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Sample records for modified redfield simulations

  1. A general approach to the electronic spin relaxation of Gd(III) complexes in solutions. Monte Carlo simulations beyond the Redfield limit

    NASA Astrophysics Data System (ADS)

    Rast, S.; Fries, P. H.; Belorizky, E.; Borel, A.; Helm, L.; Merbach, A. E.

    2001-10-01

    The time correlation functions of the electronic spin components of a metal ion without orbital degeneracy in solution are computed. The approach is based on the numerical solution of the time-dependent Schrödinger equation for a stochastic perturbing Hamiltonian which is simulated by a Monte Carlo algorithm using discrete time steps. The perturbing Hamiltonian is quite general, including the superposition of both the static mean crystal field contribution in the molecular frame and the usual transient ligand field term. The Hamiltonian of the static crystal field can involve the terms of all orders, which are invariant under the local group of the average geometry of the complex. In the laboratory frame, the random rotation of the complex is the only source of modulation of this Hamiltonian, whereas an additional Ornstein-Uhlenbeck process is needed to describe the time fluctuations of the Hamiltonian of the transient crystal field. A numerical procedure for computing the electronic paramagnetic resonance (EPR) spectra is proposed and discussed. For the [Gd(H2O)8]3+ octa-aqua ion and the [Gd(DOTA)(H2O)]- complex [DOTA=1,4,7,10-tetrakis(carboxymethyl)-1,4,7,10-tetraazacyclo dodecane] in water, the predictions of the Redfield relaxation theory are compared with those of the Monte Carlo approach. The Redfield approximation is shown to be accurate for all temperatures and for electronic resonance frequencies at and above X-band, justifying the previous interpretations of EPR spectra. At lower frequencies the transverse and longitudinal relaxation functions derived from the Redfield approximation display significantly faster decays than the corresponding simulated functions. The practical interest of this simulation approach is underlined.

  2. Spectral Trends in the Fluorescence of Single Bacterial Light-Harvesting Complexes: Experiments and Modified Redfield Simulations

    PubMed Central

    Rutkauskas, Danielis; Novoderezhkin, Vladimir; Gall, Andrew; Olsen, John; Cogdell, Richard J.; Hunter, C. Neil; van Grondelle, Rienk

    2006-01-01

    In this work we present and discuss the single-molecule fluorescence spectra of a variety of species of light-harvesting complexes: LH2 of Rhodopseudomonas acidophila, Rhodobacter sphaeroides, and Rhodospirillum molischianum and LH1 of Rhodobacter sphaeroides. The emission spectrum of these complexes varies as a function of time as was described in earlier work. For each type of complex, we observe a pronounced and well-reproducible characteristic relationship between the fluorescence spectral parameters of the peak wavelength, width, and asymmetry. This dependence for the LH2 complexes can be quantitatively explained on the basis of a disordered exciton model by varying the static disorder and phonon coupling parameters. In addition, a correlation of the pigment site energies has to be assumed to interpret the behavior of the LH1 complex. PMID:16399834

  3. Time-dependent renormalized Redfield theory II for off-diagonal transition in reduced density matrix

    NASA Astrophysics Data System (ADS)

    Kimura, Akihiro

    2016-09-01

    In our previous letter (Kimura, 2016), we constructed time-dependent renormalized Redfield theory (TRRT) only for diagonal transition in a reduced density matrix. In this letter, we formulate the general expression for off-diagonal transition in the reduced density matrix. We discuss the applicability of TRRT by numerically comparing the dependencies on the energy gap of the exciton relaxation rate by using the TRRT and the modified Redfield theory (MRT). In particular, we roughly show that TRRT improves MRT for the detailed balance about the excitation energy transfer reaction.

  4. Temporal trends in deep ocean Redfield ratios.

    PubMed

    Pahlow, M; Riebesell, U

    2000-02-01

    The Redfield ratio [carbon:nitrogen:phosphorus (C:N:P)] of particle flux to the deep ocean is a key factor in marine biogeochemical cycling. Changes in oceanic carbon sequestration have been linked to variations in the Redfield ratio on geological time scales, but this ratio generally is assumed to be constant with time in the modern ocean. However, deep-water Redfield ratios in the northern hemisphere show evidence for temporal trends over the past five decades. The North Atlantic Ocean exhibits a rising N:P ratio, which may be related to increased deposition of atmospheric nitrous oxides from anthropogenic N emissions. In the North Pacific Ocean, increasing C:N and C:P ratios are accompanied by rising remineralization rates, which suggests intensified export production. Stronger export of carbon in this region may be due to enhanced bioavailability of aeolian iron. These findings imply that the biological part of the marine carbon cycle currently is not in steady state. PMID:10657291

  5. Iron in the Ross Sea: 1. Impact on CO2 fluxes via variation in phytoplankton functional group and non-Redfield stoichiometry

    NASA Astrophysics Data System (ADS)

    Tagliabue, Alessandro; Arrigo, Kevin R.

    2005-03-01

    We present new model results examining nutrient and carbon biogeochemistry within the Ross Sea, focusing on the sensitivity of ecosystem dynamics to taxon-specific nutrient utilization parameters and the impact of alleviating Fe limitation of phytoplankton growth. The coupled ice-atmosphere-ocean ecosystem (CIAO) model of the Ross Sea was modified to include air-sea CO2 exchange and non-Redfield C/N/P uptake ratios of the dominant phytoplankton taxa. Model results show that the Ross Sea was a substantial sink for atmospheric CO2, driven by the high primary productivity prior to the onset of Fe limitation. Taxon-specific C/N/P uptake ratios controlled the relative rate of removal of each macronutrient, while Fe availability constrained the absolute magnitude of utilization. When Redfield C/N/P stoichiometry was applied to both phytoplankton taxa, net primary production (NPP) was overestimated in areas normally dominated by diatoms and underestimated in regions of Phaeocystis antarctica dominance, and macronutrient dynamics were misrepresented. Simulated shifts in phytoplankton taxonomic composition significantly altered uptake of atmospheric CO2 when the phytoplankton were dominated by diatoms (-70%) or P. antarctica (+35%). The ability to bloom later in the season afforded P. antarctica a relatively greater role than diatoms in controlling the air-sea flux of CO2 in the Ross Sea. In response to alleviation of Fe limitation, both total Ross Sea NPP and CO2 uptake increased by 30%. The response of the carbon cycle to Fe fertilization was predicted to be complex, and its magnitude and nature were dictated by patterns of macronutrient utilization.

  6. Bloch-Redfield equations for modeling light-harvesting complexes.

    PubMed

    Jeske, Jan; Ing, David J; Plenio, Martin B; Huelga, Susana F; Cole, Jared H

    2015-02-14

    We challenge the misconception that Bloch-Redfield equations are a less powerful tool than phenomenological Lindblad equations for modeling exciton transport in photosynthetic complexes. This view predominantly originates from an indiscriminate use of the secular approximation. We provide a detailed description of how to model both coherent oscillations and several types of noise, giving explicit examples. All issues with non-positivity are overcome by a consistent straightforward physical noise model. Herein also lies the strength of the Bloch-Redfield approach because it facilitates the analysis of noise-effects by linking them back to physical parameters of the noise environment. This includes temporal and spatial correlations and the strength and type of interaction between the noise and the system of interest. Finally, we analyze a prototypical dimer system as well as a 7-site Fenna-Matthews-Olson complex in regards to spatial correlation length of the noise, noise strength, temperature, and their connection to the transfer time and transfer probability.

  7. Regulation of Redfield ratios in the deep ocean

    NASA Astrophysics Data System (ADS)

    Auguères, Anne-Sophie; Loreau, Michel

    2015-02-01

    Biotic regulation of the environment at global scales has been debated for several decades. An example is the similarity between deep-ocean and phytoplankton mean N:P ratios. N and P cycles are heavily altered by human activities, mainly through an increase in nutrient supply to the upper ocean. As phytoplankton only access nutrients in the upper ocean, it is critical to understand (1) to what extent phytoplankton are able to regulate N and P concentrations as well as their ratio in the deep, inaccessible layer and (2) what mechanisms control the value of the deepwater N:P ratio and the efficiency of its biotic regulation. With a model of N and P cycles in the global ocean separated in two layers, we show that the value of the deepwater N:P ratio is determined by nonfixer's N:P ratio, recycling, and denitrification. Our model predicts that although phytoplankton cannot efficiently regulate deep nutrient pools, they can maintain nearly constant ratios between nutrients because compensatory dynamics between nonfixers and nitrogen fixers allows a control of deepwater chemistry through nutrient recycling. This mechanism could explain the near constancy of the deepwater N:P ratio, in agreement with Redfield's (1934, 1958) classical hypothesis. Surprisingly, N:P ratio of phytoplankton does not affect their ability to regulate the deepwater N:P ratio. Our model suggests that increased water column stratification as a result of global climate change may decrease the stability of the N:P ratio in the deep ocean over long temporal and spatial scales.

  8. Preferential remineralization of dissolved organic phosphorus and non-Redfield DOM dynamics in the global ocean: Impacts on marine productivity, nitrogen fixation, and carbon export

    NASA Astrophysics Data System (ADS)

    Letscher, Robert T.; Moore, J. Keith

    2015-03-01

    Selective removal of nitrogen (N) and phosphorus (P) from the marine dissolved organic matter (DOM) pool has been reported in several regional studies. Because DOM is an important advective/mixing pathway of carbon (C) export from the ocean surface layer and its non-Redfieldian stoichiometry would affect estimates of marine export production per unit N and P, we investigated the stoichiometry of marine DOM and its remineralization globally using a compiled DOM data set. Marine DOM is enriched in C and N compared to Redfield stoichiometry, averaging 317:39:1 and 810:48:1 for C:N:P within the degradable and total bulk pools, respectively. Dissolved organic phosphorus (DOP) is found to be preferentially remineralized about twice as rapidly with respect to the enriched C:N stoichiometry of marine DOM. Biogeochemical simulations with the Biogeochemical Elemental Cycling model using Redfield and variable DOM stoichiometry corroborate the need for non-Redfield dynamics to match the observed DOM stoichiometry. From our model simulations, preferential DOP remineralization is found to increase the strength of the biological pump by ~9% versus the case of Redfield DOM cycling. Global net primary productivity increases ~10% including an increase in marine nitrogen fixation of ~26% when preferential DOP remineralization and direct utilization of DOP by phytoplankton are included. The largest increases in marine nitrogen fixation, net primary productivity, and carbon export are observed within the western subtropical gyres, suggesting the lateral transfer of P in the form of DOP from the productive eastern and poleward gyre margins may be important for sustaining these processes downstream in the subtropical gyres.

  9. On the influence of "non-Redfield" dissolved organic nutrient dynamics on the spatial distribution of N2 fixation and the size of the marine fixed nitrogen inventory

    NASA Astrophysics Data System (ADS)

    Somes, Christopher J.; Oschlies, Andreas

    2015-07-01

    Dissolved organic nitrogen (DON) and phosphorus (DOP) represent the most abundant form of their respective nutrient pool in the surface layer of the oligotrophic oceans and play an important role in nutrient cycling and productivity. Since DOP is generally more labile than DON, it provides additional P that may stimulate growth of nitrogen-fixing diazotrophs that supply fixed nitrogen to balance denitrification in the ocean. In this study, we introduce semirecalcitrant components of DON and DOP as state variables in an existing global ocean-atmosphere-sea ice-biogeochemistry model of intermediate complexity to assess their impact on the spatial distribution of nitrogen fixation and the size of the marine fixed nitrogen inventory. Large-scale surface data sets of global DON and Atlantic Ocean DOP are used to constrain the model. Our simulations suggest that both preferential DOP remineralization and phytoplankton DOP uptake are important "non-Redfield" processes (i.e., deviate from molar N:P = 16) that need to be accounted for to explain the observed patterns of DOP. Additional non-Redfield DOP sensitivity experiments testing dissolved organic matter (DOM) production rate uncertainties that best reproduce the observed spatial patterns of DON and DOP stimulate additional nitrogen fixation that increases the size of the global marine fixed nitrogen inventory by 4.7 ± 1.7% compared to the simulation assuming Redfield DOM stoichiometry that underestimates the observed nitrogen inventory. The extra 8 Tg yr-1 of nitrogen fixation stimulated in the Atlantic Ocean is mainly responsible for this increase due to its large spatial separation from water column denitrification, which buffers any potential nitrogen surplus in the Pacific Ocean. Our study suggests that the marine fixed nitrogen budget is sensitive to non-Redfield DOP dynamics because access to the relatively labile DOP pool expands the ecological niche for nitrogen-fixing diazotrophs.

  10. GenAnneal: Genetically modified Simulated Annealing

    NASA Astrophysics Data System (ADS)

    Tsoulos, Ioannis G.; Lagaris, Isaac E.

    2006-05-01

    A modification of the standard Simulated Annealing (SA) algorithm is presented for finding the global minimum of a continuous multidimensional, multimodal function. We report results of computational experiments with a set of test functions and we compare to methods of similar structure. The accompanying software accepts objective functions coded both in Fortran 77 and C++. Program summaryTitle of program:GenAnneal Catalogue identifier:ADXI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXI_v1_0 Program available from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: The tool is designed to be portable in all systems running the GNU C++ compiler Installation: University of Ioannina, Greece on Linux based machines Programming language used:GNU-C++, GNU-C, GNU Fortran 77 Memory required to execute with typical data: 200 KB No. of bits in a word: 32 No. of processors used: 1 Has the code been vectorized or parallelized?: No No. of bytes in distributed program, including test data, etc.:84 885 No. of lines in distributed program, including test data, etc.:14 896 Distribution format: tar.gz Nature of physical problem: A multitude of problems in science and engineering are often reduced to minimizing a function of many variables. There are instances that a local optimum does not correspond to the desired physical solution and hence the search for a better solution is required. Local optimization techniques are frequently trapped in local minima. Global optimization is hence the appropriate tool. For example, solving a non-linear system of equations via optimization, employing a "least squares" type of objective, one may encounter many local minima that do not correspond to solutions (i.e. they are far from zero). Typical running time: Depending on the objective function. Method of solution: We modified the process of step selection that the traditional Simulated

  11. Extending the applicability of Redfield theories into highly non-Markovian regimes

    SciTech Connect

    Montoya-Castillo, Andrés; Reichman, David R.; Berkelbach, Timothy C.

    2015-11-21

    We present a new, computationally inexpensive method for the calculation of reduced density matrix dynamics for systems with a potentially large number of subsystem degrees of freedom coupled to a generic bath. The approach consists of propagation of weak-coupling Redfield-like equations for the high-frequency bath degrees of freedom only, while the low-frequency bath modes are dynamically arrested but statistically sampled. We examine the improvements afforded by this approximation by comparing with exact results for the spin-boson model over a wide range of parameter space. We further generalize the method to multi-site models and compare with exact results for a model of the Fenna–Matthews–Olson complex. The results from the method are found to dramatically improve Redfield dynamics in highly non-Markovian regimes, at a similar computational cost. Relaxation of the mode-freezing approximation via classical (Ehrenfest) evolution of the low-frequency modes results in a dynamical hybrid method. We find that this Redfield-based dynamical hybrid approach, which is computationally more expensive than bare Redfield dynamics, yields only a marginal improvement over the simpler approximation of complete mode arrest.

  12. Extending the applicability of Redfield theories into highly non-Markovian regimes

    NASA Astrophysics Data System (ADS)

    Montoya-Castillo, Andrés; Berkelbach, Timothy C.; Reichman, David R.

    2015-11-01

    We present a new, computationally inexpensive method for the calculation of reduced density matrix dynamics for systems with a potentially large number of subsystem degrees of freedom coupled to a generic bath. The approach consists of propagation of weak-coupling Redfield-like equations for the high-frequency bath degrees of freedom only, while the low-frequency bath modes are dynamically arrested but statistically sampled. We examine the improvements afforded by this approximation by comparing with exact results for the spin-boson model over a wide range of parameter space. We further generalize the method to multi-site models and compare with exact results for a model of the Fenna-Matthews-Olson complex. The results from the method are found to dramatically improve Redfield dynamics in highly non-Markovian regimes, at a similar computational cost. Relaxation of the mode-freezing approximation via classical (Ehrenfest) evolution of the low-frequency modes results in a dynamical hybrid method. We find that this Redfield-based dynamical hybrid approach, which is computationally more expensive than bare Redfield dynamics, yields only a marginal improvement over the simpler approximation of complete mode arrest.

  13. Surface hopping outperforms secular Redfield theory when reorganization energies range from small to moderate (and nuclei are classical)

    SciTech Connect

    Landry, Brian R. Subotnik, Joseph E.

    2015-03-14

    We evaluate the accuracy of Tully’s surface hopping algorithm for the spin-boson model in the limit of small to moderate reorganization energy. We calculate transition rates between diabatic surfaces in the exciton basis and compare against exact results from the hierarchical equations of motion; we also compare against approximate rates from the secular Redfield equation and Ehrenfest dynamics. We show that decoherence-corrected surface hopping performs very well in this regime, agreeing with secular Redfield theory for very weak system-bath coupling and outperforming secular Redfield theory for moderate system-bath coupling. Surface hopping can also be extended beyond the Markovian limits of standard Redfield theory. Given previous work [B. R. Landry and J. E. Subotnik, J. Chem. Phys. 137, 22A513 (2012)] that establishes the accuracy of decoherence-corrected surface-hopping in the Marcus regime, this work suggests that surface hopping may well have a very wide range of applicability.

  14. Systematic simulations of modified gravity: symmetron and dilaton models

    SciTech Connect

    Brax, Philippe; Li, Baojiu; Winther, Hans A.; Zhao, Gong-Bo E-mail: a.c.davis@damtp.cam.ac.uk E-mail: h.a.winther@astro.uio.no

    2012-10-01

    We study the linear and nonlinear structure formation in the dilaton and symmetron models of modified gravity using a generic parameterisation which describes a large class of scenarios using only a few parameters, such as the coupling between the scalar field and the matter, and the range of the scalar force on very large scales. For this we have modified the N-body simulation code ECOSMOG, which is a variant of RAMSES working in modified gravity scenarios, to perform a set of 110 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a large portion of the parameter space. We have studied the effects of modified gravity on the matter power spectrum and mass function, and found a rich and interesting phenomenology where the difference with the ΛCDM template cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc{sup −1}. Our results show the full effect of screening on nonlinear structure formation and the associated deviation from ΛCDM. We also investigate how differences in the force mediated by the scalar field in modified gravity models lead to qualitatively different features for the nonlinear power spectrum and the halo mass function, and how varying the individual model parameters changes these observables. The differences are particularly large in the nonlinear power spectra whose shapes for f(R), dilaton and symmetron models vary greatly, and where the characteristic bump around 1 hMpc{sup −1} of f(R) models is preserved for symmetrons, whereas an increase on much smaller scales is particular to symmetrons. No bump is present for dilatons where a flattening of the power spectrum takes place on small scales. These deviations from ΛCDM and the differences between modified gravity models, such as dilatons and symmetrons, could be tested with future surveys.

  15. Partial secular Bloch-Redfield master equation for incoherent excitation of multilevel quantum systems

    SciTech Connect

    Tscherbul, Timur V. Brumer, Paul

    2015-03-14

    We present an efficient theoretical method for calculating the time evolution of the density matrix of a multilevel quantum system weakly interacting with incoherent light. The method combines the Bloch-Redfield theory with a partial secular approximation for one-photon coherences, resulting in a master equation that explicitly exposes the reliance on transition rates and the angles between transition dipole moments in the energy basis. The partial secular Bloch-Redfield master equation allows an unambiguous distinction between the regimes of quantum coherent vs. incoherent energy transfer under incoherent light illumination. The fully incoherent regime is characterized by orthogonal transition dipole moments in the energy basis, leading to a dynamical evolution governed by a coherence-free Pauli-type master equation. The coherent regime requires non-orthogonal transition dipole moments in the energy basis and leads to the generation of noise-induced quantum coherences and population-to-coherence couplings. As a first application, we consider the dynamics of excited state coherences arising under incoherent light excitation from a single ground state and observe population-to-coherence transfer and the formation of non-equilibrium quasisteady states in the regime of small excited state splitting. Analytical expressions derived earlier for the V-type system [T. V. Tscherbul and P. Brumer, Phys. Rev. Lett. 113, 113601 (2014)] are found to provide a nearly quantitative description of multilevel excited-state populations and coherences in both the small- and large-molecule limits.

  16. Numeric Modified Adomian Decomposition Method for Power System Simulations

    SciTech Connect

    Dimitrovski, Aleksandar D; Simunovic, Srdjan; Pannala, Sreekanth

    2016-01-01

    This paper investigates the applicability of numeric Wazwaz El Sayed modified Adomian Decomposition Method (WES-ADM) for time domain simulation of power systems. WESADM is a numerical method based on a modified Adomian decomposition (ADM) technique. WES-ADM is a numerical approximation method for the solution of nonlinear ordinary differential equations. The non-linear terms in the differential equations are approximated using Adomian polynomials. In this paper WES-ADM is applied to time domain simulations of multimachine power systems. WECC 3-generator, 9-bus system and IEEE 10-generator, 39-bus system have been used to test the applicability of the approach. Several fault scenarios have been tested. It has been found that the proposed approach is faster than the trapezoidal method with comparable accuracy.

  17. Formulation and make-up of simulated cement modified water

    SciTech Connect

    Gdowski, G.

    1997-09-12

    This procedure describes the formulation and make-up of Simulated Cement-Modified Waters (SCMW), which are aqueous solutions to be used for Activity E-20-50 Long-Term Corrosion Studies. These solutions simulate the changes to representative Yucca Mountain water chemistry because of prolonged contact with aged cement. The representative water was chosen as J-13 well water [Harrar, 1990]. J-13 well water is obtained from ground water that is in contact with the Topopah Spring tuff, which is the repository horizon rock.

  18. Modified-Gravity-GADGET: a new code for cosmological hydrodynamical simulations of modified gravity models

    NASA Astrophysics Data System (ADS)

    Puchwein, Ewald; Baldi, Marco; Springel, Volker

    2013-11-01

    We present a new massively parallel code for N-body and cosmological hydrodynamical simulations of modified gravity models. The code employs a multigrid-accelerated Newton-Gauss-Seidel relaxation solver on an adaptive mesh to efficiently solve for perturbations in the scalar degree of freedom of the modified gravity model. As this new algorithm is implemented as a module for the P-GADGET3 code, it can at the same time follow the baryonic physics included in P-GADGET3, such as hydrodynamics, radiative cooling and star formation. We demonstrate that the code works reliably by applying it to simple test problems that can be solved analytically, as well as by comparing cosmological simulations to results from the literature. Using the new code, we perform the first non-radiative and radiative cosmological hydrodynamical simulations of an f (R)-gravity model. We also discuss the impact of active galactic nucleus feedback on the matter power spectrum, as well as degeneracies between the influence of baryonic processes and modifications of gravity.

  19. Bloch-Redfield-Wangsness theory engine implementation using symbolic processing software.

    PubMed

    Kuprov, Ilya; Wagner-Rundell, Nicola; Hore, P J

    2007-02-01

    We describe a general method for the automated symbolic processing of Bloch-Redfield-Wangsness relaxation theory equations for liquid-phase spin dynamics in the algebraically challenging case of rotationally modulated interactions. The processing typically takes no more than a few seconds (on a contemporary single-processor workstation) and yields relaxation rate expressions that are completely general with respect to the spectral density functions, relative orientations, and magnitudes of the interaction tensors, with all cross-correlations accounted for. The algorithm easily deals with fully rhombic interaction tensors, and is able, with little if any modification, to treat a large variety of the relaxation mechanisms encountered in NMR, EPR, and spin dynamics in general.

  20. Monte Carlo simulations of sexual reproduction

    NASA Astrophysics Data System (ADS)

    Stauffer, D.; de Oliveira, P. M. C.; de Oliveira, S. Moss; dos Santos, R. M. Zorzenon

    1996-02-01

    Modifying the Redfield model of sexual reproduction and the Penna model of biological aging, we compare reproduction with and without recombination in age-structured populations. In constrast to Redfield and in agreement with Bernardes we find sexual reproduction to be preferred to asexual one. In particular, the presence of old but still reproducing males helps the survival of younger females beyond their reproductive age.

  1. Modified point mass trajectory simulation for base-burn projectiles

    NASA Astrophysics Data System (ADS)

    Lieske, R. F.; Danberg, J. E.

    1992-03-01

    An addition to the Modified Point Mass Trajectory Model for Rocket-Assisted Projectiles is presented for the exterior ballistic simulation of base-burn projectiles. The addition models the change in aerodynamic base-drag based on the change in base pressure due to the base-burn motor's ejection of hot gas into the wake of the projectile. The mass flow rate of the remaining fuel of the base-burn motor is modeled as a function of the instantaneous projectile spin rate and atmospheric air pressure. HAWK Doppler radar data collected at Yuma Proving Ground, Arizona, for the 155mm, M1864 base-burn projectile were used to verify the modeling approach for a variety of test conditions.

  2. Reexamination of relaxation of spins due to a magnetic field gradient: Identity of the Redfield and Torrey theories

    NASA Astrophysics Data System (ADS)

    Golub, R.; Rohm, Ryan M.; Swank, C. M.

    2011-02-01

    There is an extensive literature on magnetic-gradient-induced spin relaxation. Cates, Schaefer, and Happer, in a seminal publication, have solved the problem in the regime where diffusion theory (the Torrey equation) is applicable using an expansion of the density matrix in diffusion equation eigenfunctions and angular momentum tensors. McGregor has solved the problem in the same regime using a slightly more general formulation using the Redfield theory formulated in terms of the autocorrelation function of the fluctuating field seen by the spins and calculating the correlation functions using the diffusion-theory Green’s function. The results of both calculations were shown to agree for a special case. In the present work, we show that the eigenfunction expansion of the Torrey equation yields the expansion of the Green’s function for the diffusion equation, thus showing the identity of this approach with that of the Redfield theory. The general solution can also be obtained directly from the Torrey equation for the density matrix. Thus, the physical content of the Redfield and Torrey approaches are identical. We then introduce a more general expression for the position autocorrelation function of particles moving in a closed cell, extending the range of applicability of the theory.

  3. Does Simulated Spaceflight Modify Epigenetic Status During Bone Remodeling?

    NASA Technical Reports Server (NTRS)

    Thomas, Nicholas J.; Stevick, Rebecca J.; Tran, Luan H.; Nalavadi, Mohit O.; Almeida, Eduardo A.C.; Globus, Ruth K.; Alwood, Joshua S.

    2015-01-01

    Little is known about the effects of spaceflight conditions on epigenetics. The term epigenetics describes changes to the genome that can affect expression of a gene without changes to the sequence of DNA. Epigenetic processes are thought to underlie cellular differentiation, where transcription of specific genes occurs in response to key stimuli, and may be heritable - passing from one cell to its daughter cell. We hypothesize that the mechanical environment during spaceflight, namely microgravity-induced weightlessness or exercise regulate gene expression in the osteoblast-lineage cells both to control bone formation by osteoblasts and bone resorption by osteoclasts, which continually shapes bone structure throughout life. Similarly we intend to evaluate how radiation regulates these same bone cell activity and differentiation related genes. We further hypothesize that the regulation in bone cell gene expression is at least partially controlled through epigenetic mechanisms of methylation or small non-coding RNA (microRNAs). We have acquired preliminary data suggesting that global genome methylation is modified in response to axial compression of the tibia - a model of exercise. We intend to pursue these hypotheses wherein we will evaluate changes in gene expression and, congruently, changes in epigenetic state in bones from mice subjected to the aforementioned conditions: hindlimb unloading to simulate weightlessness, axial compression of the tibia, or radiation exposure in order to gain insight into the role of epigenetics in spaceflight-induced bone loss.

  4. A modified method of characteristics and its application in forward and inversion simulations of underwater explosion

    NASA Astrophysics Data System (ADS)

    Zhang, Chengjiao; Li, Xiaojie; Yang, Chenchen

    2016-07-01

    This paper introduces a modified method of characteristics and its application in forward and inversion simulations of underwater explosion. Compared with standard method of characteristics which is appropriate to homoentripic flow problem, the modified method can be also used to deal with isentropic flow problem such as underwater explosion. Underwater explosion of spherical TNT and composition B explosives are simulated by using the modified method, respectively. Peak pressures and flow field pressures are obtained, and they are coincident with those from empirical formulas. The comparison demonstrates the modified is feasible and reliable in underwater explosion simulation. Based on the modified method, inverse difference schemes and inverse method are introduced. Combined with the modified, the inverse schemes can be used to deal with gas-water interface inversion of underwater explosion. Inversion simulations of underwater explosion of the explosives are performed in water, and equation of state (EOS) of detonation product is not needed. The peak pressures from the forward simulations are provided as boundary conditions in the inversion simulations. Inversion interfaces are obtained and they are mainly in good agreement with those from the forward simulations in near field. The comparison indicates the inverse method and the inverse difference schemes are reliable and reasonable in interface inversion simulation.

  5. Transmission of a Viral Disease (AIDS) Detected by a Modified ELISA Reaction: A Laboratory Simulation.

    ERIC Educational Resources Information Center

    Grimes, William J.; Chambers, Linda; Kubo, Kenneth M.; Narro, Martha L.

    1998-01-01

    Describes a laboratory exercise that simulates the spread of an infectious agent among students in a classroom. Uses a modified Enzyme Linked ImmunoSorbent Assay (ELISA) to provide students with experience using an authentic diagnostic tool for detecting human infections. (DDR)

  6. DETECTORS AND EXPERIMENTAL METHODS: Simulation of a modified neutron detector applied in CSNS

    NASA Astrophysics Data System (ADS)

    Ma, Zhong-Jian; Wang, Qing-Bin; Wu, Qing-Biao

    2009-01-01

    We simulate the response of a modified Anderson-Braun rem counter in the energy range from thermal energy to about 10 GeV using the FLUKA code. Also, we simulate the lethargy spectrum of CSNS outside the beam dump. Traditional BF3 tube is replaced by the 3He tube, a layer of 0.6 cm lead is added outside the boron doped plastic attenuator and a sphere configuration is adopted. The simulation result shows that its response is exactly fit to H*(10) in the neutron energies between 10 keV and approximately 1 GeV, although the monitor slightly underestimates H*(10) in the energy range from thermal energy to about 10 keV. According to the characteristics of the CSNS, this modified counter increases the neutron energy response by 30% compared with the traditional monitors, and it can be applied in other kinds of stray field rich of high energy neutrons.

  7. Modified natural diatomite and its enhanced immobilization of lead, copper and cadmium in simulated contaminated soils.

    PubMed

    Ye, Xinxin; Kang, Shenghong; Wang, Huimin; Li, Hongying; Zhang, Yunxia; Wang, Guozhong; Zhao, Huijun

    2015-05-30

    Natural diatomite was modified through facile acid treatment and ultrasonication, which increased its electronegativity, and the pore volume and surface area achieved to 0.211 cm(3) g(-1) and 76.9 m(2) g(-1), respectively. Modified diatomite was investigated to immobilize the potential toxic elements (PTEs) of Pb, Cu and Cd in simulated contaminated soil comparing to natural diatomite. When incubated with contaminated soils at rates of 2.5% and 5.0% by weight for 90 days, modified diatomite was more effective in immobilizing Pb, Cu and Cd than natural diatomite. After treated with 5.0% modified diatomite for 90 days, the contaminated soils showed 69.7%, 49.7% and 23.7% reductions in Pb, Cu and Cd concentrations after 0.01 M CaCl2 extraction, respectively. The concentrations of Pb, Cu and Cd were reduced by 66.7%, 47.2% and 33.1% in the leaching procedure, respectively. The surface complexation played an important role in the immobilization of PTEs in soils. The decreased extractable metal content of soil was accompanied by improved microbial activity which significantly increased (P<0.05) in 5.0% modified diatomite-amended soils. These results suggested that modified diatomite with micro/nanostructured characteristics increased the immobilization of PTEs in contaminated soil and had great potential as green and low-cost amendments.

