Das Thermometerproblem fuer eine kleine strahlende Kugel in einem stroemenden Medium (The Thermometry Problem for a Small Sphere in a Flowing Medium),

DTIC Science & Technology

conduction and radiation. The sphere is assumed to be sufficiently small so that Reynolds number, Peclet number and Bouguer number are much smaller than one. The results are obtained by an asymptotic expansion.

Dispersive effects on multicomponent transport through porous media

NASA Astrophysics Data System (ADS)

Dutta, Sourav; Daripa, Prabir

2017-11-01

We use a hybrid numerical method to solve a global pressure based porous media flow model of chemical enhanced oil recovery. This is an extension of our recent work. The numerical method is based on the use of a discontinuous finite element method and the modified method of characteristics. The impact of molecular diffusion and mechanical dispersion on the evolution of scalar concentration distributions are studied through numerical simulations of various flooding schemes. The relative importance of the advective, capillary diffusive and dispersive fluxes are compared over different flow regimes defined in the parameter space of Capillary number, Peclet number, longitudinal and transverse dispersion coefficients. Such studies are relevant for the design of effective injection policies and determining optimal combinations of chemical components for improving recovery. This work has been possible due to financial support from the U.S. National Science Foundation Grant DMS-1522782.

Interaction of 3H+ (as HTO) and 36Cl- (as Na36Cl) with crushed granite and corresponding fracture infill material investigated in column experiments.

PubMed

Štamberg, K; Palágyi, Š; Videnská, K; Havlová, V

The transport of 3 H + (as HTO) and 36 Cl - (as Na 36 Cl) was investigated in the dynamic system, i.e., in the columns filled with crushed pure granite and fracture infill of various grain sizes. The aim of column experiments was to determine important transport parameter, such as the retardation, respectively distribution coefficients, Peclet numbers and hydrodynamic dispersion coefficients. Furthermore, the research was focused to quantification of the effect of grain size on migration of studied radionuclides. The experimental breakthrough curves were fitted by a model based on the erfc-function, assuming a linear reversible equilibrium sorption/desorption isotherm, and the above mentioned transport parameters were determined. The results showed that influence of grain size on sorption of 3 H + and 36 Cl - was negligible. Retardation and distribution coefficients of both tracers converged to one and zero, respectively, in case of all fractions of crushed granite and infill material. Generally, the presumed ion exclusion of 36 Cl in anionic form was proved under given conditions, only very weak one seems to exist in a case of infill material. In principal, both radionuclides behaved as non-sorbing, conservative tracers. On the other hand, the influence of grain size on Peclet numbers value and on dispersion coefficient was observed for both crystalline materials, namely in agreement with theoretical suppositions that the values of Peclet numbers decrease with increasing grain size and values of dispersion coefficient increase.

Analysis of the effects of atomic mass, jet velocity, and radiative cooling on the dimensionless parameters of counter-propagating, weakly collisional plasma flows

NASA Astrophysics Data System (ADS)

Collins, Gilbert; Valenzuela, Julio; Beg, Farhat

2016-10-01

We have studied the collision of counter-propagating plasma flows using opposing conical wire arrays driven by the 200kA, 150ns rise-time `GenASIS' driver. These plasma flows produced weakly collisional, well-defined bow-shock structures. Varying initial parameters such as the opening angle of the array and the atomic mass of the wires allowed us to modify quantities such as the density contrast between jets, intra-jet mean free path (λmfp, scales with v, atomic mass A, and ionization state Zi-4) , Reynolds number (Re, scales with AZ), and the Peclet number (Pe, scales with Z). We calculate these dimensionless quantities using schlieren imagery, interferometry, and emission data, and determine whether they meet the scaling criteria necessary for the comparison to and subsequent study of astrophysical plasmas. This work was partially supported by the Department of Energy Grant Number DE-SC0014493.

Pore-scale and Continuum Simulations of Solute Transport Micromodel Benchmark Experiments

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

Oostrom, Martinus; Mehmani, Yashar; Romero Gomez, Pedro DJ

Four sets of micromodel nonreactive solute transport experiments were conducted with flow velocity, grain diameter, pore-aspect ratio, and flow focusing heterogeneity as the variables. The data sets were offered to pore-scale modeling groups to test their simulators. Each set consisted of two learning experiments, for which all results was made available, and a challenge experiment, for which only the experimental description and base input parameters were provided. The experimental results showed a nonlinear dependence of the dispersion coefficient on the Peclet number, a negligible effect of the pore-aspect ratio on transverse mixing, and considerably enhanced mixing due to flow focusing.more » Five pore-scale models and one continuum-scale model were used to simulate the experiments. Of the pore-scale models, two used a pore-network (PN) method, two others are based on a lattice-Boltzmann (LB) approach, and one employed a computational fluid dynamics (CFD) technique. The learning experiments were used by the PN models to modify the standard perfect mixing approach in pore bodies into approaches to simulate the observed incomplete mixing. The LB and CFD models used these experiments to appropriately discretize the grid representations. The continuum model use published non-linear relations between transverse dispersion coefficients and Peclet numbers to compute the required dispersivity input values. Comparisons between experimental and numerical results for the four challenge experiments show that all pore-scale models were all able to satisfactorily simulate the experiments. The continuum model underestimated the required dispersivity values and, resulting in less dispersion. The PN models were able to complete the simulations in a few minutes, whereas the direct models needed up to several days on supercomputers to resolve the more complex problems.« less

An adjoint-based framework for maximizing mixing in binary fluids

NASA Astrophysics Data System (ADS)

Eggl, Maximilian; Schmid, Peter

2017-11-01

Mixing in the inertial, but laminar parameter regime is a common application in a wide range of industries. Enhancing the efficiency of mixing processes thus has a fundamental effect on product quality, material homogeneity and, last but not least, production costs. In this project, we address mixing efficiency in the above mentioned regime (Reynolds number Re = 1000 , Peclet number Pe = 1000) by developing and demonstrating an algorithm based on nonlinear adjoint looping that minimizes the variance of a passive scalar field which models our binary Newtonian fluids. The numerical method is based on the FLUSI code (Engels et al. 2016), a Fourier pseudo-spectral code, which we modified and augmented by scalar transport and adjoint equations. Mixing is accomplished by moving stirrers which are numerically modeled using a penalization approach. In our two-dimensional simulations we consider rotating circular and elliptic stirrers and extract optimal mixing strategies from the iterative scheme. The case of optimizing shape and rotational speed of the stirrers will be demonstrated.

Marangoni Convection during Free Electron Laser Nitriding of Titanium

NASA Astrophysics Data System (ADS)

Höche, Daniel; Müller, Sven; Rapin, Gerd; Shinn, Michelle; Remdt, Elvira; Gubisch, Maik; Schaaf, Peter

2009-08-01

Pure titanium was treated by free electron laser (FEL) radiation in a nitrogen atmosphere. As a result, nitrogen diffusion occurs and a TiN coating was synthesized. Local gradients of interfacial tension due to the local heating lead to a Marangoni convection, which determines the track properties. Because of the experimental inaccessibility of time-dependent occurrences, finite element calculations were performed, to determine the physical processes such as heat transfer, melt flow, and mass transport. In order to calculate the surface deformation of the gas-liquid interface, the level set approach was used. The equations were modified and coupled with heat-transfer and diffusion equations. The process was characterized by dimensionless numbers such as the Reynolds, Peclet, and capillary numbers, to obtain more information about the acting forces and the coating development. Moreover, the nitrogen distribution was calculated using the corresponding transport equation. The simulations were compared with cross-sectional micrographs of the treated titanium sheets and checked for their validity. Finally, the process presented is discussed and compared with similar laser treatments.

Analytical determination of the heat transfer coefficient for gas, liquid and liquid metal flows in the tube based on stochastic equations and equivalence of measures for continuum

NASA Astrophysics Data System (ADS)

Dmitrenko, Artur V.

2017-11-01

The stochastic equations of continuum are used for determining the heat transfer coefficients. As a result, the formulas for Nusselt (Nu) number dependent on the turbulence intensity and scale instead of only on the Reynolds (Peclet) number are proposed for the classic flows of a nonisothermal fluid in a round smooth tube. It is shown that the new expressions for the classical heat transfer coefficient Nu, which depend only on the Reynolds number, should be obtained from these new general formulas if to use the well-known experimental data for the initial turbulence. It is found that the limitations of classical empirical and semiempirical formulas for heat transfer coefficients and their deviation from the experimental data depend on different parameters of initial fluctuations in the flow for different experiments in a wide range of Reynolds or Peclet numbers. Based on these new dependences, it is possible to explain that the differences between the experimental results for the fixed Reynolds or Peclet numbers are caused by the difference in values of flow fluctuations for each experiment instead of only due to the systematic error in the experiment processing. Accordingly, the obtained general dependences of Nu for a smooth round tube can serve as the basis for clarifying the experimental results and empirical formulas used for continuum flows in various power devices. Obtained results show that both for isothermal and for nonisothermal flows, the reason for the process of transition from a deterministic state into a turbulent one is determined by the physical law of equivalence of measures between them. Also the theory of stochastic equations and the law of equivalence of measures could determine mechanics which is basis in different phenomena of self-organization and chaos theory.

Peclet number analysis of cross-flow in porous gas diffusion layer of polymer electrolyte membrane fuel cell (PEMFC).

PubMed

Suresh, P V; Jayanti, Sreenivas

2016-10-01

Adoption of hydrogen economy by means of using hydrogen fuel cells is one possible solution for energy crisis and climate change issues. Polymer electrolyte membrane (PEM) fuel cell, which is an important type of fuel cells, suffers from the problem of water management. Cross-flow is induced in some flow field designs to enhance the water removal. The presence of cross-flow in the serpentine and interdigitated flow fields makes them more effective in proper distribution of the reactants on the reaction layer and evacuation of water from the reaction layer than diffusion-based conventional parallel flow fields. However, too much of cross-flow leads to flow maldistribution in the channels, higher pressure drop, and membrane dehydration. In this study, an attempt has been made to quantify the amount of cross-flow required for effective distribution of reactants and removal of water in the gas diffusion layer. Unit cells containing two adjacent channels with gas diffusion layer (GDL) and catalyst layer at the bottom have been considered for the parallel, interdigitated, and serpentine flow patterns. Computational fluid dynamics-based simulations are carried out to study the reactant transport in under-the-rib area with cross-flow in the GDL. A new criterion based on the Peclet number is presented as a quantitative measure of cross-flow in the GDL. The study shows that a cross-flow Peclet number of the order of 2 is required for effective removal of water from the GDL. Estimates show that this much of cross-flow is not usually produced in the U-bends of Serpentine flow fields, making these areas prone to flooding.

On the penetration of a hot diapir through a strongly temperature-dependent viscosity medium

NASA Technical Reports Server (NTRS)

Daly, S. F.; Raefsky, A.

1985-01-01

The ascent of a hot spherical body through a fluid with a strongly temperature-dependent viscosity has been studied using an axisymmetric finite element method. Numerical solutions range over Peclet numbers of 0.1 - 1000 from constant viscosity up to viscosity variations of 100,000. Both rigid and stress-free boundary conditions were applied at the surface of the sphere. The dependence of drag on viscosity variation was shown to have no dependence on the stress boundary condition except for a Stokes flow scaling factor. A Nusselt number parameterization based on the stress-free constant viscosity functional dependence on the Peclet number scaled by a parameter depending on the viscosity structure fits both stress-free and rigid boundary condition data above viscosity variations of 100. The temperature scale height was determined as a function of sphere radius. For the simple physical model studied in this paper pre-heating is required to reduce the ambient viscosity of the country rock to less than 10 to the 22nd sq cm/s in order for a 10 km diapir to penetrate a distance of several radii.

Doubled heterogeneous crystal nucleation in sediments of hard sphere binary-mass mixtures

NASA Astrophysics Data System (ADS)

Löwen, Hartmut; Allahyarov, Elshad

2011-10-01

Crystallization during the sedimentation process of a binary colloidal hard spheres mixture is explored by Brownian dynamics computer simulations. The two species are different in buoyant mass but have the same interaction diameter. Starting from a completely mixed system in a finite container, gravity is suddenly turned on, and the crystallization process in the sample is monitored. If the Peclet numbers of the two species are both not too large, crystalline layers are formed at the bottom of the cell. The composition of lighter particles in the sedimented crystal is non-monotonic in the altitude: it is first increasing, then decreasing, and then increasing again. If one Peclet number is large and the other is small, we observe the occurrence of a doubled heterogeneous crystal nucleation process. First, crystalline layers are formed at the bottom container wall which are separated from an amorphous sediment. At the amorphous-fluid interface, a secondary crystal nucleation of layers is identified. This doubled heterogeneous nucleation can be verified in real-space experiments on colloidal mixtures.

Ultrafast electrokinetics.

PubMed

Rouhi Youssefi, Mehrnaz; Diez, Francisco Javier

2016-03-01

The influence of a high electric field applied on both fluid flow and particle velocities is quantified at large Peclet numbers. The experiments involved simultaneous particle image velocimetry and flow rate measurements. These are conducted in polydimethylsiloxane channels with spherical nonconducting polystyrene particles and DI water as the background flow. The high electric field tests produced up to three orders of magnitude higher electrokinetic velocities than any previous reports. The maximum electroosmotic velocity and electrophoretic velocity measured were 3.55 and 2.3 m/s. Electrophoretic velocities are measured over the range of 100 V/cm < E < 250 000 V/cm. The results are separated according to the different nonlinear theoretical models, including low and high Peclet numbers, and weak and strong concentration polarization. They show good agreement with the models. Such fast velocities could be used for flow separation, mixing, transport, control, and manipulation of suspended particles as well as microthrust generation among other applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Linear analysis of the Richtmyer-Meshkov instability in shock-flame interactions

NASA Astrophysics Data System (ADS)

Massa, L.; Jha, P.

2012-05-01

Shock-flame interactions enhance supersonic mixing and detonation formation. Therefore, their analysis is important to explosion safety, internal combustion engine performance, and supersonic combustor design. The fundamental process at the basis of the interaction is the Richtmyer-Meshkov instability supported by the density difference between burnt and fresh mixtures. In the present study we analyze the effect of reactivity on the Richtmyer-Meshkov instability with particular emphasis on combustion lengths that typify the scaling between perturbation growth and induction. The results of the present linear analysis study show that reactivity changes the perturbation growth rate by developing a pressure gradient at the flame surface. The baroclinic torque based on the density gradient across the flame acts to slow down the instability growth of high wave-number perturbations. A gasdynamic flame representation leads to the definition of a Peclet number representing the scaling between perturbation and thermal diffusion lengths within the flame. Peclet number effects on perturbation growth are observed to be marginal. The gasdynamic model also considers a finite flame Mach number that supports a separation between flame and contact discontinuity. Such a separation destabilizes the interface growth by augmenting the tangential shear.

Study of fracture and stress-induced morphological instabilities in polymeric materials

NASA Astrophysics Data System (ADS)

Sabouri-Ghomi, Mohsen

We study the phenomena of fracture in polymers at the molecular and continuum level. At a molecular level, we study the failure of polymer/polymer interfaces. Our main focus is on a specific mode of failure known as chain pull-out fracture, which is common to weak adhesive junctions, and polymer blends and mixtures. In the case of the interface between incompatible polymers, reinforcement is achieved by adding a block copolymer to the interface. We introduce a microscopic model based on Brownian dynamics to investigate the effect of the polymerization index N, of the block connector chain, on fracture toughness of such reinforced polymeric junctions. We consider the mushroom regime, where connector chains are grafted with low surface density, for the case of large pulling velocity. We find that for short chains the interface fracture toughness depends linearly on the polymerization index N of the connector chains, while for longer chains the dependence becomes N 3/2. We propose a scaling argument, based on the geometry of the initial configuration, that accounts for both short and long chains and the crossover between them. At the continuum level, we study the pattern selection mechanism of finger-like crack growth phenomena in gradient driven growth problems in general, and the structure of stress-induced morphological instabilities in crazing of polymer glasses in particular. We simulate solidification in a narrow channel through the use of a phase-field model with an adaptive grid. By tuning a dimensionless parameter, the Peclet number, we show a continuous crossover from a free dendrite at high Peclet numbers to anisotropic viscous fingering at low Peclet numbers. At low Peclet numbers we find good agreement between our results, theoretical predictions, and experiment, providing the first quantitative test of solvability theory for anisotropic viscous fingers. For high undercoolings, we find new phenomena, a solid forger which satisfies stability and thermodynamic criterion. We further provide an analytical form for the shape of these fingers, based on local models of solidification, which fits our numerical results from simulation. Later we study the growth of crazes in polymer glasses by deriving the equations of motion of plastic flow at the craze tip, and the steady-state velocity profile of this flow. By developing a phenomenological model, we solve the full time-dependent equations of motion of this highly non-linear phenomena. Our simulation produces the steady-state cellular pattern observed in experiments. We further show that polymer glasses with lower yield stress produce cellular patterns with sharper tips and more cells, indicating instabilities with smaller wavelengths.

Solutions for the diurnally forced advection-diffusion equation to estimate bulk fluid velocity and diffusivity in streambeds from temperature time series

NASA Astrophysics Data System (ADS)

Luce, C.; Tonina, D.; Gariglio, F. P.; Applebee, R.

2012-12-01

Differences in the diurnal variations of temperature at different depths in streambed sediments are commonly used for estimating vertical fluxes of water in the streambed. We applied spatial and temporal rescaling of the advection-diffusion equation to derive two new relationships that greatly extend the kinds of information that can be derived from streambed temperature measurements. The first equation provides a direct estimate of the Peclet number from the amplitude decay and phase delay information. The analytical equation is explicit (e.g. no numerical root-finding is necessary), and invertable. The thermal front velocity can be estimated from the Peclet number when the thermal diffusivity is known. The second equation allows for an independent estimate of the thermal diffusivity directly from the amplitude decay and phase delay information. Several improvements are available with the new information. The first equation uses a ratio of the amplitude decay and phase delay information; thus Peclet number calculations are independent of depth. The explicit form also makes it somewhat faster and easier to calculate estimates from a large number of sensors or multiple positions along one sensor. Where current practice requires a priori estimation of streambed thermal diffusivity, the new approach allows an independent calculation, improving precision of estimates. Furthermore, when many measurements are made over space and time, expectations of the spatial correlation and temporal invariance of thermal diffusivity are valuable for validation of measurements. Finally, the closed-form explicit solution allows for direct calculation of propagation of uncertainties in error measurements and parameter estimates, providing insight about error expectations for sensors placed at different depths in different environments as a function of surface temperature variation amplitudes. The improvements are expected to increase the utility of temperature measurement methods for studying groundwater-surface water interactions across space and time scales. We discuss the theoretical implications of the new solutions supported by examples with data for illustration and validation.

Pore-scale and continuum simulations of solute transport micromodel benchmark experiments

DOE PAGES

Oostrom, M.; Mehmani, Y.; Romero-Gomez, P.; ...

2014-06-18

Four sets of nonreactive solute transport experiments were conducted with micromodels. Three experiments with one variable, i.e., flow velocity, grain diameter, pore-aspect ratio, and flow-focusing heterogeneity were in each set. The data sets were offered to pore-scale modeling groups to test their numerical simulators. Each set consisted of two learning experiments, for which our results were made available, and one challenge experiment, for which only the experimental description and base input parameters were provided. The experimental results showed a nonlinear dependence of the transverse dispersion coefficient on the Peclet number, a negligible effect of the pore-aspect ratio on transverse mixing,more » and considerably enhanced mixing due to flow focusing. Five pore-scale models and one continuum-scale model were used to simulate the experiments. Of the pore-scale models, two used a pore-network (PN) method, two others are based on a lattice Boltzmann (LB) approach, and one used a computational fluid dynamics (CFD) technique. Furthermore, we used the learning experiments, by the PN models, to modify the standard perfect mixing approach in pore bodies into approaches to simulate the observed incomplete mixing. The LB and CFD models used the learning experiments to appropriately discretize the spatial grid representations. For the continuum modeling, the required dispersivity input values were estimated based on published nonlinear relations between transverse dispersion coefficients and Peclet number. Comparisons between experimental and numerical results for the four challenge experiments show that all pore-scale models were all able to satisfactorily simulate the experiments. The continuum model underestimated the required dispersivity values, resulting in reduced dispersion. The PN models were able to complete the simulations in a few minutes, whereas the direct models, which account for the micromodel geometry and underlying flow and transport physics, needed up to several days on supercomputers to resolve the more complex problems.« less

Strategic enzyme patterning for microfluidic biofuel cells

NASA Astrophysics Data System (ADS)

Kjeang, E.; Sinton, D.; Harrington, D. A.

The specific character of biological enzyme catalysts enables combined fuel and oxidant channels and simplified non-compartmentalized fuel cell assemblies. In this work, a microstructured enzymatic biofuel cell architecture is proposed, and species transport phenomena combined with consecutive chemical reactions are studied computationally in order to provide guidelines for optimization. This is the first computational study of this technology, and a 2D CFD model for species transport coupled with laminar fluid flow and Michaelis-Menten enzyme kinetics is established. It is shown that the system is reaction rate limited, indicating that enzyme specific turnover numbers are key parameters for biofuel cell performance. Separated and mixed enzyme patterns in different proportions are analyzed for various Peclet numbers. High fuel utilization is achieved in the diffusion dominated and mixed species transport regimes with separated enzymes arranged in relation to individual turnover rates. However, the Peclet number has to be above a certain threshold value to obtain satisfying current densities. The mixed transport regime is particularly attractive while current densities are maintained close to maximum levels. Optimum performance is achieved by mixed enzyme patterning tailored with respect to individual turnover rates, enabling high current densities combined with nearly complete fuel utilization.

Characterization of mixing in an electroosmotically stirred continuous micro mixer

NASA Astrophysics Data System (ADS)

Beskok, Ali

2005-11-01

We present theoretical and numerical studies of mixing in a straight micro channel with zeta potential patterned surfaces. A steady pressure driven flow is maintained in the channel in addition to a time dependent electroosmotic flow, generated by a stream-wise AC electric field. The zeta potential patterns are placed critically in the channel to achieve spatially asymmetric time-dependent flow patterns that lead to chaotic stirring. Fixing the geometry, we performed parametric studies of passive particle motion that led to generation of Poincare sections and characterization of chaotic strength by finite time Lyapunov exponents. The parametric studies were performed as a function of the Womersley number (normalized AC frequency) and the ratio of Poiseuille flow and electroosmotic velocities. After determining the non-dimensional parameters that led to high chaotic strength, we performed spectral element simulations of species transport and mixing at high Peclet numbers, and characterized mixing efficiency using the Mixing Index inverse. Mixing lengths proportional to the natural logarithm of the Peclet number are reported. Using the optimum non-dimensional parameters and the typical magnitudes involved in electroosmotic flows, we were able to determine the physical dimensions and operation conditions for a prototype micro-mixer.

Inertial effects on heat transfer in superhydrophobic microchannels

NASA Astrophysics Data System (ADS)

Cowley, Adam; Maynes, Daniel; Crockett, Julie; Iverson, Brian; BYU Fluids Team

2015-11-01

This work numerically studies the effects of inertia on thermal transport in superhydrophbic microchannels. An infinite parallel plate channel comprised of structured superhydrophbic walls is considered. The structure of the superhydrophobic surfaces consists of square pillars organized in a square array aligned with the flow direction. Laminar, fully developed flow is explored. The flow is assumed to be non-wetting and have an idealized flat meniscus. A shear-free, adiabatic boundary condition is used at the liquid/gas interface, while a no-slip, constant heat flux condition is used at the liquid/solid interface. A wide range of Peclet numbers, relative channel spacing distances, and relative pillar sizes are considered. Results are presented in terms of Poiseuille number, Nusselt number, hydrodynamic slip length, and temperature jump length. Interestingly, the thermal transport is varied only slightly by inertial effects for a wide range of parameters explored and compares well with other analytical and numerical work that assumed Stokes flow. It is only for very small relative channel spacing and large Peclet number that inertial effects exert significant influence. Overall, the heat transfer is reduced for the superhydrophbic channels in comparison to classic smooth walled channels. This research was supported by the National Science Foundation (NSF) - United States (Grant No. CBET-1235881).

Mathematical Studies and Simulations of Nematic Liquid Crystal Polymers and Nanocomposites

DTIC Science & Technology

2010-01-01

around the folding point of the phase curve. As the Peclet number increases, the stable branch and the unstable branch of the fold are peeled off from...shaped, boomerang-shaped or banana shaped.76 Recall that in a nematic phase the molecules tend to align along the director n. A biax- ial nematic phase

Oscillating-flow regenerator test rig: Woven screen and metal felt results

NASA Technical Reports Server (NTRS)

Gedeon, D.; Wood, J. G.

1992-01-01

We present correlating expressions, in terms of Reynolds or Peclet numbers, for friction factors, Nusselt numbers, enhanced axial conduction ratios, and overall heat flux ratios in four porous regenerator samples representative of stirling cycle regenerators: two woven screen samples and two random wire samples. Error estimates and comparison of data with others suggest our correlations are reliable, but we need to test more samples over a range of porosities before our results will become generally useful.

Lifecycle of miscible viscous fingering: onset to shutdown

NASA Astrophysics Data System (ADS)

Nijjer, Japinder S.; Hewitt, Duncan R.; Neufeld, Jerome A.

2017-11-01

When a viscous fluid is injected into a porous medium or Hele-Shaw cell that is initially saturated with a more viscous fluid, the flow can be unstable to viscous fingering. We investigate the long-time dynamics of miscible viscous fingering in a homogeneous, planar, two-dimensional porous medium using high-resolution numerical simulations. At late times, we identify a new flow regime which consists of a pair of counter-propagating fingers that diffuse and slow, leaving a linearly well-mixed interior. We derive an analytic solution for this regime, and show that, in contrast to previous suggestions, the flow always evolves to this regime irrespective of the viscosity ratio and Peclet number. As a consequence, we find the instability can only ever generate a finite amount of advective mixing. We also describe the full life-cycle of miscible viscous fingering, which can be partitioned into three regimes: an early-time linearly unstable regime, an intermediate-time non-linear regime, and a late-time exchange-flow regime. We identify, using linear stability theory, a critical Peclet number below which the flow is always stable, and derive a model for the evolution of the transversely averaged concentration in the intermediate-time regime, which extends previous empirical models.

Correlations by the entrainment theory of thermodynamic effects for developed cavitation in venturis and comparisons with ogive data

NASA Technical Reports Server (NTRS)

Billet, M. L.; Holl, J. W.; Weir, D. S.

1975-01-01

A semi-empirical entrainment theory was employed to correlate the measured temperature depression, Delta T, in a developed cavity for a venturi. This theory correlates Delta t in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, Weber and Peclet, and dimensionless cavity length, L/D. These correlations are then compared with similar correlations for zero and quarter caliber ogives. In addition, cavitation number data for both limited and developed cavitation in venturis are presented.

Dynamics of miscible displacements in round tubes

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

Meiburg, E.; Maxworthy, T.; Chen, C.Y.

A combined experimental and numerical investigation of miscible two-phase flow in a capillary tube is reported. The fraction of fluid left behind on the wall is obtained as a function of the Peclet, Atwood, and Froude numbers. Scaling arguments are presented for two distinct flow regimes, dominated by diffusion and convection, respectively. In the latter one, an effective surface tension value can be estimated.

Power-law scaling in Bénard-Marangoni convection at large Prandtl numbers

NASA Astrophysics Data System (ADS)

Boeck, Thomas; Thess, André

2001-08-01

Bénard-Marangoni convection at large Prandtl numbers is found to exhibit steady (nonturbulent) behavior in numerical experiments over a very wide range of Marangoni numbers Ma far away from the primary instability threshold. A phenomenological theory, taking into account the different character of thermal boundary layers at the bottom and at the free surface, is developed. It predicts a power-law scaling for the nondimensional velocity (Peclet number) and heat flux (Nusselt number) of the form Pe~Ma2/3, Nu~Ma2/9. This prediction is in good agreement with two-dimensional direct numerical simulations up to Ma=3.2×105.

Unifying Pore Network Modeling, Continuous Time Random Walk Theory and Experiment - Accomplishments and Future Directions

NASA Astrophysics Data System (ADS)

Bijeljic, B.

2008-05-01

This talk will describe and highlight the advantages offered by a methodology that unifies pore network modeling, CTRW theory and experiment in description of solute dispersion in porous media. Solute transport in a porous medium is characterized by the interplay of advection and diffusion (described by Peclet number, Pe) that cause spreading of solute particles. This spreading is traditionally described by dispersion coefficients, D, defined by σ 2 = 2Dt, where σ 2 is the variance of the solute position and t is the time. Using a pore-scale network model based on particle tracking, the rich Peclet- number dependence of dispersion coefficient is predicted from first principles and is shown to compare well with experimental data for restricted diffusion, transition, power-law and mechanical dispersion regimes in the asymptotic limit. In the asymptotic limit D is constant and can be used in an averaged advection-dispersion equation. However, it is highly important to recognize that, until the velocity field is fully sampled, the particle transport is non-Gaussian and D possesses temporal or spatial variation. Furthermore, temporal probability density functions (PDF) of tracer particles are studied in pore networks and an excellent agreement for the spectrum of transition times for particles from pore to pore is obtained between network model results and CTRW theory. Based on the truncated power-law interpretation of PDF-s, the physical origin of the power-law scaling of dispersion coefficient vs. Peclet number has been explained for unconsolidated porous media, sands and a number of sandstones, arriving at the same conclusion from numerical network modelling, analytic CTRW theory and experiment. Future directions for further applications of the methodology presented are discussed in relation to the scale- dependent solute dispersion and reactive transport. Significance of pre-asymptotic dispersion in porous media is addressed from pore-scale upwards and the impact of heterogeneity is discussed. The length traveled by solute plumes before Gaussian behaviour is reached increases with an increase in heterogeneity and/or Pe. This opens up the question on the nature of dispersion in natural systems where the heterogeneities at the larger scales will profoundly increase the range of velocities in the aquifer, thus considerably delaying the asymptotic approach to Gaussian behaviour. As a consequence, the asymptotic behaviour might not be reached at the field scale.

Effects of a temperature-dependent rheology on large scale continental extension

NASA Technical Reports Server (NTRS)

Sonder, Leslie J.; England, Philip C.

1988-01-01

The effects of a temperature-dependent rheology on large-scale continental extension are investigated using a thin viscous sheet model. A vertically-averaged rheology is used that is consistent with laboratory experiments on power-law creep of olivine and that depends exponentially on temperature. Results of the calculations depend principally on two parameters: the Peclet number, which describes the relative rates of advection and diffusion of heat, and a dimensionless activation energy, which controls the temperature dependence of the rheology. At short times following the beginning of extension, deformation occurs with negligible change in temperature, so that only small changes in lithospheric strength occur due to attenuation of the lithosphere. However, after a certain critical time interval, thermal diffusion lowers temperatures in the lithosphere, strongly increasing lithospheric strength and slowing the rate of extension. This critical time depends principally on the Peclet number and is short compared with the thermal time constant of the lithosphere. The strength changes cause the locus of high extensional strain rates to shift with time from regions of high strain to regions of low strain. Results of the calculations are compared with observations from the Aegean, where maximum extensional strains are found in the south, near Crete, but maximum present-day strain rates are largest about 300 km further north.

A functional relation for field-scale nonaqueous phase liquid dissolution developed using a pore network model

USGS Publications Warehouse

Dillard, L.A.; Essaid, H.I.; Blunt, M.J.

2001-01-01

A pore network model with cubic chambers and rectangular tubes was used to estimate the nonaqueous phase liquid (NAPL) dissolution rate coefficient, Kdissai, and NAPL/water total specific interfacial area, ai. Kdissai was computed as a function of modified Peclet number (Pe???) for various NAPL saturations (SN) and ai during drainage and imbibition and during dissolution without displacement. The largest contributor to ai was the interfacial area in the water-filled corners of chambers and tubes containing NAPL. When Kdissai was divided by ai, the resulting curves of dissolution coefficient, Kdiss versus Pe??? suggested that an approximate value of Kdiss could be obtained as a weak function of hysteresis or SN. Spatially and temporally variable maps of Kdissai calculated using the network model were used in field-scale simulations of NAPL dissolution. These simulations were compared to simulations using a constant value of Kdissai and the empirical correlation of Powers et al. [Water Resour. Res. 30(2) (1994b) 321]. Overall, a methodology was developed for incorporating pore-scale processes into field-scale prediction of NAPL dissolution. Copyright ?? 2001 .

Electrophoretic and Electrolytic Deposition of Ceramic Particles on Porous Substrates

DTIC Science & Technology

1990-08-30

hydrodynamic drag force exerted on the particle due to the electroosmotic flow of the solvent inside the pore, the electrophoretic force exerted on the...8217 - electrophoretic velocity UN - electroosmotic velocity b - pore mean radius D - diffusion coefficient k - local deposition rate Large Peclet numbers and small...experimentally as the charge is acquired spontaneously on mixing the particles with the solvent and it may be reversed upon addition ot ionic compounds. The

Studies on dispersive stabilization of porous media flows

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

Daripa, Prabir, E-mail: prabir.daripa@math.tamu.edu; Gin, Craig

Motivated by a need to improve the performance of chemical enhanced oil recovery (EOR) processes, we investigate dispersive effects on the linear stability of three-layer porous media flow models of EOR for two different types of interfaces: permeable and impermeable interfaces. Results presented are relevant for the design of smarter interfaces in the available parameter space of capillary number, Peclet number, longitudinal and transverse dispersion, and the viscous profile of the middle layer. The stabilization capacity of each of these two interfaces is explored numerically and conditions for complete dispersive stabilization are identified for each of these two types ofmore » interfaces. Key results obtained are (i) three-layer porous media flows with permeable interfaces can be almost completely stabilized by diffusion if the optimal viscous profile is chosen, (ii) flows with impermeable interfaces can also be almost completely stabilized for short time, but become more unstable at later times because diffusion flattens out the basic viscous profile, (iii) diffusion stabilizes short waves more than long waves which leads to a “turning point” Peclet number at which short and long waves have the same growth rate, and (iv) mechanical dispersion further stabilizes flows with permeable interfaces but in some cases has a destabilizing effect for flows with impermeable interfaces, which is a surprising result. These results are then used to give a comparison of the two types of interfaces. It is found that for most values of the flow parameters, permeable interfaces suppress flow instability more than impermeable interfaces.« less

Enhanced heat transport during phase separation of liquid binary mixtures

NASA Astrophysics Data System (ADS)

Molin, Dafne; Mauri, Roberto

2007-07-01

We show that heat transfer in regular binary fluids is enhanced by induced convection during phase separation. The motion of binary mixtures is simulated using the diffuse interface model, where convection and diffusion are coupled via a nonequilibrium, reversible Korteweg body force. Assuming that the mixture is regular, i.e., its components are van der Waals fluids, we show that the two parameters that describe the mixture, namely the Margules constant and the interfacial thickness, depend on temperature as T-1 and T-1/2, respectively. Two quantities are used to measure heat transfer, namely the heat flux at the walls and the characteristic cooling time. Comparing these quantities with those of very viscous mixtures, where diffusion prevails over convection, we saw that the ratio between heat fluxes, which defines the Nusselt number, NNu, equals that between cooling times and remains almost constant in time. The Nusselt number depends on the following: the Peclet number, NPe, expressing the ratio between convective and diffusive mass fluxes; the Lewis number, NLe, expressing the ratio between thermal and mass diffusivities; the specific heat of the mixture, as it determines how the heat generated by mixing can be stored within the system; and the quenching depth, defined as the distance of the temperature at the wall from its critical value. In particular, the following results were obtained: (a) The Nusselt number grows monotonically with the Peclet number until it reaches an asymptotic value at NNu≈2 when NPe≈106; (b) the Nusselt number increases with NLe when NLe<1, remains constant at 11; (c) the Nusselt number is hardly influenced by the specific heat; (d) the Nusselt number decreases as the quenching rate increases. All these results can be explained by physical considerations. Predictably, considering that convection is within the creeping flow regime, the Nusselt number is always of o(10).

Air sparging: Air-water mass transfer coefficients

NASA Astrophysics Data System (ADS)

Braida, Washington J.; Ong, Say Kee

1998-12-01

Experiments investigating the mass transfer of several dissolved volatile organic compounds (VOCs) across the air-water interface were conducted using a single-air- channel air-sparging system. Three different porous media were used in the study. Air velocities ranged from 0.2 cm s-1 to 2.5 cm s-1. The tortuosity factor for each porous medium and the air-water mass transfer coefficients were estimated by fitting experimental data to a one-dimensional diffusion model. The estimated mass transfer coefficients KG ranged from 1.79 × 10-3 cm min-1 to 3.85 × 10-2 cm min-1. The estimated lumped gas phase mass transfer coefficients KGa were found to be directly related to the air diffusivity of the VOC, air velocity, and particle size, and inversely related to the Henry's law constant of the VOCs. Of the four parameters investigated, the parameter that controlled or had a dominant effect on the lumped gas phase mass transfer coefficient was the air diffusivity of the VOC. Two empirical models were developed by correlating the Damkohler and the modified air phase Sherwood numbers with the air phase Peclet number, Henry's law constant, and the reduced mean particle size of porous media. The correlation developed in this study may be used to obtain better predictions of mass transfer fluxes for field conditions.

Thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity

NASA Technical Reports Server (NTRS)

Lan, C. W.; Kou, Sindo

1990-01-01

Computer simulation of steady-state axisymmetrical heat transfer and fluid flow was conducted to study thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity. The effects of key variables on the extent of thermocapillary flow in the melt zone, the shapes of melt/solid interfaces and the length of the melt zone were discussed. These variables are: (1) the temperature coefficient of surface tension (or the Marangoni number), (2) the pulling speed (or the Peclet number), (3) the feed rod radius, (4) the ambient temperature distribution, (5) the heat transfer coefficient (or the Biot number), and (6) the thermal diffusivity of the material (or the Prandtl number).

Numerical analysis of transient laminar forced convection of nanofluids in circular ducts

NASA Astrophysics Data System (ADS)

Sert, İsmail Ozan; Sezer-Uzol, Nilay; Kakaç, Sadık

2013-10-01

In this study, forced convection heat transfer characteristics of nanofluids are investigated by numerical analysis of incompressible transient laminar flow in a circular duct under step change in wall temperature and wall heat flux. The thermal responses of the system are obtained by solving energy equation under both transient and steady-state conditions for hydro-dynamically fully-developed flow. In the analyses, temperature dependent thermo-physical properties are also considered. In the numerical analysis, Al2O3/water nanofluid is assumed as a homogenous single-phase fluid. For the effective thermal conductivity of nanofluids, Hamilton-Crosser model is used together with a model for Brownian motion in the analysis which takes the effects of temperature and the particle diameter into account. Temperature distributions across the tube for a step jump of wall temperature and also wall heat flux are obtained for various times during the transient calculations at a given location for a constant value of Peclet number and a particle diameter. Variations of thermal conductivity in turn, heat transfer enhancement is obtained at various times as a function of nanoparticle volume fractions, at a given nanoparticle diameter and Peclet number. The results are given under transient and steady-state conditions; steady-state conditions are obtained at larger times and enhancements are found by comparison to the base fluid heat transfer coefficient under the same conditions.

Unifying Pore Network Modeling, Continuous Time Random Walk (CTRW) Theory and Experiment to Describe Impact of Spatial Heterogeneities on Solute Dispersion at Multiple Length-scales

NASA Astrophysics Data System (ADS)

Bijeljic, B.; Blunt, M. J.; Rhodes, M. E.

2009-04-01

This talk will describe and highlight the advantages offered by a novel methodology that unifies pore network modeling, CTRW theory and experiment in description of solute dispersion in porous media. Solute transport in a porous medium is characterized by the interplay of advection and diffusion (described by Peclet number, Pe) that cause dispersion of solute particles. Dispersion is traditionally described by dispersion coefficients, D, that are commonly calculated from the spatial moments of the plume. Using a pore-scale network model based on particle tracking, the rich Peclet-number dependence of dispersion coefficient is predicted from first principles and is shown to compare well with experimental data for restricted diffusion, transition, power-law and mechanical dispersion regimes in the asymptotic limit. In the asymptotic limit D is constant and can be used in an averaged advection-dispersion equation. However, it is highly important to recognize that, until the velocity field is fully sampled, the particle transport is non-Gaussian and D possesses temporal or spatial variation. Furthermore, temporal probability density functions (PDF) of tracer particles are studied in pore networks and an excellent agreement for the spectrum of transition times for particles from pore to pore is obtained between network model results and CTRW theory. Based on the truncated power-law interpretation of PDF-s, the physical origin of the power-law scaling of dispersion coefficient vs. Peclet number has been explained for unconsolidated porous media, sands and a number of sandstones, arriving at the same conclusion from numerical network modelling, analytic CTRW theory and experiment. The length traveled by solute plumes before Gaussian behaviour is reached increases with an increase in heterogeneity and/or Pe. This opens up the question on the nature of dispersion in natural systems where the heterogeneities at the larger scales will significantly increase the range of velocities in the reservoir, thus significantly delaying the asymptotic approach to Gaussian behaviour. As a consequence, the asymptotic behaviour might not be reached at the field scale. This is illustrated by the multi-scale approach in which transport at core, gridblock and field scale is viewed as a series of particle transitions between discrete nodes governed by probability distributions. At each scale of interest a distribution that represents transport physics (and the heterogeneity) is used as an input to model a subsequent reservoir scale. The extensions to reactive transport are discussed.

Modelling of Tc migration in an un-oxidized fractured drill core from Äspö, Sweden

NASA Astrophysics Data System (ADS)

Huber, F. M.; Totskiy, Y.; Montoya Garcia, V.; Enzmann, F.; Trumm, M.; Wenka, A.; Geckeis, H.; Schaefer, T.

2015-12-01

The radionuclide retention of redox sensitive radionuclides (e.g. Pu, Np, U, Tc) in crystalline host rock greatly depends on the rock matrix and the rock redox capacity. Preservation of drill cores concerning oxidation is therefore of paramount importance to reliably predict the near-natural radionuclide retention properties. Here, experimental results of HTO and Tc laboratory migration experiments in a naturally single fractured Äspö un-oxidized drill core are modelled using two different 2D models. Both models employ geometrical information obtained by μ-computed tomography (μCT) scanning of the drill core. The models differ in geometrical complexity meaning the first model (PPM-MD) consists of a simple parallel plate with a porous matrix adjacent to the fracture whereas the second model (MPM) uses the mid-plane of the 3D fracture only (no porous matrix). Simulation results show that for higher flow rates (Peclet number > 1), the MPM satisfactorily describes the HTO breakthrough curves (BTC) whereas the PPM-MD model nicely reproduces the HTO BTC for small Pe numbers (<1). These findings clearly highlight the influence of fracture geometry/flow field complexity on solute transport for Pe numbers > 1 and the dominating effect of matrix diffusion for Peclet numbers < 1. Retention of Tc is modelled using a simple Kd-approach in case of the PPM-MD and including 1st order sorptive reduction/desorption kinetics in case of the MPM. Batch determined sorptive reduction/desorption kinetic rates and Kd values for Tc on non-oxidized Äspö diorite are used in the model and compared to best fit values. By this approach, the transferability of kinetic data concerning sorptive reduction determined in static batch experiments to dynamic transport experiments is examined.

Numerical study of vorticity-enhanced heat transfer

NASA Astrophysics Data System (ADS)

Wang, Xiaolin; Alben, Silas

2013-11-01

Vortices produced by vibrated reeds and flapping foils can improve heat transfer efficiency in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we modeled and simulated the fluid flow and temperature in a 2-D channel flow with vortices injected at the upstream boundary. We classified four types of vortex streets depending on the Reynolds number and vortices' strengths and spacings, and studied the different vortex dynamics in each situation. We then used Lagrangian coherent structures (LCS) to study the effect of the vortices on mixing and determined how the Nusselt number and Coefficients of performance vary with flow parameters and Peclet numbers.

Stellar convection 2: A multi-mode numerical solution for convection in spheres

NASA Technical Reports Server (NTRS)

Marcus, P. S.

1979-01-01

The convective flow of a self gravitating sphere of Boussinesq fluid for small Reynolds and Peclet numbers is numerically determined. The decomposition of the equations of motion into modes is reviewed and a relaxation method is developed and presented to compute the solutions to these equations. The stable equilibrium flow for a Rayleigh number of 10 to the 4th power and a Prandtl number of 10 is determined. The 2 and 3 dimensional spectra of the kinetic and thermal energies and the convective flux as a function of wavelengths are calculated in terms of modes. The anisotropy of the flow as a function of wavelength is defined.

Two-dimensional numerical modeling and solution of convection heat transfer in turbulent He II

NASA Technical Reports Server (NTRS)

Zhang, Burt X.; Karr, Gerald R.

1991-01-01

Numerical schemes are employed to investigate heat transfer in the turbulent flow of He II. FEM is used to solve a set of equations governing the heat transfer and hydrodynamics of He II in the turbulent regime. Numerical results are compared with available experimental data and interpreted in terms of conventional heat transfer parameters such as the Prandtl number, the Peclet number, and the Nusselt number. Within the prescribed Reynolds number domain, the Gorter-Mellink thermal counterflow mechanism becomes less significant, and He II acts like an ordinary fluid. The convection heat transfer characteristics of He II in the highly turbulent regime can be successfully described by using the conventional turbulence and heat transfer theories.

Effect of an insoluble surfactant on the dynamics of a thin liquid film flowing over a non-uniformly heated substrate.

PubMed

Srivastava, Ashna; Tiwari, Naveen

2018-05-07

The stability analysis of a gravity-driven thin liquid film with an insoluble surfactant flowing over a surface with embedded, regularly spaced heaters is investigated. At the leading edge of a heater, the presence of a temperature gradient induces an opposing Marangoni stress at the interface leading to the formation of a capillary ridge. This ridge has been shown to be susceptible to thermocapillary (oscillating in the flow direction) and rivulet (spanwise periodic pattern) instabilities. The presence of an insoluble surfactant is shown to have a stabilizing effect on this system. The governing equations for the evolution of the film thickness and surfactant concentration are obtained within the lubrication approximation. The coupled two-dimensional base solutions for the film thickness and surfactant concentration show that there is no significant change in the height of the capillary ridge at the subsequent heaters downstream. The height of the capillary ridge is reduced by the presence of the surfactant. For very small Peclet number, the presence of multiple heaters has almost no significant effect on the film stability as compared to a single heater and similar trends are observed between the two configurations in the presence of the surfactant as for the case of a clean interface. However, for large Peclet number, the effect was observed on both types of instabilities for certain heater configurations. The Biot number is shown to have a strong effect on the stability results wherein the dominant mode of instability is altered (from rivulet to thermocapillary instability) for a passive or no surfactant case with increase in the Biot number. For an active surfactant thermocapillary instability is found to remain the dominant mode of instability for all the values of the Biot number. It is shown that increasing the number of heaters beyond a couple does not further affect the stability results.

On the autonomous motion of active drops or bubbles.

PubMed

Ryazantsev, Yuri S; Velarde, Manuel G; Guzman, Eduardo; Rubio, Ramón G; Ortega, Francisco; Montoya, Juan-Jose

2018-05-19

Thermo-capillary stresses on the surface of a drop can be the result of a non-isothermal surface chemical conversion of a reactant dissolved in the host fluid. The strength of heat production (with e.g. absorption) on the surface is ruled by the diffusion of the reactant and depends on the state of motion of the drop. Such thermo-capillary stresses can provoke the motion of the drop or its motionless state in the presence of an external body force. If in the balance of forces, including indeed viscous drag, the net resultant force vanishes there is the possibility of autonomous motion with constant velocity of the drop. Focusing on drops with radii in the millimeter range provided here is a quantitative study of the possibility of such autonomous motion when the drop, considered as active unit, is seat of endo- or exo-thermic reactive processes that dominate its motion. The framework is restricted to Stokes flows in the hydrodynamics, negligible heat Peclet number while the solute Peclet number is considered very high. A boundary layer approximation is used in the description of reactant diffusion. Those processes eventually end up in the action being expressed by surface tension gradients and the Marangoni effect. Explicit expressions of the force acting on the drop and the velocity fields inside and outside the drop are provided. Some significant particular cases are discussed to illustrate the usefulness of the theory. Copyright © 2018. Published by Elsevier Inc.

Roles of additives and surface control in slurry atomization. Final project report

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

Tsai, S.C.

1992-12-31

This project studies the rheology and airblast atomization of micronized coal slurries. Its major objectives are (1) to promote further understanding of the mechanisms and the roles of additives in airblast atomization of coal water slurry (CWS), and (2) to investigate the impacts of coal particle surface properties and interparticle forces on CWS rheology. We have found that the flow behavior index (n) of a suspension (or slurry) is determined by the relative importance of the interparticle van der Waals attraction and the interparticle electrostatic repulsion. The interparticle attraction, measured by the Hamaker constant scaled to the thermal energy atmore » 25{degrees}C (A/kT), causes particle aggregation, which breaks down at high shear rates, and thus leads to slurry pseudoplastic behavior (n< 1). At a constant particle volume fraction and surface charge density (qualitatively measured by the zeta potential in deionized water), n decreases linearly as A/kT increases. The relative viscosity of the pseudoplastic suspension with respect to that of the suspending liquid is found to be independent of particle density and correlate well with the particle Peclet number which equals the particle diffusional relaxation time multiplied by shear rate. Specifically, the relative viscosities of the pseudoplastic glycerol/water coal slurry and the ethylene glycol/glycerol sand slurry, at same volume fractions as well as similar particle size distributions and liquid viscosities, as functions of the particle Peclet number fall along the same line.« less

Roles of additives and surface control in slurry atomization

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

Tsai, S.C.

1992-01-01

This project studies the rheology and airblast atomization of micronized coal slurries. Its major objectives are (1) to promote further understanding of the mechanisms and the roles of additives in airblast atomization of coal water slurry (CWS), and (2) to investigate the impacts of coal particle surface properties and interparticle forces on CWS rheology. We have found that the flow behavior index (n) of a suspension (or slurry) is determined by the relative importance of the interparticle van der Waals attraction and the interparticle electrostatic repulsion. The interparticle attraction, measured by the Hamaker constant scaled to the thermal energy atmore » 25[degrees]C (A/kT), causes particle aggregation, which breaks down at high shear rates, and thus leads to slurry pseudoplastic behavior (n< 1). At a constant particle volume fraction and surface charge density (qualitatively measured by the zeta potential in deionized water), n decreases linearly as A/kT increases. The relative viscosity of the pseudoplastic suspension with respect to that of the suspending liquid is found to be independent of particle density and correlate well with the particle Peclet number which equals the particle diffusional relaxation time multiplied by shear rate. Specifically, the relative viscosities of the pseudoplastic glycerol/water coal slurry and the ethylene glycol/glycerol sand slurry, at same volume fractions as well as similar particle size distributions and liquid viscosities, as functions of the particle Peclet number fall along the same line.« less

Sensitivity Studies for In-Situ Automated Tape Placement of Thermoplastic Composites

NASA Technical Reports Server (NTRS)

Costen, Robert C.; Marchello, Joseph M.

2004-01-01

This modeling effort seeks to improve the interlaminate bond strength of thermoplastic carbon composites produced by the in-situ automated tape placement (ATP) process. An existing high productivity model is extended to lower values of the Peclet number that correspond to the present operating conditions of the Langley ATP robot. (The Peclet number is the dimensionless ratio of inertial to diffusive heat transfer.) In sensitivity studies, all of the process and material parameters are individually varied. The model yields the corresponding variations in the effective bonding time (EBT) referred to the glass transition temperature. According to reptation theory, the interlaminate bond strength after wetting occurs is proportional to the one-fourth power of EBT. The model also computes the corresponding variations in the thermal input power (TIP) and the mass and volumetric process rates. Process studies show that a 10 percent increase in the consolidation length results in a 20 percent increase in EBT and a 5 percent increase in TIP. A surprising result is that a 10 K decrease in the tooling temperature results in a 25 percent increase in EBT and an 8 percent increase in TIP. Material studies show that a 10 K decrease in glass transition temperature results in an 8 percent increase in EBT and a 8 percent decrease in TIP. A 20 K increase in polymer degradation temperature results in a 23 percent increase in EBT with no change in TIP.

Hydrodynamic and thermal modeling of two-dimensional microdroplet arrays for digitized heat transfer

NASA Astrophysics Data System (ADS)

Baird, Eric S.

This document describes hydrodynamic and thermal modeling of two-dimensional microdroplet arrays for use in digitized heat transfer (DHT), a novel active thermal management technique for high power density electronics and integrated microsystems. In DHT, thermal energy is transported by a discrete array of electrostatically activated microdroplets of liquid metals, alloys or aqueous solutions with the potential of supporting significantly higher heat transfer rates than classical air-cooled heat sinks. Actuation methods for dispensing and transporting individual fluid slugs with a high degree of precision and programmability are described, with simple approximate formulae for net forces for steady state and transient velocities in terms of known parameters. A modified cavity flow solver is developed to provide details on the internal flow properties of a translating microdroplet and used to detail the effects of droplet curvature, internal mixing, Peclet number and other parameters on the heat transfer capabilities of a discretized liquid flow. The concept of Nusselt number is generalized to an individual fluid slug and shown to oscillate with a period equal to the droplet's mixing rate. In whole, DHT is demonstrated to be a viable new alternative for achieving the most important objectives of electronic cooling (i.e., minimization of the maximum substrate temperature, reduction of the substrate temperature gradient and removal of substrate hot spots) and a sound fundamental description of the method's electro-, hydro- and thermodynamics is provided.

New collector efficiency equation for colloid filtration in both natural and engineered flow conditions

NASA Astrophysics Data System (ADS)

Nelson, Kirk E.; Ginn, Timothy R.

2011-05-01

A new equation for the collector efficiency (η) of the colloid filtration theory (CFT) is developed via nonlinear regression on the numerical data generated by a large number of Lagrangian simulations conducted in Happel's sphere-in-cell porous media model over a wide range of environmentally relevant conditions. The new equation expands the range of CFT's applicability in the natural subsurface primarily by accommodating departures from power law dependence of η on the Peclet and gravity numbers, a necessary but as of yet unavailable feature for applying CFT to large-scale field transport (e.g., of nanoparticles, radionuclides, or genetically modified organisms) under low groundwater velocity conditions. The new equation also departs from prior equations for colloids in the nanoparticle size range at all fluid velocities. These departures are particularly relevant to subsurface colloid and colloid-facilitated transport where low permeabilities and/or hydraulic gradients lead to low groundwater velocities and/or to nanoparticle fate and transport in porous media in general. We also note the importance of consistency in the conceptualization of particle flux through the single collector model on which most η equations are based for the purpose of attaining a mechanistic understanding of the transport and attachment steps of deposition. A lack of sufficient data for small particles and low velocities warrants further experiments to draw more definitive and comprehensive conclusions regarding the most significant discrepancies between the available equations.

Finite analytic numerical solution of heat transfer and flow past a square channel cavity

NASA Technical Reports Server (NTRS)

Chen, C.-J.; Obasih, K.

1982-01-01

A numerical solution of flow and heat transfer characteristics is obtained by the finite analytic method for a two dimensional laminar channel flow over a two-dimensional square cavity. The finite analytic method utilizes the local analytic solution in a small element of the problem region to form the algebraic equation relating an interior nodal value with its surrounding nodal values. Stable and rapidly converged solutions were obtained for Reynolds numbers ranging to 1000 and Prandtl number to 10. Streamfunction, vorticity and temperature profiles are solved. Local and mean Nusselt number are given. It is found that the separation streamlines between the cavity and channel flow are concave into the cavity at low Reynolds number and convex at high Reynolds number (Re greater than 100) and for square cavity the mean Nusselt number may be approximately correlated with Peclet number as Nu(m) = 0.365 Pe exp 0.2.

Shear induced orientation of edible fat and chocolate crystals

NASA Astrophysics Data System (ADS)

Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.

2003-03-01

Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.

Hydrograph variances over different timescales in hydropower production networks

NASA Astrophysics Data System (ADS)

Zmijewski, Nicholas; Wörman, Anders

2016-08-01

The operation of water reservoirs involves a spectrum of timescales based on the distribution of stream flow travel times between reservoirs, as well as the technical, environmental, and social constraints imposed on the operation. In this research, a hydrodynamically based description of the flow between hydropower stations was implemented to study the relative importance of wave diffusion on the spectrum of hydrograph variance in a regulated watershed. Using spectral decomposition of the effluence hydrograph of a watershed, an exact expression of the variance in the outflow response was derived, as a function of the trends of hydraulic and geomorphologic dispersion and management of production and reservoirs. We show that the power spectra of involved time-series follow nearly fractal patterns, which facilitates examination of the relative importance of wave diffusion and possible changes in production demand on the outflow spectrum. The exact spectral solution can also identify statistical bounds of future demand patterns due to limitations in storage capacity. The impact of the hydraulic description of the stream flow on the reservoir discharge was examined for a given power demand in River Dalälven, Sweden, as function of a stream flow Peclet number. The regulation of hydropower production on the River Dalälven generally increased the short-term variance in the effluence hydrograph, whereas wave diffusion decreased the short-term variance over periods of <1 week, depending on the Peclet number (Pe) of the stream reach. This implies that flow variance becomes more erratic (closer to white noise) as a result of current production objectives.

The Dynamics of Miscible Fluids: A Space Flight Experiment (MIDAS)

NASA Technical Reports Server (NTRS)

Maxworthy, T.; Meiburg, E.; Balasubramaniam, R.; Rashidnia, N.; Lauver, R.

2001-01-01

We propose a space flight experiment to study the dynamics of miscible interfaces. A less viscous fluid displaces one of higher viscosity within a tube. The two fluids are miscible in all proportions. An intruding "finger" forms that occupies a fraction of the tube. As time progresses diffusion at the interface combined with flow induced straining between the two fluids modifies the concentration and velocity distributions within the whole tube. Also, under such circumstances it has been proposed that the interfacial stresses could depend on the local concentration gradients (Korteweg stresses) and that the divergence of the velocity need not be zero, even though the flow is incompressible. We have obtained reasonable agreement for the tip velocity between numerical simulations (that ignored the Korteweg stress and divergence effects) and physical experiments only at high Peclet Numbers. However at moderate to low Pe agreement was poor. As one possibility we attributed this lack of agreement to the disregard of these effects. We propose a space experiment to measure the finger shape, tip velocity, and the velocity and concentration fields. From intercomparisons between the experiment and the calculations we can then extract values for the coefficients of the Korteweg stress terms and confirm or deny the importance of these stresses.

Direct numerical simulations of three-dimensional electrokinetic flows

NASA Astrophysics Data System (ADS)

Chiam, Keng-Hwee

2006-11-01

We discuss direct numerical simulations of three-dimensional electrokinetic flows in microfluidic devices. In particular, we focus on the study of the electrokinetic instability that develops when two solutions with different electrical conductivities are coupled to an external electric field. We characterize this ``mixing'' instability as a function of the parameters of the model, namely the Reynolds number of the flow, the electric Peclet number of the electrolyte solution, and the ratio of the electroosmotic to the electroviscous time scales. Finally, we describe how this model breaks down when the length scale of the device approaches the nanoscale, where the width of the electric Debye layer is comparable to the width of the channel, and discuss solutions to overcome this.

Numerical modeling of time-dependent bio-convective stagnation flow of a nanofluid in slip regime

NASA Astrophysics Data System (ADS)

Kumar, Rakesh; Sood, Shilpa; Shehzad, Sabir Ali; Sheikholeslami, Mohsen

A numerical investigation of unsteady stagnation point flow of bioconvective nanofluid due to an exponential deforming surface is made in this research. The effects of Brownian diffusion, thermophoresis, slip velocity and thermal jump are incorporated in the nanofluid model. By utilizing similarity transformations, the highly nonlinear partial differential equations governing present nano-bioconvective boundary layer phenomenon are reduced into ordinary differential system. The resultant expressions are solved for numerical solution by employing a well-known implicit finite difference approach termed as Keller-box method (KBM). The influence of involved parameters (unsteadiness, bioconvection Schmidt number, velocity slip, thermal jump, thermophoresis, Schmidt number, Brownian motion, bioconvection Peclet number) on the distributions of velocity, temperature, nanoparticle and motile microorganisms concentrations, the coefficient of local skin-friction, rate of heat transport, Sherwood number and local density motile microorganisms are exhibited through graphs and tables.

Nonlinear interfacial stability of core-annular film flows in the presence of surfactants

NASA Astrophysics Data System (ADS)

Kas-Danouche, Said A.

This work is an analytical and computational study of the nonlinear interfacial instabilities found in core-annular flows in the presence of surfactants. Core-annular flows arise when two immiscible fluids (for example water and oil) are caused to flow in a pipe under the action of an axial pressure gradient. In one typical type of flow regime, the fluids arrange themselves so that the less viscous (e.g. water) lies in the region of high shear near the pipe wall, with the more viscous fluid occupying the core region. Technologically, this arrangement provides an advantage since the highly viscous fluid is lubricated by the less viscous annulus and for a given pressure gradient the core-fluid flux can be greatly increased. The stability of these flows is of fundamental scientific and practical importance. The sharp interface between the two phases can become unstable by several physical mechanisms and one such mechanism of practical importance is surface tension. In this work we incorporate into our model the effects of insoluble surfactants on the instability. The full problem is derived with particular emphasis paid to the surfactant transport equation which is novel. We then carry out an asymptotic solution of the problem when the annular layer is thin compared to the core-fluid radius and for waves which are of the order of the pipe radius (that is long compared to the annular layer thickness); these scales are in accord with both linear theory as well as experimental observations. The result of the matched asymptotic analysis is a system of coupled nonlinear partial differential equations for the interfacial amplitude and the surfactant concentration on the interface. In the absence of surfactants, the system reduces to the Kuramoto-Sivashinsky equation which has been extensively studied as a paradigm for one-dimensional turbulence in dissipative systems. The surfactant modifies the flow by inducing Marangoni forces along the interface which in turn modify both the velocities and interfacial amplitudes. There are two parameters present in the nonlinear system, the length of the system and a surface Peclet number which measures the diffusion of surfactant on the interface. In order to gain an understanding of the dynamics, we carry out extensive computations using accurate and stable numerical methods capable of following the solution for long times. We map out the dynamics by numerically solving initial value problems on spatially periodic domains where the length of the system is the bifurcation parameter, keeping the Peclet number fixed and equal to one. We find that surfactant acts to suppress chaotic behavior found in its absence for extensive ranges of the bifurcation parameter. The new flow consists of successive windows (in parameter space) of steady-state traveling waves separated by time-periodic attractors. As the length of the system increases a self-similar structure has been found to govern the shapes of the traveling waves as we move from a given window to a lower one. This is elucidated analytically and numerically.

Influence of Brownian motion on blood platelet flow behavior and adhesive dynamics near a planar wall.

PubMed

Mody, Nipa A; King, Michael R

2007-05-22

We used the platelet adhesive dynamics computational method to study the influence of Brownian motion of a platelet on its flow characteristics near a surface in the creeping flow regime. Two important characterizations were done in this regard: (1) quantification of the platelet's ability to contact the surface by virtue of the Brownian forces and torques acting on it, and (2) determination of the relative importance of Brownian motion in promoting surface encounters in the presence of shear flow. We determined the Peclet number for a platelet undergoing Brownian motion in shear flow, which could be expressed as a simple linear function of height of the platelet centroid, H from the surface Pe (platelet) = . (1.56H + 0.66) for H > 0.3 microm. Our results demonstrate that at timescales relevant to shear flow in blood Brownian motion plays an insignificant role in influencing platelet motion or creating further opportunities for platelet-surface contact. The platelet Peclet number at shear rates >100 s-1 is large enough (>200) to neglect platelet Brownian motion in computational modeling of flow in arteries and arterioles for most practical purposes even at very close distances from the surface. We also conducted adhesive dynamics simulations to determine the effects of platelet Brownian motion on GPIbalpha-vWF-A1 single-bond dissociation dynamics. Brownian motion was found to have little effect on bond lifetime and caused minimal bond stressing as bond rupture forces were calculated to be less than 0.005 pN. We conclude from our results that, for the case of platelet-shaped cells, Brownian motion is not expected to play an important role in influencing flow characteristics, platelet-surface contact frequency, and dissociative binding phenomena under flow at physiological shear rates (>50 s(-1)).

Reactive multiphase flow at the pore-scale: the melting of a crystalline framework during the injection of buoyant hot volatiles

NASA Astrophysics Data System (ADS)

Andrea, P.; Huber, C.; Bachmann, O.; Chopard, B.

2010-12-01

Multiphase reactive flows occur naturally in various environments in the shallow subsurface, e.g. CO2 injections in saturated reservoirs, exsolved methane flux in shallow sediments and H20-CO2 volatiles in magmatic systems. Because of their multiphase nature together with the nonlinear feedbacks between reactions (dissolution/melting or precipitation) and the flow field at the pore-scale, the study of these dynamical processes remains a great challenge. In this study we focus on the injection of buoyant hot volatiles exsolved from a magmatic intrusion underplating a crystal-rich magma (porous medium). We use some simple theoretical models and a pore-scale multiphase reactive lattice Boltzmann model to investigate how the heat carried by the volatile phase affects the evolution of the porous medium spatially and temporally. We find that when the reaction rate is relatively slow and when the injection rate of volatiles is large (high injection Capillary number), the dissolution of the porous medium can be described by a local Peclet number (ratio of advective to diffusive flux of heat/reactant in the main gas channel). When the injection rate of volatile is reduced, or when the reaction rate is large, the dynamics transition to more complex regimes, where subvertical gas channels are no longer stable and can break into disconnected gas slugs. For the case of the injection of hot volatiles in crystal-rich magmatic systems, we find that the excess enthalpy advected by buoyant volatiles penetrates the porous medium over distances ~r Pe, where r is the average radius of the volatile channel (~pore size). The transport of heat by buoyant gases through a crystal mush is therefore in most cases limited to distances < meters. Our results also suggest that buoyant volatiles can carry chemical species (Li,F, Cl) far into a mush as their corresponding local Peclet number is several orders of magnitude greater than that for heat, owing to their low diffusion coefficients.

Radial Viscous Fingering and its Surface Expression due to Convective Upwelling Beneath North Atlantic Ocean

NASA Astrophysics Data System (ADS)

White, N. J.; Schoonman, C. M.

2016-12-01

The Icelandic mantle plume has had a significant influence on the geologic and oceanographic evolution of the North Atlantic Ocean during Cenozoic times. Full-waveform tomographic imaging of this region show that the planform of this plume has a complex irregular shape with significant shear wave velocity anomalies lying beneath the lithospheric plates between 100 and 200 km depth. The planform of these anomalies suggests that five or more horizontal fingers extend radially beneath the fringing continental margins. The best-imaged fingers lie beneath the British Isles and beneath western Norway where significant crustal isostatic departures have been measured. Here, we propose that these radial fingers are generated by a phenomenon known as the Saffman-Taylor instability. Experimental and theoretical analyses show that radial, miscible viscous fingering occurs when a less viscous fluid is injected into a more viscous fluid. The wavelength and number of fingers are controlled by the mobility (i.e. the ratio of viscosities), by the Peclet number (i.e. the ratio of advective and diffusive processes), and by the thickness of the horizontal layer into which fluid is injected. We have combined shear wave velocity estimates with residual depth measurements around the Atlantic margins to calculate the planform distribution of temperature and viscosity within an asthenospheric layer beneath the lithospheric plates. Our calculations suggest that the mobility is 20-50, that the Peclet number is O(104, and that the asthenospheric channel is 150 ± 50 km thick. The existence and form of viscous fingering is consistent with experimental observations and with linear stability analysis. A useful rule of thumb is that the wavelength of viscous fingering is 5 ± 1 times the thickness of the horizontal layer. Our proposal support the notion that dynamic topography of the Earth's surface can be influenced by rapid horizontal flow within spatially evolving asthenospheric fingers.

Radial, Viscous, Saffman-Taylor Fingering of Hot Asthenosphere associated with the Icelandic plume beneath the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

White, Nicky; Schoonman, Charlotte

2017-04-01

The Icelandic plume has had a significant influence upon the geologic and oceanographic evolution of the North Atlantic Ocean throughout Cenozoic times. Published full-waveform earthquake tomographic imaging of this region shows that the planform of this plume has a complex irregular shape with significant shear wave velocity anomalies lying beneath the lithospheric plate at depths of between 100 and 200 km. The planform of these anomalies suggests that five or more horizontal fingers extend radially beneath the fringing continental margins. The best-resolved of these fingers lie beneath the British Isles and beneath western Norway where significant crustal isostatic departures have been measured. Here, we propose that these radial fingers are generated by a well-known fluid dynamical phenomenon known as the Saffman-Taylor instability. Experimental and theoretical analyses show that radial, miscible viscous fingering occurs when a less viscous fluid is injected into a more viscous fluid. The wavelength and number of fingers are controlled by the mobility (i.e. the ratio of viscosities), by the Peclet number (i.e. the ratio of advective and diffusive processes), and by the thickness of the horizontal layer into which fluid is injected. We have combined shear wave velocity estimates with residual depth measurements around the Atlantic margins to calculate the planform distribution of temperature and viscosity within an asthenospheric layer beneath the lithospheric plates. Our calculations suggest that the mobility is 20-50, that the Peclet number is O(10000), and that the asthenospheric channel is 150 +/- 50 km thick. The existence and form of viscous fingering is consistent with experimental observations and with linear stability analysis. A useful rule of thumb is that the wavelength of viscous fingering is 5 +/- 1 times the thickness of the horizontal layer. Our proposal support the notion that dynamic topography of the Earth's surface can be generated and maintained by rapid horizontal flow within spatially evolving asthenospheric fingers.

