaced by Cs+ prior to changes of the anion under study. At constant external Cs+ activity, a hyperpolarization results from increasing external pH from 7.2 to 10.0 or higher, using either CAPS (3-[cyclohexylamino]-1-propanesulfonic acid) or CHES (2-[N-cyclohexylamino]-ethanesulfonic acid) as buffer. For each buffer, the protonated form is a zwitterion of zero net charge and the nonprotonated form is an anion. Using reported values of H+ permeability, calculations show that the reduction in [H+]o cannot account for the hyperpolarizations produced by alkaline solutions. Membrane hyperpolarization increases with increasing total external buffer concentration at constant external pH, and with increasing external pH at constant external buffer anion concentration. Taken together, these observations indicate that both OH- and buffer anions permeate the surface membrane. The following relative permeabilities were obtained at pHo = 10.0 +/- 0.3: (POH/PK) = 890 +/- 150, (PCAPS/PK) = 12 +/- 2, (PCHES/PK) = 5.3 +/- 0.9, and (PNO3/PK) = 4.7 +/- 0.5. PNO3/PK was independent of pHo up to 10.75. At pHo = 9.6, (PHCO3/PK) = 0.49 +/- 0.03; at pHo = 8.9, (PCl/PK) = 18 +/- 2 and at pHo = 7.1, (PHEPES/PK) = 20 +/- 2. In the second
NASA Astrophysics Data System (ADS)
Ariu, Kaito; Inamori, Takaya; Funase, Ryu; Nakasuka, Shinichi
2016-08-01
The world's first micro-spacecraft, "Proximate Object Close flYby with Optical Navigation" (PROCYON) has the advanced mission to approach an asteroid in dozen km (a one-order closer imaging distance compared with previous probes). In such a close distance encounter, the estimation of the relative trajectory of the target is necessary to perform autonomous imaging. However, the estimation is difficult owing to rapid changes of the line-of-sight direction of the target body. To overcome this problem, a novel dimensionless or direction only relative trajectory estimation algorithm, which uses a least square method, is proposed. The evaluation function for the least square method coincides with the error property of picture information to enable all of its calculations to be recursive and linear. It is suited for the implementation on the limited on-board computer. Numerical simulation results indicate that the proposed algorithm should enable the one-order closer flyby observation.
Huggins, Richard
2013-10-01
Precise estimation of the relative risk of motorcyclists being involved in a fatal accident compared to car drivers is difficult. Simple estimates based on the proportions of licenced drivers or riders that are killed in a fatal accident are biased as they do not take into account the exposure to risk. However, exposure is difficult to quantify. Here we adapt the ideas behind the well known induced exposure methods and use available summary data on speeding detections and fatalities for motorcycle riders and car drivers to estimate the relative risk of a fatality for motorcyclists compared to car drivers under mild assumptions. The method is applied to data on motorcycle riders and car drivers in Victoria, Australia in 2010 and a small simulation study is conducted.
Lee, Lukas Jyuhn-Hsiarn; Lin, Cheng-Kuan; Hung, Mei-Chuan; Wang, Jung-Der
2016-12-01
This study estimates the annual numbers of eight work-related cancers, total losses of quality-adjusted life years (QALYs), and lifetime healthcare expenditures that possibly could be saved by improving occupational health in Taiwan. Three databases were interlinked: the Taiwan Cancer Registry, the National Mortality Registry, and the National Health Insurance Research Database. Annual numbers of work-related cancers were estimated based on attributable fractions (AFs) abstracted from a literature review. The survival functions for eight cancers were estimated and extrapolated to lifetime using a semi-parametric method. A convenience sample of 8846 measurements of patients' quality of life with EQ-5D was collected for utility values and multiplied by survival functions to estimate quality-adjusted life expectancies (QALEs). The loss-of-QALE was obtained by subtracting the QALE of cancer from age- and sex-matched referents simulated from national vital statistics. The lifetime healthcare expenditures were estimated by multiplying the survival probability with mean monthly costs paid by the National Health Insurance for cancer diagnosis and treatment and summing this for the expected lifetime. A total of 3010 males and 726 females with eight work-related cancers were estimated in 2010. Among them, lung cancer ranked first in terms of QALY loss, with an annual total loss-of-QALE of 28,463 QALYs and total lifetime healthcare expenditures of US$36.6 million. Successful prevention of eight work-related cancers would not only avoid the occurrence of 3736 cases of cancer, but would also save more than US$70 million in healthcare costs and 46,750 QALYs for the Taiwan society in 2010. PMID:27413666
Lee, Lukas Jyuhn-Hsiarn; Lin, Cheng-Kuan; Hung, Mei-Chuan; Wang, Jung-Der