  8. Modified Dirac Hamiltonian for efficient quantum mechanical simulations of micron sized devices

    NASA Astrophysics Data System (ADS)

    Habib, K. M. Masum; Sajjad, Redwan N.; Ghosh, Avik W.

    2016-03-01

    Representing massless Dirac fermions on a spatial lattice poses a potential challenge known as the Fermion Doubling problem. Addition of a quadratic term to the Dirac Hamiltonian provides a possible way to circumvent this problem. We show that the modified Hamiltonian with the additional term results in a very small Hamiltonian matrix when discretized on a real space square lattice. The resulting Hamiltonian matrix is considerably more efficient for numerical simulations without sacrificing on accuracy and is several orders of magnitude faster than the atomistic tight binding model. Using this Hamiltonian and the non-equilibrium Green's function formalism, we show several transport phenomena in graphene, such as magnetic focusing, chiral tunneling in the ballistic limit, and conductivity in the diffusive limit in micron sized graphene devices. The modified Hamiltonian can be used for any system with massless Dirac fermions such as Topological Insulators, opening up a simulation domain that is not readily accessible otherwise.

  9. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balances

    NASA Astrophysics Data System (ADS)

    Tang, G.; Bartlein, P. J.

    2012-08-01

    Satellite-based data, such as vegetation type and fractional vegetation cover, are widely used in hydrologic models to prescribe the vegetation state in a study region. Dynamic global vegetation models (DGVM) simulate land surface hydrology. Incorporation of satellite-based data into a DGVM may enhance a model's ability to simulate land surface hydrology by reducing the task of model parameterization and providing distributed information on land characteristics. The objectives of this study are to (i) modify a DGVM for simulating land surface water balances; (ii) evaluate the modified model in simulating actual evapotranspiration (ET), soil moisture, and surface runoff at regional or watershed scales; and (iii) gain insight into the ability of both the original and modified model to simulate large spatial scale land surface hydrology. To achieve these objectives, we introduce the "LPJ-hydrology" (LH) model which incorporates satellite-based data into the Lund-Potsdam-Jena (LPJ) DGVM. To evaluate the model we ran LH using historical (1981-2006) climate data and satellite-based land covers at 2.5 arc-min grid cells for the conterminous US and for the entire world using coarser climate and land cover data. We evaluated the simulated ET, soil moisture, and surface runoff using a set of observed or simulated data at different spatial scales. Our results demonstrate that spatial patterns of LH-simulated annual ET and surface runoff are in accordance with previously published data for the US; LH-modeled monthly stream flow for 12 major rivers in the US was consistent with observed values respectively during the years 1981-2006 (R2 > 0.46, p < 0.01; Nash-Sutcliffe Coefficient > 0.52). The modeled mean annual discharges for 10 major rivers worldwide also agreed well (differences < 15%) with observed values for these rivers. Compared to a degree-day method for snowmelt computation, the addition of the solar radiation effect on snowmelt enabled LH to better simulate monthly

  10. Hydrocode Simulation with Modified Johnson-Cook Model and Experimental Analysis of Explosively Formed Projectiles

    NASA Astrophysics Data System (ADS)

    Hussain, G.; Hameed, A.; Hetherington, J. G.; Barton, P. C.; Malik, A. Q.

    2013-04-01

    The formation of mild steel (MS) and copper (Cu) explosively formed projectiles (EFPs) was simulated in AUTODYN using both the Johnson-Cook (JC) and modified Johnson-Cook (JCM) constitutive models. The JC model was modified by increasing the hardening constant by 10%. The previously established semi-empirical equations for diameter, length, velocity, and depth of penetration were used to verify the design of the EFP. The length-to-diameter (L/D) ratio of the warhead used in the simulation varied between 1 < L/D < 2. To avoid projectile distortion or breakup for large standoff applications, the design of the EFP warhead was modified to obtain a lower L/D ratio. Simulations from the JC model underestimated the EFP diameter, resulting in an unrealistically elongated projectile. This shortcoming was resolved by employing the JCM model, giving good agreement with the experimental results. The projectile velocity and hole characteristics in 10-mm-thick aluminum target plates were studied for both models. The semi-empirical equations and the JC model overestimated the projectile velocity, whereas the JCM model underestimated the velocity slightly when compared to the experimental results. The depths of penetration calculated by the semi-empirical equations in the aluminum (Al) target plate were 55 and 52 mm for Cu and MS EFPs, respectively.

  11. Speeding up N-body simulations of modified gravity: Vainshtein screening models

    SciTech Connect

    Barreira, Alexandre; Bose, Sownak; Li, Baojiu E-mail: sownak.bose@durham.ac.uk

    2015-12-01

    We introduce and demonstrate the power of a method to speed up current iterative techniques for N-body modified gravity simulations. Our method is based on the observation that the accuracy of the final result is not compromised if the calculation of the fifth force becomes less accurate, but substantially faster, in high-density regions where it is relatively weak due to screening. We focus on the nDGP model which employs Vainshtein screening, and test our method by running AMR simulations in which the fifth force on the finer levels of the mesh (high density) is not obtained iteratively, but instead interpolated from coarser levels. The calculation of the standard gravity component of the force still employs the full AMR structure. We show that the impact this has on the matter power spectrum is below 1% for k < 5h/Mpc at 0z = , and even smaller at higher redshift. The impact on halo properties is also small (∼< 3% for abundance, profiles, mass; and ∼< 0.05% for positions and velocities). The method can boost the performance of modified gravity simulations by more than a factor of 10. This allows them to run on timescales similar to GR simulations and to push them to resolution levels that were previously hard to achieve.

  12. Modified Baryonic Dynamics: two-component cosmological simulations with light sterile neutrinos

    SciTech Connect

    Angus, G.W.; Gentile, G.; Diaferio, A.; Famaey, B.; Heyden, K.J. van der E-mail: diaferio@ph.unito.it E-mail: gianfranco.gentile@ugent.be

    2014-10-01

    In this article we continue to test cosmological models centred on Modified Newtonian Dynamics (MOND) with light sterile neutrinos, which could in principle be a way to solve the fine-tuning problems of the standard model on galaxy scales while preserving successful predictions on larger scales. Due to previous failures of the simple MOND cosmological model, here we test a speculative model where the modified gravitational field is produced only by the baryons and the sterile neutrinos produce a purely Newtonian field (hence Modified Baryonic Dynamics). We use two-component cosmological simulations to separate the baryonic N-body particles from the sterile neutrino ones. The premise is to attenuate the over-production of massive galaxy cluster halos which were prevalent in the original MOND plus light sterile neutrinos scenario. Theoretical issues with such a formulation notwithstanding, the Modified Baryonic Dynamics model fails to produce the correct amplitude for the galaxy cluster mass function for any reasonable value of the primordial power spectrum normalisation.

  13. Modified Involute Helical Gears: Computerized Design, Simulation of Meshing, and Stress Analysis

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert (Technical Monitor); Litvin, Faydor L.; Gonzalez-Perez, Ignacio; Carnevali, Luca; Kawasaki, Kazumasa; Fuentes-Aznar, Alfonso

    2003-01-01

    The computerized design, methods for generation, simulation of meshing, and enhanced stress analysis of modified involute helical gears is presented. The approaches proposed for modification of conventional involute helical gears are based on conjugation of double-crowned pinion with a conventional helical involute gear. Double-crowning of the pinion means deviation of cross-profile from an involute one and deviation in longitudinal direction from a helicoid surface. Using the method developed, the pinion-gear tooth surfaces are in point-contact, the bearing contact is localized and oriented longitudinally, and edge contact is avoided. Also, the influence of errors of aligment on the shift of bearing contact, vibration, and noise are reduced substantially. The theory developed is illustrated with numerical examples that confirm the advantages of the gear drives of the modified geometry in comparison with conventional helical involute gears.

  14. Modified Involute Helical Gears: Computerized Design, Simulation of Meshing and Stress Analysis

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The computerized design, methods for generation, simulation of meshing, and enhanced stress analysis of modified involute helical gears is presented. The approaches proposed for modification of conventional involute helical gears are based on conjugation of double-crowned pinion with a conventional helical involute gear. Double-crowning of the pinion means deviation of cross-profile from an involute one and deviation in longitudinal direction from a helicoid surface. Using the method developed, the pinion-gear tooth surfaces are in point-contact, the bearing contact is localized and oriented longitudinally, and edge contact is avoided. Also, the influence of errors of alignment on the shift of bearing contact, vibration, and noise are reduced substantially. The theory developed is illustrated with numerical examples that confirm the advantages of the gear drives of the modified geometry in comparison with conventional helical involute gears.

  15. The numerical simulations of explosion and implosion in air: use of a modified Harten's TVD scheme

    NASA Astrophysics Data System (ADS)

    Liu, T. G.; Khoo, B. C.; Yeo, K. S.

    1999-10-01

    Numerical simulations of explosion and implosion in air are carried out with a modified Harten's TVD scheme. The new scheme has a high resolution for contact discontinuities in addition to maintaining the good features of Harten's TVD scheme. In the numerical experiment of spherical explosion in air, the second shock wave (which does not exist in the one-dimensional shock tube problem) and its subsequent implosion on the origin have been successfully captured. The positions of the main shock wave, the contact discontinuity and the second shock wave have shown satisfactory agreement with those predicted from previous analysis. The numerical results are also compared with those obtained experimentally. Finally, simulations of a cylindrical explosion and implosion in air are carried out. Results of the cylindrical implosion in air are compared with those of previous work, including the interaction of the reflected main shock wave with the contact discontinuity and the formation of a second shock wave. All these attest to the successful use of the modified Harten's TVD scheme for the simulations of shock waves arising from explosion and implosion. Copyright

  16. Solitary wave simulations of Complex Modified Korteweg-de Vries Equation using differential quadrature method

    NASA Astrophysics Data System (ADS)

    Korkmaz, Alper; Dağ, İdris

    2009-09-01

    Complex Modified Korteweg-deVries Equation is solved numerically using differential quadrature method based on cosine expansion. Three test problems, motion of single solitary wave, interaction of solitary waves and wave generation, are simulated. The accuracy of the method is measured via the discrete root mean square error norm L, maximum error norm L for the motion of single solitary wave since it has an analytical solution. A rate of convergency analysis for motion of single solitary wave containing both real and imaginary parts is also given. Lowest three conserved quantities are computed for all test problems. A comparison with some earlier works is given.

  17. A modified next reaction method for simulating chemical systems with time dependent propensities and delays.

    PubMed

    Anderson, David F

    2007-12-01

    Chemical reaction systems with a low to moderate number of molecules are typically modeled as discrete jump Markov processes. These systems are oftentimes simulated with methods that produce statistically exact sample paths such as the Gillespie algorithm or the next reaction method. In this paper we make explicit use of the fact that the initiation times of the reactions can be represented as the firing times of independent, unit rate Poisson processes with internal times given by integrated propensity functions. Using this representation we derive a modified next reaction method and, in a way that achieves efficiency over existing approaches for exact simulation, extend it to systems with time dependent propensities as well as to systems with delays.

  18. Molecular simulation of dispersion and mechanical stability of organically modified layered silicates in polymer matrices

    NASA Astrophysics Data System (ADS)

    Fu, Yao-Tsung

    The experimental analysis of nanometer-scale separation processes and mechanical properties at buried interfaces in nanocomposites has remained difficult. We have employed molecular dynamics simulation in relation to available experimental data to alleviate such limitations and gain insight into the dispersion and mechanical stability of organically modified layered silicates in hydrophobic polymer matrices. We analyzed cleavage energies of various organically modified silicates as a function of the cation exchange capacity, surfactant head group chemistry, and chain length using MD simulations with the PCFF-PHYLLOSILICATE force field. The range of the cleavage energy is between 25 and 210 mJ/m2 upon the molecular structures and packing of surfactants. As a function of chain length, the cleavage energy indicates local minima for interlayer structures comprised of loosely packed layers of alkyl chains and local maxima for interlayer structures comprised of densely packed layers of alkyl chains between the layers. In addition, the distribution of cationic head groups between the layers in the equilibrium state determines whether large increases in cleavage energy due to Coulomb attraction. We have also examined mechanical bending and failure mechanisms of layered silicates on the nanometer scale using molecular dynamics simulation in comparison to a library of TEM data of polymer nanocomposites. We investigated the energy of single clay lamellae as a function of bending radius and different cation density. The layer energy increases particularly for bending radii below 20 nm and is largely independent of cation exchange capacity. The analysis of TEM images of agglomerated and exfoliated aluminosilicates of different CEC in polymer matrices at small volume fractions showed bending radii in excess of 100 nm due to free volumes in the polymer matrix. At a volume fraction >5%, however, bent clay layers were found with bending radii <20 nm and kinks as a failure mechanism

  19. Constrained simulations and excursion sets: understanding the risks and benefits of `genetically modified' haloes

    NASA Astrophysics Data System (ADS)

    Porciani, Cristiano

    2016-09-01

    Constrained realisations of Gaussian random fields are used in cosmology to design special initial conditions for numerical simulations. We review this approach and its application to density peaks providing several worked-out examples. We then critically discuss the recent proposal to use constrained realisations to modify the linear density field within and around the Lagrangian patches that form dark-matter haloes. The ambitious concept is to forge `genetically modified' haloes with some desired properties after the non-linear evolution. We demonstrate that the original implementation of this method is not exact but approximate because it tacitly assumes that protohaloes sample a set of random points with a fixed mean overdensity. We show that carrying out a full genetic modification is a formidable and daunting task requiring a mathematical understanding of what determines the biased locations of protohaloes in the linear density field. We discuss approximate solutions based on educated guesses regarding the nature of protohaloes. We illustrate how the excursion-set method can be adapted to predict the non-linear evolution of the modified patches and thus fine tune the constraints that are necessary to obtain preselected halo properties. This technique allows us to explore the freedom around the original algorithm for genetic modification. We find that the quantity which is most sensitive to changes is the halo mass-accretion rate at the mass scale on which the constraints are set. Finally we discuss constraints based on the protohalo angular momenta.

  20. Determination of bisphenol A in food-simulating liquids using LCED with a chemically modified electrode.

    PubMed

    D'Antuono, A; Dall'Orto, V C; Lo Balbo, A; Sobral, S; Rezzano, I

    2001-03-01

    Liquid chromatography with electrochemical detector (LC-ED), using a chemically modified electrode coated with a metalloporphyrin film, is reported for determination of bisphenol A (BPA) migration from polycarbonate baby bottles. The extraction process of the samples was performed according to regulations of the Southern Common Market (MERCOSUR), where certain food-simulating liquids [(A) distilled water, (B) acetic acid 3% V/V in distilled water, and (C) ethanol 15% V/V in distilled water] are defined along with controlled time and temperature conditions. The baseline obtained using the naked electrode showed a considerable drift which increased the detection limit. This effect was suppressed with the chemically modified electrode. A linear range up to 450 ppb along with a detection limit of 20 ppb for the amperometric detection technique was observed. The procedure described herein allowed lowering the detection limit of the method to 0.2 ppb. The value found for BPA in the food-simulating liquid is 1.2 ppb, which is below the tolerance limit for specific migration (4.8 ppm).

  1. Hydrophilic solutes in modified carbon dioxide extraction-prediction of the extractability using molecular dynamic simulation.

    PubMed

    Günther, Martina; Maus, Martin; Wagner, Karl Gerhard; Schmidt, Peter Christian

    2005-06-01

    Super- and subcritical carbon dioxide (CO2) extractions of crude drugs were simulated by molecular modelling to predict the extractability of different hydrophilic plant constituents under various extraction conditions. The CO2 extraction fluids were simulated either with pure CO2 or with solvent modified CO2 at different pressures and temperatures. Molecular modelling resulted in three different solubility parameters: the total solubility parameter delta and the partial solubility parameters delta(d) for the van der Waals and delta(EL) for the polar forces. Thus, delta(EL) enabled the estimation of the polarity of the extraction fluids and the solute molecules. If the value of delta(EL) of the extraction fluid reached the value of the solute molecule in the crude drug, i.e. minimum extraction value, the compound was soluble at the distinct extraction conditions. For a further increase in yield of the hydrophilic solutes, the polarity of the extraction fluid had to be increased, too. That means delta(EL) of the fluid exceeded the minimum extraction value. All simulations were verified by CO2 extractions of the secondary roots of Harpagophytum procumbens (harpagoside, stachyose) and the seeds of Aesculus hippocastanum (aescin). CO2 extractions of the flowers of Matricaria recutita ((-)-alpha-bisabolol) were obtained from literature data. These four constituents with different properties, like molecular size and the allocation of polar functional groups were extracted, analysed, simulated and the extract content was correlated with the extraction fluid used, respectively. PMID:15911229

  2. A modified Langmuir-Freundlich isotherm model for simulating pH-dependent adsorption effects

    NASA Astrophysics Data System (ADS)

    Jeppu, Gautham P.; Clement, T. Prabhakar

    2012-03-01

    Analytical isotherm equations such as Langmuir and Freundlich isotherms are widely used for modeling adsorption data. However, these isotherms are primarily useful for simulating data collected at a fixed pH value and cannot be easily adapted to simulate pH-dependent adsorption effects. Therefore, most adsorption studies currently use numerical surface-complexation models (SCMs), which are more complex and time consuming than traditional analytical isotherm models. In this work, we propose a new analytical isotherm model, identified as the modified Langmuir-Freundlich (MLF) isotherm, which can be used to simulate pH-dependent adsorption. The MLF isotherm uses a linear correlation between pH and affinity coefficient values. We validated the proposed MLF isotherm by predicting arsenic adsorption onto two different types of sorbents: pure goethite and goethite-coated sand. The MLF model gave good predictions for both experimental and surface complexation-model predicted datasets for these two sorbents. The proposed analytical isotherm framework can help reduce modeling complexity, model development time, and computational efforts. One of the limitations of the proposed method is that it is currently valid only for single-component systems. Furthermore, the model requires a system-specific pH. vs. affinity coefficient relation. Despite these limitations, the approach provides a promising analytical framework for simulating pH-dependent adsorption effects.

  3. Degradation behaviors of surface modified magnesium alloy wires in different simulated physiological environments

    NASA Astrophysics Data System (ADS)

    Li, Xuan; Shi, Chao; Bai, Jing; Guo, Chao; Xue, Feng; Lin, Ping-Hua; Chu, Cheng-Lin

    2014-09-01

    The degradation behaviors of the novel high-strength AZ31B magnesium alloy wires after surface modification using micro-arc-oxidization (MAO) and subsequently sealing with poly-L-lactic acid (PLLA) in different simulated physiological environments were investigated. The results show the surface MAO micropores could be physically sealed by PLLA, thus forming an effective protection to corrosion resistance for the wires. In simulated gastric fluid (SGF) at a low pH value (1.5 or 2.5), the treated wires have a high degradation rate with a rapid decrease of mass, diameter, mechanical properties and a significant increase of pH value of the immersion fluid. However, surface modification could effectively reduce the degradation rate of the treated wires in SGF with a pH value above 4.0. For the treated wires in simulated intestinal fluid at pH = 8.5, their strength retention ability is higher than that in strong acidic SGF. And the loss rate of mass is faster than that of diameter, while the pH value of the immersion fluid decreases. It should be noted that the modified wires in simulated body environment have the best strength retention ability. The wires show the different degradation behaviors indicating their different degradation mechanisms, which are also proposed in this work.

  4. Modified Nose-Hoover thermostat for solid state for constant temperature molecular dynamics simulation

    SciTech Connect

    Chen, Wen-Hwa; Wu, Chun-Hung; Cheng, Hsien-Chie

    2011-07-10

    Nose-Hoover (NH) thermostat methods incorporated with molecular dynamics (MD) simulation have been widely used to simulate the instantaneous system temperature and feedback energy in a canonical ensemble. The method simply relates the kinetic energy to the system temperature via the particles' momenta based on the ideal gas law. However, when used in a tightly bound system such as solids, the method may suffer from deriving a lower system temperature and potentially inducing early breaking of atomic bonds at relatively high temperature due to the neglect of the effect of the potential energy of atoms based on solid state physics. In this paper, a modified NH thermostat method is proposed for solid system. The method takes into account the contribution of phonons by virtue of the vibrational energy of lattice and the zero-point energy, derived based on the Debye theory. Proof of the equivalence of the method and the canonical ensemble is first made. The modified NH thermostat is tested on different gold nanocrystals to characterize their melting point and constant volume specific heat, and also their size and temperature dependence. Results show that the modified NH method can give much more comparable results to both the literature experimental and theoretical data than the standard NH. Most importantly, the present model is the only one, among the six thermostat algorithms under comparison, that can accurately reproduce the experimental data and also the T{sup 3}-law at temperature below the Debye temperature, where the specific heat of a solid at constant volume is proportional to the cube of temperature.

  5. Modified Nosé-Hoover thermostat for solid state for constant temperature molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Hwa; Wu, Chun-Hung; Cheng, Hsien-Chie

    2011-07-01

    Nosé-Hoover (NH) thermostat methods incorporated with molecular dynamics (MD) simulation have been widely used to simulate the instantaneous system temperature and feedback energy in a canonical ensemble. The method simply relates the kinetic energy to the system temperature via the particles' momenta based on the ideal gas law. However, when used in a tightly bound system such as solids, the method may suffer from deriving a lower system temperature and potentially inducing early breaking of atomic bonds at relatively high temperature due to the neglect of the effect of the potential energy of atoms based on solid state physics. In this paper, a modified NH thermostat method is proposed for solid system. The method takes into account the contribution of phonons by virtue of the vibrational energy of lattice and the zero-point energy, derived based on the Debye theory. Proof of the equivalence of the method and the canonical ensemble is first made. The modified NH thermostat is tested on different gold nanocrystals to characterize their melting point and constant volume specific heat, and also their size and temperature dependence. Results show that the modified NH method can give much more comparable results to both the literature experimental and theoretical data than the standard NH. Most importantly, the present model is the only one, among the six thermostat algorithms under comparison, that can accurately reproduce the experimental data and also the T 3-law at temperature below the Debye temperature, where the specific heat of a solid at constant volume is proportional to the cube of temperature.

  6. The use of the maharanobis and modified distances for the improvement of simulation of glutamic acid production.

    PubMed

    Kishimoto, M; Alfafara, C G; Nakajima, M; Yoshida, T; Taguchi, H

    1989-01-10

    A modified simulation procedure based on a statistical approach was investigated. The procedure predicts the time course of fed-batch culture for glutamic acid production by a temperature-sensitive strain of Brevibacterium flavum. The statistical approach requires only a data base of state points obtained in experiments, and not perfect identification of fermentation models. The simulation procedure is based on regression analysis to estimate specific rate parameters of system equations using the data points selected with reference to the Euclid distance. It was modified in that the data selection procedure included the use of the Maharanobis distance as well as a modified distance defined in this study. Simulation results using the modified procedure allow reasonable prediction of the time course of fed-batch culture for glutamic acid compared to that involving the Euclid distance alone.

  7. Development of modified cable models to simulate accurate neuronal active behaviors.

    PubMed

    Elbasiouny, Sherif M

    2014-12-01

    In large network and single three-dimensional (3-D) neuron simulations, high computing speed dictates using reduced cable models to simulate neuronal firing behaviors. However, these models are unwarranted under active conditions and lack accurate representation of dendritic active conductances that greatly shape neuronal firing. Here, realistic 3-D (R3D) models (which contain full anatomical details of dendrites) of spinal motoneurons were systematically compared with their reduced single unbranched cable (SUC, which reduces the dendrites to a single electrically equivalent cable) counterpart under passive and active conditions. The SUC models matched the R3D model's passive properties but failed to match key active properties, especially active behaviors originating from dendrites. For instance, persistent inward currents (PIC) hysteresis, frequency-current (FI) relationship secondary range slope, firing hysteresis, plateau potential partial deactivation, staircase currents, synaptic current transfer ratio, and regional FI relationships were not accurately reproduced by the SUC models. The dendritic morphology oversimplification and lack of dendritic active conductances spatial segregation in the SUC models caused significant underestimation of those behaviors. Next, SUC models were modified by adding key branching features in an attempt to restore their active behaviors. The addition of primary dendritic branching only partially restored some active behaviors, whereas the addition of secondary dendritic branching restored most behaviors. Importantly, the proposed modified models successfully replicated the active properties without sacrificing model simplicity, making them attractive candidates for running R3D single neuron and network simulations with accurate firing behaviors. The present results indicate that using reduced models to examine PIC behaviors in spinal motoneurons is unwarranted.

  8. Characterization of double modified internal gate pixel by 3D simulation study

    NASA Astrophysics Data System (ADS)

    Aurola, A.; Marochkin, V.; Tuuva, T.

    2015-01-01

    We have developed a novel detector concept based on Modified Internal Gate Field Effect Transistor (MIGFET) wherein a buried Modified Internal Gate (MIG) is implanted underneath a channel of a FET. In between the MIG and the channel of the FET there is a depleted semiconductor material forming a potential barrier between charges in the channel and similar type signal charges located in the MIG. The signal charges in the MIG have a measurable effect on the conductance of the channel. In this paper a double MIGFET pixel is investigated comprising two MIGFETs. By transferring the signal charges between the two MIGs Non-Destructive Correlated Double Sampling Readout (NDCDSR) is enabled. The proposed MIG radiation detector suits particularly well for low-light-level imaging, X-ray spectroscopy, as well as synchrotron and X-ray Free Electron Laser (XFEL) facilities. The reason for the excellent X-ray detection performance stems from the fact that interface related issues can be considerably mitigated since interface generated dark noise can be completely avoided and interface generated 1/f and Random Telegraph Signal (RTS) noise can be considerably reduced due to a deep buried channel readout configuration. Electrical parameters of the double MIGFET pixel have been evaluated by 3D TCAD simulation study. Simulation results show the absence of interface generated dark noise, significantly reduced interface generated 1/f and RTS noise, well performing NDCDSR operation, and blooming protection due to an inherent vertical anti-blooming structure. In addition, the backside illuminated thick fully depleted pixel design provides a homogeneous radiation entry window, low crosstalk due to lack of diffusion, and good quantum efficiency for low energy X-rays and NIR light. These facts result in excellent Signal-to-Noise Ratio (SNR) and very low crosstalk enabling thus excellent X-ray energy and spatial resolution. The simulation demonstrates the charge to current conversion gain for

  9. Discrete element simulation of dense granular flow in a modified Couette cell.

    SciTech Connect

    Lechman, Jeremy B.; Grest, Gary Stephen

    2005-02-01

    Large-scale three dimensional Discrete Element simulations of granular flow in a modified split-bottom Couette cell for packs of up to 180,000 mono-disperse spheres are presented and compared with experiments. We find that the velocity profiles collapse onto a universal curve not only at the surface but also in the bulk of the pack until slip between layers becomes significant. In agreement with experiment, we find similar relations between the cell geometry and parameters involved in rescaling the velocities at the surface and in the bulk. Likewise, a change in the shape of the shear zone is observed as predicted for tall packs once the center of the shear zone is correctly defined; although the transition does not appear to be first order. Finally, the effect of cohesion is considered as a means to test the theoretical predictions.

  10. Modified motor unit number index: A simulation study of the first dorsal interosseous muscle.

    PubMed

    Li, Xiaoyan; Nandedkar, Sanjeev D; Zhou, Ping

    2016-02-01

    The motor unit number index (MUNIX) technique has provided a quick and convenient approach to estimating motor unit population changes in a muscle. Reduction in motor unit action potential (MUAP) amplitude can lead to underestimation of motor unit numbers using the standard MUNIX technique. This study aims to overcome this limitation by developing a modified MUNIX (mMUNIX) technique. The mMUNIX uses a variable that is associated with the area of compound muscle action potential (CMAP) rather than an arbitrary fixed value (20 mV ms) as used in the standard MUNIX to define the output. The performance of the mMUNIX was evaluated using motoneuron pool and surface electromyography (EMG) models. With a fixed motor unit number, the mMUNIX output remained relatively constant with varying degrees of MUAP amplitude changes, while the standard MUNIX substantially underestimated the motor unit number in such cases. However, when MUAP amplitude remained unchanged, the mMUNIX showed less sensitivity than the standard MUNIX in tracking motor unit loss. The current simulation study demonstrated both the advantages and limitations of the standard and modified MUNIX techniques, which can help guide appropriate application and interpretation of MUNIX measurements. PMID:26639774

  11. Nonequilibrium Molecular Dynamics Simulations of Organic Friction Modifiers Adsorbed on Iron Oxide Surfaces.

    PubMed

    Ewen, James P; Gattinoni, Chiara; Morgan, Neal; Spikes, Hugh A; Dini, Daniele

    2016-05-10

    For the successful development and application of lubricants, a full understanding of the nanoscale behavior of complex tribological systems is required, but this is difficult to obtain experimentally. In this study, we use nonequilibrium molecular dynamics (NEMD) simulations to examine the atomistic structure and friction properties of commercially relevant organic friction modifier (OFM) monolayers adsorbed on iron oxide surfaces and lubricated by a thin, separating layer of hexadecane. Specifically, acid, amide, and glyceride OFMs, with saturated and Z-unsaturated hydrocarbon tail groups, are simulated at various surface coverages and sliding velocities. At low and medium coverage, the OFMs form liquidlike and amorphous monolayers, respectively, which are significantly interdigitated with the hexadecane lubricant, resulting in relatively high friction coefficients. At high coverage, solidlike monolayers are formed for all of the OFMs, which, during sliding, results in slip planes between well-defined OFM and hexadecane layers, yielding a marked reduction in the friction coefficient. When present at equal surface coverage, OFMs with saturated and Z-unsaturated tail groups are found to yield similar structure and friction behavior. OFMs with glyceride head groups yield significantly lower friction coefficients than amide and particularly carboxylic acid head groups. For all of the OFMs and coverages simulated, the friction coefficient is found to increase linearly with the logarithm of sliding velocity; however, the gradient of this increase depends on the coverage. The structure and friction details obtained from these simulations agree well with experimental results and also shed light on the relative tribological performance of these OFMs through nanoscale structural variations. This has important implications in terms of the applicability of NEMD to aid the development of new formulations to control friction.

  12. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balance

    NASA Astrophysics Data System (ADS)

    Tang, G.; Bartlein, P. J.