Cool Flame Quenching

NASA Technical Reports Server (NTRS)

Pearlman, Howard; Chapek, Richard

2001-01-01

Cool flame quenching distances are generally presumed to be larger than those associated with hot flames, because the quenching distance scales with the inverse of the flame propagation speed, and cool flame propagation speeds are often times slower than those associated with hot flames. To date, this presumption has never been put to a rigorous test, because unstirred, non-isothermal cool flame studies on Earth are complicated by natural convection. Moreover, the critical Peclet number (Pe) for quenching of cool flames has never been established and may not be the same as that associated with wall quenching due to conduction heat loss in hot flames, Pe approx. = 40-60. The objectives of this ground-based study are to: (1) better understand the role of conduction heat loss and species diffusion on cool flame quenching (i.e., Lewis number effects), (2) determine cool flame quenching distances (i.e, critical Peclet number, Pe) for different experimental parameters and vessel surface pretreatments, and (3) understand the mechanisms that govern the quenching distances in premixtures that support cool flames as well as hot flames induced by spark-ignition. Objective (3) poses a unique fire safety hazard if conditions exist where cool flame quenching distances are smaller than those associated with hot flames. For example, a significant, yet unexplored risk, can occur if a multi-stage ignition (a cool flame that transitions to a hot flame) occurs in a vessel size that is smaller than that associated with the hot quenching distance. To accomplish the above objectives, a variety of hydrocarbon-air mixtures will be tested in a static reactor at elevated temperature in the laboratory (1g). In addition, reactions with chemical induction times that are sufficiently short will be tested aboard NASA's KC-135 microgravity (mu-g) aircraft. The mu-g results will be compared to a numerical model that includes species diffusion, heat conduction, and a skeletal kinetic mechanism, following the work on diffusion-controlled cool flames by Fairlie et,al., 2000.

Method of multi-dimensional moment analysis for the characterization of signal peaks

DOEpatents

Pfeifer, Kent B; Yelton, William G; Kerr, Dayle R; Bouchier, Francis A

2012-10-23

A method of multi-dimensional moment analysis for the characterization of signal peaks can be used to optimize the operation of an analytical system. With a two-dimensional Peclet analysis, the quality and signal fidelity of peaks in a two-dimensional experimental space can be analyzed and scored. This method is particularly useful in determining optimum operational parameters for an analytical system which requires the automated analysis of large numbers of analyte data peaks. For example, the method can be used to optimize analytical systems including an ion mobility spectrometer that uses a temperature stepped desorption technique for the detection of explosive mixtures.

Micromixer based on viscoelastic flow instability at low Reynolds number.

PubMed

Lam, Y C; Gan, H Y; Nguyen, N T; Lie, H

2009-03-30

We exploited the viscoelasticity of biocompatible dilute polymeric solutions, namely, dilute poly(ethylene oxide) solutions, to significantly enhance mixing in microfluidic devices at a very small Reynolds number, i.e., Re approximately 0.023, but large Peclet and elasticity numbers. With an abrupt contraction microgeometry (8:1 contraction ratio), two different dilute poly(ethylene oxide) solutions were successfully mixed with a short flow length at a relatively fast mixing time of <10 mus. Microparticle image velocimetry was employed in our investigations to characterize the flow fields. The increase in velocity fluctuation with an increase in flow rate and Deborah number indicates the increase in viscoelastic flow instability. Mixing efficiency was characterized by fluorescent concentration measurements. Our results showed that enhanced mixing can be achieved through viscoelastic flow instability under situations where molecular-diffusion and inertia effects are negligible. This approach bypasses the laminar flow limitation, usually associated with a low Reynolds number, which is not conducive to mixing.

Micromixer based on viscoelastic flow instability at low Reynolds number

PubMed Central

Lam, Y. C.; Gan, H. Y.; Nguyen, N. T.; Lie, H.

2009-01-01

We exploited the viscoelasticity of biocompatible dilute polymeric solutions, namely, dilute poly(ethylene oxide) solutions, to significantly enhance mixing in microfluidic devices at a very small Reynolds number, i.e., Re≈0.023, but large Peclet and elasticity numbers. With an abrupt contraction microgeometry (8:1 contraction ratio), two different dilute poly(ethylene oxide) solutions were successfully mixed with a short flow length at a relatively fast mixing time of <10 μs. Microparticle image velocimetry was employed in our investigations to characterize the flow fields. The increase in velocity fluctuation with an increase in flow rate and Deborah number indicates the increase in viscoelastic flow instability. Mixing efficiency was characterized by fluorescent concentration measurements. Our results showed that enhanced mixing can be achieved through viscoelastic flow instability under situations where molecular-diffusion and inertia effects are negligible. This approach bypasses the laminar flow limitation, usually associated with a low Reynolds number, which is not conducive to mixing. PMID:19693399

Characterizing Subcore Heterogeneity: A New Analytical Model and Technique to Observe the Spatial Variation of Transverse Dispersion

NASA Astrophysics Data System (ADS)

Boon, Maartje; Niu, Ben; Krevor, Sam

2015-04-01

Transverse dispersion, the lateral spread of chemical components in an aqueous solution caused by small heterogeneities in a rock, plays an important role in spreading, mixing and reaction during flow through porous media. Conventionally, transverse dispersion has been determined with the use of an annular core device and concentration measurements of the effluent (Blackwell, 1962; Hassinger and Von Rosenberg, 1968) or concentration measurements at probe locations along the core (Han et al, 1985; Harleman and Rumer, 1963). Both methods were designed around an analytical model of the transport equations assuming a single constant for the transverse dispersion coefficient, which is used to analyse the experimental data. We have developed a new core flood test with the aim of characterising chemical transport and dispersion directly in three dimensions to (1) produce higher precision observations of transverse dispersion than has been possible before and (2) so that the effects of rock heterogeneity on transport can also be observed and summarised using statistical descriptions allowing for a more nuanced picture of transport than allowed by description with a single transverse dispersion coefficient. The dispersion of a NaI aqueous solution injected into a Berea sandstone rock core was visualised in 3D with the use of a medical x-ray CT scanner. A device consisting out of three annular regions was used for injection. Water was injected into the centre and outer annular region and a NaI aqueous solution was injected in the middle annular region. An analytical solution to the flow and transport equations for this new inlet configuration was derived to design the tests. The Berea sandstone core was 20 cm long and had a diameter of 7.62cm. The core flood experiments were carried out for Peclet nr 0.5 and Peclet nr 2. At steady state, x-ray images were taken every 0.2 cm along the core. This resulted in a high quality 3D digital data set of the concentration distribution of the NaI aqueous solution at steady state for the different Peclet numbers. The average transverse dispersion coefficient (Dt) was calculated from the change in variance of the transverse distance travelled by the NaI solution along the core. A Dt of 2.396e-04 cm2/min was obtained for Peclet nr 0.5 and a Dt of 4.771e-04 cm2/min for Peclet nr 2. These values coincide precisely with the Dt calculated from the pore scale modelling on Berea sandstone of Bijeljic and Blunt, 2007, and serves as a benchmark demonstrating the utility and repeatability of the technique. This new technique shows promise for use in characterising average transport characteristics and analysing the impacts of natural rock heterogeneity. Acknowledgement: This work was carried out as part of the Qatar Carbonates and Carbon Storage Research Centre (QCCSRC). The authors gratefully acknowledge the funding of QCCSRC provided jointly by Qatar Petroleum, Shell, and the Qatar Science & Technology Park and for supporting the present project and the permission to present this research. References: 1. Blackwell, 1962 - Laboratory studies of microscopic dispersion phenomena. Society of Petroleum Engineers Journal 2, no.1:1-8 2. Bijeljic, B., and M. J. Blunt (2007), Pore-scale modeling of transverse dispersion in porous media, Water Resour. Res., 43, W12S11, doi:10.1029/2006WR005700. 3. Han, N.W., Bhakta, J and Carbonell, R.G., 1985 - Longitudinal and lateral dispersion in packed beds: Effect of column length and particle size distribution. AIChE Journal31, no.2:277-288. 4. Harleman, D.R., and R.R. Rumer. 1963. Longitudinal and lateral dispersion in an isotropic porous medium. Journal of Fluid Mechanics16, no. 2:385-394. 5. Hassinger, R.C. and Von Rosenberg, D.U., 1968 - A mathematical and experimental examination of transverse dispersion coefficients. Society of Petroleum Engineers Journal 8, no.1:195-204.

Full numerical simulation of coflowing, axisymmetric jet diffusion flames

NASA Technical Reports Server (NTRS)

Mahalingam, S.; Cantwell, B. J.; Ferziger, J. H.

1990-01-01

The near field of a non-premixed flame in a low speed, coflowing axisymmetric jet is investigated numerically using full simulation. The time-dependent governing equations are solved by a second-order, explicit finite difference scheme and a single-step, finite rate model is used to represent the chemistry. Steady laminar flame results show the correct dependence of flame height on Peclet number and reaction zone thickness on Damkoehler number. Forced simulations reveal a large difference in the instantaneous structure of scalar dissipation fields between nonbuoyant and buoyant cases. In the former, the scalar dissipation marks intense reaction zones, supporting the flamelet concept; however, results suggest that flamelet modeling assumptions need to be reexamined. In the latter, this correspondence breaks down, suggesting that modifications to the flamelet modeling approach are needed in buoyant turbulent diffusion flames.

Numerical modeling of physical vapor transport in a vertical cylindrical ampoule, with and without gravity

NASA Technical Reports Server (NTRS)

Miller, T. L.

1986-01-01

Numerical modeling has been performed of the fluid dynamics in a prototypical physical vapor transport crystal growing situation. Cases with and without gravity have been computed. Dependence of the flows upon the dimensionless parameters aspect ratio and Peclet, Rayleigh, and Schmidt numbers is demonstrated to a greater extent than in previous works. Most notably, it is shown that the effects of thermally-induced buoyant convection upon the mass flux on the growth interface crucially depend upon the temperature boundary conditions on the sidewall (e.g., whether adiabatic or of a fixed profile, and in the latter case the results depend upon the shape of the profile assumed).

Energy balance in high-quality cutting of steel by fiber and CO2 lasers

NASA Astrophysics Data System (ADS)

Fomin, V. M.; Golyshev, A. A.; Orishich, A. M.; Shulyat'ev, V. B.

2017-03-01

The energy balance of laser cutting of low-carbon and stainless steel sheets with the minimum roughness of the cut surface is experimentally studied. Experimental data obtained in wide ranges of cutting parameters are generalized with the use of dimensionless parameters (Peclet number and absorbed laser energy). It is discovered for the first time that the minimum roughness is ensured at a certain value of energy per unit volume of the melt (approximately 26 J/mm3), regardless of the gas type (oxygen or nitrogen) and laser type (fiber laser with a wavelength of 1.07 μm or CO2 laser with a wavelength of 10.6 μm).

Tabulation and summary of thermodynamic effects data for developed cavitation on ogive-nosed bodies

NASA Technical Reports Server (NTRS)

Holl, J. W.; Billet, M. L.; Weir, D. S.

1978-01-01

Thermodynamic effects data for developed cavitation on zero and quarter caliber ogives in Freon 113 and water are tabulated and summarized. These data include temperature depression (delta T), flow coefficient (C sub Q), and various geometrical characteristics of the cavity. For the delta T tests, the free-stream temperature varied from 35 C to 95 C in Freon 113 and from 60 C to 125 C in water for a velocity range of 19.5 m/sec to 36.6 m/sec. Two correlations of the delta T data by the entrainment method are presented. These correlations involve different combinations of the Nusselt, Reynolds, Froude, Weber, and Peclet numbers and dimensionless cavity length.

Active ideal sedimentation: exact two-dimensional steady states.

PubMed

Hermann, Sophie; Schmidt, Matthias

2018-02-28

We consider an ideal gas of active Brownian particles that undergo self-propelled motion and both translational and rotational diffusion under the influence of gravity. We solve analytically the corresponding Smoluchowski equation in two space dimensions for steady states. The resulting one-body density is given as a series, where each term is a product of an orientation-dependent Mathieu function and a height-dependent exponential. A lower hard wall is implemented as a no-flux boundary condition. Numerical evaluation of the suitably truncated analytical solution shows the formation of two different spatial regimes upon increasing Peclet number. These regimes differ in their mean particle orientation and in their variation of the orientation-averaged density with height.

Influence of Brownian Motion on Blood Platelet Flow Behavior and Adhesive Dynamics near a Planar Wall

PubMed Central

Mody, Nipa A.; King, Michael R.

2008-01-01

We used the Platelet Adhesive Dynamics computational method to study the influence of Brownian motion of a platelet on its flow characteristics near a surface in the creeping flow regime. Two important characterizations were done in this regard: (1) quantification of the platelet’s ability to contact the surface by virtue of the Brownian forces and torques acting on it, and (2) determination of the relative importance of Brownian motion in promoting surface encounters in the presence of shear flow. We determined the Peclet number for a platelet undergoing Brownian motion in shear flow, which could be expressed as a simple linear function of height of the platelet centroid, H from the surface Pe (platelet) = γ. · (1.56H + 0.66) for H > 0.3 μm. Our results demonstrate that at timescales relevant to shear flow in blood, Brownian motion plays an insignificant role in influencing platelet motion or creating further opportunities for platelet-surface contact. The platelet Peclet number at shear rates > 100 s-1 is large enough (> 200) to neglect platelet Brownian motion in computational modeling of flow in arteries and arterioles for most practical purposes even at very close distances from the surface. We also conducted adhesive dynamics simulations to determine the effects of platelet Brownian motion on GPIbα-vWF-A1 single-bond dissociation dynamics. Brownian motion was found to have little effect on bond lifetime and caused minimal bond stressing as bond rupture forces were calculated to be less than 0.005 pN. We conclude from our results that for the case of platelet-shaped cells, Brownian motion is not expected to play an important role in influencing flow characteristics, platelet-surface contact frequency and dissociative binding phenomena under flow at physiological shear rates (> 50 s-1). PMID:17417890

On N. Park's Analytical solution for steady state density- and mixing regime—dependent solute transport in a vertical soil column

NASA Astrophysics Data System (ADS)

Thiele, Michael

1998-04-01

Recently, Park [1996] presented an analytical solution for stationary one-dimensional solute transport in a variable-density fluid flow through a vertical soil column. He used the widespread Bear-Scheidegger dispersion model describing solute mixing as a sum of molecular diffusion and velocity-proportional mechanical dispersion effects. His closed-form implicit concentration and pressure distributions thus allow for a discussion of the combined impact of molecular diffusion and mechanical dispersion in a variable-density environment. Whereas Park only considered the example of vanishing molecular diffusion in detail, both phenomena are taken into account simultaneously in the present study in order to elucidate their different influences on concentration distribution characteristics. The boundary value problem dealt with herein is based on an upward inflow of high-density fluid of constant solute concentration and corresponding outflow of a lower constant concentration fluid at the upper end of the column when dispersivity does not change along the flow path. The thickness of the transition zone between the two fluids appeared to strongly depend on the prevailing share of the molecular diffusion and mechanical dispersion mechanisms. The latter can be characterized by a molecular Peclet number Pe, which here is defined as the ratio of the column outflow velocity multiplied by a characteristic pore size and the molecular diffusion coefficient. For very small values of Pe, when molecular diffusion represents the exclusive mixing process, density differences have no impact on transition zone thicknesses. A relative density-;dependent thickness increases with flow velocities (increasing Pe values) very rapidly compared to the density-independent case, and after having passed a maximum decreases asymptotically to a constant value for the large Peclet number limit when mechanical dispersion is the only mixing mechanism. Hence the special transport problem analyzed gives further evidence for the importance of simultaneously considering molecular diffusion and mechanical dispersion in gravity-affected solute transport in porous media.

Percolation characteristics of solvent invasion in rough fractures under miscible conditions

NASA Astrophysics Data System (ADS)

Korfanta, M.; Babadagli, T.; Develi, K.

2017-10-01

Surface roughness and flow rate effects on the solvent transport under miscible conditions in a single fracture are studied. Surface replicas of seven different rocks (marble, granite, and limestone) are used to represent different surface roughness characteristics each described by different mathematical models including three fractal dimensions. Distribution of dyed solvent is investigated at various flow rate conditions to clarify the effect of roughness on convective and diffusive mixing. After a qualitative analysis using comparative images of different rocks, the area covered by solvent with respect to time is determined to conduct a semi-quantitative analysis. In this exercise, two distinct zones are identified, namely the straight lines obtained for convective (early times) and diffusive (late times) flow. The bending point between these two lines is used to point the transition between the two zones. Finally, the slopes of the straight lines and the bending points are correlated to five different roughness parameters and the rate (Peclet number). It is observed that both surface roughness and flow rate have significant effect on solvent spatial distribution. The largest area covered is obtained at moderate flow rates and hence not only the average surface roughness characteristic is important, but coessentially total fracture surface area needs to be considered when evaluating fluid distribution. It is also noted that the rate effect is critically different for the fracture samples of large grain size (marbles and granite) compared to smaller grain sizes (limestones). Variogram fractal dimension exhibits the strongest correlation with the maximum area covered by solvent, and display increasing trend at the moderate flow rates. Equations with variogram surface fractal dimension in combination with any other surface fractal parameter coupled with Peclet number can be used to predict maximum area covered by solvent in a single fracture, which in turn can be utilized to model oil recovery, waste disposal, and groundwater contamination processes in the presence of fractures.

Scalar entrainment in the mixing layer

NASA Technical Reports Server (NTRS)

Sandham, N. D.; Mungal, M. G.; Broadwell, J. E.; Reynolds, W. C.

1988-01-01

New definitions of entrainment and mixing based on the passive scalar field in the plane mixing layer are proposed. The definitions distinguish clearly between three fluid states: (1) unmixed fluid, (2) fluid engulfed in the mixing layer, trapped between two scalar contours, and (3) mixed fluid. The difference betwen (2) and (3) is the amount of fluid which has been engulfed during the pairing process, but has not yet mixed. Trends are identified from direct numerical simulations and extensions to high Reynolds number mixing layers are made in terms of the Broadwell-Breidenthal mixing model. In the limit of high Peclet number (Pe = ReSc) it is speculated that engulfed fluid rises in steps associated with pairings, introducing unmixed fluid into the large scale structures, where it is eventually mixed at the Kolmogorov scale. From this viewpoint, pairing is a prerequisite for mixing in the turbulent plane mixing layer.

Simulating anomalous transport and multiphase segregation in porous media with the Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Matin, Rastin; Hernandez, Anier; Misztal, Marek; Mathiesen, Joachim

2015-04-01

Many hydrodynamic phenomena ranging from flows at micron scale in porous media, large Reynolds numbers flows, non-Newtonian and multiphase flows have been simulated on computers using the lattice Boltzmann (LB) method. By solving the Lattice Boltzmann Equation on unstructured meshes in three dimensions, we have developed methods to efficiently model the fluid flow in real rock samples. We use this model to study the spatio-temporal statistics of the velocity field inside three-dimensional real geometries and investigate its relation to the, in general, anomalous transport of passive tracers for a wide range of Peclet and Reynolds numbers. We extend this model by free-energy based method, which allows us to simulate binary systems with large-density ratios in a thermodynamically consistent way and track the interface explicitly. In this presentation we will present our recent results on both anomalous transport and multiphase segregation.

Convective overshoot at the solar tachocline

NASA Astrophysics Data System (ADS)

Brown, Benjamin; Oishi, Jeffrey S.; Anders, Evan H.; Lecoanet, Daniel; Burns, Keaton; Vasil, Geoffrey M.

2017-08-01

At the base of the solar convection zone lies the solar tachocline. This internal interface is where motions from the unstable convection zone above overshoot and penetrate downward into the stiffly stable radiative zone below, driving gravity waves, mixing, and possibly pumping and storing magnetic fields. Here we study the dynamics of convective overshoot across very stiff interfaces with some properties similar to the internal boundary layer within the Sun. We use the Dedalus pseudospectral framework and study fully compressible dynamics at moderate to high Peclet number and low Mach number, probing a regime where turbulent transport is important, and where the compressible dynamics are similar to those of convective motions in the deep solar interior. We find that the depth of convective overshoot is well described by a simple buoyancy equilibration model, and we consider implications for dynamics at the solar tachocline and for the storage of magnetic fields there by overshooting convection.

Morphological instability of a thermophoretically growing deposit

NASA Technical Reports Server (NTRS)

Castillo, Jose L.; Garcia-Ybarra, Pedro L.; Rosner, Daniel E.

1992-01-01

The stability of the planar interface of a structureless solid growing from a depositing component dilute in a carrier fluid is studied when the main solute transport mechanism is thermal (Soret) diffusion. A linear stability analysis, carried out in the limit of low growth Peclet number, leads to a dispersion relation which shows that the planar front is unstable either when the thermal diffusion factor of the condensing component is positive and the latent heat release is small or when the thermal diffusion factor is negative and the solid grows over a thermally-insulating substrate. Furthermore, the influence of interfacial energy effects and constitutional supersaturation in the vicinity of the moving interface is analyzed in the limit of very small Schmidt numbers (small solute Fickian diffusion). The analysis is relevant to physical vapor deposition of very massive species on cold surfaces, as in recent experiments of organic solid film growth under microgravity conditions.

Convection in an ideal gas at high Rayleigh numbers.

PubMed

Tilgner, A

2011-08-01

Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries.

Mixed Convection Opposing Flow in a Vertical Porous Annulus-Two Temperature Model

NASA Astrophysics Data System (ADS)

Al-Rashed, Abdullah A. AA; J, Salman Ahmed N.; Khaleed, H. M. T.; Yunus Khan, T. M.; NazimAhamed, K. S.

2016-09-01

The opposing flow in a porous medium refers to a condition when the forcing velocity flows in opposite direction to thermal buoyancy obstructing the buoyant force. The present research refers to the effect of opposing flow in a vertical porous annulus embedded with fluid saturated porous medium. The thermal non-equilibrium approach with Darcy modal is considered. The boundary conditions are such that the inner radius is heated with constant temperature Tw the outer radius is maintained at constant temperature Tc. The coupled nonlinear partial differential equations such as momentum equation, energy equation for fluid and energy equation for solid are solved using the finite element method. The opposing flow variation of average Nusselt number with respect to radius ratio Rr, Aspect ratioAr and Radiation parameter Rd for different values of Peclet number Pe are investigated. It is found that the flow behavior is quite different from that of aiding flow.

A numerical treatment of radiative nanofluid 3D flow containing gyrotactic microorganism with anisotropic slip, binary chemical reaction and activation energy.

PubMed

Lu, Dianchen; Ramzan, M; Ullah, Naeem; Chung, Jae Dong; Farooq, Umer

2017-12-05

A numerical investigation of steady three dimensional nanofluid flow carrying effects of gyrotactic microorganism with anisotropic slip condition along a moving plate near a stagnation point is conducted. Additionally, influences of Arrhenius activation energy, joule heating accompanying binary chemical reaction and viscous dissipation are also taken into account. A system of nonlinear differential equations obtained from boundary layer partial differential equations is found by utilization of apposite transformations. RK fourth and fifth order technique of Maple software is engaged to acquire the solution of the mathematical model governing the presented fluid flow. A Comparison with previously done study is also made and a good agreement is achieved with existing results; hence reliable results are being presented. Evaluations are carried out for involved parameters graphically against velocity, temperature, concentration fields, microorganism distribution, density number, local Nusselt and Sherwood numbers. It is detected that microorganism distribution exhibit diminishing behavior for rising values of bio-convection Lewis and Peclet numbers.

Dimensionless numbers in additive manufacturing

NASA Astrophysics Data System (ADS)

Mukherjee, T.; Manvatkar, V.; De, A.; DebRoy, T.

2017-02-01

The effects of many process variables and alloy properties on the structure and properties of additively manufactured parts are examined using four dimensionless numbers. The structure and properties of components made from 316 Stainless steel, Ti-6Al-4V, and Inconel 718 powders for various dimensionless heat inputs, Peclet numbers, Marangoni numbers, and Fourier numbers are studied. Temperature fields, cooling rates, solidification parameters, lack of fusion defects, and thermal strains are examined using a well-tested three-dimensional transient heat transfer and fluid flow model. The results show that lack of fusion defects in the fabricated parts can be minimized by strengthening interlayer bonding using high values of dimensionless heat input. The formation of harmful intermetallics such as laves phases in Inconel 718 can be suppressed using low heat input that results in a small molten pool, a steep temperature gradient, and a fast cooling rate. Improved interlayer bonding can be achieved at high Marangoni numbers, which results in vigorous circulation of liquid metal, larger pool dimensions, and greater depth of penetration. A high Fourier number ensures rapid cooling, low thermal distortion, and a high ratio of temperature gradient to the solidification growth rate with a greater tendency of plane front solidification.

AC electroosmotic micromixer for chemical processing in a microchannel.

PubMed

Sasaki, Naoki; Kitamori, Takehiko; Kim, Haeng-Boo

2006-04-01

A rapid micromixer of fluids in a microchannel is presented. The mixer uses AC electroosmotic flow, which is induced by applying an AC voltage to a pair of coplanar meandering electrodes configured in parallel to the channel. To demonstrate performance of the mixer, dilution experiments were conducted using a dye solution in a channel of 120 microm width. Rapid mixing was observed for flow velocity up to 12 mm s(-1). The mixing time was 0.18 s, which was 20-fold faster than that of diffusional mixing without an additional mixing mechanism. Compared with the performance of reported micromixers, the present mixer worked with a shorter mixing length, particularly at low Peclet numbers (Pe < 2 x 10(3)).

Hydroliquefaction of coal

DOEpatents

Sze, Morgan C.; Schindler, Harvey D.

1982-01-01

Coal is catalytically hydroliquefied by passing coal dispersed in a liquefaction solvent and hydrogen upwardly through a plurality of parallel expanded catalyst beds, in a single reactor, in separate streams, each having a cross-sectional flow area of no greater than 255 inches square, with each of the streams through each of the catalyst beds having a length and a liquid and gas superficial velocity to maintain an expanded catalyst bed and provide a Peclet Number of at least 3. If recycle is employed, the ratio of recycle to total feed (coal and liquefaction solvent) is no greater than 2:1, based on volume. Such conditions provide for improved selectivity to liquid product to thereby reduce hydrogen consumption. The plurality of beds are formed by partitions in the reactor.

Effective Stochastic Model for Reactive Transport

NASA Astrophysics Data System (ADS)

Tartakovsky, A. M.; Zheng, B.; Barajas-Solano, D. A.

2017-12-01

We propose an effective stochastic advection-diffusion-reaction (SADR) model. Unlike traditional advection-dispersion-reaction models, the SADR model describes mechanical and diffusive mixing as two separate processes. In the SADR model, the mechanical mixing is driven by random advective velocity with the variance given by the coefficient of mechanical dispersion. The diffusive mixing is modeled as a fickian diffusion with the effective diffusion coefficient. Both coefficients are given in terms of Peclet number (Pe) and the coefficient of molecular diffusion. We use the experimental results of to demonstrate that for transport and bimolecular reactions in porous media the SADR model is significantly more accurate than the traditional dispersion model, which overestimates the mass of the reaction product by as much as 25%.

Effect of nanofluid concentration on two-phase thermosyphon heat exchanger performance

NASA Astrophysics Data System (ADS)

Cieśliński, Janusz T.

2016-06-01

An approach - relaying on application of nanofluid as a working fluid, to improve performance of the two-phase thermosyphon heat exchanger (TPTHEx) has been proposed. The prototype heat exchanger consists of two horizontal cylindrical vessels connected by two risers and a downcomer. Tube bundles placed in the lower and upper cylinders work as an evaporator and a condenser, respectively. Distilled water and nanofluid water-Al2O3 solution were used as working fluids. Nanoparticles were tested at the concentration of 0.01% and 0.1% by weight. A modified Peclet equation and Wilson method were used to estimate the overall heat transfer coefficient of the tested TPTHEx. The obtained results indicate better performance of the TPTHEx with nanofluids as working fluid compared to distilled water, independent of nanoparticle concentration tested. However, increase in nanoparticle concentration results in overall heat transfer coefficient decrease of the TPTHEx examined. It has been observed that, independent of nanoparticle concentration tested, decrease in operating pressure results in evaporation heat transfer coefficient increase.

Local structure of scalar flux in turbulent passive scalar mixing

NASA Astrophysics Data System (ADS)

Konduri, Aditya; Donzis, Diego

2012-11-01

Understanding the properties of scalar flux is important in the study of turbulent mixing. Classical theories suggest that it mainly depends on the large scale structures in the flow. Recent studies suggest that the mean scalar flux reaches an asymptotic value at high Peclet numbers, independent of molecular transport properties of the fluid. A large DNS database of isotropic turbulence with passive scalars forced with a mean scalar gradient with resolution up to 40963, is used to explore the structure of scalar flux based on the local topology of the flow. It is found that regions of small velocity gradients, where dissipation and enstrophy are small, constitute the main contribution to scalar flux. On the other hand, regions of very small scalar gradient (and scalar dissipation) become less important to the scalar flux at high Reynolds numbers. The scaling of the scalar flux spectra is also investigated. The k - 7 / 3 scaling proposed by Lumley (1964) is observed at high Reynolds numbers, but collapse is not complete. A spectral bump similar to that in the velocity spectrum is observed close to dissipative scales. A number of features, including the height of the bump, appear to reach an asymptotic value at high Schmidt number.

Studies in nonlinear problems of energy. Progress report, October 1, 1993--September 30, 1994

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

Matkowsky, B.J.

1994-09-01

The authors concentrate on modeling, analysis and large scale scientific computation of combustion and flame propagation phenomena, with emphasis on the transition from laminar to turbulent combustion. In the transition process a flame passed through a stages exhibiting increasingly complex spatial and temporal patterns which serve as signatures identifying each stage. Often the transitions arise via bifurcation. The authors investigate nonlinear dynamics, bifurcation and pattern formation in the successive stage of transition. They describe the stability of combustion waves, and transitions to combustion waves exhibiting progressively higher degrees of spatio-temporal complexity. One aspect of this research program is the systematicmore » derivation of appropriate, approximate models from the original models governing combustion. The approximate models are then analyzed. The authors are particularly interested in understanding the basic mechanisms affecting combustion, which is a prerequisite to effective control of the process. They are interested in determining the effects of varying various control parameters, such as Nusselt number, Lewis number, heat release, activation energy, Damkohler number, Reynolds number, Prandtl number, Peclet number, etc. The authors have also considered a number of problems in self-propagating high-temperature synthesis (SHS), in which combustion waves are employed to synthesize advanced materials. Efforts are directed toward understanding fundamental mechanisms. 167 refs.« less

An analysis of a mixed convection associated with thermal heating in contaminated porous media.

PubMed

Krol, Magdalena M; Johnson, Richard L; Sleep, Brent E

2014-11-15

The occurrence of subsurface buoyant flow during thermal remediation was investigated using a two dimensional electro-thermal model (ETM). The model incorporated electrical current flow associated with electrical resistance heating, energy and mass transport, and density dependent water flow. The model was used to examine the effects of heating on sixteen subsurface scenarios with different applied groundwater fluxes and soil permeabilities. The results were analyzed in terms of the ratio of Rayleigh to thermal Peclet numbers (the buoyancy ratio). It was found that when the buoyancy number was greater than unity and the soil permeability greater than 10(-12) m(2), buoyant flow and contaminant transport were significant. The effects of low permeability layers and electrode placement on heat and mass transport were also investigated. Heating under a clay layer led to flow stagnation zones resulting in the accumulation of contaminant mass and transport into the low permeability layer. The results of this study can be used to develop dimensionless number-based guidelines for site management during subsurface thermal activities. Copyright © 2014 Elsevier B.V. All rights reserved.

Stellar Mixing: I. Formalism

NASA Technical Reports Server (NTRS)

Canuto, V .M.

2011-01-01

In this paper we use the Reynolds stress models (RSM) to derive algebraic expressions for the following variables: a) heat fluxes; b) J.l fluxes; and c) momentum fluxes. These relations, which are fully 3D, include: 1) stable and unstable stratification, represented by the Brunt-Vaislila frequency, N(exp 2) =-g/H(sub p_(del - del(sub ad))(1 - RI(sub mu)); 2) double diffusion, salt-fingers, and semi-convection, represented by the density ratio R(sub mu) = del(sub mu)/(del - del(sub ad)); 3) shear (differential rotation), represented by the mean squared shear Sigma(exp 2) or by the Richardson number, Ri =N(exp 2)Sigma(exp -2); 4) radiative losses represented by a Peclet number, Pe; 5) a complete analytical solution of the ID version of the model. In general, the model requires the solution of two differential equations for the eddy kinetic energy K and its rate of dissipation, epsilon. In the local and stationary cases, when production equals dissipation, the model equations are all algebraic.

Richtmyer-Meshkov instability in shock-flame interactions

NASA Astrophysics Data System (ADS)

Massa, Luca; Pallav Jha Collaboration

2011-11-01

Shock-flame interactions occur in supersonic mixing and detonation formation. Therefore, their analysis is important to explosion safety, internal combustion engine performance, and supersonic combustor design. The fundamental process at the basis of the interaction is the Richtmyer-Meshkov instability supported by the density difference between burnt and fresh mixtures. In the present study we analyze the effect of reactivity on the Richtmyer- Meshkov instability with particular emphasis on combustion lengths that typify the scaling between perturbation growth and induction. The results of the present linear analysis study show that reactivity changes the perturbation growth rate by developing a non-zero pressure gradient at the flame surface. The baroclinic torque based on the density gradient across the flame acts to slow down the instability growth for high wave numbers. A non-hydrodynamic flame representation leads to the definition of an additional scaling Peclet number, the effects of which are investigated. It is found that an increased flame-contact separation destabilizes the contact discontinuity by augmenting the tangential shear.

Chemical Transport in a Fissured Rock: Verification of a Numerical Model

NASA Astrophysics Data System (ADS)

Rasmuson, A.; Narasimhan, T. N.; Neretnieks, I.

1982-10-01

Numerical models for simulating chemical transport in fissured rocks constitute powerful tools for evaluating the acceptability of geological nuclear waste repositories. Due to the very long-term, high toxicity of some nuclear waste products, the models are required to predict, in certain cases, the spatial and temporal distribution of chemical concentration less than 0.001% of the concentration released from the repository. Whether numerical models can provide such accuracies is a major question addressed in the present work. To this end we have verified a numerical model, TRUMP, which solves the advective diffusion equation in general three dimensions, with or without decay and source terms. The method is based on an integrated finite difference approach. The model was verified against known analytic solution of the one-dimensional advection-diffusion problem, as well as the problem of advection-diffusion in a system of parallel fractures separated by spherical particles. The studies show that as long as the magnitude of advectance is equal to or less than that of conductance for the closed surface bounding any volume element in the region (that is, numerical Peclet number <2), the numerical method can indeed match the analytic solution within errors of ±10-3% or less. The realistic input parameters used in the sample calculations suggest that such a range of Peclet numbers is indeed likely to characterize deep groundwater systems in granitic and ancient argillaceous systems. Thus TRUMP in its present form does provide a viable tool for use in nuclear waste evaluation studies. A sensitivity analysis based on the analytic solution suggests that the errors in prediction introduced due to uncertainties in input parameters are likely to be larger than the computational inaccuracies introduced by the numerical model. Currently, a disadvantage in the TRUMP model is that the iterative method of solving the set of simultaneous equations is rather slow when time constants vary widely over the flow region. Although the iterative solution may be very desirable for large three-dimensional problems in order to minimize computer storage, it seems desirable to use a direct solver technique in conjunction with the mixed explicit-implicit approach whenever possible. Work in this direction is in progress.

Nonlinear Response of Layer Growth Dynamics in the Mixed Kinetics-Bulk-Transport Regime

NASA Technical Reports Server (NTRS)

Vekilov, Peter G.; Alexander, J. Iwan D.; Rosenberger, Franz

1996-01-01

In situ high-resolution interferometry on horizontal facets of the protein lysozyme reveal that the local growth rate R, vicinal slope p, and tangential (step) velocity v fluctuate by up to 80% of their average values. The time scale of these fluctuations, which occur under steady bulk transport conditions through the formation and decay of step bunches (macrosteps), is of the order of 10 min. The fluctuation amplitude of R increases with growth rate (supersaturation) and crystal size, while the amplitude of the v and p fluctuations changes relatively little. Based on a stability analysis for equidistant step trains in the mixed transport-interface-kinetics regime, we argue that the fluctuations originate from the coupling of bulk transport with nonlinear interface kinetics. Furthermore, step bunches moving across the interface in the direction of or opposite to the buoyancy-driven convective flow increase or decrease in height, respectively. This is in agreement with analytical treatments of the interaction of moving steps with solution flow. Major excursions in growth rate are associated with the formation of lattice defects (striations). We show that, in general, the system-dependent kinetic Peclet number, Pe(sub k) , i.e., the relative weight of bulk transport and interface kinetics in the control of the growth process, governs the step bunching dynamics. Since Pe(sub k) can be modified by either forced solution flow or suppression of buoyancy-driven convection under reduced gravity, this model provides a rationale for the choice of specific transport conditions to minimize the formation of compositional inhomogeneities under steady bulk nutrient crystallization conditions.

Remediation of saturated soil contaminated with petroleum products using air sparging with thermal enhancement.

PubMed

Mohamed, A M I; El-menshawy, Nabil; Saif, Amany M

2007-05-01

Pollutants in the form of non-aqueous phase liquids (NAPLs), such as petroleum products, pose a serious threat to the soil and groundwater. A mathematical model was derived to study the unsteady pollutant concentrations through water saturated contaminated soil under air sparging conditions for different NAPLs and soil properties. The comparison between the numerical model results and the published experimental results showed acceptable agreement. Furthermore, an experimental study was conducted to remove NAPLs from the contaminated soil using the sparging air technique, considering the sparging air velocity, air temperature, soil grain size and different contaminant properties. This study showed that sparging air at ambient temperature through the contaminated soil can remove NAPLs, however, employing hot air sparging can provide higher contaminant removal efficiency, by about 9%. An empirical correlation for the volatilization mass transfer coefficient was developed from the experimental results. The dimensionless numbers used were Sherwood number (Sh), Peclet number (Pe), Schmidt number (Sc) and several physical-chemical properties of VOCs and porous media. Finally, the estimated volatilization mass transfer coefficient was used for calculation of the influence of heated sparging air on the spreading of the NAPL plume through the contaminated soil.

Energetics of the multi-phase fluid flow in a narrow kerf in laser cutting conditions

NASA Astrophysics Data System (ADS)

Golyshev, A. A.; Orishich, A. M.; Shulyatyev, V. B.

2016-10-01

The energy balance of the multi-phase medium flow is studied experimentally under the laser cutting. Experimental data are generalized due to the condition of minimal roughness of the created surface used as a quality criterion of the melt flow, and also due to the application of dimensionless parameters: Peclet number and dimensionless absorbed laser power. For the first time ever it is found that, regardless the assistant gas (oxygen or nitrogen), laser type (the fiber one with the wavelength of 1.07 µm or CO2-laser with the wavelength of 10.6 µm), the minimal roughness is provided at a certain energy input in a melt unit, about 26 J/mm3. With oxygen, 50% of this input is provided by the radiation, the other 50% - by the exothermic reaction of iron oxidation.

Screening for heat transport by groundwater in closed geothermal systems.

PubMed

Ferguson, Grant

2015-01-01

Heat transfer due to groundwater flow can significantly affect closed geothermal systems. Here, a screening method is developed, based on Peclet numbers for these systems and Darcy's law. Conduction-only conditions should not be expected where specific discharges exceed 10(-8)  m/s. Constraints on hydraulic gradients allow for preliminary screening for advection based on rock or soil types. Identification of materials with very low hydraulic conductivity, such as shale and intact igneous and metamorphic rock, allow for analysis with considering conduction only. Variability in known hydraulic conductivity allows for the possibility of advection in most other rocks and soil types. Further screening relies on refinement of estimates of hydraulic gradients and hydraulic conductivity through site investigations and modeling until the presence or absence of conduction can be confirmed. © 2014, National Ground Water Association.

Analytical method for optimal source reduction with monitored natural attenuation in contaminated aquifers

USGS Publications Warehouse

Widdowson, M.A.; Chapelle, F.H.; Brauner, J.S.; ,

2003-01-01

A method is developed for optimizing monitored natural attenuation (MNA) and the reduction in the aqueous source zone concentration (??C) required to meet a site-specific regulatory target concentration. The mathematical model consists of two one-dimensional equations of mass balance for the aqueous phase contaminant, to coincide with up to two distinct zones of transformation, and appropriate boundary and intermediate conditions. The solution is written in terms of zone-dependent Peclet and Damko??hler numbers. The model is illustrated at a chlorinated solvent site where MNA was implemented following source treatment using in-situ chemical oxidation. The results demonstrate that by not taking into account a variable natural attenuation capacity (NAC), a lower target ??C is predicted, resulting in unnecessary source concentration reduction and cost with little benefit to achieving site-specific remediation goals.

Bioturbation, advection, and diffusion of a conserved tracer in a laboratory flume

NASA Astrophysics Data System (ADS)

Work, P. A.; Moore, P. R.; Reible, D. D.

2002-06-01

Laboratory experiments indicating the relative influences of advection, diffusion, and bioturbation on transport of NaCl tracer between a stream and streambed are described. Data were collected in a recirculating flume housing a box filled with test sediments. Peclet numbers ranged from 0 to 1.5. Sediment components included a medium sand (d50 = 0.31 mm), kaolinite, and topsoil. Lumbriculus variegatus were introduced as bioturbators. Conductivity probes were employed to document the flux of the tracer solution out of the bed. Measurements are compared to one-dimensional effective diffusion models assuming one or two horizontal sediment layers. These simple models provide a good indication of tracer half-life in the bed if a suitable effective diffusion coefficient is chosen but underpredict initial flux and overpredict flux at long times. Organism activity was limited to the upper reaches of the sediment test box but eventually exerts a secondary influence on flux from deeper regions.

Mass transfer from an oscillating microsphere.

PubMed

Zhu, Jiahua; Zheng, Feng; Laucks, Mary L; Davis, E James

2002-05-15

The enhancement of mass transfer from single oscillating aerocolloidal droplets having initial diameters approximately 40 microm has been measured using electrodynamic levitation to trap and oscillate a droplet evaporating in nitrogen gas. The frequency and amplitude of the oscillation were controlled by means of ac and dc fields applied to the ring electrodes of the electrodynamic balance (EDB). Elastic light scattering was used to size the droplet. It is shown that the mass transfer process for a colloidal or aerocolloidal particle oscillating in the Stokes flow regime is governed by a Peclet number for oscillation and a dimensionless oscillation parameter that represents the ratio of the diffusion time scale to the oscillation time scale. Evaporation rates are reported for stably oscillating droplets that are as much as five times the rate for evaporation in a stagnant gas. The enhancement is substantially larger than that predicted by quasi-steady-flow mass transfer.

[Roles of additives and surface control in slurry atomization]. Quarterly report, March 1992

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

Not Available

1992-08-01

Our experimental results clearly demonstrate that the shape of particles with aspect ratio close to unity dictates the relative suspension viscosity. Suspensions of irregularly shaped particles have higher relative viscosities than suspensions of spherical particles at same volume fractions, in agreement with the reported results at high shear conditions. The relative viscosity of a Newtonian suspension is in excellent agreement with that predicted by the Krieger/Dougherty rigid sphere model using the maximum packing fraction determined from sedimentation as the sole parameter. The relative viscosity of a pseudoplastic suspension is independent of the particle density. It correlates well with the particlemore » Peclet number. The extent of particle diffusion at high shear rates decreases considerably as the particle size increases, and less energy is dissipated as a result. The interparticle electrostatic repulsion plays no significant role in the rheology of pseudoplastic nonaqueous and aqueous glycerol suspensions of noncolloidal particles.« less

(Roles of additives and surface control in slurry atomization)

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

Not Available

1992-01-01

Our experimental results clearly demonstrate that the shape of particles with aspect ratio close to unity dictates the relative suspension viscosity. Suspensions of irregularly shaped particles have higher relative viscosities than suspensions of spherical particles at same volume fractions, in agreement with the reported results at high shear conditions. The relative viscosity of a Newtonian suspension is in excellent agreement with that predicted by the Krieger/Dougherty rigid sphere model using the maximum packing fraction determined from sedimentation as the sole parameter. The relative viscosity of a pseudoplastic suspension is independent of the particle density. It correlates well with the particlemore » Peclet number. The extent of particle diffusion at high shear rates decreases considerably as the particle size increases, and less energy is dissipated as a result. The interparticle electrostatic repulsion plays no significant role in the rheology of pseudoplastic nonaqueous and aqueous glycerol suspensions of noncolloidal particles.« less

Numerical investigation on layout optimization of obstacles in a three-dimensional passive micromixer.

PubMed

Chen, Xueye; Zhao, Zhongyi

2017-04-29

This paper aims at layout optimization design of obstacles in a three-dimensional T-type micromixer. Numerical analysis shows that the direction of flow velocity change constantly due to the obstacles blocking, which produces the chaotic convection and increases species mixing effectively. The orthogonal experiment method was applied for determining the effects of some key parameters on mixing efficiency. The weights in the order are: height of obstacles > geometric shape > symmetry = number of obstacles. Based on the optimized results, a multi-units obstacle micromixer was designed. Compared with T-type micromixer, the multi-units obstacle micromixer is more efficient, and more than 90% mixing efficiency were obtained for a wide range of peclet numbers. It can be demonstrated that the presented optimal design method of obstacles layout in three-dimensional microchannels is a simple and effective technology to improve species mixing in microfluidic devices. The obstacles layout methodology has the potential for applications in chemical engineering and bioengineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of holdup and axial dispersion of liquid phase in a catalytic exchange column using radiotracer technique.

PubMed

Kumar, Rajesh; Pant, H J; Goswami, Sunil; Sharma, V K; Dash, A; Mishra, S; Bhanja, K; Mohan, Sadhana; Mahajani, S M

2017-03-01

Holdup and axial dispersion of liquid phase in a catalytic exchange column were investigated by measuring residence time distributions (RTD) using a radiotracer technique. RTD experiments were independently carried out with two different types of packings i.e. hydrophobic water-repellent supported platinum catalyst and a mixture (50% (v/v)) of hydrophobic catalyst and a hydrophillic wettable packing were used in the column. Mean residence times and hold-ups of the liquid phase were estimated at different operating conditions. Axial dispersion model (ADM) and axial dispersion with exchange model (ADEM) were used to simulate the measured RTD data. Both the models were found equally suitable to describe the measured data. The degree of axial mixing was estimated in terms of Peclet number (Pe) and Bodenstein number (Bo). Based on the obtained parameters of the ADM, correlations for total liquid hold-up (H T ) and axial mixing in terms of Bo were proposed for design and scale up of the full-scale catalytic exchange column. Copyright © 2016 Elsevier Ltd. All rights reserved.

The formation of spikes in the displacement of miscible fluids

NASA Technical Reports Server (NTRS)

Rashidnia, N.; Balasubramaniam, R.; Schroer, R. T.

2004-01-01

We report on experiments in which a more viscous fluid displaces a less viscous one in a vertical cylindrical tube. These experiments were performed using silicone oils in a vertical pipette of small diameter. The more viscous fluid also had a slightly larger density than the less viscous fluid. In the initial configuration, the fluids were at rest, and the interface was nominally flat. A dye was added to the more viscous fluid for ease of observation of the interface between the fluids. The flow was initiated by pumping the more viscous fluid into the less viscous one. The displacement velocity was such that the Reynolds number was smaller than unity and the Peclet number for mass transfer between the fluids was large compared to unity. For upward displacement of the more viscous fluid from an initially stable configuration, an axisymmetric finger was observed under all conditions. However, a needle-shaped spike was seen to propagate from the main finger in many cases, similar to that observed by Petitjeans and Maxworthy for the displacement of a more viscous fluid by a less viscous one.

Higher order concentration moments collapse in the expected mass fraction (EMF) based risk assessment

NASA Astrophysics Data System (ADS)

Srzic, Veljko; Gotovac, Hrvoje; Cvetkovic, Vladimir; Andricevic, Roko

2014-05-01

In this work Langrangian framework is used for conservative tracer transport simulations through 2-D extremely heterogeneous porous media. Conducted numerical simulations enable large sets of concentration values in both spatial and temporal domains. In addition to the advection, which acts on all scales, an additional mechanism considered is local scale dispersion (LSD), accounting for both mechanical dispersion and molecular diffusion. The ratio between these two mechanisms is quantified by the Peclet (Pe) number. In its base, the work gives answers to concentration scalar features when influenced by: i) different log-conductivity variance; ii) log-conductivity structures defined by the same global variogram but with different log conductivity patterns correlated; and iii) for a wide range of Peclet values. Results conducted by Monte Carlo analysis show a complex interplay between the aforementioned parameters, indicating the influence of aquifer properties to temporal LSD evolution. A remarkable collapse of higher order to second-order concentration moments [Yee, 2009] leads to the conclusion that only two concentration moments are required for an accurate description of concentration fluctuations. This explicitly holds for the pure advection case, while in the case of LSD presence the moment deriving function(MDF) is involved to ensure the moment collapse validity. An inspection of the Beta distribution leads to the conclusion that the two-parametric distribution can be used for concentration fluctuation characterization even in cases of high aquifer heterogeneity and/or for different log-conductivity structures, independent of the sampling volume used. Furthermore, the expected mass fraction (EMF) [Heagy & Sullivan, 1996] concept is applied in groundwater transport. In its origin, EMF is function of the concentration but with lower number of realizations needed for its determination, compared to the one point PDF. From practical point of view, EMF excludes meandering effect and incorporates information about exposure time for each non-zero concentration value present. Also, it is shown that EMF is able to clearly reflect the effects of aquifer heterogeneity and structure as well as the Pe value. The latter is demonstrated through the non-carcinogenic risk assessment framework. To demonstrate the uniqueness of the moment collapse feature and ability of the Beta distribution to account for the concentration frequencies even in real cases, Macrodispersion Experiment (MADE1) [Boggs et al, 1992] data sets are used for validation.

Chemical transport in a fissured rock: Verification of a numerical model

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

Rasmuson, A.; Narasimhan, T. N.; Neretnieks, I.

1982-10-01

Numerical models for simulating chemical transport in fissured rocks constitute powerful tools for evaluating the acceptability of geological nuclear waste repositories. Due to the very long-term, high toxicity of some nuclear waste products, the models are required to predict, in certain cases, the spatial and temporal distribution of chemical concentration less than 0.001% of the concentration released from the repository. Whether numerical models can provide such accuracies is a major question addressed in the present work. To this end, we have verified a numerical model, TRUMP, which solves the advective diffusion equation in general three dimensions with or without decaymore » and source terms. The method is based on an integrated finite-difference approach. The model was verified against known analytic solution of the one-dimensional advection-diffusion problem as well as the problem of advection-diffusion in a system of parallel fractures separated by spherical particles. The studies show that as long as the magnitude of advectance is equal to or less than that of conductance for the closed surface bounding any volume element in the region (that is, numerical Peclet number <2), the numerical method can indeed match the analytic solution within errors of ±10{sup -3} % or less. The realistic input parameters used in the sample calculations suggest that such a range of Peclet numbers is indeed likely to characterize deep groundwater systems in granitic and ancient argillaceous systems. Thus TRUMP in its present form does provide a viable tool for use in nuclear waste evaluation studies. A sensitivity analysis based on the analytic solution suggests that the errors in prediction introduced due to uncertainties in input parameters is likely to be larger than the computational inaccuracies introduced by the numerical model. Currently, a disadvantage in the TRUMP model is that the iterative method of solving the set of simultaneous equations is rather slow when time constants vary widely over the flow region. Although the iterative solution may be very desirable for large three-dimensional problems in order to minimize computer storage, it seems desirable to use a direct solver technique in conjunction with the mixed explicit-implicit approach whenever possible. work in this direction is in progress.« less

Experimental validation of convection-diffusion discretisation scheme employed for computational modelling of biological mass transport

PubMed Central

2010-01-01

Background The finite volume solver Fluent (Lebanon, NH, USA) is a computational fluid dynamics software employed to analyse biological mass-transport in the vasculature. A principal consideration for computational modelling of blood-side mass-transport is convection-diffusion discretisation scheme selection. Due to numerous discretisation schemes available when developing a mass-transport numerical model, the results obtained should either be validated against benchmark theoretical solutions or experimentally obtained results. Methods An idealised aneurysm model was selected for the experimental and computational mass-transport analysis of species concentration due to its well-defined recirculation region within the aneurysmal sac, allowing species concentration to vary slowly with time. The experimental results were obtained from fluid samples extracted from a glass aneurysm model, using the direct spectrophometric concentration measurement technique. The computational analysis was conducted using the four convection-diffusion discretisation schemes available to the Fluent user, including the First-Order Upwind, the Power Law, the Second-Order Upwind and the Quadratic Upstream Interpolation for Convective Kinetics (QUICK) schemes. The fluid has a diffusivity of 3.125 × 10-10 m2/s in water, resulting in a Peclet number of 2,560,000, indicating strongly convection-dominated flow. Results The discretisation scheme applied to the solution of the convection-diffusion equation, for blood-side mass-transport within the vasculature, has a significant influence on the resultant species concentration field. The First-Order Upwind and the Power Law schemes produce similar results. The Second-Order Upwind and QUICK schemes also correlate well but differ considerably from the concentration contour plots of the First-Order Upwind and Power Law schemes. The computational results were then compared to the experimental findings. An average error of 140% and 116% was demonstrated between the experimental results and those obtained from the First-Order Upwind and Power Law schemes, respectively. However, both the Second-Order upwind and QUICK schemes accurately predict species concentration under high Peclet number, convection-dominated flow conditions. Conclusion Convection-diffusion discretisation scheme selection has a strong influence on resultant species concentration fields, as determined by CFD. Furthermore, either the Second-Order or QUICK discretisation schemes should be implemented when numerically modelling convection-dominated mass-transport conditions. Finally, care should be taken not to utilize computationally inexpensive discretisation schemes at the cost of accuracy in resultant species concentration. PMID:20642816

Pulsatile Flow Across a Cylinder--An Investigation of Flow in a Total Artificial Lung

NASA Astrophysics Data System (ADS)

Lin, Yu-Chun

2005-11-01

The effect of pulsatility on flow across a single cylinder has been examined experimentally using particle image velocimetry. This work is motivated by the ongoing development of a total artificial lung (TAL), a device which would serve as a bridge to lung transplant. The prototype TAL consists of hollow microfibers through which oxygen-rich gas flows and blood flows around. Flow through the device is provided entirely by right heart and, therefore, is puslatile. The Peclet number of the flow is large and consequently the development of secondary flow affects the resulting gas exchange. The effects of frequency and average flow rate of pulsatile flow around a cylinder were investigated experimentally in a water tunnel and some of the results were compared with preliminary numerical results. Vortices developed behind the cylinder at lower Reynolds numbers in pulsatile flow than steady flow. The results indicate that there are critical values of the Reynolds number between 3 to 5 and Stokes numbers of 0.22, below which vortices were not observed. The findings suggest that higher Stokes and Reynolds numbers within the device could enhance vortex formation. However, this enhanced gas exchange could be at the expense of higher device resistance and increased likelihood of blood trauma. Intelligent TAL design will require consideration of these effects. This work is supported by NIH grant HL69420.

Towards the minimization of thermodynamic irreversibility in an electrically actuated microflow of a viscoelastic fluid under electrical double layer phenomenon

NASA Astrophysics Data System (ADS)

Sarma, Rajkumar; Jain, Manish; Mondal, Pranab Kumar

2017-10-01

We discuss the entropy generation minimization for electro-osmotic flow of a viscoelastic fluid through a parallel plate microchannel under the combined influences of interfacial slip and conjugate transport of heat. We use in this study the simplified Phan-Thien-Tanner model to describe the rheological behavior of the viscoelastic fluid. Using Navier's slip law and thermal boundary conditions of the third kind, we solve the transport equations analytically and evaluate the global entropy generation rate of the system. We examine the influential role of the following parameters on the entropy generation rate of the system, viz., the viscoelastic parameter (ɛDe2), Debye-Hückel parameter ( κ ¯ ) , channel wall thickness (δ), thermal conductivity of the wall (γ), Biot number (Bi), Peclet number (Pe), and axial temperature gradient (B). This investigation finally establishes the optimum values of the abovementioned parameters, leading to the minimum entropy generation of the system. We believe that results of this analysis could be helpful in optimizing the second-law performance of microscale thermal management devices, including the micro-heat exchangers, micro-reactors, and micro-heat pipes.

Vortex-scalar element calculations of a diffusion flame stabilized on a plane mixing layer

NASA Technical Reports Server (NTRS)

Ghoniem, Ahmed F.; Givi, Peyman

1987-01-01

The vortex-scalar element method, a scheme which utilizes vortex elements to discretize the region of high vorticity and scalar elements to represent species or temperature fields, is utilized in the numerical simulations of a two-dimensional reacting mixing layer. Computations are performed for a diffusion flame at high Reynolds and Peclet numbers without resorting to turbulence models. In the nonreacting flow, the mean and fluctuation profiles of a conserved scalar show good agreement with experimental measurements. Results for the reacting flow indicate that for temperature independent kinetics, the chemical reaction begins immediately downstream of the splitter plate where mixing starts. Results for the reacting flow with Arrhenius kinetics show an ignition delay, which depends on reactant temperature, before significant chemical reaction occurs. Harmonic forcing changes the structure of the layer, and concomitantly the rates of mixing and reaction, in accordance with experimental results. Strong stretch within the braids in the nonequilibrium kinetics case causes local flame quenching due to the temperature drop associated with the large convective fluxes.

Microscopic origin and macroscopic implications of lane formation in mixtures of oppositely-driven particles

NASA Astrophysics Data System (ADS)

Whitelam, Stephen

Colloidal particles of two types, driven in opposite directions, can segregate into lanes. I will describe some results on this phenomenon obtained by simple physical arguments and computer simulations. Laning results from rectification of diffusion on the scale of a particle diameter: oppositely-driven particles must, in the time taken to encounter each other in the direction of the drive, diffuse in the perpendicular direction by about one particle diameter. This geometric constraint implies that the diffusion constant of a particle, in the presence of those of the opposite type, grows approximately linearly with Peclet number, a prediction confirmed by our numerics. Such environment-dependent diffusion is statistically similar to an effective interparticle attraction; consistent with this observation, we find that oppositely-driven colloids display features characteristic of the simplest model system possessing both interparticle attractions and persistent motion, the driven Ising lattice gas. Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Laminar convective heat transfer of non-Newtonian nanofluids with constant wall temperature

NASA Astrophysics Data System (ADS)

Hojjat, M.; Etemad, S. Gh.; Bagheri, R.; Thibault, J.

2011-02-01

Nanofluids are obtained by dispersing homogeneously nanoparticles into a base fluid. Nanofluids often exhibit higher heat transfer rate in comparison with the base fluid. In the present study, forced convection heat transfer under laminar flow conditions was investigated experimentally for three types of non-Newtonian nanofluids in a circular tube with constant wall temperature. CMC solution was used as the base fluid and γ-Al2O3, TiO2 and CuO nanoparticles were homogeneously dispersed to create nanodispersions of different concentrations. Nanofluids as well as the base fluid show shear thinning (pseudoplastic) rheological behavior. Results show that the presence of nanoparticles increases the convective heat transfer of the nanodispersions in comparison with the base fluid. The convective heat transfer enhancement is more significant when both the Peclet number and the nanoparticle concentration are increased. The increase in convective heat transfer is higher than the increase caused by the augmentation of the effective thermal conductivity.

Free Dendritic Growth of Succinonitrile-Acetone Alloys with Thermosolutal Melt Convection

NASA Technical Reports Server (NTRS)

Beckermann, Christoph; Li, Ben Q.

2003-01-01

A stagnant film model of the effects of thermosolutal convection on free dendritic growth of alloys is developed, and its predictions are compared to available earth-based experimental data for succinonitrileacetone alloys. It is found that the convection model gives excellent agreement with the measured dendrite tip velocities and radii for low solute concentrations. However, at higher solute concentrations the present predictions show some deviations from the measured data, and the measured (thermal) Peclet numbers tend to fall even below the predictions from diffusion theory. Furthermore, the measured selection parameter (sigma*) is significantly above the expected value of 0.02 and exhibits strong scatter. It is shown that convection is not responsible for these discrepancies. Some of the deviations between the predicted and measured data at higher supercoolings could be caused by measurement difficulties. The systematic disagreement in the selection parameter for higher solute concentrations and all supercoolings examined, indicates that the theory for the selection of the dendrite tip operating state in alloys may need to be reexamined.

Hydrodynamic Aspects of Particle Clogging in Porous Media

PubMed Central

MAYS, DAVID C.; HUNT, JAMES R.

2010-01-01

Data from 6 filtration studies, representing 43 experiments, are analyzed with a simplified version of the single-parameter O’Melia and Ali clogging model. The model parameter displays a systematic dependence on fluid velocity, which was an independent variable in each study. A cake filtration model also explains the data from one filtration study by varying a single, velocity-dependent parameter, highlighting that clogging models, because they are empirical, are not unique. Limited experimental data indicate exponential depth dependence of particle accumulation, whose impact on clogging is quantified with an extended O’Melia and Ali model. The resulting two-parameter model successfully describes the increased clogging that is always observed in the top segment of a filter. However, even after accounting for particle penetration, the two-parameter model suggests that a velocity-dependent parameter representing deposit morphology must also be included to explain the data. Most of the experimental data are described by the single-parameter O’Melia and Ali model, and the model parameter is correlated to the collector Peclet number. PMID:15707058

Modeling residence-time distribution in horizontal screw hydrolysis reactors

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

Sievers, David A.; Stickel, Jonathan J.

The dilute-acid thermochemical hydrolysis step used in the production of liquid fuels from lignocellulosic biomass requires precise residence-time control to achieve high monomeric sugar yields. Difficulty has been encountered reproducing residence times and yields when small batch reaction conditions are scaled up to larger pilot-scale horizontal auger-tube type continuous reactors. A commonly used naive model estimated residence times of 6.2-16.7 min, but measured mean times were actually 1.4-2.2 the estimates. Here, this study investigated how reactor residence-time distribution (RTD) is affected by reactor characteristics and operational conditions, and developed a method to accurately predict the RTD based on key parameters.more » Screw speed, reactor physical dimensions, throughput rate, and process material density were identified as major factors affecting both the mean and standard deviation of RTDs. The general shape of RTDs was consistent with a constant value determined for skewness. The Peclet number quantified reactor plug-flow performance, which ranged between 20 and 357.« less

Modeling residence-time distribution in horizontal screw hydrolysis reactors

DOE PAGES

Sievers, David A.; Stickel, Jonathan J.

2017-10-12

The dilute-acid thermochemical hydrolysis step used in the production of liquid fuels from lignocellulosic biomass requires precise residence-time control to achieve high monomeric sugar yields. Difficulty has been encountered reproducing residence times and yields when small batch reaction conditions are scaled up to larger pilot-scale horizontal auger-tube type continuous reactors. A commonly used naive model estimated residence times of 6.2-16.7 min, but measured mean times were actually 1.4-2.2 the estimates. Here, this study investigated how reactor residence-time distribution (RTD) is affected by reactor characteristics and operational conditions, and developed a method to accurately predict the RTD based on key parameters.more » Screw speed, reactor physical dimensions, throughput rate, and process material density were identified as major factors affecting both the mean and standard deviation of RTDs. The general shape of RTDs was consistent with a constant value determined for skewness. The Peclet number quantified reactor plug-flow performance, which ranged between 20 and 357.« less

Shear thinning in soft particle suspensions

NASA Astrophysics Data System (ADS)

Voudouris, Panayiotis; van der Zanden, Berco; Florea, Daniel; Fahimi, Zahra; Wyss, Hans

2012-02-01

Suspensions of soft deformable particles are encountered in a wide range of food and biological materials. Examples are biological cells, micelles, vesicles or microgel particles. While the behavior of suspenions of hard spheres - the classical model system of colloid science - is reasonably well understood, a full understanding of these soft particle suspensions remains elusive. The relation between single particle properties and macroscopic mechanical behavior still remains poorly understood in these materials. Here we examine the surprising shear thinning behavior that is observed in soft particle suspensions as a function of particle softness. We use poly-N-isopropylacrylamide (p-NIPAM) microgel particles as a model system to study this effect in detail. These soft spheres show significant shear thinning even at very large Peclet numbers, where this would not be observed for hard particles. The degree of shear thinning is directly related to the single particle elastic properties, which we characterize by the recently developed Capillary Micromechanics technique. We present a simple model that qualitatively accounts for the observed behavior.

Flow-induced gelation of living (micellar) polymers

NASA Technical Reports Server (NTRS)

Bruinsma, Robijn; Gelbart, William M.; Ben-Shaul, Avinoam

1992-01-01

The effect of shear velocity gradients on the size (L) of rodlike micelles in dilute and semidilute solution is considered. A kinetic equation is introduced for the time-dependent concentration of aggregates of length L, consisting of 'bimolecular' combination processes L + L-prime yield (L + L-prime) and unimolecular fragmentations L yield L + (L - L-prime). The former are described by a generalization (from spheres to rods) of the Smoluchowski mechanism for shear-induced coalesence of emulsions, and the latter by incorporating the tension-deformation effects due to flow. Steady-state solutions to the kinetic equation are obtained, with the corresponding mean micellar size evaluated as a function of the Peclet number P (i.e., the dimensionless ratio of the flow rate and the rotational diffusion coefficient). For sufficiently dilute solutions, only a weak dependence of the micellar size on P is found. In the semidilute regime, however, an apparent divergence in the micellar size at P of about 1 suggests a flow-induced first-order gelation phenomenon.

Flowfield-Dependent Mixed Explicit-Implicit (FDMEL) Algorithm for Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Garcia, S. M.; Chung, T. J.

1997-01-01

Despite significant achievements in computational fluid dynamics, there still remain many fluid flow phenomena not well understood. For example, the prediction of temperature distributions is inaccurate when temperature gradients are high, particularly in shock wave turbulent boundary layer interactions close to the wall. Complexities of fluid flow phenomena include transition to turbulence, relaminarization separated flows, transition between viscous and inviscid incompressible and compressible flows, among others, in all speed regimes. The purpose of this paper is to introduce a new approach, called the Flowfield-Dependent Mixed Explicit-Implicit (FDMEI) method, in an attempt to resolve these difficult issues in Computational Fluid Dynamics (CFD). In this process, a total of six implicitness parameters characteristic of the current flowfield are introduced. They are calculated from the current flowfield or changes of Mach numbers, Reynolds numbers, Peclet numbers, and Damkoehler numbers (if reacting) at each nodal point and time step. This implies that every nodal point or element is provided with different or unique numerical scheme according to their current flowfield situations, whether compressible, incompressible, viscous, inviscid, laminar, turbulent, reacting, or nonreacting. In this procedure, discontinuities or fluctuations of an variables between adjacent nodal points are determined accurately. If these implicitness parameters are fixed to certain numbers instead of being calculated from the flowfield information, then practically all currently available schemes of finite differences or finite elements arise as special cases. Some benchmark problems to be presented in this paper will show the validity, accuracy, and efficiency of the proposed methodology.

Boundary Effects and Shear Thickening of Colloidal Suspensions: A study based on measurement of Suspension Microstructure

NASA Astrophysics Data System (ADS)

Perera, M. Tharanga D.

Microstructure is key to understanding rheological behaviors of flowing particulate suspensions. During the past decade, Stokesian Dynamics simulations have been the dominant method of determining suspension microstructure. Structure results obtained numerically reveal that an anisotropic structure is formed under high Peclet (Pe) number conditions. Researchers have used various experimental techniques such as small angle neutron scattering (SANS) and light scattering methods to validate microstructure. This work outlines an experimental technique based on confocal microscopy to study microstructure of a colloidal suspension in an index-matched fluid flowing in a microchannel. High resolution scans determining individual particle locations in suspensions 30-50 vol % yield quantitative results of the local microstructure in the form of the pair distribution function, g(r). From these experimentally determined g(r), the effect of shear rate, quantified by the Peclet number as a ratio of shear and Brownian stress, on the suspension viscosity and normal stress follow that seen in macroscopic rheological measurements and simulations. It is generally believed that shear thickening behavior of colloidal suspensions is driven by the formation of hydroclusters. From measurements of particle locations, hydroclusters are identified. The number of hydroclusters grows exponentially with increasing Pe, and the onset of shear thickening is driven by the increase in formation of clusters having 5-8 particles. At higher Pe, we notice the emergence of 12 or more particle clusters. The internal structure of these hydroclusters has been investigated, and there is some evidence that particles internal to hydroclusters preferentially align along the 45° and 135° axis. Beyond observations of bulk suspension behavior, the influence of boundaries on suspension microstructure is also investigated. Experiments were performed for suspensions flowing over smooth walls, made of glass coverslips, and over rough walls having a high density coating of particles. These results show that there is more order in structure near smooth boundaries while near rough boundaries the structure is similar to that found in the bulk. The relative viscosity and normal stress differences also indicate that boundaries have an effect up as far as 6 particle diameters away from the boundary. Finally, we investigate the microstructure evolvement in a model porous medium and notice that such boundary effects come into play in such real process flows. The confocal microscopy technique also provides us with the advantage of measuring structure in real process flows. We have investigated how the microstructure evolves upstream and downstream in a porous medium. We notice more structure in a high volume fraction suspension and notice anisotropic behavior at regions where shear from the wall of the posts dominate. In other cases, a mixed flow behavior is observed due to collisions between pore surfaces and other particles resulting in a deviation from flow streamlines.