2016-12-01
This study estimates the annual numbers of eight work-related cancers, total losses of quality-adjusted life years (QALYs), and lifetime healthcare expenditures that possibly could be saved by improving occupational health in Taiwan. Three databases were interlinked: the Taiwan Cancer Registry, the National Mortality Registry, and the National Health Insurance Research Database. Annual numbers of work-related cancers were estimated based on attributable fractions (AFs) abstracted from a literature review. The survival functions for eight cancers were estimated and extrapolated to lifetime using a semi-parametric method. A convenience sample of 8846 measurements of patients' quality of life with EQ-5D was collected for utility values and multiplied by survival functions to estimate quality-adjusted life expectancies (QALEs). The loss-of-QALE was obtained by subtracting the QALE of cancer from age- and sex-matched referents simulated from national vital statistics. The lifetime healthcare expenditures were estimated by multiplying the survival probability with mean monthly costs paid by the National Health Insurance for cancer diagnosis and treatment and summing this for the expected lifetime. A total of 3010 males and 726 females with eight work-related cancers were estimated in 2010. Among them, lung cancer ranked first in terms of QALY loss, with an annual total loss-of-QALE of 28,463 QALYs and total lifetime healthcare expenditures of US$36.6 million. Successful prevention of eight work-related cancers would not only avoid the occurrence of 3736 cases of cancer, but would also save more than US$70 million in healthcare costs and 46,750 QALYs for the Taiwan society in 2010.
Hansen, Hendrik H.G.; Richards, Michael S.; Doyley, Marvin M.; de Korte, Chris L.
2013-01-01
Atherosclerotic plaque rupture can initiate stroke or myocardial infarction. Lipid-rich plaques with thin fibrous caps have a higher risk to rupture than fibrotic plaques. Elastic moduli differ for lipid-rich and fibrous tissue and can be reconstructed using tissue displacements estimated from intravascular ultrasound radiofrequency (RF) data acquisitions. This study investigated if modulus reconstruction is possible for noninvasive RF acquisitions of vessels in transverse imaging planes using an iterative 2D cross-correlation based displacement estimation algorithm. Furthermore, since it is known that displacements can be improved by compounding of displacements estimated at various beam steering angles, we compared the performance of the modulus reconstruction with and without compounding. For the comparison, simulated and experimental RF data were generated of various vessel-mimicking phantoms. Reconstruction errors were less than 10%, which seems adequate for distinguishing lipid-rich from fibrous tissue. Compounding outperformed single-angle reconstruction: the interquartile range of the reconstructed moduli for the various homogeneous phantom layers was approximately two times smaller. Additionally, the estimated lateral displacements were a factor of 2–3 better matched to the displacements corresponding to the reconstructed modulus distribution. Thus, noninvasive elastic modulus reconstruction is possible for transverse vessel cross sections using this cross-correlation method and is more accurate with compounding. PMID:23478602
Hansen, Hendrik H G; Richards, Michael S; Doyley, Marvin M; de Korte, Chris L
2013-01-01
Atherosclerotic plaque rupture can initiate stroke or myocardial infarction. Lipid-rich plaques with thin fibrous caps have a higher risk to rupture than fibrotic plaques. Elastic moduli differ for lipid-rich and fibrous tissue and can be reconstructed using tissue displacements estimated from intravascular ultrasound radiofrequency (RF) data acquisitions. This study investigated if modulus reconstruction is possible for noninvasive RF acquisitions of vessels in transverse imaging planes using an iterative 2D cross-correlation based displacement estimation algorithm. Furthermore, since it is known that displacements can be improved by compounding of displacements estimated at various beam steering angles, we compared the performance of the modulus reconstruction with and without compounding. For the comparison, simulated and experimental RF data were generated of various vessel-mimicking phantoms. Reconstruction errors were less than 10%, which seems adequate for distinguishing lipid-rich from fibrous tissue. Compounding outperformed single-angle reconstruction: the interquartile range of the reconstructed moduli for the various homogeneous phantom layers was approximately two times smaller. Additionally, the estimated lateral displacements were a factor of 2-3 better matched to the displacements corresponding to the reconstructed modulus distribution. Thus, noninvasive elastic modulus reconstruction is possible for transverse vessel cross sections using this cross-correlation method and is more accurate with compounding.