    2012-01-01

    Water balance models of simple structure are easier to grasp and more clearly connect cause and effect than models of complex structure. Such models are essential for studying large spatial scale land surface water balance in the context of climate and land cover change, both natural and anthropogenic. This study aims to (i) develop a large spatial scale water balance model by modifying a dynamic global vegetation model (DGVM), and (ii) test the model's performance in simulating actual evapotranspiration (ET), soil moisture and surface runoff for the coterminous United States (US). Toward these ends, we first introduced development of the "LPJ-Hydrology" (LH) model by incorporating satellite-based land covers into the Lund-Potsdam-Jena (LPJ) DGVM instead of dynamically simulating them. We then ran LH using historical (1982-2006) climate data and satellite-based land covers at 2.5 arc-min grid cells. The simulated ET, soil moisture and surface runoff were compared to existing sets of observed or simulated data for the US. The results indicated that LH captures well the variation of monthly actual ET (R2 = 0.61, p < 0.01) in the Everglades of Florida over the years 1996-2001. The modeled monthly soil moisture for Illinois of the US agrees well (R2 = 0.79, p < 0.01) with the observed over the years 1984-2001. The modeled monthly stream flow for most 12 major rivers in the US is consistent R2 > 0.46, p < 0.01; Nash-Sutcliffe Coefficients >0.52) with observed values over the years 1982-2006, respectively. The modeled spatial patterns of annual ET and surface runoff are in accordance with previously published data. Compared to its predecessor, LH simulates better monthly stream flow in winter and early spring by incorporating effects of solar radiation on snowmelt. Overall, this study proves the feasibility of incorporating satellite-based land-covers into a DGVM for simulating large spatial scale land surface water balance. LH developed in this study should be a useful

  13. Simulation of emotional contagion using modified SIR model: A cellular automaton approach

    NASA Astrophysics Data System (ADS)

    Fu, Libi; Song, Weiguo; Lv, Wei; Lo, Siuming

    2014-07-01

    Emotion plays an important role in the decision-making of individuals in some emergency situations. The contagion of emotion may induce either normal or abnormal consolidated crowd behavior. This paper aims to simulate the dynamics of emotional contagion among crowds by modifying the epidemiological SIR model to a cellular automaton approach. This new cellular automaton model, entitled the “CA-SIRS model”, captures the dynamic process ‘susceptible-infected-recovered-susceptible', which is based on SIRS contagion in epidemiological theory. Moreover, in this new model, the process is integrated with individual movement. The simulation results of this model show that multiple waves and dynamical stability around a mean value will appear during emotion spreading. It was found that the proportion of initial infected individuals had little influence on the final stable proportion of infected population in a given system, and that infection frequency increased with an increase in the average crowd density. Our results further suggest that individual movement accelerates the spread speed of emotion and increases the stable proportion of infected population. Furthermore, decreasing the duration of an infection and the probability of reinfection can markedly reduce the number of infected individuals. It is hoped that this study will be helpful in crowd management and evacuation organization.

  14. Prediction of fatique crack growth under flight-simulation loading with the modified CORPUS model

    NASA Technical Reports Server (NTRS)

    Padmadinata, U. H.; Schijve, J.

    1994-01-01

    The CORPUS (Computation Of Retarded Propagation Under Spectrum loading) crack growth prediction model for variable-amplitude loading, as introduced by De Koning, was based on crack closure. It includes a multiple-overload effect and a transition from plane strain to plane stress. In the modified CORPUS model an underload affected zone (ULZ) is introduced, which is significant for flight-simulation loading in view of the once per flight compressive ground load. The ULZ is associated with reversed plastic deformation induced by the underloads after crack closure has already occurred. Predictions of the crack growth fatigue life are presented for a large variety of flight-simulation test series on 2024-T3 sheet specimens in order to reveal the effects of a number of variables: the design stress level, the gust spectrum severity, the truncation level (clipping), omission of small cycles, and the ground stress level. Tests with different load sequences are also included. The trends of the effects induced by the variables are correctly predicted. The quantitative agreement between the predictions and the test results is also satisfactory.

  15. Simulation and analysis of congestion risk during escalator transfers using a modified social force model

    NASA Astrophysics Data System (ADS)

    Li, Wenhang; Gong, Jianhua; Yu, Ping; Shen, Shen; Li, Rong; Duan, Qishen

    2015-02-01

    The congestion risk during escalator transfers was simulated based on a modified social force model. A four-stage transfer model was proposed. A projection strategy was employed to calculate the social forces for inclined surfaces, and a schedule-line model was proposed to calculate the targets adaptively. Realistic simulations of escalator transfer activities were achieved. The results demonstrate that the spatial distribution of the congestion risks is inhomogeneous. A few areas contain clearly higher risks, and the congestion risk is higher in the transfer aisles than on the escalators. The congestion risk in the transfer aisle is influenced more by the average pedestrian speed than that of the escalators. Slower walkers in the transfer aisle may cause congestion, which is more serious when the escalator speed is faster than that of the pedestrians. Therefore, to reduce the congestion risk, the speed of the escalator should be set slower than the average speed of the pedestrians, and conductors can be employed to divert the traffic at the entrance, turns, and exit of the escalator.

  16. A modified TIP3P water potential for simulation with Ewald summation

    NASA Astrophysics Data System (ADS)

    Price, Daniel J.; Brooks, Charles L.

    2004-11-01

    The charges and Lennard-Jones parameters of the TIP3P water potential have been modified to improve its performance under the common condition for molecular dynamics simulations of using Ewald summation in lieu of relatively short nonbonded truncation schemes. These parameters were optimized under the condition that the hydrogen atoms do not have Lennard-Jones parameters, thus making the model independent of the combining rules used for the calculation of nonbonded, heteroatomic interaction energies, and limiting the number of Lennard-Jones calculations required. Under these conditions, this model provides accurate density (ρ=0.997 g/ml) and heat of vaporization (ΔHvap=10.53 kcal/mol) at 25 °C and 1 atm, but also provides improved structure in the second peak of the O-O radial distribution function and improved values for the dielectric constant (ɛ0=89) and the diffusion coefficient (D=4.0×10-5 cm2/s) relative to the original parametrization. Like the original parameterization, however, this model does not show a temperature density maximum. Several similar models are considered with the additional constraint of trying to match the performance of the optimized potentials for liquid simulation atom force field to that obtained when using the simulation conditions under which it was originally designed, but no model was entirely satisfactory in reproducing the relative difference in free energies of hydration between the model compounds, phenol and benzene. Finally, a model that incorporates a long-range correction for truncated Lennard-Jones interactions is presented, which provides a very accurate dielectric constant (ɛ0=76), however, the improvement in this estimate is on the same order as the uncertainty in the calculation.

  17. Imaging in turbid media by modified filtered back projection method using data from Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Aggarwal, Ashwani; Vasu, Ram M.

    2003-07-01

    Noninvasive diagnosis in medicine has shown considerable attention in recent years. Several methods are already available for imaging the biological tissue like X-ray computerized tomography, magentic resonance imaging and ultrasound imaging et c. But each of these methods has its own disadvantages. Optical tomography which uses NIR light is one of the emerging methods in teh field of medical imaging because it is non-invasive in nature. The only problem that occurs in using light for imaging the tissue is that it is highly scattered inside tissue, so the propagation of light in tissue is not confined to straight lines as is the case with X-ray tomography. Therefore the need arises to understand the behaviour of propagation of light in tissue. There are several methods for light interaction with tissue. Monte Carlo method is one of these methods which is a simple technique for simulation of light through tissue. The only problem faced with Monte Carlo simulation is its high computational time. Once the data is obtained using Monte Carlo simulation, it need to be inverted to obtain the reconstruction of tissue image. There are standard methods of reconstruction like algebraic reconstruction method, filtered backprojection method etc. But these methods can not be used as such in the case when light is used as probing radiations because it is highly scattered inside the tissue. The standard filtered backprojection method has been modified so that the zigzag path of photons is taken into consideration while back projecting the data. This is achieved by dividing the tissue domain in a square grid and storing the average path traversed in each grid element. It has been observed that the reconstruction obtained using this modification is much better than the result in case of standard filtered backprojection method.

  18. Degradation of transgenic DNA from genetically modified soya and maize in human intestinal simulations.

    PubMed

    Martín-Orúe, Susana M; O'Donnell, Anthony G; Ariño, Joaquin; Netherwood, Trudy; Gilbert, Harry J; Mathers, John C

    2002-06-01

    The inclusion of genetically modified (GM) foods in the human diet has caused considerable debate. There is concern that the transfer of plant-derived transgenes to the resident intestinal microflora could have safety implications. For these gene transfer events to occur, the nucleic acid would need to survive passage through the gastrointestinal tract. The aim of the present study was to evaluate the rate at which transgenes, contained within GM soya and maize, are degraded in gastric and small bowel simulations. The data showed that 80 % of the transgene in naked GM soya DNA was degraded in the gastric simulations, while no degradation of the transgenes contained within GM soya and maize were observed in these acidic conditions. In the small intestinal simulations, transgenes in naked soya DNA were degraded at a similar rate to the material in the soya protein. After incubation for 30 min, the transgenes remaining in soya protein and naked DNA were 52 (sem 13.1) % and 34 (sem 17.5) %, respectively, and at the completion of the experiment (3 h) these values were 5 % and 3 %, respectively. In contrast to the soya transgene, the maize nucleic acid was hydrolysed in the small intestinal simulations in a biphasic process in which approximately 85 % was rapidly degraded, while the rest of the DNA was cleaved at a rate similar to that in the soya material. Guar gum and tannic acid, molecules that are known to inhibit digestive enzymes, did not influence the rate of transgene degradation in soya protein. In contrast guar gum reduced the rate of transgene degradation in naked soya DNA in the initial stages, but the polysaccharide did not influence the amount of nucleic acid remaining at the end of the experiment. Tannic acid reduced the rate of DNA degradation throughout the small bowel simulations, with 21 (sem 5.4) % and 2 (sem 1.8) % of the naked soya DNA remaining in the presence and absence of the phenolic acid, respectively. These data indicate that some transgenes

  19. Simulated geochemical weathering of a mineral ash-rich biochar in a modified Soxhlet reactor.

    PubMed

    Yao, F X; Arbestain, M Camps; Virgel, S; Blanco, F; Arostegui, J; Maciá-Agulló, J A; Macías, F

    2010-08-01

    Although there are many studies on the characterization of C in biochar and its C sequestration potential, there is little knowledge on the mineral fraction in biochar and its weathering. The latter, however, can have powerful implications on nutrient availability. In the present study, a modified Soxhlet reactor was used to simulate the long-term geochemical weathering of an ash-rich biochar produced from sewage sludge of a non-industrial area in New Zealand. The weathering process took place during a period of 300 h, with and without the addition of humic acid (1.00 g added to 20.00 g of biochar), and the treatments were referred to as treatment BC-HA and BC-B, respectively. Both the leaching kinetics and the transformations within the solid phase were studied. The results revealed that substantial amounts of K (8.5-10.2%) and S (20.2-28.3%) were recovered in the weathering solutions. Noticeable Ca (17.9-20.7%) and P (15.4%) in the solid were released but only a few were recovered in the weathering solutions because of the precipitation. The presence of humic acids increased this dissolution and thus the availability of K, S, Ca, Mg and P, but induced N immobilization. Nitrogen availability was already very low (<1.0% of the total N) due to the probable recalcitrant heterocyclic N structure. The pH of the biochar samples dropped from 8.4 to 7.5; this was mainly attributed to loss of base cations through leaching and probable carbonation of the system. The XPS spectra evidenced the oxidation of C in biochar during the weathering process with the formation of carbonyl and carboxylic functional groups. The results obtained in this study showed some promise for the positive use of modified Soxhlet extractor in simulating the geochemical weathering in ash-rich biochars and providing a better understanding on the kinetics of nutrient release. This will be key information in assessing the added value of biochars as soil amendments.

  20. Molecular dynamics simulations of cinchonidine-modified platinum in ethanol: comparisons with surface studies

    NASA Astrophysics Data System (ADS)

    Calvo, Sergio R.; LeBlanc, Rene J.; Williams, Christopher T.; Balbuena, Perla B.

    2004-08-01

    The interaction of the chiral modifier cinchonidine with Pt(1 1 1) both in ultrahigh vacuum (UHV) and in ethanol solvent has been studied using molecular dynamics (MD) simulation. In UHV at low coverage (0.0125 molecules/Pt atom) and 298.15 K the cinchonidine was found to adsorb with the quinoline ring oriented largely parallel ( α=6°) to the surface. Cinchonidine surface attachment was found to be through both π bonding of the aromatic group and adsorption of the CC double bond of the vinyl group. The dihedral angles T1 and T2 are reduced about 30° and 20°, respectively, with respect to those corresponding to the vacuum free molecule, revealing the strong molecule-surface interaction. A previous UHV experimental study in the literature performed at similar coverage ( θ≈0.03 molecules/Pt atom) of the related aromatic molecule quinoline shows an aromatic tilt of ≈15°, which is in reasonable agreement with the present MD simulations. The interactions between ethanol solutions of cinchonidine (0.129 and 1.035 M) and the platinum surface were also simulated at 298.15 K. The cinchonidine coverage was found to be 0.0125 molecules/Pt atom for a 0.129 M solution and approximately 0.0375 molecules/Pt for 1.035 M. The results indicate that either the entire quinoline group or at least part of the quinoline group is attached to the platinum surface (via the π system) in all cases. For the less concentrated solution (0.129 M) we found two different equilibrium conformations, one in which only part of the quinoline is attached to the surface, and a slightly more stable conformation that involves the quinoline group being adsorbed parallel to the platinum surface. We found that cinchonidine conformation at the surface was not only affected by the ethanol solvent, but also by the cinchonidine-cinchonidine steric interactions and their competition for surface sites. These MD simulations are compared with recent in situ Raman and infrared studies of this important

  1. Modifying stochastic slip distributions based on dynamic simulations for use in probabilistic tsunami hazard evaluation.

    NASA Astrophysics Data System (ADS)

    Murphy, Shane; Scala, Antonio; Lorito, Stefano; Herrero, Andre; Festa, Gaetano; Nielsen, Stefan; Trasatti, Elisa; Tonini, Roberto; Romano, Fabrizio; Molinari, Irene

    2016-04-01

    Stochastic slip modelling based on general scaling features with uniform slip probability over the fault plane is commonly employed in tsunami and seismic hazard. However, dynamic rupture effects driven by specific fault geometry and frictional conditions can potentially control the slip probability. Unfortunately dynamic simulations can be computationally intensive, preventing their extensive use for hazard analysis. The aim of this study is to produce a computationally efficient stochastic model that incorporates slip features observed in dynamic simulations. Dynamic rupture simulations are performed along a transect representing an average along-depth profile on the Tohoku subduction interface. The surrounding media, effective normal stress and friction law are simplified. Uncertainty in the nucleation location and pre-stress distribution are accounted for by using randomly located nucleation patches and stochastic pre-stress distributions for 500 simulations. The 1D slip distributions are approximated as moment magnitudes on the fault plane based on empirical scaling laws with the ensemble producing a magnitude range of 7.8 - 9.6. To measure the systematic spatial slip variation and its dependence on earthquake magnitude we introduce the concept of the Slip Probability density Function (SPF). We find that while the stochastic SPF is magnitude invariant, the dynamically derived SPF is magnitude-dependent and shows pronounced slip amplification near the surface for M > 8.6 events. To incorporate these dynamic features in the stochastic source models, we sub-divide the dynamically derived SPFs into 0.2 magnitude bins and compare them with the stochastic SPF in order to generate a depth and magnitude dependent transfer function. Applying this function to the traditional stochastic slip distribution allows for an approximated but efficient incorporation of regionally specific dynamic features in a modified source model, to be used specifically when a significant

  2. Modifier mass transfer kinetic effect in the performance of solvent gradient simulated moving bed (SG-SMB) process

    NASA Astrophysics Data System (ADS)

    Câmara, L. D. T.

    2015-09-01

    The solvent-gradient simulated moving bed process (SG-SMB) is the new tendency in the performance improvement if compared to the traditional isocratic solvent conditions. In such SG-SMB separation process the modulation of the solvent strength leads to significant increase in the purities and productivity followed by reduction in the solvent consumption. A stepwise modelling approach was utilized in the representation of the interconnected chromatographic columns of the system combined with lumped mass transfer models between the solid and liquid phase. The influence of the solvent modifier was considered applying the Abel model which takes into account the effect of modifier volume fraction over the partition coefficient. The modelling and simulations were carried out and compared to the experimental SG-SMB separation of the amino acids phenylalanine and tryptophan. A lumped mass transfer kinetic model was applied for both the modifier (ethanol) as well as the solutes. The simulation results showed that such simple and global mass transfer models are enough to represent all the mass transfer effect between the solid adsorbent and the liquid phase. The separation performance can be improved reducing the interaction or the mass transfer kinetic effect between the solid adsorbent phase and the modifier. The simulations showed great agreement fitting the experimental data of the amino acids concentrations both at the extract as well as at the raffinate.

  3. Effects of Varying Particle Sizes and Different Types of LDH-Modified Anthracite in Simulated Test Columns for Phosphorous Removal.

    PubMed

    Zhang, Xiangling; Chen, Qiaozhen; Guo, Lu; Huang, Hualing; Ruan, Chongying

    2015-06-16

    A comparative study was carried out for the removal of phosphorus in simulated unplanted vertical-flow constructed wetlands with different layered double hydroxide (LDHs) coated anthracite substrates. Three particle sizes of anthracites were selected and modified separately with nine kinds of LDH coating. The simulated substrates test columns loaded with the original and modified anthracites were constructed to treat the contaminated water. For the medium and large particle size modified anthracite substrates, the purification effects of total phosphorus, total dissolved phosphorus and phosphate were improved by various degrees, and the purification effect of the medium particle size anthracite is better than that of the large size one. The medium size anthracite modified by ZnCo-LDHs had optimal performance with average removal efficiencies of total phosphorus, total dissolved phosphorus and phosphate reaching 95%, 95% and 98%, respectively. The maximum adsorption capacity on ZnCo-LDHs and ZnAl-LDHs modified medium sizes anthracites were 65.79 (mg/kg) and 48.78 (mg/kg), respectively. In comparison, the small size anthracite is not suitable for LDHs modification.

  4. Modified conceptual model for compensated root water uptake - A simulation study

    NASA Astrophysics Data System (ADS)

    Peters, Andre

    2016-03-01

    Modeling root water uptake within the macroscopic approach is usually done by introducing a sink term in the Richards equation. This sink term represents potential water uptake reduced by a so-called stress reduction factor accounting for stress due to high suctions, oxygen deficit or salinity. Since stress in some parts of the soil can be compensated by enhanced water uptake in less stressed parts, several compensation models have been suggested. One of them is the empirical model of Jarvis, which is often applied due to its mathematical elegance and simplicity. However, it has been discussed that under certain conditions and assumptions this model might predict too high transpiration rates, which are not in agreement with the assumed stress reduction function. The aim of this paper is (i) to analyze these inconsistencies and (ii) to introduce a simple constraint for transpiration in a way as if the complete water would be taken form the location with highest uptake rate in the uncompensated case. Transpiration from 50 cm deep soils with hydraulic functions representing different textures, ranging from a clay loam to a coarse sand, was simulated with the original and the modified model using HYDRUS-1D. Root distribution was assumed to be uniform or linearly decreasing with depth. In case of the fine textured soils and uniform root density, the original model predicted transpiration equal to potential transpiration even when the complete root domain was already heavily stressed if the maximum enhancement factor for uptake was 2. These results are not in agreement with the original meaning of the stress reduction function. The modification eliminates the inconsistencies by limiting transpiration to a maximum value based on the highest uncompensated uptake rate in the root zone. It does neither increase the mathematical complexity nor require any additional parameters.

  5. 3D transient electromagnetic simulation using a modified correspondence principle for wave and diffusion fields

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Ji, Y.; Egbert, G. D.

    2015-12-01

    The fictitious time domain method (FTD), based on the correspondence principle for wave and diffusion fields, has been developed and used over the past few years primarily for marine electromagnetic (EM) modeling. Here we present results of our efforts to apply the FTD approach to land and airborne TEM problems which can reduce the computer time several orders of magnitude and preserve high accuracy. In contrast to the marine case, where sources are in the conductive sea water, we must model the EM fields in the air; to allow for topography air layers must be explicitly included in the computational domain. Furthermore, because sources for most TEM applications generally must be modeled as finite loops, it is useful to solve directly for the impulse response appropriate to the problem geometry, instead of the point-source Green functions typically used for marine problems. Our approach can be summarized as follows: (1) The EM diffusion equation is transformed to a fictitious wave equation. (2) The FTD wave equation is solved with an explicit finite difference time-stepping scheme, with CPML (Convolutional PML) boundary conditions for the whole computational domain including the air and earth , with FTD domain source corresponding to the actual transmitter geometry. Resistivity of the air layers is kept as low as possible, to compromise between efficiency (longer fictitious time step) and accuracy. We have generally found a host/air resistivity contrast of 10-3 is sufficient. (3)A "Modified" Fourier Transform (MFT) allow us recover system's impulse response from the fictitious time domain to the diffusion (frequency) domain. (4) The result is multiplied by the Fourier transformation (FT) of the real source current avoiding time consuming convolutions in the time domain. (5) The inverse FT is employed to get the final full waveform and full time response of the system in the time domain. In general, this method can be used to efficiently solve most time-domain EM

  6. Effects of modified soil water-heat physics on RegCM4 simulations of climate over the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Xuejia; Pang, Guojin; Yang, Meixue; Wan, Guoning

    2016-06-01

    To optimize the description of land surface processes and improve climate simulations over the Tibetan Plateau (TP), a modified soil water-heat parameterization scheme (SWHPS) is implemented into the Community Land Model 3.5 (CLM3.5), which is coupled to the regional climate model 4 (RegCM4). This scheme includes Johansen's soil thermal conductivity scheme together with Niu's groundwater module. Two groups of climate simulations are then performed using the original RegCM4 and revised RegCM4 to analyze the effects of the revised SWHPS on regional climate simulations. The effect of the revised RegCM4 on simulated air temperature is relatively small (with mean biases changing by less than 0.1°C over the TP). There are overall improvements in the simulation of winter and summer air temperature but increased errors in the eastern TP. It has a significant effect on simulated precipitation. There is also a clear improvement in simulated annual and winter precipitation, particularly over the northern TP, including the Qilian Mountains and the source region of the Yellow River. There are, however, increased errors in precipitation simulation in parts of the southern TP. The precipitation difference between the two models is caused mainly by their convective precipitation difference, particularly in summer. Overall, the implementation of the new SWHPS into the RegCM4 has a significant effect not only on land surface variables but also on the overlying atmosphere through various physical interactions.

  7. On a modified Monte-Carlo method and variable soft sphere model for rarefied binary gas mixture flow simulation

    NASA Astrophysics Data System (ADS)

    Nourazar, S. S.; Jahangiri, P.; Aboutalebi, A.; Ganjaei, A. A.; Nourazar, M.; Khadem, J.

    2011-06-01

    The effect of new terms in the improved algorithm, the modified direct simulation Monte-Carlo (MDSMC) method, is investigated by simulating a rarefied binary gas mixture flow inside a rotating cylinder. Dalton law for the partial pressures contributed by each species of the binary gas mixture is incorporated into our simulation using the MDSMC method and the direct simulation Monte-Carlo (DSMC) method. Moreover, the effect of the exponent of the cosine of deflection angle (α) in the inter-molecular collision models, the variable soft sphere (VSS) and the variable hard sphere (VHS), is investigated in our simulation. The improvement of the results of simulation is pronounced using the MDSMC method when compared with the results of the DSMC method. The results of simulation using the VSS model show some improvements on the result of simulation for the mixture temperature at radial distances close to the cylinder wall where the temperature reaches the maximum value when compared with the results using the VHS model.

  8. Employing a Modified Diffuser Momentum Model to Simulate Ventilation of the Orion CEV (DRAFT)

    NASA Technical Reports Server (NTRS)

    Straus, John; Ball, Tyler; OHara, William; Barido, Richard

    2011-01-01

    Computational Fluid Dynamics (CFD) is used to model the flow field in the Orion CEV cabin. The CFD model employs a momentum model used to account for the effect of supply grilles on the supply flow. The momentum model is modified to account for non-uniform velocity profiles at the approach of the supply grille. The modified momentum model is validated against a detailed vane-resolved model before inclusion into the Orion CEV cabin model. Results for this comparison, as well as that of a single ventilation configuration are presented.

  9. Low-dose photons modify liver response to simulated solar particle event protons.

    PubMed

    Gridley, Daila S; Coutrakon, George B; Rizvi, Asma; Bayeta, Erben J M; Luo-Owen, Xian; Makinde, Adeola Y; Baqai, Farnaz; Koss, Peter; Slater, James M; Pecaut, Michael J

    2008-03-01

    The health consequences of exposure to low-dose radiation combined with a solar particle event during space travel remain unresolved. The goal of this study was to determine whether protracted radiation exposure alters gene expression and oxidative burst capacity in the liver, an organ vital in many biological processes. C57BL/6 mice were whole-body irradiated with 2 Gy simulated solar particle event (SPE) protons over 36 h, both with and without pre-exposure to low-dose/low-dose-rate photons ((57)Co, 0.049 Gy total at 0.024 cGy/h). Livers were excised immediately after irradiation (day 0) or on day 21 thereafter for analysis of 84 oxidative stress-related genes using RT-PCR; genes up or down-regulated by more than twofold were noted. On day 0, genes with increased expression were: photons, none; simulated SPE, Id1; photons + simulated SPE, Bax, Id1, Snrp70. Down-regulated genes at this same time were: photons, Igfbp1; simulated SPE, Arnt2, Igfbp1, Il6, Lct, Mybl2, Ptx3. By day 21, a much greater effect was noted than on day 0. Exposure to photons + simulated SPE up-regulated completely different genes than those up-regulated after either photons or the simulated SPE alone (photons, Cstb; simulated SPE, Dctn2, Khsrp, Man2b1, Snrp70; photons + simulated SPE, Casp1, Col1a1, Hspcb, Il6st, Rpl28, Spnb2). There were many down-regulated genes in all irradiated groups on day 21 (photons, 13; simulated SPE, 16; photons + simulated SPE, 16), with very little overlap among groups. Oxygen radical production by liver phagocytes was significantly enhanced by photons on day 21. The results demonstrate that whole-body irradiation with low-dose-rate photons, as well as time after exposure, had a great impact on liver response to a simulated solar particle event.

  10. Low-dose photons modify liver response to simulated solar particle event protons.

    PubMed

    Gridley, Daila S; Coutrakon, George B; Rizvi, Asma; Bayeta, Erben J M; Luo-Owen, Xian; Makinde, Adeola Y; Baqai, Farnaz; Koss, Peter; Slater, James M; Pecaut, Michael J

    2008-03-01

    The health consequences of exposure to low-dose radiation combined with a solar particle event during space travel remain unresolved. The goal of this study was to determine whether protracted radiation exposure alters gene expression and oxidative burst capacity in the liver, an organ vital in many biological processes. C57BL/6 mice were whole-body irradiated with 2 Gy simulated solar particle event (SPE) protons over 36 h, both with and without pre-exposure to low-dose/low-dose-rate photons ((57)Co, 0.049 Gy total at 0.024 cGy/h). Livers were excised immediately after irradiation (day 0) or on day 21 thereafter for analysis of 84 oxidative stress-related genes using RT-PCR; genes up or down-regulated by more than twofold were noted. On day 0, genes with increased expression were: photons, none; simulated SPE, Id1; photons + simulated SPE, Bax, Id1, Snrp70. Down-regulated genes at this same time were: photons, Igfbp1; simulated SPE, Arnt2, Igfbp1, Il6, Lct, Mybl2, Ptx3. By day 21, a much greater effect was noted than on day 0. Exposure to photons + simulated SPE up-regulated completely different genes than those up-regulated after either photons or the simulated SPE alone (photons, Cstb; simulated SPE, Dctn2, Khsrp, Man2b1, Snrp70; photons + simulated SPE, Casp1, Col1a1, Hspcb, Il6st, Rpl28, Spnb2). There were many down-regulated genes in all irradiated groups on day 21 (photons, 13; simulated SPE, 16; photons + simulated SPE, 16), with very little overlap among groups. Oxygen radical production by liver phagocytes was significantly enhanced by photons on day 21. The results demonstrate that whole-body irradiation with low-dose-rate photons, as well as time after exposure, had a great impact on liver response to a simulated solar particle event. PMID:18302490

  11. Rationalizing the effects of modified electrostatic interactions in computer simulations: The dielectric self-consistent field method

    NASA Astrophysics Data System (ADS)

    Boresch, Stefan; Steinhauser, Othmar

    1999-11-01

    The dielectric self-consistent field method, a novel tool to study solvated systems based on continuum electrostatics, is introduced. It permits the qualitative and even semiquantitative calculation of orientational correlation functions, i.e., it gives insights into the orientational structure of a solute-solvent system. Further, modified Coulomb potentials and periodic boundary conditions can easily be integrated. One possible application is rapid, yet detailed methodological studies of the effects resulting from the various modified electrostatic interactions that are used regularly in computer simulations with explicit solvent molecules. As an example, we report the distance dependent Kirkwood g-factor and ion-dipole correlation functions of a solvated glycine zwitterion obtained with a simple cutoff, a shifted potential, two reaction field techniques, and Ewald summation. For the reaction fields and Ewald summation, conducting and adjusted dielectric boundary conditions are compared.

  12. Modeling sorption and diffusion of organic sorbate in hexadecyltrimethylammonium-modified clay nanopores - a molecular dynamics simulation study.

    PubMed

    Zhao, Qian; Burns, Susan E

    2013-03-19

    Organoclays are highly sorptive engineered materials that can be used as amendments in barrier systems or geosynthetic liners. The performance of confining and isolating the nonpolar organic contaminants by those barrier/lining systems is essentially controlled by the process of organic contaminant mass transport in nanopores of organoclays. In this article, we use molecular dynamics (MD) simulations to study the sorption and diffusion of organic sorbates in interlayers of sodium montmorillonite and hexadecyltrimethylammonium (HDTMA(+))-modified montmorillonite clays. Simulated system consisted of the clay framework, interlayer organic cation, water, and organic sorbate. Their interactions were addressed by the combined force field of ClayFF, constant-valence force field, and SPC water model. Simulation results indicated that in HDTMA coated clay nanopores, diffusion of nonpolar species benzene was slowed because they were subjected to influence of both the pore wall and the HDTMA surfactant. This suggested the nonpolar organic compound diffusion in organophilic clays can be affected by molecular size of diffusive species, clay pore size, and organic surfactant loading. Additionally, a model that connected the diffusion rate of organic compounds in the bulk organoclay matrix with macropores and nanopores was established. The impact of intercalated organic cations on the diffusion dominated mass transport of organic compounds yielded insight into the prediction of the apparent diffusion behavior of organic compounds in organic-modified clays.

  13. A statistical simulation model for field testing of non-target organisms in environmental risk assessment of genetically modified plants

    PubMed Central

    Goedhart, Paul W; van der Voet, Hilko; Baldacchino, Ferdinando; Arpaia, Salvatore

    2014-01-01

    Genetic modification of plants may result in unintended effects causing potentially adverse effects on the environment. A comparative safety assessment is therefore required by authorities, such as the European Food Safety Authority, in which the genetically modified plant is compared with its conventional counterpart. Part of the environmental risk assessment is a comparative field experiment in which the effect on non-target organisms is compared. Statistical analysis of such trials come in two flavors: difference testing and equivalence testing. It is important to know the statistical properties of these, for example, the power to detect environmental change of a given magnitude, before the start of an experiment. Such prospective power analysis can best be studied by means of a statistical simulation model. This paper describes a general framework for simulating data typically encountered in environmental risk assessment of genetically modified plants. The simulation model, available as Supplementary Material, can be used to generate count data having different statistical distributions possibly with excess-zeros. In addition the model employs completely randomized or randomized block experiments, can be used to simulate single or multiple trials across environments, enables genotype by environment interaction by adding random variety effects, and finally includes repeated measures in time following a constant, linear or quadratic pattern in time possibly with some form of autocorrelation. The model also allows to add a set of reference varieties to the GM plants and its comparator to assess the natural variation which can then be used to set limits of concern for equivalence testing. The different count distributions are described in some detail and some examples of how to use the simulation model to study various aspects, including a prospective power analysis, are provided. PMID:24834325

  14. A statistical simulation model for field testing of non-target organisms in environmental risk assessment of genetically modified plants.