A porous flow approach to model thermal non-equilibrium applicable to melt migration

NASA Astrophysics Data System (ADS)

Schmeling, Harro; Marquart, Gabriele; Grebe, Michael

2018-01-01

We develop an approach for heat exchange between a fluid and a solid phase of a porous medium where the temperatures of the fluid and matrix are not in thermal equilibrium. The formulation considers moving of the fluid within a resting or deforming porous matrix in an Eulerian coordinate system. The approach can be applied, for example, to partially molten systems or to brine transport in porous rocks. We start from an existing theory for heat exchange where the energy conservation equations for the fluid and the solid phases are separated and coupled by a heat exchange term. This term is extended to account for the full history of heat exchange. It depends on the microscopic geometry of the fluid phase. For the case of solid containing hot, fluid-filled channels, we derive an expression based on a time-dependent Fourier approach for periodic half-waves. On the macroscopic scale, the temporal evolution of the heat exchange leads to a convolution integral along the flow path of the solid, which simplifies considerably in case of a resting matrix. The evolution of the temperature in both phases with time is derived by inserting the heat exchange term into the energy equations. We explore the effects of thermal non-equilibrium between fluid and solid by considering simple cases with sudden temperature differences between fluid and solid as initial or boundary conditions, and by varying the fluid velocity with respect to the resting porous solid. Our results agree well with an analytical solution for non-moving fluid and solid. The temperature difference between solid and fluid depends on the Peclet number based on the Darcy velocity. For Peclet numbers larger than 1, the temperature difference after one diffusion time reaches 5 per cent of \\tilde{T} or more (\\tilde{T} is a scaling temperature, e.g. the initial temperature difference). Thus, our results imply that thermal non-equilibrium can play an important role for melt migration through partially molten systems where melt focuses into melt channels near the transition to melt ascent by dykes. Our method is based on solving the convolution integration for the heat exchange over the full flow history, which is numerically expensive. We tested to replace the heat exchange term by an instantaneous, approximate term. We found considerable errors on the short timescale, but a good agreement on the long timescale if appropriate parameters for the approximate terms are used. We derived these parameters which may be implemented in fully dynamical two-phase flow formulations of melt migration in the Earth.

Effect of permeable flow on cyclic layering in solidifying magma bodies: Insights from an analog experiment of diffusion-precipitation systems

NASA Astrophysics Data System (ADS)

Toramaru, A.; Yamauchi, S.

2012-04-01

Characteristic structures such as rhythmic layering, cress cumulate, cross bedding, perpendicular feldspar rock etc, are commonly observed in layered intrusion or shallow magmatic intrusions. These structures result from complex processes including thermal and compositional diffusions, crystallization, crystal settling, convection and interaction among three phases (crystals, bubble, melt). In order to understand how the differentiation proceeds in solidifying magma bodies from each characteristic structure together with chemical signatures, it is necessary to evaluate the relative importance among these elemental processes on structures. As an attempt to evaluate the effect of advection on a diffusion-related structure, we carried out an analog experiment of Liesegang system using lead-iodide (PbI2) crystallization in agar media which have been normally used to prohibit convection. In the ordinary Liesegang band formation experiments including only diffusion and crystallization kinetics without any advection and convection, the precipitation bands develop with regular spacing following a geometric progression due to two-component diffusion and reaction with supersaturation. This type of banding structure has been advocated as the same type of cyclic layering or vesicle layering (a sort of rhythmic layering) in dykes or sills. In order to see the effect of one-directional advection on Liesegang band, we apply the electric field (5 V to 25 V for a distance 15 cm) along the concentration gradient in agar media, thereby counteracting flows of lead anion Pb2+ and iodide ion I- are driven at constant velocities. The flows of anions and ions are equivalent to the permeable flows in porous media of crystal mush. The resultant precipitation structures exhibit very curious banding structure in which band spacings do not change with distance, are nearly constant and quite narrow, depending on the voltage, unlike those in ordinary Liesegang bands in which band spacings increase with distance following geometric progression. Further interestingly each band consists of a lot of very tiny irregular-shaped crystal aggregates. From experimental results and scaling arguments, with regard to the effect of one directional permeable flow on band spacing of cyclic layering, we propose a hypothesis of constant Peclet number that Peclet number (ratio of flow velocity to diffusive velocity) is nearly unity. By applying the hypothesis to natural examples, we can estimate a value of permeable flow velocity of interstitial melts in differentiating magma bodies from values of a band spacing and diffusivity data.

Separation of electrolyte solutions by reverse osmosis.

PubMed

Starov, V M; Churaev, N V

1993-05-09

The paper presented is subdivided into two parts. The first one includes a survey of current notions concerning the physico-chemical nature of interaction potential phi between dissolved molecules or ions and water with a membrane material. Special attention is paid to the structural potential and the potential of image forces. The main conclusion is that the potential of interaction phi determines the major part of phenomena which are relevant for reverse osmosis (RO) separation. In the second part the distribution coefficient gamma = exp (phi) is supposed to be known and a survey of theoretical investigations of RO processes is undertaken. The so called homogeneous model of RO membranes is employed and concentration polarization is taken into account. Two main points in this investigation should be emphasized, that is, taking into account concentration polarization and a theory of RO separation of electrolyte mixtures. The maximum value of rejection coefficient and corresponding optimum velocity of filtration are calculated. Negative rejection of some ions from the mixture is explained, as well as a change in pH of filtrate. The streaming potential is calculated as a function of Peclet number, distribution coefficients, membrane charge and so on in all cases. The suggested theory gives the possibility to explain a number of phenomena in RO separation of electrolyte solutions.

Polymer Stress-Gradient Induced Migration in Thin Film Flow Over Topography

NASA Astrophysics Data System (ADS)

Tsouka, Sophia; Dimakopoulos, Yiannis; Tsamopoulos, John

2014-11-01

We consider the 2D, steady film flow of a dilute polymer solution over a periodic topography. We examine how the distribution of polymer in the planarization of topographical features is affected by flow intensity and physical properties. The thermodynamically acceptable, Mavrantzas-Beris two-fluid Hamiltonian model is used for polymer migration. The resulting system of differential equations is solved via the mixed FE method combined with an elliptic grid generation scheme. We present numerical results for polymer concentration, stress, velocity and flux of components as a function of the non-dimensional parameters of the problem (Deborah, Peclet, Reynolds and Capillary numbers, ratio of solvent viscosity to total liquid viscosity and geometric features of the topography). Polymer migration to the free surface is enhanced when the cavity gets steeper and deeper. This increases the spatial extent of the polymer depletion layer and induces strong banding in the stresses away from the substrate wall, especially in low polymer concentration. Macromolecules with longer relaxation times are predicted to migrate towards the free surface more easily, while high surface tension combined with a certain range of Reynolds numbers affects the free surface deformations. Work supported by the General Secretariat of Research & Technology of Greece through the program ``Excellence'' (Grant No. 1918) in the framework ``Education and Lifelong Learning'' co-funded by the ESF.

On the survival of zombie vortices in protoplanetary discs

NASA Astrophysics Data System (ADS)

Lesur, Geoffroy R. J.; Latter, Henrik

2016-11-01

Recently it has been proposed that the zombie vortex instability (ZVI) could precipitate hydrodynamical activity and angular momentum transport in unmagnetized regions of protoplanetary discs, also known as `dead zones'. In this Letter we scrutinize, with high-resolution 3D spectral simulations, the onset and survival of this instability in the presence of viscous and thermal physics. First, we find that the ZVI is strongly dependent on the nature of the viscous operator. Although the ZVI is easily obtained with hyperdiffusion, it is difficult to sustain with physical (second order) diffusion operators up to Reynolds numbers as high as 107. This sensitivity is probably due to the ZVI's reliance on critical layers, whose characteristic length-scale, structure, and dynamics are controlled by viscous diffusion. Second, we observe that the ZVI is sensitive to radiative processes, and indeed only operates when the Peclet number is greater than a critical value ˜104, or when the cooling time is longer than ˜10Ω-1. As a consequence, the ZVI struggles to appear at R ≳ 0.3 au in standard 0.01 M⊙ T Tauri disc models, though younger more massive discs provide a more hospitable environment. Together these results question the prevalence of the ZVI in protoplanetary discs.

A finite-volume ELLAM for three-dimensional solute-transport modeling

USGS Publications Warehouse

Russell, T.F.; Heberton, C.I.; Konikow, Leonard F.; Hornberger, G.Z.

2003-01-01

A three-dimensional finite-volume ELLAM method has been developed, tested, and successfully implemented as part of the U.S. Geological Survey (USGS) MODFLOW-2000 ground water modeling package. It is included as a solver option for the Ground Water Transport process. The FVELLAM uses space-time finite volumes oriented along the streamlines of the flow field to solve an integral form of the solute-transport equation, thus combining local and global mass conservation with the advantages of Eulerian-Lagrangian characteristic methods. The USGS FVELLAM code simulates solute transport in flowing ground water for a single dissolved solute constituent and represents the processes of advective transport, hydrodynamic dispersion, mixing from fluid sources, retardation, and decay. Implicit time discretization of the dispersive and source/sink terms is combined with a Lagrangian treatment of advection, in which forward tracking moves mass to the new time level, distributing mass among destination cells using approximate indicator functions. This allows the use of large transport time increments (large Courant numbers) with accurate results, even for advection-dominated systems (large Peclet numbers). Four test cases, including comparisons with analytical solutions and benchmarking against other numerical codes, are presented that indicate that the FVELLAM can usually yield excellent results, even if relatively few transport time steps are used, although the quality of the results is problem-dependent.

Mass Transport and Shear Stress in the Carotid Artery Bifurcation

NASA Astrophysics Data System (ADS)

Gorder, Riley; Aliseda, Alberto

2010-11-01

The carotid artery bifurcation (CAB) is one of the leading sites for atherosclerosis, a major cause of death and disability in the developed world. The specific processes by which the complex flow found at the bifurcation and carotid sinus promotes plaque formation and growth are not fully understood. Shear stress, mass transport, and flow residence times are considered key factors. Although the governing equations closely link shear stress and mass transfer, the pulsatile, transitional, and detached flow found at the CAB can lead to differences between regions of WSS and mass transfer statistics. In this study, CAB geometries are reconstructed from patient specific 3D ultrasound medical imaging. Using ANSYS FLUENT, the fluid flow and scalar transport was solved using realistic flow conditions and various mass transfer boundary conditions. The spatial and temporal resolution was validated against the analytical solution of the Graetz-Nusselt problem with constant wall flux to ensure the scalar transport is resolved for a Peclet number up to 100,000. High residence time regions are investigated by determining the number of cardiac cycles required to flush out the carotid sinus. The correlations between regions of low WSS, high OSI, and scalar concentration are computed and interpreted in the context of atherosclerotic plaque origin and progression.

Treatment of internal sources in the finite-volume ELLAM

USGS Publications Warehouse

Healy, R.W.; ,; ,; ,; ,; ,

2000-01-01

The finite-volume Eulerian-Lagrangian localized adjoint method (FVELLAM) is a mass-conservative approach for solving the advection-dispersion equation. The method has been shown to be accurate and efficient for solving advection-dominated problems of solute transport in ground water in 1, 2, and 3 dimensions. Previous implementations of FVELLAM have had difficulty in representing internal sources because the standard assumption of lowest order Raviart-Thomas velocity field does not hold for source cells. Therefore, tracking of particles within source cells is problematic. A new approach has been developed to account for internal sources in FVELLAM. It is assumed that the source is uniformly distributed across a grid cell and that instantaneous mixing takes place within the cell, such that concentration is uniform across the cell at any time. Sub-time steps are used in the time-integration scheme to track mass outflow from the edges of the source cell. This avoids the need for tracking within the source cell. We describe the new method and compare results for a test problem with a wide range of cell Peclet numbers.

The nature of the laning transition in two dimensions

NASA Astrophysics Data System (ADS)

Glanz, T.; Löwen, H.

2012-11-01

If a binary colloidal mixture is oppositely driven by an external field, a transition towards a laned state occurs at sufficiently large drives, where particles driven alike form elongated structures (‘lanes’) characterized by a large correlation length ξ along the drive. Here we perform extensive Brownian dynamics computer simulations on a two-dimensional equimolar binary Yukawa system driven by a constant force that acts oppositely on the two species. We systematically address finite-size effects on lane formation by exploring large systems up to 262 144 particles under various boundary conditions. It is found that the correlation length ξ along the field depends exponentially on the driving force (or Peclet number). Conversely, in a finite system, ξ reaches a fraction of the system size at a driving force which is logarithmic in the system size, implying massive finite-size corrections. For a fixed finite drive, ξ does not diverge in the thermodynamic limit. Therefore, though laning has a signature as a sharp transition in a finite system, it is a smooth crossover in the thermodynamic limit.

An enriched finite element method to fractional advection-diffusion equation

NASA Astrophysics Data System (ADS)

Luan, Shengzhi; Lian, Yanping; Ying, Yuping; Tang, Shaoqiang; Wagner, Gregory J.; Liu, Wing Kam

2017-08-01

In this paper, an enriched finite element method with fractional basis [ 1,x^{α }] for spatial fractional partial differential equations is proposed to obtain more stable and accurate numerical solutions. For pure fractional diffusion equation without advection, the enriched Galerkin finite element method formulation is demonstrated to simulate the exact solution successfully without any numerical oscillation, which is advantageous compared to the traditional Galerkin finite element method with integer basis [ 1,x] . For fractional advection-diffusion equation, the oscillatory behavior becomes complex due to the introduction of the advection term which can be characterized by a fractional element Peclet number. For the purpose of addressing the more complex numerical oscillation, an enriched Petrov-Galerkin finite element method is developed by using a dimensionless fractional stabilization parameter, which is formulated through a minimization of the residual of the nodal solution. The effectiveness and accuracy of the enriched finite element method are demonstrated by a series of numerical examples of fractional diffusion equation and fractional advection-diffusion equation, including both one-dimensional and two-dimensional, steady-state and time-dependent cases.

Trojan particles: Large porous carriers of nanoparticles for drug delivery

PubMed Central

Tsapis, N.; Bennett, D.; Jackson, B.; Weitz, D. A.; Edwards, D. A.

2002-01-01

We have combined the drug release and delivery potential of nanoparticle (NP) systems with the ease of flow, processing, and aerosolization potential of large porous particle (LPP) systems by spray drying solutions of polymeric and nonpolymeric NPs into extremely thin-walled macroscale structures. These hybrid LPPs exhibit much better flow and aerosolization properties than the NPs; yet, unlike the LPPs, which dissolve in physiological conditions to produce molecular constituents, the hybrid LPPs dissolve to produce NPs, with the drug release and delivery advantages associated with NP delivery systems. Formation of the large porous NP (LPNP) aggregates occurs via a spray-drying process that ensures the drying time of the sprayed droplet is sufficiently shorter than the characteristic time for redistribution of NPs by diffusion within the drying droplet, implying a local Peclet number much greater than unity. Additional control over LPNPs physical characteristics is achieved by adding other components to the spray-dried solutions, including sugars, lipids, polymers, and proteins. The ability to produce LPNPs appears to be largely independent of molecular component type as well as the size or chemical nature of the NPs. PMID:12200546

Unsteady Oxygen Transfer in Space-Filling Models of the Pulmonary Acinus

NASA Astrophysics Data System (ADS)

Hofemeier, Philipp; Shachar-Berman, Lihi; Filoche, Marcel; Sznitman, Josue

2014-11-01

Diffusional screening in the pulmonary acinus is a well-known physical phenomenon that results from the depletion of fresh oxygen in proximal acinar generations diffusing through the alveolar wall membranes and effectively creating a gradient in the oxygen partial pressure along the acinar airways. Until present, most studies have focused on steady-state oxygen diffusion in generic sub-acinar structures and discarded convective oxygen transport due to low Peclet numbers in this region. Such studies, however, fall typically short in capturing the complex morphology of acinar airways as well as the oscillatory nature of convecive acinar breathing. Here, we revisit this problem and solve the convective-diffusive transport equations in breathing 3D acinar structures, underlining the significance of convective flows in proximal acinar generations as well as recirculating alveolar flow patterns. In particular, to assess diffusional screening, we monitor time-dependent efficiencies of the acinus under cyclic breathing motion. Our study emphasizes the necessity of capturing both a dynamically breathing and anatomically-realistic model of the sub-acinus to characterize unsteady oxygen transport across the acinar walls.

Comparison of catalytic converter performance in internal combustion engine fueled with Ron 95 and Ron 97 gasoline

NASA Astrophysics Data System (ADS)

Leman, A. M.; Rahman, Fakhrurrazi; Jajuli, Afiqah; Feriyanto, Dafit; Zakaria, Supaat

2017-09-01

Generating ideal stability between engine performance, fuel consumption and emission is one of the main challenges in the automotive industry. The characteristics of engine combustion and creation of emission might simply change with different types of operating parameters. This study aims in investigating the relationship between two types of fuels on the performance and exhaust emission of internal combustion engine using ceramic and metallic catalytic converters. Experimental tests were performed on Mitsubishi 4G93 engine by applying several ranges of engine speeds to determine the conversion of pollutant gases released by the engine. The obtained results specify that the usage of RON 97 equipped with metallic converters might increase the conversion percentage of 1.31% for CO and 126 ppm of HC gases. The metallic converters can perform higher conversion compared to ceramic because in the high space velocities, metallic has higher surface geometry area and higher amount of transverse Peclet number (Pi). Ceramic converters achieved conversion at 2496 ppm of NOx gas, which is higher than the metallic converter.

Experimental studies on laminar flow heat transfer in nanofluids flowing through a straight circular tube with and without V-cut twisted tape insert

NASA Astrophysics Data System (ADS)

Arunachalam, U.; Edwin, M.

2018-03-01

This paper presents experimental studies on the convective heat transfer and friction factor characteristics of flows in a straight circular tube with and without V-cut twisted tapeinserts using Al2O3-Cu/water hybrid nanofluid as working fluid and also comparative studies between Alumina nanofluid and (Cu-Alumina) hybrid nanofluid is conducted. This work is restricted to one type of hybrid nanofluid only. It also does not include the effect of twisted tape dimensions on heat transfer coefficient and pressure drop.Itis observed that the experimental convective heat transfer coefficient increases slightly with an increase in particle volume concentration from 0.1 and 0.4%. The experimental data is in good agreement with the previous models and correlations.The experimental results showed a good enhancement in Nusselt number for Peclet number from 2580 to 11,780 compared to Nusselt number of water, when the copper nanofluid is 0.01% volume concentration and mixed with 0.4% concentration of Alumina nanofluid.Itis also noticed that 0.01% Al2O3-Cu/water hybrid nanofluidhas a higher friction factor than the Al2O3/water nanofluid and base fluid. Since the magnitude of thermal enhancement factor (η) has been observed to be only marginally higher than unity (1.01 to 1.05), the net benefit of inserting V - cut twisted tapes in nanofluids is also nevertheless marginal.

Advection within side-by-side liquid micro-cylinders in a cross-flow

NASA Astrophysics Data System (ADS)

Dong, Qingming; Sau, Amalendu

2017-11-01

The gaseous SO2 entrainment from outer air stream and dispersion in binary and ternary liquid micro-cylinders appearing side-by-side are examined hereby. The separation/attachment regulated non-uniform interfacial momentum exchange creates main stream driven "primary" and shear reversed "secondary" vortices in the liquid cylinders. At separation points, the sense of rotation of the generated "primary-secondary" vortex pair remains inward directed. We define such a vortex pair as the "inflow" type. However, at stagnation or attachment points, the sense of rotation of a "primary-primary" or "secondary-secondary" vortex pair remains outward directed, and such a vortex pair is defined as the "outflow" type. For the coupled water cylinders facing an oncoming stream contaminated by gaseous SO2, its absorption and internal transport are effectively controlled by dominant "inflow" and "outflow" natured dynamics of the said vortex pairs, besides by diffusion. The evolving "inflow" natured "primary-secondary" vortex pairs at separation points actively entrain the outer SO2, whereas the "outflow" natured vortex-pairs oppose SO2 entry through the stagnation regions. Moreover, the blockage induced steady-symmetric, steady-deflected, and flip-flopping air-jets through gaps, for varied gap-ratio (1 ≤ G/R ≤ 4) and Reynolds number (30 ≤ Re ≤ 160), create distinctive impact both on quantitative SO2 absorption (mso2 ') and convective nature of the SO2 transport in upper, lower, and middle cylinders, by virtue of modified strength and size of the inflow and outflow paired vortices. The present study shows that the tiny "secondary vortices" play important roles in SO2 entrainment and in effectively controlling the local absorption rate Rs o2. The sudden acceleration and upward/downward deflection of gap-flows enhanced near-neck advective SO2 entrainment by suitably strengthening the "inflow" natured local vortex dynamics. Conversely, for the reduced size of secondary vortices, the saturation becomes delayed. In addition, for decreased vertical spacing of micro-cylinders (R = 40 μm) falling below the diameter-length "2R," the SO2 absorption (mso2 ') only gets slower. We provide extensive analysis of two-phase transport phenomena in terms of interactive shear-stress, pressure, and characteristic time-ratio "Tr" of advection-diffusion processes, for varied G/R, Re, and liquid phase Peclet number "Pel" (96 ≤ Pel ≤ 1333), to present a better insight into the governing physics.

Effects of Soluble Surfactant on Lateral Migration of a Bubble in a Shear Flow

NASA Astrophysics Data System (ADS)

Muradoglu, Metin; Tryggvason, Gretar

2014-11-01

Motivated by the recent experimental study of Takagi et al. (2008), direct numerical simulations are performed to examine effects of soluble surfactant on the lateral migration of a deformable bubble in a pressure-driven channel flow. The interfacial and bulk surfactant concentration evolution equations are solved fully coupled with the incompressible Navier-Stokes equations. A non-linear equation of state is used to relate interfacial surface tension to surfactant concentration at the interface. A multiscale method is developed to handle the mass exchange between the interface and bulk fluid at high Peclet numbers, using a boundary-layer approximation next to the bubble and a relatively coarse grid for the rest of the flow. It is found that the surfactant induced Marangoni stresses can dominate over the shear-induced lift force and thus alter the behavior of the bubble completely, i.e., the contaminated bubble drifts away from the channel wall and stabilizes at the center of the channel in contrast with the corresponding clean bubble that drifts toward the wall and stabilizes near the wall. The Scientific and Technical Research Council of Turkey (TUBITAK), Grant 112M181 and Turkish Academy of Sciences (TUBA).

Fluctuation, dissipation, and a non-equilibrium ``equation of state'' via nonlinear microrheology of hydrodynamically interacting colloids

NASA Astrophysics Data System (ADS)

Chu, Henry; Zia, Roseanna

2014-11-01

In our recently developed non-equilibrium Stokes-Einstein relation for microrheology, we showed that, in the absence of hydrodynamic interactions, the stress in a suspension is given by a balance between fluctuation and dissipation. Here we generalize our theory to develop a simple analytical relation connecting diffusive fluctuation, viscous dissipation and suspension stress in systems of hydrodynamically interacting colloids. In active microrheology, a Brownian probe is driven through a complex medium. The strength of probe forcing compared to the entropic restoring force defines a Peclet number, Pe. In the absence of hydrodynamics, normal stress differences scale as Pe4 and Pe for weak and strong probe forcing, respectively. But as hydrodynamics become important, interparticle forces give way to lubrication interactions and the normal stresses scale as Pe2 and Peδln(Pe), where 0.773 <= δ <= 1 as hydrodynamics vary from strong to weak. The new phenomenological theory is shown to agree with standard micromechanical definitions of the stress. A connection is made between the stress and an effective temperature of the medium, prompting the interpretation of the particle stress as the energy density, and the expression for osmotic pressure as a ``non-equilibrium equation of state.''

Analysis of liquid-metal-jet impingement cooling in a corner region and for a row of jets

NASA Technical Reports Server (NTRS)

Siegel, R.

1975-01-01

A conformal mapping method was used to analyze liquid-metal-jet impingement heat transfer. The jet flow region and energy equation are transformed to correspond to uniform flow in a parallel plate channel with nonuniform heat addition along a portion of one wall. The exact solution for the wall-temperature distribution was obtained in the transformed channel, and the results are mapped back into the physical plane. Two geometries are analyzed. One is for a single slot jet directed either into an interior corner formed by two flat plates, or over the external sides of the corner; the flat plates are uniformly heated, and the corner can have various included angles. The heat-transfer coefficient at the stagnation point at the apex of the plates is obtained as a function of the corner angle, and temperature distributions are calculated along the heated walls. The second geometry is an infinite row of uniformly spaced parallel slot jets impinging normally against a uniformly heated plate. The heat-transfer behavior is obtained as a function of the spacing between the jets. Results are given for several jet Peclet numbers from 5 to 50.

Statistics of chemical gradients in heterogeneous porous media

NASA Astrophysics Data System (ADS)

Le Borgne, T.; Huck, P. D.; Dentz, M.; Villermaux, E.

2017-12-01

As they create chemical disequilibrium and drive mixing fluxes, spatial gradients in solute concentrations exert a strong control on mixing and biogeochemical reactions in the subsurface. Large concentration gradients may develop in particular at interfaces between surface water and groundwater bodies, such as hyporheic zones, sea water - surface water interfaces or recharge areas. They also develop around contaminant plumes and fluids injected in subsurface operations. While macrodispersion theories predict smooth gradients, decaying in time due to dispersive dissipation, we show that concentration gradients are sustained by flow heterogeneity and have broadly distributed values. We present a general theory predicting the statistics of concentration gradients from the flow heterogeneity (Le Borgne et al., 2017). Analytical predictions are validated from high resolution simulations of transport in heterogeneous Darcy fields ranging from low to high permeability variances and low to high Peclet numbers. This modelling framework hence opens new perspectives for quantifying the dynamics of chemical gradients and the kinetics of associated biogeochemical reactions in heterogeneous subsurface environments.Reference:Le Borgne T., P.D. Huck, M. Dentz and E. Villermaux (2017) Scalar gradients in stirred mixtures and the deconstruction of random fields, J. of Fluid Mech. vol. 812, pp. 578-610 doi:10.1017/jfm.2016.799

Observations of axisymmetric tracer particle orientation during flow through a dilute fixed bed of fibers

NASA Astrophysics Data System (ADS)

Frattini, Paul L.; Shaqfeh, Eric S. G.; Levy, Jeffrey L.; Koch, Donald L.

1991-11-01

Direct microstructural evidence for net tracer particle orientation induced solely by hydrodynamic interactions in a dilute, disordered, fibrous media is reported. A dilute fixed bed of randomly placed fibers was constructed and glycerol/water suspensions of either synthetic akaganeite (βFeOOH, average aspect ratio 6.3) or hematite (αFe2O3, average aspect ratio 1.6) tracer particles were made to flow axially through the bed at prescribed flow rates. Conservative linear dichroism, a noninvasive light scattering technique, was employed to provide a direct measure of the orientational order parameter for the tracer particle population at the end of the bed. The effect of Brownian motion on the hydrodynamically induced order in the suspensions was studied over three orders of magnitude in scaled rotary Peclet number, 5

Assessment of a low-cost, point-of-use, ultraviolet water disinfection technology.

PubMed

Brownell, Sarah A; Chakrabarti, Alicia R; Kaser, Forest M; Connelly, Lloyd G; Peletz, Rachel L; Reygadas, Fermin; Lang, Micah J; Kammen, Daniel M; Nelson, Kara L

2008-03-01

We describe a point-of-use (POU) ultraviolet (UV) disinfection technology, the UV Tube, which can be made with locally available resources around the world for under $50 US. Laboratory and field studies were conducted to characterize the UV Tube's performance when treating a flowrate of 5 L/min. Based on biological assays with MS2 coliphage, the UV Tube delivered an average fluence of 900+/-80 J/m(2) (95% CI) in water with an absorption coefficient of 0.01 cm(-1). The residence time distribution in the UV Tube was characterized as plug flow with dispersion (Peclet Number = 19.7) and a mean hydraulic residence time of 36 s. Undesirable compounds were leached or produced from UV Tubes constructed with unlined ABS, PVC, or a galvanized steel liner. Lining the PVC pipe with stainless steel, however, prevented production of regulated halogenated organics. A small field study in two rural communities in Baja California Sur demonstrated that the UV Tube reduced E. coli concentrations to less than 1/100 ml in 65 out of 70 samples. Based on these results, we conclude that the UV Tube is a promising technology for treating household drinking water at the point of use.

Gyrotactic swimmer dispersion in pipe flow: testing the theory

NASA Astrophysics Data System (ADS)

Croze, Ottavio A.; Bearon, Rachel N.; Bees, Martin A.

2017-04-01

Suspensions of microswimmers are a rich source of fascinating new fluid mechanics. Recently we predicted the active pipe flow dispersion of gyrotactic microalgae, whose orientation is biased by gravity and flow shear. Analytical theory predicts that these active swimmers disperse in a markedly distinct manner from passive tracers (Taylor dispersion). Dispersing swimmers display nonzero drift and effective diffusivity that is non-monotonic with P$\\'e$clet number. Such predictions agree with numerical simulations, but hitherto have not been tested experimentally. Here, to facilitate comparison, we obtain new solutions of the axial dispersion theory accounting both for swimmer negative buoyancy and a local nonlinear response of swimmers to shear, provided by two alternative microscopic stochastic descriptions. We obtain new predictions for suspensions of the model swimming alga $\\it Dunaliella\\,salina$, whose motility and buoyant mass we parametrise using tracking video microscopy. We then present a new experimental method to measure gyrotactic dispersion using fluorescently stained $\\it D. salina$ and provide a preliminary comparison with predictions of a nonzero drift above the mean flow for each microscopic stochastic description. Finally, we propose further experiments for a full experimental characterisation of gyrotactic dispersion measures and discuss implications of our results for algal dispersion in industrial photobioreactors.

Experimental investigation of heat transfer and pressure drop characteristics of non-Newtonian nanofluids flowing in the shell-side of a helical baffle heat exchanger with low-finned tubes

NASA Astrophysics Data System (ADS)

Tan, Yunkai; He, Zhenbin; Xu, Tao; Fang, Xiaoming; Gao, Xuenong; Zhang, Zhengguo

2017-09-01

An aqueous solution of Xanthan Gum (XG) at a weight fraction as high as 0.2% was used as the base liquid, the stable MWCNTs-dispersed non-Newtonian nanofluids at different weight factions of MWCNTs was prepared. The base fluid and all nanofluids show pseudoplastic (shear-thinning) rheological behavior. Experiments were performed to compare the shell-side forced convective heat transfer coefficient and pressure drop of non-Newtonian nanofluids to those of non-Newtonian base fluid in an integrally helical baffle heat exchanger with low-finned tubes. The experimental results showed that the enhancement of the convective heat transfer coefficient increases with an increase in the Peclet number and the nanoparticle concentration. For nanofluids with 1.0, 0.5 and 0.2 wt% of multi-walled carbon nanotubes (MWCNTs), the heat transfer coefficients respectively augmented by 24.3, 13.2 and 4.7% on average and the pressure drops become larger than those of the base fluid. The comprehensive thermal performance factor is higher than one and increases with an increasing weight fraction of MWCNTs. A remarkable heat transfer enhancement in the shell side of helical baffle heat exchanger with low-finned tubes can be obtained by adding MWCNTs into XG aqueous solution based on thermal resistance analysis. New correlations have been suggested for the shell-side friction coefficient and the Nusselt numbers of non-Newtonian nanofluids and give very good agreement with experimental data.

Effects of microscale inertia on heat or mass transfer from a drop

NASA Astrophysics Data System (ADS)

Krishnamurthy, Deepak; Subramanian, Ganesh

2012-11-01

Heat or mass transport from suspensions of solid particles or drops is ubiquitous in many industrial processes. In the zero inertia limit the transport is diffusion limited owing to the presence of closed streamlines around each particle. A small but finite amount of inertia though, results in a vastly different picture, greatly enhancing transport by destroying the closed streamline configuration. We develop a theoretical formulation to study the effects of weak inertia on transport from a density-matched drop in a 2D linear flow. It is shown that, unlike a solid particle, the near-surface streamlines are closed only when the viscosity ratio (λ) exceeds a critical value λc = 2 α / (1- α) , where α is the linear flow parameter measuring relative magnitudes of extension and vorticity. The velocity field on the drop surface can be characterized using a complex-valued analogue of the (C, τ) coordinate system used to describe Jeffrey orbits of an axisymmetric particle. In the open-streamline case (λ < λ c) , convective transport occurs even with zero inertia, and for large Peclet number (Pe) (the relative magnitude of convective to diffusive transport), the Nusselt number (dimensionless rate of heat transfer) is expected to scale as F(α, λ) Pe1/2 and is determined via a boundary layer analysis in the (C, τ) coordinate system. In the closed streamline case (λ > λ c) , similar to the solid particle, inertia plays a crucial role, and the Nusselt number must scale as G(α, λ)Re1/2Pe1/2. A methodology is developed to analyze the convection along spiraling streamlines using a physically motivated choice of coordinate system on the drop surface.

Direct numerical simulation of turbulent mixing at very low Schmidt number with a uniform mean gradient

NASA Astrophysics Data System (ADS)

Yeung, P. K.; Sreenivasan, K. R.

2014-01-01

In a recent direct numerical simulation (DNS) study [P. K. Yeung and K. R. Sreenivasan, "Spectrum of passive scalars of high molecular diffusivity in turbulent mixing," J. Fluid Mech. 716, R14 (2013)] with Schmidt number as low as 1/2048, we verified the essential physical content of the theory of Batchelor, Howells, and Townsend ["Small-scale variation of convected quantities like temperature in turbulent fluid. 2. The case of large conductivity," J. Fluid Mech. 5, 134 (1959)] for turbulent passive scalar fields with very strong diffusivity, decaying in the absence of any production mechanism. In particular, we confirmed the existence of the -17/3 power of the scalar spectral density in the so-called inertial-diffusive range. In the present paper, we consider the DNS of the same problem, but in the presence of a uniform mean gradient, which leads to the production of scalar fluctuations at (primarily) the large scales. For the parameters of the simulations, the presence of the mean gradient alters the physics of mixing fundamentally at low Peclet numbers. While the spectrum still follows a -17/3 power law in the inertial-diffusive range, the pre-factor is non-universal and depends on the magnitude of the mean scalar gradient. Spectral transfer is greatly reduced in comparison with those for moderately and weakly diffusive scalars, leading to several distinctive features such as the absence of dissipative anomaly and a new balance of terms in the spectral transfer equation for the scalar variance, differing from the case of zero gradient. We use the DNS results to present an alternative explanation for the observed scaling behavior, and discuss a few spectral characteristics in detail.

Effects of incomplete mixing on reactive transport in flows through heterogeneous porous media

NASA Astrophysics Data System (ADS)

Wright, Elise E.; Richter, David H.; Bolster, Diogo

2017-11-01

The phenomenon of incomplete mixing reduces bulk effective reaction rates in reactive transport. Many existing models do not account for these effects, resulting in the overestimation of reaction rates in laboratory and field settings. To date, most studies on incomplete mixing have focused on diffusive systems; here, we extend these to explore the role that flow heterogeneity has on incomplete mixing. To do this, we examine reactive transport using a Lagrangian reactive particle tracking algorithm in two-dimensional idealized heterogeneous porous media. Contingent on the nondimensional Peclet and Damköhler numbers in the system, it was found that near well-mixed behavior could be observed at late times in the heterogeneous flow field simulations. We look at three common flow deformation metrics that describe the enhancement of mixing in the flow due to velocity gradients: the Okubo-Weiss parameter (θ ), the largest eigenvalue of the Cauchy-Green strain tensor (λC), and the finite-time Lyapunov exponent (Λ ). Strong mixing regions in the heterogeneous flow field identified by these metrics were found to correspond to regions with higher numbers of reactions, but the infrequency of these regions compared to the large numbers of reactions occurring elsewhere in the domain imply that these strong mixing regions are insufficient in explaining the observed near well-mixed behavior. Since it was found that reactive transport in these heterogeneous flows could overcome the effects of incomplete mixing, we also search for a closure for the mean concentration. The conservative quantity u2¯, where u =CA-CB , was found to predict the late time scaling of the mean concentration, i.e., Ci¯˜u2¯ .

Stratification during evaporative assembly of multicomponent nanoparticle films

DOE PAGES

Liu, Xiao; Liu, Weiping; Carr, Amanda J.; ...

2018-01-03

Multicomponent coatings with layers comprising different functionalities are of interest for a variety of applications, including electronic devices, energy storage, and biomaterials. Rather than creating such a film using multiple deposition steps, we explore a single-step method to create such films by varying the particle Peclet numbers, Pe. Our hypothesis, based on recent theoretical descriptions of the stratification process, is that by varying particle size and evaporation rate such that Pe of large and small particles are above and below unity, we can create stratified films of polymeric and inorganic particles. In this paper, we present AFM on the surfacemore » composition of films comprising poly(styrene) nanoparticles (diameter 25–90 nm) and silica nanoparticles (diameter 8–14 nm). Previous studies on films containing both inorganic and polymeric particles correspond to large Pe values (e.g., 120–460), while we utilize Pe ~ 0.3–4, enabling us to test theories that have been developed for different regimes of Pe. We demonstrate evidence of stratification and effect of the Pe ratio, although our results agree only qualitatively with theory. Finally, our results also provide validation of recent theoretical descriptions of the film drying process that predict different regimes for large-on-top and small-on-top stratification.« less

Dynamics of hard sphere colloidal dispersions

NASA Technical Reports Server (NTRS)

Zhu, J. X.; Chaikin, Paul M.; Phan, S.-E.; Russel, W. B.

1994-01-01

Our objective is to perform on homogeneous, fully equilibrated dispersions the full set of experiments characterizing the transition from fluid to solid and the properties of the crystalline and glassy solid. These include measurements quantifying the nucleation and growth of crystallites, the structure of the initial fluid and the fully crystalline solid, and Brownian motion of particles within the crystal, and the elasticity of the crystal and the glass. Experiments are being built and tested for ideal microgravity environment. Here we describe the ground based effort, which exploits a fluidized bed to create a homogeneous, steady dispersion for the studies. The differences between the microgravity environment and the fluidized bed is gauged by the Peclet number Pe, which measures the rate of convection/sedimentation relative to Brownian motion. We have designed our experiment to accomplish three types of measurements on hard sphere suspensions in a fluidized bed: the static scattering intensity as a function of angle to determine the structure factor, the temporal autocorrelation function at all scattering angles to probe the dynamics, and the amplitude of the response to an oscillatory forcing to deduce the low frequency viscoelasticity. Thus the scattering instrument and the colloidal dispersion were chosen such as that the important features of each physical property lie within the detectable range for each measurement.

Non-equilibrium Stokes-Einstein relation via active microrheology of hydrodynamically interacting suspensions

NASA Astrophysics Data System (ADS)

Chu, Henry; Zia, Roseanna

In our recently developed non-equilibrium Stokes-Einstein relation, we showed that, in the absence of hydrodynamic interactions, the stress in a suspension is given by a balance between fluctuation and dissipation. Here, we generalize our theory for systems of hydrodynamically interacting colloids, via active microrheology, where motion of a Brownian probe through the medium reveals rheological properties. The strength of probe forcing compared to the entropic restoring force defines a Peclet number, Pe. In the absence of hydrodynamics, the first normal stress difference and the osmotic pressure scale as Pe4 and Pe2 respectively when probe forcing is weak, and uniformly as Pe for strong probe forcing. As hydrodynamics become important, interparticle forces give way to lubrication interactions. Hydrodynamic coupling leads to a new low-Pe scaling of the first normal stress difference and the osmotic pressure as Pe2, and high-Pe scaling as Peδ, where 0.799 <= δ <= 1 as hydrodynamics vary from strong to weak. For the entire range of the strength of hydrodynamic interactions and probe forcing, the new phenomenological theory is shown to agree with standard micromechanical definitions of the stress. We further draw a connection between the stress and the energy storage in a suspension, and the entropic nature of such storage is identified.

Development and Implementation of a Transport Method for the Transport and Reaction Simulation Engine (TaRSE) based on the Godunov-Mixed Finite Element Method

USGS Publications Warehouse

James, Andrew I.; Jawitz, James W.; Munoz-Carpena, Rafael

2009-01-01

A model to simulate transport of materials in surface water and ground water has been developed to numerically approximate solutions to the advection-dispersion equation. This model, known as the Transport and Reaction Simulation Engine (TaRSE), uses an algorithm that incorporates a time-splitting technique where the advective part of the equation is solved separately from the dispersive part. An explicit finite-volume Godunov method is used to approximate the advective part, while a mixed-finite element technique is used to approximate the dispersive part. The dispersive part uses an implicit discretization, which allows it to run stably with a larger time step than the explicit advective step. The potential exists to develop algorithms that run several advective steps, and then one dispersive step that encompasses the time interval of the advective steps. Because the dispersive step is computationally most expensive, schemes can be implemented that are more computationally efficient than non-time-split algorithms. This technique enables scientists to solve problems with high grid Peclet numbers, such as transport problems with sharp solute fronts, without spurious oscillations in the numerical approximation to the solution and with virtually no artificial diffusion.

Stratification during evaporative assembly of multicomponent nanoparticle films

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

Liu, Xiao; Liu, Weiping; Carr, Amanda J.

Multicomponent coatings with layers comprising different functionalities are of interest for a variety of applications, including electronic devices, energy storage, and biomaterials. Rather than creating such a film using multiple deposition steps, we explore a single-step method to create such films by varying the particle Peclet numbers, Pe. Our hypothesis, based on recent theoretical descriptions of the stratification process, is that by varying particle size and evaporation rate such that Pe of large and small particles are above and below unity, we can create stratified films of polymeric and inorganic particles. In this paper, we present AFM on the surfacemore » composition of films comprising poly(styrene) nanoparticles (diameter 25–90 nm) and silica nanoparticles (diameter 8–14 nm). Previous studies on films containing both inorganic and polymeric particles correspond to large Pe values (e.g., 120–460), while we utilize Pe ~ 0.3–4, enabling us to test theories that have been developed for different regimes of Pe. We demonstrate evidence of stratification and effect of the Pe ratio, although our results agree only qualitatively with theory. Finally, our results also provide validation of recent theoretical descriptions of the film drying process that predict different regimes for large-on-top and small-on-top stratification.« less

Solution of the advection-dispersion equation in two dimensions by a finite-volume Eulerian-Lagrangian localized adjoint method

USGS Publications Warehouse

Healy, R.W.; Russell, T.F.

1998-01-01

We extend the finite-volume Eulerian-Lagrangian localized adjoint method (FVELLAM) for solution of the advection-dispersion equation to two dimensions. The method can conserve mass globally and is not limited by restrictions on the size of the grid Peclet or Courant number. Therefore, it is well suited for solution of advection-dominated ground-water solute transport problems. In test problem comparisons with standard finite differences, FVELLAM is able to attain accurate solutions on much coarser space and time grids. On fine grids, the accuracy of the two methods is comparable. A critical aspect of FVELLAM (and all other ELLAMs) is evaluation of the mass storage integral from the preceding time level. In FVELLAM this may be accomplished with either a forward or backtracking approach. The forward tracking approach conserves mass globally and is the preferred approach. The backtracking approach is less computationally intensive, but not globally mass conservative. Boundary terms are systematically represented as integrals in space and time which are evaluated by a common integration scheme in conjunction with forward tracking through time. Unlike the one-dimensional case, local mass conservation cannot be guaranteed, so slight oscillations in concentration can develop, particularly in the vicinity of inflow or outflow boundaries. Published by Elsevier Science Ltd.

A correction procedure for thermally two-way coupled point-particles

NASA Astrophysics Data System (ADS)

Horwitz, Jeremy; Ganguli, Swetava; Mani, Ali; Lele, Sanjiva

2017-11-01

Development of a robust procedure for the simulation of two-way coupled particle-laden flows remains a challenge. Such systems are characterized by O(1) or greater mass of particles relative to the fluid. The coupling of fluid and particle motion via a drag model means the undisturbed fluid velocity evaluated at the particle location (which is needed in the drag model) is no longer equal to the interpolated fluid velocity at the particle location. The same issue arises in problems of dispersed flows in the presence of heat transfer. The heat transfer rate to each particle depends on the difference between the particle's temperature and the undisturbed fluid temperature. We borrow ideas from the correction scheme we have developed for particle-fluid momentum coupling by developing a procedure to estimate the undisturbed fluid temperature given the disturbed temperature field created by a point-particle. The procedure is verified for the case of a particle settling under gravity and subject to radiation. The procedure is developed in the low Peclet, low Boussinesq number limit, but we will discuss the applicability of the same correction procedure outside of this regime when augmented by appropriate drag and heat exchange correlations. Supported by DOE, J. H. Supported by NSF GRF

Is thermal dispersivity significant for the use of heat as a tracer?

NASA Astrophysics Data System (ADS)

Rau, G. C.; Andersen, M. S.; Acworth, I.

2011-12-01

Heat profiles are regularly used to estimate sediment thermal parameters and to quantify vertical water flow velocity in fully saturated porous media. However, it has been pointed out by several authors that there is disagreement regarding the use of thermal dispersivity in heat transport models [e.g. Anderson, 2005]. Some researchers argue that this term should be treated analogous to solute transport [e.g. de Marsily, 1986], whilst others state that because heat diffusion is much faster than solute diffusion the dispersivity term can be neglected [e.g. Ingebritsen and Sanford, 1998]. This issue has never been properly addressed experimentally for environmentally relevant conditions. In order to address this question a hydraulic laboratory experiment was designed to investigate heat transport for different steady-state uniform flow velocities in the Darcy range (between 0 and 100 m/d) through homogeneous sand. For each flow velocity a point heat source at the center of the tank was instantaneously activated, and the thermal response was measured at 27 different locations using high resolution temperature probes. For the same flow velocities, a solute slug was injected in the center of the tank and the solute slug breakthrough was measured using 3 fluid EC sensors at different distances downstream of the injection point. This enabled direct comparison of solute and heat transport under identical conditions. The recorded temperature time-series data were used to calculate the thermal properties of the sand for conduction only, and estimate water flow velocity and thermal dispersion. The recorded EC time-series data were used to independently estimate water flow velocity but also solute dispersivity. The analytical solution for the solute transport case [Hunt, 1978] was adapted for heat transport and extended to account for slightly non-ideal experiment conditions. Velocity results independently derived from solute and heat show a discrepancy of up to 20%. The reason for this is not clear. Furthermore, the results show that thermal dispersivity can best be approximated with a square dependency on flow velocity. This agrees with earlier experiments in ideal materials by Green et al. [1964] as well as theoretical derivations [Kaviany, 1995]. However, this is in contrast to the linear dispersion model which has been adapted from solute transport and is commonly used in groundwater studies. The experimental results can be visualized in a conceptual plot devised by Bear [1972] for solute dispersion data (Figure 1). From this it becomes clear that the heat and solute transport Peclet numbers differs by several orders of magnitude for the same flow velocity and material because diffusion of heat is much faster than solute diffusion. As a result, the same Darcy flow range covers a different Peclet number range in heat transport and solute transport. This explains the controversy in the hydrologic community regarding the use of thermal dispersivity in transport models. In summary, for this experiment thermal dispersivity can be neglected when thermal Pe < 0.5, but should be considered for Pe > 0.5 with a square dependency on velocity.

Quantification of chaotic strength and mixing in a micro fluidic system

NASA Astrophysics Data System (ADS)

Kim, Ho Jun; Beskok, Ali

2007-11-01

Comparative studies of five different techniques commonly employed to identify the chaotic strength and mixing efficiency in micro fluidic systems are presented to demonstrate the competitive advantages and shortcomings of each method. The 'chaotic electroosmotic stirrer' of Qian and Bau (2002 Anal. Chem. 74 3616-25) is utilized as the benchmark case due to its well-defined flow kinematics. Lagrangian particle tracking methods are utilized to study particle dispersion in the conceptual device using spectral element and fourth-order Runge-Kutta discretizations in space and time, respectively. Stirring efficiency is predicted using the stirring index based on the box counting method, and Poincaré sections are utilized to identify the chaotic and regular regions under various actuation conditions. Finite time Lyapunov exponents are calculated to quantify the chaotic strength, while the probability density function of the stretching field is utilized as an alternative method to demonstrate the statistical analysis of chaotic and partially chaotic cases. Mixing index inverse, based on the standard deviation of scalar species distribution, is utilized as a metric to quantify the mixing efficiency. Series of numerical simulations are performed by varying the Peclet number (Pe) at fixed kinematic conditions. The mixing time (tm) is characterized as a function of the Pe number, and tm ~ ln(Pe) scaling is demonstrated for fully chaotic cases, while tm ~ Peα scaling with α ≈ 0.33 and α = 0.5 are observed for partially chaotic and regular cases, respectively. Employing the aforementioned techniques, optimum kinematic conditions and the actuation frequency of the stirrer that result in the highest mixing/stirring efficiency are identified.

Solutal Convection Around Growing Protein Crystal and Diffusional Purification in Space

NASA Technical Reports Server (NTRS)

Chernov, A. A.; Lee, C. P.

2002-01-01

This work theoretically addressed two subjects: 1) onset of convection, 2) distribution of impurities. Onset of convection was considered analytically and numerically. Crystal growth was characterized by slow surface incorporation kinetics, i.e. growth kinetic coefficient beta (cm/s) small as compared to the typical bulk diffusion rate, D(sub 1)/h, where D(sub 1) is diffusivity of major crystallizing protein and h is the crystal size. Scaling type analysis predicted two laws on how the convection rate, v, essentially the Peclet number, Pe exactly equal to vh/D(sub 1), depends on dimensionless kinetic coefficient a exactly equal to beta h/D(sub 1). Namely: Pe = C(sub 2/5)(aRa(sup 2/5)) and Pe = C(sub 1) aRa. Here, Reynolds number Ra = rho(sub 1)(sup 0)gh(sup 3)(rho(sub p) - rho(sub w))/rho(sup p)rho(sub 1)vD(sub 1), v being solution viscosity. The constants C(sub 2/5), exactly equal to 0.28 and C(sub 1) exactly equal to 10(exp -2) found from the full scale computer simulation for a cylindrical crystal inside big cylindrical vessel. The linear boundary conditions connecting protein and impurity concentration at the interface with the flux to/from the interface was applied. No-slip condition for Navier-Shocker equations was employed. With these conditions, flow and concentration distributions were calculated. Validity of the Pe(Ra) dependencies follows for wide range of parameters for which numerical calculations have been accomplished and presented by various points.

Linear instabilities of a planar liquid sheet in a static electric field for intermediate relaxation and convection of surface charges

NASA Astrophysics Data System (ADS)

Yoshinaga, Takao

2018-04-01

Linear temporal instabilities of a two-dimensional planar liquid sheet in a static electric field are investigated when the relaxation and convection of surface electric charges are considered. Both viscous sheet liquid and inviscid surrounding liquid are placed between two parallel sheath walls, on which an external electric field is imposed. In particular, effects of the electric Peclet number {Pe} (charge relaxation time/convection time) and the electric Euler number Λ (electric pressure/liquid inertial) on the instabilities are emphasized for the symmetric and antisymmetric deformations of the sheet. It is found that the unstable mode is composed of the aerodynamic and electric modes, which are merged with each other for the symmetric deformation and separated for the antisymmetric deformation. For the symmetric deformation, the combined mode is more destabilized with the decrease of {Pe} and the increase of Λ. On the other hand, for the antisymmetric deformation, the electric mode is more destabilized and the aerodynamic mode is left unchanged with the decrease of {Pe}, while the electric mode is more destabilized but the aerodynamic mode is more stabilized with the increase of Λ. It is also found for both symmetric and antisymmetric deformations that the instabilities are most suppressed when {σ }R≃ 1/{ε }P ({σ }R: conductivity ratio of the surrounding to the sheet liquid, {ε }P: permittivity ratio of the sheet to the surrounding liquid), whose trend of the instabilities is more enhanced with the decrease of {Pe} except for vanishingly small {Pe}.

Pore scale investigation of salt precipitation inside drying porous media resolved by 4D X-ray Microscopy Imaging

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.

2016-12-01

Precipitation and deposition of salts in porous media is important in many natural processes as well as industrial and environmental applications since it can modify the structure and transport properties of porous media. In the presence of soluble salt in water during evaporation from porous media, salt is transported by convection induced by capillary liquid flow toward the evaporating surface where it accumulates, whereas diffusion tends to spread the salt and homogenize concentrations in space. Therefore, the competition between the convection and diffusion (characterized by Peclet number) affects the dynamics of salt distribution in porous media. As shown in previous studies (1-3) salt crust thickness and its coverage on the surface are highly influenced by the pore size distribution on the surface and active evaporation spots. In the current study, we focus on the precipitation dynamics and pattern during diffusion-driven evaporation period (the so-called stage-2 of evaporation) when the surface is dried and vaporization plane moves below the surface. Therefore, precipitation occurs inside the porous media during this period. To investigate the details of this process, 4D X-ray Microscopy was utilized. To do so, a packed bed of silica sand was saturated with 4 Molal NaCl solution and X-ray Microscopy was used to image the sample at well-defined time intervals during the evaporation process to provide pore scale information on evaporation and precipitation dynamics. The resulted 3-D pore-scale images were segmented to quantify the evaporative water losses and the dynamics and patterns of salt precipitation inside porous media with particular focus on the characterization of the processes occurring during stage-2 evaporation affecting the precipitation dynamics. [1] Norouzi Rad, M., N. Shokri, A. Keshmiri, P. Withers (2015), Effects of grain and pore size on salt precipitation during evaporation from porous media: A pore-scale investigation, Trans. Porous. Med., 110(2), 281-294. [2] Norouzi Rad, M., N. Shokri (2014), Effects of grain angularity on NaCl precipitation in porous media during evaporation, Water Resour. Res., 50, 9020-9030. [3] Norouzi Rad, M., N. Shokri, M. Sahimi (2013), Pore-Scale Dynamics of Salt Precipitation in Drying Porous Media, Phys. Rev. E, 88, 032404.

Modified Mason number for charged paramagnetic colloidal suspensions

NASA Astrophysics Data System (ADS)

Du, Di; Hilou, Elaa; Biswal, Sibani Lisa

2016-06-01

The dynamics of magnetorheological fluids have typically been described by the Mason number, a governing parameter defined as the ratio between viscous and magnetic forces in the fluid. For most experimental suspensions of magnetic particles, surface forces, such as steric and electrostatic interactions, can significantly influence the dynamics. Here we propose a theory of a modified Mason number that accounts for surface forces and show that this modified Mason number is a function of interparticle distance. We demonstrate that this modified Mason number is accurate in describing the dynamics of a rotating pair of paramagnetic colloids of identical or mismatched sizes in either high or low salt solutions. The modified Mason number is confirmed to be pseudoconstant for particle pairs and particle chains undergoing a stable-metastable transition during rotation. The interparticle distance term can be calculated using theory or can be measured experimentally. This modified Mason number is more applicable to magnetorheological systems where surface forces are not negligible.

An implicit dispersive transport algorithm for the US Geological Survey MOC3D solute-transport model

USGS Publications Warehouse

Kipp, K.L.; Konikow, Leonard F.; Hornberger, G.Z.

1998-01-01

This report documents an extension to the U.S. Geological Survey MOC3D transport model that incorporates an implicit-in-time difference approximation for the dispersive transport equation, including source/sink terms. The original MOC3D transport model (Version 1) uses the method of characteristics to solve the transport equation on the basis of the velocity field. The original MOC3D solution algorithm incorporates particle tracking to represent advective processes and an explicit finite-difference formulation to calculate dispersive fluxes. The new implicit procedure eliminates several stability criteria required for the previous explicit formulation. This allows much larger transport time increments to be used in dispersion-dominated problems. The decoupling of advective and dispersive transport in MOC3D, however, is unchanged. With the implicit extension, the MOC3D model is upgraded to Version 2. A description of the numerical method of the implicit dispersion calculation, the data-input requirements and output options, and the results of simulator testing and evaluation are presented. Version 2 of MOC3D was evaluated for the same set of problems used for verification of Version 1. These test results indicate that the implicit calculation of Version 2 matches the accuracy of Version 1, yet is more efficient than the explicit calculation for transport problems that are characterized by a grid Peclet number less than about 1.0.

Two-dimensional patterns in bacterial veils arise from self-generated, three-dimensional fluid flows.

PubMed

Cogan, N G; Wolgemuth, C W

2011-01-01

The behavior of collections of oceanic bacteria is controlled by metabolic (chemotaxis) and physical (fluid motion) processes. Some sulfur-oxidizing bacteria, such as Thiovulum majus, unite these two processes via a material interface produced by the bacteria and upon which the bacteria are transiently attached. This interface, termed a bacterial veil, is formed by exo-polymeric substances (EPS) produced by the bacteria. By adhering to the veil while continuing to rotate their flagella, the bacteria are able to exert force on the fluid surroundings. This behavior induces a fluid flow that, in turn, causes the bacteria to aggregate leading to the formation of a physical pattern in the veil. These striking patterns are very similar in flavor to the classic convection instability observed when a shallow fluid is heated from below. However, the physics are very different since the flow around the veil is mediated by the bacteria and affects the bacterial densities. In this study, we extend a model of a one-dimensional veil in a two-dimensional fluid to the more realistic two-dimensional veil in a three-dimensional fluid. The linear stability analysis indicates that the Peclet number serves as a bifurcation parameter, which is consistent with experimental observations. We also solve the nonlinear problem numerically and are able to obtain patterns that are similar to those observed in the experiments.

Mechanistic principles of colloidal crystal growth by evaporation-induced convective steering.

PubMed

Brewer, Damien D; Allen, Joshua; Miller, Michael R; de Santos, Juan M; Kumar, Satish; Norris, David J; Tsapatsis, Michael; Scriven, L E

2008-12-02

We simulate evaporation-driven self-assembly of colloidal crystals using an equivalent network model. Relationships between a regular hexagonally close-packed array of hard, monodisperse spheres, the associated pore space, and selectivity mechanisms for face-centered cubic microstructure propagation are described. By accounting for contact line rearrangement and evaporation at a series of exposed menisci, the equivalent network model describes creeping flow of solvent into and through a rigid colloidal crystal. Observations concerning colloidal crystal growth are interpreted in terms of the convective steering hypothesis, which posits that solvent flow into and through the pore space of the crystal may play a major role in colloidal self-assembly. Aspects of the convective steering and deposition of high-Peclet-number rigid spherical particles at a crystal boundary are inferred from spatially resolved solvent flow into the crystal. Gradients in local flow through boundary channels were predicted due to the channels' spatial distribution relative to a pinned free surface contact line. On the basis of a uniform solvent and particle flux as the criterion for stability of a particular growth plane, these network simulations suggest the stability of a declining {311} crystal interface, a symmetry plane which exclusively propagates fcc microstructure. Network simulations of alternate crystal planes suggest preferential growth front evolution to the declining {311} interface, in consistent agreement with the proposed stability mechanism for preferential fcc microstructure propagation in convective assembly.

Microfluidic droplet-based liquid-liquid extraction.

PubMed

Mary, Pascaline; Studer, Vincent; Tabeling, Patrick

2008-04-15

We study microfluidic systems in which mass exchanges take place between moving water droplets, formed on-chip, and an external phase (octanol). Here, no chemical reaction takes place, and the mass exchanges are driven by a contrast in chemical potential between the dispersed and continuous phases. We analyze the case where the microfluidic droplets, occupying the entire width of the channel, extract a solute-fluorescein-from the external phase (extraction) and the opposite case, where droplets reject a solute-rhodamine-into the external phase (purification). Four flow configurations are investigated, based on straight or zigzag microchannels. Additionally to the experimental work, we performed two-dimensional numerical simulations. In the experiments, we analyze the influence of different parameters on the process (channel dimensions, fluid viscosities, flow rates, drop size, droplet spacing, ...). Several regimes are singled out. In agreement with the mass transfer theory of Young et al. (Young, W.; Pumir, A.; Pomeau, Y. Phys. Fluids A 1989, 1, 462), we find that, after a short transient, the amount of matter transferred across the droplet interface grows as the square root of time and the time it takes for the transfer process to be completed decreases as Pe-2/3, where Pe is the Peclet number based on droplet velocity and radius. The numerical simulation is found in excellent consistency with the experiment. In practice, the transfer time ranges between a fraction and a few seconds, which is much faster than conventional systems.

Role of Marangoni stress during breakup of surfactant-covered liquid threads: Reduced rates of thinning and microthread cascades

NASA Astrophysics Data System (ADS)

Kamat, Pritish M.; Wagoner, Brayden W.; Thete, Sumeet S.; Basaran, Osman A.

2018-04-01

Adsorption onto and lowering of surface tension σ of fluid interfaces by surfactants is exploited in drop formation (e.g., inkjet printing) where a thinning liquid thread (radius h ) connects an about-to-form drop to the liquid that remains hanging from the nozzle when the former falls from it. Surfactants can affect thread pinch-off in two ways: first, by lowering σ , they lower capillary pressure (σ /h ), and second, as surfactant concentration along the interface can be nonuniform, they cause the interface to be subjected to a surface tension gradient or Marangoni stress. Recent studies show that the location where the thread breaks is devoid of surfactant, and others assert that the influence of Marangoni stress on pinch-off is negligible. We demonstrate by simulations and experiments that surfactants play a major role in drop formation and that Marangoni stresses acting near but not at the pinch point give rise to reduced rates of thread thinning and formation of multiple microthreads that distinguish pinch-off of surfactant-covered threads from surfactant-free ones. Thinning at finite Reynolds and Peclet numbers, Re and Pe, is shown to exhibit intermediate scaling regimes that have heretofore only been observed during pinch-off of threads undergoing creeping flow (Re=0 ) while convection of surfactant is weak compared to its diffusion (Pe<1 ).

Explosion bomb measurements of ethanol-air laminar gaseous flame characteristics at pressures up to 1.4 MPa

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

Bradley, D.; Lawes, M.; Mansour, M.S.

2009-07-15

The principal burning characteristics of a laminar flame comprise the fuel vapour pressure, the laminar burning velocity, ignition delay times, Markstein numbers for strain rate and curvature, the stretch rates for the onset of flame instabilities and of flame extinction for different mixtures. With the exception of ignition delay times, measurements of these are reported and discussed for ethanol-air mixtures. The measurements were in a spherical explosion bomb, with central ignition, in the regime of a developed stable, flame between that of an under or over-driven ignition and that of an unstable flame. Pressures ranged from 0.1 to 1.4 MPa,more » temperatures from 300 to 393 K, and equivalence ratios were between 0.7 and 1.5. It was important to ensure the relatively large volume of ethanol in rich mixtures at high pressures was fully evaporated. The maximum pressure for the measurements was the highest compatible with the maximum safe working pressure of the bomb. Many of the flames soon became unstable, due to Darrieus-Landau and thermo-diffusive instabilities. This effect increased with pressure and the flame wrinkling arising from the instabilities enhanced the flame speed. Both the critical Peclet number and the, more rational, associated critical Karlovitz stretch factor were evaluated at the onset of the instability. With increasing pressure, the onset of flame instability occurred earlier. The measured values of burning velocity are expressed in terms of their variations with temperature and pressure, and these are compared with those obtained by other researchers. Some comparisons are made with the corresponding properties for iso-octane-air mixtures. (author)« less

Design and synthesis of magnetic nanoparticles with gold shells for single particle optical tracking

NASA Astrophysics Data System (ADS)

Lim, Jitkang

The design, synthesis, and characterization of iron oxide core, gold shell nanoparticles are studied in this thesis. Firstly, nanoparticles with 18 +/- 1.7 nm diameter iron oxide cores with ˜5 nm thick gold shells were synthesized via a new seed-mediated electroless deposition method. The nanoparticles were superparamagnetic at room temperature and could be reversibly collected by a permanent magnet. These nanoparticles displayed a sharp localized surface plasmon resonance peak at 605 nm, as predicted by scattering theory, and their large scattering cross-section allowed them to be individually resolved in darkfield optical microscopy while undergoing Brownian motion in aqueous suspension. Later, commercially available 38 +/- 3.8 nm diameter spherical iron oxide nanoparticles (from Ocean Nanotech, Inc) were employed to make core-shell particles. These particles were decorated with cationic poly(diallyldimethylammonium chloride) (PDDA) which further promotes the attachment of small gold clusters. After gold seeding, the average hydrodynamic diameter of the core-shell particles is 172 +/- 65.9 nm. The magnetophoretic motion of these particles was guided by a piece of magnetized mu-metal. Individual particle trajectories were observed by darkfield optical microscopy. The typical magnetophoretic velocity achieved was within the range of 1--10 mum/sec. Random walk analysis performed on these particles while undergoing Brownian motion confirmed that individual particles were indeed being imaged. The particle size variation within the observed sample obtained through random walk analysis was within the size distribution obtained by dynamic light scattering. When the current to the solenoid used to magnetize the mu-metal was turned off, all the collected core-shell particles were readily redispersed by diffusion back into the surrounding environment. A Peclet number analysis was performed to probe the convective motion of nanospheres and nanorods under the influence of magnetophoresis and diffusion. Under most circumstances, magnetophoretic behavior dominates diffusion for nanorods, as the magnetic field lines tend to align the magnetic moment along the rod axis. The synthesis and dispersion of fluorophore-tagged nanorods are described. Fluorescence microscopy was employed to image the nanorod motion in a magnetic field gradient. The preliminary experimental data are consistent with the Peclet number analysis. Lastly, the colloidal stability of iron oxide core, gold shell nanoparticles in high ionic strength media was investigated. Such particles are sufficiently charged to be stable against flocculation without modification in low ionic strength media, but they require surface modification to be stably dispersed in elevated ionic strength media that are appropriate for biotechnological applications. Dynamic light scattering and ultraviolet-visible spectrophotometry were used to monitor the colloidal stability of core-shell particles in pH 7.4, 150 mM ionic strength phosphate buffered saline (PBS). While uncoated particles flocculated immediately upon being introduced into PBS, core-shell particles with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than five days in PBS. Adsorbed dextran allowed flocculation that was limited to the formation of small clusters, while poly(ethylene glycol) homopolymers ranging in molecular weight from 6,000 to 100,000 were ineffective steric stabilizers. The effectiveness of adsorbed Pluronic copolymers as steric stabilizers was interpreted in terms of the measured adsorbed layer thickness and extended DLVO theory predictions of the interparticle interactions.

Scaling of normalized mean energy and scalar dissipation rates in a turbulent channel flow

NASA Astrophysics Data System (ADS)

Abe, Hiroyuki; Antonia, Robert Anthony

2011-05-01

Non-dimensional parameters for the mean energy and scalar dissipation rates Cɛ and Cɛθ are examined using direct numerical simulation (DNS) data obtained in a fully developed turbulent channel flow with a passive scalar (Pr = 0.71) at several values of the Kármán (Reynolds) number h+. It is shown that Cɛ and Cɛθ are approximately equal in the near-equilibrium region (viz., y+ = 100 to y/h = 0.7) where the production and dissipation rates of either the turbulent kinetic energy or scalar variance are approximately equal and the magnitudes of the diffusion terms are negligibly small. The magnitudes of Cɛ and Cɛθ are about 2 and 1 in the logarithmic and outer regions, respectively, when h+ is sufficiently large. The former value is about the same for the channel, pipe, and turbulent boundary layer, reflecting the similarity between the mean velocity and temperature distributions among these three canonical flows. The latter value is, on the other hand, about twice as large as in homogeneous isotropic turbulence due to the existence of the large-scale u structures in the channel. The behaviour of Cɛ and Cɛθ impacts on turbulence modeling. In particular, the similarity between Cɛ and Cɛθ leads to a simple relation for the scalar variance to turbulent kinetic energy time-scale ratio, an important ingredient in the eddy diffusivity model. This similarity also yields a relation between the Taylor and Corrsin microscales and analogous relations, in terms of h+, for the Taylor microscale Reynolds number and Corrsin microscale Peclet number. This dependence is reasonably well supported by both the DNS data at small to moderate h+ and the experimental data of Comte-Bellot [Ph. D. thesis (University of Grenoble, 1963)] at larger h+. It does not however apply to a turbulent boundary layer where the mean energy dissipation rate, normalized on either wall or outer variables, is about 30% larger than for the channel flow.

25 CFR 166.308 - Can the number of animals and/or season of use be modified on the permitted land if I graze...

Code of Federal Regulations, 2012 CFR

2012-04-01

... 25 Indians 1 2012-04-01 2011-04-01 true Can the number of animals and/or season of use be modified... WATER GRAZING PERMITS Land and Operations Management § 166.308 Can the number of animals and/or season... on-and-off grazing permit? Yes. The number of animals and/or season of use may be modified on...

Glossosoma nigrior (Trichoptera: Glossosomatidae) respiration in moving fluid.

PubMed

Morris, Mark W L; Hondzo, Miki

2013-08-15

Laboratory measurements of dissolved oxygen (DO) uptake by Glossosoma nigrior Banks were conducted in a sealed, recirculating flume under variable fluid flow velocities. Measurements were performed in similar water temperatures, DO concentrations and fluid flow velocities to field conditions in the stream where the larvae were obtained. Total oxygen uptake by both cased larvae and corresponding cases without larvae were quantified. An increased fluid flow velocity corresponded to an increased larval DO uptake rate. Oxygen uptake by the larval cases alone was not as sensitive to changes in the Peclet (Pe) number, the dimensionless ratio of advective to diffusive DO transport, as uptake by larvae themselves. The flux of DO to larvae and their cases was up to seven times larger in a moving fluid in comparison to non-moving fluid conditions in the proximity of larvae for 087, larvae typically remained in their cases. This indicates that oxygen delivery to the larvae at low Pe is insufficient to satisfy the respiratory demands of cased larvae.

Design and simulation of the micromixer with chaotic advection in twisted microchannels.