Estimation of selenium intake in Switzerland in relation to selected food groups.
Jenny-Burri, J; Haldimann, M; Dudler, V
2010-11-01
The selenium concentration in foods was analysed in order to identify principal sources of this trace element in Switzerland. Selenium intake estimations based on three different approaches were carried out. From the relationship between intake and serum/plasma concentration, the selenium intake was estimated to 66 µg day(-1). The second approach based on measured food groups combined with consumption statistics; and the third approach consisted of duplicate meal samples. With the last two methods, over 75% of the serum/plasma based intake was confirmed. Swiss pasta made of North American durum wheat was the food with the highest contribution to the dietary intake, followed by meat. The strong decrease in imports of selenium-rich North American wheat of the last years was not reflected in the present intake estimations. It appears that this intake loss was compensated by a consumption increase of other foods. Compared with former intake estimations, selenium intake seems to be in Switzerland nearly constant for the last 25 years.
ERIC Educational Resources Information Center
Lemaire, Patrick; Lecacheur, Mireille
2011-01-01
Third, fifth, and seventh graders selected the best strategy (rounding up or rounding down) for estimating answers to two-digit addition problems. Executive function measures were collected for each individual. Data showed that (a) children's skill at both strategy selection and execution improved with age and (b) increased efficiency in executive…
ERIC Educational Resources Information Center
Proyer, Rene T.
2011-01-01
The study examines the relation between subjectively assessed adult playfulness and psychometric and self-estimated intelligence in a sample of 254 students. As expected, playfulness existed widely independently from psychometric intelligence. Correlations pointed in the direction of higher expressive playfulness and numeric intelligence and lower…
Risk Factors for Learning-Related Behavior Problems at 24 Months of Age: Population-Based Estimates
ERIC Educational Resources Information Center
Morgan, Paul L.; Farkas, George; Hillemeier, Marianne M.; Maczuga, Steven
2009-01-01
We used a large sample of singleton children to estimate the effects of socioeconomic status (SES), race/ethnicity, gender, additional socio-demographics, gestational and birth factors, and parenting on children's risk for learning-related behavior problems at 24 months of age. We investigated to what extent these factors increased a child's risk…
Bayesian estimation of the relative toxicity of (239)Pu and (226)Ra with dependent competing risks
NASA Astrophysics Data System (ADS)
Xiao, Shili
The purpose of this dissertation research is to compare the toxicity of the alpha-emitting, bone-seeking radionuclides sp{239}Pu and sp{226}Ra, develop a model for radiation induced osteosarcomas, and analyze the survival data of beagles exposed to these radionuclides. This research integrates the knowledge of radiation protection, survival theory and methods (competing risks, maximum likelihood estimation, and Bayesian techniques), numerical integration techniques (Monte Carlo, Lattice rule and Gauss-quadrature) and object-oriented programming in C++. The outline of this research is: (1) survival data preprocessing, (2) model identification and selection, (3) introduction of FGM model, the dependent competing risk model created by Farlie, Gumbel and Morgenstern, to the study of survival data with dependent competing risks: osteosarcomas and other diseases, development of the crude density of the FGM model and construction of the likelihood function for the FGM model, (4) Bayesian estimates of the posterior marginal density of the toxicity ratio in the FGM model using several numerical integration techniques (Monte Carlo, Lattice rule and Gaussian Quadrature), (5) construction of the likelihood function for the independent competing risk model, Bayesian estimate of the posterior marginal density of toxicity ratio in the model using Monte Carlo method, which is compared with the posterior marginal densities for the toxicity ratio obtained from the FGM model, (6) Bayesian estimates of all other parameters in the FGM model using Monte Carlo method, (7) Comparison of the cumulative hazard for sp{239}Pu calculated according to the model with Nelson's cumulative hazard plot under Bayesian point estimates of parameters and the mean activity in each injection level, (8) Comparison of the toxicity of plutonium in osteosarcoma with that of radium under Bayesian point estimates of parameters an d the selected activit of 0.85 muCsbi, (7) discuss Bayesian prediction of the
The MMRD relation of the Galactic Novae: insights from a new distance estimation method
NASA Astrophysics Data System (ADS)
Ak, Tansel; Guver, Tolga; Ozdonmez, Aykut
2016-07-01
In order to re-establish the Maximum Magnitude Rate of Decline (MMRD) relation of galactic novae, we used the distances of them obtained from the reddening-distance relations and expansion parallaxes. We investigated the relation using about 70 Galactic novae, which have the distance measurement, the magnitude at maximum of the nova outburst and the decline rate, and compared the relation with that found for M31. It is possible to use the MMRD relation as a standard tool for distance measurement. In addition, the relations for our Galaxy and the ones obtained from other galaxies can be compared to understand the differences of nova distributions in different galaxies.