    PubMed

    Goedhart, Paul W; van der Voet, Hilko; Baldacchino, Ferdinando; Arpaia, Salvatore

    2014-04-01

    Genetic modification of plants may result in unintended effects causing potentially adverse effects on the environment. A comparative safety assessment is therefore required by authorities, such as the European Food Safety Authority, in which the genetically modified plant is compared with its conventional counterpart. Part of the environmental risk assessment is a comparative field experiment in which the effect on non-target organisms is compared. Statistical analysis of such trials come in two flavors: difference testing and equivalence testing. It is important to know the statistical properties of these, for example, the power to detect environmental change of a given magnitude, before the start of an experiment. Such prospective power analysis can best be studied by means of a statistical simulation model. This paper describes a general framework for simulating data typically encountered in environmental risk assessment of genetically modified plants. The simulation model, available as Supplementary Material, can be used to generate count data having different statistical distributions possibly with excess-zeros. In addition the model employs completely randomized or randomized block experiments, can be used to simulate single or multiple trials across environments, enables genotype by environment interaction by adding random variety effects, and finally includes repeated measures in time following a constant, linear or quadratic pattern in time possibly with some form of autocorrelation. The model also allows to add a set of reference varieties to the GM plants and its comparator to assess the natural variation which can then be used to set limits of concern for equivalence testing. The different count distributions are described in some detail and some examples of how to use the simulation model to study various aspects, including a prospective power analysis, are provided.

  15. Monte Carlo simulation of inverse geometry x-ray fluoroscopy using a modified MC-GPU framework

    PubMed Central

    Dunkerley, David A. P.; Tomkowiak, Michael T.; Slagowski, Jordan M.; McCabe, Bradley P.; Funk, Tobias; Speidel, Michael A.

    2015-01-01

    Scanning-Beam Digital X-ray (SBDX) is a technology for low-dose fluoroscopy that employs inverse geometry x-ray beam scanning. To assist with rapid modeling of inverse geometry x-ray systems, we have developed a Monte Carlo (MC) simulation tool based on the MC-GPU framework. MC-GPU version 1.3 was modified to implement a 2D array of focal spot positions on a plane, with individually adjustable x-ray outputs, each producing a narrow x-ray beam directed toward a stationary photon-counting detector array. Geometric accuracy and blurring behavior in tomosynthesis reconstructions were evaluated from simulated images of a 3D arrangement of spheres. The artifact spread function from simulation agreed with experiment to within 1.6% (rRMSD). Detected x-ray scatter fraction was simulated for two SBDX detector geometries and compared to experiments. For the current SBDX prototype (10.6 cm wide by 5.3 cm tall detector), x-ray scatter fraction measured 2.8–6.4% (18.6–31.5 cm acrylic, 100 kV), versus 2.1–4.5% in MC simulation. Experimental trends in scatter versus detector size and phantom thickness were observed in simulation. For dose evaluation, an anthropomorphic phantom was imaged using regular and regional adaptive exposure (RAE) scanning. The reduction in kerma-area-product resulting from RAE scanning was 45% in radiochromic film measurements, versus 46% in simulation. The integral kerma calculated from TLD measurement points within the phantom was 57% lower when using RAE, versus 61% lower in simulation. This MC tool may be used to estimate tomographic blur, detected scatter, and dose distributions when developing inverse geometry x-ray systems. PMID:26113765

  16. Monte Carlo simulation of inverse geometry x-ray fluoroscopy using a modified MC-GPU framework

    NASA Astrophysics Data System (ADS)

    Dunkerley, David A. P.; Tomkowiak, Michael T.; Slagowski, Jordan M.; McCabe, Bradley P.; Funk, Tobias; Speidel, Michael A.

    2015-03-01

    Scanning-Beam Digital X-ray (SBDX) is a technology for low-dose fluoroscopy that employs inverse geometry x-ray beam scanning. To assist with rapid modeling of inverse geometry x-ray systems, we have developed a Monte Carlo (MC) simulation tool based on the MC-GPU framework. MC-GPU version 1.3 was modified to implement a 2D array of focal spot positions on a plane, with individually adjustable x-ray outputs, each producing a narrow x-ray beam directed toward a stationary photon-counting detector array. Geometric accuracy and blurring behavior in tomosynthesis reconstructions were evaluated from simulated images of a 3D arrangement of spheres. The artifact spread function from simulation agreed with experiment to within 1.6% (rRMSD). Detected x-ray scatter fraction was simulated for two SBDX detector geometries and compared to experiments. For the current SBDX prototype (10.6 cm wide by 5.3 cm tall detector), x-ray scatter fraction measured 2.8-6.4% (18.6-31.5 cm acrylic, 100 kV), versus 2.2-5.0% in MC simulation. Experimental trends in scatter versus detector size and phantom thickness were observed in simulation. For dose evaluation, an anthropomorphic phantom was imaged using regular and regional adaptive exposure (RAE) scanning. The reduction in kerma-area-product resulting from RAE scanning was 45% in radiochromic film measurements, versus 46% in simulation. The integral kerma calculated from TLD measurement points within the phantom was 57% lower when using RAE, versus 61% lower in simulation. This MC tool may be used to estimate tomographic blur, detected scatter, and dose distributions when developing inverse geometry x-ray systems.

  17. Optical simulation for imaging reconnaissance and intelligence sensors OSIRIS: High fidelity sensor simulation test bed; Modified user`s manual

    SciTech Connect

    Abernathy, M.F.; Puccetti, M.G.

    1988-01-04

    The OSIRIS program is an imaging optical simulation program which has been developed to predict the output of space-borne sensor systems. The simulation is radiometrically precise and includes highly realistic laser, atmosphere, and earth background models, as well as detailed models of optical components. This system was developed by Rockwell Power Services for the Los Alamos National Laboratory. It is based upon the LARC (Los Alamos Radiometry Code, also by Rockwell), and uses a similar command structure and 3d coordinate system as LARC. At present OSIRIS runs on the Cray I computer under the CTSS operating s stem, and is stored in the OSIRIS root directory on LANL CTSS mass storage.

  18. Reaction-Diffusion Model Simulations relevant to Modified Taylor-Couette Flow in Systems of Varying Length

    NASA Astrophysics Data System (ADS)

    Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

    2006-11-01

    Previously, we have observed a period-doubling cascade to chaos in Modified Taylor-Couette Flow with Hourglass Geometry. Such behavior had been predicted by The Reaction-Diffusion model simulations. The chaotic formation of Taylor-Vortex pair formation was restricted to a very narrow band about the waist of the hourglass. It was suggested that with increasing lengths of systems, the chaotic region would expand. We present a battery of simulations to determine the variation of the size of the chaotic region with length, seeking the transition to spatio- temporal chaos. Richard J. Wiener et al, Phys. Rev. E 55, 5489 (1997). H. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).

  19. Effects of Simulated Microstructure on the Creep Rupture of the Modified 9Cr-1Mo Steel

    NASA Astrophysics Data System (ADS)

    Hsiao, T. H.; Chen, T. C.; Jeng, S. L.; Chung, T. J.; Tsay, L. W.

    2016-10-01

    Microstructures of the heat-affected zone (HAZ) of a Gr. 91 steel weld were simulated to evaluate their effects on the creep life of the weld at elevated temperatures. The Ac1 and Ac3 temperatures of the Gr. 91 steel were determined by a dilatometer to be at 867 and 907 °C, respectively. An infrared heating system was employed to heat the samples to 860 (STOT), 900 (ICHAZ) and 940 °C (FGHAZ) for 1 min, followed by cooling to room temperature. The simulated specimens were then subjected to conventional post-weld heat treatment (PWHT) at 750 °C/2 h. After the PWHT, the tempered ICHAZ specimen had a shortest creep life among the specimens tested at 650 °C/60 MPa. Moreover, the simulated specimen heated to 860 °C (STOT) was more likely to fracture at 615 °C/80 MPa than others.

  20. Effects of Simulated Microstructure on the Creep Rupture of the Modified 9Cr-1Mo Steel

    NASA Astrophysics Data System (ADS)

    Hsiao, T. H.; Chen, T. C.; Jeng, S. L.; Chung, T. J.; Tsay, L. W.

    2016-08-01

    Microstructures of the heat-affected zone (HAZ) of a Gr. 91 steel weld were simulated to evaluate their effects on the creep life of the weld at elevated temperatures. The Ac1 and Ac3 temperatures of the Gr. 91 steel were determined by a dilatometer to be at 867 and 907 °C, respectively. An infrared heating system was employed to heat the samples to 860 (STOT), 900 (ICHAZ) and 940 °C (FGHAZ) for 1 min, followed by cooling to room temperature. The simulated specimens were then subjected to conventional post-weld heat treatment (PWHT) at 750 °C/2 h. After the PWHT, the tempered ICHAZ specimen had a shortest creep life among the specimens tested at 650 °C/60 MPa. Moreover, the simulated specimen heated to 860 °C (STOT) was more likely to fracture at 615 °C/80 MPa than others.

  1. Disability simulations and information: techniques for modifying the attitudes of elementary school music students.

    PubMed

    Colwell, C M; Thompson, L K; Berke, M K

    2001-01-01

    The purpose of this study was to determine the effect of different presentation formats (information and simulation) on the attitudes of elementary music students toward children with special needs. A questionnaire was initially administered to 11 elementary music classes (N = 198). Examination showed a 0.86 difference between highest and lowest rated disabilities on 6-point scale on the first administration. Females showed slightly more favorable attitudes than males for each of the 6 disability categories. Rank ordering indicated an identical ranking between genders with Learning Disabilities most accepted and Visual Impairments least accepted. Prior to the second administration, classes received different preparations: (a) information-based, (b) simulation-based, (c) contact-control. Results of the second administration showed no significant difference among treatment groups on gain scores with only a slight increase noted for the simulation-based treatment.

  2. Molecular dynamics simulation of secondary sorption behavior of montmorillonite modified by single chain quaternary ammonium cations.

    PubMed

    Zhao, Qian; Burns, Susan E

    2012-04-01

    Organoclays synthesized from single chain quaternary ammonium cations (QAC) ((CH(3))(3)NR(+)) exhibit different mechanisms for the sorption of nonpolar organic compounds as the length of the carbon chain is increased. The interaction between a nonpolar sorbate and an organoclay intercalated with small QACs has been demonstrated to be surface adsorption, while partitioning is the dominant mechanism in clays intercalated with long chain surfactants. This study presents the results of a molecular dynamics (MD) simulation performed to examine the sorption mechanisms of benzene in the interlayer of three organoclays with chain lengths ranging from 1 to 16 carbons: tetramethylammonium (TMA) clay; decyltrimethylammonium (DTMA) clay; and hexadecyltrimethylammonium (HDTMA) clay. The basis of the overall simulation was a combined force field of ClayFF and CVFF. In the simulations, organic cations were intercalated and benzene molecules were introduced to the interlayer, followed by whole system NPT and NVT time integration. Trajectories of all the species were recorded after the system reached equilibrium and subsequently analyzed. Simulation results confirmed that the arrangement of the surfactants controlled the sorption mechanism of organoclays. Benzene molecules were observed to interact directly with the clay surface in the presence of TMA cations, but tended to interact with the aliphatic chain of the HDTMA cation in the interlayer. The simulation provided insight into the nature of the adsorption/partitioning mechanisms in organoclays, and explained experimental observations of decreased versus increased uptake capacities as a function of increasing total organic carbon (TOC) for TMA clay and HDTMA clay, respectively. The transition of sorption mechanisms was also quantified with simulation of DTMA clay, with a chain length between that of TMA and HDTMA. Furthermore, this study suggested that at the molecular level, the controlling factor for the ultimate sorption

  3. An efficient modified Gabriel method for triangulating complex fractured media for multiphase flow simulations

    NASA Astrophysics Data System (ADS)

    Mustapha, Hussein; Rouxel-Labbé, Mael; Abbas, Hicham

    2013-10-01

    Fractured reservoirs and aquifers are complex domains where discrete fractures are internal constraining boundaries. The Delaunay triangulation of a fractured medium generally does not conform to the fracture boundaries and recovering the fracture elements may violate the Delaunay empty-circle (2D) criterion, which may lead to a low-quality triangulation. This paper presents a new approach based on the combined Gabriel and Delaunay methods. A modified Gabriel condition of edge-empty-circle is introduced. In a first stage, the fracture edges violating the modified Gabriel criterion are released and then followed by a Delaunay triangulation with the rest of the fracture constraints. The released fracture edges are approximated by the edges of the Delaunay triangles in a postprocessing stage. The final representation of the fractures might be slightly different, but a very accurate solution is always maintained. The method has the capability to generate fine grids and to offer an accurate and good-quality grid. Numerical examples are presented to assess the efficiency of the proposed method.

  4. Simulation of hailstorm event using Mesoscale Model MM5 with modified cloud microphysics scheme

    NASA Astrophysics Data System (ADS)

    Chatterjee, P.; Pradhan, D.; de, U. K.

    2008-11-01

    Mesoscale model MM5 (Version 3.5) with some modifications in the cloud microphysics scheme of Schultz (1995), has been used to simulate two hailstorm events over Gangetic Plain of West Bengal, India. While the first event occurred on 12 March 2003 and the hails covered four districts of the state of West Bengal, India, the second hailstorm event struck Srinikatan (22.65° N, 87.7° E) on 10 April 2006 at 11:32 UT and it lasted for 2 3 min. Both these events can be simulated, if the same modifications are introduced in the cloud microphysics scheme of Schultz. However, the original scheme of Schultz cannot simulate any hail. The results of simulation were compared with the necessary products of Doppler Weather Radar (DWR) located at Kolkata (22.57° N, 88.35° E). Model products like reflectivity, graupel and horizontal wind are compared with the corresponding products of DWR. The pattern of hail development bears good similarity between model output and observation from DWR, if necessary modifications are introduced in the model. The model output of 24 h accumulated rain from 03:00 UT to next day 03:00 UT has also been compared with the corresponding product of the satellite TRMM.

  5. Improved fast-rotating black hole evolution simulations with modified Baumgarte-Shapiro-Shibata-Nakamura formulation

    NASA Astrophysics Data System (ADS)

    Yo, Hwei-Jang; Cao, Zhoujian; Lin, Chun-Yu; Pan, Hsing-Po

    2015-07-01

    Different formulations of Einstein's equations used in numerical relativity can affect not only the stability but also the accuracy of numerical simulations. In the original Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation, the loss of the angular momentum, J , is non-negligible in highly spinning single black hole evolutions. This loss also appears, usually right after the merger, in highly spinning binary black hole simulations, The loss of J may be attributed to some unclear numerical dissipation. Reducing unphysical dissipation is expected to result in more stable and accurate evolutions. In the previous work [H.-J. Yo et al., Phys. Rev. D 86, 064027 (2012).] we proposed several modifications which are able to prevent black hole evolutions from the unphysical dissipation, and the resulting simulations are more stable than in the traditional BSSN formulation. Specifically, these three modifications (M1, M2, and M3) enhance the effects of stability, hyperbolicity, and dissipation of the formulation. We experiment further in this work with these modifications, and demonstrate that these modifications improve the accuracy and also effectively suppress the loss of J , particularly in the black hole simulations with an initially large ratio of J and a square of the ADM mass.

  6. A generalized force-modified potential energy surface for mechanochemical simulations

    SciTech Connect

    Subramanian, Gopinath; Mathew, Nithin; Leiding, Jeff

    2015-10-07

    We describe the modifications that a spatially varying external load produces on a Born-Oppenheimer potential energy surface (PES) by calculating static quantities of interest. The effects of the external loads are exemplified using electronic structure calculations (at the HF/6-31G{sup ∗∗} level) of two different molecules: ethane and hexahydro-1,3,5-trinitro-s-triazine (RDX). The calculated transition states and Hessian matrices of stationary points show that spatially varying external loads shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules are blueshifted with increasing compressive “pressure.” Some stationary points on the RDX-PES disappear under application of the external load, indicating the merging of an energy minimum with a saddle point.

  7. A generalized force-modified potential energy surface for mechanochemical simulations

    NASA Astrophysics Data System (ADS)

    Subramanian, Gopinath; Mathew, Nithin; Leiding, Jeff

    2015-10-01

    We describe the modifications that a spatially varying external load produces on a Born-Oppenheimer potential energy surface (PES) by calculating static quantities of interest. The effects of the external loads are exemplified using electronic structure calculations (at the HF/6-31G∗∗ level) of two different molecules: ethane and hexahydro-1,3,5-trinitro-s-triazine (RDX). The calculated transition states and Hessian matrices of stationary points show that spatially varying external loads shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules are blueshifted with increasing compressive "pressure." Some stationary points on the RDX-PES disappear under application of the external load, indicating the merging of an energy minimum with a saddle point.

  8. Generation and Computerized Simulation of Meshing and Contact of Modified Involute Helical Gears

    NASA Technical Reports Server (NTRS)

    Litvin, Faydor L.; Chen, Ningxin; Lu, Jian

    1995-01-01

    The design and generation of modified involute helical gears that have a localized and stable bearing contact, and reduced noise and vibration characteristics are described. The localization of the bearing contact is achieved by the mismatch of the two generating surfaces that are used for generation of the pinion and the gear. The reduction of noise and vibration will be achieved by application of a parabolic function of transmission errors that is able to absorb the almost linear function of transmission errors caused by gear misalignment. The meshing and contact of misaligned gear drives can be analyzed by application of computer programs that have been developed. The computations confirmed the effectiveness of the proposed modification of the gear geometry. A numerical example that illustrates the developed theory is provided.

  9. A generalized force-modified potential energy surface (G-FMPES) for mechanochemical simulations

    DOE PAGESBeta

    Subramanian, Gopinath; Mathew, Nithin; Leiding, Jeffery A.

    2015-10-05

    We describe the modifications that a spatially varying external load produces on a Born-Oppenheimer potential energy surface (PES) by calculating static quantities of interest. The effects of the external loads are exemplified using electronic structure calculations (at the HF/6-31G** level) of two different molecules: ethane and hexahydro-1,3,5-trinitro-s-triazine (RDX). The calculated transition states and The Hessian matrices of stationary points show that spatially varying external loads shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules aremore » blue-shifted with increasing compressive “pressure.” Some stationary points on the RDX-PES disappear under application of the external load, indicating the merging of an energy minimum with a saddle point.« less

  10. A generalized force-modified potential energy surface (G-FMPES) for mechanochemical simulations

    SciTech Connect

    Subramanian, Gopinath; Mathew, Nithin; Leiding, Jeffery A.

    2015-10-05

    We describe the modifications that a spatially varying external load produces on a Born-Oppenheimer potential energy surface (PES) by calculating static quantities of interest. The effects of the external loads are exemplified using electronic structure calculations (at the HF/6-31G** level) of two different molecules: ethane and hexahydro-1,3,5-trinitro-s-triazine (RDX). The calculated transition states and The Hessian matrices of stationary points show that spatially varying external loads shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules are blue-shifted with increasing compressive “pressure.” Some stationary points on the RDX-PES disappear under application of the external load, indicating the merging of an energy minimum with a saddle point.

  11. Accelerating All-Atom MD Simulations of Lipids Using a Modified Virtual-Sites Technique.

    PubMed

    Loubet, Bastien; Kopec, Wojciech; Khandelia, Himanshu

    2014-12-01

    We present two new implementations of the virtual sites technique which completely suppresses the degrees of freedom of the hydrogen atoms in a lipid bilayer allowing for an increased time step of 5 fs in all-atom simulations of the CHARMM36 force field. One of our approaches uses the derivation of the virtual sites used in GROMACS while the other uses a new definition of the virtual sites of the CH2 groups. Our methods is tested on a DPPC (no unsaturated chain), a POPC (one unsaturated chain), and a DOPC (two unsaturated chains) lipid bilayers. We calculate various physical properties of the membrane of our simulations with and without virtual sites and explain the differences and similarity observed. The best agreements are obtained for the GROMACS original virtual sites on the DOPC bilayer where we get an area per lipid of 67.3 ± 0.3 Å(2) without virtual sites and 67.6 ± 0.3 Å(2) with virtual sites. In conclusion the virtual-sites technique on lipid membranes is a powerful simulation tool, but it should be used with care. The procedure can be applied to other force fields and lipids in a straightforward manner.

  12. Measurements of thermal and healing properties of nanoclay modified asphalt binders using molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Baker, Dustin; Hawa, Takumi; Hossain, Zahid; Saha, Mrinal; Zaman, Musharraf

    2014-03-01

    A seven component molecular dynamics model has been developed to represent asphalt binder. The model has been developed to include the four major classes of molecules found in asphalt binders. The seven asphalt binder molecules were assembled with the Optimized Potentials for Liquid Simulations force field (OPLS) and the Large-scale atomic/molecular massively parallel simulator (LAMMPS) was used to carry out all simulations. Diffusion and density values were determined to validate individual molecules; all values were within acceptable range. Diffusion values were also determined for each molecule while present in the asphalt binder mixture. Density of the asphalt binder was determined to compare to experimental results. Values appear to follow the same trend as seen in experimental results and were closer to experimental results than other asphalt binder models. A glass transition temperature of 263.59K was determined using the density results at nineteen temperatures and was found to be in an acceptable range. A nano-clay model has also been developed using Clay force field and combined with the asphalt binder model. Also, we have investigated how the nano-clay impacts thermal and healing properties of the binder.

  13. Initial conditions for cosmological N-body simulations of the scalar sector of theories of Newtonian, Relativistic and Modified Gravity

    SciTech Connect

    Valkenburg, Wessel; Hu, Bin E-mail: hu@lorentz.leidenuniv.nl

    2015-09-01

    We present a description for setting initial particle displacements and field values for simulations of arbitrary metric theories of gravity, for perfect and imperfect fluids with arbitrary characteristics. We extend the Zel'dovich Approximation to nontrivial theories of gravity, and show how scale dependence implies curved particle paths, even in the entirely linear regime of perturbations. For a viable choice of Effective Field Theory of Modified Gravity, initial conditions set at high redshifts are affected at the level of up to 5% at Mpc scales, which exemplifies the importance of going beyond Λ-Cold Dark Matter initial conditions for modifications of gravity outside of the quasi-static approximation. In addition, we show initial conditions for a simulation where a scalar modification of gravity is modelled in a Lagrangian particle-like description. Our description paves the way for simulations and mock galaxy catalogs under theories of gravity beyond the standard model, crucial for progress towards precision tests of gravity and cosmology.

  14. Reconciling simulated melting and ground-state properties of metals with a modified embedded-atom method potential.

    PubMed

    Sushko, G B; Verkhovtsev, A V; Kexel, Ch; Korol, A V; Schramm, S; Solov'yov, A V

    2016-04-13

    We propose a modification of the embedded-atom method-type potential aiming at reconciling simulated melting and ground-state properties of metals by means of classical molecular dynamics. Considering titanium, magnesium, gold, and platinum as case studies, we demonstrate that simulations performed with the modified force field yield quantitatively correctly both the melting temperature of the metals and their ground-state properties. It is shown that the accounting for the long-range interatomic interactions noticeably affects the melting point assessment. The introduced modification weakens the interaction at interatomic distances exceeding the equilibrium one by a characteristic vibration amplitude defined by the Lindemann criterion, thus allowing for the correct simulation of melting, while keeping its behavior in the vicinity of the ground state minimum. The modification of the many-body potential has a general nature and can be applicable to metals with different characteristics of the electron structure as well as for many different molecular and solid state systems experiencing phase transitions. PMID:26977922

  15. Reconciling simulated melting and ground-state properties of metals with a modified embedded-atom method potential.

    PubMed

    Sushko, G B; Verkhovtsev, A V; Kexel, Ch; Korol, A V; Schramm, S; Solov'yov, A V

    2016-04-13

    We propose a modification of the embedded-atom method-type potential aiming at reconciling simulated melting and ground-state properties of metals by means of classical molecular dynamics. Considering titanium, magnesium, gold, and platinum as case studies, we demonstrate that simulations performed with the modified force field yield quantitatively correctly both the melting temperature of the metals and their ground-state properties. It is shown that the accounting for the long-range interatomic interactions noticeably affects the melting point assessment. The introduced modification weakens the interaction at interatomic distances exceeding the equilibrium one by a characteristic vibration amplitude defined by the Lindemann criterion, thus allowing for the correct simulation of melting, while keeping its behavior in the vicinity of the ground state minimum. The modification of the many-body potential has a general nature and can be applicable to metals with different characteristics of the electron structure as well as for many different molecular and solid state systems experiencing phase transitions.

  16. A Modified LBM Model for Simulating Gas Seepage in Fissured Coal Considering Klinkenberg Effects and Adsorbability-Desorbability

    NASA Astrophysics Data System (ADS)

    Tan, Yun-Liang; Teng, Gui-Rong; Zhang, Ze

    2010-01-01

    A modified Lattice-Boltzmann method is proposed by considering the Klinkenberg effect and adsorbability-desorbability for the purpose of simulating methane gas seepage in fissured coal. The results show that the Klinkenberg effect has a little influence on methane gas seepage in fissured coal, so it can be neglected in engineering computations for simplicity. If both the Klinkenberg effect and the adsorbability-desorbability are considered, the Klinkenberg influence on gas pressure decreases as the Darcy coefficient increases. It is found by gas drainage simulations that near a drainage hole, the effect of adsorption and desorption cannot be neglected, and the location of the drainage hole has a great influence on drainage efficient λ when the hole is just located at the mid-zone of the coal seam, λ is 0.691808; when the hole is excursion down to 1.0 m from the mid-zone of coal seam, λ decreases to 0.668631; when the hole is excursion up or down to 2.0 m from the mid-zone of coal seam, λ decreases to 0.632917. The simulations supply an effective approach for optimizing the gas drainage hole location.

  17. Stooped postures are modified by pretask walking in a simulated weed-pulling task.

    PubMed

    Hudson, D S; Copeland, J L; Hepburn, C G; Doan, J B

    2014-01-01

    Seasonal agricultural workers are hired in some sectors for intermittent manual weed removal, a stoop and grasp harvesting task likely similar to those associated with the high prevalence of musculoskeletal disorders in agriculture. Evaluation of this task in an experimental situation would be useful for identifying and controlling musculoskeletal injury risks, presuming a valid experimental model of the task can be created. The purpose of the present study was to examine how a relevant work-related task, namely prolonged walking, altered the biomechanics of manual weed removal in a laboratory setting. Preliminary field assessments informed the development and analysis of a simulated manual weed removal with two separate conditions: not primed, where 11 participants (4 female, mean age 21.6 years) manually removed a simulated weed six times, and primed, where 23 participants (13 female, mean age 22.1 years) walked 1600 m prior to manually removing the same simulated weed six successive times. Segment end point markers and experimental motion capture were used to determine hip, knee, and ankle angles, as well as toe-target proximity, during weed removal. Significant differences between primed and not primed participants were found for angular displacement at the ankle (t(32) = 5.08, P < .001) and toe-target proximity (t(32) = 2.78, P = .008), where primed participants had increased ankle flexion and a greater distance to the weed, leading to decreased trunk flexion during the harvesting task. These findings suggest that priming can positively influence whole-body postures for manual weed removal.

  18. Simulation of Ion Motion in FAIMS through Combined Use of SIMION and Modified SDS

    SciTech Connect

    Prasad, Satendra; Tang, Keqi; Manura, David; Papanastasiou, Dimitris; Smith, Richard D.

    2009-11-01

    Over the years, the use of Field Asymmetric Ion Mobility Spectrometry (FAIMS) has grown with applications spanning from explosives detection to separation of complex biological mixtures. Although, the principles of ion separation in FAIMS is understood and comprehensively characterized, little effort has been made in developing commercially available computational tools that can simulate ion motion in FAIMS. Such a tool could be of great value for refining theory, optimizing the performance of the instrument for specific applications, and in modeling the fringe-fields caused by rf decay at the entrance and exit of FAIMS which can significantly affect ion transmission. An algorithm using SIMIONTM as its core structure was developed in this study to realistically compute ion trajectory at different ratios of electric field to buffer gas number density (E/N). The E/N can vary from a few Td to ~80 Td in FAIMS as created by an asymmetric square waveform. The Statistical Diffusion Simulation (SDS) model was further incorporated in the algorithm to simulate the ion diffusion in the FAIMS gap. The algorithm was validated using a FAIMS analyzer model similar to the Sionex Corporation model SVAC in terms of its dimensions and geometry. Hydroxyproline and Leucine ions with similar reduced mobility Ko (2.17 and 2.18 cm2.V-1.s-1, respectively) were used as model ions to test the new algorithm and demonstrate the effects of gas flow and waveform (voltage pulse amplitude and frequency) on peak shape and ion current transmission. Simulation results from three ion types: O2-(H2O)3, (A type), (C3H6O)2H+ (B type), and (C12H24O)2H+ (C type) were then compared with the experimental data (available in the literature). The SIMION-SDS-Field Dependent Mobility Calculation (FDMC) algorithm provided good agreement with experimental measurements of the ion peak position in FAIMS compensation voltage (CV) spectrum, peak width, and the ion transmission over a broad range of E/N.

  19. Mechanisms of CPB Modified Zeolite on Mercury Adsorption in Simulated Wastewater.

    PubMed

    Liu, Jiang; Huang, Hui; Huang, Rong; Zhang, Jinzhong; Hao, Shuoshuo; Shen, Yuanyuan; Chen, Hong

    2016-06-01

    A systematic study was carried out to analyze the effects of mercury(II) adsorption by surface modified zeolite (SMZ) and adsorption mechanism. Cetylpyridinium bromide (CPB) was used to prepare SMZ. The characterization methods by means of powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM) showed that both the surface and internal zeolite were covered with CPB molecules, but the main binding sites were surface. Results showed that the organic carbon and cation exchange capacity of the SMZ were 7.76 times and 4.22 times higher than those of natural zeolite (NZ), respectively. Zeta potentials before and after modification were measured at -7.80 mV and -30.27 mV, respectively. Moreover, the saturation adsorptive capacity of SMZ was 16.35 times higher than NZ in mercury-containing wastewater. The possible mechanisms of mercury elimination were surface adsorption, hydrophobic interaction, ion exchange, electricity neutralization. The adsorption process was affected little by competitive ions.

  20. Finger milling-cutter CNC generating hypoid pinion tooth surfaces based on modified-roll method and machining simulation

    NASA Astrophysics Data System (ADS)

    Li, Genggeng; Deng, Xiaozhong; Wei, Bingyang; Lei, Baozhen

    2011-05-01

    The two coordinate systems of cradle-type hypoid generator and free-form CNC machine tool by application disc milling-cutter to generate hypoid pinion tooth surfaces based on the modified-roll method were set up, respectively, and transformation principle and method for machine-tool settings between the two coordinate systems was studied. It was presented that finger milling-cutter was mounted on imagined disc milling-cutter and its motion was controlled directly by CNC shafts to replace disc milling-cutter blades effective cutting motion. Finger milling-cutter generation accomplished by ordered circular interpolation was determined, and interpolation center, starting and ending were worked out. Finally, a hypoid pinion was virtually machined by using CNC machining simulation software VERICUT.