PubMed

Jen, Chun-Ping; Wu, Chung-Yi; Lin, Yu-Cheng; Wu, Ching-Yi

2003-05-01

Chaotic mixers with twisted microchannels were designed and simulated numerically in the present study. The phenomenon whereby a simple Eulerian velocity field may generate a chaotic response in the distribution of a Lagrangian marker is termed chaotic advection. Dynamic system theory indicates that chaotic particle motion can occur when a velocity field is either two-dimensional and time-dependent, or three-dimensional. In the present study, micromixers with three-dimensional structures of the twisted microchannel were designed in order to induce chaotic mixing. In addition to the basic T-mixer, three types of micromixers with inclined, oblique and wavelike microchannels were investigated. In the design of each twisted microchannel, the angle of the channels' bottoms alternates in each subsection. When the fluids enter the twisted microchannels, the flow sways around the varying structures within the microchannels. The designs of the twisted microchannels provide a third degree of freedom to the flow field in the microchannel. Therefore, chaotic regimes that lead to chaotic mixing may arise. The numerical results indicate that mixing occurs in the main channel and progressively larger mixing lengths are required as the Peclet number increased. The swaying of the flow in the twisted microchannel causes chaotic advection. Among the four micromixer designs, the micromixer with the inclined channel most improved mixing. Furthermore, using the inclined mixer with six subsections yielded optimum performance, decreasing the mixing length by up to 31% from that of the basic T-mixer.

Dispersion in 2D network: Effects of mixing rule at nodes and molecular diffusion

NASA Astrophysics Data System (ADS)

Wang, Y.; Tao, Q.; Li, M.

2017-12-01

We simulate solute transport in 2D network backbone characterized by pore connectivity and pore heterogeneity by particle-tracking method. In order to ensure the dispersion coefficient reaching an asymptotic value, we upscale dispersion from pore-scale to meter-scale by using periodic boundary condition. As comparison, two different flow mechanisms without or with dispersion in a capillary tube, namely mean flow and Taylor-Aris dispersion, are introduced to investigate the evolution of solute spreading. The longitudinal dispersion coefficient DLM without dispersion in a pipe can roughly be regarded as a parameter to quantify the impact of microscopic structure of porous media on solute spreading, which is smaller than that value DL of Taylor-Aris dispersion. The difference between them decreases with the enhancement of the disorder. The mixing rule at nodes has a minor effect on longitudinal spreading, but has a significant effect on transverse spreading, especially for the nearly homogeneous media. An increase of the disorder in network achieved by increasing pore size heterogeneity or/and decreasing pore connectivity diminishes the difference between two mixing rules. Besides, the evolution of longitudinal dispersion coefficient over diffusion presents three different patterns at different velocities for homogenous media, such as monotonically increasing trend, decreasing first and then increasing trend and monotonically decreasing trend. But all are replaced by power law for a high disorder. The simulation results also accurately predict the experimental dependence of the longitudinal coefficient on Peclet number Pe.

Energy characteristics of the CO2 laser cutting of thick steel sheets

NASA Astrophysics Data System (ADS)

Orishich, A. M.

2012-01-01

In the present paper the scaling laws for the oxygen-assisted laser cutting of low-carbon steel of 5-25 mm is studied experimentally. No dross and minimal roughness of the cut surface were chosen as criteria of quality. The paper also studies the possibility to describe the cutting process by the similarity method and as ratios between dimensionless variables. Normalized power W/ktT, normalized velocity Vcb/a (Peclet number) and kerf width have special optimum numb. Formulas were obtained to determine the optimum values of the laser power and cutting speed for the given sheet thickness. The energy balance of the oxygen-assisted laser cutting is studied experimentally at these optimum parameters. The absorbed laser energy, heat conduction losses and cut width were measured experimentally, and then the energy of exothermic reaction of oxidation was found from the balance equation. To define the integral coefficient of absorption, the laser power was measured on the cutting channel exit during the cutting. The heat conduction losses were measured by the calorimetric method. It has been established that the absorbed laser energy, oxidation energy, thermal losses and melting enthalpy related to a sheet thickness unit, do not depend on the sheet thickness at the cutting with the minimal roughness. The results enable to determine the fraction of the oxidized iron in the melt and thermal efficiency at the cutting with the minimal roughness. The share of the oxidation reaction energy is 50-60% in the total contributed energy.

On the Concentration Gradient across a Spherical Source Washed by Slow Flow

PubMed Central

Jaffe, Lionel

1965-01-01

A model has been numerically analyzed to help interpret the orienting effects of flow upon cells. The model is a sphere steadily and uniformly emitting a diffusible stuff into a medium otherwise free of it and moving past with Stokes flow. Its properties depend primarily upon the Peclet number, Pe, equal to a · v∞/D, i.e., the sphere's radius, a, times the free stream speed, v∞, over the stuff's diffusion constant, D. As Pe rises, and washing becomes more effective, the average surface concentration, C̄s a falls (Figs. 2 and 5) and the residual material becomes relatively concentrated on the sphere's lee pole (Figs. 2 and 4). Specifically, as Pe rises from 0.1 to 1, the relative concentration gradient, G, rises from 0.7 to 5.0 per cent and to the point where it is rising at about 8 per cent per decade; by Pe 1000, G = 22.1 per cent. From Pe 1 through 1000, G/(1 - C̄s a), or the gradient per concentration deficiency remains at about 26 per cent suggesting that G approaches a ceiling of about 26 per cent. Also from Pe 1 through 1000, the average mass transfer co-efficient nearly equals that previously calculated for spheres maintaining constant surface concentration instead of flux. The complete differential equation without approximations, the Gauss-Seidel method, and an approximation for the outer boundary condition were used. PMID:14268954

Size limits for rounding of volcanic ash particles heated by lightning.

PubMed

Wadsworth, Fabian B; Vasseur, Jérémie; Llewellin, Edward W; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B

2017-03-01

Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high-temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1-D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters-capillary, Fourier, Stark, Biot, and Peclet numbers-to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension-driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first-order estimate of lightning conditions in volcanic plumes.

Thermal Edge-Effects Model for Automated Tape Placement of Thermoplastic Composites

NASA Technical Reports Server (NTRS)

Costen, Robert C.

2000-01-01

Two-dimensional thermal models for automated tape placement (ATP) of thermoplastic composites neglect the diffusive heat transport that occurs between the newly placed tape and the cool substrate beside it. Such lateral transport can cool the tape edges prematurely and weaken the bond. The three-dimensional, steady state, thermal transport equation is solved by the Green's function method for a tape of finite width being placed on an infinitely wide substrate. The isotherm for the glass transition temperature on the weld interface is used to determine the distance inward from the tape edge that is prematurely cooled, called the cooling incursion Delta a. For the Langley ATP robot, Delta a = 0.4 mm for a unidirectional lay-up of PEEK/carbon fiber composite, and Delta a = 1.2 mm for an isotropic lay-up. A formula for Delta a is developed and applied to a wide range of operating conditions. A surprise finding is that Delta a need not decrease as the Peclet number Pe becomes very large, where Pe is the dimensionless ratio of inertial to diffusive heat transport. Conformable rollers that increase the consolidation length would also increase Delta a, unless other changes are made, such as proportionally increasing the material speed. To compensate for premature edge cooling, the thermal input could be extended past the tape edges by the amount Delta a. This method should help achieve uniform weld strength and crystallinity across the width of the tape.

A critical evaluation of the local-equilibrium assumption in modeling NAPL-pool dissolution

NASA Astrophysics Data System (ADS)

Seagren, Eric A.; Rittmann, Bruce E.; Valocchi, Albert J.

1999-07-01

An analytical modeling analysis was used to assess when local equilibrium (LE) and nonequilibrium (NE) modeling approaches may be appropriate for describing nonaqueous-phase liquid (NAPL) pool dissolution. NE mass-transfer between NAPL pools and groundwater is expected to affect the dissolution flux under conditions corresponding to values of Sh'St (the modified Sherwood number ( Lxkl/ Dz) multiplied by the Stanton number ( kl/ vx))<≈400. A small Sh'St can be brought about by one or more of: a large average pore water velocity ( vx), a large transverse dispersivity ( αz), a small pool length ( Lx), or a small mass-transfer coefficient ( kl). On the other hand, at Sh'St>≈400, the NE and LE solutions converge, and the LE assumption is appropriate. Based on typical groundwater conditions, many cases of interest are expected to fall in this range. The parameter with the greatest impact on Sh'St is kl. The NAPL pool mass-transfer coefficient correlation of Pfannkuch [Pfannkuch, H.-O., 1984. Determination of the contaminant source strength from mass exchange processes at the petroleum-ground-water interface in shallow aquifer systems. In: Proceedings of the NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water—Prevention, Detection, and Restoration, Houston, TX. Natl. Water Well Assoc., Worthington, OH, Nov. 1984, pp. 111-129.] was evaluated using the toluene pool data from Seagren et al. [Seagren, E.A., Rittmann, B.E., Valocchi, A.J., 1998. An experimental investigation of NAPL-pool dissolution enhancement by flushing. J. Contam. Hydrol., accepted.]. Dissolution flux predictions made with kl calculated using the Pfannkuch correlation were similar to the LE model predictions, and deviated systematically from predictions made using the average overall kl=4.76 m/day estimated by Seagren et al. [Seagren, E.A., Rittmann, B.E., Valocchi, A.J., 1998. An experimental investigation of NAPL-pool dissolution enhancement by flushing. J. Contam. Hydrol., accepted.] and from the experimental data for vx>18 m/day. The Pfannkuch correlation kl was too large for vx>≈10 m/day, possibly because of the relatively low Peclet number data used by Pfannkuch [Pfannkuch, H.-O., 1984. Determination of the contaminant source strength from mass exchange processes at the petroleum-ground-water interface in shallow aquifer systems. In: Proceedings of the NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water—Prevention, Detection, and Restoration, Houston, TX. Natl. Water Well Assoc., Worthington, OH, Nov. 1984, pp. 111-129.]. The results of the modeling analyses were evaluated by comparing pool dissolution fluxes from the literature to each other and to the corresponding LE and NE model predictions. The LE model described most of the pool dissolution flux data reasonably well, given the uncertainty in some of the model parameter estimates, suggesting that the LE model can be a useful tool for describing steady-state NAPL pool dissolution under some conditions. However, a conclusive test of the LE assumption was difficult due to the limited range of experimental conditions covered and the uncertainties in some of the model input parameters, including the mass-transfer coefficient correlation required for the NE model.

Does strand configuration and number of purchase points affect the biomechanical behavior of a tendon repair? A biomechanical evaluation using different kessler methods of flexor tendon repair.

PubMed

Dogramaci, Yunus; Kalaci, Aydiner; Sevinç, Teoman Toni; Esen, Erdinc; Komurcu, Mahmut; Yanat, Ahmet Nedim

2008-09-01

This study compares the mechanical properties of modified Kessler and double-modified Kessler flexor tendon repair techniques and evaluates simple modifications on both methods. Forty fresh sheep flexor tendons were divided equally into four groups. A transverse sharp cut was done in the middle of each tendon and then repaired with modified Kessler technique, modified Kessler with additional purchase point in the midpoint of each longitudinal strand, double-modified Kessler technique, or a combination of outer Kessler and inner cruciate configuration based on double-modified Kessler technique. The tendons were tested in a tensile testing machine to assess the mechanical performance of the repairs. Outcome measures included gap formation and ultimate forces. The gap strengths of the double-modified Kessler technique (30.85 N, SD 1.90) and double-modified Kessler technique with inner cruciate configuration (33.60 N, SD 4.64) were statistically significantly greater than that of the two-strand modified Kessler (22.56 N, SD 3.44) and modified Kessler with additional purchase configuration (21.75 N, SD 4.03; Tukey honestly significant difference test, P < 0.000). There were statistically significant differences in failure strengths of the all groups (analysis of variance, P < 0.000). With an identical number of strands, the gap formation and ultimate forces of the repairs were not changed by additional locking purchase point in modified Kessler repair or changing the inner strand configuration in double-modified Kessler repair. The results of this study show that the number of strands across the repair site together with the number of locking loops clearly affects the strength of the repair; meanwhile, the longitudinal strand orientation and number of purchase points in a single loop did not affect its strength.

Genetically Modified Porcine Skin Grafts for Treatment of Severe Burn Injuries

DTIC Science & Technology

2010-07-01

TITLE: Genetically Modified Porcine Skin Grafts for Treatment of Severe Burn Injuries PRINCIPAL INVESTIGATOR: David H. Sachs, M.D...4. TITLE AND SUBTITLE Genetically Modified Porcine Skin Grafts for Treatment of 5a. CONTRACT NUMBER Severe Burn Injuries 5b. GRANT NUMBER...DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES Burns, skin grafts , genetic

Theoretical and numerical studies of chaotic mixing

NASA Astrophysics Data System (ADS)

Kim, Ho Jun

Theoretical and numerical studies of chaotic mixing are performed to circumvent the difficulties of efficient mixing, which come from the lack of turbulence in microfluidic devices. In order to carry out efficient and accurate parametric studies and to identify a fully chaotic state, a spectral element algorithm for solution of the incompressible Navier-Stokes and species transport equations is developed. Using Taylor series expansions in time marching, the new algorithm employs an algebraic factorization scheme on multi-dimensional staggered spectral element grids, and extends classical conforming Galerkin formulations to nonconforming spectral elements. Lagrangian particle tracking methods are utilized to study particle dispersion in the mixing device using spectral element and fourth order Runge-Kutta discretizations in space and time, respectively. Comparative studies of five different techniques commonly employed to identify the chaotic strength and mixing efficiency in microfluidic systems are presented to demonstrate the competitive advantages and shortcomings of each method. These are the stirring index based on the box counting method, Poincare sections, finite time Lyapunov exponents, the probability density function of the stretching field, and mixing index inverse, based on the standard deviation of scalar species distribution. Series of numerical simulations are performed by varying the Peclet number (Pe) at fixed kinematic conditions. The mixing length (lm) is characterized as function of the Pe number, and lm ∝ ln(Pe) scaling is demonstrated for fully chaotic cases. Employing the aforementioned techniques, optimum kinematic conditions and the actuation frequency of the stirrer that result in the highest mixing/stirring efficiency are identified in a zeta potential patterned straight micro channel, where a continuous flow is generated by superposition of a steady pressure driven flow and time periodic electroosmotic flow induced by a stream-wise AC electric field. Finally, it is shown that the invariant manifold of hyperbolic periodic point determines the geometry of fast mixing zones in oscillatory flows in two-dimensional cavity.

Upscaling of reaction rates in reactive transport using pore-scale reactive transport model

NASA Astrophysics Data System (ADS)

Yoon, H.; Dewers, T. A.; Arnold, B. W.; Major, J. R.; Eichhubl, P.; Srinivasan, S.

2013-12-01

Dissolved CO2 during geological CO2 storage may react with minerals in fractured rocks, confined aquifers, or faults, resulting in mineral precipitation and dissolution. The overall rate of reaction can be affected by coupled processes among hydrodynamics, transport, and reactions at the (sub) pore-scale. In this research pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous reaction at the mineral surface is applied to account for permeability alterations caused by precipitation-induced pore-blocking. This work is motivated by the observed CO2 seeps from a natural analog to geologic CO2 sequestration at Crystal Geyser, Utah. A key observation is the lateral migration of CO2 seep sites at a scale of ~ 100 meters over time. A pore-scale model provides fundamental mechanistic explanations of how calcite precipitation alters flow paths by pore plugging under different geochemical compositions and pore configurations. In addition, response function of reaction rates will be constructed from pore-scale simulations which account for a range of reaction regimes characterized by the Damkohler and Peclet numbers. Newly developed response functions will be used in a continuum scale model that may account for large-scale phenomena mimicking lateral migration of surface CO2 seeps. Comparison of field observations and simulations results will provide mechanistic explanations of the lateral migration and enhance our understanding of subsurface processes associated with the CO2 injection. This work is supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

The effect of catchment discretization on rainfall-runoff model predictions

NASA Astrophysics Data System (ADS)

Goodrich, D.; Grayson, R.; Willgoose, G.; Palacios-Valez, O.; Bloschl, G.

2003-04-01

Application of distributed hydrologic watershed models fundamentally requires watershed partitioning or discretization. In addition to partitioning the watershed into modelling elements, these elements typically represent a further abstraction of the actual watershed surface and its relevant hydrologic properties. A critical issue that must be addressed by any user of these models prior to their application is definition of an acceptable level and type of watershed discretization or geometric model complexity. A quantitative methodology to define a level of geometric model complexity commensurate with a specified level of model performance is developed for watershed rainfall-runoff modelling. The methodology is tested on four subcatchments which cover a range of watershed scales of over three orders of magnitude in the USDA-ARS Walnut Gulch Experimental Watershed in Southeastern Arizona. It was found that distortion of the hydraulic roughness can compensate for a lower level of discretization (fewer channels) to a point. Beyond this point, hydraulic roughness distortion cannot compensate for the topographic distortion of representing the watershed by fewer elements (e.g. less complex channel network). Similarly, differences in representation of topography by different model or digital elevation model (DEM) types (e.g. Triangular Irregular Elements - TINs; contour lines; and regular grid DEMs) also result in difference in runoff routing responses that can be largely compensated for by a distortion in hydraulic roughness or path length. To put the effect of these discretization models in context it will be shown that relatively small non-compliance with Peclet number restrictions on timestep size can overwhelm the relatively modest differences resulting from the type of representation of topography.

Catalytic Ignition and Upstream Reaction Propagation in a Platinum Tube

NASA Technical Reports Server (NTRS)

Struk, P. M.; Dietrich, D. L.; Mellish, B. P.; Miller, F. J.; T'ien, J. S.

2007-01-01

A challenge for catalytic combustion in monolithic reactors at elevated temperatures is the start-up or "light-off" from a cold initial condition. In this work, we demonstrate a concept called "back-end catalytic ignition that potentially can be utilized in the light-off of catalytic monoliths. An external downstream flame or Joule heating raises the temperature of a small portion of the catalyst near the outlet initiating a localized catalytic reaction that propagates upstream heating the entire channel. This work uses a transient numerical model to demonstrate "back-end" ignition within a single channel which can characterize the overall performance of a monolith. The paper presents comparisons to an experiment using a single non-adiabatic channel but the concept can be extended to the adiabatic monolith case. In the model, the time scales associated with solid heat-up are typically several orders of magnitude larger than the gas-phase and chemical kinetic time-scales. Therefore, the model assumes a quasi-steady gas-phase with respect to a transient solid. The gas phase is one-dimensional. Appropriate correlations, however, account for heat and mass transfer in a direction perpendicular to the flow. The thermally-thin solid includes axial conduction. The gas phase, however, does not include axial conduction due to the high Peclet number flows. The model includes both detailed gas-phase and catalytic surface reactions. The experiment utilizes a pure platinum circular channel oriented horizontally though which a CO/O2 mixture (equivalence ratios ranging from 0.6 to 0.9) flows at 2 m/s.

Accurate measurement of dispersion data through short and narrow tubes used in very high-pressure liquid chromatography.

PubMed

Gritti, Fabrice; McDonald, Thomas; Gilar, Martin

2015-09-04

An original method is proposed for the accurate and reproducible measurement of the time-based dispersion properties of short L< 50cm and narrow rc< 50μm tubes at mobile phase flow rates typically used in very high-pressure liquid chromatography (vHPLC). Such tubes are used to minimize sample dispersion in vHPLC; however, their dispersion characteristics cannot be accurately measured at such flow rates due to system dispersion contribution of vHPLC injector and detector. It is shown that using longer and wider tubes (>10μL) enables a reliable measurement of the dispersion data. We confirmed that the dimensionless plot of the reduced dispersion coefficient versus the reduced linear velocity (Peclet number) depends on the aspect ratio, L/rc, of the tube, and unexpectedly also on the diffusion coefficient of the analyte. This dimensionless plot could be easily obtained for a large volume tube, which has the same aspect ratio as that of the short and narrow tube, and for the same diffusion coefficient. The dispersion data for the small volume tube are then directly extrapolated from this plot. For instance, it is found that the maximum volume variances of 75μm×30.5cm and 100μm×30.5cm prototype finger-tightened connecting tubes are 0.10 and 0.30μL(2), respectively, with an accuracy of a few percent and a precision smaller than seven percent. Copyright © 2015 Elsevier B.V. All rights reserved.

Environmental Mycobiome Modifiers of Inflammation and Fibrosis in Systemic Sclerosis

DTIC Science & Technology

2015-10-01

COVER&PAGE& ) ) Award)Number:)W81XWH&14&1&0224) ) ) TITLE:)Environmental Mycobiome Modifiers of Inflammation and Fibrosis in Systemic Sclerosis ...Inflammation and Fibrosis in Systemic Sclerosis 5a.&CONTRACT&NUMBER& ) ) ) ) 5b.&GRANT&NUMBER& W81XWH-14-1-0224) ) 5c.&PROGRAM&ELEMENT&NUMBER& ) 6... Sclerosis )(SSc),)a)progressive)fibrotic)disease)characterized)by)skin)fibrosis)and)damage) to) internal) organs.) ) While) a) wide) range) of

Hydrodynamic Scalings: from Astrophysics to Laboratory

NASA Astrophysics Data System (ADS)

Ryutov, D. D.; Remington, B. A.

2000-05-01

A surprisingly general hydrodynamic similarity has been recently described in Refs. [1,2]. One can call it the Euler similarity because it works for the Euler equations (with MHD effects included). Although the dissipation processes are assumed to be negligible, the presence of shocks is allowed. For the polytropic medium (i.e., the medium where the energy density is proportional to the pressure), an evolution of an arbitrarily chosen 3D initial state can be scaled to another system, if a single dimensionless parameter (the Euler number) is the same for both initial states. The Euler similarity allows one to properly design laboratory experiments modeling astrophysical phenomena. We discuss several examples of such experiments related to the physics of supernovae [3]. For the problems with a single spatial scale, the condition of the smallness of dissipative processes can be adequately described in terms of the Reynolds, Peclet, and magnetic Reynolds numbers related to this scale (all three numbers must be large). However, if the system develops small-scale turbulence, dissipation may become important at these smaller scales, thereby affecting the gross behavior of the system. We analyze the corresponding constraints. We discuss also constraints imposed by the presence of interfaces between the substances with different polytropic index. Another set of similarities governs evolution of photoevaporation fronts in astrophysics. Convenient scaling laws exist in situations where the density of the ablated material is very low compared to the bulk density. We conclude that a number of hydrodynamical problems related to such objects as the Eagle Nebula can be adequately simulated in the laboratory. We discuss also possible scalings for radiative astrophysical jets (see Ref. [3] and references therein). This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract W-7405-Eng-48. 1. D.D. Ryutov, R.P. Drake, J. Kane, E. Liang, B. A. Remington, and W.M. Wood-Vasey. "Similarity criteria for the laboratory simulation of supernova hydrodynamics." Astrophysical Journal, v. 518, p. 821 (1999). 2. D.D. Ryutov, R.P. Drake, B.A. Remington. "Criteria for scaled laboratory simulations of astrophysical MHD phenomena." To appear in Astrophysical Journal - Supplement, April 2000. 3. Remington, B.A., Phys. Plasmas, 7, # 5 (2000).

Effects of Fineness Ratio and Reynolds Number on the Low-Speed Crosswind Drag Characteristics of Circular and Modified-Square Cylinders

NASA Technical Reports Server (NTRS)

McKinney, Linwood W.

1960-01-01

A wind-tunnel investigation has been made on modified-square and circular cylinders to determine the effects of fineness ratio and Reynolds numbers on the crosswind drag characteristics. Fineness ratios from 2 to 14 were investigated over a Reynolds number range from approximately 300,000 to 1,650,000 which corresponded to Mach numbers from 0.057 to 0.377.The result of the investigation show that at supercraft Reynolds numbers the drag coefficient of the circular cylinder increases with increasing Reynolds number for all fineness ratios but at low fineness ratios this effect is considerably less than at higher fineness ratios. For circular cylinders in the high fineness-ratio range there is a reduction in drag as the fineness ratio is decreased except for Reynolds numbers of 900,000 and 1,000,000, whereas at low fineness ratios the opposite trend generally occurs. The addition of hemispherical ends to the circular cylinder gave a substantial decrease in drag at a fineness ratio of 3.27 but the effect was negligible at fineness ratios of 5.27 and 10. The finite-length modified-square cylinder gave the reduction in drag over the two-dimensional modified-square cylinder for the complete range of test Reynolds numbers with the lowest fineness ratio giving the lowest drag at Reynolds numbers above 3O0,OOO.

25 CFR 166.308 - Can the number of animals and/or season of use be modified on the permitted land if I graze...

Code of Federal Regulations, 2013 CFR

2013-04-01

... 25 Indians 1 2013-04-01 2013-04-01 false Can the number of animals and/or season of use be... AND WATER GRAZING PERMITS Land and Operations Management § 166.308 Can the number of animals and/or... an on-and-off grazing permit? Yes. The number of animals and/or season of use may be modified on...

25 CFR 166.308 - Can the number of animals and/or season of use be modified on the permitted land if I graze...

Code of Federal Regulations, 2011 CFR

2011-04-01

... 25 Indians 1 2011-04-01 2011-04-01 false Can the number of animals and/or season of use be... AND WATER GRAZING PERMITS Land and Operations Management § 166.308 Can the number of animals and/or... an on-and-off grazing permit? Yes. The number of animals and/or season of use may be modified on...

25 CFR 166.308 - Can the number of animals and/or season of use be modified on the permitted land if I graze...

Code of Federal Regulations, 2010 CFR

2010-04-01

... 25 Indians 1 2010-04-01 2010-04-01 false Can the number of animals and/or season of use be... AND WATER GRAZING PERMITS Land and Operations Management § 166.308 Can the number of animals and/or... an on-and-off grazing permit? Yes. The number of animals and/or season of use may be modified on...

25 CFR 166.308 - Can the number of animals and/or season of use be modified on the permitted land if I graze...

Code of Federal Regulations, 2014 CFR

2014-04-01

... 25 Indians 1 2014-04-01 2014-04-01 false Can the number of animals and/or season of use be... AND WATER GRAZING PERMITS Land and Operations Management § 166.308 Can the number of animals and/or... an on-and-off grazing permit? Yes. The number of animals and/or season of use may be modified on...

Transfer Kinetics at the Aqueous/Non-Aqueous Phase Liquid Interface. A Statistical Mechanic Approach

NASA Astrophysics Data System (ADS)

Doss, S. K.; Ezzedine, S.; Ezzedine, S.; Ziagos, J. P.; Hoffman, F.; Gelinas, R. J.

2001-05-01

Many modeling efforts in the literature use a first-order, linear-driving-force model to represent the chemical dissolution process at the non-aqueous/aqueous phase liquid (NAPL/APL) interface. In other words, NAPL to APL phase flux is assumed to be equal to the difference between the solubility limit and the "bulk aqueous solution" concentrations times a mass transfer coefficient. Under such assumptions, a few questions are raised: where, in relation to a region of pure NAPL, does the "bulk aqueous solution" regime begin and how does it behave? The answers are assumed to be associated with an arbitrary, predetermined boundary layer, which separates the NAPL from the surrounding solution. The mass transfer rate is considered to be, primarily, limited by diffusion of the component through the boundary layer. In fact, compositional models of interphase mass transfer usually assume that a local equilibrium is reached between phases. Representing mass flux as a rate-limiting process is equivalent to assuming diffusion through a stationary boundary layer with an instantaneous local equilibrium and linear concentration profile. Some environmental researchers have enjoyed success explaining their data using chemical engineering-based correlations. Correlations are strongly dependent on the experimental conditions employed. A universally applicable theory for NAPL dissolution in natural systems does not exist. These correlations are usually expressed in terms of the modified Sherwood number as a function of Reynolds, Peclet, and Schmidt numbers. The Sherwood number may be interpreted as the ratio between the grain size and the thickness of the Nernst stagnant film. In the present study, we show that transfer kinetics at the NAPL/APL interface under equilibrium conditions disagree with approaches based on the Nernst stagnant film concept. It is unclear whether local equilibrium assumptions used in current models are suitable for all situations.A statistical mechanic framework has been chosen to study the transfer kinetic processes at the microscale level. The rationale for our approach is based on both the activation energy of transfer of an ion and its velocity across the NAPL/APL interface. There are four major energies controlling the interfacial NAPL dissolution kinetics: (de)solvation energy, interfacial tension energy, electrostatic energy, and thermal fluctuation energy. Transfer of an ion across the NAPL/APL interface is accelerated by the viscous forces which can be described using the averaged Langevin master equation. The resulting energies and viscous forces were combined using the Boltzmann probability distribution. Asymptotic time limits of the resulting kinetics lead to instantaneous local equilibrium conditions that contradict the Nernst equilibrium equation. The NAPL/APL interface is not an ideal one: it does not conserve energy and heat. In our case the interface is treated as a thin film or slush zone that alters the thermodynamic variables. Such added zone, between the two phases, is itself a phase, and, therefore, the equilibrium does not occur between two phases but rather three. All these findings led us to develop a new non-linearly coupled flow and transport system of equations which is able to account for specific chemical dissolution processes and precludes the need for empirical mass-transfer parameters. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Preparation of Composite Fluoropolymers with Enhanced Dewetting Using Fluorinated Silsesquioxanes as Drop-In Modifiers (Preprint)

DTIC Science & Technology

2010-02-17

Dewetting Using Fluorinated Silsesquioxanes as Drop-In Modifiers (Preprint) 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Scott T... Dewetting Using Fluorinated Silsesquioxanes as Drop-In Modifiers (Preprint) Scott T. Iacono, a,b Stephen M. Budy, a,c Dennis W. Smith, a and...nanometer-sized surface roughness due to POSS aggregation. 23 Likewise, similar dewetting behavior, 90 albeit modest, was observed utilizing partially

Identification of Associations Between Genetic Factors and Asthma that are Modified by Obesity

DTIC Science & Technology

2016-06-01

AFRL-SA-WP-TR-2016-0010 Identification of Associations Between Genetic Factors and Asthma That Are Modified by Obesity Andrew T...Between Genetic Factors and Asthma That Are Modified by Obesity 5a. CONTRACT NUMBER FA8650-13-2-6371 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...among African American women in the Women’s Health Initiative study. 15. SUBJECT TERMS Body mass index, SNP, asthma, obesity , genome, genes 16

A Randomized Controlled Trial of the Group-Based Modified Story Memory Technique in TBI

DTIC Science & Technology

2017-10-01

AWARD NUMBER: W81XWH-16-1-0726 TITLE: A Randomized Controlled Trial of the Group -Based Modified Story Memory Technique in TBI PRINCIPAL...2017 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER A Randomized Controlled Trial of the Group -Based Modified Story Memory Technique in TBI 5b. GRANT...forthcoming, The current study addresses this need through a double blind, placebo- controlled , randomized clinical trial (RCT) of a group

Arithmetic operations in optical computations using a modified trinary number system.

PubMed

Datta, A K; Basuray, A; Mukhopadhyay, S

1989-05-01

A modified trinary number (MTN) system is proposed in which any binary number can be expressed with the help of trinary digits (1, 0, 1 ). Arithmetic operations can be performed in parallel without the need for carry and borrow steps when binary digits are converted to the MTN system. An optical implementation of the proposed scheme that uses spatial light modulators and color-coded light signals is described.

Entree Production Guides for Modified Diets at Walter Reed Army Medical Center. Part 4. Meat Substitute Entrees

DTIC Science & Technology

1979-06-01

numbers of vegetarian patients. Part V, Renal Diets , consists of eight very carefully weighed entrees and one dessert. These items are designed to give...WORDS (Conthmae an, revee side It nocesary and Identify by black number) \\ ~FOOD PREPARATION MEAT SUBSTITUTE MODIFIED DIETS COOK-FEEZE SYSTEMS SENSORY...Unsrfnounced I:! I *1C: -r Lii ENTREE PRODUCTION GUIDES FOR MODIFIED DIETS AT WALTER REED ARMY MEDICAL CENTER PART III: DENTAL LIQUID ENTREES FOREWORD

Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion

NASA Astrophysics Data System (ADS)

Liu, Longcheng; Neretnieks, Ivars; Shahkarami, Pirouz; Meng, Shuo; Moreno, Luis

2018-02-01

A simple and robust solution is developed for the problem of solute transport along a single fracture in a porous rock. The solution is referred to as the solution to the single-flow-path model and takes the form of a convolution of two functions. The first function is the probability density function of residence-time distribution of a conservative solute in the fracture-only system as if the rock matrix is impermeable. The second function is the response of the fracture-matrix system to the input source when Fickian-type dispersion is completely neglected; thus, the effects of Fickian-type dispersion and matrix diffusion have been decoupled. It is also found that the solution can be understood in a way in line with the concept of velocity dispersion in fractured rocks. The solution is therefore extended into more general cases to also account for velocity variation between the channels. This leads to a development of the multi-channel model followed by detailed statistical descriptions of channel properties and sensitivity analysis of the model upon changes in the model key parameters. The simulation results obtained by the multi-channel model in this study fairly well agree with what is often observed in field experiments—i.e. the unchanged Peclet number with distance, which cannot be predicted by the classical advection-dispersion equation. In light of the findings from the aforementioned analysis, it is suggested that forced-gradient experiments can result in considerably different estimates of dispersivity compared to what can be found in natural-gradient systems for typical channel widths.

Effect of pore water velocities and solute input methods on chloride transport in the undisturbed soil columns of Loess Plateau

NASA Astrophysics Data System (ADS)

Zhou, BeiBei; Wang, QuanJiu

2017-09-01

Studies on solute transport under different pore water velocity and solute input methods in undisturbed soil could play instructive roles for crop production. Based on the experiments in the laboratory, the effect of solute input methods with small pulse input and large pulse input, as well as four pore water velocities, on chloride transport in the undisturbed soil columns obtained from the Loess Plateau under controlled condition was studied. Chloride breakthrough curves (BTCs) were generated using the miscible displacement method under water-saturated, steady flow conditions. Using the 0.15 mol L-1 CaCl2 solution as a tracer, a small pulse (0.1 pore volumes) was first induced, and then, after all the solution was wash off, a large pulse (0.5 pore volumes) was conducted. The convection-dispersion equation (CDE) and the two-region model (T-R) were used to describe the BTCs, and their prediction accuracies and fitted parameters were compared as well. All the BTCs obtained for the different input methods and the four pore water velocities were all smooth. However, the shapes of the BTCs varied greatly; small pulse inputs resulted in more rapid attainment of peak values that appeared earlier with increases in pore water velocity, whereas large pulse inputs resulted in an opposite trend. Both models could fit the experimental data well, but the prediction accuracy of the T-R was better. The values of the dispersivity, λ, calculated from the dispersion coefficient obtained from the CDE were about one order of magnitude larger than those calculated from the dispersion coefficient given by the T-R, but the calculated Peclet number, Pe, was lower. The mobile-immobile partition coefficient, β, decreased, while the mass exchange coefficient increased with increases in pore water velocity.

Turbulent mixing& combustion in TNT explosions

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

Kuhl, A L; Ferguson, R E; Oppenheim, A K

2000-12-12

Effects of turbulent mixing induced by explosion of a 1-g spherical TNT charge in air are investigated. The detonation wave in the charge transforms the solid explosive (C{sub 7}H{sub 5}N{sub 3}O{sub 6}) to gaseous products, rich in C{sub (S)}, and CO. The detonation pressure ({approx}210 kb) causes the products to expand rapidly, driving a blast wave into the surrounding air (Brode, 1959). The interface between the products and air is unstable (Richtmyer, 1960; Meshkov, 1960; Anisimov & Zel'dovich, 1977). As shown in Collage Ia-c, this region rapidly transitions into a turbulent mixing layer (Kuhl, 1996). As the embedded shock, I,more » implodes, it draws the mixing structures (Taylor cavities) into the origin (Collage Id-e). In this way air becomes distributed throughout the hot detonation products gases. This process is enhanced by shock reflections from confining walls. In either case (confined or unconfined), rapid combustion takes place where the expanded detonation products play the role of fuel. This leads to a dramatic increase in chamber pressure (Fig. 1)-in contrast to a corresponding TNT explosion in nitrogen. The problem was modeled as turbulent combustion in an unmixed system at large Reynolds, Peclet and Damkohler numbers (Kuhl et al, 1997). The numerical solution was obtained by a high-order Godunov scheme (Colella & Glaz, 1985). Adaptive Mesh Refinement (Berger & Colella, 1989) was used to follow the turbulent mixing on the computational grid in as much detail as possible. The results reveal all the dynamic features (Fig. 2) of the exothermic process of combustion controlled by fluid-mechanic transport in a highly turbulent field (Kuhl & Oppenheim, 1997), in contrast to the conventional reaction-diffusion mechanism of Zel'dovich & Frank-Kamenetskii (1938).« less

Confined combustion of TNT explosion products in air

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

Chandler, J; Ferguson, R E; Forbes, J

1998-08-31

Effects of turbulent combustion induced by explosion of a 0.8 kg cylindrical charge of TNT in a 17 m 3 chamber filled with air, are investigated. The detonation wave in the charge transforms the solid explosive (C 7H 5N 3O 6) to gaseous products, rich (~20% each) in carbon dust and carbon monoxide. The detonation pressure (~210 kb) thereby engendered causes the products to expand rapidly, driving a blast wave into the surrounding air. The interface between the products and air, being essentially unstable as a consequence of strong acceleration to which it is subjected within the blast wave, evolvesmore » into a turbulent mixing layer-a process enhanced by shock reflections from the walls. Under such circumstances rapid combustion takes place where the expanded detonation products play the role of fuel. Its dynamic effect is manifested by the experimental measurement of ~3 bar pressure increase in the chamber, in contrast to ~1bar attained by a corresponding TNT explosion in nitrogen. The experiments were modeled as a turbulent combustion in an unmixed system at infinite Reynolds, Peclet and DamkGhler numbers. The CFD solution was obtained by a high-order Godunov scheme using an AMR (Adaptive Mesh Refinement) to trace the turbulent mixing on the computational grid in as much detail as possible. The evolution of the mass fraction of fuel consumed by combustion thus determined exhibited the properties of an exponential decay following a sharp initiation. The results reveal all the dynamic features of the exothermic process of combustion controlled by fluid mechanic transport in a highly turbulent field, in contrast to those elucidated by the conventional reaction-diffusion model.« less

Finite-part integration of the generalized Stieltjes transform and its dominant asymptotic behavior for small values of the parameter. I. Integer orders

NASA Astrophysics Data System (ADS)

Tica, Christian D.; Galapon, Eric A.

2018-02-01

The paper addresses the exact evaluation of the generalized Stieltjes transform Sn[f ] =∫0∞f (x ) (ω+x ) -nd x of integral order n = 1, 2, 3, … about ω = 0 from which the asymptotic behavior of Sn[f] for small parameters ω is directly extracted. An attempt to evaluate the integral by expanding the integrand (ω + x)-n about ω = 0 and then naively integrating the resulting infinite series term by term leads to an infinite series whose terms are divergent integrals. Assigning values to the divergent integrals, say, by analytic continuation or by Hadamard's finite part is known to reproduce only some of the correct terms of the expansion but completely misses out a group of terms. Here we evaluate explicitly the generalized Stieltjes transform by means of finite-part integration recently introduced in Galapon [Proc. R. Soc. A 473, 20160567 (2017)]. It is shown that, when f(x) does not vanish or has zero of order m at the origin such that (n - m) ≥ 1, the dominant terms of Sn[f] as ω → 0 come from contributions arising from the poles and branch points of the complex valued function f(z)(ω + z)-n. These dominant terms are precisely the terms missed out by naive term by term integration. Furthermore, it is demonstrated how finite-part integration leads to new series representations of special functions by exploiting their known Stieltjes integral representations. Finally, the application of finite part integration in obtaining asymptotic expansions of the effective diffusivity in the limit of high Peclet number, the Green-Kubo formula for the self-diffusion coefficient, and the antisymmetric part of the diffusion tensor in the weak noise limit is discussed.

Simple Kinematic Pathway Approach (KPA) to Catchment-scale Travel Time and Water Age Distributions

NASA Astrophysics Data System (ADS)

Soltani, S. S.; Cvetkovic, V.; Destouni, G.

2017-12-01

The distribution of catchment-scale water travel times is strongly influenced by morphological dispersion and is partitioned between hillslope and larger, regional scales. We explore whether hillslope travel times are predictable using a simple semi-analytical "kinematic pathway approach" (KPA) that accounts for dispersion on two levels of morphological and macro-dispersion. The study gives new insights to shallow (hillslope) and deep (regional) groundwater travel times by comparing numerical simulations of travel time distributions, referred to as "dynamic model", with corresponding KPA computations for three different real catchment case studies in Sweden. KPA uses basic structural and hydrological data to compute transient water travel time (forward mode) and age (backward mode) distributions at the catchment outlet. Longitudinal and morphological dispersion components are reflected in KPA computations by assuming an effective Peclet number and topographically driven pathway length distributions, respectively. Numerical simulations of advective travel times are obtained by means of particle tracking using the fully-integrated flow model MIKE SHE. The comparison of computed cumulative distribution functions of travel times shows significant influence of morphological dispersion and groundwater recharge rate on the compatibility of the "kinematic pathway" and "dynamic" models. Zones of high recharge rate in "dynamic" models are associated with topographically driven groundwater flow paths to adjacent discharge zones, e.g. rivers and lakes, through relatively shallow pathway compartments. These zones exhibit more compatible behavior between "dynamic" and "kinematic pathway" models than the zones of low recharge rate. Interestingly, the travel time distributions of hillslope compartments remain almost unchanged with increasing recharge rates in the "dynamic" models. This robust "dynamic" model behavior suggests that flow path lengths and travel times in shallow hillslope compartments are controlled by topography, and therefore application and further development of the simple "kinematic pathway" approach is promising for their modeling.

Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone

USGS Publications Warehouse

Bachand, P.A.M.; S. Bachand,; Fleck, Jacob A.; Anderson, Frank E.; Windham-Myers, Lisamarie

2014-01-01

The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flowrates and tracer concentrations atwetland inflows and outflows. We used two ideal reactormodel solutions, a continuous flowstirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these nonideal agricultural wetlands in which check ponds are in series. Using a fluxmodel, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment–water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemicalmechanisms affecting dissolved constituent cycling in the root zone. In addition,our understanding of internal root zone cycling of Hg and other dissolved constituents, benthic fluxes, and biological irrigation may be greatly affected.

A Green's function method for two-dimensional reactive solute transport in a parallel fracture-matrix system

NASA Astrophysics Data System (ADS)

Chen, Kewei; Zhan, Hongbin

2018-06-01

The reactive solute transport in a single fracture bounded by upper and lower matrixes is a classical problem that captures the dominant factors affecting transport behavior beyond pore scale. A parallel fracture-matrix system which considers the interaction among multiple paralleled fractures is an extension to a single fracture-matrix system. The existing analytical or semi-analytical solution for solute transport in a parallel fracture-matrix simplifies the problem to various degrees, such as neglecting the transverse dispersion in the fracture and/or the longitudinal diffusion in the matrix. The difficulty of solving the full two-dimensional (2-D) problem lies in the calculation of the mass exchange between the fracture and matrix. In this study, we propose an innovative Green's function approach to address the 2-D reactive solute transport in a parallel fracture-matrix system. The flux at the interface is calculated numerically. It is found that the transverse dispersion in the fracture can be safely neglected due to the small scale of fracture aperture. However, neglecting the longitudinal matrix diffusion would overestimate the concentration profile near the solute entrance face and underestimate the concentration profile at the far side. The error caused by neglecting the longitudinal matrix diffusion decreases with increasing Peclet number. The longitudinal matrix diffusion does not have obvious influence on the concentration profile in long-term. The developed model is applied to a non-aqueous-phase-liquid (DNAPL) contamination field case in New Haven Arkose of Connecticut in USA to estimate the Trichloroethylene (TCE) behavior over 40 years. The ratio of TCE mass stored in the matrix and the injected TCE mass increases above 90% in less than 10 years.

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

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

Qu, Ge; Zhao, Xikang; Newbloom, Gregory M.

Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor–acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiopheneco- thieno[3,2- b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π–π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coatingmore » direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. As a result, we further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.« less

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

DOE PAGES

Qu, Ge; Zhao, Xikang; Newbloom, Gregory M.; ...

2017-08-01

Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor–acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiopheneco- thieno[3,2- b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π–π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coatingmore » direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. As a result, we further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.« less

Mixing driven by transient buoyancy flows. I. Kinematics

NASA Astrophysics Data System (ADS)

Duval, W. M. B.; Zhong, H.; Batur, C.

2018-05-01

Mixing of two miscible liquids juxtaposed inside a cavity initially separated by a divider, whose buoyancy-driven motion is initiated via impulsive perturbation of divider motion that can generate the Richtmyer-Meshkov instability, is investigated experimentally. The measured Lagrangian history of interface motion that contains the continuum mechanics of mixing shows self-similar nearly Gaussian length stretch distribution for a wide range of control parameters encompassing an approximate Hele-Shaw cell to a three-dimensional cavity. Because of the initial configuration of the interface which is parallel to the gravitational field, we show that at critical initial potential energy mixing occurs through the stretching of the interface, which shows frontogenesis, and folding, owing to an overturning motion that results in unstable density stratification and produces an ideal condition for the growth of the single wavelength Rayleigh-Taylor instability. The initial perturbation of the interface and flow field generates the Kelvin-Helmholtz instability and causes kinks at the interface, which grow into deep fingers during overturning motion and unfold into local whorl structures that merge and self-organize into the Rayleigh-Taylor morphology (RTM) structure. For a range of parametric space that yields two-dimensional flows, the unfolding of the instability through a supercritical bifurcation yields an asymmetric pairwise structure exhibiting smooth RTM that transitions to RTM fronts with fractal structures that contain small length scales for increasing Peclet numbers. The late stage of the RTM structure unfolds into an internal breakwave that breaks down through wall and internal collision and sets up the condition for self-induced sloshing that decays exponentially as the two fluids become stably stratified with a diffusive region indicating local molecular diffusion.

Dispersion upscaling from a pore scale characterization of Lagrangian velocities

NASA Astrophysics Data System (ADS)

Turuban, Régis; de Anna, Pietro; Jiménez-Martínez, Joaquín; Tabuteau, Hervé; Méheust, Yves; Le Borgne, Tanguy

2013-04-01

Mixing and reactive transport are primarily controlled by the interplay between diffusion, advection and reaction at pore scale. Yet, how the distribution and spatial correlation of the velocity field at pore scale impact these processes is still an open question. Here we present an experimental investigation of the distribution and correlation of pore scale velocities and its relation with upscaled dispersion. We use a quasi two-dimensional (2D) horizontal set up, consisting of two glass plates filled with cylinders representing the grains of the porous medium : the cell is built by soft lithography technique, wich allows for full control of the system geometry. The local velocity field is quantified from particle tracking velocimetry using microspheres that are advected with the pore scale flow. Their displacement is purely advective, as the particle size is chosen large enough to avoid diffusion. We thus obtain particle trajectories as well as lagrangian velocities in the entire system. The measured velocity field shows the existence of a network of preferential flow paths in channels with high velocities, as well as very low velocity in stagnation zones, with a non Gaussian distribution. Lagrangian velocities are long range correlated in time, which implies a non-fickian scaling of the longitudinal variance of particle positions. To upscale this process we develop an effective transport model, based on correlated continous time random walk, which is entirely parametrized by the pore scale velocity distribution and correlation. The model predictions are compared with conservative tracer test data for different Peclet numbers. Furthermore, we investigate the impact of different pore geometries on the distribution and correlation of Lagrangian velocities and we discuss the link between these properties and the effective dispersion behavior.

Effects of aspect ratio and concentration on rheology of epoxy suspensions containing model plate-like nanoparticles

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

White, K. L.; Takahara, A.; Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395

2015-12-15

Hexagonal 2-dimensional α-zirconium phosphate crystals were prepared with lateral diameters ranging from 110 nm to 1.5 μm to investigate the effect of particle size on suspension rheology. The nanoplatelets were exfoliated to individual sheets with monodisperse thickness and dispersed in a Newtonian epoxy fluid. The steady shear response of dilute and semi-dilute suspensions was measured and compared to expressions obtained from theory for infinitely dilute suspensions. For suspensions containing the smaller nanoplatelets, aspect ratio ∼160, the low shear rate viscosity and transition to shear thinning behavior were well described by theory for loadings up to 0.5 vol. %. The agreementmore » was improved by assuming a moderate polydispersity in lateral diameter, ∼30%–50%, which is consistent with experimental observation. For the higher aspect ratio nanoplatelets, good agreement between theory and experiment was observed only at high shear rates. At lower shear rate, theory consistently over-predicted viscosity, which was attributed to a progressive shift to non-isotropic initial conditions with increasing particle size. The results suggest that at a fixed Peclet number, there is an increasing tendency for the nanoplatelets to form transient, local stacks as particle size increases. The largest particles, aspect ratio ∼2200, showed unusual shear thinning and thickening behaviors that were attributed to particle flexibility. The findings demonstrate the surprising utility of theory for infinitely dilute suspensions to interpret, and in some cases quantitatively describe, the non-Newtonian viscosity of real suspensions containing high aspect ratio plate-like particles. A simple framework is proposed to interpret deviations from ideal behavior based on the local and collective behavior of the suspended nanoplatelets.« less

Study of ocular transport of drugs released from an intravitreal implant using magnetic resonance imaging.

PubMed

Kim, Hyuncheol; Lizak, Martin J; Tansey, Ginger; Csaky, Karl G; Robinson, Michael R; Yuan, Peng; Wang, Nam Sun; Lutz, Robert J

2005-02-01

Ensuring optimum delivery of therapeutic agents in the eye requires detailed information about the transport mechanisms and elimination pathways available. This knowledge can guide the development of new drug delivery devices. In this study, we investigated the movement of a drug surrogate, Gd-DTPA (Magnevist) released from a polymer-based implant in rabbit vitreous using T1-weighted magnetic resonance imaging (MRI). Intensity values in the MRI data were converted to concentration by comparison with calibration samples. Concentration profiles approaching pseudosteady state showed gradients from the implant toward the retinal surface, suggesting that diffusion was occurring into the retinal-choroidal-scleral (RCS) membrane. Gd-DTPA concentration varied from high values near the implant to lower values distal to the implant. Such regional concentration differences throughout the vitreous may have clinical significance when attempting to treat ubiquitous eye diseases using a single positional implant. We developed a finite element mathematical model of the rabbit eye and compared the MRI experimental concentration data with simulation concentration profiles. The model utilized a diffusion coefficient of Gd-DTPA in the vitreous of 2.8 x 10(-6) cm2 s(-1) and yielded a diffusion coefficient for Gd-DTPA through the simulated composite posterior membrane (representing the retina-choroidsclera membrane) of 6.0 x 10(-8) cm2 s(-1). Since the model membrane was 0.03-cm thick, this resulted in an effective membrane permeability of 2.0 x 10(-6) cm s(-1). Convective movement of Gd-DTPA was shown to have minimal effect on the concentration profiles since the Peclet number was 0.09 for this system.

Tape-Drop Transient Model for In-Situ Automated Tape Placement of Thermoplastic Composites

NASA Technical Reports Server (NTRS)

Costen, Robert C.; Marchello, Joseph M.

1998-01-01

Composite parts of nonuniform thickness can be fabricated by in-situ automated tape placement (ATP) if the tape can be started and stopped at interior points of the part instead of always at its edges. This technique is termed start/stop-on-the-part, or, alternatively, tape-add/tape-drop. The resulting thermal transients need to be managed in order to achieve net shape and maintain uniform interlaminar weld strength and crystallinity. Starting-on-the-part has been treated previously. This paper continues the study with a thermal analysis of stopping-on-the-part. The thermal source is switched off when the trailing end of the tape enters the nip region of the laydown/consolidation head. The thermal transient is determined by a Fourier-Laplace transform solution of the two-dimensional, time-dependent thermal transport equation. This solution requires that the Peclet number Pe (the dimensionless ratio of inertial to diffusive heat transport) be independent of time and much greater than 1. Plotted isotherms show that the trailing tape-end cools more rapidly than the downstream portions of tape. This cooling can weaken the bond near the tape end; however the length of the affected region is found to be less than 2 mm. To achieve net shape, the consolidation head must continue to move after cut-off until the temperature on the weld interface decreases to the glass transition temperature. The time and elapsed distance for this condition to occur are computed for the Langley ATP robot applying PEEK/carbon fiber composite tape and for two upgrades in robot performance. The elapsed distance after cut-off ranges from about 1 mm for the present robot to about 1 cm for the second upgrade.

Reversible entrapment of plasmid deoxyribonucleic acid on different chromatographic supports.

PubMed

Gabor, Boštjan; Černigoj, Urh; Barut, Miloš; Štrancar, Aleš

2013-10-11

HPLC based analytical assay is a powerful technique that can be used to efficiently monitor plasmid DNA (pDNA) purity and quantity throughout the entire purification process. Anion exchange monolithic and non-porous particle based stationary phases were used to study the recovery of the different pDNA isoforms from the analytical column. Three differently sized pDNA molecules of 3.0kbp, 5.2kbp and 14.0kbp were used. Plasmid DNA was injected onto columns under the binding conditions and the separation of the isoforms took place by increasing the ionic strength of the elution buffer. While there was no substantial decrease of the recovered supercoiled and linear isoforms of the pDNA with the increase of the plasmid size and with the increase of the flow rate (recoveries in all cases larger than 75%), a pronounced decrease of the oc isoform recovery was observed. The entrapment of the oc pDNA isoform occurred under non-binding conditions as well. The partial oc isoform elution from the column could be achieved by decreasing the flow rate of the elution mobile phase. The results suggested a reversible entrapment of the oc isoform in the restrictions within the pores of the monolithic material as well as within the intra-particle space of the non-porous particles. This phenomenon was observed on both types of the stationary phase morphologies and could only be connected to the size of a void space through which the pDNA needs to migrate. A prediction of reversible pDNA entrapment was successfully estimated with the calculation of Peclet numbers, Pe, which defines the ratio between a convective and diffusive mass transport. Copyright © 2013 Elsevier B.V. All rights reserved.

Modified 30-second Sit to Stand test predicts falls in a cohort of institutionalized older veterans

PubMed Central

Chassé, Kathleen

2017-01-01

Physical function performance tests, including sit to stand tests and Timed Up and Go, assess the functional capacity of older adults. Their ability to predict falls warrants further investigation. The objective was to determine if a modified 30-second Sit to Stand test that allowed upper extremity use and Timed Up and Go test predicted falls in institutionalized Veterans. Fifty-three older adult Veterans (mean age = 91 years, 49 men) residing in a long-term care hospital completed modified 30-second Sit to Stand and Timed Up and Go tests. The number of falls over one year was collected. The ability of modified 30-second Sit to Stand or Timed Up and Go to predict if participants had fallen was examined using logistic regression. The ability of these tests to predict the number of falls was examined using negative binomial regression. Both analyses controlled for age, history of falls, cognition, and comorbidities. The modified 30-second Sit to Stand was significantly (p < 0.05) related to if participants fell (odds ratio = 0.75, 95% confidence interval = 0.58, 0.97) and the number of falls (incidence rate ratio = 0.82, 95% confidence interval = 0.68, 0.98); decreased repetitions were associated with increased number of falls. Timed Up and Go was not significantly (p > 0.05) related to if participants fell (odds ratio = 1.03, 95% confidence interval = 0.96, 1.10) or the number of falls (incidence rate ratio = 1.01, 95% confidence interval = 0.98, 1.05). The modified 30-second Sit to Stand that allowed upper extremity use offers an alternative method to screen for fall risk in older adults in long-term care. PMID:28464024

Subsonic and Supersonic Flutter Analysis of a Highly Tapered Swept-Wing Planform, Including Effects of Density Variation and Finite Wing Thickness, and Comparison with Experiments

NASA Technical Reports Server (NTRS)

Yates, Carson, Jr.

1967-01-01

The flutter characteristics of several wings with an aspect-ratio of 4.0, a taper ratio of 0.2, and a quarter-chord sweepback of 45 deg. have been investigated analytically for Mach numbers up to 2.0. The calculations were based on the modified-strip-analysis method, the subsonic-kernel-function method, piston theory, and quasi-steady second-order theory. Results of t h e analysis and comparisons with experiment indicated that: (1) Flutter speeds were accurately predicted by the modified strip analysis, although accuracy at t h e highest Mach numbers required the use of nonlinear aerodynamic theory (which accounts for effects of wing thickness) for the calculation of the aerodynamic parameters. (2) An abrupt increase of flutter-speed coefficient with increasing Mach number, observed experimentally in the transonic range, was also indicated by the modified strip analysis. (3) In the low supersonic range for some densities, a discontinuous variation of flutter frequency with Mach number was indicated by the modified strip analysis. An abrupt change of frequency appeared experimentally in the transonic range. (4) Differences in flutter-speed-coefficient levels obtained from tests at low supersonic Mach numbers in two wind tunnels were also predicted by the modified strip analysis and were shown to be caused primarily by differences in mass ratio. (5) Flutter speeds calculated by the subsonic-kernel-function method were in good agreement with experiment and with the results of the modified strip analysis. (6) Flutter speed obtained from piston theory and from quasi-steady second-order theory were higher than experimental values by at least 38 percent.

Modified 30-second Sit to Stand test predicts falls in a cohort of institutionalized older veterans.

PubMed

Applebaum, Eva V; Breton, Dominic; Feng, Zhuo Wei; Ta, An-Tchi; Walsh, Kayley; Chassé, Kathleen; Robbins, Shawn M

2017-01-01

Physical function performance tests, including sit to stand tests and Timed Up and Go, assess the functional capacity of older adults. Their ability to predict falls warrants further investigation. The objective was to determine if a modified 30-second Sit to Stand test that allowed upper extremity use and Timed Up and Go test predicted falls in institutionalized Veterans. Fifty-three older adult Veterans (mean age = 91 years, 49 men) residing in a long-term care hospital completed modified 30-second Sit to Stand and Timed Up and Go tests. The number of falls over one year was collected. The ability of modified 30-second Sit to Stand or Timed Up and Go to predict if participants had fallen was examined using logistic regression. The ability of these tests to predict the number of falls was examined using negative binomial regression. Both analyses controlled for age, history of falls, cognition, and comorbidities. The modified 30-second Sit to Stand was significantly (p < 0.05) related to if participants fell (odds ratio = 0.75, 95% confidence interval = 0.58, 0.97) and the number of falls (incidence rate ratio = 0.82, 95% confidence interval = 0.68, 0.98); decreased repetitions were associated with increased number of falls. Timed Up and Go was not significantly (p > 0.05) related to if participants fell (odds ratio = 1.03, 95% confidence interval = 0.96, 1.10) or the number of falls (incidence rate ratio = 1.01, 95% confidence interval = 0.98, 1.05). The modified 30-second Sit to Stand that allowed upper extremity use offers an alternative method to screen for fall risk in older adults in long-term care.

Enhanced heat transfer and frictional losses in heat exchanger tube with modified helical coiled inserts

NASA Astrophysics Data System (ADS)

Verma, Aditya; Kumar, Manoj; Patil, Anil Kumar

2018-04-01

The application of compact heat exchangers in any thermal system improves overall performance with a considerable reduction in size and weight. Inserts of different geometrical features have been used as turbulence promoting devices to increase the heat transfer rates. The present study deals with the experimental investigation of heat transfer and fluid flow characteristics of a tubular heat exchanger fitted with modified helical coiled inserts. Experiments have been carried out for a smooth tube without insert, tube fitted with helical coiled inserts, and modified helical coiled inserts. The helical coiled inserts are tested by varying the pitch ratio and wire diameter ratio from 0.5-1.5, and 0.063-0.125, respectively for the Reynolds number range of 1400 to 11,000. Experimental data have also been collected for the modified helical coiled inserts with gradually increasing pitch (GIP) and gradually decreasing pitch (GDP) configurations. The Nusselt number and friction factor values for helical coiled inserts are enhanced in the range of 1.42-2.62, 3.4-27.4, relative to smooth tube, respectively. The modified helical coiled insert showed enhancements in Nusselt number and friction factor values in the range of 1.49-3.14, 11.2-19.9, relative to smooth tube, respectively. The helical coiled and modified helical coiled inserts have thermo-hydraulic performance factor in the range of 0.59-1.29, 0.6-1.39, respectively. The empirical correlations of Nusselt number and friction factor for helical coiled inserts are proposed.

Recent Advances and Future Challenges in Modified Mycotoxin Analysis: Why HRMS Has Become a Key Instrument in Food Contaminant Research

PubMed Central

Righetti, Laura; Paglia, Giuseppe; Galaverna, Gianni; Dall’Asta, Chiara

2016-01-01

Mycotoxins are secondary metabolites produced by pathogenic fungi in crops worldwide. These compounds can undergo modification in plants, leading to the formation of a large number of possible modified forms, whose toxicological relevance and occurrence in food and feed is still largely unexplored. The analysis of modified mycotoxins by liquid chromatography–mass spectrometry remains a challenge because of their chemical diversity, the large number of isomeric forms, and the lack of analytical standards. Here, the potential benefits of high-resolution and ion mobility mass spectrometry as a tool for separation and structure confirmation of modified mycotoxins have been investigated/reviewed. PMID:27918432

A multi-threaded version of MCFM

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

Campbell, John M.; Ellis, R. Keith; Giele, Walter T.

We report on our findings modifying MCFM using OpenMP to implement multi-threading. By using OpenMP, the modified MCFM will execute on any processor, automatically adjusting to the number of available threads. We then modified the integration routine VEGAS to distribute the event evaluation over the threads, while combining all events at the end of every iteration to optimize the numerical integration. Furthermore, we took special care so that the results of the Monte Carlo integration were independent of the number of threads used, to facilitate the validation of the OpenMP version of MCFM.

Wear behavior of AISI 1090 steel modified by pulse plasma technique

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

Ayday, Aysun; Durman, Mehmet

2012-09-06

AISI 1090 steel was pulse plasma treated (PPT) using a Molybdenum electrode. Two different pulse numbers were chosen to obtain modified layers of 20{+-}5 {mu}m thickness. The dry sliding wear studies performed on this steel with and without PPT against an alumina ball counterpart showed that the PPT improved the wear resistance. The pulse number of the PPT modified layer was found to be highly influential in imparting the wear resistance to this steel, due to enhancement of surface hardness depending on treatment time.

Space-Based Three-Dimensional Imaging of Equatorial Plasma Bubbles: Advancing the Understanding of Ionospheric Density Depletions and Scintillation

DTIC Science & Technology

2012-03-28

Scintillation 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Comberiate, Joseph M. 5e. TASK NUMBER 5f. WORK...bubble climatology. A tomographic reconstruction technique was modified and applied to SSUSI data to reconstruct three-dimensional cubes of ionospheric... modified and applied to SSUSI data to reconstruct three-dimensional cubes of ionospheric electron density. These data cubes allowed for 3-D imaging of

A directional entrapment modification on the polyethylene surface by the amphiphilic modifier of stearyl-alcohol poly(ethylene oxide) ether

NASA Astrophysics Data System (ADS)

Lu, Qiang; Chen, Yi; Huang, Juexin; Huang, Jian; Wang, Xiaolin; Yao, Jiaying

2018-05-01

A novel entrapment modification method involving directional implantation of the amphiphilic modifier of stearyl-alcohol poly(ethylene oxide) ether (AEO) into the high-density polyethylene (HDPE) surface is proposed. This modification technique allows the AEO modifier to be able to spontaneously attain and subsequently penetrate into the swollen HDPE surface with its hydrophobic stearyl segment, while its hydrophilic poly(ethylene oxide) (PEO) segment spontaneously points to water. The AEO modifier with a HLB number below 8.7 was proved appropriate for the directional entrapment, Nevertheless, AEOs with larger HLB numbers were also effective modifiers in the presence of salt additives. In addition, a larger and hydrophobic micelle, induced respectively by the AEO concentration above 1.3 × 10-2 mol/L and the entrapping temperature above the cloud point of AEO, could lead to a sharp contact angle decline of the modified surface. Finally, a hydrophilic HDPE surface with the modifier coverage of 38.9% was reached by the directional entrapment method, which is far larger than that of 19.2% by the traditional entrapment method.

Modified screening and ranking algorithm for copy number variation detection.

PubMed

Xiao, Feifei; Min, Xiaoyi; Zhang, Heping

2015-05-01

Copy number variation (CNV) is a type of structural variation, usually defined as genomic segments that are 1 kb or larger, which present variable copy numbers when compared with a reference genome. The screening and ranking algorithm (SaRa) was recently proposed as an efficient approach for multiple change-points detection, which can be applied to CNV detection. However, some practical issues arise from application of SaRa to single nucleotide polymorphism data. In this study, we propose a modified SaRa on CNV detection to address these issues. First, we use the quantile normalization on the original intensities to guarantee that the normal mean model-based SaRa is a robust method. Second, a novel normal mixture model coupled with a modified Bayesian information criterion is proposed for candidate change-point selection and further clustering the potential CNV segments to copy number states. Simulations revealed that the modified SaRa became a robust method for identifying change-points and achieved better performance than the circular binary segmentation (CBS) method. By applying the modified SaRa to real data from the HapMap project, we illustrated its performance on detecting CNV segments. In conclusion, our modified SaRa method improves SaRa theoretically and numerically, for identifying CNVs with high-throughput genotyping data. The modSaRa package is implemented in R program and freely available at http://c2s2.yale.edu/software/modSaRa. Supplementary data are available at Bioinformatics online. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Dynamic analysis of modified transcutaneous lower blepharoplasty based on biochemical and biophysical principles.

PubMed

Liao, Chuh-Kai; Tsai, Feng-Chou; Fong, Tsorng-Harn; Huang, Chin-Ju; Shen, Yi-Chin; Ku, Yuan-Hao; Su, Ching-Hua

2013-12-01

In this study, we analyzed the key parameters of modified transcutaneous lower blepharoplasty based on multidisciplinary principles (biochemical findings and biophysical wrinkling theory). A total of 408 female patients received our subciliary lower blepharoplasty between March 2002 and January 2010. The severity of the eyebags (dynamic wrinkle numbers and prolapse) was evaluated through preoperative and postoperative photography, whereas the excised lower eyelid skin specimens from 56 patients were investigated with hematoxylin and eosin staining. The modified techniques produced significant improvements in the severity of eyebags in all age groups (P < 0.001). Poor surgical outcome was found to correlate significantly with preoperative dynamic wrinkle numbers (P < 0.001). Age, dynamic wrinkle numbers, and prolapse correlated significantly with dermal fiber density (P = 0.004, 0.000, and 0.000, respectively) but not epidermal, rete ridge, and dermal thickness or the number of rete ridges. In conclusion, modified transcutaneous lower blepharoplasty provides significant improvement to dynamic wrinkles and prolapse in the eyebags. Periorbital aging progressively disturbs the dermal compactness (fiber density) until the structure can no longer hold its integrity at the critical age (around the age of 40).

Eddy Flow during Magma Emplacement: The Basemelt Sill, Antarctica

NASA Astrophysics Data System (ADS)

Petford, N.; Mirhadizadeh, S.

2014-12-01

The McMurdo Dry Valleys magmatic system, Antarctica, forms part of the Ferrar dolerite Large Igneous Province. Comprising a vertical stack of interconnected sills, the complex provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) offers detailed sections through the now frozen particle macrostructure of a congested magma slurry1. Image-based numerical modelling where the intrusion geometry defines its own unique finite element mesh allows simulations of the flow regime to be made that incorporate realistic magma particle size and flow geometries obtained directly from field measurements. One testable outcome relates to the origin of rhythmic layering where analytical results imply the sheared suspension intersects the phase space for particle Reynolds and Peclet number flow characteristic of macroscopic structures formation2. Another relates to potentially novel crystal-liquid segregation due to the formation of eddies locally at undulating contacts at the floor and roof of the intrusion. The eddies are transient and mechanical in origin, unrelated to well-known fluid dynamical effects around obstacles where flow is turbulent. Numerical particle tracing reveals that these low Re number eddies can both trap (remove) and eject particles back into the magma at a later time according to their mass density. This trapping mechanism has potential to develop local variations in structure (layering) and magma chemistry that may otherwise not occur where the contact between magma and country rock is linear. Simulations indicate that eddy formation is best developed where magma viscosity is in the range 1-102 Pa s. Higher viscosities (> 103 Pa s) tend to dampen the effect implying eddy development is most likely a transient feature. However, it is nice to think that something as simple as a bumpy contact could impart physical and by implication chemical diversity in igneous rocks. 1Marsh, D.B. (2004), A magmatic mush column Rosetta stone: the McMurdo Dry Valleys of Antarcica. EOS, 85, 497-502. 2Petford, N. (2009), Which Effective Viscosity? Mineralogical Magazine, 73, 167-191. Fig. 1. Numerical simulation in the geometry showing magma flow field and eddy formation where circulating magma is trapped. Streamlines track particle orbits.

Application of a pore-scale reactive transport model to a natural analog for reaction-induced pore alterations

DOE PAGES

Yoon, Hongkyu; Major, Jonathan; Dewers, Thomas; ...