Nieto Camargo, Jorge E. Jensen, Jerry L.
2012-09-15
Reservoir compartments, typical targets for infill well locations, are commonly created by faults that may reduce permeability. A narrow fault may consist of a complex assemblage of deformation elements that result in spatially variable and anisotropic permeabilities. We report on the permeability structure of a km-scale fault sampled through drilling a faulted siliciclastic aquifer in central Texas. Probe and whole-core permeabilities, serial CAT scans, and textural and structural data from the selected core samples are used to understand permeability structure of fault zones and develop predictive models of fault zone permeability. Using numerical flow simulation, it is possible to predict permeability anisotropy associated with faults and evaluate the effect of individual deformation elements in the overall permeability tensor. We found relationships between the permeability of the host rock and those of the highly deformed (HD) fault-elements according to the fault throw. The lateral continuity and predictable permeability of the HD fault elements enhance capability for estimating the effects of subseismic faulting on fluid flow in low-shale reservoirs.
Evaluation of permeable fractures in rock aquifers
NASA Astrophysics Data System (ADS)
Bok Lee, Hang
2015-04-01
In this study, the practical usefulness and fundamental applicability of a self-potential (SP) method for identifying the permeable fractures were evaluated by a comparison of SP methods with other geophysical logging methods and hydraulic tests. At a 10 m-shallow borehole in the study site, the candidates of permeable fractures crossing the borehole were first determined by conventional geophysical methods such as an acoustic borehole televiwer, temperature, electrical conductivity and gamma-gamma loggings, which was compared to the analysis by the SP method. Constant pressure injection and recovery tests were conducted for verification of the hydraulic properties of the fractures identified by various logging methods. The acoustic borehole televiwer and gamma-gamma loggings detected the open space or weathering zone within the borehole, but they cannot prove the possibility of a groundwater flow through the detected fractures. The temperature and electrical conductivity loggings had limitations to detect the fractured zones where groundwater in the borehole flows out to the surrounding rock aquifers. Comparison of results from different methods showed that there is a best correlation between the distribution of hydraulic conductivity and the variation of the SP signals, and the SP logging can estimate accurately the hydraulic activity as well as the location of permeable fractures. Based on the results, the SP method is recommended for determining the hydraulically-active fractures rather than other conventional geophysical loggings. This self-potential method can be effectively applied in the initial stage of a site investigation which selects the optimal location and evaluates the hydrogeological property of fractures in target sites for the underground structure including the geothermal reservoir and radioactive waste disposal.
Fu, Bo; Wang, Wenbin; Shi, Xin
2015-12-01
Delay of the diagnosis of hepatitis C virus (HCV), and its treatment to avert cirrhosis, is often present sincethe early stage of HCV progression is latent. Current methods to determine the incubation time to HCV-related cirrhosis and the duration time from cirrhosis to subsequent events (e.g. complications or death) used to be based on the time of liver biopsy diagnosis and ignore this delay which led to an interval censoring for the first event time and a double censoring for the subsequent event time. To investigate the impact of this delay in estimating HCV progression rates and relevant estimating bias, we present a correlated two-stage progression model for delayed diagnosis time and fit the developed model to the previously studied hepatitis C cohort data from Edinburgh. Our analysis shows that taking the delayed diagnosis into account gives a mildly different estimate of progression rate to cirrhosis and significantly lower estimated progression rate to HCV-related death in comparison with conventional modelling. We also find that when the delay increases, the bias in estimating progression increases significantly.