  1. Finger milling-cutter CNC generating hypoid pinion tooth surfaces based on modified-roll method and machining simulation

    NASA Astrophysics Data System (ADS)

    Li, Genggeng; Deng, Xiaozhong; Wei, Bingyang; Lei, Baozhen

    2010-12-01

    The two coordinate systems of cradle-type hypoid generator and free-form CNC machine tool by application disc milling-cutter to generate hypoid pinion tooth surfaces based on the modified-roll method were set up, respectively, and transformation principle and method for machine-tool settings between the two coordinate systems was studied. It was presented that finger milling-cutter was mounted on imagined disc milling-cutter and its motion was controlled directly by CNC shafts to replace disc milling-cutter blades effective cutting motion. Finger milling-cutter generation accomplished by ordered circular interpolation was determined, and interpolation center, starting and ending were worked out. Finally, a hypoid pinion was virtually machined by using CNC machining simulation software VERICUT.

  2. Simulation Of Wave Function And Probability Density Of Modified Poschl Teller Potential Derived Using Supersymmetric Quantum Mechanics

    SciTech Connect

    Angraini, Lily Maysari; Suparmi,; Variani, Viska Inda

    2010-12-23

    SUSY quantum mechanics can be applied to solve Schrodinger equation for high dimensional system that can be reduced into one dimensional system and represented in lowering and raising operators. Lowering and raising operators can be obtained using relationship between original Hamiltonian equation and the (super) potential equation. In this paper SUSY quantum mechanics is used as a method to obtain the wave function and the energy level of the Modified Poschl Teller potential. The graph of wave function equation and probability density is simulated by using Delphi 7.0 programming language. Finally, the expectation value of quantum mechanics operator could be calculated analytically using integral form or probability density graph resulted by the programming.

  3. Fatigue and cyclic deformation behaviour of surface-modified titanium alloys in simulated physiological media.

    PubMed

    Leinenbach, Christian; Eifler, Dietmar

    2006-03-01

    In this investigation, the cyclic deformation behaviour of the binary titanium alloys Ti-6Al-4V and Ti-6Al-7Nb was characterized in axial stress-controlled constant amplitude and load increase tests as well as in rotating bending tests. The influence of different clinically relevant surface treatments (polishing, corundum grit blasting, thermal and anodic oxidizing) on the fatigue behaviour was investigated. All tests were realized in oxygen-saturated Ringer's solution. The cyclic deformation behaviour was characterized by mechanical hysteresis measurements. In addition, the change of the free corrosion potential and the corrosion current during testing in simulated physiological media indicated surface damages such as slip bands, intrusions and extrusions or finally microcracks. Microstructural changes on the specimen surfaces were examined by scanning electron microscopy (SEM). PMID:16140373

  4. Numerical simulation of damage in cementitious materials using a modified approach to the multicutting technique

    NASA Astrophysics Data System (ADS)

    Saad, Pascinthe

    The Linear Elastic Fracture Mechanics approach widely used for damage characterization of ductile materials cannot be accurately used for cementitious composites which undergo a substantial amount of localized microcracking prior to peak load. The Multicutting Technique offers a reasonably sound experimental means of obtaining the size of the damage zone for cementitious, concrete-like materials. The method, however, has many theoretical deficiencies and its sensitivity to experimental errors renders it occasionally unpredictable. The presented work is an attempt to study these deficiencies while providing a means of obtaining the size of the damage zone through the numerical simulation of the Multicutting Technique. Three modifications were made in an attempt to circumvent the deficiencies of the original technique: (1) Nonlinear axial elements are used to represent the localized strain-softening occurring near the cracktip in the introduced numerically based model. (2) A nonlinear crack opening profile is obtained rather than the linear relation assumed in the original theory. This crack opening profile is then used to obtain more adequate cohesive stress relations. (3) The stress redistribution factor is obtained and is found to be a function of the crack length as well as the location where the cut is performed. Results of the introduced model were found to be mesh and loading pattern independent, provided an adequately fine mesh is selected (size of elements < characteristic length) and a relatively small time step is used. Once the dependency on numerical parameters is eliminated with the proper choice of mesh configuration, time step and cohesive stress distribution function, the numerically simulated P-CMOD curve was very similar to the experimentally obtained curve. This similarity tends to validate, to a certain extent, the presented model as a sound, numerically based, means of assessing damage in cementitious composites.

  5. Brain without mind: Computer simulation of neural networks with modifiable neuronal interactions

    NASA Astrophysics Data System (ADS)

    Clark, John W.; Rafelski, Johann; Winston, Jeffrey V.

    1985-07-01

    Aspects of brain function are examined in terms of a nonlinear dynamical system of highly interconnected neuron-like binary decision elements. The model neurons operate synchronously in discrete time, according to deterministic or probabilistic equations of motion. Plasticity of the nervous system, which underlies such cognitive collective phenomena as adaptive development, learning, and memory, is represented by temporal modification of interneuronal connection strengths depending on momentary or recent neural activity. A formal basis is presented for the construction of local plasticity algorithms, or connection-modification routines, spanning a large class. To build an intuitive understanding of the behavior of discrete-time network models, extensive computer simulations have been carried out (a) for nets with fixed, quasirandom connectivity and (b) for nets with connections that evolve under one or another choice of plasticity algorithm. From the former experiments, insights are gained concerning the spontaneous emergence of order in the form of cyclic modes of neuronal activity. In the course of the latter experiments, a simple plasticity routine (“brainwashing,” or “anti-learning”) was identified which, applied to nets with initially quasirandom connectivity, creates model networks which provide more felicitous starting points for computer experiments on the engramming of content-addressable memories and on learning more generally. The potential relevance of this algorithm to developmental neurobiology and to sleep states is discussed. The model considered is at the same time a synthesis of earlier synchronous neural-network models and an elaboration upon them; accordingly, the present article offers both a focused review of the dynamical properties of such systems and a selection of new findings derived from computer simulation.

  6. Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes: A Generalized Modified Poisson-Nernst-Planck Model

    SciTech Connect

    Wang, Hainan; Thiele, Alexander; Pilon, Laurent

    2013-11-15

    This paper presents a generalized modified Poisson–Nernst–Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |zi| of either ion species. By contrast, the ion diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τCV and the “RC time scale” τRC corresponding to the characteristic time of ions’ electrodiffusion. For τRC ← τCV, quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τRC → τCV, the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.

  7. Speech intelligibility and speech quality of modified loudspeaker announcements examined in a simulated aircraft cabin.

    PubMed

    Pennig, Sibylle; Quehl, Julia; Wittkowski, Martin

    2014-01-01

    Acoustic modifications of loudspeaker announcements were investigated in a simulated aircraft cabin to improve passengers' speech intelligibility and quality of communication in this specific setting. Four experiments with 278 participants in total were conducted in an acoustic laboratory using a standardised speech test and subjective rating scales. In experiments 1 and 2 the sound pressure level (SPL) of the announcements was varied (ranging from 70 to 85 dB(A)). Experiments 3 and 4 focused on frequency modification (octave bands) of the announcements. All studies used a background noise with the same SPL (74 dB(A)), but recorded at different seat positions in the aircraft cabin (front, rear). The results quantify speech intelligibility improvements with increasing signal-to-noise ratio and amplification of particular octave bands, especially the 2 kHz and the 4 kHz band. Thus, loudspeaker power in an aircraft cabin can be reduced by using appropriate filter settings in the loudspeaker system. PMID:25183056

  8. Speech intelligibility and speech quality of modified loudspeaker announcements examined in a simulated aircraft cabin.

    PubMed

    Pennig, Sibylle; Quehl, Julia; Wittkowski, Martin

    2014-01-01

    Acoustic modifications of loudspeaker announcements were investigated in a simulated aircraft cabin to improve passengers' speech intelligibility and quality of communication in this specific setting. Four experiments with 278 participants in total were conducted in an acoustic laboratory using a standardised speech test and subjective rating scales. In experiments 1 and 2 the sound pressure level (SPL) of the announcements was varied (ranging from 70 to 85 dB(A)). Experiments 3 and 4 focused on frequency modification (octave bands) of the announcements. All studies used a background noise with the same SPL (74 dB(A)), but recorded at different seat positions in the aircraft cabin (front, rear). The results quantify speech intelligibility improvements with increasing signal-to-noise ratio and amplification of particular octave bands, especially the 2 kHz and the 4 kHz band. Thus, loudspeaker power in an aircraft cabin can be reduced by using appropriate filter settings in the loudspeaker system.

  9. Improvement of hydrologic simulations in CLM4 by modified soil properties

    NASA Astrophysics Data System (ADS)

    Du, E.; Di Vittorio, A. V.; Collins, W.

    2014-12-01

    Runoff and soil moisture biases were found by comparing fully coupled CCSM4 simulations and observations. The CLM underestimated runoff in the areas where soils have high clay content, but overestimated in the areas covered by volcanic ash soils (i.e. Andisols). Clayey soils tend to exhibit aggregation structure that prone to form macropores. Macropores enable water to flow through unsaturated soil more rapidly than it would in a soil matrix defined by Darcy's law. The existence of macropores increases effective hydraulic conductivity, thus decreases water content in the surface soils. Without this mechanism, CLM4 may overestimate evapotranspiration and in turn underestimate runoff by retaining too much plant available water. We hypothesize that lack of macropore flow mechanism is partially responsible for the underestimation and insufficient soil porosity representation is associated with overestimation. Andisols are soils formed in volcanic ash with very high porosity (often >0.60 cm3 cm-3) and water holding capacity. The mineral soil porosity is defined by sand content in CLM and is much lower than it would have been for Andisols. CLM may retain insufficient plant available water and underestimate evapotranspiration therefore partitioning too much to runoff. We propose more detailed soil maps in the CLM to improve the representations of soil physical properties that are critical in the terrestrial water modeling.

  10. Release of a Poorly Soluble Drug from Hydrophobically Modified Poly (Acrylic Acid) in Simulated Intestinal Fluids

    PubMed Central

    Knöös, Patrik

    2015-01-01

    A large part of new pharmaceutical substances are characterized by a poor solubility and high hydrophobicity, which might lead to a difference in drug adsorption between fasted and fed patients. We have previously evaluated the release of hydrophobic drugs from tablets based on Pemulen TR2 and showed that the release can be manipulated by adding surfactants. Here we further evaluate the possibility to use Pemulen TR2 in controlled release tablet formulations containing a poorly soluble substance, griseofulvin. The release is evaluated in simulated intestinal media that model the fasted state (FaSSIF medium) or fed state (FeSSIF). The rheology of polymer gels is studied in separate experiments, in order to gain more information on possible interactions. The release of griseofulvin in tablets without surfactant varied greatly and the slowest release were observed in FeSSIF. Addition of SDS to the tablets eliminated the differences and all tablets showed a slow linear release, which is of obvious relevance for robust drug delivery. Comparing the data from the release studies and the rheology experiment showed that the effects on the release from the different media could to a large extent be rationalised as a consequence of the interactions between the polymer and the surfactants in the media. The study shows that Pemulen TR2 is a candidate for controlled release formulations in which addition of surfactant provides a way to eliminate food effects on the release profile. However, the formulation used needs to be designed to give a faster release rate than the tablets currently investigated. PMID:26473964

  11. Bio-Templated Growth of Bone Minerals from Modified Simulated Body Fluid on Nanofibrous Decellularized Natural Tissues.

    PubMed

    Yang, Mingying; Wang, Jie; Zhu, Ye; Mao, Chuanbin

    2016-04-01

    Small intestine submucosal (SIS) membrane used in this study is a decellularized, naturally occurring nanofibrous scaffold derived from a submucosal layer of porcine small intestine. It is predominantly composed of type I collagen fibers. Here we studied the bio-templated growth of hydroxylapatite (HAP) bone minerals on the SIS membrane from a modified simulated body fluid (1.5 SBF) at the body temperature, namely, under a near-physiological condition, in order to evaluate its bone bioactivity, the capability of the membrane in bonding with bone tissue once implanted in vivo. Minute HAP crystals were successfully nucleated on the SIS membranes from 1.5 SBF at the body temperature. The crystals were preferentially nucleated along the collagen fibers constituting the SIS membranes. HAP was the major crystalline mineral phase formed during the whole period of time and a minor crystalline phase of tricalcium phosphate (TCP) appeared after the membranes were incubated for 96 h. We also found that the mineralization for 8 h most significantly promoted the osteogenic differentiation of rat mesenchymal stem cells (MSCs) by evaluating the formation of osteogenic markers in MSCs including alkaline phosphatase (early stage marker) as well as osteocalcin and osteopontin (late stage markers). Hence, SIS membranes show excellent bone bioactivity and once mineralized, can significantly promote the osteogenic differentiation of MSCs. PMID:27301201

  12. A new approach for the simulation of ESR lineshapes over a large range of correlation times

    NASA Astrophysics Data System (ADS)

    Eviatar, H.; van Faassen, E.; Levine, Y. K.

    1992-07-01

    A new approach for the simulation of ESR lineshapes over a range of correlation times extending from the Redfield limit to the rigid limit is described. The use of a separable operator for the dynamics of a spin label in a uniaxial liquid crystal ("Kangaroo dynamics") allows an algebraic solution of the stochastic Liouville equation. This procedure avoids the numerical instability resulting from clustering of eigenvalues inherent in the conventional solution using an eigenfunction expansion.

  13. Quality of fresh retail pork cuts stored in modified atmosphere under temperature conditions simulating export to distant markets.

    PubMed

    McMullen, L M; Stiles, M E

    1994-01-01

    The effect of storage temperature on microbial and sensory quality of retail cuts of pork was determined on samples stored under temperature regimens designed to simulate conditions that could be encountered in accessing distant markets with retail-ready product. Samples were packaged in modified atmosphere with 100% CO(2) and <200 ppm O(2) in plastic film with extremely low gas transmission rates. All samples were stored at -1·5°C for three weeks. Reference samples were held at -1·5°C for the duration of the study; experimental samples were transferred to 4°C (-1·5 4° C ) or 7°C (-1· 517° C ) and analyzed for microbial content and sebsory attributes including appearance, confinement and meat odours. Storage life of reference samples at -1·5°C was seven weeks before rejection for loss of acceptable appearance. With transfer of samples to 4 and 7°C after three weeks at -1·5°C, samples remained acceptable for retail sale for two weeks and one week, restpectively. The microbial flora was dominated by lactic acid bacteria under all three storage conditions. Appearance of the cuts was the principal criterion limiting storage life. Discoloration of the meat was not a problem in this study, but purge and odour, including sour and sulphur notes, became a problem with time. The study indicated that export of retail-ready pork cuts to distant markets with a three-week time for delivery to market at -1·5°C can be achieved with one to two weeks of marketing time at retail market at 4 to 7°C.

  14. Simulated passage through a modified Kaplan turbine pressure regime: A supplement to "Laboratory Studies of the Effects of Pressure and Dissolved Gas Supersaturation on Turbine-Passed Fish"

    SciTech Connect

    Abernethy, C. S.; Amidan, B. G.; Cada, G. F.

    2002-04-01

    A previous test series (Abernethy et al. 2001) evaluated the effects of passage through a Kaplan turbine under the “worst case” pressure conditions. For this series of tests, pressure changes were modified to simulate passage through a Kaplan turbine under a more “fish-friendly” mode of operation. The results were compared to results from Abernethy et al. (2001). These data indicate that altered operating conditions that raise the nadir (low point) of the turbine passage pressure regime could reduce the injury and mortality rates of fish during turbine passage. Fall Chinook salmon were not injured or killed when subjected to the modified pressure scenario. Bluegills were more sensitive to pressure effects than fall Chinook salmon, but injury and mortality rates were lower under the modified Kaplan pressure regime. This improvement was particularly significant among fish that were acclimated to greater water pressures (traveling at greater depth).

  15. Experiment and numerical simulation on cross-die forming of SUS304 metastable austenitic stainless using a modified Johnson-Cook model

    NASA Astrophysics Data System (ADS)

    Li, Xifeng; Ding, Wei; Ye, Liyan; Chen, Jun

    2013-12-01

    True stress-strain curves of SUS304 metastable austenitic stainless steel at various strain rates were fitted by a modified Johnson-Cook material model. The effect of blank-holder force on Cross-die forming of SUS304 stainless steel was studied. The forming process was also simulated by the software Marc based on this model. Major strain distribution, thickness distribution and load-displacement were compared between experiment and simulation. The results indicated the modified Johnson-Cook model could well predict the deformation behavior of SUS304 stainless steel. The martensitie volume fraction at different positions of the formed part was in good agreement with what can be expected.

  16. 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)

  17. Aluminum oxide as a dual-functional modifier of Ni-based anodes of solid oxide fuel cells for operation on simulated biogas

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Wang, Wei; Ran, Ran; Tade, Moses O.; Shao, Zongping

    2014-12-01

    Al2O3 and SnO2 additives are introduced into the Ni-YSZ cermet anode of solid oxide fuel cells (SOFCs) for operation on simulated biogas. The effects of incorporating Al2O3/SnO2 on the electrical conductivity, morphology, coking resistance and catalytic activity for biogas reforming of the cermet anode are systematically studied. The electrochemical performance of the internal reforming SOFC is enhanced by introducing an appropriate amount of Al2O3 into the anode, but it becomes worse with excess alumina addition. For SnO2, a negative effect on the electrochemical performance is demonstrated, although the coking resistance of the anode is improved. For fuel cells operating on biogas, stable operation under a polarization current for 130 h at 750 °C is achieved for a cell with an Al2O3-modified anode, while cells with unmodified or SnO2-modified Ni-YSZ anodes show much poorer stability under the same conditions. The improved performance of the cell with the Al2O3-modified anode mainly results from the suppressed coking and sintering of the anode and from the formation of NiAl2O4 in the unreduced anode. In sum, modifying the anode with Al2O3 may be a useful and facile way to improve the coking resistance and electrochemical performance of the nickel-based cermet anodes for SOFCs.

  18. Application of a modified conceptual rainfall-runoff model to simulation of groundwater level in an undefined watershed.

    PubMed

    Hong, Nian; Hama, Takehide; Suenaga, Yuichi; Aqili, Sayed Waliullah; Huang, Xiaowu; Wei, Qiaoyan; Kawagoshi, Yasunori

    2016-01-15

    Groundwater level simulation models can help ensure the proper management and use of urban and rural water supply. In this paper, we propose a groundwater level tank model (GLTM) based on a conceptual rainfall-runoff model (tank model) to simulate fluctuations in groundwater level. The variables used in the simulations consist of daily rainfall and daily groundwater level, which were recorded between April 2011 and March 2015 at two representative observation wells in Kumamoto City, Japan. We determined the best-fit model parameters by root-mean-square error through use of the Shuffled Complex Evolution-University of Arizona algorithm on a simulated data set. Calibration and validation results were evaluated by their coefficients of determination, Nash-Sutcliffe efficiency coefficients, and root-mean-square error values. The GLTM provided accurate results in both the calibration and validation of fluctuations in groundwater level. The split sample test results indicate a good reliability. These results indicate that this model can provide a simple approach to the accurate simulation of groundwater levels.

  19. A critical evaluation of fasted state simulating gastric fluid (FaSSGF) that contains sodium lauryl sulfate and proposal of a modified recipe.

    PubMed

    Aburub, Aktham; Risley, Donald S; Mishra, Dinesh

    2008-01-22

    The aim of this work is to evaluate one of the most commonly used fasted state simulating gastric fluids (FaSSGFs), which contains sodium lauryl sulfate (SLS) (FaSSGF(SLS)), and propose a more appropriate surfactant concentration. Surface tension studies clearly show that the critical micelle concentration (CMC) of SLS in the relevant media (a media whose pH and sodium chloride concentration are representative of physiological conditions) is significantly lower (p<0.05) than 8.67 mM, which is the SLS concentration in FaSSGF(SLS). The CMC of SLS in the relevant media was determined to be 1.75 mM. Based on this a modified recipe is proposed in which the concentration of SLS is sufficient to achieve a surface tension similar to that in vivo without causing artificial micellar solubilization. Solubility, intrinsic dissolution, and GastroPlus modeling studies are presented to support and give rationale for the modified recipe. In addition, a comparison between the modified recipe and other FaSSGFs reported in the literature is made.

  20. Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles' radii

    NASA Astrophysics Data System (ADS)

    Bolghasi, Alireza; Ghadimi, Parviz; Chekab, Mohammad A. Feizi

    2016-09-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz-Kirchhoff-Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall-Novarini model and optimized HKF method. The extended Hall-Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  1. Three-dimensional printed prototypes refine the anatomy of post-modified Norwood-1 complex aortic arch obstruction and allow presurgical simulation of the repair.

    PubMed

    Kiraly, Laszlo; Tofeig, Magdi; Jha, Neerod Kumar; Talo, Haitham

    2016-02-01

    Three-dimensional (3D) printed prototypes of malformed hearts have been used for education, communication, presurgical planning and simulation. We present a case of a 5-month old infant with complex obstruction at the neoaortic to transverse arch and descending aortic junction following the neonatal modified Norwood-1 procedure for hypoplastic left heart syndrome. Digital 3D models were created from a routine 64-slice CT dataset; then life-size solid and magnified hollow models were printed with a 3D printer. The solid model provided further insights into details of the anatomy, whereas the surgical approach and steps of the operation were simulated on the hollow model. Intraoperative assessment confirmed the anatomical accuracy of the 3D models. The operation was performed in accordance with preoperative simulation: sliding autologous flaps achieved relief of the obstruction without additional patching. Knowledge gained from the models fundamentally contributed to successful outcome and improved patient safety. This case study presents an effective use of 3D models in exploring complex spatial relationship at the aortic arch and in simulation-based planning of the operative procedure.

  2. Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles' radii

    NASA Astrophysics Data System (ADS)

    Bolghasi, Alireza; Ghadimi, Parviz; Chekab, Mohammad A. Feizi

    2016-08-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz-Kirchhoff-Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall-Novarini model and optimized HKF method. The extended Hall-Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  3. Impact of MODIS and AIRS total precipitable water on modifying the vertical shear and Hurricane Emily simulations

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Chin; Chen, Shu-Hua; Chien, Fang-Ching

    2011-01-01

    The impact of retrieved total precipitable water (TPW) from Moderate Resolution Imaging Spectrometer (MODIS) infrared (IR), MODIS near-infrared (NIR), and the combined Atmospheric Infrared Sounder (AIRS)-IR and Advanced Microwave Sounding Unit-Microwave channels on simulations of Hurricane Emily was assessed and compared using the Weather Research and Forecasting model and its three-dimensional variation data assimilation (3D-Var) system. After assimilating MODIS IR TPW, the model clearly better reproduced storm tracking, intensity, and the 10 m wind field, while the improvement was limited or nil when assimilating either MODIS NIR TPW or AIRS TPW. After the data assimilation of MODIS IR TPW, a positive moisture increment was present to the east of the simulated storm in 3D-Var analysis (i.e., initial conditions). The positive TPW increment enhanced a convective cloud, which was also observed by satellites. The convective cloud effectively modulated the height and wind fields, resulting in a weakening of the vertical wind shear (VWS) over the region. The weak VWS band was then advected to the north of the storm, preventing the storm from attaching to the strong VWS zone located between 20°N and 30°N. There was no such positive moisture increment, convective cloud, or weak VWS band occurring to the east of the simulated storm in the other data assimilation experiments. This explains why the simulated storm intensified with assimilation of MODIS IR TPW but not for the other experiments.

  4. The Use of Social Simulation Game in an Attempt to Modify White Suburban Adolescents' Attitudes Toward Blacks.

    ERIC Educational Resources Information Center

    Lovelace, Juan Carlos.

    An inter-racial simulation game was administered to 6 ninth grade social studies classes in a desegregated upper middle class suburban junior high school to determine how the game would affect the white students racial attitudes and the self perceived race relations within the classrooms. There were two experimental treatments, the Sunrise game,…

  5. Modified Slim-Disk Model Based on Radiation-Hydrodynamic Simulation Data: The Conflict between Outflow and Photon Trapping

    NASA Astrophysics Data System (ADS)

    Takeuchi, Shun; Mineshige, Shin; Ohsuga, Ken

    2009-08-01

    Photon trapping and outflow are two key physics issues associated with supercritical accretion flow. We investigated the conflict between these two processes based on two-dimensional radiation-hydrodynamic (RHD) simulation data, and constructed a simplified (radially) one-dimensional model. Mass loss due to outflow, which is not considered in the slim-disk model, reduces the surface density of the flow, and if very significantly, it can totally suppress the photon-trapping effects. If photon trapping is very significant, conversely, outflow can be suppressed because the radiation-pressure force is reduced. To see what actually occurs, we examined the RHD simulation data and evaluated the accretion and outflow rates as functions of the radius. We have found that the accretion rate monotonically decreases, while the outflow rate increases, as the radius decreases. However, the accretion remains constant at small radii, inside several Schwarzschild radii, since the outflow is suppressed by photon trapping effects. To understand the conflict between the photon trapping and outflow in a simpler way, we modeled the radial distribution of the accretion rate from our simulation data, and built up a new (radially) one-dimensional model, which is similar to the slim-disk model, but incorporates mass loss effects due to the outflow. We find that the surface density (and, hence, the optical depth) is greatly reduced even inside the trapping radius, compared to the case without outflow, whereas the effective temperature distribution hardly changes. That is, the emergent spectra do not sensitively depend on the amount of mass outflow. We conclude that the slim-disk approach is valid for interpreting observations, even if the outflow is taken into account. The observational implications of our findings are briefly discussed in relation to ultra-luminous X-ray sources.

  6. Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: model development and initial evaluation.

    PubMed

    Zhang, Xuesong; Izaurralde, R César; Arnold, Jeffrey G; Williams, Jimmy R; Srinivasan, Raghavan

    2013-10-01

    Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land-atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land-atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes. PMID:23859899

  7. Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: model development and initial evaluation.

    PubMed

    Zhang, Xuesong; Izaurralde, R César; Arnold, Jeffrey G; Williams, Jimmy R; Srinivasan, Raghavan

    2013-10-01

    Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land-atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land-atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes.

  8. Corrosion behavior of chromium and oxygen plasma-modified magnesium in sulfate solution and simulated body fluid

    NASA Astrophysics Data System (ADS)

    Xu, Ruizhen; Wu, Guosong; Yang, Xiongbo; Zhang, Xuming; Wu, Zhengwei; Sun, Guangyong; Li, Guangyao; Chu, Paul K.

    2012-08-01

    Because of the unique mechanical properties and biocompatibility, magnesium and its alloys have large potential as lightweight structural materials in the industry in addition to being naturally degradable and resorbable biomaterials. However, their corrosion resistance is usually inadequate especially in an aqueous environment. In this work, pure magnesium is implanted with chromium and oxygen by plasma immersion ion implantation (PIII) and the corrosion behavior is systematically investigated in simulated body fluid and sodium sulfate solution by polarization tests and electrochemical impedance spectroscopy. Our results reveal that chromium and oxygen ion-implanted magnesium have a lower corrosion rate and exhibit less pitting corrosion in the two solutions.

  9. Simulation of Streamflow in a Discontinuous Permafrost Environment Using a Modified First-order, Nonlinear Rainfall-runoff Model

    NASA Astrophysics Data System (ADS)

    Bolton, W. R.; Hinzman, L. D.

    2009-12-01

    The sub-arctic environment can be characterized by being located in the zone of discontinuous permafrost. Although the distribution of permafrost in this region is specific, it dominates the response of many of the hydrologic processes including stream flow, soil moisture dynamics, and water storage processes. In areas underlain by permafrost, ice-rich conditions at the permafrost table inhibit surface water percolation to the deep subsurface soils, resulting in an increased runoff generation generation during precipitation events, decreased baseflow between precipitation events, and relatively wetter soils compared to permafrost-free areas. Over the course of a summer season, the thawing of the active layer (the thin soil layer about the permafrost that seasonally freezes and thaws) increases the potential water holding capacity of the soil, resulting in a decreasing surface water contribution during precipitation events and a steadily increasing baseflow contribution between precipitation events. Simulation of stream flow in this region is challenging due to the rapidly changing thermal (permafrost versus non-permafrost, active layer development) and hydraulic (hydraulic conductivity and soil storage capacity) conditions in both time and space (x, y, and z-dimensions). Many of the factors that have a control on both permafrost distribution and the thawing/freezing of active layer (such as soil material, soil moisture, and ice content) are not easily quantified at scales beyond the point measurement. In this study, these issues are addressed through streamflow analysis - the only hydrologic process that is easily measured at the basin scale. Following the general procedure outlined in Kirchner (2008), a simple rainfall-runoff model was applied to three small head-water basins of varying permafrost coverage. A simple, first-order, non-linear differential equation that describes the storage-discharge relationship were derived from three years of stream flow data

  10. Toward "pseudo-haptic avatars": modifying the visual animation of self-avatar can simulate the perception of weight lifting.

    PubMed

    Jáuregui, David Antonio Gómez; Argelaguet, Ferran; Olivier, Anne-Hélène; Marchal, Maud; Multon, Franck; Lécuyer, Anatole

    2014-04-01

    In this paper we study how the visual animation of a self-avatar can be artificially modified in real-time in order to generate different haptic perceptions. In our experimental setup, participants could watch their self-avatar in a virtual environment in mirror mode while performing a weight lifting task. Users could map their gestures on the self-animated avatar in real-time using a Kinect. We introduce three kinds of modification of the visual animation of the self-avatar according to the effort delivered by the virtual avatar: 1) changes on the spatial mapping between the user’s gestures and the avatar, 2) different motion profiles of the animation, and 3) changes in the posture of the avatar (upper-body inclination). The experimental task consisted of a weight lifting task in which participants had to order four virtual dumbbells according to their virtual weight. The user had to lift each virtual dumbbells by means of a tangible stick, the animation of the avatar was modulated according to the virtual weight of the dumbbell. The results showed that the altering the spatial mapping delivered the best performance. Nevertheless, participants globally appreciated all the different visual effects. Our results pave the way to the exploitation of such novel techniques in various VR applications such as sport training, exercise games, or industrial training scenarios in single or collaborative mode.

  11. Interactions of CO2, temperature and management practices: simulations with a modified version of CERES-Wheat

    NASA Technical Reports Server (NTRS)

    Tubiello, F. N.; Rosenzweig, C.; Volk, T.

    1995-01-01

    A new growth subroutine was developed for CERES-Wheat, a computer model of wheat (Triticum aestivum) growth and development. The new subroutine simulates canopy photosynthetic response to CO2 concentrations and light levels, and includes the effects of temperature on canopy light-use efficiency. Its performance was compared to the original CERES-Wheat V-2 10 in 30 different cases. Biomass and yield predictions of the two models were well correlated (correlation coefficient r > 0.95). As an application, summer growth of spring wheat was simulated at one site. Modeled crop responses to higher mean temperatures, different amounts of minimum and maximum warming, and doubled CO2 concentrations were compared to observations. The importance of irrigation and nitrogen fertilization in modulating the wheat crop climatic responses were also analyzed. Specifically, in agreement with observations, rainfed crops were found to be more sensitive to CO2 increases than irrigated ones. On the other hand, low nitrogen applications depressed the ability of the wheat crop to respond positively to CO2 increases. In general, the positive effects of high CO2 on grain yield were found to be almost completely counterbalanced by the negative effects of high temperatures. Depending on how temperature minima and maxima were increased, yield changes averaged across management practices ranged from -4% to 8%.