2017-01-05

Dissolved CO 2 in the subsurface resulting from geological CO 2 storage may react with minerals in fractured rocks, confined aquifers, or faults, resulting in mineral precipitation and dissolution. The overall rate of reaction can be affected by coupled processes including hydrodynamics, transport, and reactions at the (sub) pore-scale. In this work pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous reactions at the mineral surface is applied to account for permeability alterations caused by precipitation-induced pore-blocking. This paper is motivated by observations of CO 2 seeps from a natural CO 2 sequestration analog, Crystal Geyser, Utah. Observations alongmore » the surface exposure of the Little Grand Wash fault indicate the lateral migration of CO 2 seep sites (i.e., alteration zones) of 10–50 m width with spacing on the order of ~100 m over time. Sandstone permeability in alteration zones is reduced by 3–4 orders of magnitude by carbonate cementation compared to unaltered zones. One granular porous medium and one fracture network systems are used to conceptually represent permeable porous media and locations of conduits controlled by fault-segment intersections and/or topography, respectively. Simulation cases accounted for a range of reaction regimes characterized by the Damköhler (Da) and Peclet (Pe) numbers. Pore-scale simulation results demonstrate that combinations of transport (Pe), geochemical conditions (Da), solution chemistry, and pore and fracture configurations contributed to match key patterns observed in the field of how calcite precipitation alters flow paths by pore plugging. This comparison of simulation results with field observations reveals mechanistic explanations of the lateral migration and enhances our understanding of subsurface processes associated with the CO 2 injection. In addition, permeability and porosity relations are constructed from pore-scale simulations which account for a range of reaction regimes characterized by the Da and Pe numbers. Finally, the functional relationships obtained from pore-scale simulations can be used in a continuum scale model that may account for large-scale phenomena mimicking lateral migration of surface CO 2 seeps.« less

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

Yoon, Hongkyu; Major, Jonathan; Dewers, Thomas

Dissolved CO 2 in the subsurface resulting from geological CO 2 storage may react with minerals in fractured rocks, confined aquifers, or faults, resulting in mineral precipitation and dissolution. The overall rate of reaction can be affected by coupled processes including hydrodynamics, transport, and reactions at the (sub) pore-scale. In this work pore-scale modeling of coupled fluid flow, reactive transport, and heterogeneous reactions at the mineral surface is applied to account for permeability alterations caused by precipitation-induced pore-blocking. This paper is motivated by observations of CO 2 seeps from a natural CO 2 sequestration analog, Crystal Geyser, Utah. Observations alongmore » the surface exposure of the Little Grand Wash fault indicate the lateral migration of CO 2 seep sites (i.e., alteration zones) of 10–50 m width with spacing on the order of ~100 m over time. Sandstone permeability in alteration zones is reduced by 3–4 orders of magnitude by carbonate cementation compared to unaltered zones. One granular porous medium and one fracture network systems are used to conceptually represent permeable porous media and locations of conduits controlled by fault-segment intersections and/or topography, respectively. Simulation cases accounted for a range of reaction regimes characterized by the Damköhler (Da) and Peclet (Pe) numbers. Pore-scale simulation results demonstrate that combinations of transport (Pe), geochemical conditions (Da), solution chemistry, and pore and fracture configurations contributed to match key patterns observed in the field of how calcite precipitation alters flow paths by pore plugging. This comparison of simulation results with field observations reveals mechanistic explanations of the lateral migration and enhances our understanding of subsurface processes associated with the CO 2 injection. In addition, permeability and porosity relations are constructed from pore-scale simulations which account for a range of reaction regimes characterized by the Da and Pe numbers. Finally, the functional relationships obtained from pore-scale simulations can be used in a continuum scale model that may account for large-scale phenomena mimicking lateral migration of surface CO 2 seeps.« less

Plume capture by a migrating ridge: Analog geodynamic experiments

NASA Astrophysics Data System (ADS)

Mendez, J. S.; Hall, P.

2010-12-01

Paleomagnetic data from the Hawaii-Emperor Seamount Chain (HESC) suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma but has remained relatively stationary since that time. This implies that the iconic bend in the HESC may in fact reflect the transition from a period of rapid hotspot motion to a stationary state, rather than a change in motion of the Pacific plate. Tarduno et al. (2009) have suggested that this period of rapid hotspot motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been “captured” and tilted by a migrating mid-ocean ridge. We report on a series of analog fluid dynamic experiments designed to characterize the interaction between a migrating spreading center and a thermally buoyant mantle plume. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is modeled using corn syrup introduced into the bottom of the tank from an external, heated, pressurized reservoir. Small (~2 mm diameter), neutrally buoyant Delrin spheres are mixed into reservoir of plume material to aid in visualization. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Experiments are scaled to the Earth's mantle through a combination of a Peclet number and a plume buoyancy number. A range of spreading rates, ridge migration rates, and plume excess temperatures representative of the Earth are considered.

Determining the Transference Number of H[superscript +](aq) by a Modified Moving Boundary Method: A Directed Study for the Undergraduate Physical Chemistry Laboratory

ERIC Educational Resources Information Center

Dabke, Rajeev B.; Gebeyehu, Zewdu; Padelford, Jonathan

2012-01-01

A directed study for the undergraduate physical chemistry laboratory for determining the transference number of H[superscript +](aq) using a modified moving boundary method is presented. The laboratory study combines Faraday's laws of electrolysis with mole ratios and the perfect gas equation. The volume of hydrogen gas produced at the cathode is…

Analysis of turbulent heat transfer, mass transfer, and friction in smooth tubes at high Prandtl and Schmidt numbers

NASA Technical Reports Server (NTRS)

Deissler, Robert G

1955-01-01

The expression for eddy diffusivity from a previous analysis was modified in order to account for the effect of kinematic viscosity on the turbulence in the region close to a wall. By using the modified expression, good agreement was obtained between predicted and experimental results for heat and mass transfer at Prandtl and Schmidt numbers between 0.5 and 3000. The effects of length-to-diameter ratio and of variable viscosity were also investigated for a wide range of Prandtl numbers.

Longitudinal Stability and Drag Characteristics at Mach Numbers from 0.70 to 1.37 of Rocket-propelled Models Having a Modified Triangular Wing

NASA Technical Reports Server (NTRS)

Chapman, Rowe, Jr; Morrow, John D

1952-01-01

A modified triangular wing of aspect ratio 2.53 having an airfoil section 3.7 percent thick at the root and 5.98 percent thick at the tip was designed in an attempt to improve the lift and drag characteristics of triangular wings. Free-flight drag and stability tests were made using rocket-propelled models equipped with the modified wing. The Mach number range of the test was from 0.70 to 1.37. Test results indicated the following: The lift-curve slope of wing plus fuselage approaches the theoretical value of wing alone at supersonic Mach numbers. The drag coefficient, based on total wing area, for wing plus interference was approximately 0.0035 at subsonic Mach numbers and 0.0080 at supersonic Mach numbers. The maximum shift in aerodynamic center for the complete configuration was 14 percent in the rearward direction from the forward position of 51.5 percent of mean aerodynamic chord at subsonic Mach numbers. The variation of lift and moment with angle of attack was linear at supersonic Mach numbers for the range of coefficients covered in the test. The high value of lift-curve slope was considered to be a significant result attributable to the wing modifications.

Modified Hartree-Fock-Bogoliubov theory at finite temperature

NASA Astrophysics Data System (ADS)

Dinh Dang, Nguyen; Arima, Akito

2003-07-01

The modified Hartree-Fock-Bogoliubov (MHFB) theory at finite temperature is derived, which conserves the unitarity relation of the particle-density matrix. This is achieved by constructing a modified-quasiparticle-density matrix, where the fluctuation of the quasiparticle number is microscopically built in. This matrix can be directly obtained from the usual quasiparticle-density matrix by applying the secondary Bogoliubov transformation, which includes the quasiparticle-occupation number. It is shown that, in the limit of constant pairing parameter, the MHFB theory yields the previously obtained modified BCS (MBCS) equations. It is also proved that the modified quasiparticle-random-phase approximation, which is based on the MBCS quasiparticle excitations, conserves the Ikeda sum rule. The numerical calculations of the pairing gap, heat capacity, level density, and level-density parameter within the MBCS theory are carried out for 120Sn. The results show that the superfluid-normal phase transition is completely washed out. The applicability of the MBCS up to a temperature as high as T˜5 MeV is analyzed in detail.

A Novel Method to Generate and Expand Clinical-Grade, Genetically Modified, Tumor-Infiltrating Lymphocytes

PubMed Central

Forget, Marie-Andrée; Tavera, René J.; Haymaker, Cara; Ramachandran, Renjith; Malu, Shuti; Zhang, Minying; Wardell, Seth; Fulbright, Orenthial J.; Toth, Chistopher Leroy; Gonzalez, Audrey M.; Thorsen, Shawne T.; Flores, Esteban; Wahl, Arely; Peng, Weiyi; Amaria, Rodabe N.; Hwu, Patrick; Bernatchez, Chantale

2017-01-01

Following the clinical success achieved with the first generation of adoptive cell therapy (ACT) utilizing in vitro expanded tumor-infiltrating lymphocytes (TILs), the second and third generations of TIL ACT are evolving toward the use of genetically modified TIL. TIL therapy generally involves the transfer of a high number of TIL, ranging from 109 to 1011 cells. One of the technical difficulties in genetically modifying TIL, using a retroviral vector, is the ability to achieve large expansion of transduced TIL, while keeping the technique suitable to a Good Manufacturing Practices (GMP) environment. Consequently, we developed and optimized a novel method for the efficient production of large numbers of GMP-grade, gene-modified TIL for the treatment of patients with ACT. The chemokine receptor CXCR2 was used as the gene of interest for methodology development. The optimized procedure is currently used in the production of gene-modified TIL for two clinical trials for the treatment of metastatic melanoma at MD Anderson Cancer Center. PMID:28824634

[Study on the attenuation of graft versus host disease by methoxy polyethylene glycol modification of donor lymphocytes].

PubMed

Zhang, Quan; Yuan, Yi; Li, Su-Bo; Dou, Na; Ma, Fu-Ling; Ji, Shou-Ping

2004-05-01

To find out why mPEG modification of donor's lymphocytes can attenuate the occurrence of graft versus host disease(GVHD), but not affect the hemopoietic reconstitution of stem/progenitor cells after transplanting the mPEG-modified mononuclear cells from human cord blood into the SCID mice. The followings were observed: (1) Changes of CD4(+) and CD8(+) T cells and the ratio of CD4(+)/CD8(+) T cells were examined by flow cytometry before and after mononuclear cells from human cord blood were modified with mPEG. (2) The difference in forming the CFU-GM in-vitro between the mPEG modified-stem/progenitor cell group and non-modified cell group was observed. (3) The time of appearance of GVHD and the survival of the SCID mice were observed after the pre- and post-modification mononuclear cells were transplanted. (4) The number of humanized CD45(+) cells in the mouse's bone marrow was detected about 7 weeks after transplantation. (1) mPEG nearly completely covered up the CD4 and CD8 antigens on T cells, while the number of CFU-GM did not show any obvious change between the modified and non-modified cell groups. (2) GVHD appeared later in the modified mononuclear cell group than in the non-modified group, and the survival rate was elevated in the modified group than in the non-modified group. (3) Humanized CD45 cells were found in mouse's bone marrow at the 47th day after transplantation of both mPEG-modified and non-modified mononuclear cells. After CD4 and CD8 antigens were covered up with mPEG, the graft's immune response against host was weakened, but the proliferation and differentiation of transplanted hemopoietic stem/progenitor cells were not affected.

Novel Numerical Algorithms for Sensing, Discrimination, and Control

DTIC Science & Technology

1990-03-09

Boas87], and Cross WVD (XWVD) [Boas89]. A modified XWVD is especially useful because it minimizes the number of cross terms or ghosts that corrupt...between real events. If the signal strength is high, then these ghosts may even hide or cover useful returns. We do know that the cross terms can be...modified XWVD is especially useful because it minimizes the number of cross terms or ghosts that corrupt spin rate identification. Autoregressive

Development of a Windbreak Dust Predictive Model and Mitigation Planning Tool

DTIC Science & Technology

2013-12-01

laminar and turbulent flow (Uo = 5 m/s and Ls = 1 cm). Figure 28 Deposition fraction, DF, as a function of Stk * showing the collapse of the artificial...Figure 30 Deposition fraction, DF, as a function of the modified Stokes number ( Stk *). Figure 31 The measured decrease in horizontal PM10 flux, F...concentration. Sb Particle travel distance vi SERDP Strategic Environmental Research and Development Program Stk Stokes number Stk * Modified Stokes

A modified cluster-sampling method for post-disaster rapid assessment of needs.

PubMed Central

Malilay, J.; Flanders, W. D.; Brogan, D.

1996-01-01

The cluster-sampling method can be used to conduct rapid assessment of health and other needs in communities affected by natural disasters. It is modelled on WHO's Expanded Programme on Immunization method of estimating immunization coverage, but has been modified to provide (1) estimates of the population remaining in an area, and (2) estimates of the number of people in the post-disaster area with specific needs. This approach differs from that used previously in other disasters where rapid needs assessments only estimated the proportion of the population with specific needs. We propose a modified n x k survey design to estimate the remaining population, severity of damage, the proportion and number of people with specific needs, the number of damaged or destroyed and remaining housing units, and the changes in these estimates over a period of time as part of the survey. PMID:8823962

All-optical negabinary adders using Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Cherri, A. K.

2011-02-01

In contrast to optoelectronics, all-optical adders are proposed where all-optical signals are used to represent the input numbers and the control signals. In addition, the all-optical adders use the negabinary modified signed-digit number representation (an extension of the negabinary number system) to represent the input digits. Further, the ultra-speed of the designed circuits is achieved due to the use of ultra-fast all-optical switching property of the semiconductor optical amplifier and Mach-Zehnder interferometer (SOA-MZI). Furthermore, two-bit per digit binary encoding scheme is employed to represent the trinary values of the negabinary modified signed-digits.

The use of modified scaling factors in the design of high-power, non-linear, transmitting rod-core antennas

NASA Astrophysics Data System (ADS)

Jordan, Jared Williams; Dvorak, Steven L.; Sternberg, Ben K.

2010-10-01

In this paper, we develop a technique for designing high-power, non-linear, transmitting rod-core antennas by using simple modified scale factors rather than running labor-intensive numerical models. By using modified scale factors, a designer can predict changes in magnetic moment, inductance, core series loss resistance, etc. We define modified scale factors as the case when all physical dimensions of the rod antenna are scaled by p, except for the cross-sectional area of the individual wires or strips that are used to construct the core. This allows one to make measurements on a scaled-down version of the rod antenna using the same core material that will be used in the final antenna design. The modified scale factors were derived from prolate spheroidal analytical expressions for a finite-length rod antenna and were verified with experimental results. The modified scaling factors can only be used if the magnetic flux densities within the two scaled cores are the same. With the magnetic flux density constant, the two scaled cores will operate with the same complex permeability, thus changing the non-linear problem to a quasi-linear problem. We also demonstrate that by holding the number of turns times the drive current constant, while changing the number of turns, the inductance and core series loss resistance change by the number of turns squared. Experimental measurements were made on rod cores made from varying diameters of black oxide, low carbon steel wires and different widths of Metglas foil. Furthermore, we demonstrate that the modified scale factors work even in the presence of eddy currents within the core material.

Acceptable Tolerances for Matching Icing Similarity Parameters in Scaling Applications

NASA Technical Reports Server (NTRS)

Anderson, David N.

2003-01-01

This paper reviews past work and presents new data to evaluate how changes in similarity parameters affect ice shapes and how closely scale values of the parameters should match reference values. Experimental ice shapes presented are from tests by various researchers in the NASA Glenn Icing Research Tunnel. The parameters reviewed are the modified inertia parameter (which determines the stagnation collection efficiency), accumulation parameter, freezing fraction, Reynolds number, and Weber number. It was demonstrated that a good match of scale and reference ice shapes could sometimes be achieved even when values of the modified inertia parameter did not match precisely. Consequently, there can be some flexibility in setting scale droplet size, which is the test condition determined from the modified inertia parameter. A recommended guideline is that the modified inertia parameter be chosen so that the scale stagnation collection efficiency is within 10 percent of the reference value. The scale accumulation parameter and freezing fraction should also be within 10 percent of their reference values. The Weber number based on droplet size and water properties appears to be a more important scaling parameter than one based on model size and air properties. Scale values of both the Reynolds and Weber numbers need to be in the range of 60 to 160 percent of the corresponding reference values. The effects of variations in other similarity parameters have yet to be established.

Comparative impact of genetically modified and non modified maize (Zea mays L.) on succeeding crop and associated weed.

PubMed

Ibrahim, Muhammad; Ahmed, Naseer; Ullah, Faizan; Shinwari, Zabta Khan; Bano, Asghari

2016-04-01

This research work documents the comparative impact of genetically modified (GM) (insect resistance) and non modified maize (Zea mays L.) on growth and germination of succeeding crop wheat (Triticum aestivum L.) and associated weed (Avena fatua L.). The aqueous extracts of both the GM and non-GM maize exhibited higher phenolic content than that of methanolic extracts. Germination percentage and germination index of wheat was significantly decreased by GM methanolic extract (10%) as well as that of non-GM maize at 3% aqueous extract. Similarly germination percentage of weed (Avena fatua L.) was significantly reduced by application of 3% and 5% methanolic GM extracts. All extracts of GM maize showed non-significant effect on the number of roots, root length and shoot length per plant but 5% and 10% methanolic extracts of non-GM maize significantly increased the number of roots per plant of wheat seedling. Similarly, 10% methanolic extract of GM maize significantly increased the number of roots per plant of weed seedling. Methanolic extracts of GM and non-GM maize (3% and 5%) significantly decreased the protease activity in wheat as compared to untreated control. © The Author(s) 2013.

A network of epigenetic modifiers and DNA repair genes controls tissue-specific copy number alteration preference.

PubMed

Cramer, Dina; Serrano, Luis; Schaefer, Martin H

2016-11-10

Copy number alterations (CNAs) in cancer patients show a large variability in their number, length and position, but the sources of this variability are not known. CNA number and length are linked to patient survival, suggesting clinical relevance. We have identified genes that tend to be mutated in samples that have few or many CNAs, which we term CONIM genes (COpy Number Instability Modulators). CONIM proteins cluster into a densely connected subnetwork of physical interactions and many of them are epigenetic modifiers. Therefore, we investigated how the epigenome of the tissue-of-origin influences the position of CNA breakpoints and the properties of the resulting CNAs. We found that the presence of heterochromatin in the tissue-of-origin contributes to the recurrence and length of CNAs in the respective cancer type.

Parity generator and parity checker in the modified trinary number system using savart plate and spatial light modulator

NASA Astrophysics Data System (ADS)

Ghosh, Amal K.

2010-09-01

The parity generators and the checkers are the most important circuits in communication systems. With the development of multi-valued logic (MVL), the proposed system with parity generators and checkers is the most required using the recently developed optoelectronic technology in the modified trinary number (MTN) system. This system also meets up the tremendous needs of speeds by exploiting the savart plates and spatial light modulators (SLM) in the optical tree architecture (OTA).

Assessment of dual-point drag reduction for an executive-jet modified airfoil section

NASA Technical Reports Server (NTRS)

Allison, Dennis O.; Mineck, Raymond E.

1996-01-01

This paper presents aerodynamic characteristics and pressure distributions for an executive-jet modified airfoil and discusses drag reduction relative to a baseline airfoil for two cruise design points. A modified airfoil was tested in the adaptive-wall test section of the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT) for Mach numbers ranging from 0.250 to 0.780 and chord Reynolds numbers ranging from 3.0 x 10(exp 6) to 18.0 x 10(exp 6). The angle of attack was varied from minus 2 degrees to almost 10 degrees. Boundary-layer transition was fixed at 5 percent of chord on both the upper and lower surfaces of the model for most of the test. The two design Mach numbers were 0.654 and 0.735, chord Reynolds numbers were 4.5 x 10(exp 6) and 8.9 x 10(exp 6), and normal-force coefficients were 0.98 and 0.51. Test data are presented graphically as integrated force and moment coefficients and chordwise pressure distributions. The maximum normal-force coefficient decreases with increasing Mach number. At a constant normal-force coefficient in the linear region, as Mach number increases an increase occurs in the slope of normal-force coefficient versus angle of attack, negative pitching-moment coefficient, and drag coefficient. With increasing Reynolds number at a constant normal-force coefficient, the pitching-moment coefficient becomes more negative and the drag coefficient decreases. The pressure distributions reveal that when present, separation begins at the trailing edge as angle of attack is increased. The modified airfoil, which is designed with pitching moment and geometric constraints relative to the baseline airfoil, achieved drag reductions for both design points (12 and 22 counts). The drag reductions are associated with stronger suction pressures in the first 10 percent of the upper surface and weakened shock waves.

7 CFR 900.54 - Docket number.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 8 2011-01-01 2011-01-01 false Docket number. 900.54 Section 900.54 Agriculture... Governing Proceedings on Petitions To Modify or To Be Exempted From Marketing Orders § 900.54 Docket number. Each proceeding, immediately following its institution, shall be assigned a docket number by the...

7 CFR 900.54 - Docket number.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 8 2012-01-01 2012-01-01 false Docket number. 900.54 Section 900.54 Agriculture... Governing Proceedings on Petitions To Modify or To Be Exempted From Marketing Orders § 900.54 Docket number. Each proceeding, immediately following its institution, shall be assigned a docket number by the...

7 CFR 900.54 - Docket number.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 8 2010-01-01 2010-01-01 false Docket number. 900.54 Section 900.54 Agriculture... Governing Proceedings on Petitions To Modify or To Be Exempted From Marketing Orders § 900.54 Docket number. Each proceeding, immediately following its institution, shall be assigned a docket number by the...

7 CFR 900.54 - Docket number.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 8 2014-01-01 2014-01-01 false Docket number. 900.54 Section 900.54 Agriculture... Governing Proceedings on Petitions To Modify or To Be Exempted From Marketing Orders § 900.54 Docket number. Each proceeding, immediately following its institution, shall be assigned a docket number by the...

7 CFR 900.54 - Docket number.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 8 2013-01-01 2013-01-01 false Docket number. 900.54 Section 900.54 Agriculture... Governing Proceedings on Petitions To Modify or To Be Exempted From Marketing Orders § 900.54 Docket number. Each proceeding, immediately following its institution, shall be assigned a docket number by the...

Span efficiency of wings with leading edge protuberances

NASA Astrophysics Data System (ADS)

Custodio, Derrick; Henoch, Charles; Johari, Hamid

2013-11-01

Past work has shown that sinusoidal leading edge protuberances resembling those found on humpback whale flippers alter the lift and drag coefficients of full- and finite-span foils and wings depending on the angle of attack and leading edge geometry. Although the load characteristics of protuberance modified finite-span wings have been reported for flipper-like geometries at higher Reynolds numbers and for rectangular planforms at lower Reynolds numbers, the effects of leading edge geometry on the span efficiency, which is indicative of the deviation of the spanwise lift distribution from elliptical and the viscous effects, for a range of planforms and Reynolds numbers have not been addressed. The lift and drag coefficients of 7 rectangular, 2 swept, and 2 flipper-like planform models with aspect ratios of 4.3, 4.0, and 8.86, respectively, were used to compute the span efficiency at Reynolds numbers ranging from 0.9 to 4.5 × 105. The span efficiency, based on the data at lower angles of attack, of modified wings was compared with the unmodified models. For the cases considered, the span efficiencies of the leading edge modified models were less than those of the equivalent unmodified models. The dependence of span efficiency on the leading edge geometry, planform, and Reynolds number will be presented. Supported by the ONR-ULI program.

Efficient Residue to Binary Conversion Based on a Modified Flexible Moduli Set

NASA Astrophysics Data System (ADS)

Molahosseini, Amir Sabbagh

2011-09-01

The Residue Number System (RNS) is a non-weighted number system which can perform addition (subtraction) and multiplication on residues without carry-propagation; resulting in high-speed hardware implementations of computation systems. The problem of converting residue numbers to equivalent binary weighted form has been attracted a lot of research for many years. Recently, some researchers proposed using flexible moduli sets instead of previous traditional moduli sets to enhance the performance of residue to binary converters. This paper introduces the modified flexible moduli set {22p+k. 22p+1, 2p+1, 2p-1} which is achieved from the flexible set {2p+k, 22p+1, 2p+1, 2p-1} by enhancing modulo 2p+k. Next, new Chinese remainder theorem-1 is used to design simple and efficient residue to binary converter for this modified set with better performance than the converter of the moduli set {2p+k, 22p+1, 2p+1, 2p-1}.

Modified Dempster-Shafer approach using an expected utility interval decision rule

NASA Astrophysics Data System (ADS)

Cheaito, Ali; Lecours, Michael; Bosse, Eloi

1999-03-01

The combination operation of the conventional Dempster- Shafer algorithm has a tendency to increase exponentially the number of propositions involved in bodies of evidence by creating new ones. The aim of this paper is to explore a 'modified Dempster-Shafer' approach of fusing identity declarations emanating form different sources which include a number of radars, IFF and ESM systems in order to limit the explosion of the number of propositions. We use a non-ad hoc decision rule based on the expected utility interval to select the most probable object in a comprehensive Platform Data Base containing all the possible identity values that a potential target may take. We study the effect of the redistribution of the confidence levels of the eliminated propositions which otherwise overload the real-time data fusion system; these eliminated confidence levels can in particular be assigned to ignorance, or uniformly added to the remaining propositions and to ignorance. A scenario has been selected to demonstrate the performance of our modified Dempster-Shafer method of evidential reasoning.

WE-AB-204-07: Spatiotemporal Distribution of the FDG PET Tracer in Solid Tumors: Contributions of Diffusion and Convection Mechanisms

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

Soltani, M; Sefidgar, M; Bazmara, H

2015-06-15

Purpose: In this study, a mathematical model is utilized to simulate FDG distribution in tumor tissue. In contrast to conventional compartmental modeling, tracer distributions across space and time are directly linked together (i.e. moving beyond ordinary differential equations (ODEs) to utilizing partial differential equations (PDEs) coupling space and time). The diffusion and convection transport mechanisms are both incorporated to model tracer distribution. We aimed to investigate the contributions of these two mechanisms on FDG distribution for various tumor geometries obtained from PET/CT images. Methods: FDG transport was simulated via a spatiotemporal distribution model (SDM). The model is based on amore » 5K compartmental model. We model the fact that tracer concentration in the second compartment (extracellular space) is modulated via convection and diffusion. Data from n=45 patients with pancreatic tumors as imaged using clinical FDG PET/CT imaging were analyzed, and geometrical information from the tumors including size, shape, and aspect ratios were classified. Tumors with varying shapes and sizes were assessed in order to investigate the effects of convection and diffusion mechanisms on FDG transport. Numerical methods simulating interstitial flow and solute transport in tissue were utilized. Results: We have shown the convection mechanism to depend on the shape and size of tumors whereas diffusion mechanism is seen to exhibit low dependency on shape and size. Results show that concentration distribution of FDG is relatively similar for the considered tumors; and that the diffusion mechanism of FDG transport significantly dominates the convection mechanism. The Peclet number which shows the ratio of convection to diffusion rates was shown to be of the order of 10−{sup 3} for all considered tumors. Conclusion: We have demonstrated that even though convection leads to varying tracer distribution profiles depending on tumor shape and size, the domination of the diffusion phenomenon prevents these factors from modulating FDG distribution.« less

Mathematical modeling of sample stacking methods in microfluidic systems

NASA Astrophysics Data System (ADS)

Horek, Jon

Gradient focusing methods are a general class of experimental techniques used to simultaneously separate and increase the cross-sectionally averaged concentration of charged particle mixtures. In comparison, Field Amplified Sample Stacking (FASS) techniques first concentrate the collection of molecules before separating them. Together, we denote gradient focusing and FASS methods "sample stacking" and study the dynamics of a specific method, Temperature Gradient Focusing (TGF), in which an axial temperature gradient is applied along a channel filled with weak buffer. Gradients in electroosmotic fluid flow and electrophoretic species velocity create the simultaneous separating and concentrating mechanism mentioned above. In this thesis, we begin with the observation that very little has been done to model the dynamics of gradient focusing, and proceed to solve the fundamental equations of fluid mechanics and scalar transport, assuming the existence of slow axial variations and the Taylor-Aris dispersion coefficient. In doing so, asymptotic methods reduce the equations from 3D to 1D, and we arrive at a simple 1D model which can be used to predict the transient evolution of the cross-sectionally averaged analyte concentration. In the second half of this thesis, we run several numerical focusing experiments with a 3D finite volume code. Comparison of the 1D theory and 3D simulations illustrates not only that the asymptotic theory converges as a certain parameter tends to zero, but also that fairly large axial slip velocity gradients lead to quite small errors in predicted steady variance. Additionally, we observe that the axial asymmetry of the electrophoretic velocity model leads to asymmetric peak shapes, a violation of the symmetric Gaussians predicted by the 1D theory. We conclude with some observations on the effect of Peclet number and gradient strength on the performance of focusing experiments, and describe a method for experimental optimization. Such knowledge is useful for design of lab-on-a-chip devices.

Karst-on-a-chip: microfluidic studies of dissolution of a gypsum fracture

NASA Astrophysics Data System (ADS)

Szymczak, Piotr; Dutka, Filip; Osselin, Florian

2017-04-01

Dissolution of fractured and porous media introduces a positive feedback between fluid transport and chemical reactions at mineral surfaces leading to self-focusing of the flow in pronounced wormhole-like channels [1,2]. We study the flow-induced dissolution in a simple microfluidic setup, with a gypsum block inserted in between two polycarbonate plates, which is the simplest model of a fracture [3]. This gives us a unique opportunity to observe the evolution of the dissolution patterns in-situ and in real-time. By changing the flow rate and the aperture of the fracture we can scan a relatively wide range of Peclet and Damkohler numbers, characterizing the relative magnitude of advection, diffusion and reaction in the system. Additionally, as the aperture is increased, a transition is observed between the fractal and regular dissolution patterns. For small gaps, the patterns are ramified fractals. For larger gaps, the dissolution fingers are found to have regular forms of two different kinds: either linear (for high flow rates) or parabolic (for lower flow rates). The experiments are supplemented with numerical simulations and analytical modeling which allow for a better understanding of evolving flow patterns. In particular, we find the shapes and propagation velocities of dominant fingers for different widths of the system, flow rates and reaction rates. Finally, we comment on the link between the experimentally observed patterns and the natural karst systems - both cave conduits and epikarst solution pipes. [1] Hoefner, M. L. and Fogler, H. S. Pore evolution and channel formation during flow and reaction in porous media. AIChE J. 34, 45-54, 1988 [2] P. Szymczak, A. J. C. Ladd, Wormhole formation in dissolving fractures, J. Geophys. Res., 114, B06203, 2009 [3] F. Osselin, P. Kondratiuk, A Budek, O. Cybulski, P. Garstecki, P. Szymczak Microfluidic observation of the onset of reactive infiltration instability in an analog fracture, Geophys. Res. Lett., 43, 6907-6915, 2016

An analytical model to predict interstitial lubrication of cartilage in migrating contact areas.

PubMed

Moore, A C; Burris, D L

2014-01-03

For nearly a century, articular cartilage has been known for its exceptional tribological properties. For nearly as long, there have been research efforts to elucidate the responsible mechanisms for application toward biomimetic bearing applications. It is now widely accepted that interstitial fluid pressurization is the primary mechanism responsible for the unusual lubrication and load bearing properties of cartilage. Although the biomechanics community has developed elegant mathematical theories describing the coupling of solid and fluid (biphasic) mechanics and its role in interstitial lubrication, quantitative gaps in our understanding of cartilage tribology have inhibited our ability to predict how tribological conditions and material properties impact tissue function. This paper presents an analytical model of the interstitial lubrication of biphasic materials under migrating contact conditions. Although finite element and other numerical models of cartilage mechanics exist, they typically neglect the important role of the collagen network and are limited to a specific set of input conditions, which limits general applicability. The simplified approach taken in this work aims to capture the broader underlying physics as a starting point for further model development. In agreement with existing literature, the model indicates that a large Peclet number, Pe, is necessary for effective interstitial lubrication. It also predicts that the tensile modulus must be large relative to the compressive modulus. This explains why hydrogels and other biphasic materials do not provide significant interstitial pressure under high Pe conditions. The model quantitatively agrees with in-situ measurements of interstitial load support and the results have interesting implications for tissue engineering and osteoarthritis problems. This paper suggests that a low tensile modulus (from chondromalacia or local collagen rupture after impact, for example) may disrupt interstitial pressurization, increase shear stresses, and activate a condition of progressive surface damage as a potential precursor of osteoarthritis. © 2013 Elsevier Ltd. All rights reserved.

Upscaling mixing in porous media from an experimental quantification of pore scale Lagrangian deformation statistics

NASA Astrophysics Data System (ADS)

Turuban, R.; Jimenez-Martinez, J.; De Anna, P.; Tabuteau, H.; Meheust, Y.; Le Borgne, T.

2014-12-01

As dissolved chemical elements are transported in the subsurface, their mixing with other compounds and potential reactivity depends on the creation of local scale chemical gradients, which ultimately drive diffusive mass transfer and reaction. The distribution of concentration gradients is in turn shaped by the spatial gradients of flow velocity arising from the random distribution of solid grains. We present an experimental investigation of the relationship between the microscale flow stretching properties and the effective large scale mixing dynamics in porous media. We use a flow cell that models a horizontal quasi two-dimensional (2D) porous medium, the grains of which are cylinders randomly positioned between two glass plates [de Anna et al. 2013]. In this setup, we perform both non diffusive and diffusive transport tests, by injecting respectively microsphere solid tracers and a fluorescent dye. While the dye front propagates through the medium, it undergoes in time a kinematic stretching that is controlled by the flow heterogeneity, as it encounters stagnation zones and high velocity channels between the grains. The spatial distribution of the dye can then be described as a set of stretched lamellae whose rate of diffusive smoothing is locally enhanced by kinematic stretching [Le Borgne et al., 2013]. We show that this representation allows predicting the temporal evolution of the mixing rate and the probability distribution of concentration gradients for a range of Peclet numbers. This upscaling framework hence provides a quantification of the dynamics of effective mixing from the microscale Lagrangian velocity statistics. References:[1] P. de Anna, J. Jimenez-Martinez, H. Tabuteau, R. Turuban, T. Le Borgne, M. Derrien,and Yves Méheust, Mixing and reaction kinetics in porous media : an experimental pore scale quantification, Environ. Sci. Technol. 48, 508-516, 2014. [2] Le Borgne, T., M. Dentz, E. Villermaux, Stretching, coalescence and mixing in porous media, Phys. Rev. Lett., 110, 204501 (2013)

Validation and Development of a Modified Breast Graded Prognostic Assessment As a Tool for Survival in Patients With Breast Cancer and Brain Metastases.

PubMed

Subbiah, Ishwaria M; Lei, Xiudong; Weinberg, Jeffrey S; Sulman, Erik P; Chavez-MacGregor, Mariana; Tripathy, Debu; Gupta, Rohan; Varma, Ankur; Chouhan, Jay; Guevarra, Richard P; Valero, Vicente; Gilbert, Mark R; Gonzalez-Angulo, Ana M

2015-07-10

Several indices have been developed to predict overall survival (OS) in patients with breast cancer with brain metastases, including the breast graded prognostic assessment (breast-GPA), comprising age, tumor subtype, and Karnofsky performance score. However, number of brain metastases-a highly relevant clinical variable-is less often incorporated into the final model. We sought to validate the existing breast-GPA in an independent larger cohort and refine it integrating number of brain metastases. Data were retrospectively gathered from a prospectively maintained institutional database. Patients with newly diagnosed brain metastases from 1996 to 2013 were identified. After validating the breast-GPA, multivariable Cox regression and recursive partitioning analysis led to the development of the modified breast-GPA. The performances of the breast-GPA and modified breast-GPA were compared using the concordance index. In our cohort of 1,552 patients, the breast-GPA was validated as a prognostic tool for OS (P < .001). In multivariable analysis of the breast-GPA and number of brain metastases (> three v ≤ three), both were independent predictors of OS. We therefore developed the modified breast-GPA integrating a fourth clinical parameter. Recursive partitioning analysis reinforced the prognostic significance of these four factors. Concordance indices were 0.78 (95% CI, 0.77 to 0.80) and 0.84 (95% CI, 0.83 to 0.85) for the breast-GPA and modified breast-GPA, respectively (P < .001). The modified breast-GPA incorporates four simple clinical parameters of high prognostic significance. This index has an immediate role in the clinic as a formative part of the clinician's discussion of prognosis and direction of care and as a potential patient selection tool for clinical trials. © 2015 by American Society of Clinical Oncology.

Direct Demonstration of the Concept of Unrestricted Effective-Medium Approximation

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Dlugach, Zhanna M.; Zakharova, Nadezhda T.

2014-01-01

The modified unrestricted effective-medium refractive index is defined as one that yields accurate values of a representative set of far-field scattering characteristics (including the scattering matrix) for an object made of randomly heterogeneous materials. We validate the concept of the modified unrestricted effective-medium refractive index by comparing numerically exact superposition T-matrix results for a spherical host randomly filled with a large number of identical small inclusions and Lorenz-Mie results for a homogeneous spherical counterpart. A remarkable quantitative agreement between the superposition T-matrix and Lorenz-Mie scattering matrices over the entire range of scattering angles demonstrates unequivocally that the modified unrestricted effective-medium refractive index is a sound (albeit still phenomenological) concept provided that the size parameter of the inclusions is sufficiently small and their number is sufficiently large. Furthermore, it appears that in cases when the concept of the modified unrestricted effective-medium refractive index works, its actual value is close to that predicted by the Maxwell-Garnett mixing rule.

On large time step TVD scheme for hyperbolic conservation laws and its efficiency evaluation

NASA Astrophysics Data System (ADS)

Qian, ZhanSen; Lee, Chun-Hian

2012-08-01

A large time step (LTS) TVD scheme originally proposed by Harten is modified and further developed in the present paper and applied to Euler equations in multidimensional problems. By firstly revealing the drawbacks of Harten's original LTS TVD scheme, and reasoning the occurrence of the spurious oscillations, a modified formulation of its characteristic transformation is proposed and a high resolution, strongly robust LTS TVD scheme is formulated. The modified scheme is proven to be capable of taking larger number of time steps than the original one. Following the modified strategy, the LTS TVD schemes for Yee's upwind TVD scheme and Yee-Roe-Davis's symmetric TVD scheme are constructed. The family of the LTS schemes is then extended to multidimensional by time splitting procedure, and the associated boundary condition treatment suitable for the LTS scheme is also imposed. The numerical experiments on Sod's shock tube problem, inviscid flows over NACA0012 airfoil and ONERA M6 wing are performed to validate the developed schemes. Computational efficiencies for the respective schemes under different CFL numbers are also evaluated and compared. The results reveal that the improvement is sizable as compared to the respective single time step schemes, especially for the CFL number ranging from 1.0 to 4.0.

Internal-Modified Dithiol DNA-Directed Au Nanoassemblies: Geometrically Controlled Self-Assembly and Quantitative Surface-Enhanced Raman Scattering Properties

NASA Astrophysics Data System (ADS)

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-11-01

In this work, a hierarchical DNA-directed self-assembly strategy to construct structure-controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal-modified dithiol single-strand DNA (ssDNA) (Au-B-A or A-B-Au-B-A). It is found that the dithiol-ssDNA-modified Au NPs and molecule quantity of thiol-modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au-DNA self-assembly units, geometrical structures of the Au NAs can be tailored from one-dimensional (1D) to quasi-2D and 2D. Au-B-A conjugates readily give 1D and quasi-2D Au NAs while 2D Au NAs can be formed by A-B-Au-B-A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite-difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”-number-depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique.

The 'modified prone position': a new approach for treating pre-vesical stones with extracorporeal shock wave lithotripsy.

PubMed

Köse, A C; Demirbas, M

2004-02-01

To investigate the utility of a new 'modified-prone' position for treating pre-vesical stones with extracorporeal shock wave lithotripsy (ESWL), usually considered an acceptable and effective treatment for such stones, but for which many different body positions have been used in an attempt to increase its efficacy. The study included 268 consecutive patients with a solitary pre-vesical stone who underwent ESWL either prone (69) or in the modified-prone position (199) between May 1999 and August 2001. Only those with one stone between the ureteric orifice and 1 cm proximal to the vesico-ureteric junction were included. In each case the stone diameter, days to stone clearance, number of shock waves applied per treatment, and number of sessions required to become stone-free were recorded. If the treatment failed this was also noted. Success rates in the prone and modified-prone groups were compared and analysed to assess which of the variables influenced success with ESWL. After ESWL, 95.5% of the 268 patients were stone-free; the rates in the prone and modified-prone groups were 89.9% and 97.5%, respectively (P = 0.015). The probability of success with ESWL therapy for pre-vesical calculi in modified-prone position was about five times (odds ratio 4.56, 95% confidence interval 1.2-17.7) greater than that expected with when prone. The modified-prone position was an independent factor most significantly influencing success with ESWL in these patients. The modified-prone position for ESWL is a new and very effective way to treat patients with pre-vesical stones.

Mass transfer of nonvolatile organic compounds from porous media

NASA Astrophysics Data System (ADS)

Khachikian, Crist Simon

This thesis presents data pertaining to the mass transfer of nonvolatile organic compounds from porous media. Physical properties of porous solids, including surface and pore areas, are studied. Information from these studies, along with dissolution data, are used to develop correlations relating the Sherwood Number to the Peclet Number. The contaminant used in this study is naphthalene; the solids used are Moffett Sand (MS), Borden Sand (BS), Lampblack (LB), and Silica Gel (SG). Surface area results indicate that contamination at 0.1% reduces the area of MS and SG by 48 and 37%, respectively, while contamination at 1.0% reduces the area of MS, BS, and SG by 59, 56, and 40%, respectively. Most of the reduction in area originates in the reduction of pore areas and volumes, where the contaminant precipitates. After long-term storage, surface areas did not recover to their original values due to an "irreversible" fraction of naphthalene. Treatment with heat or solvent or both was necessary to completely remove the contamination. For lampblack, treatment at 100°C decreased areas while treatment at 250°C increased them. Treatment at 250°°C probably opened pores while that at 100°C may have blocked more pores by redistributing the tar-like contaminant characteristic of lampblack. Contaminated MS and SG solids are packed in columns through which water is pumped. The effluent began at a relatively high concentration (˜70% of solubility) for both samples. However, SG column concentrations dropped quickly, never achieving steady state while the MS samples declined more gradually towards steady state. The high pore areas of the SG samples are believed to cause this behavior. The steady state portion of the MS dissolution history is used to develop mass transfer correlations. The correlation in this study differs from previous work in two major ways: (1) the exponent on the Pe is three times larger and (2) the limiting Sh is 106 times smaller. These results suggest that the dissolution mechanism here is different than in other studies, that is, dissolution is occurring from the contaminated pores which are inaccessible to the flowing water. This work can be used to assess the leaching potential of non-volatile organic impacted soils. Also, soil vapor extraction schemes which are hampered by observed long tails can be explained using the data in this thesis.

The Dynamics of Miscible Interfaces: A Space Flight Experiment

NASA Technical Reports Server (NTRS)

Maxworthy, Tony; Meiburg, Eckart

2000-01-01

Experiments as well as accompanying simulations are described that serve in preparation of a space flight experiment to study the dynamics of miscible interfaces. The investigation specifically addresses the importance of both nonsolenoidal effects as well as nonconventional Korteweg stresses in flows that give rise to steep but finite concentration gradients. The investigation focuses on the flow in which a less viscous fluid displaces one of higher viscosity and different density within a narrow capillary tube. The fluids are miscible in all proportions. An intruding finger forms that occupies a fraction of the total tube diameter. Depending on the flow conditions, as expressed by the Peclet number, a dimensionless viscosity ratio, and a gravity parameter, this fraction can vary between approximately 0.9 and 0.2. For large Pe values, a quasi-steady finger forms, which persists for a time of O(Pe) before it starts to decay, and Poiseuille flow and Taylor dispersion are approached asymptotically. Depending on the specific flow conditions, we observe a variety of topologically different streamline patterns, among them some that leak fluid from the finger tip. For small Pe values, the flow decays from the start and asymptotically reaches Taylor dispersion after a time of O(Pe). Comparisons between experiments and numerical simulations based on the 'conventional' assumption of solenoidal velocity fields and without Korteweg stresses yield poor agreement as far as the Pe value is concerned that distinguishes these two regimes. As one possibility, we attribute this lack of agreement to the disregard of these terms. An attempt is made to use scaling arguments in order to evaluate the importance of the Korteweg stresses and of the assumption of solenoidality. While these effects should be strongest in absolute terms when steep concentration fronts exist, i.e., at large Pe, they may be relatively most important at lower values of Pe. We subsequently compare these conventional simulations to more complete simulations that account for nonvanishing divergence as well as Korteweg stresses. While the exact value of the relevant stress coefficients are not known, ballpark numbers do exist, and their use in the simulations indicates that these stresses may indeed be important. We plan to evaluate these issues in detail by means of comparing a space experiment with corresponding simulations, in order to extract more accurate Korteweg stress coefficients, and to confirm or deny the importance of such stresses.

Field test method to determine presence and quantity of modifiers in liquid asphalt - follow-up data analysis.

DOT National Transportation Integrated Search

2015-08-01

In an earlier study under the contract grant number BDV25-977-06, two portable Fourier transform infrared spectrometer : (FTIR) were evaluated for their ability to quickly detect and/or quantify the presence of polymer modifiers, including styrene : ...

40 CFR 172.48 - Data requirements for a notification.

Code of Federal Regulations, 2010 CFR

2010-07-01

... PROGRAMS EXPERIMENTAL USE PERMITS Notification for Certain Genetically Modified Microbial Pesticides § 172... methods used to genetically modify the microbial pesticide. (h) The identity and location of the gene... organisms. (d) Information on survival and the ability of the microbial pesticide to increase in numbers...

Results of dynamic stability tests conducted on a .012 scale model modified 089 B shuttle orbiter in the AEDC-VKF tunnel B at a Mach number of 8.0 (LA42)

NASA Technical Reports Server (NTRS)

Vaughn, J. E.; Daviet, J. T.

1975-01-01

Experimental aerodynamic investigations were conducted on a .012 scale model of a NASA/Langley modified version of the Rockwell 089B Space Shuttle Orbiter. Using the forced oscillation test technique, dynamic stability derivatives were measured in the pitch, yaw and roll planes at a Mach number of 8 over an angle of attack range from -4 deg to 28 deg. Plotted and tabulated results are presented.

Extension of modified power method to two-dimensional problems

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

Zhang, Peng; Ulsan National Institute of Science and Technology, 50 UNIST-gil, Ulsan 44919; Lee, Hyunsuk

2016-09-01

In this study, the generalized modified power method was extended to two-dimensional problems. A direct application of the method to two-dimensional problems was shown to be unstable when the number of requested eigenmodes is larger than a certain problem dependent number. The root cause of this instability has been identified as the degeneracy of the transfer matrix. In order to resolve this instability, the number of sub-regions for the transfer matrix was increased to be larger than the number of requested eigenmodes; and a new transfer matrix was introduced accordingly which can be calculated by the least square method. Themore » stability of the new method has been successfully demonstrated with a neutron diffusion eigenvalue problem and the 2D C5G7 benchmark problem. - Graphical abstract:.« less

Modified signed-digit arithmetic based on redundant bit representation.

PubMed

Huang, H; Itoh, M; Yatagai, T

1994-09-10

Fully parallel modified signed-digit arithmetic operations are realized based on redundant bit representation of the digits proposed. A new truth-table minimizing technique is presented based on redundant-bitrepresentation coding. It is shown that only 34 minterms are enough for implementing one-step modified signed-digit addition and subtraction with this new representation. Two optical implementation schemes, correlation and matrix multiplication, are described. Experimental demonstrations of the correlation architecture are presented. Both architectures use fixed minterm masks for arbitrary-length operands, taking full advantage of the parallelism of the modified signed-digit number system and optics.

ASSESSMENT OF ALLERGENIC POTENTIAL OF GENETICALLY MODIFIED FOODS: AN AGENDA FOR FUTURE RESEARCH

EPA Science Inventory

Abstract
Speakers and participants in the Workshop Assessment of the Allergenic Potential of Genetically Modified Foods met in breakout groups to discuss a number of issues including needs for future research. There was agreement that research should move forward quickly in t...

Effect of Phthalic Anhydride Modified Soy Protein on Viscoelastic Properties of Polymer Composites

USDA-ARS?s Scientific Manuscript database

Phthalic anhydride (PA) modified soy protein isolates (SPI), both hydrolyzed and un-hydrolyzed, are investigated as reinforcement fillers in styrene-butadiene (SB) composites. The modification of SPI by PA increases the number of carboxylic acid functional groups on the protein surface and therefor...

EFFECT OF SOIL MODIFYING FACTORS ON THE BIOAVAILABILITY AND TOXICITY OF METAL CONTAMINATED SOILS

EPA Science Inventory

Heavy metal and organic chemical contamination of soils is a worldwide problem posing a risk to humans and more directly, soil organisms. Metal toxicity is often not directly related to the total concentration of metals present due to a number of modifying factors that depend,...

Mycophenolate Mofetil Treatment of Systemic Sclerosis Reduces Myeloid Cell Numbers and Attenuates the Inflammatory Gene Signature in Skin.

PubMed

Hinchcliff, Monique; Toledo, Diana M; Taroni, Jaclyn N; Wood, Tammara A; Franks, Jennifer M; Ball, Michael S; Hoffmann, Aileen; Amin, Sapna M; Tan, Ainah U; Tom, Kevin; Nesbeth, Yolanda; Lee, Jungwha; Ma, Madeleine; Aren, Kathleen; Carns, Mary A; Pioli, Patricia A; Whitfield, Michael L

2018-01-31

Fewer than half of patients with systemic sclerosis demonstrate modified Rodnan skin score improvement during mycophenolate mofetil (MMF) treatment. To understand the molecular basis for this observation, we extended our prior studies and characterized molecular and cellular changes in skin biopsies from subjects with systemic sclerosis treated with MMF. Eleven subjects completed ≥24 months of MMF therapy. Two distinct skin gene expression trajectories were observed across six of these subjects. Three of the six subjects showed attenuation of the inflammatory signature by 24 months, paralleling reductions in CCL2 mRNA expression in skin and reduced numbers of macrophages and myeloid dendritic cells in skin biopsies. MMF cessation at 24 months resulted in an increased inflammatory score, increased CCL2 mRNA and protein levels, modified Rodnan skin score rebound, and increased numbers of skin myeloid cells in these subjects. In contrast, three other subjects remained on MMF >24 months and showed a persistent decrease in inflammatory score, decreasing or stable modified Rodnan skin score, CCL2 mRNA reductions, sera CCL2 protein levels trending downward, reduction in monocyte migration, and no increase in skin myeloid cell numbers. These data summarize molecular changes during MMF therapy that suggest reduction of innate immune cell numbers, possibly by attenuating expression of chemokines, including CCL2. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Aerodynamic Performance and Static Stability at Mach Number 3.3 of an Aircraft Configuration Employing Three Triangular Wing Panels and a Body Equal Length

NASA Technical Reports Server (NTRS)

James, Carlton S.

1960-01-01

An aircraft configuration, previously conceived as a means to achieve favorable aerodynamic stability characteristics., high lift-drag ratio, and low heating rates at high supersonic speeds., was modified in an attempt to increase further the lift-drag ratio without adversely affecting the other desirable characteristics. The original configuration consisted of three identical triangular wing panels symmetrically disposed about an ogive-cylinder body equal in length to the root chord of the panels. This configuration was modified by altering the angular disposition of the wing panels, by reducing the area of the panel forming the vertical fin, and by reshaping the body to produce interference lift. Six-component force and moment tests of the modified configuration at combined angles of attack and sideslip were made at a Mach number of 3.3 and a Reynolds number of 5.46 million. A maximum lift-drag ratio of 6.65 (excluding base drag) was measured at a lift coefficient of 0.100 and an angle of attack of 3.60. The lift-drag ratio remained greater than 3 up to lift coefficient of 0.35. Performance estimates, which predicted a maximum lift-drag ratio for the modified configuration 27 percent greater than that of the original configuration, agreed well with experiment. The modified configuration exhibited favorable static stability characteristics within the test range. Longitudinal and directional centers of pressure were slightly aft of the respective centroids of projected plan-form and side area.

Handgrip strength and associated factors in hospitalized patients.

PubMed

Guerra, Rita S; Fonseca, Isabel; Pichel, Fernando; Restivo, Maria T; Amaral, Teresa F

2015-03-01

Handgrip strength (HGS) is a marker of nutrition status. Many factors are associated with HGS. Age, height, body mass index, number of diagnoses, and number and type of drugs have been shown to modify the association between undernutrition and HGS. Nevertheless, other patient characteristics that could modify this association and its joint modifier effect have not been studied yet. To evaluate the association of inpatients' HGS and undernutrition considering the potential modifier effect of cognitive status, functional activity, disease severity, anthropometrics, and other patient characteristics on HGS. A cross-sectional study was conducted in a university hospital. Sex, age, abbreviated mental test score, functional activity score, Charlson index, number of drugs, Patient-Generated Subjective Global Assessment (PG-SGA) score, body weight, mid-arm muscle circumference, adductor pollicis muscle thickness, body height, wrist circumference, hand length, and palm width were included in a linear regression model to identify independent factors associated with HGS (dependent variable). The study sample was composed of 688 inpatients (18-91 years old). All variables included in the model were associated with HGS (β, -0.16 to 0.38; P ≤ .049) and explained 68.5% of HGS. Age, functional activity decline, Charlson index, number of drugs, PG-SGA score, body weight, and wrist circumference had a negative association with HGS. All other studied variables were positively associated with HGS. Nutrition status evaluated by PG-SGA was still associated with HGS after considering the joint effect of other patient characteristics, which reinforces the value of HGS as an indicator of undernutrition. © 2013 American Society for Parenteral and Enteral Nutrition.

Mechanical Slosh Models for Rocket-Propelled Spacecraft

NASA Technical Reports Server (NTRS)

Jang, Jiann-Woei; Alaniz, Abram; Yang, Lee; Powers. Joseph; Hall, Charles

2013-01-01

Several analytical mechanical slosh models for a cylindrical tank with flat bottom are reviewed. Even though spacecrafts use cylinder shaped tanks, most of those tanks usually have elliptical domes. To extend the application of the analytical models for a cylindrical tank with elliptical domes, the modified slosh parameter models are proposed in this report by mapping an elliptical dome cylindrical tank to a flat top/bottom cylindrical tank while maintaining the equivalent liquid volume. For the low Bond number case, the low-g slosh models were also studied. Those low-g models can be used for Bond number > 10. The current low-g slosh models were also modified to extend their applications for the case that liquid height is smaller than the tank radius. All modified slosh models are implemented in MATLAB m-functions and are collected in the developed MST (Mechanical Slosh Toolbox).

Hybrid Modified K-Means with C4.5 for Intrusion Detection Systems in Multiagent Systems

PubMed Central

Laftah Al-Yaseen, Wathiq; Ali Othman, Zulaiha; Ahmad Nazri, Mohd Zakree

2015-01-01

Presently, the processing time and performance of intrusion detection systems are of great importance due to the increased speed of traffic data networks and a growing number of attacks on networks and computers. Several approaches have been proposed to address this issue, including hybridizing with several algorithms. However, this paper aims at proposing a hybrid of modified K-means with C4.5 intrusion detection system in a multiagent system (MAS-IDS). The MAS-IDS consists of three agents, namely, coordinator, analysis, and communication agent. The basic concept underpinning the utilized MAS is dividing the large captured network dataset into a number of subsets and distributing these to a number of agents depending on the data network size and core CPU availability. KDD Cup 1999 dataset is used for evaluation. The proposed hybrid modified K-means with C4.5 classification in MAS is developed in JADE platform. The results show that compared to the current methods, the MAS-IDS reduces the IDS processing time by up to 70%, while improving the detection accuracy. PMID:26161437

Hybrid Modified K-Means with C4.5 for Intrusion Detection Systems in Multiagent Systems.

PubMed

Laftah Al-Yaseen, Wathiq; Ali Othman, Zulaiha; Ahmad Nazri, Mohd Zakree

2015-01-01

Presently, the processing time and performance of intrusion detection systems are of great importance due to the increased speed of traffic data networks and a growing number of attacks on networks and computers. Several approaches have been proposed to address this issue, including hybridizing with several algorithms. However, this paper aims at proposing a hybrid of modified K-means with C4.5 intrusion detection system in a multiagent system (MAS-IDS). The MAS-IDS consists of three agents, namely, coordinator, analysis, and communication agent. The basic concept underpinning the utilized MAS is dividing the large captured network dataset into a number of subsets and distributing these to a number of agents depending on the data network size and core CPU availability. KDD Cup 1999 dataset is used for evaluation. The proposed hybrid modified K-means with C4.5 classification in MAS is developed in JADE platform. The results show that compared to the current methods, the MAS-IDS reduces the IDS processing time by up to 70%, while improving the detection accuracy.

Modifying the Weinberger-Powell Doctrine for the Modern Geo-Strategic Environment

DTIC Science & Technology

2017-03-31

Geo-Strategic Environment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Scott T. Yeatman, Lt Col, USAF 5d...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 9... environment , its prescriptive nature, and its misunderstanding of the modern utility of force. This paper examines each of these issues then proposes

Post-transcriptional modifications in the small subunit ribosomal RNA from Thermotoga maritima, including presence of a novel modified cytidine

PubMed Central

Guymon, Rebecca; Pomerantz, Steven C.; Ison, J. Nicholas; Crain, Pamela F.; McCloskey, James A.

2007-01-01

Post-transcriptional modifications of RNA are nearly ubiquitous in the principal RNAs involved in translation. However, in the case of rRNA the functional roles of modification are far less established than for tRNA, and are subject to less knowledge in terms of specific nucleoside identities and their sequence locations. Post-transcriptional modifications have been studied in the SSU rRNA from Thermotoga maritima (optimal growth 80°C), one of the most deeply branched organisms in the Eubacterial phylogenetic tree. A total of 10 different modified nucleosides were found, the greatest number reported for bacterial SSU rRNA, occupying a net of ∼14 sequence sites, compared with a similar number of sites recently reported for Thermus thermophilus and 11 for Escherichia coli. The relatively large number of modifications in Thermotoga offers modest support for the notion that thermophile rRNAs are more extensively modified than those from mesophiles. Seven of the Thermotoga modified sites are identical (location and identity) to those in E. coli. An unusual derivative of cytidine was found, designated N-330 (M r 330.117), and was sequenced to position 1404 in the decoding region of the rRNA. It was unexpectedly found to be identical to an earlier reported nucleoside of unknown structure at the same location in the SSU RNA of the archaeal mesophile Haloferax volcanii. PMID:17255199

Magnetically modified bioсells in constant magnetic field

NASA Astrophysics Data System (ADS)

Abramov, E. G.; Panina, L. K.; Kolikov, V. A.; Bogomolova, E. V.; Snetov, V. N.; Cherepkova, I. A.; Kiselev, A. A.

2017-02-01

Paper addresses the inverse problem in determining the area, where the external constant magnetic field captures the biological cells modified by the magnetic nanoparticles. Zero velocity isolines, in area where the modified cells are captured by the magnetic field were determined by numerical method for two locations of the magnet. The problem was solved taking into account the gravitational field, magnetic induction, density of medium, concentration and size of cells, and size and magnetization of nanoparticles attached to the cell. Increase in the number of the nanoparticles attached to the cell and decrease in the cell' size, enlarges the area, where the modified cells are captured and concentrated by the magnet. Solution is confirmed by the visible pattern formation of the modified cells Saccharomyces cerevisiae.

Viscous dissipation effects on MHD slip flow and heat transfer in porous micro duct with LTNE assumptions using modified lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Rabhi, R.; Amami, B.; Dhahri, H.; Mhimid, A.

2017-11-01

This paper deals with heat transfer and fluid flow in a porous micro duct under local thermal non equilibrium conditions subjected to an external oriented magnetic field. The considered sample is a micro duct filled with porous media assumed to be homogenous, isotropic and saturated. The slip velocity and the temperature jump were uniformly imposed to the wall. In modeling the flow, the Brinkmann-Forchheimer extended Darcy model was incorporated into the momentum equations. In the energy equation, the local thermal non equilibrium between the two phases was adopted. A modified axisymmetric lattice Boltzmann method was used to solve the obtained governing equation system. Attention was focused on the influence of the emerging parameters such as Knudsen number, Kn, Hartmann number, Ha, Eckert number, Ec, Biot number, Bi and the magnetic field inclination γ on flow and heat transfer throughout this paper.

Two-Phase Item Selection Procedure for Flexible Content Balancing in CAT

ERIC Educational Resources Information Center

Cheng, Ying; Chang, Hua-Hua; Yi, Qing

2007-01-01

Content balancing is an important issue in the design and implementation of computerized adaptive testing (CAT). Content-balancing techniques that have been applied in fixed content balancing, where the number of items from each content area is fixed, include constrained CAT (CCAT), the modified multinomial model (MMM), modified constrained CAT…

Modified signed-digit trinary arithmetic by using optical symbolic substitution.

PubMed

Awwal, A A; Islam, M N; Karim, M A

1992-04-10

Carry-free addition and borrow-free subtraction of modified signed-digit trinary numbers with optical symbolic substitution are presented. The proposed two-step and three-step algorithms can be easily implemented by using phase-only holograms, optical content-addressable memories, a multichannel correlator, or a polarization-encoded optical shadow-casting system.

Modified signed-digit trinary arithmetic by using optical symbolic substitution

NASA Astrophysics Data System (ADS)

Awwal, A. A. S.; Islam, M. N.; Karim, M. A.

1992-04-01

Carry-free addition and borrow-free subtraction of modified signed-digit trinary numbers with optical symbolic substitution are presented. The proposed two-step and three-step algorithms can be easily implemented by using phase-only holograms, optical content-addressable memories, a multichannel correlator, or a polarization-encoded optical shadow-casting system.

Interferon Inducers against Infectious Diseases

DTIC Science & Technology

1990-07-13

22 7. Induction of IFN in Micoe by IC-(PLL- monosaccharides ............................... *23 8. ICL- CDS04...seeking to replace both PLL and CM by modifying the PLL with engrafted polysaccharides . 2. Background A number of candidates have been developed in this...expanders, or being closely related to such. These include gelatin, anionically-modified gelatin, oarboxymethyl polysaocharides, sulfated polysaccharides

Thermal and flow analysis subroutines for the SINDA-version 9 computer routine

NASA Technical Reports Server (NTRS)

Oren, J. A.; Williams, D. R.

1973-01-01

Fluid flow analysis, special thermal analysis and input/output capabilities of the MOTAR routine were incorporated into the SINDA routine. All the capabilities were added in the form of user subroutines so that they may be added to different versions of SINDA with a minimum of programmer effort. Two modifications were made to the existing subroutines of SINDA/8 to incorporate the above subroutines. These were: (1) A modification to the preprocessor to permit actual values of array numbers, conductor numbers, node numbers or constant numbers supplied as array data to be converted to relative numbers. (2) Modifications to execution subroutine CNFAST to make it compatible with the radiant interchange user subroutine, RADIR. This modified version of SINDA has been designated SINDA/version 9. A detailed discussion of the methods used for the capabilities added is presented. The modifications for the SINDA subroutines are described, as well as user subroutines. All subroutines added or modified are listed.

Space Shuttle Orbiter trimmed center-of-gravity extension study. Volume 7: Effects of configuration modifications on the subsonic aerodynamic characteristics of the 1140 A/B orbbiter at high Reynolds numbers. [Langley low turbulence pressure tunnel

NASA Technical Reports Server (NTRS)

Phillips, W. P.

1981-01-01

Subsonic longitudinal andd laternal directional characteristics were obtained for several modified configurations of the 140 A/B orbiter (0.010 scale). These modifications, designed to extend longitudinal trim capability forward of the 65 percent fuselage length station, consisted of modified wing planform fillet and a canard. Tests were performed in the Langley Low Turbulence Pressure Tunnel at Reynolds numbers from about 4.2 million to 14.3 million based on the fuselage reference length.

Modified signed-digit trinary addition using synthetic wavelet filter

NASA Astrophysics Data System (ADS)

Iftekharuddin, K. M.; Razzaque, M. A.

2000-09-01

The modified signed-digit (MSD) number system has been a topic of interest as it allows for parallel carry-free addition of two numbers for digital optical computing. In this paper, harmonic wavelet joint transform (HWJT)-based correlation technique is introduced for optical implementation of MSD trinary adder implementation. The realization of the carry-propagation-free addition of MSD trinary numerals is demonstrated using synthetic HWJT correlator model. It is also shown that the proposed synthetic wavelet filter-based correlator shows high performance in logic processing. Simulation results are presented to validate the performance of the proposed technique.

Warranties and Acquisition Strategies.

DTIC Science & Technology

1986-04-01

statement must accompany the modified document: "Adapted from Air Command and Staff Research Report (number) entitled (title) by (author) -- This notice... STATEMENT A 86-1755 Apm d for public release; 4. PERFORMING ORGANIZATION REPORT NUMBER(S) 5. MONITORING ORGANIZATION REPORT NUMBER(S) ACSC/EDCC 6...34’Warranty,’ as used in this subpart, means a promise or affirmation given by a contractor to the Government regarding the nature, usefullness , or

Quantitative analysis by UV-Vis absorption spectroscopy of amino groups attached to the surface of carbon-based nanoparticles

NASA Astrophysics Data System (ADS)

Saraswati, T. E.; Astuti, A. R.; Rismana, N.

2018-03-01

Carbon-based nanoparticles must be modified due to their wide array of applications, especially when they are used as biomaterials. After modifying, quantitative analysis of the functional group is essential to evaluate a number of the available functional groups applied for further functionalization. In this study, we modified the carbon-based nanoparticles by amino group using submerged arc discharge in different liquids. The attached amino groups were then characterised and quantified by UV-Vis spectroscopy. This amino group functionalization was also confirmed by Fourier transform infrared (FTIR) spectra. The FTIR spectra of amine-modified nanoparticles show the definitive absorption peaks of N—H amine, C—H, C=O, C—N and Fe—O at 3418.97; 3000–2850 1700–1600 1400–1100 and 480-550 cm-1, respectively. The amine groups have different performance signals between the amine-modified and unmodified nanoparticles. The FTIR spectra results were correlated with the UV-Vis absorption spectroscopy method using acidic methyl orange. The UV-Vis absorption spectroscopy shows that the absorbance of methyl orange represented to amino groups number was 1.3 times higher when the pH of the solution was increased. The absorbance intensity was then used to estimate the quantity of amine groups attached.

Transpiration Driven Hydrologic Transport in vegetated shallow water environments: Implications on Diel and Seasonal Soil Biogeochemical Processes and System Management

NASA Astrophysics Data System (ADS)

Bachand, P.; Bachand, S. M.; Fleck, J.; Anderson, F.

2011-12-01

Hydrology arguably plays the most important role in biogeochemical cycling of mercury in wetlands and other shallow aquatic systems. CFSTR, PFR and non-ideal reactor models are oftentimes currently used to hydrologically assess these systems and to account for the fate, transport and cycling of constituents of concern (COC) with systems assumed to be non-leaky and with diffusion dominating soil transport. Yet a number of results in the literature imply transpiration drives soil transport: transpiration into the root zone is in the range of 50 - 75% of ET seasonally; gaseous emissions from aquatic systems show a diel pattern that tracks diel ET patterns; in long detention time aquatic systems ET is the largest sink for applied surface waters; and non-reactive tracers when applied to surface waters can find themselves in the root zone and within plants. All these findings strongly suggest transpiration driven infiltration into the root zone, is a significant hydrologic pathway for constituents and is an important transport mechanism. This paper examines the annual water budget for four shallow aquatic land uses in the Yolo Bypass, California: rice, wild rice, fallowed fields and wetlands. Results indicate that differences in hydrology between the fields, particularly the temporal nature of transpiration, play a significant role in mercury transformations and transport. During the irrigation period, fallowed fields discharged 6 cm of surface water (15% applied water), rice fields 31 - 43 cm (27 - 31% applied water), and wild rice fields 16 - 39 cm (15 - 31% applied water). Evapotranspiration rates were in the range of 120 - 130 cm/y for all land uses (i.e. rice, wild rice, fallowed fields and seasonal wetlands) except for the permanent wetland which was about 1/3 higher at about 170 cm/y. During the summer, approximately 50% of the applied surface water was drawn into the root zone to meet transpiration demands. Based upon results from our water budget and utilizing modified Peclet No. calculations, we quantified the relative importance of upward diffusion from the sediments and downward advection from transpiration as hydrologic transport mechanisms in the root zone. Transpiration driven infiltration moves water past the diffusive zone within 1 - 2 days in this system during the summer months. With the waning seasons, evapotranspiration diminishes until by winter diffusion dominates throughout the entire root zone. This model has great implications on the analyses of soil biogeochemical process in the root zone of shallow aquatic systems. Downward advection is a major transport mechanism into the root zone of shallow flooded aquatic systems and provides an important physical mechanism that drives variability in the seasonal and diel storage; release and cycling of COCs; and the creation of both a physical and chemical barrierd to upward diffusion of soil-borne COCs into the water column. Models that do not account for root zone interactions may not be able to capture diel and seasonal differences. Moreover, these interactions may lead to unanticipated environmental consequences as a result of cultural practices.

Preliminary Results of Altitude-Wind-Tunnel Investigation of X24C-4B Turbojet Engine. IV - Performance of Modified Compressor. Part 4; Performance of Modified Compressor

NASA Technical Reports Server (NTRS)

Thorman, H. Carl; Dupree, David T.

1947-01-01

The performance of the 11-stage axial-flow compressor, modified to improve the compressor-outlet velocity, in a revised X24C-4B turbojet engine is presented and compared with the performance of the compressor in the original engine. Performance data were obtained from an investigation of the revised engine in the MACA Cleveland altitude wind tunnel. Compressor performance data were obtained for engine operation with four exhaust nozzles of different outlet area at simulated altitudes from 15,OOO to 45,000 feet, simulated flight Mach numbers from 0.24 to 1.07, and engine speeds from 4000 to 12,500 rpm. The data cover a range of corrected engine speeds from 4100 to 13,500 rpm, which correspond to compressor Mach numbers from 0.30 to 1.00.

Investigation of thermo-fluid behavior of mixed convection heat transfer of different dimples-protrusions wall patterns to heat transfer enhancement

NASA Astrophysics Data System (ADS)

Sobhani, M.; Behzadmehr, A.