  12. Modifying the Soil and Water Assessment Tool to Simulate Cropland Carbon Flux: Model Development and Initial Evaluation

    SciTech Connect

    Zhang, Xuesong; Izaurralde, Roberto C.; Arnold, Jeffrey; Williams, Jimmy R.; Srinivasan, Raghavan

    2013-10-01

    Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO2 emission, one important source of greenhouse gases (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)- residue and simulate land-atmosphere carbon exchange.

  13. Simulating Crop Evapotranspiration Response under Different Planting Scenarios by Modified SWAT Model in an Irrigation District, Northwest China

    PubMed Central

    Liu, Xin; Wang, Sufen; Xue, Han; Singh, Vijay P.

    2015-01-01

    Modelling crop evapotranspiration (ET) response to different planting scenarios in an irrigation district plays a significant role in optimizing crop planting patterns, resolving agricultural water scarcity and facilitating the sustainable use of water resources. In this study, the SWAT model was improved by transforming the evapotranspiration module. Then, the improved model was applied in Qingyuan Irrigation District of northwest China as a case study. Land use, soil, meteorology, irrigation scheduling and crop coefficient were considered as input data, and the irrigation district was divided into subdivisions based on the DEM and local canal systems. On the basis of model calibration and verification, the improved model showed better simulation efficiency than did the original model. Therefore, the improved model was used to simulate the crop evapotranspiration response under different planting scenarios in the irrigation district. Results indicated that crop evapotranspiration decreased by 2.94% and 6.01% under the scenarios of reducing the planting proportion of spring wheat (scenario 1) and summer maize (scenario 2) by keeping the total cultivated area unchanged. However, the total net output values presented an opposite trend under different scenarios. The values decreased by 3.28% under scenario 1, while it increased by 7.79% under scenario 2, compared with the current situation. This study presents a novel method to estimate crop evapotranspiration response under different planting scenarios using the SWAT model, and makes recommendations for strategic agricultural water management planning for the rational utilization of water resources and development of local economy by studying the impact of planting scenario changes on crop evapotranspiration and output values in the irrigation district of northwest China. PMID:26439928

  14. Simulating Crop Evapotranspiration Response under Different Planting Scenarios by Modified SWAT Model in an Irrigation District, Northwest China.

    PubMed

    Liu, Xin; Wang, Sufen; Xue, Han; Singh, Vijay P

    2015-01-01

    Modelling crop evapotranspiration (ET) response to different planting scenarios in an irrigation district plays a significant role in optimizing crop planting patterns, resolving agricultural water scarcity and facilitating the sustainable use of water resources. In this study, the SWAT model was improved by transforming the evapotranspiration module. Then, the improved model was applied in Qingyuan Irrigation District of northwest China as a case study. Land use, soil, meteorology, irrigation scheduling and crop coefficient were considered as input data, and the irrigation district was divided into subdivisions based on the DEM and local canal systems. On the basis of model calibration and verification, the improved model showed better simulation efficiency than did the original model. Therefore, the improved model was used to simulate the crop evapotranspiration response under different planting scenarios in the irrigation district. Results indicated that crop evapotranspiration decreased by 2.94% and 6.01% under the scenarios of reducing the planting proportion of spring wheat (scenario 1) and summer maize (scenario 2) by keeping the total cultivated area unchanged. However, the total net output values presented an opposite trend under different scenarios. The values decreased by 3.28% under scenario 1, while it increased by 7.79% under scenario 2, compared with the current situation. This study presents a novel method to estimate crop evapotranspiration response under different planting scenarios using the SWAT model, and makes recommendations for strategic agricultural water management planning for the rational utilization of water resources and development of local economy by studying the impact of planting scenario changes on crop evapotranspiration and output values in the irrigation district of northwest China. PMID:26439928

  15. Survival of genetically modified and self-cloned strains of commercial baker's yeast in simulated natural environments: environmental risk assessment.

    PubMed

    Ando, Akira; Suzuki, Chise; Shima, Jun

    2005-11-01

    Although genetic engineering techniques for baker's yeast might improve the yeast's fermentation characteristics, the lack of scientific data on the survival of such strains in natural environments as well as the effects on human health prevent their commercial use. Disruption of acid trehalase gene (ATH1) improves freeze tolerance, which is a crucial characteristic in frozen-dough baking. In this study, ATH1 disruptants constructed by genetic modification (GM) and self-cloning (SC) techniques were used as models to study such effects because these strains have higher freeze tolerance and are expected to be used commercially. Behavior of the strains in simulated natural environments, namely, in soil and water, was studied by measuring the change in the number of viable cells and in the concentration of DNA that contains ATH1 loci. Measurements were made using a real-time PCR method during 40 days of cultivation. Results showed that the number of viable cells of GM and SC strains decreased in a time-dependent manner and that the decrease rate was nearly equal to or higher than that for wild-type (WT) yeast. For all three strains (SC, GM, and WT) in the two simulated natural environments (water and soil), the DNA remained longer than did viable cells but the decrease patterns of either the DNA or the viable cells of SC and GM strains had tendencies similar to those of the WT strain. In conclusion, disruption of ATH1 by genetic engineering apparently does not promote the survival of viable cells and DNA in natural environments. PMID:16269743

  16. Kinetic Monte Carlo Simulation of the oscillatory catalytic CO oxidation using a modified Ziff-Gulari-Barshad model

    NASA Astrophysics Data System (ADS)

    Sinha, Indrajit; Mukherjee, Ashim K.

    2014-03-01

    The oxidation of CO on Pt-group metal surfaces has attracted widespread attention since a long time due to its interesting oscillatory kinetics and spatiotemporal behavior. The use of STM in conjunction with other experimental data has confirmed the validity of the surface reconstruction (SR) model under low pressure and the more recent surface oxide (SO) model which is possible under sub-atmospheric pressure conditions [1]. In the SR model the surface is periodically reconstructed below a certain low critical CO-coverage and this reconstruction is lifted above a second, higher critical CO-coverage. Alternatively the SO model proposes periodic switching between a low-reactivity metallic surface and a high-reactivity oxide surface. Here we present an overview of our recent kinetic Monte Carlo (KMC) simulation studies on the oscillatory kinetics of surface catalyzed CO oxidation. Different modifications of the lattice gas Ziff-Gulari-Barshad (ZGB) model have been utilized or proposed for this purpose. First we present the effect of desorption on the ZGB reactive to poisoned irreversible phase transition in the SR model. Next we discuss our recent research on KMC simulation of the SO model. The ZGB framework is utilized to propose a new model incorporating not only the standard Langmuir-Hinshelwood (LH) mechanism, but also introducing the Mars-van Krevelen (MvK) mechanism for the surface oxide phase [5]. Phase diagrams, which are plots between long time averages of various oscillating quantities against the normalized CO pressure, show two or three transitions depending on the CO coverage critical threshold (CT) value beyond which all adsorbed oxygen atoms are converted to surface oxide.

  17. Simulating Crop Evapotranspiration Response under Different Planting Scenarios by Modified SWAT Model in an Irrigation District, Northwest China.

    PubMed

    Liu, Xin; Wang, Sufen; Xue, Han; Singh, Vijay P

    2015-01-01

    Modelling crop evapotranspiration (ET) response to different planting scenarios in an irrigation district plays a significant role in optimizing crop planting patterns, resolving agricultural water scarcity and facilitating the sustainable use of water resources. In this study, the SWAT model was improved by transforming the evapotranspiration module. Then, the improved model was applied in Qingyuan Irrigation District of northwest China as a case study. Land use, soil, meteorology, irrigation scheduling and crop coefficient were considered as input data, and the irrigation district was divided into subdivisions based on the DEM and local canal systems. On the basis of model calibration and verification, the improved model showed better simulation efficiency than did the original model. Therefore, the improved model was used to simulate the crop evapotranspiration response under different planting scenarios in the irrigation district. Results indicated that crop evapotranspiration decreased by 2.94% and 6.01% under the scenarios of reducing the planting proportion of spring wheat (scenario 1) and summer maize (scenario 2) by keeping the total cultivated area unchanged. However, the total net output values presented an opposite trend under different scenarios. The values decreased by 3.28% under scenario 1, while it increased by 7.79% under scenario 2, compared with the current situation. This study presents a novel method to estimate crop evapotranspiration response under different planting scenarios using the SWAT model, and makes recommendations for strategic agricultural water management planning for the rational utilization of water resources and development of local economy by studying the impact of planting scenario changes on crop evapotranspiration and output values in the irrigation district of northwest China.

  18. Materials Performance of Modified 430 Stainless Steel in Simulated SOFC Stack Environments for Integrated Gasification Fuel Cell System Applications

    SciTech Connect

    Ziomek-Moroz, M.E.; Adler, T.A.; Alman, D.E.; Jablonski, P.D.; Clark, J.A.; Penner, L.R.

    2008-01-01

    The corrosion behaviors of a low silicon and aluminum 430 stainless steel with and without ceria surface treatment were investigated in a simulated coal syngas at 800 {degree sign}C and in air. Thermodynamic calculations were made to predict carbon activities for the coal syngas as a function of temperature. At 800 {degree sign}C, carbon activity is ~1.1, which indicates that carbon that forms could diffuse into the steel and induce carbon corrosion, e.g. carburization and metal dusting. The surface morphology was investigated with X-ray diffraction and scanning electron microscopy. In coal gas, the scale formed on bare steel consisted of Mn1.5Cr1.5O4 and Cr2O3 and on ceria treated steel (Fe, Mn)O, FeCr2O4, Cr2O3, and CeCrO3. Both materials underwent carburization, but not metal dusting. The results of oxidation in air using a thermogravimetric apparatus confirmed that the 430 sample was less resistant to oxidation than the 430 treated with ceria.

  19. Hybridisations Of Simulated Annealing And Modified Simplex Algorithms On A Path Of Steepest Ascent With Multi-Response For Optimal Parameter Settings Of ACO

    NASA Astrophysics Data System (ADS)

    Luangpaiboon, P.

    2009-10-01

    Many entrepreneurs face to extreme conditions for instances; costs, quality, sales and services. Moreover, technology has always been intertwined with our demands. Then almost manufacturers or assembling lines adopt it and come out with more complicated process inevitably. At this stage, products and service improvement need to be shifted from competitors with sustainability. So, a simulated process optimisation is an alternative way for solving huge and complex problems. Metaheuristics are sequential processes that perform exploration and exploitation in the solution space aiming to efficiently find near optimal solutions with natural intelligence as a source of inspiration. One of the most well-known metaheuristics is called Ant Colony Optimisation, ACO. This paper is conducted to give an aid in complicatedness of using ACO in terms of its parameters: number of iterations, ants and moves. Proper levels of these parameters are analysed on eight noisy continuous non-linear continuous response surfaces. Considering the solution space in a specified region, some surfaces contain global optimum and multiple local optimums and some are with a curved ridge. ACO parameters are determined through hybridisations of Modified Simplex and Simulated Annealing methods on the path of Steepest Ascent, SAM. SAM was introduced to recommend preferable levels of ACO parameters via statistically significant regression analysis and Taguchi's signal to noise ratio. Other performance achievements include minimax and mean squared error measures. A series of computational experiments using each algorithm were conducted. Experimental results were analysed in terms of mean, design points and best so far solutions. It was found that results obtained from a hybridisation with stochastic procedures of Simulated Annealing method were better than that using Modified Simplex algorithm. However, the average execution time of experimental runs and number of design points using hybridisations were

  20. Analysis of modified MYJ and YSU boundary layer schemes in WRF-Chem with respect to simulated boundary layer heights and pollutant concentrations

    NASA Astrophysics Data System (ADS)

    Forkel, Renate; Foreman, Richard; Emeis, Stefan

    2014-05-01

    To improve the performance of boundary layer schemes currently applied within WRF-Chem (Grell et al., 2005), the Mellor-Yamada-Janjic (MYJ) model (Mellor and Yamada 1982) and the Yonsei University (YSU) PBL scheme (Hong et al. 2006) have been updated using data from a 100 m high offshore measurement tower called FINO1. The turbulence intensity in the Mellor-Yamada-Janjic model has been enhanced as described in Foreman and Emeis (2012). An alternative to the exchange coefficient for stable stratification in the YSU scheme is described in Foreman et al. (2014). These modifications to the two schemes have been applied and are compared with the existing schemes. For example, the updated MYJ scheme results in an improved representation of the turbulent kinetic energy throughout the boundary layer as compared with the measurements at FINO1. The modified MYJ and YSU schemes, which have been originally developed for wind energy applications, have been implemented into version 3.5 of the WRF model. Simulations with WRF-Chem were carried out for Europe and the region of Augsburg in order to evaluate the effect of the modified PBL schemes on simulated PBL heights, gas phase pollutant and aerosol concentrations. Foreman, R.J. and S. Emeis, 2012. A method for increasing the turbulent kinetic energy in the Mellor-Yamada-Janjic boundary layer parametrization. Boundary Layer Meteorology 145:329-349. Foreman, R.J. S. Emeis and B. Canadillas, 2014. Stable boundary layer parametrization without eddy viscosity or turbulent kinetic energy equation approaches. Submitted to Boundary Layer Meteorology 2014. Grell, G. A., Peckham, S. E., Schmitz, R., McKeen, S. A., Frost, G., Skamarock,W. C., and Eder, B., 2005. Fully Coupled Online Chemistry within the WRF Model. Atmospheric Environment 39, 6957-6975. Hong S, Noh Y, Dudhia J 2006. Nonlocal boundary layer vertical diffusion in a medium-range forecast model. Mon Wea Rev 124:2322-2339. Mellor GL, Yamada T 1982. Development of a turbulence

  1. Selective recovery of Ag(I) coordination anion from simulate nickel electrolyte using corn stalk based adsorbent modified by ammonia-thiosemicarbazide.

    PubMed

    Xiong, Ying; Wan, Li; Xuan, Jing; Wang, Yongwei; Xing, Zhiqing; Shan, Weijun; Lou, Zhenning

    2016-01-15

    In nickel electrolyte, Ag(I) was present at trace level concentration (10-20 mg L(-1)) and existed in the form of AgCli(1-i) coordination anion, instead of Ag(+) positive ion usually in several sources. In the present study, TSC-NH3-OCS adsorbent based on natural corn stalk modified by ammonia (NH3)-thiosemicarbazide (TSC) was synthesized and characterized using some instrumental techniques. The TSC-NH3-OCS adsorbent could selectively adsorb Ag(I) as AgCl(i)(1-i) coordination anion from the Ag(I)-Cu(II)-Ni(II) simulate nickel electrolyte, especially in the case of the very high levels of Cu(II) and Ni(II), which significantly outperforms the commercial available resins. The adsorption mechanism was believed to be electrostatic interaction of the protonated bands of AgCl4(3-) with protonated thiol form of the thioamide units by FTIR and XPS analysis. The maximum adsorption capacity in the Ag(I) single and Ag(I)-Cu(II)-Ni(II) ternary system were obtained and calculated as 153.54 and 46.69 mg g(-1), respectively. The reasons that the maximum adsorption capacity of AgCl(i)(1-i) from the single and ternary system varied widely could be explained by adsorption kinetic and thermodynamic results. In addition, three successive sorption/desorption cycle runs from ternary system were performed which indicated that the TSC-NH3-OCS adsorbent has a good performance for recovery Ag(I) from simulate nickel electrolyte.

  2. Selective recovery of Ag(I) coordination anion from simulate nickel electrolyte using corn stalk based adsorbent modified by ammonia-thiosemicarbazide.

    PubMed

    Xiong, Ying; Wan, Li; Xuan, Jing; Wang, Yongwei; Xing, Zhiqing; Shan, Weijun; Lou, Zhenning

    2016-01-15

    In nickel electrolyte, Ag(I) was present at trace level concentration (10-20 mg L(-1)) and existed in the form of AgCli(1-i) coordination anion, instead of Ag(+) positive ion usually in several sources. In the present study, TSC-NH3-OCS adsorbent based on natural corn stalk modified by ammonia (NH3)-thiosemicarbazide (TSC) was synthesized and characterized using some instrumental techniques. The TSC-NH3-OCS adsorbent could selectively adsorb Ag(I) as AgCl(i)(1-i) coordination anion from the Ag(I)-Cu(II)-Ni(II) simulate nickel electrolyte, especially in the case of the very high levels of Cu(II) and Ni(II), which significantly outperforms the commercial available resins. The adsorption mechanism was believed to be electrostatic interaction of the protonated bands of AgCl4(3-) with protonated thiol form of the thioamide units by FTIR and XPS analysis. The maximum adsorption capacity in the Ag(I) single and Ag(I)-Cu(II)-Ni(II) ternary system were obtained and calculated as 153.54 and 46.69 mg g(-1), respectively. The reasons that the maximum adsorption capacity of AgCl(i)(1-i) from the single and ternary system varied widely could be explained by adsorption kinetic and thermodynamic results. In addition, three successive sorption/desorption cycle runs from ternary system were performed which indicated that the TSC-NH3-OCS adsorbent has a good performance for recovery Ag(I) from simulate nickel electrolyte. PMID:26368801

  3. Modified embedded-atom method interatomic potential for the Fe-Cu alloy system and cascade simulations on pure Fe and Fe-Cu alloys

    NASA Astrophysics Data System (ADS)

    Lee, Byeong-Joo; Wirth, Brian D.; Shim, Jae-Hyeok; Kwon, Junhyun; Kwon, Sang Chul; Hong, Jun-Hwa

    2005-05-01

    A modified embedded-atom method (MEAM) interatomic potential for the Fe-Cu binary system has been developed using previously developed MEAM potentials of Fe and Cu. The Fe-Cu potential was determined by fitting to data on the mixing enthalpy and the composition dependencies of the lattice parameters in terminal solid solutions. The potential gives a value of 0.65eV for the dilute heat of solution and reproduces the increase of lattice parameter of Fe with addition of Cu in good agreement with experiments. The potential was used to investigate the primary irradiation defect formation in pure Fe and Fe-0.5at.%Cu alloy by a molecular dynamics cascade simulation study with a PKA energy of 2keV at 573K . A tendency for self-interstitial atom-Cu binding, the formation of mixed (Fe-Cu) dumbbells and even Cu-Cu dumbbells was observed. Given a positive binding energy between Cu atoms and self-interstitials, Cu transport by an interstitial diffusion mechanism could be proposed to contribute to the formation of Cu-rich precipitates and irradiation-induced embrittlement in nuclear structural steels.

  4. Decomposition of two-component ultrasound pulses in cancellous bone using modified least squares prony method--phantom experiment and simulation.

    PubMed

    Wear, Keith A

    2010-02-01

    Porous media such as cancellous bone often support the simultaneous propagation of two compressional waves. When small bone samples are interrogated in through-transmission with broadband sources, these two waves often overlap in time. The modified least-squares Prony's (MLSP) method was tested for decomposing a 500 kHz-center-frequency signal containing two overlapping components: one passing through a polycarbonate plate (to produce the "fast" wave) and another passing through a cancellous-bone-mimicking phantom (to produce the "slow" wave). The MLSP method yielded estimates of attenuation slopes accurate to within 7% (polycarbonate plate) and 2% (cancellous bone phantom). The MLSP method yielded estimates of phase velocities accurate to within 1.5% (both media). The MLSP method was also tested on simulated data generated using attenuation slopes and phase velocities corresponding to bovine cancellous bone. Throughout broad ranges of signal-to-noise ratio (SNR), the MLSP method yielded estimates of attenuation slope that were accurate to within 1.0% and estimates of phase velocity that were accurate to within 4.3% (fast wave) and 1.3% (slow wave).

  5. Modified cyanobacteria

    DOEpatents

    Vermaas, Willem F J.

    2014-06-17

    Disclosed is a modified photoautotrophic bacterium comprising genes of interest that are modified in terms of their expression and/or coding region sequence, wherein modification of the genes of interest increases production of a desired product in the bacterium relative to the amount of the desired product production in a photoautotrophic bacterium that is not modified with respect to the genes of interest.

  6. Modified blank ammunition injuries.

    PubMed

    Ogunc, Gokhan I; Ozer, M Tahir; Coskun, Kagan; Uzar, Ali Ihsan

    2009-12-15

    Blank firing weapons are designed only for discharging blank ammunition cartridges. Because they are cost-effective, are easily accessible and can be modified to live firearms plus their unclear legal situation in Turkish Law makes them very popular in Turkey. 2004 through 2008, a total of 1115 modified blank weapons were seized in Turkey. Blank firing weapons are easily modified by owners, making them suitable for discharging live firearm ammunition or modified blank ammunitions. Two common methods are used for modification of blank weapons. After the modification, these weapons can discharge the live ammunition. However, due to compositional durability problems with these types of weapons; the main trend is to use the modified blank ammunitions rather than live firearm ammunition fired from modified blank firing weapons. In this study, two types of modified blank weapons and two types of modified blank cartridges were tested on three different target models. Each of the models' shooting side was coated with 1.3+/-2 mm thickness chrome tanned cowhide as a skin simulant. The first model was only coated with skin simulant. The second model was coated with skin simulant and 100% cotton police shirt. The third model was coated with skin simulant and jean denim. After the literature evaluation four high risky anatomic locations (the neck area; the eyes; the thorax area and inguinal area) were pointed out for the steel and lead projectiles are discharged from the modified blank weapons especially in close range (0-50 cm). The target models were designed for these anatomic locations. For the target models six Transparent Ballistic Candle blocks (TCB) were prepared and divided into two test groups. The first group tests were performed with lead projectiles and second group with steel projectile. The shortest penetration depth (lead projectile: 4.358 cm; steel projectile 8.032 cm) was recorded in the skin simulant and jean denim coated block for both groups. In both groups

  7. Modified blank ammunition injuries.

    PubMed

    Ogunc, Gokhan I; Ozer, M Tahir; Coskun, Kagan; Uzar, Ali Ihsan

    2009-12-15

    Blank firing weapons are designed only for discharging blank ammunition cartridges. Because they are cost-effective, are easily accessible and can be modified to live firearms plus their unclear legal situation in Turkish Law makes them very popular in Turkey. 2004 through 2008, a total of 1115 modified blank weapons were seized in Turkey. Blank firing weapons are easily modified by owners, making them suitable for discharging live firearm ammunition or modified blank ammunitions. Two common methods are used for modification of blank weapons. After the modification, these weapons can discharge the live ammunition. However, due to compositional durability problems with these types of weapons; the main trend is to use the modified blank ammunitions rather than live firearm ammunition fired from modified blank firing weapons. In this study, two types of modified blank weapons and two types of modified blank cartridges were tested on three different target models. Each of the models' shooting side was coated with 1.3+/-2 mm thickness chrome tanned cowhide as a skin simulant. The first model was only coated with skin simulant. The second model was coated with skin simulant and 100% cotton police shirt. The third model was coated with skin simulant and jean denim. After the literature evaluation four high risky anatomic locations (the neck area; the eyes; the thorax area and inguinal area) were pointed out for the steel and lead projectiles are discharged from the modified blank weapons especially in close range (0-50 cm). The target models were designed for these anatomic locations. For the target models six Transparent Ballistic Candle blocks (TCB) were prepared and divided into two test groups. The first group tests were performed with lead projectiles and second group with steel projectile. The shortest penetration depth (lead projectile: 4.358 cm; steel projectile 8.032 cm) was recorded in the skin simulant and jean denim coated block for both groups. In both groups

  8. Experimental evaluation of the effect of a modified port-location mode on the performance of a three-zone simulated moving-bed process for the separation of valine and isoleucine.

    PubMed

    Park, Chanhun; Nam, Hee-Geun; Kim, Pung-Ho; Mun, Sungyong

    2014-06-01

    The removal of isoleucine from valine has been a key issue in the stage of valine crystallization, which is the final step in the valine production process in industry. To address this issue, a three-zone simulated moving-bed (SMB) process for the separation of valine and isoleucine has been developed previously. However, the previous process, which was based on a classical port-location mode, had some limitations in throughput and valine product concentration. In this study, a three-zone SMB process based on a modified port-location mode was applied to the separation of valine and isoleucine for the purpose of making a marked improvement in throughput and valine product concentration. Computer simulations and a lab-scale process experiment showed that the modified three-zone SMB for valine separation led to >65% higher throughput and >160% higher valine concentration compared to the previous three-zone SMB for the same separation.

  9. Modified Embedded Atom Method

    2012-08-01

    Interatomic force and energy calculation subroutine to be used with the molecular dynamics simulation code LAMMPS (Ref a.). The code evaluated the total energy and atomic forces (energy gradient) according to a cubic spline-based variant (Ref b.) of the Modified Embedded Atom Method (MEAM) with a additional Stillinger-Weber (SW) contribution.

  10. Quality and physiological responses of two late-season sweet cherry cultivars 'Lapins' and 'Skeena' to modified atmosphere packaging (MAP) during simulated long distance ocean shipping

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flavor loss, skin darkening, pitting, splitting, pedicel browning, and decay are the major quality deteriorations in sweet cherries during storage/shipping. In this research, three modified atmosphere packaging (MAP) liners with varied gas permeability were evaluated for the effect on quality deteri...

  11. Improved recovery from Gulf of Mexico reservoirs. Volume II (of 4): Task 5, modify publicly available simulators. Final report, February 14, 1995--October 13, 1996

    SciTech Connect

    Kimbrell, W.C.; Bassiouni, Z.A.; Bourgoyne, A.T.

    1997-01-13

    The objective for this portion of the research involved the continuation of the modifications of the public domain simulators BOAST and MASTER. The modifications continued during this project are generic relative to both BOAST and MASTER. BOAST was the primary concern during the research however, because MASTER as well.

  12. Quantum mechanical NMR simulation algorithm for protein-size spin systems

    NASA Astrophysics Data System (ADS)

    Edwards, Luke J.; Savostyanov, D. V.; Welderufael, Z. T.; Lee, Donghan; Kuprov, Ilya

    2014-06-01

    Nuclear magnetic resonance spectroscopy is one of the few remaining areas of physical chemistry for which polynomially scaling quantum mechanical simulation methods have not so far been available. In this communication we adapt the restricted state space approximation to protein NMR spectroscopy and illustrate its performance by simulating common 2D and 3D liquid state NMR experiments (including accurate description of relaxation processes using Bloch-Redfield-Wangsness theory) on isotopically enriched human ubiquitin - a protein containing over a thousand nuclear spins forming an irregular polycyclic three-dimensional coupling lattice. The algorithm uses careful tailoring of the density operator space to only include nuclear spin states that are populated to a significant extent. The reduced state space is generated by analysing spin connectivity and decoherence properties: rapidly relaxing states as well as correlations between topologically remote spins are dropped from the basis set.

  13. Simulation of nitrate-concentration variation and estimation of nitrogen-form transformation in groundwater by modified rain-runoff model

    NASA Astrophysics Data System (ADS)

    Hong, N.; Hama, T.; Suenaga, Y.; Huang, X.; Wei, Q.; Kawagoshi, Y.

    2015-12-01

    Groundwater is an important drinking-water source throughout the world. Nitrate is considered as one of the most widespread contaminant in groundwater and some studies have presented that intake of excess amount of nitrate could be associated with several types of disease. Modeling of nitrate-concentration in groundwater and estimation of nitrogen-form transformation by meteorological effects is necessary for countermeasure to nitrate contamination in groundwater. In this research, groundwater-quality tank model (GQTM) coupled with Fuzzy Optimize Method (FOM) and Shuffled Complex Evolution-University of Arizona (SCE-UA) is proposed to simulate NO3- and Cl- concentrations simultaneously. For the simulation, daily precipitation data and weekly data of NO3- and Cl- concentrations at two observation wells in Kumamoto City for three years (2012-2015) were used. The GQTM coupled with FOM and SCE-UA algorithm provided accurate simulation results in the variations of NO3- and Cl- concentrations. Difference in the concentration-variation ratio between NO3- and Cl- suggested that NO3- concentration variation was mainly due to dilution and concentration processes rather than nitrogen transformation by nitrification-denitrification reaction in the both observation wells. This calculation provides a simple and reliable method in nitrification and denitrification process estimation. The GQTM coupled with FOM and SCE-UA must be useful for managing of groundwater supplies in effective and sustainable manner by providing scientific evidence for the risk of groundwater quality.

  14. Influence of the solvent on the self-assembly of a modified amyloid beta peptide fragment. II. NMR and computer simulation investigation.

    PubMed

    Hamley, I W; Nutt, D R; Brown, G D; Miravet, J F; Escuder, B; Rodríguez-Llansola, F

    2010-01-21

    The conformation of a model peptide AAKLVFF based on a fragment of the amyloid beta peptide Abeta16-20, KLVFF, is investigated in methanol and water via solution NMR experiments and molecular dynamics computer simulations. In previous work, we have shown that AAKLVFF forms peptide nanotubes in methanol and twisted fibrils in water. Chemical shift measurements were used to investigate the solubility of the peptide as a function of concentration in methanol and water. This enabled the determination of critical aggregation concentrations. The solubility was lower in water. In dilute solution, diffusion coefficients revealed the presence of intermediate aggregates in concentrated solution, coexisting with NMR-silent larger aggregates, presumed to be beta-sheets. In water, diffusion coefficients did not change appreciably with concentration, indicating the presence mainly of monomers, coexisting with larger aggregates in more concentrated solution. Concentration-dependent chemical shift measurements indicated a folded conformation for the monomers/intermediate aggregates in dilute methanol, with unfolding at higher concentration. In water, an antiparallel arrangement of strands was indicated by certain ROESY peak correlations. The temperature-dependent solubility of AAKLVFF in methanol was well described by a van't Hoff analysis, providing a solubilization enthalpy and entropy. This pointed to the importance of solvophobic interactions in the self-assembly process. Molecular dynamics simulations constrained by NOE values from NMR suggested disordered reverse turn structures for the monomer, with an antiparallel twisted conformation for dimers. To model the beta-sheet structures formed at higher concentration, possible model arrangements of strands into beta-sheets with parallel and antiparallel configurations and different stacking sequences were used as the basis for MD simulations; two particular arrangements of antiparallel beta-sheets were found to be stable, one

  15. SUMMARY OF 2009 RHEOLOGY MODIFIER PROGRAM

    SciTech Connect

    Hansen, E.

    2009-12-08

    The overall objective of the EM-31 Rheological Modifiers and Wetting Agents program is to utilize commercially available rheology modifiers to increase the solids fraction of radioactive sludge based waste streams, resulting in an increase in throughput and decreasing the overall processing time. The program first investigates the impact of rheology modifiers on slurry simulants and then utilizes the most effective rheology modifiers on radioactive slurries. The work presented in this document covers the initial investigation of rheology modifier testing with simulants. This task is supported by both the Savannah River National Laboratory (SRNL) and Pacific Northwest National Laboratory (PNNL). The SRNL EM-31 task, for this year, was to investigate the use of rheology modifiers on simulant Defense Waste Processing Facility (DWPF) melter feeds. The task is to determine, based on the impact of the rheology modifier, if there are rheology modifiers that could reduce the water content of the slurry going to the DWPF melter, hence increasing the melt rate by decreasing the water loading. The rheology modifier in essence would allow a higher solids content slurry to have the same type of rheology or pumpability of a lower solids slurry. The modifiers selected in this report were determined based on previous modifiers used in high level waste melter feed simulants, on-going testing performed by counterparts at PNNL, and experiences gain through use of modifiers in other Department of Energy (DOE) processes such as grout processing. There were 12 rheology modifiers selected for testing, covering both organic and inorganic types and they were tested at four different concentrations for a given melter feed. Five different DWPF melter feeds were available and there was adequate material in one of the melter feeds to increase the solids concentration, resulting in a total of six simulants for testing. The mass of melter feed available in each simulant was not adequate for

  16. Coarse grid shallow water simulations of rainfall-runoff in small catchments with modified friction law to account for unresolved microtopography

    NASA Astrophysics Data System (ADS)

    Özgen, Ilhan; Serrano-Taslim, Miguel; Zhao, Jiaheng; Liang, Dongfang; Hinkelmann, Reinhard

    2016-04-01

    In recent years, the fully dynamic shallow water equations have been successfully used to simulate rainfall-runoff in natural catchments. Hereby, the hydrodynamics of the surface runoff is greatly influenced by local topographical features. Thus, it is desirable to use high-resolution models which resolve the topography of the study area sufficiently. However, high-resolution simulations across catchment scales are often unfeasible due to finite computer resources. In this contribution, the shallow water equations are solved on a coarse resolution, leaving significant topographical features unresolved. The coarsened grid size leads to a smaller cell number and therefore reduces computational cost. The influence of the topography is accounted for with an artificial friction source term which is dependent on the inundation ratio, i.e. the ratio of water depth to roughness height, the slope and two additional parameters, namely a dimensionless friction coefficient and a geometric conveyance parameter. Subgrid scale information is used to determine these parameters. The friction approach is applied in two different ways: (1) a global average roughness height for the entire catchment is calculated and used as input, (2) the roughness height is calculated individually in each cell which introduces additional heterogeneity to the model. In two test cases, the individual roughness height-based approach is compared to results of the global roughness height-based approach and to igh-resolution model results. The comparison shows slight improvement in the results if the roughness height is assigned individually, however overall the improvement is negligible. Both models enable to run the simulations about three orders of magnitude faster than the high-resolution model.

  17. Enhancement of osteogenic differentiation and proliferation in human mesenchymal stem cells by a modified low intensity ultrasound stimulation under simulated microgravity.

    PubMed

    Uddin, Sardar M Z; Qin, Yi-Xian

    2013-01-01

    Adult stem cells can differentiate into multiple lineages depending on their exposure to differing biochemical and biomechanical inductive factors. Lack of mechanical signals due to disuse can inhibit osteogenesis and induce adipogenesis of mesenchymal stem cells (MSCs). Long-term bed rest due to both brain/spinal cord injury and space travel can lead to disuse osteoporosis that is in part caused by a reduced number of osteoblasts. Thus, it is essential to provide proper mechanical stimulation for cellular viability and osteogenesis, particularly under disuse conditions. The objective of this study was to examine the effects of low intensity pulsed ultrasound (LIPUS) on the osteogenic differentiation of adipose-derived human stem cells (Ad-hMSC) in simulated microgravity conditions. Cells were cultured in a 1D clinostat to simulate microgravity (SMG) and treated with LIPUS at 30mW/cm(2) for 20 min/day. It was hypothesized that the application of LIPUS to SMG cultures would restore osteogenesis in Ad-hMSCs. The results showed significant increases in ALP, OSX, RANKL, RUNX2, and decreases in OPG in LIPUS treated SMG cultures of Ad-MSC compared to non-treated cultures. LIPUS also restored OSX, RUNX2 and RANKL expression in osteoblast cells. SMG significantly reduced ALP positive cells by 70% (p<0.01) and ALP activity by 22% (p<0.01), while LIPUS treatment restored ALP positive cell number and activity to equivalence with normal gravity controls. Extracellular matrix collagen and mineralization was assessed by Sirius red and Alizarin red staining, respectively. SMG cultures showed little or no collagen or mineralization, but LIPUS treatment restored collagen content to 50% (p<0.001) and mineralization by 45% (p<0.001) in LIPUS treated-SMG cultures relative to SMG-only cultures. The data suggest that LIPUS treatment can restore normal osteogenic differentiation of MSCs from disuse by daily short duration stimulation.

  18. Enhancement of osteogenic differentiation and proliferation in human mesenchymal stem cells by a modified low intensity ultrasound stimulation under simulated microgravity.

    PubMed

    Uddin, Sardar M Z; Qin, Yi-Xian

    2013-01-01

    Adult stem cells can differentiate into multiple lineages depending on their exposure to differing biochemical and biomechanical inductive factors. Lack of mechanical signals due to disuse can inhibit osteogenesis and induce adipogenesis of mesenchymal stem cells (MSCs). Long-term bed rest due to both brain/spinal cord injury and space travel can lead to disuse osteoporosis that is in part caused by a reduced number of osteoblasts. Thus, it is essential to provide proper mechanical stimulation for cellular viability and osteogenesis, particularly under disuse conditions. The objective of this study was to examine the effects of low intensity pulsed ultrasound (LIPUS) on the osteogenic differentiation of adipose-derived human stem cells (Ad-hMSC) in simulated microgravity conditions. Cells were cultured in a 1D clinostat to simulate microgravity (SMG) and treated with LIPUS at 30mW/cm(2) for 20 min/day. It was hypothesized that the application of LIPUS to SMG cultures would restore osteogenesis in Ad-hMSCs. The results showed significant increases in ALP, OSX, RANKL, RUNX2, and decreases in OPG in LIPUS treated SMG cultures of Ad-MSC compared to non-treated cultures. LIPUS also restored OSX, RUNX2 and RANKL expression in osteoblast cells. SMG significantly reduced ALP positive cells by 70% (p<0.01) and ALP activity by 22% (p<0.01), while LIPUS treatment restored ALP positive cell number and activity to equivalence with normal gravity controls. Extracellular matrix collagen and mineralization was assessed by Sirius red and Alizarin red staining, respectively. SMG cultures showed little or no collagen or mineralization, but LIPUS treatment restored collagen content to 50% (p<0.001) and mineralization by 45% (p<0.001) in LIPUS treated-SMG cultures relative to SMG-only cultures. The data suggest that LIPUS treatment can restore normal osteogenic differentiation of MSCs from disuse by daily short duration stimulation. PMID:24069248

  19. Biogenic carbon and nitrogen export in a deep-convection region: simulations in the Labrador Sea

    NASA Astrophysics Data System (ADS)

    Tian, Ru Cheng; Deibel, Don; Rivkin, Richard B.; Vézina, Alain F.

    2004-03-01

    The Labrador Sea is a major sink of anthropogenic CO 2 due to deep-water formation in winter. To investigate the relative importance of different forms of export flux, we used a physical-biogeochemical model to simulate the vertical fluxes of particulate and dissolved biogenic carbon as a function of winter convection, food web dynamics and zooplankton vertical migration. The C:N ratio of these export fluxes was simulated based on trophic dynamics and bacterial activity. The model was run using winter convection and seasonal mixed layer evolution extracted from multi-year physical data collected in the central Labrador Sea. Comparisons between model output and data from the Labrador Sea and other systems indicate that the model provides a realistic picture of carbon and nitrogen pools and fluxes. Our results suggest that on an annual basis, dissolved organic carbon (DOC) export by deep, vertical convection is greater than that of the sinking flux of POC. Furthermore, the C:N ratio of exported dissolved organic matter (DOM) is higher than that of the particle sinking flux, resulting in 23% more carbon exported than would be estimated if predictions were made from the Redfield ratio (e.g., 11.4 vs. 7.0 for DOM and particulate organic matter, respectively, at the bottom of the euphotic zone and 17.2 vs. 9.3 at 1000 m depth). The active export of carbon by the respiration and mortality of migrating zooplankton amounts to 19% of sinking flux annually, but only 6% of total carbon export because of the high rates of DOC export in deep-water formation regions. Our model simulations indicate that non-Redfield ratio DOC export characterizes the function of the biological pump in deep-water formation regions.

  20. Oxidation of elemental mercury by modified spent TiO2-based SCR-DeNOx catalysts in simulated coal-fired flue gas.

    PubMed

    Zhao, Lingkui; Li, Caiting; Zhang, Xunan; Zeng, Guangming; Zhang, Jie; Xie, Yin'e

    2016-01-01

    In order to reduce the costs, the recycle of spent TiO2-based SCR-DeNOx catalysts were employed as a potential catalytic support material for elemental mercury (Hg(0)) oxidation in simulated coal-fired flue gas. The catalytic mechanism for simultaneous removal of Hg(0) and NO was also investigated. The catalysts were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) method. Results indicated that spent TiO2-based SCR-DeNOx catalyst supported Ce-Mn mixed oxides catalyst (CeMn/SCR1) was highly active for Hg(0) oxidation at low temperatures. The Ce1.00Mn/SCR1 performed the best catalytic activities, and approximately 92.80% mercury oxidation efficiency was obtained at 150 °C. The inhibition effect of NH3 on Hg(0) oxidation was confirmed in that NH3 consumed the surface oxygen. Moreover, H2O inhibited Hg(0) oxidation while SO2 had a promotional effect with the aid of O2. The XPS results illustrated that the surface oxygen was responsible for Hg(0) oxidation and NO conversion. Besides, the Hg(0) oxidation and NO conversion were thought to be aided by synergistic effect between the manganese and cerium oxides. PMID:26370819

  1. Oxidation of elemental mercury by modified spent TiO2-based SCR-DeNOx catalysts in simulated coal-fired flue gas.

    PubMed

    Zhao, Lingkui; Li, Caiting; Zhang, Xunan; Zeng, Guangming; Zhang, Jie; Xie, Yin'e

    2016-01-01

    In order to reduce the costs, the recycle of spent TiO2-based SCR-DeNOx catalysts were employed as a potential catalytic support material for elemental mercury (Hg(0)) oxidation in simulated coal-fired flue gas. The catalytic mechanism for simultaneous removal of Hg(0) and NO was also investigated. The catalysts were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) method. Results indicated that spent TiO2-based SCR-DeNOx catalyst supported Ce-Mn mixed oxides catalyst (CeMn/SCR1) was highly active for Hg(0) oxidation at low temperatures. The Ce1.00Mn/SCR1 performed the best catalytic activities, and approximately 92.80% mercury oxidation efficiency was obtained at 150 °C. The inhibition effect of NH3 on Hg(0) oxidation was confirmed in that NH3 consumed the surface oxygen. Moreover, H2O inhibited Hg(0) oxidation while SO2 had a promotional effect with the aid of O2. The XPS results illustrated that the surface oxygen was responsible for Hg(0) oxidation and NO conversion. Besides, the Hg(0) oxidation and NO conversion were thought to be aided by synergistic effect between the manganese and cerium oxides.

  2. A modified chaotic cryptographic method

    NASA Astrophysics Data System (ADS)

    Wong, Wai-kit; Lee, Lap-piu; Wong, Kwok-wo

    2001-08-01

    We propose a modified version of the chaotic cryptographic method based on iterating a logistic map. Simulation results show that the distribution of the ciphertext is flatter and the encryption time is shorter. Moreover, the trade-off between the spread of the distribution of ciphertext and the encryption time can be controlled by a single parameter.

  3. Modified 24 kb/s ADPCM System

    NASA Astrophysics Data System (ADS)

    Al-Rawi, M. F.; Al-Rawi, M.

    2013-09-01

    This paper presents new modified 24 kb/s Adaptive Differential Pulse Code Modulation (ADPCM) system. The modified ADPCM uses 4-bit quantizer with sampling rate of 6,000 sample/s, while, the standard ADPCM uses 3-bit quantizer with sampling rate of 8,000 sample/s. The purpose of this modification is to reduce the nonlinear distortion introduced by ADPCM when QAM signal is sent over it. The performances of standard and modified ADPCM are studied using QAM signal at data rate of 9.6 kb/s. The simulation results show that the performance of modified ADPCM is better than standard ADPCM.

  4. Review Of Rheology Modifiers For Hanford Waste

    SciTech Connect

    Pareizs, J. M.

    2013-09-30

    As part of Savannah River National Laboratory (SRNL)'s strategic development scope for the Department of Energy - Office of River Protection (DOE-ORP) Hanford Tank Waste Treatment and Immobilization Plant (WTP) waste feed acceptance and product qualification scope, the SRNL has been requested to recommend candidate rheology modifiers to be evaluated to adjust slurry properties in the Hanford Tank Farm. SRNL has performed extensive testing of rheology modifiers for use with Defense Waste Processing Facility (DWPF) simulated melter feed - a high undissolved solids (UDS) mixture of simulated Savannah River Site (SRS) Tank Farm sludge, nitric and formic acids, and glass frit. A much smaller set of evaluations with Hanford simulated waste have also been completed. This report summarizes past work and recommends modifiers for further evaluation with Hanford simulated wastes followed by verification with actual waste samples. Based on the review of available data, a few compounds/systems appear to hold the most promise. For all types of evaluated simulated wastes (caustic Handford tank waste and DWPF processing samples with pH ranging from slightly acidic to slightly caustic), polyacrylic acid had positive impacts on rheology. Citric acid also showed improvement in yield stress on a wide variety of samples. It is recommended that both polyacrylic acid and citric acid be further evaluated as rheology modifiers for Hanford waste. These materials are weak organic acids with the following potential issues: The acidic nature of the modifiers may impact waste pH, if added in very large doses. If pH is significantly reduced by the modifier addition, dissolution of UDS and increased corrosion of tanks, piping, pumps, and other process equipment could occur. Smaller shifts in pH could reduce aluminum solubility, which would be expected to increase the yield stress of the sludge. Therefore, it is expected that use of an acidic modifier would be limited to concentrations that do not

  5. Colorimetric response of dithizone product and hexadecyl trimethyl ammonium bromide modified gold nanoparticle dispersion to 10 types of heavy metal ions: understanding the involved molecules from experiment to simulation.

    PubMed

    Leng, Yumin; Li, Yonglong; Gong, An; Shen, Zheyu; Chen, Liang; Wu, Aiguo

    2013-06-25

    A new kind of analytical reagent, hexadecyl trimethyl ammonium bromide (CTAB), and dithizone product-modified gold nanoparticle dispersion, is developed for colorimetric response to 10 types of heavy metal ions (M(n+)), including Cr(VI), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change of the modified gold nanoparticle dispersion is instantaneous and distinct for Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change results from the multiple reasons, such as electronic transitions, cation-π interactions, formation of coordination bonds, and M(n+)-induced aggregation of gold nanoparticles (AuNPs). The different combining capacity of heavy metal ions to modifiers results in the different broadening and red-shifting of the plasmon peak of modified AuNPs. In addition, Cr(VI), Cu(2+), Co(2+), Ni(2+), and Mn(2+) cause the new UV-vis absorption peaks in the region of 360-460 nm. The interactions between the modifiers and AuNPs, and between the modifiers and M(n+), are investigated by using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results confirm that AuNPs are modified by CTAB and dithizone products through electrostatic interactions and Au-S bonds, respectively, and the M(n+)-N bonds form between M(n+) and dithizone products. Furthermore, the experimental and density functional theory calculated IR spectra prove that dithizone reacts with NaOH to produce C6H5O(-) and [SCH2N4](2-). The validation of this method is carried out by analysis of heavy metal ions in tap water. PMID:23724944

  6. Colorimetric response of dithizone product and hexadecyl trimethyl ammonium bromide modified gold nanoparticle dispersion to 10 types of heavy metal ions: understanding the involved molecules from experiment to simulation.

    PubMed

    Leng, Yumin; Li, Yonglong; Gong, An; Shen, Zheyu; Chen, Liang; Wu, Aiguo

    2013-06-25

    A new kind of analytical reagent, hexadecyl trimethyl ammonium bromide (CTAB), and dithizone product-modified gold nanoparticle dispersion, is developed for colorimetric response to 10 types of heavy metal ions (M(n+)), including Cr(VI), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change of the modified gold nanoparticle dispersion is instantaneous and distinct for Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), and Pb(2+). The color change results from the multiple reasons, such as electronic transitions, cation-π interactions, formation of coordination bonds, and M(n+)-induced aggregation of gold nanoparticles (AuNPs). The different combining capacity of heavy metal ions to modifiers results in the different broadening and red-shifting of the plasmon peak of modified AuNPs. In addition, Cr(VI), Cu(2+), Co(2+), Ni(2+), and Mn(2+) cause the new UV-vis absorption peaks in the region of 360-460 nm. The interactions between the modifiers and AuNPs, and between the modifiers and M(n+), are investigated by using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results confirm that AuNPs are modified by CTAB and dithizone products through electrostatic interactions and Au-S bonds, respectively, and the M(n+)-N bonds form between M(n+) and dithizone products. Furthermore, the experimental and density functional theory calculated IR spectra prove that dithizone reacts with NaOH to produce C6H5O(-) and [SCH2N4](2-). The validation of this method is carried out by analysis of heavy metal ions in tap water.

  7. Modifying Classroom Behavior

    ERIC Educational Resources Information Center

    Heifetz, Louis J.; Farber, Barry A.

    1976-01-01

    An introductory framework for analyzing and modifying classroom behavior...is followed by presentation of illustrative case materials, discussion of philosophical and ethical issues, analysis of pitfalls to be avoided, and consideration of limitations inherent in behavioral approaches. (Author)

  8. Biological response modifiers

    SciTech Connect

    Weller, R.E.

    1988-10-01

    Much of what used to be called immunotherapy is now included in the term biological response modifiers. Biological response modifiers (BRMs) are those agents or approaches that modify the relationship between the tumor and host by modifying the host's biological response to tumor cells with resultant therapeutic effects. Most of the early work with BRMs centered around observations of spontaneous tumor regression and the association of tumor regression with concurrent bacterial infections. The BRM can modify the host response by increasing the host's antitumor responses through augmentation and/or restoration of effector mechanisms or mediators of the host's defense or decrease the deleterious component by the host's reaction, increasing the host's defenses by the administration of natural biologics (or the synthetic derivatives thereof) as effectors or mediators of an antitumor response, augmenting the host's response to modified tumor cells or vaccines, which might stimulate a greater response by the host or increase tumor-cell sensitivity to an existing response, decreasing the transformation and/or increase differentiation (maturation) of tumor cells, or increasing the ability of the host to tolerate damage by cytotoxic modalities of cancer treatment.

  9. Biological response modifiers

    SciTech Connect

    Weller, R.E.

    1991-10-01

    Much of what used to be called immunotherapy is now included in the term biological response modifiers. Biological response modifiers (BRMs) are defined as those agents or approaches that modify the relationship between the tumor and host by modifying the host's biological response to tumor cells with resultant therapeutic effects.'' Most of the early work with BRMs centered around observations of spontaneous tumor regression and the association of tumor regression with concurrent bacterial infections. The BRM can modify the host response in the following ways: Increase the host's antitumor responses through augmentation and/or restoration of effector mechanisms or mediators of the host's defense or decrease the deleterious component by the host's reaction; Increase the host's defenses by the administration of natural biologics (or the synthetic derivatives thereof) as effectors or mediators of an antitumor response; Augment the host's response to modified tumor cells or vaccines, which might stimulate a greater response by the host or increase tumor-cell sensitivity to an existing response; Decrease the transformation and/or increase differentiation (maturation) of tumor cells; or Increase the ability of the host to tolerate damage by cytotoxic modalities of cancer treatment.

  10. Spring bloom community change modifies carbon pathways and C : N : P : Chl a stoichiometry of coastal material fluxes

    NASA Astrophysics Data System (ADS)

    Spilling, K.; Kremp, A.; Klais, R.; Olli, K.; Tamminen, T.

    2014-08-01

    Diatoms and dinoflagellates are major bloom-forming phytoplankton groups competing for resources in the oceans and coastal seas. Recent evidence suggests that their competition is significantly affected by climatic factors under ongoing change, modifying especially the conditions for cold-water, spring bloom communities in temperate and arctic regions. We investigated the effects of phytoplankton community composition on spring bloom carbon flows and nutrient stoichiometry in multi-year mesocosm experiments. Comparison of differing communities showed that community structure significantly affected C accumulation parameters, with highest particulate organic carbon (POC) build-up and dissolved organic carbon (DOC) release in diatom-dominated communities. In terms of inorganic nutrient drawdown and bloom accumulation phase, the dominating groups behaved as functional surrogates. Dominance patterns, however, significantly affected C : N : P : Chl a ratios over the whole bloom event: when diatoms were dominant, these ratios increased compared to dinoflagellate dominance or mixed communities. Diatom-dominated communities sequestered carbon up to 3.6-fold higher than the expectation based on the Redfield ratio, and 2-fold higher compared to dinoflagellate dominance. To our knowledge, this is the first experimental report of consequences of climatically driven shifts in phytoplankton dominance patterns for carbon sequestration and related biogeochemical cycles in coastal seas. Our results also highlight the need for remote sensing technologies with taxonomical resolution, as the C : Chl a ratio was strongly dependent on community composition and bloom stage. Climate-driven changes in phytoplankton dominance patterns will have far-reaching consequences for major biogeochemical cycles and need to be considered in climate change scenarios for marine systems.

  11. Spring bloom community change modifies carbon pathways and C : N : P : Chl a stoichiometry of coastal material fluxes

    NASA Astrophysics Data System (ADS)

    Spilling, K.; Kremp, A.; Klais, R.; Olli, K.; Tamminen, T.

    2014-12-01

    Diatoms and dinoflagellates are major bloom-forming phytoplankton groups competing for resources in the oceans and coastal seas. Recent evidence suggests that their competition is significantly affected by climatic factors under ongoing change, modifying especially the conditions for cold-water, spring bloom communities in temperate and Arctic regions. We investigated the effects of phytoplankton community composition on spring bloom carbon flows and nutrient stoichiometry in multiyear mesocosm experiments. Comparison of differing communities showed that community structure significantly affected C accumulation parameters, with highest particulate organic carbon (POC) buildup and dissolved organic carbon (DOC) release in diatom-dominated communities. In terms of inorganic nutrient drawdown and bloom accumulation phase, the dominating groups behaved as functional surrogates. Dominance patterns, however, significantly affected C : N : P : Chl a ratios over the whole bloom event: when diatoms were dominant, these ratios increased compared to dinoflagellate dominance or mixed communities. Diatom-dominated communities sequestered carbon up to 3.6-fold higher than the expectation based on the Redfield ratio, and 2-fold higher compared to dinoflagellate dominance. To our knowledge, this is the first experimental report of consequences of climatically driven shifts in phytoplankton dominance patterns for carbon sequestration and related biogeochemical cycles in coastal seas. Our results also highlight the need for remote sensing technologies with taxonomical resolution, as the C : Chl a ratio was strongly dependent on community composition and bloom stage. Climate-driven changes in phytoplankton dominance patterns will have far-reaching consequences for major biogeochemical cycles and need to be considered in climate change scenarios for marine systems.

  12. Aminoglycoside Modifying Enzymes

    PubMed Central

    Ramirez, Maria S.; Tolmasky, Marcelo E.

    2010-01-01

    Aminoglycosides have been an essential component of the armamentarium in the treatment of life-threatening infections. Unfortunately, their efficacy has been reduced by the surge and dissemination of resistance. In some cases the levels of resistance reached the point that rendered them virtually useless. Among many known mechanisms of resistance to aminoglycosides, enzymatic modification is the most prevalent in the clinical setting. Aminoglycoside modifying enzymes catalyze the modification at different −OH or −NH2 groups of the 2-deoxystreptamine nucleus or the sugar moieties and can be nucleotidyltranferases, phosphotransferases, or acetyltransferases. The number of aminoglycoside modifying enzymes identified to date as well as the genetic environments where the coding genes are located is impressive and there is virtually no bacteria that is unable to support enzymatic resistance to aminoglycosides. Aside from the development of new aminoglycosides refractory to as many as possible modifying enzymes there are currently two main strategies being pursued to overcome the action of aminoglycoside modifying enzymes. Their successful development would extend the useful life of existing antibiotics that have proven effective in the treatment of infections. These strategies consist of the development of inhibitors of the enzymatic action or of the expression of the modifying enzymes. PMID:20833577

  13. Direct Simulation of Magnetic Resonance Relaxation Rates and Line Shapes from Molecular Trajectories

    PubMed Central

    Rangel, David P.; Baveye, Philippe C.; Robinson, Bruce H.

    2012-01-01

    We simulate spin relaxation processes, which may be measured by either continuous wave or pulsed magnetic resonance techniques, using trajectory-based simulation methodologies. The spin–lattice relaxation rates are extracted numerically from the relaxation simulations. The rates obtained from the numerical fitting of the relaxation curves are compared to those obtained by direct simulation from the relaxation Bloch–Wangsness–Abragam– Redfield theory (BWART). We have restricted our study to anisotropic rigid-body rotational processes, and to the chemical shift anisotropy (CSA) and a single spin–spin dipolar (END) coupling mechanisms. Examples using electron paramagnetic resonance (EPR) nitroxide and nuclear magnetic resonance (NMR) deuterium quadrupolar systems are provided. The objective is to compare those rates obtained by numerical simulations with the rates obtained by BWART. There is excellent agreement between the simulated and BWART rates for a Hamiltonian describing a single spin (an electron) interacting with the bath through the chemical shift anisotropy (CSA) mechanism undergoing anisotropic rotational diffusion. In contrast, when the Hamiltonian contains both the chemical shift anisotropy (CSA) and the spin–spin dipolar (END) mechanisms, the decay rate of a single exponential fit of the simulated spin–lattice relaxation rate is up to a factor of 0.2 smaller than that predicted by BWART. When the relaxation curves are fit to a double exponential, the slow and fast rates extracted from the decay curves bound the BWART prediction. An extended BWART theory, in the literature, includes the need for multiple relaxation rates and indicates that the multiexponential decay is due to the combined effects of direct and cross-relaxation mechanisms. PMID:22540276

  14. Error Analysis of Modified Langevin Dynamics

    NASA Astrophysics Data System (ADS)

    Redon, Stephane; Stoltz, Gabriel; Trstanova, Zofia

    2016-08-01

    We consider Langevin dynamics associated with a modified kinetic energy vanishing for small momenta. This allows us to freeze slow particles, and hence avoid the re-computation of inter-particle forces, which leads to computational gains. On the other hand, the statistical error may increase since there are a priori more correlations in time. The aim of this work is first to prove the ergodicity of the modified Langevin dynamics (which fails to be hypoelliptic), and next to analyze how the asymptotic variance on ergodic averages depends on the parameters of the modified kinetic energy. Numerical results illustrate the approach, both for low-dimensional systems where we resort to a Galerkin approximation of the generator, and for more realistic systems using Monte Carlo simulations.

  15. Digital simulation program improved

    NASA Technical Reports Server (NTRS)

    Bramblett, E. K.

    1970-01-01

    Modified Integration Digital Analog Simulation /MIDAS/ program, which provides time oriented solutions to equations from system block diagram descriptions, is given greater speed, accuracy, flexibility, and applicability. Improved program incorporates additional elements for extended solution capability not readily available from analog computers.

  16. Modified Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Gilwee, W. J.

    1984-01-01

    The properties of a rubber-modified experimental epoxy resin and a standard epoxy as composite matrices were studied. In addition, a brominated epoxy resin was used in varying quantities to improve the fire resistance of the composite. The experimental resin was tris-(hydroxyphenyl)methane triglycidyl ether, known as tris epoxy novolac (TEN). The standard epoxy resin used was tetraglycidyl 4,4'-diaminodiphenyl methane (TGDDM). The above resins were modified with carboxyl-terminated butadiene acrylonitrile (CTBN) rubber. It is concluded that: (1) modification of TEN resin with bromine gives better impact resistance than rubber modification alone; (2) 25% rubber addition is necessary to obtain significant improvement in impact resistance; (3) impact resistance increases with bromine content; (4) impact velocity does not significantly affect the energy absorbed by the test sample; (5) Tg did not decline with rubber modification; and (6) TEN resin had better hot/wet properties than TGDDM resin.

  17. Modified Faraday cup

    DOEpatents

    Elmer, John W.; Teruya, Alan T.; O'Brien, Dennis W.

    1996-01-01

    A tomographic technique for measuring the current density distribution in electron beams using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams. The modified Faraday cup includes a narrow slit and is rotated by a stepper motor and can be moved in the x, y and z directions. The beam is swept across the slit perpendicular thereto and controlled by deflection coils, and the slit rotated such that waveforms are taken every few degrees form 0.degree. to 360.degree. and the waveforms are recorded by a digitizing storage oscilloscope. Two-din-tensional and three-dimensional images of the current density distribution in the beam can be reconstructed by computer tomography from this information, providing quantitative information about the beam focus and alignment.

  18. Modified Faraday cup

    DOEpatents

    Elmer, J.W.; Teruya, A.T.; O`Brien, D.W.

    1996-09-10

    A tomographic technique for measuring the current density distribution in electron beams using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams is disclosed. The modified Faraday cup includes a narrow slit and is rotated by a stepper motor and can be moved in the x, y and z directions. The beam is swept across the slit perpendicular thereto and controlled by deflection coils, and the slit rotated such that waveforms are taken every few degrees from 0{degree} to 360{degree} and the waveforms are recorded by a digitizing storage oscilloscope. Two-dimensional and three-dimensional images of the current density distribution in the beam can be reconstructed by computer tomography from this information, providing quantitative information about the beam focus and alignment. 12 figs.

  19. Genetically modified bacteriophages.

    PubMed

    Sagona, Antonia P; Grigonyte, Aurelija M; MacDonald, Paul R; Jaramillo, Alfonso

    2016-04-18

    Phages or bacteriophages, viruses that infect and replicate inside bacteria, are the most abundant microorganisms on earth. The realization that antibiotic resistance poses a substantial risk to the world's health and global economy is revitalizing phage therapy as a potential solution. The increasing ease by which phage genomes can be modified, owing to the influx of new technologies, has led to an expansion of their natural capabilities, and a reduced dependence on phage isolation from environmental sources. This review will discuss the way synthetic biology has accelerated the construction of genetically modified phages and will describe the wide range of their applications. It will further provide insight into the societal and economic benefits that derive from the use of recombinant phages in various sectors, from health to biodetection, biocontrol and the food industry.

  20. Genetically modified bacteriophages.

    PubMed

    Sagona, Antonia P; Grigonyte, Aurelija M; MacDonald, Paul R; Jaramillo, Alfonso

    2016-04-18

    Phages or bacteriophages, viruses that infect and replicate inside bacteria, are the most abundant microorganisms on earth. The realization that antibiotic resistance poses a substantial risk to the world's health and global economy is revitalizing phage therapy as a potential solution. The increasing ease by which phage genomes can be modified, owing to the influx of new technologies, has led to an expansion of their natural capabilities, and a reduced dependence on phage isolation from environmental sources. This review will discuss the way synthetic biology has accelerated the construction of genetically modified phages and will describe the wide range of their applications. It will further provide insight into the societal and economic benefits that derive from the use of recombinant phages in various sectors, from health to biodetection, biocontrol and the food industry. PMID:26906932

  1. RNA-modifying enzymes.

    PubMed

    Ferré-D'Amaré, Adrian R

    2003-02-01

    A bewildering number of post-transcriptional modifications are introduced into cellular RNAs by enzymes that are often conserved among archaea, bacteria and eukaryotes. The modifications range from those with well-understood functions, such as tRNA aminoacylation, to widespread but more mysterious ones, such as pseudouridylation. Recent structure determinations have included two types of RNA nucleobase modifying enzyme: pseudouridine synthases and tRNA guanine transglycosylases.