2018-05-01

This study is a numerical investigation of the effect of improving heat transfer namely, modified rough (dimples and protrusions) surfaces on the mixed convective heat transfer of a turbulent flow in a horizontal tube. The effects of different dimples-protrusions arrangements on the improving the thermal performance of a rough tube are investigated at various Richardson numbers. Three dimensional governing equations are discretized by the finite-volume technique. Based on the obtained results the dimples-protrusions arrangements are modified to find a suitable configuration for which heat transfer coefficient and pressure drop to be balanced. Modified dimples-protrusions arrangements that shows higher performance is presented. Its average thermal performance 18% and 11% is higher than the other arrangements. In addition, the results show that roughening a smooth tube is more effective at the higher Richardson number.

Results of investigations on a 0.004-scale 140C modified configuration space shuttle vehicle orbiter model (74-0) in the NASA/Langley Research Center hypersonic helium tunnel

NASA Technical Reports Server (NTRS)

Hawthorne, P. J.

1975-01-01

Data obtained during a wind tunnel test of a 0.004-scale 140C modified configuration SSV orbiter are documented. The test was conducted during August 1974 with 80 occupancy hours charged, and all runs were conducted at a nominal Mach number of 20 and at Reynolds numbers of 0.7, 1.0, 1.8, and 1,100,000 based on body length. The complete -140C modified model was tested with various elevon settings at angles of attack from 10 to 50 degrees at zero yaw and from angles of sideslip of -10 to +10 at 35 deg angle of attack. The purpose of this test was to obtain high hypersonic longitudinal and lateral-directional stability and control characteristics of the updated SSV configuration.

Comparison of Sleep Latency and Number of SOREMPs in the Home and Hospital With a Modified Multiple Sleep Latency Test: A Randomized Crossover Study.

PubMed

Beiske, Kornelia K; Sand, Trond; Rugland, Eyvind; Stavem, Knut

2017-05-01

Comparison of mean sleep latencies and number of sleep-onset rapid eye movement periods (SOREMPs) between modified multiple sleep latency test (MSLT) performed in the unattended home and in-hospital laboratory setting. A randomized crossover single-blinded design. Thirty-four subjects referred to MSLT for suspected hypersomnia or narcolepsy were included. Participants were randomized to perform modified MSLT in the unattended home or in the hospital first. Scores in the two settings were compared using Wilcoxon signed-rank test or exact McNemar test. Agreement between home and hospital categorized mean sleep latency and number of SOREMPs was assessed using simple kappa (κ) and proportion agreement. Agreement between home and hospital mean sleep latency was assessed using a Bland-Altman plot and an intraclass correlation coefficient. There was no difference between home and hospital assessment of mean sleep latency (P = 0.86). Two or more SOREMPs were found more frequently on modified MSLTs performed at home compared with those at the hospital (7 and 2, respectively; P = 0.025). Agreement was moderate for categorized sleep latency (κ = 0.53) and fair for categorized SOREMPs (κ = 0.39) in the 2 settings. Analysis of mean sleep latency using intraclass correlation coefficient showed a very good agreement between the two settings. Group mean sleep latency for home modified MSLTs seems to be reliable compared with that for the attended sleep-laboratory setting. Higher rate of SOREMP in the unattended home suggests that napping in a familiar environment facilitates the transition into REM sleep. Further studies are needed to assess the normal limit, sensitivity, and specificity for SOREMP at home before the clinical utility of home-based napping can be determined.

Association between chronic conditions and health-related quality of life: differences by level of urbanization in Peru.

PubMed

Taype-Rondan, Alvaro; Abbs, Elizabeth Sarah; Lazo-Porras, Maria; Checkley, William; Gilman, Robert H; Smeeth, Liam; Miranda, J Jaime; Bernabe-Ortiz, Antonio

2017-12-01

To evaluate the role of urbanization as an effect modifier for the association between specific chronic conditions and number of conditions with health-related quality of life (QOL). We analyzed cross-sectional data from the CRONICAS Cohort Study conducted in Lima (highly urbanized), Tumbes (semi-urban), as well as rural and urban sites in Puno. Exposures of interest were chronic bronchitis, depressive mood, hypertension, type 2 diabetes, and a composite variable aggregating the number of chronic conditions (the four exposures plus heart disease and stroke). QOL outcomes were assessed with EuroQol's EQ-5D visual analogue scale (EQ-VAS). We fitted linear regressions with robust variance to evaluate the associations of interest. Study site was assessed as a potential effect modifier using the likelihood-ratio (LR) test. We evaluated data on 2433 subjects: 51.3% were female, mean age was 57.2 years. Study site was found to be an effect modifier only for the association between depressive mood and EQ-VAS score (LR test p < 0.001). Compared to those without depressive mood, participants with depressive mood scored -13.7 points on the EQ-VAS in Lima, -7.9 in urban Puno, -11.0 in semi-urban Tumbes, and -2.7 in rural Puno. Study site was not found to be an effect modifier for the association between the number of chronic conditions and EQ-VAS (LR test p = 0.64). The impact of depressive mood on EQ-VAS was larger in urban than in rural sites, while site was not an effect modifier for the remaining associations.

Modified kernel-based nonlinear feature extraction.

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

Ma, J.; Perkins, S. J.; Theiler, J. P.

2002-01-01

Feature Extraction (FE) techniques are widely used in many applications to pre-process data in order to reduce the complexity of subsequent processes. A group of Kernel-based nonlinear FE ( H E ) algorithms has attracted much attention due to their high performance. However, a serious limitation that is inherent in these algorithms -- the maximal number of features extracted by them is limited by the number of classes involved -- dramatically degrades their flexibility. Here we propose a modified version of those KFE algorithms (MKFE), This algorithm is developed from a special form of scatter-matrix, whose rank is not determinedmore » by the number of classes involved, and thus breaks the inherent limitation in those KFE algorithms. Experimental results suggest that MKFE algorithm is .especially useful when the training set is small.« less

Improving yield and reliability of FIB modifications using electrical testing

NASA Astrophysics Data System (ADS)

Desplats, Romain; Benbrik, Jamel; Benteo, Bruno; Perdu, Philippe

1998-08-01

Focused Ion Beam technology has two main areas of application for ICs: modification and preparation for technological analysis. The most solicited area is modification. This involves physically modifying a circuit by cutting lines and creating new ones in order to change the electrical function of the circuit. IC planar technologies have an increasing number of metal interconnections making FIB modifications more complex and decreasing their changes of success. The yield of FIB operations on ICs reflects a downward trend that imposes a greater number of circuits to be modified in order to successfully correct a small number of them. This requires extended duration, which is not compatible with production line turn around times. To respond to this problem, two solutions can be defined: either, reducing the duration of each FIB operation or increasing the success rate of FIB modifications. Since reducing the time depends mainly on FIB operator experience, insuring a higher success rate represents a more crucial aspect as both experienced and novice operators could benefit from this improvement. In order to insure successful modifications, it is necessary to control each step of a FIB operation. To do this, we have developed a new method using in situ electrical testing which has a direct impact on the yield of FIB modifications. We will present this innovative development through a real case study of a CMOS ASIC for high-speed communications. Monitoring the electrical behavior at each step in a FIB operation makes it possible to reduce the number of circuits to be modified and consequently reduces system costs thanks to better yield control. Knowing the internal electrical behavior also gives us indications about the impact on reliability of FIB modified circuits. Finally, this approach can be applied to failure analysis and FIB operations on flip chip circuits.

78 FR 27476 - Pirelli Tire LLC, Grant of Petition for Decision of Inconsequential Noncompliance

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-10

... complete or partial tire identification number (TIN) on the inner tire sidewall as required by paragraphs... being modified or have been modified to ensure that the appropriate TIN information is contained on both... visibility of the full TIN on the outboard sidewall: Pirelli's internal policy allows dealers to sell these...

Turbulent Boundary Layer Flow over Superhydrophobic Surfaces

DTIC Science & Technology

2013-05-10

DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Turbulent Boundary Layer Flow over Superhydrophobic ...modified surfaces. This study encompassed the testing of four different surfaces: 1) Teflon SLIP, 2) Aluminum SLIP, 3) Honeycomb Superhydrophobic and 4...Polydimethylsiloxane elastomer (PDMSe) Superhydrophobic . Each of these surfaces uses specific geometrical surface features to modify the original

75 FR 17667 - Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to Reclassify the...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-07

...). Allozyme studies have demonstrated that wakasagi and delta smelt are genetically distinct and presumably..., survey methods have been modified to minimize potential impacts to delta smelt (K. Souza 2009, pers. comm.). Based on the low number of delta smelt collected in sampling surveys and the modified methods employed...

Improved biobased lubricants from chemically modified vegetable oils

USDA-ARS?s Scientific Manuscript database

Vegetable oils possess a number of desirable properties for lubricant application such as excellent boundary properties, high viscosity index, low volatility, low traction coefficient, renewability, and biodegradability. Unfortunately, they also have a number of weaknesses that make them less desira...

Generation and purification of highly-specific antibodies for detecting post-translationally modified proteins in vivo

PubMed Central

Arur, Swathi; Schedl, Tim

2014-01-01

Post-translational modifications alter protein structure, affecting activity, stability, localization and/or binding partners. Antibodies that specifically recognize post-translationally modified proteins have a number of uses including immuno-cytochemistry and immuno-precipitation of the modified protein to purify protein-protein and protein-nucleic acid complexes. However, antibodies directed at modified sites on individual proteins are often non-specific. Here we describe a protocol to purify polyclonal antibodies that specifically detect the modified protein of interest. The approach uses iterative rounds of subtraction and affinity purification, using stringent washes to remove antibodies that recognize the unmodified protein and low sequence complexity epitopes containing the modified amino acid. Dot and western blots assays are employed to assess antibody preparation specificity. The approach is designed to overcome the common occurrence that a single round of subtraction and affinity purification is not sufficient to obtain a modified protein specific antibody preparation. One full round of antibody purification and specificity testing takes 6 days of discontinuous time. PMID:24457330

Preston Probe Calibrations at High Reynolds Number

NASA Technical Reports Server (NTRS)

Smits, Alexander J.

1998-01-01

The overall goal of the research effort is to study the performance of two Preston probes designed by NASA Langley Research Center across an unprecedented range of Reynolds number (based on friction velocity and probe diameter), and perform an accurate calibration over the same Reynolds number range. Using the Superpipe facility in Princeton, two rounds of experiments were performed. In each round of experiments for each Reynolds number, the pressure gradient, static pressure from the Preston probes and the total pressure from the Preston probes were measured. In the first round, 3 Preston probes having outer diameters of 0.058 inches, 0.083 inches and 0.203 inches were tested over a large range of pipe Reynolds numbers. Two data reduction methods were employed: first, the static pressure measured on the Preston probe was used to calculate P (modified Preston probe configuration), and secondly, the static pressure measured at the reference pressure tap was used to calculate P (un-modified Preston probe configuration). For both methods, the static pressure was adjusted to correspond with the static pressure at the Preston probe tip using the pressure gradient. The measurements for Preston probes with diameters of 0.058 inches, and 0.083 inches respectively were performed in the test pipe before it was polished a second time. Therefore, the measurements at high pipe Reynolds numbers may have been affected by roughness. In the second round of experiments the 0.058 inches and 0.083 inches diameter, un-modified probes were tested after the pipe was polished and prepared to ensure that the surface was smooth. The average velocity was estimated by assuming that the connection between the centerline velocity and the average velocity was known, and by using a Pitot tube to measure the centerline velocity. A preliminary error estimate suggests that it is possible to introduce a 1% to 2% error in estimating the average velocity using this approach. The evidence on the errors attending the second data set is somewhat circumstantial, and the measurements have not been repeated using a better approach, it seems probable that the correlation given applies to un-modified Preston probes over the range 6.4 less than x* less than 11.3.

Method Accelerates Training Of Some Neural Networks

NASA Technical Reports Server (NTRS)

Shelton, Robert O.

1992-01-01

Three-layer networks trained faster provided two conditions are satisfied: numbers of neurons in layers are such that majority of work done in synaptic connections between input and hidden layers, and number of neurons in input layer at least as great as number of training pairs of input and output vectors. Based on modified version of back-propagation method.

Black hole field theory with a firewall in two spacetime dimensions

NASA Astrophysics Data System (ADS)

Ho, C. T. Marco; Su, Daiqin; Mann, Robert B.; Ralph, Timothy C.

2016-10-01

We propose that the vacuum state of a scalar field around a black hole is a modified Unruh vacuum. In (1 +1 ) dimensions, we show that a free-faller close to such an horizon can be modeled as an inertial observer in a modified Minkowski vacuum. The modification allows for information-leaking correlations at high frequencies. Using a Gaussian detector centered at k0, we find that the expectation value of the number operator for a detector crossing the horizon is proportional to 1 /|k0|, implying that the free-faller will observe unbounded numbers of high-energy photons, i.e. a firewall.

Testing modified gravity using a marked correlation function

NASA Astrophysics Data System (ADS)

Armijo, Joaquí n.; Cai, Yan-Chuan; Padilla, Nelson; Li, Baojiu; Peacock, John A.

2018-05-01

In theories of modified gravity with the chameleon screening mechanism, the strength of the fifth force depends on environment. This induces an environment dependence of structure formation, which differs from ΛCDM. We show that these differences can be captured by the marked correlation function. With the galaxy correlation functions and number densities calibrated to match between f(R) and ΛCDM models in simulations, we show that the marked correlation functions from using either the local galaxy number density or halo mass as the marks encode extra information, which can be used to test these theories. We discuss possible applications of these statistics in observations.

Dust acoustic solitary waves in a dusty plasma with two kinds of nonthermal ions at different temperatures

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

Dorranian, Davoud; Sabetkar, Akbar

The nonlinear dust acoustic solitary waves in a dusty plasma with two nonthermal ion species at different temperatures is studied analytically. Using reductive perturbation method, the Kadomtsev-Petviashivili (KP) equation is derived, and the effects of nonthermal coefficient, ions temperature, and ions number density on the amplitude and width of soliton in dusty plasma are investigated. It is shown that the amplitude of solitary wave of KP equation diverges at critical points of plasma parameters. The modified KP equation is also derived, and from there, the soliton like solutions of modified KP equation with finite amplitude is extracted. Results show thatmore » generation of rarefactive or compressive solitary waves strongly depends on the number and temperature of nonthermal ions. Results of KP equation confirm that for different magnitudes of ions temperature (mass) and number density, mostly compressive solitary waves are generated in a dusty plasma. In this case, the amplitude of solitary wave is decreased, while the width of solitary waves is increased. According to the results of modified KP equation for some certain magnitudes of parameters, there is a condition for generation of an evanescent solitary wave in a dusty plasma.« less

Stable and unstable roots of ion temperature gradient driven mode using curvature modified plasma dispersion functions

NASA Astrophysics Data System (ADS)

Gültekin, Ö.; Gürcan, Ö. D.

2018-02-01

Basic, local kinetic theory of ion temperature gradient driven (ITG) mode, with adiabatic electrons is reconsidered. Standard unstable, purely oscillating as well as damped solutions of the local dispersion relation are obtained using a bracketing technique that uses the argument principle. This method requires computing the plasma dielectric function and its derivatives, which are implemented here using modified plasma dispersion functions with curvature and their derivatives, and allows bracketing/following the zeros of the plasma dielectric function which corresponds to different roots of the ITG dispersion relation. We provide an open source implementation of the derivatives of modified plasma dispersion functions with curvature, which are used in this formulation. Studying the local ITG dispersion, we find that near the threshold of instability the unstable branch is rather asymmetric with oscillating solutions towards lower wave numbers (i.e. drift waves), and damped solutions toward higher wave numbers. This suggests a process akin to inverse cascade by coupling to the oscillating branch towards lower wave numbers may play a role in the nonlinear evolution of the ITG, near the instability threshold. Also, using the algorithm, the linear wave diffusion is estimated for the marginally stable ITG mode.

COLA with scale-dependent growth: applications to screened modified gravity models

NASA Astrophysics Data System (ADS)

Winther, Hans A.; Koyama, Kazuya; Manera, Marc; Wright, Bill S.; Zhao, Gong-Bo

2017-08-01

We present a general parallelized and easy-to-use code to perform numerical simulations of structure formation using the COLA (COmoving Lagrangian Acceleration) method for cosmological models that exhibit scale-dependent growth at the level of first and second order Lagrangian perturbation theory. For modified gravity theories we also include screening using a fast approximate method that covers all the main examples of screening mechanisms in the literature. We test the code by comparing it to full simulations of two popular modified gravity models, namely f(R) gravity and nDGP, and find good agreement in the modified gravity boost-factors relative to ΛCDM even when using a fairly small number of COLA time steps.

An ontology-based search engine for protein-protein interactions

PubMed Central

2010-01-01

Background Keyword matching or ID matching is the most common searching method in a large database of protein-protein interactions. They are purely syntactic methods, and retrieve the records in the database that contain a keyword or ID specified in a query. Such syntactic search methods often retrieve too few search results or no results despite many potential matches present in the database. Results We have developed a new method for representing protein-protein interactions and the Gene Ontology (GO) using modified Gödel numbers. This representation is hidden from users but enables a search engine using the representation to efficiently search protein-protein interactions in a biologically meaningful way. Given a query protein with optional search conditions expressed in one or more GO terms, the search engine finds all the interaction partners of the query protein by unique prime factorization of the modified Gödel numbers representing the query protein and the search conditions. Conclusion Representing the biological relations of proteins and their GO annotations by modified Gödel numbers makes a search engine efficiently find all protein-protein interactions by prime factorization of the numbers. Keyword matching or ID matching search methods often miss the interactions involving a protein that has no explicit annotations matching the search condition, but our search engine retrieves such interactions as well if they satisfy the search condition with a more specific term in the ontology. PMID:20122195

An ontology-based search engine for protein-protein interactions.

PubMed

Park, Byungkyu; Han, Kyungsook

2010-01-18

Keyword matching or ID matching is the most common searching method in a large database of protein-protein interactions. They are purely syntactic methods, and retrieve the records in the database that contain a keyword or ID specified in a query. Such syntactic search methods often retrieve too few search results or no results despite many potential matches present in the database. We have developed a new method for representing protein-protein interactions and the Gene Ontology (GO) using modified Gödel numbers. This representation is hidden from users but enables a search engine using the representation to efficiently search protein-protein interactions in a biologically meaningful way. Given a query protein with optional search conditions expressed in one or more GO terms, the search engine finds all the interaction partners of the query protein by unique prime factorization of the modified Gödel numbers representing the query protein and the search conditions. Representing the biological relations of proteins and their GO annotations by modified Gödel numbers makes a search engine efficiently find all protein-protein interactions by prime factorization of the numbers. Keyword matching or ID matching search methods often miss the interactions involving a protein that has no explicit annotations matching the search condition, but our search engine retrieves such interactions as well if they satisfy the search condition with a more specific term in the ontology.

78 FR 5712 - Airworthiness Directives; CFM International, S.A. Turbofan Engines Modified by Supplemental Type...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-28

..., and CFM56-3C turbofan engines. This AD requires removal from service of certain high-pressure turbine... high-pressure turbine (HPT) disk, part number (P/N) 880026, serial number (S/N) GLKBAA9307, GLKBAA9335...

Russian and Chinese Information Warfare: Theory and Practice

DTIC Science & Technology

2004-06-01

Integral neurolinguistic programming •Placing essential programs into the conscious or sub- conscious mind •Subconscious suggestions that modify human...Generators of special rays •Optical systems • Neurolinguistic programming •Computer psychotechnology •The mass media •Audiovisual effects •Special effects...Information Warfare: Theory and Practice 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e

Improvement of Cell Survival During Human Pluripotent Stem Cell Definitive Endoderm Differentiation

PubMed Central

Wang, Han; Luo, Xie; Yao, Li; Lehman, Donna M.

2015-01-01

Definitive endoderm (DE) is a vital precursor for internal organs such as liver and pancreas. Efficient protocol to differentiate human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs) to DE is essential for regenerative medicine and for modeling diseases; yet, poor cell survival during DE differentiation remains unsolved. In this study, our use of B27 supplement in modified differentiation protocols has led to a substantial improvement. We used an SOX17-enhanced green fluorescent protein (eGFP) reporter hESC line to compare and modify established DE differentiation protocols. Both total live cell numbers and the percentages of eGFP-positive cells were used to assess differentiation efficiency. Among tested protocols, three modified protocols with serum-free B27 supplement were developed to generate a high number of DE cells. Massive cell death was avoided during DE differentiation and the percentage of DE cells remained high. When the resulting DE cells were further differentiated toward the pancreatic lineage, the expression of pancreatic-specific markers was significantly increased. Similar high DE differentiation efficiency was observed in H1 hESCs and iPSCs through the modified protocols. In B27 components, bovine serum albumin was found to facilitate DE differentiation and cell survival. Using our modified DE differentiation protocols, satisfactory quantities of quality DE can be produced as primary material for further endoderm lineage differentiation. PMID:26132288

Wind tunnel tests of modified cross, hemisflo, and disk-gap-band parachutes with emphasis in the transonic range

NASA Technical Reports Server (NTRS)

Foughner, J. T., Jr.; Alexander, W. C.

1974-01-01

Transonic wind-tunnel studies were conducted with modified cross, hemisflo, and disk-gap-band parachute models in the wake of a cone-cylinder shape forebody. The basic cross design was modified with the addition of a circumferential constraining band at the lower edge of the canopy panels. The tests covered a Mach number range of 0.3 to 1.2 and a dynamic pressure range from 479 Newtons per square meter to 5746 Newtons per square meter. The parachute models were flexible textile-type structures and were tethered to a rigid forebody with a single flexible riser. Different size models of the modified cross and disk-gap-band canopies were tested to evaluate scale effects. Model reference diameters were 0.30, 0.61, and 1.07 meters (1.0, 2.0, and 3.5 ft) for the modified cross; and nominal diameters of 0.25 and 0.52 meter (0.83 and 1.7 ft) for the disk-gap-band; and 0.55 meter (1.8 ft) for the hemisflo. Reefing information is presented for the 0.61-meter-diameter cross and the 0.52-meter-diameter disk-gap-band. Results are presented in the form of the variation of steady-state average drag coefficient with Mach number. General stability characteristics of each parachute are discussed. Included are comments on canopy coning, spinning, and fluttering motions.

A tristate optical logic system

NASA Astrophysics Data System (ADS)

Basuray, A.; Mukhopadhyay, S.; Kumar Ghosh, Hirak; Datta, A. K.

1991-09-01

A method is described to represent data in a tristate logic system which are subsequently replaced by Modified Trinary Numbers (MTN). This system is advantagegeous in parallel processing as carry and borrow free operations in arithmatic computation is possible. The logical operations are also modified according to the three states available. A possible practical application of the same using polarized light is also suggested.

78 FR 23978 - Proposed Collection; Comment Request for Revenue Procedure 2011-14 (as modified by and amplified...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-23

... information collections, as required by the Paperwork Reduction Act of 1995, Public Law 104-13 (44 U.S.C. 3506... modified and amplified by RP 2011-22 and RP 2011-28), Changes in Methods of Accounting. DATES: Written....gov . SUPPLEMENTARY INFORMATION: Title: Changes in Methods of Accounting. OMB Number: 1545-1551...

State Perspectives on Implementing, or Choosing Not to Implement, an Alternate Assessment Based on Modified Academic Achievement Standards

ERIC Educational Resources Information Center

Palmer, Porter W.

2009-01-01

Since Federal regulations have given states the option to implement alternate assessments based on modified academic achievement standards (AA-MAS) as part of their accountability systems for a small group of students with disabilities, a number of states have made decisions about whether or not to develop and implement such an assessment.…

Interfacial characterization and supercapacitive properties of polyaniline-Gum arabic nanocomposite/graphene oxide LbL modified electrodes

NASA Astrophysics Data System (ADS)

Oliveira, Rafaela D.; Santos, Cleverson S.; Ferreira, Rodolfo T.; Marciniuk, Gustavo; Marchesi, Luís F.; Garcia, Jarem R.; Vidotti, Marcio; Pessoa, Christiana A.

2017-12-01

In this manuscript, we describe the synthesis and electrochemical characterization of polyaniline-gum arabic nanocomposites and graphene oxide (PANI-GA/GO) modified electrodes with a detailed study concerning their supercapacitive properties. The electrode modification was carried out by using the Layer-by-Layer technique (LbL), where the PANI-GA nanocomposite dispersion was used as polycation and the GO colloidal dispersion as polyanion. The bilayer growth was followed by both UV-vis spectroscopy and cyclic voltammetry, and an increase in the characteristic PANI absorption and in the electrochemical signal was verified, confirming the electrode build up. Galvanostatic charge-discharge curves (GCDC) were performed to evaluate the supercapacitive properties of the modified electrodes, these results showed the dependence of the specific capacitance with the number of bilayers, where values of CS around 15 mF cm-2 (i = 0.1 mA cm-2) were found. Electrochemical impedance spectroscopy confirmed the pseudocapacitive properties of the modified electrodes, showing an increase in the low-frequency capacitance with the number of bilayers. Hereby the (PANI-GA/GO)-LbL electrodes were shown to be good candidates for active materials in supercapacitors.

Stable Gene Targeting in Human Cells Using Single-Strand Oligonucleotides with Modified Bases

PubMed Central

Rios, Xavier; Briggs, Adrian W.; Christodoulou, Danos; Gorham, Josh M.; Seidman, Jonathan G.; Church, George M.

2012-01-01

Recent advances allow multiplexed genome engineering in E. coli, employing easily designed oligonucleotides to edit multiple loci simultaneously. A similar technology in human cells would greatly expedite functional genomics, both by enhancing our ability to test how individual variants such as single nucleotide polymorphisms (SNPs) are related to specific phenotypes, and potentially allowing simultaneous mutation of multiple loci. However, oligo-mediated targeting of human cells is currently limited by low targeting efficiencies and low survival of modified cells. Using a HeLa-based EGFP-rescue reporter system we show that use of modified base analogs can increase targeting efficiency, in part by avoiding the mismatch repair machinery. We investigate the effects of oligonucleotide toxicity and find a strong correlation between the number of phosphorothioate bonds and toxicity. Stably EGFP-corrected cells were generated at a frequency of ~0.05% with an optimized oligonucleotide design combining modified bases and reduced number of phosphorothioate bonds. We provide evidence from comparative RNA-seq analysis suggesting cellular immunity induced by the oligonucleotides might contribute to the low viability of oligo-corrected cells. Further optimization of this method should allow rapid and scalable genome engineering in human cells. PMID:22615794

Calculation of composition distribution of ultrafine ion-H2O-H2SO4 clusters using a modified binary ion nucleation theory

NASA Technical Reports Server (NTRS)

Singh, J. J.; Smith, A. S.; Chan, L. Y.; Yue, G. K.

1982-01-01

Thomson's ion nucleation theory was modified to include the effects of curvature dependence of the microscopic surface tension of field dependent, nonlinear, dielectric properties of the liquid; and of sulfuric acid hydrate formation in binary mixtures of water and sulfuric acid vapors. The modified theory leads to a broadening of the ion cluster spectrum, and shifts it towards larger numbers of H2O and H2SO4 molecules. Whether there is more shifting towards larger numbers of H2O or H2SO4 molecules depends on the relative humidity and relative acidity of the mixture. Usually, a broadening of the spectrum is accompanied by a lowering of the mean cluster intensity. For fixed values of relative humidity and relative acidity, a similar broadening pattern is observed when the temperature is lowered. These features of the modified theory illustrate that a trace of sulfuric acid can facilitate the formation of ultrafine, stable, prenucleation ion clusters as well as the growth of the prenucleation ion clusters towards the critical saddle point conditions, even with low values of relative humidity and relative acidity.

Effect of modified yam (Dioscorea esculenta) flour on some physicochemical and sensory properties of synbiotic yoghurt

NASA Astrophysics Data System (ADS)

Handayani, M. N.; Cakrawati, D.; Handayani, S.

2016-04-01

The aim of the study were to know characteristics of yam modified flour; to know the effect of modified yam flour on some physicochemical and sensory properties of synbiotic yoghurt and to determine the concentration level of modified yam flour to produce symbiotic yoghurt preferred by panelists. The reasearch was conducted using one factor complete randomized design. Modified yam flour was added to yoghurt at concentration of 2%, 4%, 6%. The effect of physical modification were investigated. Proximate analysis showed modified yam flour consist of 7.66% moisture content, 1.42% ash content, 10.16%, dietary fiber, 7.49% inulin, and 71.78% total starch content. Result obtained that modified yam flour has yield of 10.54%, the modified yam flour showed solubility and water absopsion of 77,63% and 136,65 respectively. The addition of modified yam flour on yoghurt resulted significantly difference effect on texture, but did not have significantly difference on colour, flavour and aroma. Modified yam flour added yoghurt thickness because it was gelatinized when added to yoghurt at 40°C. Sensory analysis conducted with hedonic test showed synbiotic yoghurt added with 2% of modified yam flour most preferred by panellists. Synbiotic yoghurt with 2% of modified yam flour has pH number of 4, 8 and total acid tirated of 1, 7%.

PIPI: PTM-Invariant Peptide Identification Using Coding Method.

PubMed

Yu, Fengchao; Li, Ning; Yu, Weichuan

2016-12-02

In computational proteomics, the identification of peptides with an unlimited number of post-translational modification (PTM) types is a challenging task. The computational cost associated with database search increases exponentially with respect to the number of modified amino acids and linearly with respect to the number of potential PTM types at each amino acid. The problem becomes intractable very quickly if we want to enumerate all possible PTM patterns. To address this issue, one group of methods named restricted tools (including Mascot, Comet, and MS-GF+) only allow a small number of PTM types in database search process. Alternatively, the other group of methods named unrestricted tools (including MS-Alignment, ProteinProspector, and MODa) avoids enumerating PTM patterns with an alignment-based approach to localizing and characterizing modified amino acids. However, because of the large search space and PTM localization issue, the sensitivity of these unrestricted tools is low. This paper proposes a novel method named PIPI to achieve PTM-invariant peptide identification. PIPI belongs to the category of unrestricted tools. It first codes peptide sequences into Boolean vectors and codes experimental spectra into real-valued vectors. For each coded spectrum, it then searches the coded sequence database to find the top scored peptide sequences as candidates. After that, PIPI uses dynamic programming to localize and characterize modified amino acids in each candidate. We used simulation experiments and real data experiments to evaluate the performance in comparison with restricted tools (i.e., Mascot, Comet, and MS-GF+) and unrestricted tools (i.e., Mascot with error tolerant search, MS-Alignment, ProteinProspector, and MODa). Comparison with restricted tools shows that PIPI has a close sensitivity and running speed. Comparison with unrestricted tools shows that PIPI has the highest sensitivity except for Mascot with error tolerant search and ProteinProspector. These two tools simplify the task by only considering up to one modified amino acid in each peptide, which results in a higher sensitivity but has difficulty in dealing with multiple modified amino acids. The simulation experiments also show that PIPI has the lowest false discovery proportion, the highest PTM characterization accuracy, and the shortest running time among the unrestricted tools.

Coliform species recovered from untreated surface water and drinking water by the membrane filter, standard, and modified most-probable-number techniques.

PubMed Central

Evans, T M; LeChevallier, M W; Waarvick, C E; Seidler, R J

1981-01-01

The species of total coliform bacteria isolated from drinking water and untreated surface water by the membrane filter (MF), the standard most-probable-number (S-MPN), and modified most-probable-number (M-MPN) techniques were compared. Each coliform detection technique selected for a different profile of coliform species from both types of water samples. The MF technique indicated that Citrobacter freundii was the most common coliform species in water samples. However, the fermentation tube techniques displayed selectivity towards the isolation of Escherichia coli and Klebsiella. The M-MPN technique selected for more C. freundii and Enterobacter spp. from untreated surface water samples and for more Enterobacter and Klebsiella spp. from drinking water samples than did the S-MPN technique. The lack of agreement between the number of coliforms detected in a water sample by the S-MPN, M-MPN, and MF techniques was a result of the selection for different coliform species by the various techniques. PMID:7013706

Detection of susceptibility genes as modifiers due to subgroup differences in complex disease.

PubMed

Bergen, Sarah E; Maher, Brion S; Fanous, Ayman H; Kendler, Kenneth S

2010-08-01

Complex diseases invariably involve multiple genes and often exhibit variable symptom profiles. The extent to which disease symptoms, course, and severity differ between affected individuals may result from underlying genetic heterogeneity. Genes with modifier effects may or may not also influence disease susceptibility. In this study, we have simulated data in which a subset of cases differ by some effect size (ES) on a quantitative trait and are also enriched for a risk allele. Power to detect this 'pseudo-modifier' gene in case-only and case-control designs was explored blind to case substructure. Simulations involved 1000 iterations and calculations for 80% power at P<0.01 while varying the risk allele frequency (RAF), sample size (SS), ES, odds ratio (OR), and proportions of the case subgroups. With realistic values for the RAF (0.20), SS (3000) and ES (1), an OR of 1.7 is necessary to detect a pseudo-modifier gene. Unequal numbers of subjects in the case groups result in little decrement in power until the group enriched for the risk allele is <30% or >70% of the total case population. In practice, greater numbers of subjects and selection of a quantitative trait with a large range will provide researchers with greater power to detect a pseudo-modifier gene. However, even under ideal conditions, studies involving alleles with low frequencies or low ORs are usually underpowered for detection of a modifier or susceptibility gene. This may explain some of the inconsistent association results for many candidate gene studies of complex diseases.

Exploring the Role of Genetic Modifiers in DNA Repair and Breast Cancer

DTIC Science & Technology

2013-09-01

GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER E-Mail: 5f. WORK UNIT NUMBER 7. PERFORMING...detailed in the Statement of Work for this training grant . I have applied for and received a no-cost extension (Amendment P00001, 24-Aug-2012...Date In Year 1 of this grant I successfully constructed a yeast tel1∆ ∆ genome-wide double-deletion library that was screened for sensitivity to

A study of the limitations of linear theory methods as applied to sonic boom calculations

NASA Technical Reports Server (NTRS)

Darden, Christine M.

1990-01-01

Current sonic boom minimization theories have been reviewed to emphasize the capabilities and flexibilities of the methods. Flexibility is important because it is necessary for the designer to meet optimized area constraints while reducing the impact on vehicle aerodynamic performance. Preliminary comparisons of sonic booms predicted for two Mach 3 concepts illustrate the benefits of shaping. Finally, for very simple bodies of revolution, sonic boom predictions were made using two methods - a modified linear theory method and a nonlinear method - for signature shapes which were both farfield N-waves and midfield waves. Preliminary analysis on these simple bodies verified that current modified linear theory prediction methods become inadequate for predicting midfield signatures for Mach numbers above 3. The importance of impulse is sonic boom disturbance and the importance of three-dimensional effects which could not be simulated with the bodies of revolution will determine the validity of current modified linear theory methods in predicting midfield signatures at lower Mach numbers.

Assessing the Treatment Effects in Apraxia of Speech: Introduction and Evaluation of the Modified Diadochokinesis Test

ERIC Educational Resources Information Center

Hurkmans, Joost; Jonkers, Roel; Boonstra, Anne M.; Stewart, Roy E.; Reinders-Messelink, Heleen A.

2012-01-01

Background: The number of reliable and valid instruments to measure the effects of therapy in apraxia of speech (AoS) is limited. Aims: To evaluate the newly developed Modified Diadochokinesis Test (MDT), which is a task to assess the effects of rate and rhythm therapies for AoS in a multiple baseline across behaviours design. Methods: The…

On the validity of the modified equation approach to the stability analysis of finite-difference methods

NASA Technical Reports Server (NTRS)

Chang, Sin-Chung

1987-01-01

The validity of the modified equation stability analysis introduced by Warming and Hyett was investigated. It is shown that the procedure used in the derivation of the modified equation is flawed and generally leads to invalid results. Moreover, the interpretation of the modified equation as the exact partial differential equation solved by a finite-difference method generally cannot be justified even if spatial periodicity is assumed. For a two-level scheme, due to a series of mathematical quirks, the connection between the modified equation approach and the von Neuman method established by Warming and Hyett turns out to be correct despite its questionable original derivation. However, this connection is only partially valid for a scheme involving more than two time levels. In the von Neumann analysis, the complex error multiplication factor associated with a wave number generally has (L-1) roots for an L-level scheme. It is shown that the modified equation provides information about only one of these roots.

Using spiritually modified cognitive-behavioral therapy in substance dependence treatment: therapists' and clients' perceptions of the presumed benefits and limitations.

PubMed

Hodge, David R; Lietz, Cynthia A

2014-11-01

Cognitive-behavioral therapy (CBT) that has been modified to incorporate clients' spiritual beliefs and practices has been used to treat a variety of problems. This study examines the utility of this modality with the treatment of alcohol dependence and other forms of substance abuse. Toward this end, six focus groups (three therapist groups and three client groups) were conducted to identify the presumed benefits and limitations of using spiritually modified CBT in substance dependence treatment. In terms of benefits, spiritually modified CBT was perceived to enhance outcomes through operationalizing horizontal and vertical sources of social support, divine coping resources, and spiritual motivation. Potential challenges include the risk of therapists inadvertently imposing their own beliefs during the modification process and the possibility of offending clients when conflicts in belief systems emerge, particularly in group setting. The article concludes by providing suggestions for incorporating spiritually modified CBT into treatment and develops a number of illustrative examples of spiritually modified CBT self-statements.

Novel materials to enhance corneal epithelial cell migration on keratoprosthesis.

PubMed

Karkhaneh, Akbar; Mirzadeh, Hamid; Ghaffariyeh, Alireza; Ebrahimi, Abdolali; Honarpisheh, Nazafarin; Hosseinzadeh, Masud; Heidari, Mohammad Hossein

2011-03-01

To introduce a new modification for silicone optical core Keratoprosthesis. Using mixtures of 2-hydroxyethyl methacrylate and acrylic acid polydimethylsiloxane (PDMS) films were modified with two-step oxygen plasma treatment, and then type I collagen was immobilised onto this modified surfaces. Both the biocompatibility of the modified films and cell behaviour on the surface of these films were investigated by in vitro tests, and formation of epithelial cell layer was evaluated by implantation of the modified films in the corneas of 10 rabbits. In vitro studies indicated that the number of attached and proliferated cells onto modified PDMS in comparison with the unmodified PDMS significantly increased. Histological studies showed that corneal epithelial cells migrated on the anterior surface of the modified films after 1week. The corneal epithelial cell formed an incomplete monolayer cellular sheet after 10days. A complete epithelialisation on the modified surface was formed after 21days. The epithelial layer persisted on the anterior surface of implant after 1-month and 3-month follow-up. This method may have potential use in silicone optical core Keratoprosthesis.

Flight determined lift and drag characteristics of an F-8 airplane modified with a supercritical wing with comparison to wind-tunnel results

NASA Technical Reports Server (NTRS)

Pyle, J. S.; Steers, L. L.

1975-01-01

Flight measurements obtained with a TF-8A airplane modified with a supercritical wing are presented for altitudes from 7.6 kilometers (25,000 feet) to 13.7 kilometers (45,000 feet), Mach numbers from 0.6 to 1.2, and Reynolds numbers from 0.8 x 10 to the 7th power to 2.3 x 10 to the 7th power. Flight results for the airplane with and without area-rule fuselage fairings are compared. The techniques used to determine the lift and drag characteristics of the airplane are discussed. Flight data are compared with wind-tunnel model results, where applicable.

Long-term hydrological simulation based on the Soil Conservation Service curve number

NASA Astrophysics Data System (ADS)

Mishra, Surendra Kumar; Singh, Vijay P.

2004-05-01

Presenting a critical review of daily flow simulation models based on the Soil Conservation Service curve number (SCS-CN), this paper introduces a more versatile model based on the modified SCS-CN method, which specializes into seven cases. The proposed model was applied to the Hemavati watershed (area = 600 km2) in India and was found to yield satisfactory results in both calibration and validation. The model conserved monthly and annual runoff volumes satisfactorily. A sensitivity analysis of the model parameters was performed, including the effect of variation in storm duration. Finally, to investigate the model components, all seven variants of the modified version were tested for their suitability.

Clustering approaches to feature change detection

NASA Astrophysics Data System (ADS)

G-Michael, Tesfaye; Gunzburger, Max; Peterson, Janet

2018-05-01

The automated detection of changes occurring between multi-temporal images is of significant importance in a wide range of medical, environmental, safety, as well as many other settings. The usage of k-means clustering is explored as a means for detecting objects added to a scene. The silhouette score for the clustering is used to define the optimal number of clusters that should be used. For simple images having a limited number of colors, new objects can be detected by examining the change between the optimal number of clusters for the original and modified images. For more complex images, new objects may need to be identified by examining the relative areas covered by corresponding clusters in the original and modified images. Which method is preferable depends on the composition and range of colors present in the images. In addition to describing the clustering and change detection methodology of our proposed approach, we provide some simple illustrations of its application.

Huntington's Disease: Relationship Between Phenotype and Genotype.

PubMed

Sun, Yi-Min; Zhang, Yan-Bin; Wu, Zhi-Ying

2017-01-01

Huntington's disease (HD) is an autosomal dominant inherited neurodegenerative disease with the typical manifestations of involuntary movements, psychiatric and behavior disorders, and cognitive impairment. It is caused by the dynamic mutation in CAG triplet repeat number in exon 1 of huntingtin (HTT) gene. The symptoms of HD especially the age at onset are related to the genetic characteristics, both the CAG triplet repeat and the modified factors. Here, we reviewed the recent advancement on the genotype-phenotype relationship of HD, mainly focus on the characteristics of different expanded CAG repeat number, genetic modifiers, and CCG repeat number in the 3' end of CAG triplet repeat and their effects on the phenotype. We also reviewed the special forms of HD (juvenile HD, atypical onset HD, and homozygous HD) and their phenotype-genotype correlations. The review will aid clinicians to predict the onset age and disease course of HD, give the genetic counseling, and accelerate research into the HD mechanism.

Effects of Inlet Modification and Rocket-Rack Extension on the Longitudinal Trim and Low-Lift Drag of the Douglas F5D-1 Airplane as Obtained with a 0.125-Scale Rocket-Boosted Model Between Mach Numbers of 0.81 and 1.64: TED No. NACA AD 399

NASA Technical Reports Server (NTRS)

Hastings, Earl C., Jr.; Dickens, Waldo L.

1957-01-01

A flight investigation was conducted to determine the effects of inlet modification and rocket-rack extension on the longitudinal trim and low-lift drag of the Douglas F5D-1 airplane. The investigation was conducted with a 0.125-scale rocket-boosted model between Mach Numbers of 0.81 and 1.64. This paper presents the changes in trim angle of attack, trim lift coefficient, and low-lift drag caused by the modified inlets alone over a small part of the test Mach number range and by a combination of the modified inlets and extended rocket racks throughout the remainder of the test.

A web-based repository of surgical simulator projects.

PubMed

Leskovský, Peter; Harders, Matthias; Székely, Gábor

2006-01-01

The use of computer-based surgical simulators for training of prospective surgeons has been a topic of research for more than a decade. As a result, a large number of academic projects have been carried out, and a growing number of commercial products are available on the market. Keeping track of all these endeavors for established groups as well as for newly started projects can be quite arduous. Gathering information on existing methods, already traveled research paths, and problems encountered is a time consuming task. To alleviate this situation, we have established a modifiable online repository of existing projects. It contains detailed information about a large number of simulator projects gathered from web pages, papers and personal communication. The database is modifiable (with password protected sections) and also allows for a simple statistical analysis of the collected data. For further information, the surgical repository web page can be found at www.virtualsurgery.vision.ee.ethz.ch.

Resonance Ops: How Developing Social Movements Can Operationalize Ideologies

DTIC Science & Technology

2016-12-01

NUMBERS 6. AUTHOR(S) Gabriel R. Bowns 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 8...PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING /MONITORING AGENCY NAME(S) AND ADDRESS(ES) N/A 10. SPONSORING / MONITORING AGENCY REPORT NUMBER...international phenomena, my recommendation is an initial attempt to modify Special Operations organization and expectations and to improve their effectiveness

Novel alpha-hydroxy phosphonic acids via castor oil

USDA-ARS?s Scientific Manuscript database

Hydroxy fatty acids (HFAs) have found a number of uses in today’s market, with uses ranging from materials to pharmaceuticals. Castor oil has served as a versatile HFA; its principle component, ricinoleic acid, can be isolated from castor oil and has been modified extensively for a number of applica...

Effect of Diabetes and Obesity on Disparities in Prostate Cancer Outcomes

DTIC Science & Technology

2015-10-01

AWARD NUMBER: W81XWH-14-1-0503 TITLE: “Effect of Diabetes and Obesity on Disparities in Prostate Cancer Outcomes PRINCIPAL INVESTIGATOR: Bettina F...and Obesity on Disparities in Prostate Cancer Outcomes 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-14-1-0503 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR...death by identifying potential modifiable factors. 15. SUBJECT TERMS Prostate cancer, disparities, VHA and VACCR data, obesity , mortality, survival

Electroosmotic Push–Pull Perfusion: Description and Application to Qualitative Analysis of the Hydrolysis of Exogenous Galanin in Organotypic Hippocampal Slice Cultures

PubMed Central

2013-01-01

We demonstrate here a method that perfuses a small region of an organotypic hippocampal culture with a solution containing an enzyme substrate, a neuropeptide. Perfusate containing hydrolysis products is continually collected and subsequently analyzed for the products of the enzymatic degradation of the peptide substrate. The driving force for perfusion is an electric field. The fused silica capillaries used as “push” and “pull” or “source” and “collection” capillaries have a ζ-potential that is negative and greater in magnitude than the tissue’s ζ-potential. Thus, depending on the magnitudes of particular dimensions, the electroosmotic flow in the capillaries augments the fluid velocity in the tissue. The flow rate is not directly measured; however, we determine it using a finite-element approach. We have determined the collection efficiency of the system using an all d-amino acid internal standard. The flow rates are low, in the nL/min range, and adjustable by controlling the current or voltage in the system. The collection efficiency of the d-amino acid peptide internal standard is variable, increasing with increased current and thus electroosmotic flow rate. The collection efficiency can be rationalized in the context of a Peclet number. Electroosmotic push–pull perfusion of the neuropeptide galanin (gal1–29) through the extracellular space of an organotypic hippocampal culture results in its hydrolysis by ectopeptidase reactions occurring in the extracellular space. The products of hydrolysis were identified by MALDI-MS. Experiments at two levels of current (8–12 μA and 19–40 μA) show that the probability of seeing hydrolysis products (apparently from aminopeptidases) is greater in the Cornu Ammonis area 3 (CA3) than in the Cornu Ammonis area 1 (CA1) in the higher current experiments. In the lower current experiments, shorter peptide products of aminopeptidases (gal13–29 to gal20–19) are seen with greater frequency in CA3 than in CA1 but there is no statistically significant difference for longer peptides (gal3–29 to gal12–29). PMID:23614879

Suite of Benchmark Tests to Conduct Mesh-Convergence Analysis of Nonlinear and Non-constant Coefficient Transport Codes

NASA Astrophysics Data System (ADS)

Zamani, K.; Bombardelli, F. A.

2014-12-01

Verification of geophysics codes is imperative to avoid serious academic as well as practical consequences. In case that access to any given source code is not possible, the Method of Manufactured Solution (MMS) cannot be employed in code verification. In contrast, employing the Method of Exact Solution (MES) has several practical advantages. In this research, we first provide four new one-dimensional analytical solutions designed for code verification; these solutions are able to uncover the particular imperfections of the Advection-diffusion-reaction equation, such as nonlinear advection, diffusion or source terms, as well as non-constant coefficient equations. After that, we provide a solution of Burgers' equation in a novel setup. Proposed solutions satisfy the continuity of mass for the ambient flow, which is a crucial factor for coupled hydrodynamics-transport solvers. Then, we use the derived analytical solutions for code verification. To clarify gray-literature issues in the verification of transport codes, we designed a comprehensive test suite to uncover any imperfection in transport solvers via a hierarchical increase in the level of tests' complexity. The test suite includes hundreds of unit tests and system tests to check vis-a-vis the portions of the code. Examples for checking the suite start by testing a simple case of unidirectional advection; then, bidirectional advection and tidal flow and build up to nonlinear cases. We design tests to check nonlinearity in velocity, dispersivity and reactions. The concealing effect of scales (Peclet and Damkohler numbers) on the mesh-convergence study and appropriate remedies are also discussed. For the cases in which the appropriate benchmarks for mesh convergence study are not available, we utilize symmetry. Auxiliary subroutines for automation of the test suite and report generation are designed. All in all, the test package is not only a robust tool for code verification but it also provides comprehensive insight on the ADR solvers capabilities. Such information is essential for any rigorous computational modeling of ADR equation for surface/subsurface pollution transport. We also convey our experiences in finding several errors which were not detectable with routine verification techniques.

Electrochemical Ionization and Analyte Charging in the Array of Micromachined UltraSonic Electrospray (AMUSE) Ion Source

PubMed Central

Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

2010-01-01

Electrochemistry and ion transport in a planar array of mechanically-driven, droplet-based ion sources are investigated using an approximate time scale analysis and in-depth computational simulations. The ion source is modeled as a controlled-current electrolytic cell, in which the piezoelectric transducer electrode, which mechanically drives the charged droplet generation using ultrasonic atomization, also acts as the oxidizing/corroding anode (positive mode). The interplay between advective and diffusive ion transport of electrochemically generated ions is analyzed as a function of the transducer duty cycle and electrode location. A time scale analysis of the relative importance of advective vs. diffusive ion transport provides valuable insight into optimality, from the ionization prospective, of alternative design and operation modes of the ion source operation. A computational model based on the solution of time-averaged, quasi-steady advection-diffusion equations for electroactive species transport is used to substantiate the conclusions of the time scale analysis. The results show that electrochemical ion generation at the piezoelectric transducer electrodes located at the back-side of the ion source reservoir results in poor ionization efficiency due to insufficient time for the charged analyte to diffuse away from the electrode surface to the ejection location, especially at near 100% duty cycle operation. Reducing the duty cycle of droplet/analyte ejection increases the analyte residence time and, in turn, improves ionization efficiency, but at an expense of the reduced device throughput. For applications where this is undesirable, i.e., multiplexed and disposable device configurations, an alternative electrode location is incorporated. By moving the charging electrode to the nozzle surface, the diffusion length scale is greatly reduced, drastically improving ionization efficiency. The ionization efficiency of all operating conditions considered is expressed as a function of the dimensionless Peclet number, which defines the relative effect of advection as compared to diffusion. This analysis is general enough to elucidate an important role of electrochemistry in ionization efficiency of any arrayed ion sources, be they mechanically-driven or electrosprays, and is vital for determining optimal design and operation conditions. PMID:20607111

Universal Linear Scaling of Permeability and Time for Heterogeneous Fracture Dissolution

NASA Astrophysics Data System (ADS)

Wang, L.; Cardenas, M. B.

2017-12-01

Fractures are dynamically changing over geological time scale due to mechanical deformation and chemical reactions. However, the latter mechanism remains poorly understood with respect to the expanding fracture, which leads to a positively coupled flow and reactive transport processes, i.e., as a fracture expands, so does its permeability (k) and thus flow and reactive transport processes. To unravel this coupling, we consider a self-enhancing process that leads to fracture expansion caused by acidic fluid, i.e., CO2-saturated brine dissolving calcite fracture. We rigorously derive a theory, for the first time, showing that fracture permeability increases linearly with time [Wang and Cardenas, 2017]. To validate this theory, we resort to the direct simulation that solves the Navier-Stokes and Advection-Diffusion equations with a moving mesh according to the dynamic dissolution process in two-dimensional (2D) fractures. We find that k slowly increases first until the dissolution front breakthrough the outbound when we observe a rapid k increase, i.e., the linear time-dependence of k occurs. The theory agrees well with numerical observations across a broad range of Peclet and Damkohler numbers through homogeneous and heterogeneous 2D fractures. Moreover, the theory of linear scaling relationship between k and time matches well with experimental observations of three-dimensional (3D) fractures' dissolution. To further attest to our theory's universality for 3D heterogeneous fractures across a broad range of roughness and correlation length of aperture field, we develop a depth-averaged model that simulates the process-based reactive transport. The simulation results show that, regardless of a wide variety of dissolution patterns such as the presence of dissolution fingers and preferential dissolution paths, the linear scaling relationship between k and time holds. Our theory sheds light on predicting permeability evolution in many geological settings when the self-enhancing process is relevant. References: Wang, L., and M. B. Cardenas (2017), Linear permeability evolution of expanding conduits due to feedback between flow and fast phase change, Geophys. Res. Lett., 44(9), 4116-4123, doi: 10.1002/2017gl073161.

Pore-scale dynamics of salt transport in drying porous media

NASA Astrophysics Data System (ADS)

Shokri, N.

2013-12-01

Understanding the physics of water evaporation from saline porous media is important in many hydrological processes such as land-atmosphere interactions, water management, vegetation, soil salinity, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI2 solution (5% concentration by mass) with a spatial and temporal resolution of 12 microns and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron X-rays energies immediately above (33.2690 keV) and below (33.0690 keV) the K-edge value of Iodine (33.1694 keV). Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI2 concentration at pore scale. The experiment was continued for 12 hours. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. The Peclet number (describing the competition between convection and diffusion) was greater than one in our experiment resulting in higher salt concentrations closer to the evaporation surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray micro-tomography as an effective tool to investigate the dynamics of dissolved salt transport in porous media with high spatial and temporal resolutions.

Aquarius - A Modelling Package for Groundwater Flow and Coupled Heat Transport in the Range 0.1 to 100 MPa and 0.1 to 1000 C

NASA Astrophysics Data System (ADS)

Cook, S. J.

2009-05-01

Aquarius is a Windows application that models fluid flow and heat transport under conditions in which fluid buoyancy can significantly impact patterns and magnitudes of fluid flow. The package is designed as a visualization tool through which users can examine flow systems in environments, both low temperature aquifers and regions with elevated PT regimes such as deep sedimentary basins, hydrothermal systems, and contact thermal aureoles. The package includes 4 components: (1) A finite-element mesh generator/assembler capable of representing complex geologic structures. Left-hand, right-hand and alternating linear triangles can be mixed within the mesh. Planer horizontal, planer vertical and cylindrical vertical coordinate sections are supported. (2) A menu-selectable system for setting properties and boundary/initial conditions. The design retains mathematical terminology for all input parameters such as scalars (e.g., porosity), tensors (e.g., permeability), and boundary/initial conditions (e.g., fixed potential). This makes the package an effective instructional aide by linking model requirements with the underlying mathematical concepts of partial differential equations and the solution logic of boundary/initial value problems. (3) Solution algorithms for steady-state and time-transient fluid flow/heat transport problems. For all models, the nonlinear global matrix equations are solved sequentially using over-relaxation techniques. Matrix storage design allows for large (e.g., 20000) element models to run efficiently on a typical PC. (4) A plotting system that supports contouring nodal data (e.g., head), vector plots for flux data (e.g., specific discharge), and colour gradient plots for elemental data (e.g., porosity), water properties (e.g., density), and performance measures (e.g., Peclet numbers). Display graphics can be printed or saved in standard graphic formats (e.g., jpeg). This package was developed from procedural codes in C written originally to model the hydrothermal flow system responsible for contact metamorphism of Utah's Alta Stock (Cook et al., AJS 1997). These codes were reprogrammed in Microsoft C# to take advantage of object oriented design and the capabilities of Microsoft's .NET framework. The package is available at no cost by e-mail request from the author.

Assessment of local hydraulic properties from electrical resistivity tomography monitoring of a three-dimensional synthetic tracer test experiment

NASA Astrophysics Data System (ADS)

Camporese, M.; Cassiani, G.; Deiana, R.; Salandin, P.

2011-12-01

In recent years geophysical methods have become increasingly popular for hydrological applications. Time-lapse electrical resistivity tomography (ERT) represents a potentially powerful tool for subsurface solute transport characterization since a full picture of the spatiotemporal evolution of the process can be obtained. However, the quantitative interpretation of tracer tests is difficult because of the uncertainty related to the geoelectrical inversion, the constitutive models linking geophysical and hydrological quantities, and the a priori unknown heterogeneous properties of natural formations. Here an approach based on the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) data assimilation technique is applied to assess the spatial distribution of hydraulic conductivity K by incorporating time-lapse cross-hole ERT data. Electrical data consist of three-dimensional cross-hole ERT images generated for a synthetic tracer test in a heterogeneous aquifer. Under the assumption that the solute spreads as a passive tracer, for high Peclet numbers the spatial moments of the evolving plume are dominated by the spatial distribution of the hydraulic conductivity. The assimilation of the electrical conductivity 4D images allows updating of the hydrological state as well as the spatial distribution of K. Thus, delineation of the tracer plume and estimation of the local aquifer heterogeneity can be achieved at the same time by means of this interpretation of time-lapse electrical images from tracer tests. We assess the impact on the performance of the hydrological inversion of (i) the uncertainty inherently affecting ERT inversions in terms of tracer concentration and (ii) the choice of the prior statistics of K. Our findings show that realistic ERT images can be integrated into a hydrological model even within an uncoupled inverse modeling framework. The reconstruction of the hydraulic conductivity spatial distribution is satisfactory in the portion of the domain directly covered by the passage of the tracer. Aside from the issues commonly affecting inverse models, the proposed approach is subject to the problem of the filter inbreeding and the retrieval performance is sensitive to the choice of K prior geostatistical parameters.

Constraints on Fault Permeability from Helium and Heat Flow in the Los Angeles Basin

NASA Astrophysics Data System (ADS)

Garven, G.; Boles, J. R.

2016-12-01

Faults have profound controls on fluid flow in the Earth's crust. Faults affect the diagenesis of sediments, the migration of brines and petroleum, and the dynamics of hydrothermal mineralization. In southern California, the migration of petroleum and noble gases can be used to constrain fault permeability at both the formation and crustal scale. In the Los Angeles Basin, mantle-derived helium is a significant component of casing gas from deep production wells along the Newport-Inglewood Fault zone (NIFZ). Helium isotope ratios are as high as 5.3 Ra, indicating up to 66% mantle contribution along parts of this strike-slip fault zone (Boles et al., 2015). The 3He inversely correlates with CO2, a potential magmatic-derived carrier gas, and the d13C of the CO2 in the 3He rich samples is between 0 and -10 per mil, suggesting a mantle influence. The strong mantle-helium signal along the NIFZ is surprising, considering that the fault is currently in a transpressional state of stress (rather than extensional), has no history of recent magma emplacement, and lacks high geothermal gradients. Structurally it has been modeled as being truncated by a "potentially seismically active" décollement beneath the LA basin. But the geochemical data demonstrate that the NIFZ is a deep-seated fault connected with the mantle. Assuming that the helium migration is linked to the bulk fluid transport in the crust, we have used 1-D reactive mass transport theory to calculate a maximum inter-seismic Darcy flow rate of 2.2 cm yr-1 and intrinsic permeability of 160 microdarcys (1.6 x 10 -16 m2), vertically averaged across the crust. Based on thermal Peclet numbers and numerical models for the basin, we show that fault-focused fluid flow is too slow to elevate heat flow around the NIFZ. Although heat flow data are sparse, there generally doesn't appear to be any clear pattern of anomalous heat flow with the large strike-slip faults of southern California, suggesting that neither bulk fluid flow nor frictional heating alter the conductive temperature regime.

Characterization of Viscoelastic Materials Through an Active Mixer by Direct-Ink Writing

NASA Astrophysics Data System (ADS)

Drake, Eric

The goal of this thesis is two-fold: First, to determine mixing effectiveness of an active mixer attachment to a three-dimensional (3D) printer by characterizing actively-mixed, three-dimensionally printed silicone elastomers. Second, to understand mechanical properties of a printed lattice structure with varying geometry and composition. Ober et al defines mixing effectiveness as a measureable quantity characterized by two key variables: (i) a dimensionless impeller parameter (O ) that depends on mixer geometry as well as Peclet number (Pe) and (ii) a coefficient of variation (COV) that describes the mixer effectiveness based upon image intensity. The first objective utilizes tungsten tracer particles distributed throughout a batch of Dow Corning SE1700 (two parts silicone) - ink "A". Ink "B" is made from pure SE1700. Using the in-site active mixer, both ink "A" and "B" coalesce to form a hybrid ink just before extrusion. Two samples of varying mixer speeds and composition ratios are printed and analyzed by microcomputed tomography (MicroCT). A continuous stirred tank reactor (CSTR) model is applied to better understand mixing behavior. Results are then compared with computer models to verify the hypothesis. Data suggests good mixing for the sample with higher impeller speed. A Radial Distrubtion Function (RDF) macro is used to provide further qualitative analysis of mixing efficiency. The second objective of this thesis utilized three-dimensionally printed samples of varying geometry and composition to ascertain mechanical properties. Samples were printed using SE1700 provided by Lawrence Livermore National Laboratory with a face-centered tetragonal (FCT) structure. Hardness testing is conducted using a Shore OO durometer guided by a computer-controlled, three-axis translation stage to provide precise movements. Data is collected across an 'x-y' plane of the specimen. To explain the data, a simply supported beam model is applied to a single unit cell which yields basic structural behavior per cell. Characterizing the sample as a whole requires a more rigorous approach and non-trivial complexities due to varying geometries and compositions exist. The data demonstrates a uniform change in hardness as a function of position. Additionally, the data indicates periodicities in the lattice structure.

Comparison of five cluster validity indices performance in brain [18 F]FET-PET image segmentation using k-means.

PubMed

Abualhaj, Bedor; Weng, Guoyang; Ong, Melissa; Attarwala, Ali Asgar; Molina, Flavia; Büsing, Karen; Glatting, Gerhard

2017-01-01

Dynamic [ 18 F]fluoro-ethyl-L-tyrosine positron emission tomography ([ 18 F]FET-PET) is used to identify tumor lesions for radiotherapy treatment planning, to differentiate glioma recurrence from radiation necrosis and to classify gliomas grading. To segment different regions in the brain k-means cluster analysis can be used. The main disadvantage of k-means is that the number of clusters must be pre-defined. In this study, we therefore compared different cluster validity indices for automated and reproducible determination of the optimal number of clusters based on the dynamic PET data. The k-means algorithm was applied to dynamic [ 18 F]FET-PET images of 8 patients. Akaike information criterion (AIC), WB, I, modified Dunn's and Silhouette indices were compared on their ability to determine the optimal number of clusters based on requirements for an adequate cluster validity index. To check the reproducibility of k-means, the coefficients of variation CVs of the objective function values OFVs (sum of squared Euclidean distances within each cluster) were calculated using 100 random centroid initialization replications RCI 100 for 2 to 50 clusters. k-means was performed independently on three neighboring slices containing tumor for each patient to investigate the stability of the optimal number of clusters within them. To check the independence of the validity indices on the number of voxels, cluster analysis was applied after duplication of a slice selected from each patient. CVs of index values were calculated at the optimal number of clusters using RCI 100 to investigate the reproducibility of the validity indices. To check if the indices have a single extremum, visual inspection was performed on the replication with minimum OFV from RCI 100 . The maximum CV of OFVs was 2.7 × 10 -2 from all patients. The optimal number of clusters given by modified Dunn's and Silhouette indices was 2 or 3 leading to a very poor segmentation. WB and I indices suggested in median 5, [range 4-6] and 4, [range 3-6] clusters, respectively. For WB, I, modified Dunn's and Silhouette validity indices the suggested optimal number of clusters was not affected by the number of the voxels. The maximum coefficient of variation of WB, I, modified Dunn's, and Silhouette validity indices were 3 × 10 -2 , 1, 2 × 10 -1 and 3 × 10 -3 , respectively. WB-index showed a single global maximum, whereas the other indices showed also local extrema. From the investigated cluster validity indices, the WB-index is best suited for automated determination of the optimal number of clusters for [ 18 F]FET-PET brain images for the investigated image reconstruction algorithm and the used scanner: it yields meaningful results allowing better differentiation of tissues with higher number of clusters, it is simple, reproducible and has an unique global minimum. © 2016 American Association of Physicists in Medicine.

Inexpensive automated paging system for use at remote research sites

USGS Publications Warehouse

Sargent, S.L.; Dey, W.S.; Keefer, D.A.

1998-01-01

The use of a flow-activated automatic sampler at a remote research site required personnel to periodically visit the site to collect samples and reset the automatic sampler. To reduce site visits, a cellular telephone was modified for activation by a datalogger. The purpose of this study was to demonstrate the use and benefit of the modified telephone. Both the power switch and the speed-dial button on the telephone were bypassed and wired to a relay driver. The datalogger was programmed to compare values of a monitored environmental parameter with a target value. When the target value was reached or exceeded, the datalogger pulsed a relay driver, activating power to the telephone. A separate relay activated the speed dial, dialing the number of a tone-only pager. The use of this system has saved time and reduced travel costs by reducing the number of trips to the site, without the loss of any data.The use of a flow-activated automatic sampler at a remote research site required personnel to periodically visit the site to collect samples and reset the automatic sampler. To reduce site visits, a cellular telephone was modified for activation by a datalogger. The purpose of this study was to demonstrate the use and benefit of the modified telephone. Both the power switch and the speed-dial button on the telephone were bypassed and wired to a relay driver. The datalogger was programmed to compare values of a monitored environmental parameter with a target value. When the target value was reached or exceeded, the datalogger pulsed a relay driver, activating power to the telephone. A separate relay activated the speed dial, dialing the number of a tone-only pager. The use of this system has saved time and reduced travel costs by reducing the number of trips to the site, without the loss of any data.

An evolutionary reduction principle for mutation rates at multiple Loci.

PubMed

Altenberg, Lee

2011-06-01

A model of mutation rate evolution for multiple loci under arbitrary selection is analyzed. Results are obtained using techniques from Karlin (Evolutionary Biology, vol. 14, pp. 61-204, 1982) that overcome the weak selection constraints needed for tractability in prior studies of multilocus event models.A multivariate form of the reduction principle is found: reduction results at individual loci combine topologically to produce a surface of mutation rate alterations that are neutral for a new modifier allele. New mutation rates survive if and only if they fall below this surface-a generalization of the hyperplane found by Zhivotovsky et al. (Proc. Natl. Acad. Sci. USA 91, 1079-1083, 1994) for a multilocus recombination modifier. Increases in mutation rates at some loci may evolve if compensated for by decreases at other loci. The strength of selection on the modifier scales in proportion to the number of germline cell divisions, and increases with the number of loci affected. Loci that do not make a difference to marginal fitnesses at equilibrium are not subject to the reduction principle, and under fine tuning of mutation rates would be expected to have higher mutation rates than loci in mutation-selection balance.Other results include the nonexistence of 'viability analogous, Hardy-Weinberg' modifier polymorphisms under multiplicative mutation, and the sufficiency of average transmission rates to encapsulate the effect of modifier polymorphisms on the transmission of loci under selection. A conjecture is offered regarding situations, like recombination in the presence of mutation, that exhibit departures from the reduction principle. Constraints for tractability are: tight linkage of all loci, initial fixation at the modifier locus, and mutation distributions comprising transition probabilities of reversible Markov chains.

Evaluation of the Cost-Effectiveness of Pyramidal, Modified Pyramidal and Monoscreen Traps for the Control of the Tsetse Fly, Glossina fuscipes fuscipes, in Uganda

PubMed Central

Abila, P.P.; Okello-Onen, J.; Okoth, J.O.; Matete, G.O.; Wamwiri, F.; Politzar, H.

2007-01-01

Several trap designs have been used for sampling and control of the tsetse fly, Glossina fuscipes fuscipes, Newstead (Diptera: Glossinidae) based on preferences of individual researchers and program managers with little understanding of the comparative efficiency and cost-effectiveness of trap designs. This study was carried out to evaluate the cost-effectiveness of four commonly used trap designs: monoscreen, modified pyramidal and pyramidal, relative to the standard biconical trap. The study was performed under high tsetse challenge on Buvuma Island, Lake Victoria, Uganda, using a 4 × 4 Latin square design replicated 3 times, so as to separate the trap positions and day effects from the treatment effect. A total of 12 trap positions were tested over 4 days. The monoscreen trap caught significantly higher numbers of G. f. fuscipes (P<0.05) followed by biconical, modified pyramidal and pyramidal traps. Analysis of variance showed that treatment factor was a highly significant source of variation in the data. The index of increase in trap catches relative biconical were O.60 (pyramidal), 0.68 (modified pyramidal) and 1.25 (monoscreen). The monoscreen trap was cheaper (US$ 2.61) and required less material to construct than pyramidal trap (US$ 3.48), biconical and the modified pyramidal traps (US$ 4.06 each). Based on the number of flies caught per meter of material, the monoscreen trap proved to be the most cost-effective (232 flies/m) followed by the biconical trap (185 flies/m). The modified pyramidal and the pyramidal traps caught 112 and 125 flies/m, respectively. PMID:20345292

A class of minimally modified gravity theories

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

Lin, Chunshan; Mukohyama, Shinji, E-mail: chunshan.lin@yukawa.kyoto-u.ac.jp, E-mail: shinji.mukohyama@yukawa.kyoto-u.ac.jp

We investigate the Hamiltonian structure of a class of gravitational theories whose actions are linear in the lapse function. We derive the necessary and sufficient condition for a theory in this class to have two or less local physical degrees of freedom. As an application we then find several concrete examples of modified gravity theories in which the total number of local physical degrees of freedom in the gravity sector is two.

Reexamination of the Classical View of how Drag-Reducing Polymer Solutions Modify the Mean Velocity Profile: Baseline Results

NASA Astrophysics Data System (ADS)

Farsiani, Yasaman; Baade, Jacquelyne; Elbing, Brian

2016-11-01

Recent numerical and experimental data have shown that the classical view of how drag-reducing polymer solutions modify the mean turbulent velocity profile is incorrect. The classical view is that the log-region is unmodified from the traditional law-of-the-wall for Newtonian fluids, though shifted outward. Thus the current study reexamines the modified velocity distribution and its dependence on flow and polymer properties. Based on previous work it is expected that the behavior will depend on the Reynolds number, Weissenberg number, ratio of solvent viscosity to the zero-shear viscosity, and the ratio between the coiled and fully extended polymer chain lengths. The long-term objective for this study includes a parametric study to assess the velocity profile sensitivity to each of these parameters. This study will be performed using a custom design water tunnel, which has a test section that is 1 m long with a 15.2 cm square cross section and a nominal speed range of 1 to 10 m/s. The current presentation focuses on baseline (non-polymeric) measurements of the velocity distribution using PIV, which will be used for comparison of the polymer modified results. Preliminary polymeric results will also be presented. This work was supported by NSF Grant 1604978.

Internal-Modified Dithiol DNA–Directed Au Nanoassemblies: Geometrically Controlled Self–Assembly and Quantitative Surface–Enhanced Raman Scattering Properties

PubMed Central

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-01-01

In this work, a hierarchical DNA–directed self–assembly strategy to construct structure–controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal–modified dithiol single-strand DNA (ssDNA) (Au–B–A or A–B–Au–B–A). It is found that the dithiol–ssDNA–modified Au NPs and molecule quantity of thiol–modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au–DNA self–assembly units, geometrical structures of the Au NAs can be tailored from one–dimensional (1D) to quasi–2D and 2D. Au–B–A conjugates readily give 1D and quasi–2D Au NAs while 2D Au NAs can be formed by A–B–Au–B–A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite–difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”–number–depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique. PMID:26581251

Repeatability precision of the falling number procedure under standard and modified methodologies

USDA-ARS?s Scientific Manuscript database

The falling number (FN) procedure is used worldwide to assess the integrity of the starch stored within wheat seed. As an indirect measurement of the activity level of alpha-amylase, FN relies on a dedicated viscometer that measures the amount of time needed for a metal stirring rod of precise geome...

Eco-Cities: Possible or Purely Utopian?

DTIC Science & Technology

2009-12-01

00-2009 to 00-00-2009 4. TITLE AND SUBTITLE Eco-Cities: Possible or Purely Utopian? 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...2005, Disney modified their building plans for Hong Kong Disneyland by shifting the angle of the front gate by twelve degrees in order to abide by

Lutzomyia spp. (Diptera: Psychodidae) response to olfactory attractant- and light emitting diode-modified Mosquito Magnet X (MM-X) traps.

PubMed

Mann, Rajinder S; Kaufman, Phillip E; Butler, Jerry F

2009-09-01

Mosquito Magnet-X traps were modified for use with blue, green, red, and blue-green-red light-emitting diodes and olfactory attractants to determine the response of Lutzomyia shannoni (Dyar) and Lutzomyia vexator (Coquillett) (Diptera: Psychodidae) field populations to these attractants. Red and blue-green-red-baited traps captured the highest numbers of Lu. shannoni and Lu. vexator, respectively, although, there were no significant differences between the colors. Baiting the traps with CO, attracted significantly higher numbers of Lu. shannoni but showed no effect on Lu. vexator capture. In comparison with CO, alone, Lu. shannoni preferred 1-octen-3-ol and 1-hexen-3-ol (0.05 g per trap) in combination with CO.

Volume-energy parameters for heat transfer to supercritical fluids

NASA Technical Reports Server (NTRS)

Kumakawa, A.; Niino, M.; Hendricks, R. C.; Giarratano, P. J.; Arp, V. D.

1986-01-01

Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.

Ada Compiler Validation Summary Report: Certificate Number 891201S1. 10214 U.S. Navy Ada/M, Version 2.0 (/OPTIMIZE Option) VAX 8550 and VAX 11/785 Hosts AN/UYK-44 Target

DTIC Science & Technology

1989-12-01

s -M-COM ST-1815A, Ada Joint Program Office 17.gbJftYCLSSF~ATW4 Is. SECURITY CLASSFAT04 OAS. TRUmVACAT M. LUITAf WCOF ABSTRACT Xi LLASSIFIED I CM ...Department of Defense Dist Specla Washington DC 20301 AVF Control Number: NIST89USN5556_1. 10 DATE VSR CPIEM BEFORE ON-SITE: 08-11-89 DATE VSR C34PLETED AFTER...ON-SITE: 12-04-89 DATE VSR MODIFIED PER AVO C31ME : 12-29-89 DATE VSR MODIFIED PER AVO CMtEN: 04-27-90 Ada O4PIIER VALIDATION SUM4M REPORT

Wind-tunnel test results of airfoil modifications for the EA-6B

NASA Technical Reports Server (NTRS)

Sewall, W. G.; Mcghee, R. J.; Ferris, J. C.

1987-01-01

Wind-tunnel tests have been conducted (to determine the effects on airfoil performance for several airfoil modifications) for the EA-6B Wing Improvement Program. The modifications consist of contour changes to the leading-edge slat and trailing-edge flap to provide a higher low-speed maximum lift with no high-speed cruise-drag penalty. Airfoil sections from the 28- and 76-percent span stations were selected as baseline shapes with the major testing devoted to the inboard airfoil section (28-percent span station). The airfoil modifications increased the low-speed maximum lift coefficient between 20 and 35 percent over test conditions of 3 to 14 million chord Reynolds number and 0.14 to 0.34 Mach number. At the high-speed test conditions of 0.4 to 0.80 Mach number and 10 million chord Reynolds number, the modified airfoils had either matched or had lower drag coefficients for all normal-force coefficients above 0.2 as compared to the baseline airfoil. At normal-force coefficients less than 0.2, the baseline (original) airfoil had lower drag coefficients than any of the modified airfoils.

Resistance Training Enhances Skeletal Muscle Innervation Without Modifying the Number of Satellite Cells or their Myofiber Association in Obese Older Adults

PubMed Central

Messi, María Laura; Li, Tao; Wang, Zhong-Min; Marsh, Anthony P.; Nicklas, Barbara

2016-01-01

Studies in humans and animal models provide compelling evidence for age-related skeletal muscle denervation, which may contribute to muscle fiber atrophy and loss. Skeletal muscle denervation seems relentless; however, long-term, high-intensity physical activity appears to promote muscle reinnervation. Whether 5-month resistance training (RT) enhances skeletal muscle innervation in obese older adults is unknown. This study found that neural cell-adhesion molecule, NCAM+ muscle area decreased with RT and was inversely correlated with muscle strength. NCAM1 and RUNX1 gene transcripts significantly decreased with the intervention. Type I and type II fiber grouping in the vastus lateralis did not change significantly but increases in leg press and knee extensor strength inversely correlated with type I, but not with type II, fiber grouping. RT did not modify the total number of satellite cells, their number per area, or the number associated with specific fiber subtypes or innervated/denervated fibers. Our results suggest that RT has a beneficial impact on skeletal innervation, even when started late in life by sedentary obese older adults. PMID:26447161

Effects of Inlet Modification and Rocket-Rack Extension on the Longitudinal Trim and Low-Lift Drag of the Douglas F5D-1 Airplane as Obtained with a 0.125-Scale Rocket-Boosted Model between Mach Numbers of 0.81 and 1.64, TED No. NACA AD 399

NASA Technical Reports Server (NTRS)

Hastings, Earl C., Jr.; Dickens, Waldo L.

1957-01-01

A flight investigation was conducted to determine the effects of an inlet modification and rocket-rack extension on the longitudinal trim and low-lift drag of the Douglas F5D-1 airplane. The investigation was conducted with a 0.125-scale rocket-boosted model which was flight tested at the Langley Pilotless Aircraft Research Station at Wallops Island, Va. Results indicate that the combined effects of the modified inlet and fully extended rocket racks on the trim lift coefficient and trim angle of attack were small between Mach numbers of 0.94 and 1.57. Between Mach numbers of 1.10 and 1.57 there was an average increase in drag coefficient of about o,005 for the model with modified inlet and extended rocket racks. The change in drag coefficient due to the inlet modification alone is small between Mach numbers of 1.59 and 1.64

Processing and problems in manufacturing a Ti-modified Nb/sub 3/Sn MJR billet. Volume 2

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

McDonald, W.K.; Smathers, D.; Geno, J.D.

1985-06-18

This report is submitted to complete Task II of University of California Order Number 4321405. Task I had Teledyne Wah Chang Albany (TWCA) assemble and process by the Modified Jelly Roll (MJR) method a Ti-modified Nb/sub 3/Sn superconductor billet. This billet was identified as M103 by TWCA. The billet matrix is nominally composed of copper 13.5 wt % tin bronze sheet and niobium 1.2 wt % titanium expanded metal with a volume ratio of three parts bronze to one part niobium alloy. All processing steps and problems encountered in manufacturing billet M103 are described in this report.

Miniature modified Faraday cup for micro electron beams

DOEpatents

Teruya, Alan T.; Elmer, John W.; Palmer, Todd A.; Walton, Chris C.

2008-05-27

A micro beam Faraday cup assembly includes a refractory metal layer with an odd number of thin, radially positioned traces in this refractory metal layer. Some of the radially positioned traces are located at the edge of the micro modified Faraday cup body and some of the radially positioned traces are located in the central portion of the micro modified Faraday cup body. Each set of traces is connected to a separate data acquisition channel to form multiple independent diagnostic networks. The data obtained from the two diagnostic networks are combined and inputted into a computed tomography algorithm to reconstruct the beam shape, size, and power density distribution.

Biological Response Modifiers in Rheumatoid Arthritis: Systematic Review and Meta-analysis of Safety

PubMed Central

Tank, Nitishkumar D.; Karelia, Bharti N.; Vegada, Bhavisha N.

2017-01-01

Objective: To analyze available evidence on the safety of different biological response modifiers which are used for a treatment of rheumatoid arthritis (RA). Materials and Methods: We searched systematically for randomized controlled clinical trials on treatment of RA with different biological response modifiers, followed by a systematic review with meta-analysis. Trials were searched from MEDLINE and Cochrane Library databases. The following safety parameters reported in the selected trials were analyzed: number of patients suffering any adverse event (AE), withdrawal due to AEs, serious AE (SAEs), infections, serious infections, infusion reactions, injection site reactions, malignancies, and overall mortality. Undesired effects were estimated using combined relative risks (RR) and number needed to harm (NNH). Heterogeneity was evaluated by Cochrane's Q and I2 statistics. Results: According to inclusion criteria, a total of 43 trials (20,504 patients) were included in this study. A total number of AEs were found more with abatacept (RR: 1.05, NNH: 21.93). Withdrawal due to AEs was found with all biologicals, highest with anakinra (RR: 3.48, NNH: 15.70). Patients receiving newer tumor necrosis factor-alpha inhibitors, golimumab, were more likely to develop SAEs (RR: 2.44, NNH: 12.72) and infection (RR: 1.25, NNH: 10.09), and in certolizumab, serious infections (RR: 2.95, NNH: 37.31) were found more. Infusion reaction develops more with rituximab (RR: 1.52, NNH: 8.47). Etanercept showed the highest risk to develop infusion site reaction (RR: 5.33, NNH: 4.65). Biologicals showed no difference to their control counterparts in malignancy and mortality risk. Conclusion: This meta-analysis helps to clarify some frequently encountered and unanswered safety questions of different biological response modifiers, a new class of drugs, in the clinical care of RA patients. PMID:29081616

Failure probability of three designs of zirconia crowns

PubMed Central

Ramos, G. Freitas; Monteiro, E. Barbosa Carmona; Bottino, M.A.; Zhang, Y.; de Melo, R. Marques

2015-01-01

Objectives This study utilized a 2-parameter Weibull analysis for evaluation of lifetime of fully or partially porcelain-/glaze-veneered zirconia crowns after fatigue test. Methods Sixty first molars were selected and prepared for full-coverage crowns with three different designs(n = 20): Traditional –crowns with zirconia framework covered with feldspathic porcelain; Modified– crowns partially covered with veneering porcelain; and Monolithic–full-contour zirconia crowns. All specimens were treated with a glaze layer. Specimens were subjected to mechanical cycling (100N, 3Hz) with a piston with hemispherical tip (Ø=6 mm) until the specimens failed or up to 2×106 cycles. Every 500,000 cycles intervals, the fatigue tests were interrupted, and stereomicroscopy (10 X) was used to inspect the specimens for damage. We performed Weibull analysis of interval data to calculate the number of failures in each interval. Results The types and number of failures according to the groups were: cracking (Traditional-13, Modified-6) and chipping (Traditional-4) of the feldspathic porcelain, followed by delamination (Traditional-1) at the veneer/core interface and debonding (Monollithic-2) at the cementation interface. Weibull parameters (beta, scale; and eta, shape), with a two-sided confidence interval of 95%, were: Traditional – 1.25 and 0.9 × 106cycles; Modified– 0.58 and 11.7 × 106 cycles; and Monolithic – 1.05 and 16.5 × 106 cycles. Traditional crowns showed greater susceptibility to fatigue, the Modified group presented higher propensity to early failures, and the Monolithic group showed no susceptibility to fatigue. The Modified and Monolithic groups presented the highest number of crowns with no failures after the fatigue test. Conclusions The three crown designs presented significantly different behaviors under fatigue. The Modified and the Monolithic groups presented less probability to failure after 2×106cycles. PMID:26509988

Comparison of rapid descriptive sensory methodologies: Free-Choice Profiling, Flash Profile and modified Flash Profile.

PubMed

Liu, Jing; Bredie, Wender L P; Sherman, Emma; Harbertson, James F; Heymann, Hildegarde

2018-04-01

Rapid sensory methods have been developed as alternatives to traditional sensory descriptive analysis methods. Among them, Free-Choice Profiling (FCP) and Flash Profile (FP) are two that have been known for many years. The objectives of this work were to compare the rating-based FCP and ranking-based FP method; to evaluate the impact of adding adjustments to FP approach; to investigate the influence of the number of assessors on the outcome of modified FP. To achieve these aims, a conventional descriptive analysis (DA), FCP, FP and a modified version of FP were carried out. Red wines made by different grape maturity and ethanol concentration were used for sensory testing. This study showed that DA provided a more detailed and accurate information on products through a quantitative measure of the intensity of sensory attributes than FCP and FP. However, the panel hours for conducting DA were higher than that for rapid methods, and FP was even able to separate the samples to a higher degree than DA. When comparing FCP and FP, this study showed that the ranking-based FP provided a clearer separation of samples than rating-based FCP, but the latter was an easier task for most assessors. When restricting assessors on their use of attributes in FP, the sample space became clearer and the ranking task was simplified. The FP protocol with restricted attribute sets seems to be a promising approach for efficient screening of sensory properties in wine. When increasing the number of assessors from 10 to 20 for conducting the modified FP, the outcome tended to be slightly more stable, however, one should consider the degree of panel training when deciding the optimal number of assessors for conducting FP. Copyright © 2018 Elsevier Ltd. All rights reserved.

Development of an innovative immunoassay for CP4EPSPS and Cry1AB genetically modified protein detection and quantification.

PubMed

Ermolli, M; Prospero, A; Balla, B; Querci, M; Mazzeo, A; Van Den Eede, G

2006-09-01

An innovative immunoassay, called enzyme-linked immunoabsorbant assay (ELISA) Reverse, based on a new conformation of the solid phase, was developed. The solid support was expressly designed to be immersed directly in liquid samples to detect the presence of protein targets. Its application is proposed in those cases where a large number of samples have to be screened simultaneously or when the simultaneous detection of different proteins is required. As a first application, a quantitative immunoassay for Cry1AB protein in genetically modified maize was optimized. The method was tested using genetically modified organism concentrations from 0.1 to 2.0%. The limit of detection and limit of quantitation of the method were determined as 0.0056 and 0.0168 (expressed as the percentage of genetically modified organisms content), respectively. A qualitative multiplex assay to assess the presence of two genetically modified proteins simultaneously was also established for the case of the Cry1AB and the CP4EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) present in genetically modified maize and soy, respectively.

A Modified Kirchhoff plate theory for Free Vibration analysis of functionally graded material plates using meshfree method

NASA Astrophysics Data System (ADS)

Nguyen Van Do, Vuong

2018-04-01

In this paper, a modified Kirchhoff theory is presented for free vibration analyses of functionally graded material (FGM) plate based on modified radial point interpolation method (RPIM). The shear deformation effects are taken account into modified theory to ignore the locking phenomenon of thin plates. Due to the proposed refined plate theory, the number of independent unknowns reduces one variable and exists with four degrees of freedom per node. The simulated free vibration results employed by the modified RPIM are compared with the other analytical solutions to verify the effectiveness and the accuracy of the developed mesh-free method. Detail parametric studies of the proposed method are then conducted including the effectiveness of thickness ratio, boundary condition and material inhomogeneity on the sample problems of square plates. Results illustrated that the modified mesh-free RPIM can effectively predict the numerical calculation as compared to the exact solutions. The obtained numerical results are indicated that the proposed method are stable and well accurate prediction to evaluate with other published analyses.

Modified homotopy perturbation method for solving hypersingular integral equations of the first kind.

PubMed

Eshkuvatov, Z K; Zulkarnain, F S; Nik Long, N M A; Muminov, Z

2016-01-01

Modified homotopy perturbation method (HPM) was used to solve the hypersingular integral equations (HSIEs) of the first kind on the interval [-1,1] with the assumption that the kernel of the hypersingular integral is constant on the diagonal of the domain. Existence of inverse of hypersingular integral operator leads to the convergence of HPM in certain cases. Modified HPM and its norm convergence are obtained in Hilbert space. Comparisons between modified HPM, standard HPM, Bernstein polynomials approach Mandal and Bhattacharya (Appl Math Comput 190:1707-1716, 2007), Chebyshev expansion method Mahiub et al. (Int J Pure Appl Math 69(3):265-274, 2011) and reproducing kernel Chen and Zhou (Appl Math Lett 24:636-641, 2011) are made by solving five examples. Theoretical and practical examples revealed that the modified HPM dominates the standard HPM and others. Finally, it is found that the modified HPM is exact, if the solution of the problem is a product of weights and polynomial functions. For rational solution the absolute error decreases very fast by increasing the number of collocation points.

A modified NSGA-II solution for a new multi-objective hub maximal covering problem under uncertain shipments

NASA Astrophysics Data System (ADS)

Ebrahimi Zade, Amir; Sadegheih, Ahmad; Lotfi, Mohammad Mehdi

2014-07-01

Hubs are centers for collection, rearrangement, and redistribution of commodities in transportation networks. In this paper, non-linear multi-objective formulations for single and multiple allocation hub maximal covering problems as well as the linearized versions are proposed. The formulations substantially mitigate complexity of the existing models due to the fewer number of constraints and variables. Also, uncertain shipments are studied in the context of hub maximal covering problems. In many real-world applications, any link on the path from origin to destination may fail to work due to disruption. Therefore, in the proposed bi-objective model, maximizing safety of the weakest path in the network is considered as the second objective together with the traditional maximum coverage goal. Furthermore, to solve the bi-objective model, a modified version of NSGA-II with a new dynamic immigration operator is developed in which the accurate number of immigrants depends on the results of the other two common NSGA-II operators, i.e. mutation and crossover. Besides validating proposed models, computational results confirm a better performance of modified NSGA-II versus traditional one.

Efficiency of colored modified box traps for sampling of tabanids

PubMed Central

Krčmar, Stjepan; Radolić, Vanja; Lajoš, Petar; Lukačević, Igor

2014-01-01

The efficiency of ten differently colored modified box traps for collecting tabanids was studied in the Monjoroš Forest in eastern Croatia. A total of 5,436 specimens belonging to 16 species of tabanids grouped into six genera were collected. The genus Tabanus was the most represented with 98% of all collected tabanids. Tabanus bromius comprised 90% of tabanids collected, and was the most abundant species collected in all box traps. The majority of tabanids (74%) were collected from black, brown, bordeaux, red, and blue traps (dark group), whereas 26% were collected from green, light violet, white, orange, and yellow traps (light group). The black modified trap was the most successful and collected 20% of all collected tabanids, whereas the yellow trap was the least effective with 1%. The number of collected specimens of species T. bromius differed significantly between the dark and light group of traps. Traps with lower reflectance from green color collected 77% of T. bromius. The most species of tabanids (12) was collected in the brown trap, whereas the least number of species (6) was collected in the yellow trap. PMID:25514593

A modified procedure for mixture-model clustering of regional geochemical data

USGS Publications Warehouse

Ellefsen, Karl J.; Smith, David B.; Horton, John D.

2014-01-01

A modified procedure is proposed for mixture-model clustering of regional-scale geochemical data. The key modification is the robust principal component transformation of the isometric log-ratio transforms of the element concentrations. This principal component transformation and the associated dimension reduction are applied before the data are clustered. The principal advantage of this modification is that it significantly improves the stability of the clustering. The principal disadvantage is that it requires subjective selection of the number of clusters and the number of principal components. To evaluate the efficacy of this modified procedure, it is applied to soil geochemical data that comprise 959 samples from the state of Colorado (USA) for which the concentrations of 44 elements are measured. The distributions of element concentrations that are derived from the mixture model and from the field samples are similar, indicating that the mixture model is a suitable representation of the transformed geochemical data. Each cluster and the associated distributions of the element concentrations are related to specific geologic and anthropogenic features. In this way, mixture model clustering facilitates interpretation of the regional geochemical data.

Immobilization of glucoamylase on ceramic membrane surfaces modified with a new method of treatment utilizing SPCP-CVD.

PubMed

Ida; Matsuyama; Yamamoto

2000-07-01

Glucoamylase, as a model enzyme, was immobilized on a ceramic membrane modified by surface corona discharge induced plasma chemical process-chemical vapor deposition (SPCP-CVD). Characterizations of the immobilized enzyme were then discussed. Three kinds of ceramic membranes with different amounts of amino groups on the surface were prepared utilizing the SPCP-CVD method. Each with 1-time, 3-times and 5-times surface modification treatments and used for supports in glucoamylase immobilization. The amount of immobilized glucoamylase increased with the increase in the number of surface modification treatments and saturated to a certain maximum value estimated by a two-dimensional random packing. The operational stability of the immobilized glucoamylase also increased with the increase in the number of the surface treatment. It was almost the same as the conventional method, while the activity of immobilized enzyme was higher. The results indicated the possibility of designing the performance of the immobilized enzyme by controlling the amount of amino groups. The above results showed that the completely new surface modification method using SPCP was effective in modifying ceramic membranes for enzyme immobilization.

Modified methylene blue injection improves lymph node harvest in rectal cancer.

PubMed

Liu, Jianpei; Huang, Pinjie; Zheng, Zongheng; Chen, Tufeng; Wei, Hongbo

2017-04-01

The presence of nodal metastases in rectal cancer plays an important role in accurate staging and prognosis, which depends on adequate lymph node harvest. The aim of this prospective study is to investigate the feasibility and survival benefit of improving lymph node harvest by a modified method with methylene blue injection in rectal cancer specimens. One hundred and thirty-one patients with rectal cancer were randomly assigned to the control group in which lymph nodes were harvested by palpation and sight, or to the methylene blue group using a modified method of injection into the superior rectal artery with methylene blue. Analysis of clinicopathologic records, including a long-term follow-up, was performed. In the methylene blue group, 678 lymph nodes were harvested by simple palpation and sight. Methylene blue injection added 853 lymph nodes to the total harvest as well as 32 additional metastatic lymph nodes, causing a shift to node-positive stage in four patients. The average number of lymph nodes harvested was 11.7 ± 3.4 in the control group and 23.2 ± 4.7 in the methylene blue group, respectively. The harvest of small lymph nodes (<5 mm) and the average number of metastatic nodes were both significantly higher in the methylene blue group. The modified method of injection with methylene blue had no impact on overall survival. The modified method with methylene blue injection improved lymph node harvest in rectal cancer, especially small node and metastatic node retrieval, which provided more accurate staging. However, it was not associated with overall survival. © 2014 Royal Australasian College of Surgeons.

Electrocardiogram‐gated coronary CT angiography dose estimates using ImPACT

PubMed Central

Asada, Yasuki; Matsubara, Kosuke; Suzuki, Shouichi; Koshida, Kichiro; Matsunaga, Yuta; Haba, Tomonobu; Kawaguchi, Ai; Toyama, Hiroshi; Kato, Ryoichi

2016-01-01

The primary study objective was to assess radiation doses using a modified form of the Imaging Performance Assessment of Computed Tomography (CT) scanner (ImPACT) patient dosimetry for cardiac applications on an Aquilion ONE ViSION Edition scanner, including the Ca score, target computed tomography angiography (CTA), prospective CTA, continuous CTA/cardiac function analysis (CFA), and CTA/CFA modulation. Accordingly, we clarified the CT dose index (CTDI) to determine the relationship between heart rate (HR) and X‐ray exposure. As a secondary objective, we compared radiation doses using modified ImPACT, a whole‐body dosimetry phantom study, and the k‐factor method to verify the validity of the dose results obtained with modified ImPACT. The effective dose determined for the reference person (4.66 mSv at 60 beats per minute (bpm) and 33.43 mSv at 90 bpm) were approximately 10% less than those determined for the phantom study (5.28 mSv and 36.68 mSv). The effective doses according to the k‐factor (0.014 mSv·mGy−1·cm−1; 2.57 mSv and 17.10 mSv) were significantly lower than those obtained with the other two methods. In the present study, we have shown that ImPACT, when modified for cardiac applications, can assess both absorbed and effective doses. The results of our dose comparison indicate that modified ImPACT dose assessment is a promising and practical method for evaluating coronary CTA. PACS number(s): 87.57.Q‐, 87.59.Dj, 87.57.uq PMID:27455500

Association of Day Length and Weather Conditions with Physical Activity Levels in Older Community Dwelling People

PubMed Central

Witham, Miles D.; Donnan, Peter T.; Vadiveloo, Thenmalar; Sniehotta, Falko F.; Crombie, Iain K.; Feng, Zhiqiang; McMurdo, Marion E. T.

2014-01-01

Background Weather is a potentially important determinant of physical activity. Little work has been done examining the relationship between weather and physical activity, and potential modifiers of any relationship in older people. We therefore examined the relationship between weather and physical activity in a cohort of older community-dwelling people. Methods We analysed prospectively collected cross-sectional activity data from community-dwelling people aged 65 and over in the Physical Activity Cohort Scotland. We correlated seven day triaxial accelerometry data with daily weather data (temperature, day length, sunshine, snow, rain), and a series of potential effect modifiers were tested in mixed models: environmental variables (urban vs rural dwelling, percentage of green space), psychological variables (anxiety, depression, perceived behavioural control), social variables (number of close contacts) and health status measured using the SF-36 questionnaire. Results 547 participants, mean age 78.5 years, were included in this analysis. Higher minimum daily temperature and longer day length were associated with higher activity levels; these associations remained robust to adjustment for other significant associates of activity: age, perceived behavioural control, number of social contacts and physical function. Of the potential effect modifier variables, only urban vs rural dwelling and the SF-36 measure of social functioning enhanced the association between day length and activity; no variable modified the association between minimum temperature and activity. Conclusions In older community dwelling people, minimum temperature and day length were associated with objectively measured activity. There was little evidence for moderation of these associations through potentially modifiable health, environmental, social or psychological variables. PMID:24497925

Association of day length and weather conditions with physical activity levels in older community dwelling people.

PubMed

Witham, Miles D; Donnan, Peter T; Vadiveloo, Thenmalar; Sniehotta, Falko F; Crombie, Iain K; Feng, Zhiqiang; McMurdo, Marion E T

2014-01-01

Weather is a potentially important determinant of physical activity. Little work has been done examining the relationship between weather and physical activity, and potential modifiers of any relationship in older people. We therefore examined the relationship between weather and physical activity in a cohort of older community-dwelling people. We analysed prospectively collected cross-sectional activity data from community-dwelling people aged 65 and over in the Physical Activity Cohort Scotland. We correlated seven day triaxial accelerometry data with daily weather data (temperature, day length, sunshine, snow, rain), and a series of potential effect modifiers were tested in mixed models: environmental variables (urban vs rural dwelling, percentage of green space), psychological variables (anxiety, depression, perceived behavioural control), social variables (number of close contacts) and health status measured using the SF-36 questionnaire. 547 participants, mean age 78.5 years, were included in this analysis. Higher minimum daily temperature and longer day length were associated with higher activity levels; these associations remained robust to adjustment for other significant associates of activity: age, perceived behavioural control, number of social contacts and physical function. Of the potential effect modifier variables, only urban vs rural dwelling and the SF-36 measure of social functioning enhanced the association between day length and activity; no variable modified the association between minimum temperature and activity. In older community dwelling people, minimum temperature and day length were associated with objectively measured activity. There was little evidence for moderation of these associations through potentially modifiable health, environmental, social or psychological variables.

Stressful life events and cognitive decline in late life: moderation by education and age. The Cache County Study.

PubMed

Tschanz, Joann T; Pfister, Roxane; Wanzek, Joseph; Corcoran, Chris; Smith, Ken; Tschanz, Brian T; Steffens, David C; Østbye, Truls; Welsh-Bohmer, Kathleen A; Norton, Maria C

2013-08-01

Stressful life events (SLE) have been associated with increased dementia risk, but their association with cognitive decline has been inconsistent. In a longitudinal population-based study of older individuals, we examined the association between SLE and cognitive decline, and the role of potential effect modifiers. A total of 2665 non-demented participants of the Cache County Memory Study completed an SLE questionnaire at Wave 2 and were revisited 4 and 7 years later. The events were represented via several scores: total number, subjective rating (negative, positive, and unexpected), and a weighted summary based on their impact. Cognition was assessed at each visit with the modified Mini-Mental State Exam. General linear models were used to examine the association between SLE scores and cognition. Effect modification by age, education, and APOE genotype was tested. Years of formal education (p = 0.006) modified the effect of number of SLE, and age (p = 0.009) modified the effect of negative SLE on the rate of cognitive decline. Faster decline was observed among those with fewer years of education experiencing more SLE and also among younger participants experiencing more negative SLE. There was no association between other indicators of SLE and cognitive decline. APOE genotype did not modify any of the aforementioned associations. The effects of SLE on cognition in late life are complex and vary by individual factors such as age and education. These results may explain some of the contradictory findings in the literature. Copyright © 2012 John Wiley & Sons, Ltd.

Detection and traceability of genetically modified organisms in the food production chain.

PubMed

Miraglia, M; Berdal, K G; Brera, C; Corbisier, P; Holst-Jensen, A; Kok, E J; Marvin, H J P; Schimmel, H; Rentsch, J; van Rie, J P P F; Zagon, J

2004-07-01

Both labelling and traceability of genetically modified organisms are current issues that are considered in trade and regulation. Currently, labelling of genetically modified foods containing detectable transgenic material is required by EU legislation. A proposed package of legislation would extend this labelling to foods without any traces of transgenics. These new legislations would also impose labelling and a traceability system based on documentation throughout the food and feed manufacture system. The regulatory issues of risk analysis and labelling are currently harmonised by Codex Alimentarius. The implementation and maintenance of the regulations necessitates sampling protocols and analytical methodologies that allow for accurate determination of the content of genetically modified organisms within a food and feed sample. Current methodologies for the analysis of genetically modified organisms are focused on either one of two targets, the transgenic DNA inserted- or the novel protein(s) expressed- in a genetically modified product. For most DNA-based detection methods, the polymerase chain reaction is employed. Items that need consideration in the use of DNA-based detection methods include the specificity, sensitivity, matrix effects, internal reference DNA, availability of external reference materials, hemizygosity versus homozygosity, extrachromosomal DNA, and international harmonisation. For most protein-based methods, enzyme-linked immunosorbent assays with antibodies binding the novel protein are employed. Consideration should be given to the selection of the antigen bound by the antibody, accuracy, validation, and matrix effects. Currently, validation of detection methods for analysis of genetically modified organisms is taking place. In addition, new methodologies are developed, including the use of microarrays, mass spectrometry, and surface plasmon resonance. Challenges for GMO detection include the detection of transgenic material in materials with varying chromosome numbers. The existing and proposed regulatory EU requirements for traceability of genetically modified products fit within a broader tendency towards traceability of foods in general and, commercially, towards products that can be distinguished from each other. Traceability systems document the history of a product and may serve the purpose of both marketing and health protection. In this framework, segregation and identity preservation systems allow for the separation of genetically modified and non-modified products from "farm to fork". Implementation of these systems comes with specific technical requirements for each particular step of the food processing chain. In addition, the feasibility of traceability systems depends on a number of factors, including unique identifiers for each genetically modified product, detection methods, permissible levels of contamination, and financial costs. In conclusion, progress has been achieved in the field of sampling, detection, and traceability of genetically modified products, while some issues remain to be solved. For success, much will depend on the threshold level for adventitious contamination set by legislation. Copryright 2004 Elsevier Ltd.

Results of the flight noise measurement program using a standard and modified SH-3A helicopter

NASA Technical Reports Server (NTRS)

Pegg, R. J.; Henderson, H. R.; Hilton, D. A.

1973-01-01

A field noise measurement program has been conducted using both a standard SH-3A helicopter and an SH-3A helicopter modified to reduce external noise levels. Modifications included reducing rotor speed, increasing the number of rotor blades, modifying the blade-tip shapes, and acoustically treating the engine air intakes and exhaust. The purpose of this study was to document the noise characteristics recorded on the ground of each helicopter during flyby, hover, landing, and take-off operations. Based on an analysis of the measured results, the average of the overhead, overall, ontrack noise levels was approximately 4 db lower for the modified helicopter than for the standard helicopter. The improved in-flight noise characteristics, and associated small footprint areas and time durations, were judged to be mainly due to tail-rotor noise reductions. The noise reductions were obtained at the expense of required power increases at airspeeds greater than 70 knots for the modified helicopter.

An Estimate of Attributable Cases of Alzheimer Disease and Vascular Dementia due to Modifiable Risk Factors: The Impact of Primary Prevention in Europe and in Italy.

PubMed

Mayer, Flavia; Di Pucchio, Alessandra; Lacorte, Eleonora; Bacigalupo, Ilaria; Marzolini, Fabrizio; Ferrante, Gianluigi; Minardi, Valentina; Masocco, Maria; Canevelli, Marco; Di Fiandra, Teresa; Vanacore, Nicola

2018-01-01

Up to 53.7% of all cases of dementia are assumed to be due to Alzheimer disease (AD), while 15.8% are considered to be due to vascular dementia (VaD). In Europe, about 3 million cases of AD could be due to 7 potentially modifiable risk factors: diabetes, midlife hypertension and/or obesity, physical inactivity, depression, smoking, and low educational level. To estimate the number of VaD cases in Europe and the number of AD and VaD cases in Italy attributable to these 7 potentially modifiable risk factors. Assuming the nonindependence of the 7 risk factors, the adjusted combined population attributable risk (PAR) was estimated for AD and VaD. In Europe, adjusted combined PAR was 31.4% for AD and 37.8% for VaD. The total number of attributable cases was 3,033,000 for AD and 873,000 for VaD. In Italy, assuming a 20% reduction of the prevalence of each risk factor, adjusted combined PAR decreased from 45.2 to 38.9% for AD and from 53.1 to 46.6% for VaD, implying a 6.4 and 6.5% reduction in the prevalence of AD and VaD, respectively. A relevant reduction of AD and VaD cases in Europe and Italy could be obtained through primary prevention.

Optimal solution for travelling salesman problem using heuristic shortest path algorithm with imprecise arc length

NASA Astrophysics Data System (ADS)

Bakar, Sumarni Abu; Ibrahim, Milbah

2017-08-01

The shortest path problem is a popular problem in graph theory. It is about finding a path with minimum length between a specified pair of vertices. In any network the weight of each edge is usually represented in a form of crisp real number and subsequently the weight is used in the calculation of shortest path problem using deterministic algorithms. However, due to failure, uncertainty is always encountered in practice whereby the weight of edge of the network is uncertain and imprecise. In this paper, a modified algorithm which utilized heuristic shortest path method and fuzzy approach is proposed for solving a network with imprecise arc length. Here, interval number and triangular fuzzy number in representing arc length of the network are considered. The modified algorithm is then applied to a specific example of the Travelling Salesman Problem (TSP). Total shortest distance obtained from this algorithm is then compared with the total distance obtained from traditional nearest neighbour heuristic algorithm. The result shows that the modified algorithm can provide not only on the sequence of visited cities which shown to be similar with traditional approach but it also provides a good measurement of total shortest distance which is lesser as compared to the total shortest distance calculated using traditional approach. Hence, this research could contribute to the enrichment of methods used in solving TSP.

Seasonal rationalization of river water quality sampling locations: a comparative study of the modified Sanders and multivariate statistical approaches.

PubMed

Varekar, Vikas; Karmakar, Subhankar; Jha, Ramakar

2016-02-01

The design of surface water quality sampling location is a crucial decision-making process for rationalization of monitoring network. The quantity, quality, and types of available dataset (watershed characteristics and water quality data) may affect the selection of appropriate design methodology. The modified Sanders approach and multivariate statistical techniques [particularly factor analysis (FA)/principal component analysis (PCA)] are well-accepted and widely used techniques for design of sampling locations. However, their performance may vary significantly with quantity, quality, and types of available dataset. In this paper, an attempt has been made to evaluate performance of these techniques by accounting the effect of seasonal variation, under a situation of limited water quality data but extensive watershed characteristics information, as continuous and consistent river water quality data is usually difficult to obtain, whereas watershed information may be made available through application of geospatial techniques. A case study of Kali River, Western Uttar Pradesh, India, is selected for the analysis. The monitoring was carried out at 16 sampling locations. The discrete and diffuse pollution loads at different sampling sites were estimated and accounted using modified Sanders approach, whereas the monitored physical and chemical water quality parameters were utilized as inputs for FA/PCA. The designed optimum number of sampling locations for monsoon and non-monsoon seasons by modified Sanders approach are eight and seven while that for FA/PCA are eleven and nine, respectively. Less variation in the number and locations of designed sampling sites were obtained by both techniques, which shows stability of results. A geospatial analysis has also been carried out to check the significance of designed sampling location with respect to river basin characteristics and land use of the study area. Both methods are equally efficient; however, modified Sanders approach outperforms FA/PCA when limited water quality and extensive watershed information is available. The available water quality dataset is limited and FA/PCA-based approach fails to identify monitoring locations with higher variation, as these multivariate statistical approaches are data-driven. The priority/hierarchy and number of sampling sites designed by modified Sanders approach are well justified by the land use practices and observed river basin characteristics of the study area.

Suggestion for the Implementation of the Bologna Declaration in Hungary in Engineering Higher Education

ERIC Educational Resources Information Center

Molnar, Karoly; Jobbagy, Akos

2004-01-01

The countries that signed the Bologna Declaration need also to modify their engineering programmes accordingly. In Hungary some modifications are necessary independently of the Bologna Declaration. The number of students has increased by a factor of three during the past decade without an increase in the number of staff. The consequence is…

Modified dust ion-acoustic surface waves in a semi-bounded magnetized plasma containing the rotating dust grains

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

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588

2016-05-15

The dispersion relation for modified dust ion-acoustic surface waves in the magnetized dusty plasma containing the rotating dust grains is derived, and the effects of magnetic field configuration on the resonant growth rate are investigated. We present the results that the resonant growth rates of the wave would increase with the ratio of ion plasma frequency to cyclotron frequency as well as with the increase of wave number for the case of perpendicular magnetic field configuration when the ion plasma frequency is greater than the dust rotation frequency. For the parallel magnetic field configuration, we find that the instability occursmore » only for some limited ranges of the wave number and the ratio of ion plasma frequency to cyclotron frequency. The resonant growth rate is found to decrease with the increase of the wave number. The influence of dust rotational frequency on the instability is also discussed.« less

Targeted Cellular Drug Delivery using Tailored Dendritic Nanostructures

NASA Astrophysics Data System (ADS)

Kannan, Rangaramanujam; Kolhe, Parag; Kannan, Sujatha; Lieh-Lai, Mary

2002-03-01

Dendrimers and hyperbranched polymers possess highly branched architectures, with a large number of controllable, tailorble, ‘peripheral’ functionalities. Since the surface chemistry of these materials can be modified with relative ease, these materials have tremendous potential in targeted drug and gene delivery. The large number of end groups can also be tailored to create special affinity to targeted cells, and can also encapsulate drugs and deliver them in a controlled manner. We are developing tailor-modified dendritic systems for drug delivery. Synthesis, in-vitro drug loading, in-vitro drug delivery, and the targeting efficiency to the cell are being studied systematically using a wide variety of experimental tools. Polyamidoamine and Polyol dendrimers, with different generations and end-groups are studied, with drugs such as Ibuprofen and Methotrexate. Our results indicate that a large number of drug molecules can be encapsulated/attached to the dendrimers, depending on the end groups. The drug-encapsulated dendrimer is able to enter the cells rapidly and deliver the drug. Targeting strategies being explored

Creation of high-energy electron tails by means of the modified two-stream instability

NASA Technical Reports Server (NTRS)

Tanaka, M.; Papadopoulos, K.

1983-01-01

Particle simulations of the modified two-stream instability demonstrate strong electron acceleration rather than bulk heating when the relative drift speed is below a critical speed Vc. A very interesting nonlinear mode transition and autoresonance acceleration process is observed which accelerates the electrons much above the phase speed of the linearly unstable modes. Simple criteria are presented that predict the value of Vc and the number density of the accelerated electrons.

Fabrication of aligned magnetic nanoparticles using tobamoviruses.

PubMed

Kobayashi, Mime; Seki, Munetoshi; Tabata, Hitoshi; Watanabe, Yuichiro; Yamashita, Ichiro

2010-03-10

We used genetically modified tube-shaped tobamoviruses to produce 3 nm aligned magnetic nanoparticles. Amino acid residues facing the central channel of the virus were modified to increase the number of nucleation sites. Energy dispersive X-ray spectroscopy and superconducting quantum interference device analysis suggest that the particles consisted of Co-Pt alloy. The use of tobamovirus mutants is a promising approach to making a variety of components that can be applied to fabricate nanometer-scaled electronic devices.

Swedish Defence Research Abstracts 79/80-4 (Froe Foersvars Forsknings Referat 79/80-4).

DTIC Science & Technology

1980-12-05

wavelength. In order to verify and modify the model, measurements were made with a transmissometer over a horizontal measuring path . The equipment was...wavelength. In order to verify and modify the model, measurements were made with a transmissometer over a horizontal measuring path . The equipment was in... measurements taken from a number of meteoro loi ca I sensors. Aerosol .xtinc tion was obtained by subtracting the water vapour extinction , as calculated trom

Immune Protection of Nonhuman Primates Against Ebola Virus with Single Low-Dose Adenovirus Vectors Encoding Modified GPs

DTIC Science & Technology

2006-06-01

21. Geisbert TW, Hensley LE , Larsen T, Young HA, Reed DS, et al. (2003) Pathogenesis of Ebola hemorrhagic fever in cynomolgus macaques: Evidence that...Shedlock DJ, Xu L, et al. (2006) Immune protection of nonhuman primates against Ebola virus with single low-dose adenovirus vectors encoding modified...CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 9 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT

Determination of specific capacitance of modified candlenut shell based carbon as electrode material for supercapacitor

NASA Astrophysics Data System (ADS)

Zakir, M.; Budi, P.; Raya, I.; Karim, A.; Wulandari, R.; Sobrido, A. B. J.

2018-03-01

Surface modification of candlenut shell carbon (CSC) using three chemicals: nitric acid (HNO3), hydrogen peroxide (H2O2), and sulfuric acid (H2SO4) has been carried out. Activation of CSC was performed using H3PO4 solution with different ratio between CSC and activator. Carbon surface area was determined by methylene blue adsorption method. Surface characterization was performed using FTIR spectroscopy and Boehm titration method. Specific capacitance of electrode prepared from CSAC (candlenuts shell activated carbon) materials was quantified by Cyclic Voltammetry (CV) measurement. The surface area before and after activation are 105,127 m2/g, 112,488 m2/g, 124,190 m2/g, and 135,167 m2/g, respectively. Surface modification of CSAC showed the improvement in the chemical functionality of CSAC surface. Analyses using FTIR spectroscopy and Boehm titration showed that modifications with HNO3, H2SO4 and H2O2 on the surface of the CSAC increased the number of oxygen functional groups. As a consequence, the specific capacitance of CSAC modified with 65% HNO3 attained the highest value (127 μF/g). There is an incredible increase by a factor of 298% from electrode which was constructed with un-modified CSAC material. This increase correlates to the largest number of oxygen functional groups of CSAC modified with nitric acid (HNO3).

Modified independent modal space control method for active control of flexible systems

NASA Technical Reports Server (NTRS)

Baz, A.; Poh, S.

1987-01-01

A modified independent modal space control (MIMSC) method is developed for designing active vibration control systems for large flexible structures. The method accounts for the interaction between the controlled and residual modes. It incorporates also optimal placement procedures for selecting the optimal locations of the actuators in the structure in order to minimize the structural vibrations as well as the actuation energy. The MIMSC method relies on an important feature which is based on time sharing of a small number of actuators, in the modal space, to control effectively a large number of modes. Numerical examples are presented to illustrate the application of the method to generic flexible systems. The results obtained suggest the potential of the devised method in designing efficient active control systems for large flexible structures.

Comparisons of two-dimensional shock-expansion theory with experimental aerodynamic data for delta-planform wings at high supersonic speeds

NASA Technical Reports Server (NTRS)

Jernell, L. S.

1974-01-01

An investigation has been conducted to explore the potential for optimizing airfoil shape at high supersonic speeds by utilizing the two-dimensional shock-expansion method. Theoretical and experimental force and moment coefficients are compared for four delta-planform semispan wings having a leading-edge sweep angle of 65 deg and incorporating modified diamond airfoils with a thickness-chord ratio of 0.06. The wings differ only in airfoil maximum-thickness position and camber. The experimental data are obtained at Mach numbers of 3.95 and 4.63 and at a Reynolds number of 9.84 million per meter. A relatively simple method is developed for predicting, in terms of lift-drag ratio, the optimum modified diamond airfoil at high supersonic and hypersonic speeds.

Viscoinertial regime of immersed granular flows

NASA Astrophysics Data System (ADS)

Amarsid, L.; Delenne, J.-Y.; Mutabaruka, P.; Monerie, Y.; Perales, F.; Radjai, F.

2017-07-01

By means of extensive coupled molecular dynamics-lattice Boltzmann simulations, accounting for grain dynamics and subparticle resolution of the fluid phase, we analyze steady inertial granular flows sheared by a viscous fluid. We show that, for a broad range of system parameters (shear rate, confining stress, fluid viscosity, and relative fluid-grain density), the frictional strength and packing fraction can be described by a modified inertial number incorporating the fluid effect. In a dual viscous description, the effective viscosity diverges as the inverse square of the difference between the packing fraction and its jamming value, as observed in experiments. We also find that the fabric and force anisotropies extracted from the contact network are well described by the modified inertial number, thus providing clear evidence for the role of these key structural parameters in dense suspensions.

Higher modulus compositions incorporating particulate rubber

DOEpatents

Bauman, Bernard D.; Williams, Mark A.

1999-01-01

A plastic article having a number of surfaces with at least one surface being modified by contacting that surface with a reactive gas atmosphere containing F.sub.2, Cl.sub.2, O.sub.2, Ozone, SO.sub.3, oxidative acids, or mixtures thereof, at a temperature and gas partial pressure sufficient to increase the surface energy of the at least one surface being modified to at least 40 dynes/cm at a temperature of 20.degree. C., to enhance bonding of non-slip polymer coatings to the modified surface, to which coatings elastomeric or rigid particles may be admixed for imparting a surface profile and increasing the coefficient of friction between the coated surface and the counter-surface.

Profiling of modified nucleosides from ribonucleic acid digestion by supercritical fluid chromatography coupled to high resolution mass spectrometry.

PubMed

Laboureur, Laurent; Guérineau, Vincent; Auxilien, Sylvie; Yoshizawa, Satoko; Touboul, David

2018-02-16

A method based on supercritical fluid chromatography coupled to high resolution mass spectrometry for the profiling of canonical and modified nucleosides was optimized, and compared to classical reverse-phase liquid chromatography in terms of separation, number of detected modified nucleosides and sensitivity. Limits of detection and quantification were measured using statistical method and quantifications of twelve nucleosides of a tRNA digest from E. coli are in good agreement with previously reported data. Results highlight the complementarity of both separation techniques to cover the largest view of nucleoside modifications for forthcoming epigenetic studies. Copyright © 2017 Elsevier B.V. All rights reserved.

Determination of small quantities of fluoride in water: A modified zirconium-alizarin method

USGS Publications Warehouse

Lamar, W.L.; Seegmiller, C.G.

1941-01-01

The zirconium-alizarin method has been modified to facilitate the convenient and accurate determination of small amounts of fluoride in a large number of water samples. Sulfuric acid is used to acidify the samples to reduce the interference of sulfate. The pH is accurately controlled to give the most sensitive comparisons. Most natural waters can be analyzed by the modified procedure without resorting to correction curves. The fluoride content of waters containing less than 500 parts per million of sulfate, 500 parts per million of bicarbonate, and 1000 parts per million of chloride may be determined within a limit of about 0.1 part per million when a 100-ml. sample is used.

Analysis of Modified SMI Method for Adaptive Array Weight Control. M.S. Thesis

NASA Technical Reports Server (NTRS)

Dilsavor, Ronald Louis

1989-01-01

An adaptive array is used to receive a desired signal in the presence of weak interference signals which need to be suppressed. A modified sample matrix inversion (SMI) algorithm controls the array weights. The modification leads to increased interference suppression by subtracting a fraction of the noise power from the diagonal elements of the covariance matrix. The modified algorithm maximizes an intuitive power ratio criterion. The expected values and variances of the array weights, output powers, and power ratios as functions of the fraction and the number of snapshots are found and compared to computer simulation and real experimental array performance. Reduced-rank covariance approximations and errors in the estimated covariance are also described.

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

Winther, Hans A.; Koyama, Kazuya; Wright, Bill S.

We present a general parallelized and easy-to-use code to perform numerical simulations of structure formation using the COLA (COmoving Lagrangian Acceleration) method for cosmological models that exhibit scale-dependent growth at the level of first and second order Lagrangian perturbation theory. For modified gravity theories we also include screening using a fast approximate method that covers all the main examples of screening mechanisms in the literature. We test the code by comparing it to full simulations of two popular modified gravity models, namely f ( R ) gravity and nDGP, and find good agreement in the modified gravity boost-factors relative tomore » ΛCDM even when using a fairly small number of COLA time steps.« less

Impact of a labor and delivery safety bundle on a modified adverse outcomes index.

PubMed

Tolcher, Mary Catherine; Torbenson, Vanessa E; Weaver, Amy L; McGree, Michaela E; El-Nashar, Sherif A; Nesbitt, Katharine M; Gostout, Bobbie S; Famuyide, Abimbola O

2016-03-01

The Obstetrics Adverse Outcomes Index was designed to measure the quality of perinatal care and includes 10 adverse events that may occur at or around the time of delivery. We hypothesized that adverse outcomes in the labor and delivery suite, including hypoxic ischemic encephalopathy, could be decreased with a combination of interventions, even among high-risk pregnancies. The objective of the study was to evaluate the impact of a labor and delivery care bundle on adverse obstetrics outcomes as measured by a modified Obstetrics Adverse Outcomes Index, Weighted Adverse Outcomes Index, and Severity Index. This is a retrospective cohort study including all women who delivered at our academic, tertiary care institution over a 3 year period of time, before and after the implementation of an intervention to decrease adverse outcomes. Outcome measures consisted of previously reported indices that were modified including the addition of hypoxic ischemic encephalopathy. The adverse outcomes index is a percentage of deliveries with 1 or more adverse events, the weighted adverse outcomes index is the sum of the points assigned to cases with adverse outcomes divided by the number of deliveries, and the severity index is the sum of the adverse outcome scores divided by the number of deliveries with an identified adverse outcome. A segmented regression analysis was utilized to evaluate the differences in the level and trend of each index before and after our intervention using calendar month as the unit of analysis. During the study period, 5826 deliveries met inclusion criteria. Comparing the pre- and postintervention periods, high-risk pregnancy was more common in the postintervention period (73.5% vs 79.4%, P < .001). Overall, there was a decrease in both the Modified Weighted Adverse Outcomes Index (P = .0497) and the Modified Severity Index (P = 0.01) comparing the pre- and postintervention periods; there was no difference in the Modified Adverse Outcomes Index (P = .43). For low-risk pregnancies, there was no significant difference in the levels for any of the measured indices over the study period (P = .61, P = .41, and P = .34 for the Modified Adverse Outcomes Index, Modified Weighted Adverse Outcomes Index, and Modified Severity Index, respectively). Among the high-risk pregnancies, the monthly Modified Weighted Adverse Outcomes Index decreased by 4.2 ± 1.8 (P = .03). The monthly Modified Severity Index decreased by 53.9 ± 17.7 points from the pre- to the postintervention periods (P = .01) and was < 50% of the predicted Modified Severity Index had the intervention not been implemented. The cesarean delivery rate was increasing prior to the intervention, but the rate was stable after the intervention, and the absolute rate did not differ between the pre- and the postintervention periods (28.4% vs 30.0%, P = .20). Overall and for high-risk pregnancies, the implementation of the labor and delivery care bundle had a positive impact on the Modified Weighted Adverse Outcomes Index and Modified Severity Index but not the Modified Adverse Outcomes Index. Copyright © 2016 Elsevier Inc. All rights reserved.

Numerical investigation of the bowed stator effects in a transonic fan at low Reynolds number

NASA Astrophysics Data System (ADS)

Huang, Enliang; Zhao, Shengfeng; Gong, Jianbo; Lu, Xingen; Zhu, Junqiang

2017-02-01

The performance of fan stage in a small turbofan engines is significantly affected at high-altitude low Reynolds number. In order to examine the effect of low Reynolds number on the fan stage, 3D numerical simulation method was employed to analyse the performance variations and the underlying flow structure in the fan stage. For the sake of decreasing the influence of low Reynolds number, the different bowed stator airfoils were redesigned and the effect of the modified design was evaluated.

Reynolds number scaling of the influence of boundary layers on the global behavior of laboratory quasi-Keplerian flows

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

Edlund, E. M.; Ji, H.

2015-10-06

Here, we present fluid velocity measurements in a modified Taylor-Couette device operated in the quasi-Keplerian regime, where it is observed that nearly ideal flows exhibit self-similarity under scaling of the Reynolds number. In contrast, nonideal flows show progressive departure from ideal Couette as the Reynolds number is increased. We present a model that describes the observed departures from ideal Couette rotation as a function of the fluxes of angular momentum across the boundaries, capturing the dependence on Reynolds number and boundary conditions.

Reynolds number scaling of the influence of boundary layers on the global behavior of laboratory quasi-Keplerian flows.

PubMed

Edlund, E M; Ji, H

2015-10-01

We present fluid velocity measurements in a modified Taylor-Couette device operated in the quasi-Keplerian regime, where it is observed that nearly ideal flows exhibit self-similarity under scaling of the Reynolds number. In contrast, nonideal flows show progressive departure from ideal Couette as the Reynolds number is increased. We present a model that describes the observed departures from ideal Couette rotation as a function of the fluxes of angular momentum across the boundaries, capturing the dependence on Reynolds number and boundary conditions.

Effect of Diabetes and Obesity on Disparities in Prostate Cancer Outcomes

DTIC Science & Technology

2016-10-01

AWARD NUMBER: W81XWH-14-1-0503 TITLE: Effect of Diabetes and Obesity on Disparities in Prostate Cancer Outcomes PRINCIPAL INVESTIGATOR: Bettina F...Effect of Diabetes and Obesity on Disparities in Prostate Cancer Outcomes 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-14-1-0503 5c. PROGRAM ELEMENT...prostate cancer related death by identifying potential modifiable factors. 15. SUBJECT TERMS Prostate cancer, disparities, VHA and VACCR data, obesity

Modification process optimization, characterization and adsorption property of granular fir-based activated carbon

NASA Astrophysics Data System (ADS)

Chen, Congjin; Li, Xin; Tong, Zhangfa; Li, Yue; Li, Mingfei

2014-10-01

Granular fir-based activated carbon (GFAC) was modified with H2O2, and orthogonal array experimental design method was used to optimize the process. The properties of the original and modified GFAC were characterized by N2 adsorption-desorption isotherms, Brunauer-Emmett-Teller (BET) equation, Barett-Joyner-Halenda (BJH) equation, field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FT-IR) analysis, etc. When 10.00 g of GFAC with particle size of 0.25-0.85 mm was modified by 150.0 ml of aqueous H2O2 solution, the optimized conditions were found to be as follows: aqueous H2O2 solution concentration 1.0 mol·l-1, modification temperature 30.0 °C, modification time 4.0 h. Modified under the optimized conditions, decolonization of caramel, methylene blue adsorption, phenol adsorption and iodine number of the modified GFAC increased by 500.0%, 59.7%, 32.5%, and 15.1%, respectively. The original and optimally modified GFAC exhibited adsorption isotherms of hybrid Type I-IV isotherms with H4 hysteresis. BET surface area, micropore area, total pore volume, micropore volume, and microporosity of the modified GFAC increased by 7.33%, 11.25%, 3.89%, 14.23%, 9.91%, respectively. Whereas the average pore width decreased by 3.16%. In addition, the amount of surface oxygen groups (such as carbonyl or carboxyl) increased in the modified GFAC.

Preparation of sandwich-structured graphene/mesoporous silica composites with C8-modified pore wall for highly efficient selective enrichment of endogenous peptides for mass spectrometry analysis.

PubMed

Yin, Peng; Wang, Yuhua; Li, Yan; Deng, Chunhui; Zhang, Xiangmin; Yang, Pengyuan

2012-09-01

In this study, sandwich-structured graphene/mesoporous silica composites (C8-modified graphene@mSiO(2)) were synthesized by coating mesoporous silica onto hydrophilic graphene nanosheets through a surfactant-mediated cocondensation sol-gel process. The newly prepared C8-modified graphene@mSiO(2) nanocomposites possess unique properties of extended plate-like morphology, good water dispersibility, highly open pore structure, uniform pore size (2.8 nm), high surface area (632 m(2)/g), and C8-modified-interior pore walls. The unique structure of the C8-modified graphene@mSiO(2) composite nanosheets not only provide extended planes with hydrophilic surface that prevents aggregation in solution, but also offer a huge number of C8-modified mesopores with high surface area that can ensure an efficient adsorption of peptides through hydrophobic-hydrophobic interaction between C8-moified pore walls and target molecules. The obtained C8-modified graphene@mSiO(2) materials were utilized for size selectively and specifically enriching peptides in standard peptide mixtures and endogenous peptides in real biological samples (mouse brain tissue). © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional Analysis of Problem Behavior: A Systematic Approach for Identifying Idiosyncratic Variables

PubMed Central

Roscoe, Eileen M.; Schlichenmeyer, Kevin J.; Dube, William V.

2015-01-01

When inconclusive functional analysis (FA) outcomes occur, a number of modifications have been made to enhance the putative establishing operation or consequence associated with behavioral maintenance. However, a systematic method for identifying relevant events to test during modified FAs has not been evaluated. The purpose of this study was to develop and evaluate a technology for systematically identifying events to test in a modified FA after an initial FA led to inconclusive outcomes. Six individuals whose initial FA showed little or no responding or high levels only in the control condition participated. An indirect assessment (IA) questionnaire developed for identifying idiosyncratic variables was administered, and a descriptive analysis (DA) was conducted. Results from the IA only or a combination of the IA and DA were used to inform modified FA test and control conditions. Conclusive FA outcomes were obtained with five of the six participants during the modified FA phase. PMID:25930176

Effect of mixing proportion on the properties of seaweed modified sustainable concrete

NASA Astrophysics Data System (ADS)

Siddique, Md Nurul Islam; Wahid, Zularisam bin Abd

2017-10-01

Although the application of organic polymer has already been reported in the development of polymer modification process the use of carbohydrate polymer hasn't been reported till date. The effect of mixing ratio of seaweed modified mortar on the properties of sustainable concrete was investigated. A number of mixing ratios of seaweed (gel) with cement, sand and water (such as 0.1; 0.6; 1.1; 6) was studied in this work. In addition, a range of mixing ratios of seaweed (powder) with cement, sand and water (such as 0.1; 0.3; 0.6; 1.1; 2.1, 5.1) was examined. The performance of the seaweed modified sustainable concrete was evaluated by compressive and splitting strength. Results revealed that seaweed modified concrete with mixing ratio (0.6) was optimum. This ratio produced significant compressive and splitting strength of 30 MPa and 5 MPa for 28 days, respectively.

7 CFR 1753.93 - Responsibilities.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Approval of field trials. (9) Approval to modify or alter standard forms and contracts. (10) Approval to open bids when fewer than the required number have been received. (11) Approval of outside plant...

78 FR 50475 - Self-Regulatory Organizations; NYSE MKT LLC; Notice of Filing and Immediate Effectiveness of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-19

... Amending Commentary .10 to Rule 903 To Modify the Short-Term Option Series Program To Increase the Number... option series (``Short-Term Option Series'' or ``STOS'') Program to increase the number of classes that... respective rules. \\3\\ A Short-Term Option Series is a series of an option class that is approved for listing...

46 CFR 54.01-5 - Scope (modifies U-1 and U-2).

Code of Federal Regulations, 2010 CFR

2010-10-01

... (approved by the Office of Management and Budget under OMB control number 2130-0181); (2) Meet § 54.01-35... stress relief may be substituted if allowed under Subpart 54.30 of this chapter. III (a) Vapor or gas(b... pressure vessels. (Approved by the Office of Management and Budget under OMB control number 2130-0181...

46 CFR 54.01-5 - Scope (modifies U-1 and U-2).

Code of Federal Regulations, 2013 CFR

2013-10-01

... (approved by the Office of Management and Budget under OMB control number 2130-0181); (2) Meet § 54.01-35... stress relief may be substituted if allowed under subpart 54.30 of this chapter. III (a) Vapor or gas(b... pressure vessels. (Approved by the Office of Management and Budget under OMB control number 2130-0181...

46 CFR 54.01-5 - Scope (modifies U-1 and U-2).

Code of Federal Regulations, 2012 CFR

2012-10-01

... (approved by the Office of Management and Budget under OMB control number 2130-0181); (2) Meet § 54.01-35... stress relief may be substituted if allowed under Subpart 54.30 of this chapter. III (a) Vapor or gas(b... pressure vessels. (Approved by the Office of Management and Budget under OMB control number 2130-0181...

46 CFR 54.01-5 - Scope (modifies U-1 and U-2).

Code of Federal Regulations, 2011 CFR

2011-10-01

... (approved by the Office of Management and Budget under OMB control number 2130-0181); (2) Meet § 54.01-35... stress relief may be substituted if allowed under Subpart 54.30 of this chapter. III (a) Vapor or gas(b... pressure vessels. (Approved by the Office of Management and Budget under OMB control number 2130-0181...

77 FR 5284 - Self-Regulatory Organizations; The Options Clearing Corporation; Notice of Filing of Proposed...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-02

... governance structure of OCC by (i) increasing the number of public directors on the Board from one to three... any comments it received on the proposed rule change. The text of these statements may be examined at... change is to modify the corporate governance structure of OCC by (i) increasing the number of public...

Characterization of the Auroral Electrojet and the Ambient and Modified D Region for HAARP Using Long-Path VLF Diagnostics

DTIC Science & Technology

2001-03-15

order to characterize the auroral electrojet and the ambient and modified D-region directly above and near the HAARP (High Frequency Active Auroral...near the HAARP facility and along the west coast of Alaska. In addition in order to characterize the auroral electrojet on a continental scale and to...United States and Canada. Data from the complete array of D-region diagnostic systems was acquired during a number of Fall and Spring HAARP campaigns

A three-dimensional ground-water-flow model modified to reduce computer-memory requirements and better simulate confining-bed and aquifer pinchouts

USGS Publications Warehouse

Leahy, P.P.

1982-01-01

The Trescott computer program for modeling groundwater flow in three dimensions has been modified to (1) treat aquifer and confining bed pinchouts more realistically and (2) reduce the computer memory requirements needed for the input data. Using the original program, simulation of aquifer systems with nonrectangular external boundaries may result in a large number of nodes that are not involved in the numerical solution of the problem, but require computer storage. (USGS)

Laser modified processes: bremsstrahlung and inelastic photon atom scattering

NASA Astrophysics Data System (ADS)

Budriga, Olimpia; Dondera, Mihai; Florescu, Viorica

2007-08-01

We consider the influence of a low-frequency monochromatic external electromagnetic field (the laser) on two basic atomic processes: electron Coulomb bremsstrahlung and inelastic photon scattering on an electron bound in the ground state of a hydrogenic atom. We briefly describe the approximations adopted and illustrate in figures how the laser parameters modify the shape of the differential cross-sections and extend the energy domain for emitted electrons, due to simultaneous absorption or emission of a large number (hundreds) of laser photons.

Modified global and modified linear contrast stretching algorithms: new colour contrast enhancement techniques for microscopic analysis of malaria slide images.

PubMed

Abdul-Nasir, Aimi Salihah; Mashor, Mohd Yusoff; Mohamed, Zeehaida

2012-01-01

Malaria is one of the serious global health problem, causing widespread sufferings and deaths in various parts of the world. With the large number of cases diagnosed over the year, early detection and accurate diagnosis which facilitates prompt treatment is an essential requirement to control malaria. For centuries now, manual microscopic examination of blood slide remains the gold standard for malaria diagnosis. However, low contrast of the malaria and variable smears quality are some factors that may influence the accuracy of interpretation by microbiologists. In order to reduce this problem, this paper aims to investigate the performance of the proposed contrast enhancement techniques namely, modified global and modified linear contrast stretching as well as the conventional global and linear contrast stretching that have been applied on malaria images of P. vivax species. The results show that the proposed modified global and modified linear contrast stretching techniques have successfully increased the contrast of the parasites and the infected red blood cells compared to the conventional global and linear contrast stretching. Hence, the resultant images would become useful to microbiologists for identification of various stages and species of malaria.

Modified Rice Straw as Adsorbent Material to Remove Aflatoxin B1 from Aqueous Media and as a Fiber Source in Fino Bread

PubMed Central

Mohamed, Sherif R.; El-Desouky, Tarek A.; Hussein, Ahmed M. S.; Mohamed, Sherif S.; Naguib, Khayria M.

2016-01-01

The aims of the current work are in large part the benefit of rice straw to be used as adsorbent material and natural source of fiber in Fino bread. The rice straw was subjected to high temperature for modification process and the chemical composition was carried out and the native rice straw contained about 41.15% cellulose, 20.46% hemicellulose, and 3.91% lignin while modified rice straw has 42.10, 8.65, and 5.81%, respectively. The alkali number was tested and showed an increase in the alkali consumption due to the modification process. The different concentrations of modified rice straw, aflatoxin B1, and pH were tested for removal of aflatoxin B1 from aqueous media and the maximum best removal was at 5% modified rice straw, 5 ng/mL aflatoxin B1, and pH 7. The modified rice straw was added to Fino bread at a level of 5, 10, and 15% and the chemical, rheological, baking quality, staling, and sensory properties were studied. Modified rice straw induced an increase of the shelf life and the produced Fino bread has a better consistency. PMID:26989411

Artificial specific binders directly recovered from chemically modified nucleic acid libraries.

PubMed

Kasahara, Yuuya; Kuwahara, Masayasu

2012-01-01

Specific binders comprised of nucleic acids, that is, RNA/DNA aptamers, are attractive functional biopolymers owing to their potential broad application in medicine, food hygiene, environmental analysis, and biological research. Despite the large number of reports on selection of natural DNA/RNA aptamers, there are not many examples of direct screening of chemically modified nucleic acid aptamers. This is because of (i) the inferior efficiency and accuracy of polymerase reactions involving transcription/reverse-transcription of modified nucleotides compared with those of natural nucleotides, (ii) technical difficulties and additional time and effort required when using modified nucleic acid libraries, and (iii) ambiguous efficacies of chemical modifications in binding properties until recently; in contrast, the effects of chemical modifications on biostability are well studied using various nucleotide analogs. Although reports on the direct screening of a modified nucleic acid library remain in the minority, chemical modifications would be essential when further functional expansion of nucleic acid aptamers, in particular for medical and biological uses, is considered. This paper focuses on enzymatic production of chemically modified nucleic acids and their application to random screenings. In addition, recent advances and possible future research are also described.

Gene selection for cancer classification with the help of bees.

PubMed

Moosa, Johra Muhammad; Shakur, Rameen; Kaykobad, Mohammad; Rahman, Mohammad Sohel

2016-08-10

Development of biologically relevant models from gene expression data notably, microarray data has become a topic of great interest in the field of bioinformatics and clinical genetics and oncology. Only a small number of gene expression data compared to the total number of genes explored possess a significant correlation with a certain phenotype. Gene selection enables researchers to obtain substantial insight into the genetic nature of the disease and the mechanisms responsible for it. Besides improvement of the performance of cancer classification, it can also cut down the time and cost of medical diagnoses. This study presents a modified Artificial Bee Colony Algorithm (ABC) to select minimum number of genes that are deemed to be significant for cancer along with improvement of predictive accuracy. The search equation of ABC is believed to be good at exploration but poor at exploitation. To overcome this limitation we have modified the ABC algorithm by incorporating the concept of pheromones which is one of the major components of Ant Colony Optimization (ACO) algorithm and a new operation in which successive bees communicate to share their findings. The proposed algorithm is evaluated using a suite of ten publicly available datasets after the parameters are tuned scientifically with one of the datasets. Obtained results are compared to other works that used the same datasets. The performance of the proposed method is proved to be superior. The method presented in this paper can provide subset of genes leading to more accurate classification results while the number of selected genes is smaller. Additionally, the proposed modified Artificial Bee Colony Algorithm could conceivably be applied to problems in other areas as well.

Understanding the Role of O-GlcNAc Modifications in Plant Development

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

Olszewski, Neil, E.

2011-06-16

This project has contributed towards understanding the role of O-GlcNAc (O-linked N-acetylglucosamine) transferases (OGTs) in plants. Through analyses of single and double mutants, we have investigated the unique and overlapping functions of SECRET AGENT (SEC) and SPINDLY (SPY), the arabidopsis OGTs. This work showed that SEC functions as negative regulators of the long-day flowering pathway. SEC also has a positive role in regulation of rosette. An E. coli co-expression system that allows potential substrates to be co-expressed with and O-GlcNAc modified by SEC was developed. We showed that SEC is a bona fide OGT that modifies itself with single O-linkedmore » GlcNAc(s). Using this system, we tested a number of proteins that were hypothesized to be substrates of SEC and identified a number of substrates include GIGANTEA (GI), a component of the long day flowering pathway. The hypothesis that O-GlcNAc modification controls GI activity was tested by first mapping where E. coli-expressed SEC modifies GI and then assessing the activity of a non-modifiable mutant form of GI. The activity of the mutant form of GI was indistinguishable from that of wild type suggesting that either O-GlcNAc does not regulate GI activity or that additional modification sites exist on GI. In collaboration with Dr. Juan Antonio Garcia at Universidad Autónoma de Madrid the role of O-GlcNAc modification of the plum pox virus coat protein (PPV-CP) was investigated. SEC was shown to O-GlcNAc modify PPV-CP and the modification was shown to facilitate the infection process. E. coli-expressed SEC was shown to modify the same PPV-CP sites that are modified in plants. SEC has a large protein interaction domain called the TPR domain that has been hypothesized to have a role in determining the substrate specificity of the enzyme and/or to regulate its activity. A mutational analysis of the TPR domain did not find evidence for a role in substrate specificity but did obtain evidence that the domain regulates enzyme activity.« less

Peptide- and Amine-Modified Glucan Particles for the Delivery of Therapeutic siRNA

PubMed Central

Aouadi, Myriam; Vangala, Pranitha; Tencerova, Michaela; Amano, Shinya U.; Nicoloro, Sarah M.; Yawe, Joseph C.; Czech, Michael P.

2016-01-01

Translation of siRNA technology into the clinic is limited by the need for improved delivery systems that target specific cell types. Macrophages are particularly attractive targets for RNAi therapy because they promote pathogenic inflammatory responses in a number of important human diseases. We previously demonstrated that a multi-component formulation of β-1,3-D-glucan-encapsulated siRNA particles (GeRPs) can specifically and potently silence genes in mouse macrophages. A major advance would be to simplify the GeRP system by reducing the number of delivery components, thus enabling more facile manufacturing and future commercialization. Here we report the synthesis and evaluation of a simplified glucan-based particle (GP) capable of delivering siRNA in vivo to selectively silence macrophage genes. Covalent attachment of small-molecule amines and short peptides containing weak bases to GPs facilitated electrostatic interaction of the particles with siRNA and aided in the endosomal release of siRNA by the proton-sponge effect. Modified GPs were non-toxic and were efficiently internalized by macrophages in vitro. When injected intraperitoneally (i.p.), several of the new peptide-modified GPs were found to efficiently deliver siRNA to peritoneal macrophages in lean, healthy mice. In an animal model of obesity-induced inflammation, i.p. administration of one of the peptide-modified GPs (GP-EP14) bound to siRNA selectively reduced the expression of target inflammatory cytokines in the visceral adipose tissue macrophages. Decreasing adipose tissue inflammation resulted in an improvement of glucose metabolism in these metabolically challenged animals. Thus, modified GPs represent a promising new simplified system for the efficient delivery of therapeutic siRNAs specifically to phagocytic cells in vivo for modulation of inflammation responses. PMID:26815386

The Hypoglycemic Risk of Glyburide (Glibenclamide) Compared with Modified-Release Gliclazide.

PubMed

Clemens, Kristin K; McArthur, Eric; Dixon, Stephanie N; Fleet, Jamie L; Hramiak, Irene; Garg, Amit X

2015-08-01

The risk for hypoglycemia when taking glyburide compared with modified-release gliclazide remains to be established in older adults in routine care. We investigated the risk of a hospital encounter with hypoglycemia following a new prescription for glyburide compared with modified-release gliclazide. In 2 population-based matched retrospective cohort studies in Ontario, Canada, between 2002 and 2011, we examined older adults who were newly prescribed glyburide or gliclazide as monotherapy or in the presence of metformin. Our primary outcome was a hospital encounter with hypoglycemia assessed within 90 days. The baseline characteristics between matched groups were similar. Initiating glyburide vs. gliclazide as monotherapy was associated with a higher risk for a hospital encounter with hypoglycemia (69 patients of 4374 taking glyburide [1.58%] vs. 8 patients of 4374 taking gliclazide [0.18%], absolute risk increase 1.40% [95% CI 1.01% to 1.79%], number needed to harm 71 [55 to 99], odds ratio 8.63 [95% CI 4.15 to 17.93], p<0.0001). Similar findings were noted when glyburide vs. gliclazide was initiated in the presence of metformin (110 patients of 8038 taking glyburide [1.37%] vs. 19 patients of 8038 taking gliclazide [0.24%], absolute risk increase 1.13% [95% CI 0.86% to 1.40%], number needed to harm 77 [71 to 116], odds ratio 6.06 [95% CI 3.68 to 9.97], p<0.0001). Glyburide was associated with a higher risk for hypoglycemia than modified-release gliclazide. The results of our studies may help to convince healthcare professionals who use glyburide to consider modified-release gliclazide as a safer alternative. Copyright © 2015 Canadian Diabetes Association. Published by Elsevier Inc. All rights reserved.

Identifying Treatment Effect Modifiers in the STarT Back Trial: A Secondary Analysis.

PubMed

Beneciuk, Jason M; Hill, Jonathan C; Campbell, Paul; Afolabi, Ebenezer; George, Steven Z; Dunn, Kate M; Foster, Nadine E

2017-01-01

Identification of patient characteristics influencing treatment outcomes is a top low back pain (LBP) research priority. Results from the STarT Back trial support the effectiveness of prognostic stratified care for LBP compared with current best care, however, patient characteristics associated with treatment response have not yet been explored. The purpose of this secondary analysis was to identify treatment effect modifiers within the STarT Back trial at 4-month follow-up (n = 688). Treatment response was dichotomized using back-specific physical disability measured using the Roland-Morris Disability Questionnaire (≥7). Candidate modifiers were identified using previous literature and evaluated using logistic regression with statistical interaction terms to provide preliminary evidence of treatment effect modification. Socioeconomic status (SES) was identified as an effect modifier for disability outcomes (odds ratio [OR] = 1.71, P = .028). High SES patients receiving prognostic stratified care were 2.5 times less likely to have a poor outcome compared with low SES patients receiving best current care (OR = .40, P = .006). Education level (OR = 1.33, P = .109) and number of pain medications (OR = .64, P = .140) met our criteria for effect modification with weaker evidence (.20 > P ≥ .05). These findings provide preliminary evidence for SES, education, and number of pain medications as treatment effect modifiers of prognostic stratified care delivered in the STarT Back Trial. This analysis provides preliminary exploratory findings about the characteristics of patients who might least likely benefit from targeted treatment using prognostic stratified care for LBP. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

U.S. Strategic Nuclear Forces: Background, Developments, and Issues

DTIC Science & Technology

2015-03-18

5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Congressional Research Service,The...extend the life of the missiles and warheads so that they and the submarines can remain in the fleet past 2020. It is designing a new submarine and...modifying and extending the life of the B61 bomb carried on B-2 bombers and fighter aircraft. The Obama Administration completed a review of the size and

Canonical Probability Distributions for Model Building, Learning, and Inference

DTIC Science & Technology

2006-07-14

hand , are for Ranked nodes set at Unobservable and Auxiliary nodes. The value of alpha is set in the diagnostic window by moving the slider in the upper...right hand side of the window. The upper bound of alpha can be modified by typing the new value in the small edit box to the right of the slider. f...TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER University of Pittsburgh

Magnetic Properties of the DNA-Quaternary Ammonium Surfactant Complexes Studied by EMR Spectroscopy and SQUID Measurement

DTIC Science & Technology

2008-09-24

Eui Doo Do, Dong Hoon Choi, and Jung -Il Jin∗ Department of Chemistry, Korea University, Seoul 136-701, Korea Chang Hoon Lee Department of Polymer...Electromagnetic Properties of Modified DNA 5a. CONTRACT NUMBER FA48690714023 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Jung -Il Jin 5d...the last temperature- independent χPauli is the Pauli spin susceptibility attributed by delocalized con- ductive spin species. The molar

Ectopic expression of anti-HIV-1 shRNAs protects CD8{sup +} T cells modified with CD4ζ CAR from HIV-1 infection and alleviates impairment of cell proliferation

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

Kamata, Masakazu, E-mail: masa3k@ucla.edu; Kim, Patrick Y.; Ng, Hwee L.

Chimeric antigen receptors (CARs) are artificially engineered receptors that confer a desired specificity to immune effector T cells. As an HIV-1-specific CAR, CD4ζ CAR has been extensively tested in vitro as well as in clinical trials. T cells modified with this CAR mediated highly potent anti-HIV-1 activities in vitro and were well-tolerated in vivo, but exerted limited effects on viral load and reservoir size due to poor survival and/or functionality of the transduced cells in patients. We hypothesize that ectopic expression of CD4ζ on CD8{sup +} T cells renders them susceptible to HIV-1 infection, resulting in poor survival of those cells. To testmore » this possibility, highly purified CD8{sup +} T cells were genetically modified with a CD4ζ-encoding lentiviral vector and infected with HIV-1. CD8{sup +} T cells were vulnerable to HIV-1 infection upon expression of CD4ζ as evidenced by elevated levels of p24{sup Gag} in cells and culture supernatants. Concurrently, the number of CD4ζ-modified CD8{sup +} T cells was reduced relative to control cells upon HIV-1 infection. To protect these cells from HIV-1 infection, we co-expressed two anti-HIV-1 shRNAs previously developed by our group together with CD4ζ. This combination vector was able to suppress HIV-1 infection without impairing HIV-1-dependent effector activities of CD4ζ. In addition, the number of CD4ζ-modified CD8{sup +} T cells maintained similar levels to that of the control even under HIV-1 infection. These results suggest that protecting CD4ζ-modified CD8{sup +} T cells from HIV-1 infection is required for prolonged HIV-1-specific immune surveillance. - Highlights: • Ectopic expression of CD4ζ CAR in CD8{sup +} T cells renders them susceptible to HIV-1 infection. • Co-expression of two anti-HIV-1 shRNAs protects CD4ζ CAR-modified CD8{sup +} T cells from HIV-1 infection. • Protecting CD4ζ CAR-modified CD8{sup +} T cells from HIV-1 infection suppresses its cytopathic effect.« less

75 FR 15434 - Agency Information Collection Activities: Proposed Collection; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-29

... beneficiaries. The Deficit Reduction Act (DRA) of 2005 modified section 1927 to require additional reporting... Regulations Development, Attention: Document Identifier/OMB Control Number, Room C4-26-05, 7500 Security...

Performance Analysis of Combined Methods of Genetic Algorithm and K-Means Clustering in Determining the Value of Centroid

NASA Astrophysics Data System (ADS)

Adya Zizwan, Putra; Zarlis, Muhammad; Budhiarti Nababan, Erna

2017-12-01

The determination of Centroid on K-Means Algorithm directly affects the quality of the clustering results. Determination of centroid by using random numbers has many weaknesses. The GenClust algorithm that combines the use of Genetic Algorithms and K-Means uses a genetic algorithm to determine the centroid of each cluster. The use of the GenClust algorithm uses 50% chromosomes obtained through deterministic calculations and 50% is obtained from the generation of random numbers. This study will modify the use of the GenClust algorithm in which the chromosomes used are 100% obtained through deterministic calculations. The results of this study resulted in performance comparisons expressed in Mean Square Error influenced by centroid determination on K-Means method by using GenClust method, modified GenClust method and also classic K-Means.

Development of melting temperature-based SYBR Green I polymerase chain reaction methods for multiplex genetically modified organism detection.

PubMed

Hernández, Marta; Rodríguez-Lázaro, David; Esteve, Teresa; Prat, Salomé; Pla, Maria

2003-12-15

Commercialization of several genetically modified crops has been approved worldwide to date. Uniplex polymerase chain reaction (PCR)-based methods to identify these different insertion events have been developed, but their use in the analysis of all commercially available genetically modified organisms (GMOs) is becoming progressively insufficient. These methods require a large number of assays to detect all possible GMOs present in the sample and thereby the development of multiplex PCR systems using combined probes and primers targeted to sequences specific to various GMOs is needed for detection of this increasing number of GMOs. Here we report on the development of a multiplex real-time PCR suitable for multiple GMO identification, based on the intercalating dye SYBR Green I and the analysis of the melting curves of the amplified products. Using this method, different amplification products specific for Maximizer 176, Bt11, MON810, and GA21 maize and for GTS 40-3-2 soybean were obtained and identified by their specific Tm. We have combined amplification of these products in a number of multiplex reactions and show the suitability of the methods for identification of GMOs with a sensitivity of 0.1% in duplex reactions. The described methods offer an economic and simple alternative to real-time PCR systems based on sequence-specific probes (i.e., TaqMan chemistry). These methods can be used as selection tests and further optimized for uniplex GMO quantification.

Modified visual field trend analysis.

PubMed

De Moraes, Carlos Gustavo V; Ritch, Robert; Tello, Celso; Liebmann, Jeffrey M

2011-01-01

Visual field trend analysis can be influenced by outlying values that may disproportionately affect estimation of the rate of change. We tested a modified approach to visual field trend analysis to minimize this problem. Automated pointwise linear regression (PLR) was used in glaucoma patients with ≥13 SITA-Standard 24-2 VF tests in either eye. In the control group (Group A), conventional PLR using the entire set of VF tests was carried out. In the other 3 groups (study groups), a truncated analysis was done using only the first and last 3 (Group B), first and last 4 (Group C), or first and last 5 (Group D) VF tests. We compared the global slopes (dB/y), number of eyes experiencing significant progression, and significant improvement between groups. Ninety eyes of 90 patients were evaluated. The mean number±SD of VF tests was 15.7±2.6, spanning 7.8±1.7 years. The study groups showed similar global rates of VF change as the control group (Group A=-0.48±0.5, Group B=-0.48±0.6, Group C=-0.48±0.6, Group D=-0.48±0.5 dB/y, P>0.05), and a similar number of eyes reaching a progression endpoint (Group A=53, Group B=52, Group C=49, Group D=53, P>0.05). However, Group B showed fewer eyes presenting VF improvement (false-positives). The modified VF trend-analysis showed greater specificity than conventional PLR in a population with glaucoma.

Reversible Venting Stitch for Fenestrating Valve-less Glaucoma Shunts.

PubMed

Akil, Handan; Vu, Priscilla Q; Nguyen, Anhtuan H; Nugent, Alexander; Chopra, Vikas; Francis, Brian A; Tan, James C

2017-12-01

The purpose of this is to describe a venting stitch modification for valveless glaucoma aqueous shunts and characterize early postoperative intraocular pressure (IOP) and glaucoma medication use following the modification. Retrospective chart review of 61 sequential patients undergoing Baerveldt glaucoma implant (BGI)-350 implantation at the Doheny Eye Institute. Twenty-four patients received a glaucoma shunt with venting stitch modification (modified BGI) and 37 patients received an unmodified shunt (BGI-only). IOP, number of glaucoma medications, and number of hypotony cases (intraocular pressure ≤5 mm Hg) were compared between the groups. T-tests were used for statistical analysis. At postoperative-day 1, mean IOP was significantly lower compared with preoperatively in the modified BGI group (14 mm Hg; reduced by 51%; P<0.0001) but not the BGI-only group (27 mm Hg; P=0.06). IOP difference between groups persisted till immediately before tube opening (P=0.005) and fewer IOP-lowering medications needed in the modified BGI group (P<0.0001). One case (4.2%) of postoperative hypotony was encountered with BGI modification, which resolved after the stitch was removed in clinic. The venting stitch valveless shunt modification allows for effective, reliable, and safe control of early postoperative IOP.

Moving force identification based on modified preconditioned conjugate gradient method

NASA Astrophysics Data System (ADS)

Chen, Zhen; Chan, Tommy H. T.; Nguyen, Andy

2018-06-01

This paper develops a modified preconditioned conjugate gradient (M-PCG) method for moving force identification (MFI) by improving the conjugate gradient (CG) and preconditioned conjugate gradient (PCG) methods with a modified Gram-Schmidt algorithm. The method aims to obtain more accurate and more efficient identification results from the responses of bridge deck caused by vehicles passing by, which are known to be sensitive to ill-posed problems that exist in the inverse problem. A simply supported beam model with biaxial time-varying forces is used to generate numerical simulations with various analysis scenarios to assess the effectiveness of the method. Evaluation results show that regularization matrix L and number of iterations j are very important influence factors to identification accuracy and noise immunity of M-PCG. Compared with the conventional counterpart SVD embedded in the time domain method (TDM) and the standard form of CG, the M-PCG with proper regularization matrix has many advantages such as better adaptability and more robust to ill-posed problems. More importantly, it is shown that the average optimal numbers of iterations of M-PCG can be reduced by more than 70% compared with PCG and this apparently makes M-PCG a preferred choice for field MFI applications.

Evaluation of cephamycins as supplements to selective agar for detecting Campylobacter spp. in chicken carcass rinses.

PubMed

Chon, Jung-Whan; Kim, Young-Ji; Kim, Hong-Seok; Kim, Dong-Hyeon; Kim, Hyunsook; Song, Kwang-Young; Sung, Kidon; Seo, Kun-Ho

2016-04-16

Although cefoperazone is the most commonly used antibiotic in Campylobacter-selective media, the distribution of cefoperazone-resistant bacteria such as extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli is increasing. Here we evaluated the potential of cephamycins for use as supplements to improve modified charcoal-cefoperazone-deoxycholate agar (mCCDA) by replacing cefoperazone with the same concentrations (32 mg/L) of cefotetan (modified charcoal-cefotetan-deoxycholate agar, mCCtDA) and cefoxitin (modified charcoal-cefoxitin-deoxycholate agar, mCCxDA). In chicken carcass rinse samples, the number of mCCDA plates detecting for Campylobacter (18/70, 26%) was significantly lower than that of mCCtDA (42/70, 60%) or mCCxDA plates (40/70, 57%). The number of mCCDA plates (70/70, 100%) that were contaminated with non-Campylobacter species was significantly higher than that of mCCtDA (20/70, 29%) or mCCxDA plates (21/70, 30%). The most common competing species identified using mCCDA was ESBL-producing E. coli, while Pseudomonas species frequently appeared on mCCtDA and mCCxDA. Copyright © 2016. Published by Elsevier B.V.

Analysis of modified SMI method for adaptive array weight control

NASA Technical Reports Server (NTRS)

Dilsavor, R. L.; Moses, R. L.

1989-01-01

An adaptive array is applied to the problem of receiving a desired signal in the presence of weak interference signals which need to be suppressed. A modification, suggested by Gupta, of the sample matrix inversion (SMI) algorithm controls the array weights. In the modified SMI algorithm, interference suppression is increased by subtracting a fraction F of the noise power from the diagonal elements of the estimated covariance matrix. Given the true covariance matrix and the desired signal direction, the modified algorithm is shown to maximize a well-defined, intuitive output power ratio criterion. Expressions are derived for the expected value and variance of the array weights and output powers as a function of the fraction F and the number of snapshots used in the covariance matrix estimate. These expressions are compared with computer simulation and good agreement is found. A trade-off is found to exist between the desired level of interference suppression and the number of snapshots required in order to achieve that level with some certainty. The removal of noise eigenvectors from the covariance matrix inverse is also discussed with respect to this application. Finally, the type and severity of errors which occur in the covariance matrix estimate are characterized through simulation.

Efficiency of colored modified box traps for sampling of tabanids.

PubMed

Krčmar, Stjepan; Radolić, Vanja; Lajoš, Petar; Lukačević, Igor

2014-01-01

The efficiency of ten differently colored modified box traps for collecting tabanids was studied in the Monjoroš Forest in eastern Croatia. A total of 5,436 specimens belonging to 16 species of tabanids grouped into six genera were collected. The genus Tabanus was the most represented with 98% of all collected tabanids. Tabanus bromius comprised 90% of tabanids collected, and was the most abundant species collected in all box traps. The majority of tabanids (74%) were collected from black, brown, bordeaux, red, and blue traps (dark group), whereas 26% were collected from green, light violet, white, orange, and yellow traps (light group). The black modified trap was the most successful and collected 20% of all collected tabanids, whereas the yellow trap was the least effective with 1%. The number of collected specimens of species T. bromius differed significantly between the dark and light group of traps. Traps with lower reflectance from green color collected 77% of T. bromius. The most species of tabanids (12) was collected in the brown trap, whereas the least number of species (6) was collected in the yellow trap. © S. Krčmar et al., published by EDP Sciences, 2014.

A theoretical introduction to "combinatory SYBRGreen qPCR screening", a matrix-based approach for the detection of materials derived from genetically modified plants.

PubMed

Van den Bulcke, Marc; Lievens, Antoon; Barbau-Piednoir, Elodie; MbongoloMbella, Guillaume; Roosens, Nancy; Sneyers, Myriam; Casi, Amaya Leunda

2010-03-01

The detection of genetically modified (GM) materials in food and feed products is a complex multi-step analytical process invoking screening, identification, and often quantification of the genetically modified organisms (GMO) present in a sample. "Combinatory qPCR SYBRGreen screening" (CoSYPS) is a matrix-based approach for determining the presence of GM plant materials in products. The CoSYPS decision-support system (DSS) interprets the analytical results of SYBRGREEN qPCR analysis based on four values: the C(t)- and T(m) values and the LOD and LOQ for each method. A theoretical explanation of the different concepts applied in CoSYPS analysis is given (GMO Universe, "Prime number tracing", matrix/combinatory approach) and documented using the RoundUp Ready soy GTS40-3-2 as an example. By applying a limited set of SYBRGREEN qPCR methods and through application of a newly developed "prime number"-based algorithm, the nature of subsets of corresponding GMO in a sample can be determined. Together, these analyses provide guidance for semi-quantitative estimation of GMO presence in a food and feed product.

Effect of vacuum and modified atmosphere packaging on microbiological properties of cold-smoked trout

NASA Astrophysics Data System (ADS)

Đorđević, J.; Pavlićević, N.; Bošković, M.; Janjić, J.; Glišić, M.; Starčević, M.; Baltić, M. Ž.

2017-09-01

Because of the importance of different packaging methods for the extension of fish shelf life, as a highly perishable food, the aim of the present study was to examine the effect of vacuum and modified atmosphere packaging on the total Enterobacteriaceae and lactic acid bacteria counts of cold-smoked Salmon trout (Oncorhynchus mykiss) stored at 3°C during six weeks. Trout fillets were vacuumed packaged (VP) or packaged in one of two different modified atmospheres, with gas ratio of 50%CO2/50%N2 (MAP1) and 90%CO2/10%N2 (MAP2) and analysed on days 0, 7, 14, 21, 28, 35 and 42. Both the total Enterobacteriaceae and total lactic acid bacteria counts increased in the trout fillets in all packaging types during storage. A significantly lower total Enterobacteriaceae count was determined in the MAP fish compared to the VP fish, with the weakest growth rate and lowest numbers attained in MAP2 fillets. The lactic acid bacteria count was higher in trout packaged in MAP compared to VP, with the highest number in the MAP with 90% CO2 (MAP2).

A modified technique for the preparation of SO2 from sulphates and sulphides for sulphur isotope analyses.

PubMed

Han, L; Tanweer, A; Szaran, J; Halas, S

2002-09-01

A modified technique for the conversion of sulphates and sulphides to SO2 with the mixture of V2O5-SiO2 for sulphur isotopic analyses is described. This technique is more suitable for routine analysis of large number of samples. Modification of the reaction vessel and using manifold inlet system allows to analyse up to 24 samples every day. The modified technique assures the complete yield of SO2, consistent oxygen isotope composition of the SO2 gas and reproducibility of delta34S measurements being within 0.10 per thousand. It is observed, however, oxygen in SO2 produced from sulphides differs in delta18O with respect to that produced from sulphates.

Water repellent properties of dispersed metals containing low-dimensional forms of ammonium compounds on the surface

NASA Astrophysics Data System (ADS)

Syrkov, A. G.; Kabirov, V. R.; Silivanov, M. O.

2017-07-01

For the first time the change of the water repellent properties of dispersed copper, modified using quaternary ammonium compounds on 24 h time scale in saturated water vapours was studied. Exponential time dependences of the water repellent properties of dispersed copper with adsopted QAC were derived and characterized. It was established that the samples modified in mixed and consistent modes by both modifiers reach the saturation state faster than others, due to the small number of hydrophilic centers on the surface of metals. The last conclusion was confirmed by the distribution spectra of centers of adsorption, which were obtained by the adsorption of acid-base indicators for more dispersed samples based on aluminum powder.

Detection of Genetically Modified Maize in Processed Foods Sold Commercially in Iran by Qualitative PCR

PubMed Central

Rabiei, Maryam; Mehdizadeh, Mehrangiz; Rastegar, Hossein; Vahidi, Hossein; Alebouyeh, Mahmoud

2013-01-01

Detection of genetically modified organisms (GMOs) in food is an important issue for all the subjects involved in food control and customer’s right. Due to the increasing number of GMOs imported to Iran during the past few years, it has become necessary to screen the products in order to determine the identity of the consumed daily foodstuffs. In this study, following the extraction of genomic DNA from processed foods sold commercially in Iran, qualitative PCR was performed to detect genetically modified maize. The recombinant DNA target sequences were detected with primers highly specific for each investigated transgene such as CaMV35s gene, Bt-11, MON810 and Bt-176 separately. Based on the gel electrophoresis results, Bt- 11 and MON810 events were detected in some maize samples, while, in none of them Bt- 176 modified gene was detected. For the first time, the results demonstrate the presence of genetically modified maize in Iranian food products, reinforcing the need for the development of labeling system and valid quantitative methods in routine analyses. PMID:24250568

Detection of genetically modified maize in processed foods sold commercially in iran by qualitative PCR.

PubMed

Rabiei, Maryam; Mehdizadeh, Mehrangiz; Rastegar, Hossein; Vahidi, Hossein; Alebouyeh, Mahmoud

2013-01-01

Detection of genetically modified organisms (GMOs) in food is an important issue for all the subjects involved in food control and customer's right. Due to the increasing number of GMOs imported to Iran during the past few years, it has become necessary to screen the products in order to determine the identity of the consumed daily foodstuffs. In this study, following the extraction of genomic DNA from processed foods sold commercially in Iran, qualitative PCR was performed to detect genetically modified maize. The recombinant DNA target sequences were detected with primers highly specific for each investigated transgene such as CaMV35s gene, Bt-11, MON810 and Bt-176 separately. Based on the gel electrophoresis results, Bt- 11 and MON810 events were detected in some maize samples, while, in none of them Bt- 176 modified gene was detected. For the first time, the results demonstrate the presence of genetically modified maize in Iranian food products, reinforcing the need for the development of labeling system and valid quantitative methods in routine analyses.

Nucleoside-modified mRNA vaccines induce potent T follicular helper and germinal center B cell responses.

PubMed

Pardi, Norbert; Hogan, Michael J; Naradikian, Martin S; Parkhouse, Kaela; Cain, Derek W; Jones, Letitia; Moody, M Anthony; Verkerke, Hans P; Myles, Arpita; Willis, Elinor; LaBranche, Celia C; Montefiori, David C; Lobby, Jenna L; Saunders, Kevin O; Liao, Hua-Xin; Korber, Bette T; Sutherland, Laura L; Scearce, Richard M; Hraber, Peter T; Tombácz, István; Muramatsu, Hiromi; Ni, Houping; Balikov, Daniel A; Li, Charles; Mui, Barbara L; Tam, Ying K; Krammer, Florian; Karikó, Katalin; Polacino, Patricia; Eisenlohr, Laurence C; Madden, Thomas D; Hope, Michael J; Lewis, Mark G; Lee, Kelly K; Hu, Shiu-Lok; Hensley, Scott E; Cancro, Michael P; Haynes, Barton F; Weissman, Drew

2018-06-04

T follicular helper (Tfh) cells are required to develop germinal center (GC) responses and drive immunoglobulin class switch, affinity maturation, and long-term B cell memory. In this study, we characterize a recently developed vaccine platform, nucleoside-modified, purified mRNA encapsulated in lipid nanoparticles (mRNA-LNPs), that induces high levels of Tfh and GC B cells. Intradermal vaccination with nucleoside-modified mRNA-LNPs encoding various viral surface antigens elicited polyfunctional, antigen-specific, CD4 + T cell responses and potent neutralizing antibody responses in mice and nonhuman primates. Importantly, the strong antigen-specific Tfh cell response and high numbers of GC B cells and plasma cells were associated with long-lived and high-affinity neutralizing antibodies and durable protection. Comparative studies demonstrated that nucleoside-modified mRNA-LNP vaccines outperformed adjuvanted protein and inactivated virus vaccines and pathogen infection. The incorporation of noninflammatory, modified nucleosides in the mRNA is required for the production of large amounts of antigen and for robust immune responses. © 2018 Pardi et al.

Thermal stability of G-rich anti-parallel DNA triplexes upon insertion of LNA and α-L-LNA.

PubMed

Kosbar, Tamer R; Sofan, Mamdouh A; Abou-Zeid, Laila; Pedersen, Erik B

2015-05-14

G-rich anti-parallel DNA triplexes were modified with LNA or α-L-LNA in their Watson-Crick and TFO strands. The triplexes were formed by targeting a pyrimidine strand to a putative hairpin formed by Hoogsteen base pairing in order to use the UV melting method to evaluate the stability of the triplexes. Their thermal stability was reduced when the TFO strand was modified with LNA or α-L-LNA. The same trend was observed when the TFO strand and the purine Watson-Crick strand both were modified with LNA. When all triad components were modified with α-L-LNA and LNA in the middle of the triplex, the thermal melting was increased. When the pyrimidine sequence was modified with a single insertion of LNA or α-L-LNA the ΔTm increased. Moreover, increasing the number of α-L-LNA in the pyrimidine target sequence to six insertions, leads to a high increase in the thermal stability. The conformational S-type structure of α-L-LNA in anti-parallel triplexes is preferable for triplex stability.

Couette flow through a porous medium with heat and mass transfer in the presence of tranverse magnetic field

NASA Astrophysics Data System (ADS)

Lawanya, T.; Vidhya, M.; Govindarajan, A.

2018-04-01

This present paper deals with the investigation of couette flow of a viscous electrically conducting incompressible fluid three dimensionally through a porous medium in presence of transverse magnetic field. Approximate Solution of equations of motion and energy equations are derived using series solution method. Hartmann number, Schmidt number and Grashoff number (or) modified Grashoff number for mass transfer on the velocity and temperature distribution are numerically discussed and shown graphically. The Nusselt number and skin friction coefficients atthe plate are derived and their numerical values are shown graphically. It is seen that in the main flow direction the velocity profiles decreases due to either an increase in Schmidt number (Or) Hartmann number.

All-optical conversion scheme from binary to its MTN form with the help of nonlinear material based tree-net architecture

NASA Astrophysics Data System (ADS)

Maiti, Anup Kumar; Nath Roy, Jitendra; Mukhopadhyay, Sourangshu

2007-08-01

In the field of optical computing and parallel information processing, several number systems have been used for different arithmetic and algebraic operations. Therefore an efficient conversion scheme from one number system to another is very important. Modified trinary number (MTN) has already taken a significant role towards carry and borrow free arithmetic operations. In this communication, we propose a tree-net architecture based all optical conversion scheme from binary number to its MTN form. Optical switch using nonlinear material (NLM) plays an important role.

Beta-defensin genomic copy number is not a modifier locus for cystic fibrosis

PubMed Central

Hollox, Edward J; Davies, Jane; Griesenbach, Uta; Burgess, Juliana; Alton, Eric WFW; Armour, John AL

2005-01-01

Human beta-defensin 2 (DEFB4, also known as DEFB2 or hBD-2) is a salt-sensitive antimicrobial protein that is expressed in lung epithelia. Previous work has shown that it is encoded in a cluster of beta-defensin genes at 8p23.1, which varies in copy number between 2 and 12 in different individuals. We determined the copy number of this locus in 355 patients with cystic fibrosis (CF), and tested for correlation between beta-defensin cluster genomic copy number and lung disease associated with CF. No significant association was found. PMID:16336654

Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro.

PubMed

Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

2015-01-01

In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866-4550 m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies.

Assessment of a Learning Strategy among Spine Surgeons.

PubMed

Gotfryd, Alberto Ofenhejm; Corredor, Jose Alfredo; Teixeira, William Jacobsen; Martins, Delio Eulálio; Milano, Jeronimo; Iutaka, Alexandre Sadao

2017-02-01

Pilot test, observational study. To evaluate objectively the knowledge transfer provided by theoretical and practical activities during AOSpine courses for spine surgeons. During two AOSpine principles courses, 62 participants underwent precourse assessment, which consisted of questions about their professional experience, preferences regarding adolescent idiopathic scoliosis (AIS) classification, and classifying the curves by means of the Lenke classification of two AIS clinical cases. Two learning strategies were used during the course. A postcourse questionnaire was applied to reclassify the same deformity cases. Differences in the correct answers of clinical cases between pre- and postcourse were analyzed, revealing the number of participants whose accuracy in classification improved after the course. Analysis showed a decrease in the number of participants with wrong answers in both cases after the course. In the first case, statistically significant differences were observed in both curve pattern (83.3%, p   =  0.005) and lumbar spine modifier (46.6%, p   =  0.049). No statistically significant improvement was seen in the sagittal thoracic modifier (33.3%, p   =  0.309). In the second case, statistical improvement was obtained in curve pattern (27.4%, p   =  0.018). No statistically significant improvement was seen regarding lumbar spine modifier (9.8%, p   =  0.121) and sagittal thoracic modifier (12.9%, p   =  0.081). This pilot test showed objectively that learning strategies used during AOSpine courses improved the participants' knowledge. Teaching strategies must be continually improved to ensure an optimal level of knowledge transfer.

Assessment of a Learning Strategy among Spine Surgeons

PubMed Central

Gotfryd, Alberto Ofenhejm; Teixeira, William Jacobsen; Martins, Delio Eulálio; Milano, Jeronimo; Iutaka, Alexandre Sadao

2017-01-01

Study Design Pilot test, observational study. Objective To evaluate objectively the knowledge transfer provided by theoretical and practical activities during AOSpine courses for spine surgeons. Methods During two AOSpine principles courses, 62 participants underwent precourse assessment, which consisted of questions about their professional experience, preferences regarding adolescent idiopathic scoliosis (AIS) classification, and classifying the curves by means of the Lenke classification of two AIS clinical cases. Two learning strategies were used during the course. A postcourse questionnaire was applied to reclassify the same deformity cases. Differences in the correct answers of clinical cases between pre- and postcourse were analyzed, revealing the number of participants whose accuracy in classification improved after the course. Results Analysis showed a decrease in the number of participants with wrong answers in both cases after the course. In the first case, statistically significant differences were observed in both curve pattern (83.3%, p  =  0.005) and lumbar spine modifier (46.6%, p  =  0.049). No statistically significant improvement was seen in the sagittal thoracic modifier (33.3%, p  =  0.309). In the second case, statistical improvement was obtained in curve pattern (27.4%, p  =  0.018). No statistically significant improvement was seen regarding lumbar spine modifier (9.8%, p  =  0.121) and sagittal thoracic modifier (12.9%, p  =  0.081). Conclusion This pilot test showed objectively that learning strategies used during AOSpine courses improved the participants' knowledge. Teaching strategies must be continually improved to ensure an optimal level of knowledge transfer. PMID:28451507

Risk to Resilience: Exploring Protective Factors for Students Experiencing Homelessness at a Traditional High School and a Modified Comprehensive School

ERIC Educational Resources Information Center

Garcia, Joel

2013-01-01

In 2008-2009, almost one million children experiencing homelessness were enrolled in school; this number has increased by 41% between 2009 and 2011. Unfortunately, this trend has continued to increase; according to the most recent data from the National Center for Homeless Education, the number of homeless students has reached a record of…

Vortex-Surface Interactions: Vortex Dynamics and Instabilities

DTIC Science & Technology

2015-10-16

31 May 2015 4. TITLE AND SUBTITLE VORTEX -SURFACE INTERACTIONS: VORTEX DYNAMICS AND INSTABILITIES Sa. CONTRACT NUMBER Sb. GRANT NUMBER N00014-12...new natural instabilities coming from vortex - vortex or vortex -surface interactions, but also ultimately the possibility to control these flows...design of vortex generators to modify surface pressures. We find a short wave instability of the secondary vortices that are created by the

Targeting the Mevalonate Pathway to Reduce Mortality from Ovarian Cancer

DTIC Science & Technology

2016-10-01

PREPARED FOR: U.S. Army Medical Research and Materiel Command Fort Detrick, Maryland 21702-5012 DISTRIBUTION STATEMENT: Approved for Public... Research and Materiel Command Fort Detrick, Maryland 21702-5012 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION / AVAILABILITY STATEMENT...other lipid lowering agents; and b) test whether the association is modified by: i) dose and duration, ii) timing of the intervention (pre-diagnosis

Lysosomal pH-inducible supramolecular dissociation of polyrotaxanes possessing acid-labile N-triphenylmethyl end groups and their therapeutic potential for Niemann-Pick type C disease

NASA Astrophysics Data System (ADS)

Tamura, Atsushi; Nishida, Kei; Yui, Nobuhiko

2016-01-01

Niemann-Pick type C (NPC) disease is characterized by the accumulation of cholesterol in lysosomes. We have previously reported that biocleavable polyrotaxanes (PRXs) composed of β-cyclodextrins (β-CDs) threaded onto a linear polymer capped with bulky stopper molecules via intracellularly cleavable linkers show remarkable cholesterol reducing effects in NPC disease patient-derived fibroblasts owing to the stimuli-responsive intracellular dissociation of PRXs and subsequent β-CD release from the PRXs. Herein, we describe a series of novel acid-labile 2-(2-hydroxyethoxy)ethyl group-modified PRXs (HEE-PRXs) bearing terminal N-triphenylmethyl (N-Trt) groups as a cleavable component for the treatment of NPC disease. The N-Trt end groups of the HEE-PRXs underwent acidic pH-induced cleavage and led to the dissociation of their supramolecular structure. A kinetic study revealed that the number of HEE groups on the PRX did not affect the cleavage kinetics of the N-Trt end groups of the HEE-PRXs. The effect of the number of HEE groups of the HEE-PRXs, which was modified to impart water solubility to the PRXs, on cellular internalization efficiency, lysosomal localization efficiency, and cholesterol reduction ability in NPC disease-derived fibroblasts (NPC1 fibroblasts) was also investigated. The cellular uptake and lysosomal localization efficiency were almost equivalent for HEE-PRXs with different numbers of HEE groups. However, the cholesterol reducing ability of the HEE-PRXs in NPC1 fibroblasts was affected by the number of HEE groups, and HEE-PRXs with a high number of HEE groups were unable to reduce lysosomal cholesterol accumulation. This deficiency is most likely due to the cholesterol-solubilizing ability of HEE-modified β-CDs released from the HEE-PRXs. We conclude that the N-Trt group acts as a cleavable component to induce the lysosomal dissociation of HEE-PRXs, and acid-labile HEE-PRXs with an optimal number of HEE groups (4.1 to 5.4 HEE groups per single β-CD threaded onto the PRX) have great therapeutic potential for treating NPC disease.

Application of pH-sensitive fusogenic polymer-modified liposomes for development of mucosal vaccines.

PubMed

Watarai, Shinobu; Iwase, Tana; Tajima, Tomoko; Yuba, Eiji; Kono, Kenji; Sekiya, Yukio

2014-03-15

To evaluate the usefulness of pH-sensitive fusogenic polymer (succinylated poly(glycidol) (SucPG) and 3-methylglutarylated poly(glycidol) (MGluPG))-modified liposomes as mucosal vaccine in the induction of a protective immune responses was evaluated. Mice were nasally immunized with OVA-containing SucPG-modified liposomes. After immunization, significant Ag-specific Abs were detected in the serum and intestine. When sera were analyzed for isotype distribution, antigen-specific IgG1 Ab responses were noted in mice immunized with OVA-containing polymer-unmodified liposomes, whereas immunization with OVA-containing SucPG-modified liposomes resulted in the induction of OVA-specific IgG1, IgG2a and IgG3 Ab responses. In spleen lymphocytes from mice immunized with OVA-containing SucPG-modified liposomes, both IFN-γ and IL-4 mRNA were detected. The same result was obtained also in the mouse immunized with OVA-containing MGluPG-modified liposomes. Furthermore, we examined the induction of immune responses in chickens following intraocular immunization with Salmonella Enteritidis Ag-containing MGluPG-modified liposomes, and the protective effect against the challenge with S. Enteritidis. Immunization with S. Enteritidis Ag-containing MGluPG-modified liposomes induced significant Ab responses against S. Enteritidis in the serum and intestine. Less fecal excretion of bacteria was observed in chickens immunized with S. Enteritidis Ag-containing MGluPG-modified liposomes after challenge. The numbers of bacteria in the caecum were also lower in immunized chickens than in unimmunized controls. Copyright © 2013 Elsevier B.V. All rights reserved.

Interchangeability, Safety and Efficacy of Modified-Release Drug Formulations in the USA: The Case of Opioid and Other Nervous System Drugs.

PubMed

Seoane-Vazquez, Enrique; Rodriguez-Monguio, Rosa; Hansen, Richard

2016-04-01

Modified-release drugs may provide clinical advantages compared to immediate-release forms and improve convenience to the patient and health outcomes. Concerns have been raised regarding interchangeability, efficacy, and safety of modified-release formulations. This study analyses all US Food and Drug Administration (FDA)-approved modified-release formulations and market trends, and illustrates how bioequivalence and safety of generic modified-release products compare to their respective brand name drugs and other generic drugs with different formulation design characteristics. This study also examines major concerns related to modified-release formulations: safety of opioids and bioequivalence of generic bupropion and methylphenidate. Study data were derived from the FDA electronic versions of the FDA's Orange Book (OB) and the FDA safety communications web page. Medicare Part D utilization and expenditures data were extracted from the Centers for Medicare and Medicaid. In May 2015, 276 (11.9 %) of the 2325 active ingredients and fixed-dose combinations listed in the FDA's Orange Book had at least one modified-release form approved by the FDA. The number of approvals increased over time; 52.5 % of modified releases were approved in the period 2000-May 2015. The FDA required a risk evaluation and mitigation strategy (REMS) to ensure that the benefits of extended-release opioids outweighed its risks of overdose and abuse. The REMS involved 16 new drug applications and 25 abbreviated new drug applications. The FDA addressed interchangeability problems with generic modified-release alternatives of bupropion and methylphenidate including lack of bioequivalence, reduced efficacy, and increased incidence of adverse events. Systematic post-marketing surveillance studies are needed to assess differences in safety, interchangeability, and efficacy of drugs with modified- and immediate-release formulations.

Inhibition of Comt with tolcapone slows progression of polycystic kidney disease in the more severely affected PKD/Mhm (cy/+) substrain of the Hannover Sprague-Dawley rat

PubMed Central

Boehn, Susanne N.E.; Spahn, Sonja; Neudecker, Sabine; Keppler, Andrea; Bihoreau, Marie-Thérèse; Kränzlin, Bettina; Pandey, Priyanka; Hoffmann, Sigrid C.; Li, Li; Torres, Vicente E.; Gröne, Hermann-Josef; Gretz, Norbert

2013-01-01

Background Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common human inherited diseases. Modifier genes seem to modulate the disease progression and might therefore be promising drug targets. Although a number of modifier loci have been already identified, no modifier gene has been proven to be a real modifier yet. Methods Gene expression profiling of two substrains of the Han:SPRD rat, namely PKD/Mhm and PKD/US, both harboring the same mutation, was conducted in 36-day-old animals. Catechol-O-methyltransferase (Comt) was identified as a potential modifier gene. A 3-month treatment with tolcapone, a selective inhibitor of Comt, was carried out in PKD/Mhm and PKD/US (cy/+) animals. Results Comt is localized within a known modifier locus of PKD (MOP2). The enzyme encoding gene was found upregulated in the more severely affected PKD/Mhm substrain and was hence presumed to be a putative modifier gene of PKD. The treatment with tolcapone markedly attenuated the loss of renal function, inhibited renal enlargement, shifted the size distribution of renal cysts and retarded cell proliferation, apoptosis, inflammation and fibrosis development in affected (cy/+) male and female PKD/Mhm and PKD/US rats. Conclusions Comt has been confirmed to be the first reported modifier gene for PKD and tolcapone offers a promising drug for treating PKD. PMID:23543593

Dietary starch intake modifies the relation between copy number variation in the salivary amylase gene and BMI.

PubMed

Rukh, Gull; Ericson, Ulrika; Andersson-Assarsson, Johanna; Orho-Melander, Marju; Sonestedt, Emily

2017-07-01

Background: Studies have shown conflicting associations between the salivary amylase gene ( AMY1 ) copy number and obesity. Salivary amylase initiates starch digestion in the oral cavity; starch is a major source of energy in the diet. Objective: We investigated the association between AMY1 copy number and obesity traits, and the effect of the interaction between AMY1 copy number and starch intake on these obesity traits. Design: We first assessed the association between AMY1 copy number (genotyped by digital droplet polymerase chain reaction) and obesity traits in 4800 individuals without diabetes (mean age: 57 y; 60% female) from the Malmö Diet and Cancer Cohort. Then we analyzed interactions between AMY1 copy number and energy-adjusted starch intake (obtained by a modified diet history method) on body mass index (BMI) and body fat percentage. Results: AMY1 copy number was not associated with BMI ( P = 0.80) or body fat percentage ( P = 0.38). We observed a significant effect of the interaction between AMY1 copy number and starch intake on BMI ( P -interaction = 0.007) and body fat percentage ( P -interaction = 0.03). Upon stratification by dietary starch intake, BMI tended to decrease with increasing AMY1 copy numbers in the low-starch intake group ( P = 0.07) and tended to increase with increasing AMY1 copy numbers in the high-starch intake group ( P = 0.08). The lowest mean BMI was observed in the group of participants with a low AMY1 copy number and a high dietary intake of starch. Conclusions: Our findings suggest an effect of the interaction between starch intake and AMY1 copy number on obesity. Individuals with high starch intake but low genetic capacity to digest starch had the lowest BMI, potentially because larger amounts of undigested starch are transported through the gastrointestinal tract, contributing to fewer calories extracted from ingested starch. © 2017 American Society for Nutrition.

Influence of a new surface modification of intraocular lenses with fluoroalkylsilan on the adherence of endophthalmitis-causing bacteria in vitro.

PubMed

Kienast, Antonia; Kämmerer, Regine; Weiss, Claudia; Klinger, Matthias; Menz, Dirk-Henning; Dresp, Joachim; Ohgke, Helge; Solbach, Werner; Laqua, Horst; Hoerauf, Hans

2006-09-01

Dynasilan is a fluoroalkylsilan that is able to interact with surface active centres on intraocular lenses (IOL), offering a new way for surface modification of different IOL materials. The purpose of this in vitro study was to investigate the influence of this new surface modification on the adherence of two typical endophthalmitis causing bacteria (Staphylococcus epidermidis, Propionibacterium acnes). In a pilot experiment, the effect of Dynasilan coating on the adherence of S. epidermidis was tested on glass slides. Forty-two Dynasilan-modified and 42 unmodified IOL (14 PMMA, 14 silicone and 14 hydrogel) were incubated at 37 degrees C in brain heart infusion broth (10(8) CFU/ml) with either S. epidermidis for 24 h or with P. acnes for 1 h. Subsequently, the adherent bacteria were resuspended using ultrasonification at 35 kHz for 3x45 s. After dilution series and incubation at 37 degrees C on Petri dishes for 24 h and 3 days, respectively, the colonies were counted. In the pilot experiment, a markedly lower number of adherent S. epidermidis was observed on Dynasilan-modified glass slides. Of all IOL materials incubated with S. epidermidis, those modified with Dynasilan showed a lower mean number of adherent bacteria (mean 1.37x10(7); SD 2.37x10(7)) than those untreated (2.43x10(7); SD 3.04x10(7)). IOLs incubated with P. acnes showed a significantly lower mean number of adherent bacteria of 2.51x10(4) (SD 2.71x10(4)) on Dynasilan-modified IOLs versus 6.27x10(4) (SD 7.70x10(4)) on untreated IOLs. The presented in vitro results indicate that Dynasilan surface modification is able to reduce the adherence of S. epidermidis and P. acnes on all IOL materials tested. Further studies regarding the stability of this modification and its biocompatibility must be performed.

Clinical efficacy of gene-modified stem cells in adenosine deaminase-deficient immunodeficiency.

PubMed

Shaw, Kit L; Garabedian, Elizabeth; Mishra, Suparna; Barman, Provaboti; Davila, Alejandra; Carbonaro, Denise; Shupien, Sally; Silvin, Christopher; Geiger, Sabine; Nowicki, Barbara; Smogorzewska, E Monika; Brown, Berkley; Wang, Xiaoyan; de Oliveira, Satiro; Choi, Yeong; Ikeda, Alan; Terrazas, Dayna; Fu, Pei-Yu; Yu, Allen; Fernandez, Beatriz Campo; Cooper, Aaron R; Engel, Barbara; Podsakoff, Greg; Balamurugan, Arumugam; Anderson, Stacie; Muul, Linda; Jagadeesh, G Jayashree; Kapoor, Neena; Tse, John; Moore, Theodore B; Purdy, Ken; Rishi, Radha; Mohan, Kathey; Skoda-Smith, Suzanne; Buchbinder, David; Abraham, Roshini S; Scharenberg, Andrew; Yang, Otto O; Cornetta, Kenneth; Gjertson, David; Hershfield, Michael; Sokolic, Rob; Candotti, Fabio; Kohn, Donald B

2017-05-01

Autologous hematopoietic stem cell transplantation (HSCT) of gene-modified cells is an alternative to enzyme replacement therapy (ERT) and allogeneic HSCT that has shown clinical benefit for adenosine deaminase-deficient (ADA-deficient) SCID when combined with reduced intensity conditioning (RIC) and ERT cessation. Clinical safety and therapeutic efficacy were evaluated in a phase II study. Ten subjects with confirmed ADA-deficient SCID and no available matched sibling or family donor were enrolled between 2009 and 2012 and received transplantation with autologous hematopoietic CD34+ cells that were modified with the human ADA cDNA (MND-ADA) γ-retroviral vector after conditioning with busulfan (90 mg/m2) and ERT cessation. Subjects were followed from 33 to 84 months at the time of data analysis. Safety of the procedure was assessed by recording the number of adverse events. Efficacy was assessed by measuring engraftment of gene-modified hematopoietic stem/progenitor cells, ADA gene expression, and immune reconstitution. With the exception of the oldest subject (15 years old at enrollment), all subjects remained off ERT with normalized peripheral blood mononuclear cell (PBMC) ADA activity, improved lymphocyte numbers, and normal proliferative responses to mitogens. Three of nine subjects were able to discontinue intravenous immunoglobulin replacement therapy. The MND-ADA vector was persistently detected in PBMCs (vector copy number [VCN] = 0.1-2.6) and granulocytes (VCN = 0.01-0.3) through the most recent visits at the time of this writing. No patient has developed a leukoproliferative disorder or other vector-related clinical complication since transplant. These results demonstrate clinical therapeutic efficacy from gene therapy for ADA-deficient SCID, with an excellent clinical safety profile. ClinicalTrials.gov NCT00794508. Food and Drug Administration Office of Orphan Product Development award, RO1 FD003005; NHLBI awards, PO1 HL73104 and Z01 HG000122; UCLA Clinical and Translational Science Institute awards, UL1RR033176 and UL1TR000124.

Clinical efficacy of gene-modified stem cells in adenosine deaminase–deficient immunodeficiency

PubMed Central

Shaw, Kit L.; Garabedian, Elizabeth; Mishra, Suparna; Barman, Provaboti; Davila, Alejandra; Carbonaro, Denise; Shupien, Sally; Silvin, Christopher; Geiger, Sabine; Nowicki, Barbara; Smogorzewska, E. Monika; Brown, Berkley; Wang, Xiaoyan; de Oliveira, Satiro; Choi, Yeong; Ikeda, Alan; Terrazas, Dayna; Fu, Pei-Yu; Yu, Allen; Fernandez, Beatriz Campo; Cooper, Aaron R.; Engel, Barbara; Podsakoff, Greg; Balamurugan, Arumugam; Anderson, Stacie; Muul, Linda; Jagadeesh, G. Jayashree; Kapoor, Neena; Tse, John; Moore, Theodore B.; Purdy, Ken; Rishi, Radha; Mohan, Kathey; Skoda-Smith, Suzanne; Buchbinder, David; Abraham, Roshini S.; Scharenberg, Andrew; Yang, Otto O.; Cornetta, Kenneth; Gjertson, David; Hershfield, Michael; Sokolic, Rob; Candotti, Fabio

2017-01-01

BACKGROUND. Autologous hematopoietic stem cell transplantation (HSCT) of gene-modified cells is an alternative to enzyme replacement therapy (ERT) and allogeneic HSCT that has shown clinical benefit for adenosine deaminase–deficient (ADA-deficient) SCID when combined with reduced intensity conditioning (RIC) and ERT cessation. Clinical safety and therapeutic efficacy were evaluated in a phase II study. METHODS. Ten subjects with confirmed ADA-deficient SCID and no available matched sibling or family donor were enrolled between 2009 and 2012 and received transplantation with autologous hematopoietic CD34+ cells that were modified with the human ADA cDNA (MND-ADA) γ-retroviral vector after conditioning with busulfan (90 mg/m2) and ERT cessation. Subjects were followed from 33 to 84 months at the time of data analysis. Safety of the procedure was assessed by recording the number of adverse events. Efficacy was assessed by measuring engraftment of gene-modified hematopoietic stem/progenitor cells, ADA gene expression, and immune reconstitution. RESULTS. With the exception of the oldest subject (15 years old at enrollment), all subjects remained off ERT with normalized peripheral blood mononuclear cell (PBMC) ADA activity, improved lymphocyte numbers, and normal proliferative responses to mitogens. Three of nine subjects were able to discontinue intravenous immunoglobulin replacement therapy. The MND-ADA vector was persistently detected in PBMCs (vector copy number [VCN] = 0.1–2.6) and granulocytes (VCN = 0.01–0.3) through the most recent visits at the time of this writing. No patient has developed a leukoproliferative disorder or other vector-related clinical complication since transplant. CONCLUSION. These results demonstrate clinical therapeutic efficacy from gene therapy for ADA-deficient SCID, with an excellent clinical safety profile. TRIAL REGISTRATION. ClinicalTrials.gov NCT00794508. FUNDING. Food and Drug Administration Office of Orphan Product Development award, RO1 FD003005; NHLBI awards, PO1 HL73104 and Z01 HG000122; UCLA Clinical and Translational Science Institute awards, UL1RR033176 and UL1TR000124. PMID:28346229

Neural networks: A simulation technique under uncertainty conditions

NASA Technical Reports Server (NTRS)

Mcallister, M. Luisa Nicosia

1992-01-01

This paper proposes a new definition of fuzzy graphs and shows how transmission through a graph with linguistic expressions as labels provides an easy computational tool. These labels are represented by modified Kauffmann Fuzzy numbers.

Modified method to improve the design of Petlyuk distillation columns.

PubMed

Zapiain-Salinas, Javier G; Barajas-Fernández, Juan; González-García, Raúl

2014-01-01

A response surface analysis was performed to study the effect of the composition and feeding thermal conditions of ternary mixtures on the number of theoretical stages and the energy consumption of Petlyuk columns. A modification of the pre-design algorithm was necessary for this purpose. The modified algorithm provided feasible results in 100% of the studied cases, compared with only 8.89% for the current algorithm. The proposed algorithm allowed us to attain the desired separations, despite the type of mixture and the operating conditions in the feed stream, something that was not possible with the traditional pre-design method. The results showed that the type of mixture had great influence on the number of stages and on energy consumption. A higher number of stages and a lower consumption of energy were attained with mixtures rich in the light component, while higher energy consumption occurred when the mixture was rich in the heavy component. The proposed strategy expands the search of an optimal design of Petlyuk columns within a feasible region, which allow us to find a feasible design that meets output specifications and low thermal loads.

Weather data for simplified energy calculation methods. Volume II. Middle United States: TRY data

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

Olsen, A.R.; Moreno, S.; Deringer, J.

1984-08-01

The objective of this report is to provide a source of weather data for direct use with a number of simplified energy calculation methods available today. Complete weather data for a number of cities in the United States are provided for use in the following methods: degree hour, modified degree hour, bin, modified bin, and variable degree day. This report contains sets of weather data for 22 cities in the continental United States using Test Reference Year (TRY) source weather data. The weather data at each city has been summarized in a number of ways to provide differing levels ofmore » detail necessary for alternative simplified energy calculation methods. Weather variables summarized include dry bulb and wet bulb temperature, percent relative humidity, humidity ratio, wind speed, percent possible sunshine, percent diffuse solar radiation, total solar radiation on horizontal and vertical surfaces, and solar heat gain through standard DSA glass. Monthly and annual summaries, in some cases by time of day, are available. These summaries are produced in a series of nine computer generated tables.« less

Experimental investigation of heat transfer coefficient of mini-channel PCHE (printed circuit heat exchanger)

NASA Astrophysics Data System (ADS)

Kwon, Dohoon; Jin, Lingxue; Jung, WooSeok; Jeong, Sangkwon

2018-06-01

Heat transfer coefficient of a mini-channel printed circuit heat exchanger (PCHE) with counter-flow configuration is investigated. The PCHE used in the experiments is two layered (10 channels per layer) and has the hydraulic diameter of 1.83 mm. Experiments are conducted under various cryogenic heat transfer conditions: single-phase, boiling and condensation heat transfer. Heat transfer coefficients of each experiments are presented and compared with established correlations. In the case of the single-phase experiment, empiricial correlation of modified Dittus-Boelter correlation was proposed, which predicts the experimental results with 5% error at Reynolds number range from 8500 to 17,000. In the case of the boiling experiment, film boiling phenomenon occurred dominantly due to large temperature difference between the hot side and the cold side fluids. Empirical correlation is proposed which predicts experimental results with 20% error at Reynolds number range from 2100 to 2500. In the case of the condensation experiment, empirical correlation of modified Akers correlation was proposed, which predicts experimental results with 10% error at Reynolds number range from 3100 to 6200.

Natural convection in a parallel-plate vertical channel with discrete heating by two flush-mounted heaters: effect of the clearance between the heaters

NASA Astrophysics Data System (ADS)

Sarper, Bugra; Saglam, Mehmet; Aydin, Orhan; Avci, Mete

2018-04-01

In this study, natural convection in a vertical channel is studied experimentally and numerically. One of the channel walls is heated discretely by two flush-mounted heaters while the other is insulated. The effects of the clearance between the heaters on heat transfer and hot spot temperature while total length of the heaters keeps constant are investigated. Four different settlements of two discrete heaters are comparatively examined. Air is used as the working fluid. The range of the modified Grashof number covers the values between 9.6 × 105 and 1.53 × 10.7 Surface to surface radiation is taken into account. Flow visualizations and temperature measurements are performed in the experimental study. Numerical computations are performed using the commercial CFD code ANSYS FLUENT. The results are represented as the variations of surface temperature, hot spot temperature and Nusselt number with the modified Grashof number and the clearance between the heaters as well as velocity and temperature variations of the fluid.

Decomposing Time Series Data by a Non-negative Matrix Factorization Algorithm with Temporally Constrained Coefficients

PubMed Central

Cheung, Vincent C. K.; Devarajan, Karthik; Severini, Giacomo; Turolla, Andrea; Bonato, Paolo

2017-01-01

The non-negative matrix factorization algorithm (NMF) decomposes a data matrix into a set of non-negative basis vectors, each scaled by a coefficient. In its original formulation, the NMF assumes the data samples and dimensions to be independently distributed, making it a less-than-ideal algorithm for the analysis of time series data with temporal correlations. Here, we seek to derive an NMF that accounts for temporal dependencies in the data by explicitly incorporating a very simple temporal constraint for the coefficients into the NMF update rules. We applied the modified algorithm to 2 multi-dimensional electromyographic data sets collected from the human upper-limb to identify muscle synergies. We found that because it reduced the number of free parameters in the model, our modified NMF made it possible to use the Akaike Information Criterion to objectively identify a model order (i.e., the number of muscle synergies composing the data) that is more functionally interpretable, and closer to the numbers previously determined using ad hoc measures. PMID:26737046

Is there a role for modified probiotics as beneficial microbes: a systematic review of the literature.

PubMed

Zorzela, L; Ardestani, S K; McFarland, L V; Vohra, S

2017-10-13

Our objective was to conduct a systematic review and meta-analysis for the use of modified (heat-killed or sonicated) probiotics for the efficacy and safety to prevent and treat various diseases. Recent clinical research has focused on living strains of probiotics, but use in high-risk patients and potential adverse reactions including bacteremia has focused interest on alternatives to the use of live probiotics. We searched MEDLINE/PubMed, Embase, Cochrane Central Register of Controlled Trials, CINAHL, Alt Health Watch, Web of Science, Scopus, PubMed, from inception to February 14, 2017 for randomised controlled trials involving modified probiotic strains. The primary outcome was efficacy to prevent or treat disease and the secondary outcome was incidence of adverse events. A total of 40 trials were included (n=3,913): 14 trials (15 arms with modified probiotics and 20 control arms) for the prevention of diseases and 26 trials (29 arms with modified probiotics and 32 control arms) for treatment of various diseases. Modified microbes were compared to either placebo (44%), or the same living probiotic strain (39%) or to only standard therapies (17%). Modified microbes were not significantly more or less effective than the living probiotic in 86% of the preventive trials and 69% of the treatment trials. Modified probiotic strains were significantly more effective in 15% of the treatment trials. Incidence rates of adverse events were similar for modified and living probiotics and other control groups, but many trials did not collect adequate safety data. Although several types of modified probiotics showed significant efficacy over living strains of probiotics, firm conclusions could not be reached due to the limited number of trials using the same type of modified microbe (strain, daily dose and duration) for a specific disease indication. Further research may illuminate other strains of modified probiotics that may have potential as clinical biotherapeutics.

Modified fluctuation-dissipation and Einstein relation at nonequilibrium steady states

NASA Astrophysics Data System (ADS)

Chaudhuri, Debasish; Chaudhuri, Abhishek

2012-02-01

Starting from the pioneering work of Agarwal [G. S. Agarwal, Zeitschrift für PhysikEPJAFV1434-600110.1007/BF01391621 252, 25 (1972)], we present a unified derivation of a number of modified fluctuation-dissipation relations (MFDR) that relate response to small perturbations around nonequilibrium steady states to steady-state correlations. Using this formalism we show the equivalence of velocity forms of MFDR derived using continuum Langevin and discrete master equation dynamics. The resulting additive correction to the Einstein relation is exemplified using a flashing ratchet model of molecular motors.

What do consumer surveys and experiments reveal and conceal about consumer preferences for genetically modified foods?

PubMed

Colson, Gregory; Rousu, Matthew C

2013-01-01

Assessing consumer perceptions and willingness to pay for genetically modified (GM) foods has been one of the most active areas of empirical research in agricultural economics. Researchers over the past 15 years have delivered well over 100 estimates of consumers' willingness to pay for GM foods using surveys and experimental methods. In this review, we explore a number of unresolved issues related to three questions that are critical when considering the sum of the individual contributions that constitute the evidence on consumer preferences for GM foods.

Pseudospin symmetry for modified Rosen-Morse potential including a Pekeris-type approximation to the pseudo-centrifugal term

NASA Astrophysics Data System (ADS)

Wei, Gao-Feng; Dong, Shi-Hai

2010-11-01

By applying a Pekeris-type approximation to the pseudo-centrifugal term, we study the pseudospin symmetry of a Dirac nucleon subjected to scalar and vector modified Rosen-Morse (MRM) potentials. A complicated quartic energy equation and spinor wave functions with arbitrary spin-orbit coupling quantum number k are presented. The pseudospin degeneracy is checked numerically. Pseudospin symmetry is discussed theoretically and numerically in the limit case α rightarrow 0 . It is found that the relativistic MRM potential cannot trap a Dirac nucleon in this limit.

A modified interval symmetric single step procedure ISS-5D for simultaneous inclusion of polynomial zeros

NASA Astrophysics Data System (ADS)

Sham, Atiyah W. M.; Monsi, Mansor; Hassan, Nasruddin; Suleiman, Mohamed

2013-04-01

The aim of this paper is to present a new modified interval symmetric single-step procedure ISS-5D which is the extension from the previous procedure, ISS1. The ISS-5D method will produce successively smaller intervals that are guaranteed to still contain the zeros. The efficiency of this method is measured on the CPU times and the number of iteration. The procedure is run on five test polynomials and the results obtained are shown in this paper.

Sum-frequency generation analyses of the structure of water at amphoteric SAM-liquid water interfaces.

PubMed

Nomura, Kouji; Nakaji-Hirabayashi, Tadashi; Gemmei-Ide, Makoto; Kitano, Hiromi; Noguchi, Hidenori; Uosaki, Kohei

2014-09-01

Surfaces of both a cover glass and the flat plane of a semi-cylindrical quartz prism were modified with a mixture of positively and negatively charged silane coupling reagents (3-aminopropyltriethoxysilane (APTES) and 3-(trihydroxysilyl)propylmethylphosphonate (THPMP), respectively). The glass surface modified with a self-assembled monolayer (SAM) prepared at a mixing ratio of APTES:THPMP=4:6 was electrically almost neutral and was resistant to non-specific adsorption of proteins, whereas fibroblasts gradually adhered to an amphoteric (mixed) SAM surface probably due to its stiffness, though the number of adhered cells was relatively small. Sum frequency generation (SFG) spectra indicated that total intensity of the OH stretching region (3000-3600cm(-1)) for the amphoteric SAM-modified quartz immersed in liquid water was smaller than those for the positively and negatively charged SAM-modified quartz prisms and a bare quartz prism in contact with liquid water. These results suggested that water molecules at the interface of water and an amphoteric SAM-modified quartz prism are not strongly oriented in comparison with those at the interface of a lopsidedly charged SAM-modified quartz prism and bare quartz. The importance of charge neutralization for the anti-biofouling properties of solid materials was strongly suggested. Copyright © 2014 Elsevier B.V. All rights reserved.

Cobalt Phthalocyanine Modified Electrodes Utilised in Electroanalysis: Nano-Structured Modified Electrodes vs. Bulk Modified Screen-Printed Electrodes

PubMed Central

Foster, Christopher W.; Pillay, Jeseelan; Metters, Jonathan P.; Banks, Craig E.

2014-01-01

Cobalt phthalocyanine (CoPC) compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC) onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes l-ascorbic acid, oxygen and hydrazine. It is found that no “electrocatalysis” is observed towards l-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where “electrocatalysis” has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate. PMID:25414969

Macrophage phenotype in the epigallocatechin-3-gallate (EGCG)-modified collagen determines foreign body reaction.

PubMed

Chu, Chenyu; Liu, Li; Wang, Yufei; Wei, Shimin; Wang, Yuanjing; Man, Yi; Qu, Yili

2018-04-28

Collagen has been widely used in guided bone regeneration, and the implantation of collagen membranes will elicit the foreign body reaction (FBR). The imbalance of FBR often leads to failure of dental implants. Therefore, modulation of the FBR after implantation of collagen membranes becomes increasingly important. Macrophages, pivotal in FBR, have been distinguished into pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. Epigallocatechin-3-gallate (EGCG)-modified collagen membranes have been previously shown to regulate secretion of inflammatory factors. In this study, immunohistochemistry of CD31 showed that areas of blood vessels were significantly enlarged after implantation of EGCG-modified collagen membranes compared with those treated with pure collagen membranes. Besides, haematoxylin-eosin staining and immunofluorescence showed an increased number of M2 macrophages after implantation of EGCG-modified collagen membranes. In addition, quantitative real-time polymerase chain reaction showed that after implantation of EGCG-modified collagen membranes, expression of CXCL1 (predominant chemoattractants to neutrophils and inflammation promotors) was significantly downregulated, whereas expressions of STAB1, CCR2, CCR3, CCL2, and CCL3 (related to M2 macrophages) were significantly upregulated. From these findings, we conclude that EGCG-modified collagen membranes were able to regulate the recruitment and polarization of macrophages, so that ameliorate FBR. Copyright © 2018 John Wiley & Sons, Ltd.

Cancer immunotherapy in children

Cancer.gov

More often than not, cancer immunotherapies that work in adults are used in modified ways in children. Seldom are new therapies developed just for children, primarily because of the small number of pediatric patients relative to the adult cancer patient

Modified current follower-based immittance function simulators

NASA Astrophysics Data System (ADS)

Alpaslan, Halil; Yuce, Erkan

2017-12-01

In this paper, four immittance function simulators consisting of a single modified current follower with single Z- terminal and a minimum number of passive components are proposed. The first proposed circuit can provide +L parallel with +R and the second proposed one can realise -L parallel with -R. The third proposed structure can provide +L series with +R and the fourth proposed one can realise -L series with -R. However, all the proposed immittance function simulators need a single resistive matching constraint. Parasitic impedance effects on all the proposed immittance function simulators are investigated. A second-order current-mode (CM) high-pass filter derived from the first proposed immittance function simulator is given as an application example. Also, a second-order CM low-pass filter derived from the third proposed immittance function simulator is given as an application example. A number of simulation results based on SPICE programme and an experimental test result are given to verify the theory.