  2. Modified entropic force

    SciTech Connect

    Gao Changjun

    2010-04-15

    The theory of statistical thermodynamics tells us the equipartition law of energy does not hold in the limit of very low temperatures. It is found the Debye model is very successful in explaining the experimental results for most of the solid objects. Motivated by this fact, we modify the entropic force formula which is proposed very recently. Since the Unruh temperature is proportional to the strength of the gravitational field, so the modified entropic force formula is an extension of the Newtonian gravity to the weak field. On the contrary, general relativity extends Newtonian gravity to the strong field case. Corresponding to Debye temperature, there exists a Debye acceleration g{sub D}. It is found the Debye acceleration is g{sub D}=10{sup -15} N kg{sup -1}. This acceleration is very much smaller than the gravitational acceleration 10{sup -4} N kg{sup -1} which is felt by Neptune and the gravitational acceleration 10{sup -10} N kg{sup -1} felt by the Sun. Therefore, the modified entropic force can be very well approximated by the Newtonian gravity in the Solar System and in the Galaxy. With this Debye acceleration, we find the current cosmic speeding up can be explained without invoking any kind of dark energy.

  3. Absorption lineshapes of molecular aggregates revisited

    SciTech Connect

    Gelzinis, Andrius; Valkunas, Leonas; Abramavicius, Darius

    2015-04-21

    Linear absorption is the most basic optical spectroscopy technique that provides information about the electronic and vibrational degrees of freedom of molecular systems. In simulations of absorption lineshapes, often diagonal fluctuations are included using the cumulant expansion, and the off-diagonal fluctuations are accounted for either perturbatively, or phenomenologically. The accuracy of these methods is limited and their range of validity is still questionable. In this work, a systematic study of several such methods is presented by comparing the lineshapes with exact results. It is demonstrated that a non-Markovian theory for off-diagonal fluctuations, termed complex time dependent Redfield theory, gives good agreement with exact lineshapes over a wide parameter range. This theory is also computationally efficient. On the other hand, accounting for the off-diagonal fluctuations using the modified Redfield lifetimes was found to be inaccurate.

  4. Twenty-first Century Climate Simulated by HadGEM2-ES under RCP8.5 Modified to Account for the Effects of Thawing Permafrost, Wetlands and Nitrogen Limited Vegetation on CO2 and Methane Concentrations

    NASA Astrophysics Data System (ADS)

    Liddicoat, S. K.; Wiltshire, A.; Burke, E.; Gedney, N.; Jones, C.; O'connor, F. M.; Robertson, E.; Zaehle, S.

    2015-12-01

    Emissions of carbon dioxide and methane from thawing permafrost and wetlands, together with reduced uptake of CO2 by vegetation due to nitrogen limitation, are expected to exert a positive feedback of increasing magnitude on the climate system over the coming century. The current generation of Earth System models is unable to simulate interactively these climate-carbon cycle feedbacks. We have used offline methodologies to estimate a range of CO2 and methane emissions from permafrost, methane emissions from wetlands, and reduced sequestration of CO2 by nitrogen-limited vegetation under the high-end representative concentration pathway, RCP8.5. By translating these fluxes into increments to the concentration of each gas we have generated a new range of scenarios, exceeding RCP8.5 by up to 266 ppm of CO2 and 732 ppb of methane by 2100. We have used these new scenarios to force the Hadley Centre Earth System model, HadGEM2-ES, over the 21st century. We found that accounting for these feedbacks leads to additional global mean warming of up to 1.5 °C relative to the standard RCP8.5.

  5. Surface modified aerogel monoliths

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas (Inventor); Johnston, James C. (Inventor); Kuczmarski, Maria A. (Inventor); Meador, Mary Ann B. (Inventor)

    2013-01-01

    This invention comprises reinforced aerogel monoliths such as silica aerogels having a polymer coating on its outer geometric surface boundary, and to the method of preparing said aerogel monoliths. The polymer coatings on the aerogel monoliths are derived from polymer precursors selected from the group consisting of isocyanates as a precursor, precursors of epoxies, and precursors of polyimides. The coated aerogel monoliths can be modified further by encapsulating the aerogel with the polymer precursor reinforced with fibers such as carbon or glass fibers to obtain mechanically reinforced composite encapsulated aerogel monoliths.

  6. Confidentiality: a modified value.

    PubMed Central

    Emson, H E

    1988-01-01

    In its original expression as a medical value confidentiality may have been absolute; this concept has become eroded by patient consent, legal actions and change in the climate of public opinion. In particular requirements arising out of legal statutes and common law judgements have greatly modified the confidentiality of the doctor-patient relationship in societies deriving their law from English origins. Despite this, confidentiality remains a value which the physician must strive to preserve. He cannot however do this without considering its effect upon possible innocent third parties. PMID:3392723

  7. Pragmatic Aspects of Scalar Modifiers

    ERIC Educational Resources Information Center

    Sawada, Osamu

    2010-01-01

    This dissertation investigates the pragmatic aspects of scalar modifiers from the standpoint of the interface between semantics and pragmatics, focusing on (i) the (non) parallelism between the truth-conditional scalar modifiers and the non-truth-conditional scalar modifiers, (ii) the compositionality and dimensionality of non-truth-conditional…

  8. Modified constant modulus algorithm for polarization-switched QPSK.

    PubMed

    Johannisson, Pontus; Sjödin, Martin; Karlsson, Magnus; Wymeersch, Henk; Agrell, Erik; Andrekson, Peter A

    2011-04-11

    By using a generalized cost function, a modified constant modulus algorithm (CMA) that allows polarization demultiplexing and equalization of polarization-switched QPSK is found. An implementation that allows easy switching between the conventional and the modified CMA is described. Using numerical simulations, the suggested algorithm is shown to have similar performance for polarization-switched QPSK as CMA has for polarization-multiplexed QPSK.

  9. Modifying Radiation Damage

    PubMed Central

    Kim, Kwanghee; McBride, William H.

    2011-01-01

    Radiation leaves a fairly characteristic footprint in biological materials, but this is rapidly all but obliterated by the canonical biological responses to the radiation damage. The innate immune recognition systems that sense “danger” through direct radiation damage and through associated collateral damage set in motion a chain of events that, in a tissue compromised by radiation, often unwittingly result in oscillating waves of molecular and cellular responses as tissues attempt to heal. Understanding “nature’s whispers” that inform on these processes will lead to novel forms of intervention targeted more precisely towards modifying them in an appropriate and timely fashion so as to improve the healing process and prevent or mitigate the development of acute and late effects of normal tissue radiation damage, whether it be accidental, as a result of a terrorist incident, or of therapeutic treatment of cancer. Here we attempt to discuss some of the non-free radical scavenging mechanisms that modify radiation responses and comment on where we see them within a conceptual framework of an evolving radiation-induced lesion. PMID:20583981

  10. Nonlinearities in modified gravity cosmology: Signatures of modified gravity in the nonlinear matter power spectrum

    SciTech Connect

    Cui Weiguang; Zhang Pengjie; Yang Xiaohu

    2010-05-15

    A large fraction of cosmological information on dark energy and gravity is encoded in the nonlinear regime. Precision cosmology thus requires precision modeling of nonlinearities in general dark energy and modified gravity models. We modify the Gadget-2 code and run a series of N-body simulations on modified gravity cosmology to study the nonlinearities. The modified gravity model that we investigate in the present paper is characterized by a single parameter {zeta}, which determines the enhancement of particle acceleration with respect to general relativity (GR), given the identical mass distribution ({zeta}=1 in GR). The first nonlinear statistics we investigate is the nonlinear matter power spectrum at k < or approx. 3h/Mpc, which is the relevant range for robust weak lensing power spectrum modeling at l < or approx. 2000. In this study, we focus on the relative difference in the nonlinear power spectra at corresponding redshifts where different gravity models have the same linear power spectra. This particular statistics highlights the imprint of modified gravity in the nonlinear regime and the importance of including the nonlinear regime in testing GR. By design, it is less susceptible to the sample variance and numerical artifacts. We adopt a mass assignment method based on wavelet to improve the power spectrum measurement. We run a series of tests to determine the suitable simulation specifications (particle number, box size, and initial redshift). We find that, the nonlinear power spectra can differ by {approx}30% for 10% deviation from GR (|{zeta}-1|=0.1) where the rms density fluctuations reach 10. This large difference, on one hand, shows the richness of information on gravity in the corresponding scales, and on the other hand, invalidates simple extrapolations of some existing fitting formulae to modified gravity cosmology.

  11. Analytic and numerical studies of the modified betatron. [Kiloamp beams

    SciTech Connect

    Hughes, T.P.; Campbell, M.M.; Godfrey, B.B.

    1983-08-01

    The modified betatron concept has been proposed as a means of accelerating high current (kiloamp) electron beams to high energy. This device employs a toroidal magnetic field to overcome the space-charge limit on the current in a conventional betatron at low energy. In this paper, the authors look at the injection, equilibrium and stability of the modified betatron. The main emphasis is on stability. An analytic dispersion relation is derived using a cold-fluid model of the beam. The results are compared to three-dimensional simulations performed with the electromagnetic PIC code IVORY. The nonlinear development of the negative mass instability is followed in the simulations.

  12. Accurate method of modeling cluster scaling relations in modified gravity

    NASA Astrophysics Data System (ADS)

    He, Jian-hua; Li, Baojiu

    2016-06-01

    We propose a new method to model cluster scaling relations in modified gravity. Using a suite of nonradiative hydrodynamical simulations, we show that the scaling relations of accumulated gas quantities, such as the Sunyaev-Zel'dovich effect (Compton-y parameter) and the x-ray Compton-y parameter, can be accurately predicted using the known results in the Λ CDM model with a precision of ˜3 % . This method provides a reliable way to analyze the gas physics in modified gravity using the less demanding and much more efficient pure cold dark matter simulations. Our results therefore have important theoretical and practical implications in constraining gravity using cluster surveys.

  13. Modified clay sorbents

    DOEpatents

    Fogler, H. Scott; Srinivasan, Keeran R.

    1990-01-01

    A novel modified clay sorbent and method of treating industrial effluents to remove trace pollutants, such as dioxins, biphenyls, and polyaromatics such as benzo(a)pyrene and pentachlorophenol. The novel clay sorbent has a composite structure in which the interlayer space of an expandable clay, such as smectite, is filled with polyvalent or multivalent inorganic cations which forces weaker surfactant cations to locate on the surface of the clay in such an orientation that the resulting composite is hydrophilic in nature. A specific example is cetylpyridinium-hydroxy aluminum-montmorillonite. In certain embodiments, a non-expanding clay, such as kaolinite, is used and surfactant cations are necessarily located on an external surface of the clay. A specific example is cetylpyridinium-kaolinite.

  14. Chemically modified polypyrrole

    SciTech Connect

    Inagaki, T.; Skotheim, T.A.; Lee, H.S.; Okamoto, Y.; Samuelson, L.; Tripathy, S.

    1988-01-01

    Polypyrrole (PPy) films have been systematically modified with electroactive groups in the ..beta..-position to design electrode materials with specific electrochemical and surface active properties. Electrochemical copolymerization of pyrrole and 3-(6-ferrocenyl,6-hydroxyhexyl)pyrrole (P-6-Fc) yields a ferrocene functionalized polypyrrole with a controlled amount to ferrocene functionalization. And also, copolymers of pyrrole and 3-(4-(2,5- dimethoxyphenyl)butyl)pyrrole (P-MP) can be made by electrochemical polymerization and converted to the copolymers containing pH dependent electroactive hydroquinone moieties. Derivatized pyrroles have also been incorporated into Langmuir-Blodgett film structures. The surface pressure-area isotherms of 3-(13-ferrocenyl,13-hydroxytridecy)pyrrole (P-13-Fc) and the mixed monolayer of P-13-Fc and 3-n-hexadecylpyrrole (HDP) are shown. 17 refs., 4 figs.

  15. [Modified Takeuchi in adults].

    PubMed

    Jaurena, J M; Subirana, M; Montiel, J; Ruyra, X; Blasco, E; Torner, M; Caralps, J M

    1996-02-01

    Anomalous origin of left coronary artery from pulmonary artery is a rare congenital anomaly (0.25-0.46%). Mortality is high in the first months (65%). Paradoxically, some patients reach adulthood because of a net made of collaterals from the right coronary artery. Thus, we classify the entity in two ways of clinical onset: childhood and adulthood. Ideally, the best surgical approach is the arrangement of a double coronary system. The most well-known technique is the one described by Takeuchi, that links the aorta and the left coronary artery by a tunnel through the pulmonary artery, made from a pulmonary artery frontal wall flap (closing the defect with a pericardial patch). We present a case of anomalous origin of the left coronary artery in an adult, treated in our institution using a modified Takeuchi technique.

  16. Modified Composite Materials Workshop

    NASA Technical Reports Server (NTRS)

    Dicus, D. L. (Compiler)

    1978-01-01

    The reduction or elimination of the hazard which results from accidental release of graphite fibers from composite materials was studied at a workshop. At the workshop, groups were organized to consider six topics: epoxy modifications, epoxy replacement, fiber modifications, fiber coatings and new fibers, hybrids, and fiber release testing. Because of the time required to develop a new material and acquire a design data base, most of the workers concluded that a modified composite material would require about four to five years of development and testing before it could be applied to aircraft structures. The hybrid working group considered that some hybrid composites which reduce the risk of accidental fiber release might be put into service over the near term. The fiber release testing working group recommended a coordinated effort to define a suitable laboratory test.

  17. Why genetically modified crops?

    PubMed

    Jones, Jonathan D G

    2011-05-13

    This paper is intended to convey the message of the talk I gave at the Theo Murphy meeting at the Kavli Centre in July 2010. It, like the talk, is polemical, and conveys the exasperation felt by a practitioner of genetically modified (GM) plant science at its widespread misrepresentation. I argue that sustainable intensification of agriculture, using GM as well as other technologies, reduces its environmental impact by reducing pesticide applications and conserving soil carbon by enabling low till methods. Current technologies (primarily insect resistance and herbicide tolerance) have been beneficial. Moreover, the near-term pipeline of new GM methods and traits to enhance our diet, increase crop yields and reduce losses to disease is substantial. It would be perverse to spurn this approach at a time when we need every tool in the toolbox to ensure adequate food production in the short, medium and long term.

  18. Modified Sigmund sputtering theory: isotopic puzzle

    NASA Astrophysics Data System (ADS)

    Zhang, Z. L.; Zhang, L.

    2005-05-01

    The theory of anisotropic sputtering proposed by Zhang [Z.L. Zhang, Phys. Rev. B 71 026101 (2005).] and [Z.L. Zhang and L. Zhang, Radiat. Eff. Defects Solids 159(5) 301 (2004).] has been generalized to sputtering of isotopic mixtures. The present theory (modified Sigmund theory) has been shown to fit numerous simulations and experimental measurements, including energy and angular distribution of sputtered atoms. In particular, the theory has successfully solved the isotope puzzle of sputtering induced by low energy and heavy ion bombardment.

  19. Distinguishing modified gravity models

    SciTech Connect

    Brax, Philippe

    2015-10-01

    Modified gravity models with screening in local environments appear in three different guises: chameleon, K-mouflage and Vainshtein mechanisms. We propose to look for differences between these classes of models by considering cosmological observations at low redshift. In particular, we analyse the redshift dependence of the fine structure constant and the proton to electron mass ratio in each of these scenarios. When the absorption lines belong to unscreened regions of space such as dwarf galaxies, a time variation would be present for chameleons. For both K-mouflage and Vainshtein mechanisms, the cosmological time variation of the scalar field is not suppressed in both unscreened and screened environments, therefore enhancing the variation of constants and their detection prospect. We also consider the time variation of the redshift of distant objects using their spectrocopic velocities. We find that models of the K-mouflage and Vainshtein types have very different spectroscopic velocities as a function of redshift and that their differences with the Λ-CDM template should be within reach of the future ELT-HIRES observations.

  20. The modified Atkins diet.

    PubMed

    Kossoff, Eric H; Dorward, Jennifer L

    2008-11-01

    In 2003, a case series was published describing the benefits of a less restrictive ketogenic diet (KD) started as an outpatient without a fast and without any restrictions on calories, fluids, or protein. This "Modified Atkins Diet" (MAD) restricts carbohydrates to 10 g/day (15 g/day in adults) while encouraging high fat foods. Now 5 years later, there have been eight prospective and retrospective studies published on this alternative dietary therapy, both in children as well as adults. In these reports, 45 (45%) have had 50-90% seizure reduction, and 28 (28%) >90% seizure reduction, which is remarkably similar to the traditional KD. This review will discuss basics and tips to best provide the MAD, evidence for its efficacy, suggestions about the role of ketosis in dietary treatment efficacy, and its side effect profile. Lastly, the possible future benefits of this treatment for new-onset seizures, adults, neurologic conditions other than epilepsy, and developing countries of the world will be discussed.

  1. [Biotechnology using modified microorganisms].

    PubMed

    Deshayes, A F

    1992-11-01

    Few microorganisms, as compare to their high diversity, are used for human needs. They can produce molecules of interest, process fermentation, protect crops, treat wastes or clean environment. Molecular technics and genetic engineering are new tools offer to geneticists which breed microorganisms for years. Using them, it is now possible, theoretically, to introduce any gene in any organism. Some examples are given concerning genetic modifications in yeasts and lactic acid bacteria to optimize agrofood processes and to improve nutritive and flavour characteristics of fermented products like bread, beer, wine, cheese, meat, vegetable juices... In spite of scientific and industrial interest of the new technologies, limiting factors can explain that genetically modified microorganisms are not routinely used in agrofood yet. First, risks assessment on human health and environment are still in debate, but their is a consensus, within the scientific community, to consider that new characteristics of improved microorganisms are more important than the technics used for their construction. Second, regulations turn out to impose constraints susceptible to discourage technological innovations. At least, the public perception about the new technologies appears, actually, as the major factor to limit their development.

  2. Rheological Modifier Testing with DWPF Process Slurries

    SciTech Connect

    MICHAEL, STONE

    2004-02-01

    Rheological modification agents were tested on simulated SRAT and SME products to determine if a suitable agent could be found for the DWPF process slurries. The agents tested were dispersants that lower the rheological properties of slurries by preventing agglomerization. Dolapix CE64, an ethylene glycol, and Disperse-Ayd W28, a polyacrylate, were the most effective dispersants tested. Further evaluation and testing should be performed on Dolapix CE64 and Disperse-Ayd W28 to determine if implementation is possible in DWPF. The initial phase of future work will include optimization of the rheology modifier by the Illinois Institute of Technology (IIT) and development of a maximum concentration limit for the rheology modifiers. IIT has been commissioned to evaluate the properties of these chemicals to determine if the chemical makeup can be optimized to enhance the properties of these modifiers. An initial concentration limit based upon the DWPF flammability limit and other constraints should be calculated to determine the potential downstream impacts.

  3. Organic intercalation of structure modified vermiculite.

    PubMed

    Wu, Nian; Wu, Limei; Liao, Libing; Lv, Guocheng

    2015-11-01

    The experiment used cationic surfactants of different chain lengths to intercalate structure modified vermiculites. The influences of structure modification, chain length and dosage of surfactants on the intercalation behavior of vermiculites were studied, and intercalation mechanism and features of interlayer chemical reactions were discussed. Results indicate that structure modified vermiculites with different layer charge have different intercalation behavior. The basal spacing of the organic intercalated modified vermiculite is the largest when acid concentration used in structure modification is 0.003 mol/L, and increases with increasing the chain length and dosage of the organics. Molecular dynamics simulation verifies that interlayer organics align almost parallel to structure layer of vermiculite, with alkyl chain stretching to the middle of interlayer space. -N(+) groups of the three surfactants locate above the leached [SiO4], which has stronger interaction with interlayer organic cations. Electrostatic force is the main interaction force between interlayer organics and structure layer of vermiculite, and then is Van der Waals force, no chemical bond formed. PMID:26196709

  4. On a modified electrodynamics.

    PubMed

    Reiss, H R

    2012-09-01

    A modification of electrodynamics is proposed, motivated by previously unremarked paradoxes that can occur in the standard formulation. It is shown by specific examples that gauge transformations exist that radically alter the nature of a problem, even while maintaining the values of many measurable quantities. In one example, a system with energy conservation is transformed to a system where energy is not conserved. The second example possesses a ponderomotive potential in one gauge, but this important measurable quantity does not appear in the gauge-transformed system. A resolution of the paradoxes comes from noting that the change in total action arising from the interaction term in the Lagrangian density cannot always be neglected, contrary to the usual assumption. The problem arises from the information lost by employing an adiabatic cutoff of the field. This is not necessary. Its replacement by a requirement that the total action should not change with a gauge transformation amounts to a supplementary condition for gauge invariance that can be employed to preserve the physical character of the problem. It is shown that the adiabatic cutoff procedure can also be eliminated in the construction of quantum transition amplitudes, thus retaining consistency between the way in which asymptotic conditions are applied in electrodynamics and in quantum mechanics. The 'gauge-invariant electrodynamics' of Schwinger is shown to depend on an ansatz equivalent to the condition found here for maintenance of the ponderomotive potential in a gauge transformation. Among the altered viewpoints required by the modified electrodynamics, in addition to the rejection of the adiabatic cutoff, is the recognition that the electric and magnetic fields do not completely determine a physical problem, and that the electromagnetic potentials supply additional information that is required for completeness of electrodynamics.

  5. Spin-modified catalysis

    SciTech Connect

    Choudhary, R.; Manchanda, P.; Enders, A.; Balamurugan, B.; Sellmyer, D. J.; Skomski, R.; Kashyap, A.; Sykes, E. C. H.

    2015-05-07

    First-principle calculations are used to explore the use of magnetic degrees of freedom in catalysis. We use the Vienna Ab-Initio Simulation Package to investigate both L1{sub 0}-ordered FePt and CoPt bulk materials and perform supercell calculations for FePt nanoclusters containing 43 atoms. As the catalytic activity of transition-metal elements and alloys involves individual d levels, magnetic alloying strongly affects the catalytic performance, because it leads to shifts in the local densities of states and to additional peaks due to magnetic-moment formation. The peak shift persists in nanoparticles but is surface-site specific and therefore depends on cluster size. Our research indicates that small modifications in stoichiometry and cluster size are a useful tool in the search for new catalysts.

  6. Nominal Modifiers in Mandarin Chinese.

    ERIC Educational Resources Information Center

    Hou, John Y.

    In the surface structure of Chinese nominal modifiers (quantifiers, determiners, adjectives, measure phrase, relative clause, etc.) may occur either before or after a modified noun. In most of the transformational studies of Chinese syntax (e.g. Cheng 1966; Hashimoto 1966; Mei 1972; Tai 1973; Teng 1974), it has been assumed that such NP's have the…

  7. V/STOL flight simulation

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The requirements for a new research aircraft to provide in-flight V/STOL simulation were reviewed. The required capabilities were based on known limitations of ground based simulation and past/current experience with V/STOL inflight simulation. Results indicate that V/STOL inflight simulation capability is needed to aid in the design and development of high performance V/STOL aircraft. Although a new research V/STOL aircraft is preferred, an interim solution can be provided by use of the X-22A, the CH-47B, or the 4AV-8B aircraft modified for control/display flight research.

  8. SPS large array simulation. [spacetennas

    NASA Technical Reports Server (NTRS)

    Rathjen, S.; Sperber, B. R.; Nalos, E. J.

    1980-01-01

    Three types of computer simulations were developed to study the SPS microwave power transmission system (MPTS). The radially symmetric array simulation is low cost and is utilized to investigate general overall characteristics of the spacetenna at the array level only. "Tiltmain", a subarray level simulation program, is used to study the effects of system errors which modify the far-field pattern. The most recently designed program, "Modmain," takes the detail of simulation down to the RF module level and so to date is the closest numerical model of the reference design.

  9. Genetic modifiers and oligogenic inheritance.

    PubMed

    Kousi, Maria; Katsanis, Nicholas

    2015-06-01

    Despite remarkable progress in the identification of mutations that drive genetic disorders, progress in understanding the effect of genetic background on the penetrance and expressivity of causal alleles has been modest, in part because of the methodological challenges in identifying genetic modifiers. Nonetheless, the progressive discovery of modifier alleles has improved both our interpretative ability and our analytical tools to dissect such phenomena. In this review, we analyze the genetic properties and behaviors of modifiers as derived from studies in patient populations and model organisms and we highlight conceptual and technological tools used to overcome some of the challenges inherent in modifier mapping and cloning. Finally, we discuss how the identification of these modifiers has facilitated the elucidation of biological pathways and holds the potential to improve the clinical predictive value of primary causal mutations and to develop novel drug targets.

  10. Euclid Cosmological Simulations Requirements and Implementation Plan

    NASA Technical Reports Server (NTRS)

    Kiessling, Alina

    2012-01-01

    Simulations are essential for the successful undertaking of the Euclid mission. The simulations requirements for the Euclid mission are vast ! It is an enormous undertaking that includes development of software and acquisition of hardware facilities. The simulations requirements are currently being finalised - please contact myself or Elisabetta Semboloni if you would like to add/modify any r equi r ements (or if you would like to be involved in the development of the simulations).

  11. The Effects of Pre Modified Input, Interactionally Modified Input, and Modified Output on EFL Learners' Comprehension of New Vocabularies

    ERIC Educational Resources Information Center

    Maleki, Zinat; Pazhakh, AbdolReza

    2012-01-01

    The present study was an attempt to investigate the effects of premodified input, interactionally modified input and modified output on 80 EFL learners' comprehension of new words. The subjects were randomly assigned into four groups of pre modified input, interactionally modified input, modified output and unmodified (control) groups. Each group…

  12. Modified Nanodiamonds for Detoxification

    NASA Astrophysics Data System (ADS)

    Gibson, Natalie Marie

    essential for interacting with charged molecules, like OTA. Furthermore, the increased ZPs lead to improved colloidal stabilities over a wide range of pH, which is important for their interaction in the GI tract. While the dyes and OTA illustrated primarily electrostatic adsorption mechanisms, neutrally charged AfB1's adsorption was predominantly based upon the aggregate size of the ND substrate. In addition to mycotoxins, fluorescent dyes, including propidium iodide, pyranine and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), were initially utilized during methodological development. Fluorescent dye investigations helped assesses the adsorption mechanisms of NDs and demonstrated the significance of electrostatic interactions. Beyond electrostatic adsorption mechanisms, surface functional groups were also responsible for the amount of dye adsorbed, as was also true in OTA adsorption. Therefore, surface characterization was carried out for several ND samples by FTIR, TOF-SIMS and TDMS analysis. Final results of our studies show that our modified NDs perform better than yeast cells walls and other NDs but comparable to activated charcoal in the adsorption of AfB1, and outperform clay minerals in OTA studies. Moreover, it was demonstrated that adsorption can be maintained in a wide range of pH, thereby, increasing the possibility of NDs use in mycotoxins enterosorbent applications.

  13. Studies on chemically modified fibrinogen.

    PubMed

    Kloczewiak, M; Wegrzynowicz, Z; Matthias, F R; Heene, D L; Zajdel, M

    1976-04-30

    Treatment of fibrinogen with maleic acid anhydride renders fibrinogen unclottable depending on the degree of modification of the molecule. According to radioactive studies the release of fibrinopeptides by thrombin or reptilase is undisturbed. The incoagulability is due to inhibition of the polymerization process of fibrinmonomers derived from modified fibronogen, mainly caused by the increase of electronegative charges upon the fibrogen molecule. According to discelectrophoretic analysis modified fibrinogen fails to produce fragments D and E following plasmic digestion, however, may be degraded to high molecular weight products. Modified fibrinogen reveals some similarities to abnormal fibrinogens in congenital dysfibrinogenemia with regard to its functional properties.

  14. Modifiers of the ash properties

    NASA Astrophysics Data System (ADS)

    Peer, Vaclav; Najser, Jan; Pilat, Peter

    2014-08-01

    The aim of this article is to perform an experimental verification of the impact of added substances to limit or prevent sintering of solid fuel ash, which is formed during the thermochemical conversion of fuels. As a modifiers of ash sintering and melting temperature were used halloysite (aluminosilicate) and limestone, which has similar mechanism of action. Both of them act on the principle of a strong chemical adsorption of potassium ions, which largely cause a reduction of ash fusibility. Influence of the modifiers was observed after tests provided at 900, 1000, 1100 and 1200°C. Modifiers were dosed in amounts of 2, 5 and 10 wt.%.

  15. Modified polymers for gas chromatography

    NASA Technical Reports Server (NTRS)

    Woeller, F. H.; Christensen, W.; Mayer, L.

    1979-01-01

    Polymeric materials are modified to serve as stationary phase in chromatographic columns used for separation of atmospheric gases. Materials simplify and improve separation of atmospheric gases in terms of time, quantity of material needed, and sharpness of separation.

  16. Modified laparoscopic ventral mesh rectopexy.

    PubMed

    Sileri, P; Capuano, I; Franceschilli, L; Giorgi, F; Gaspari, A L

    2014-06-01

    We present a modified laparoscopic ventral mesh rectopexy procedure using biological mesh and bilateral anterior mesh fixation. The rectopexy is anterior with a minimal posterior mobilization. The rectum is symmetrically suspended to the sacral promontory through a mesorectal window.

  17. MS Disease-Modifying Medications

    MedlinePlus

    ... Contents Injectable treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Oral treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Intravenous infusion treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Managing side effects of disease- modifying ... or subcutaneous), oral and intravenous (into the vein) infusion. INJECTABLE TREATMENTS Treatment (chemical name) Manufacturer Avonex ® (interferon ...

  18. Modified acyl-ACP desaturase

    DOEpatents

    Cahoon, Edgar B.; Shanklin, John; Lindgvist, Ylva; Schneider, Gunter

    1998-01-06

    Disclosed is a methods for modifying the chain length and double bond positional specificities of a soluble plant fatty acid desaturase. More specifically, the method involves modifying amino acid contact residues in the substrate binding channel of the soluble fatty acid desaturase which contact the fatty acid. Specifically disclosed is the modification of an acyl-ACP desaturase. Amino acid contact residues which lie within the substrate binding channel are identified, and subsequently replaced with different residues to effect the modification of activity.

  19. Modified Acyl-ACP desaturase

    DOEpatents

    Cahoon, Edgar B.; Shanklin, John; Lindqvist, Ylva; Schneider, Gunter

    1999-03-30

    Disclosed is a method for modifying the chain length and double bond positional specificities of a soluble plant fatty acid desaturase. More specifically, the method involves modifying amino acid contact residues in the substrate binding channel of the soluble fatty acid desaturase which contact the fatty acid. Specifically disclosed is the modification of an acyl-ACP desaturase. Amino acid contact residues which lie within the substrate binding channel are identified, and subsequently replaced with different residues to effect the modification of activity.

  20. Genetically modified probiotics in foods.

    PubMed

    Ahmed, Farid E

    2003-11-01

    Probiotics have many potential therapeutic uses, but have not been universally accepted because of a lack of understanding of their action. Lactic acid bacteria (LAB) have been modified by traditional and genetic engineering methods to produce new varieties. Modern techniques of molecular biology have facilitated the identification of probiotic LAB strains, but only a few LAB have been modified by recombinant-DNA technology because of consumer resistance to their introduction to markets, especially in Europe.

  1. USING SIMULATION FOR POLLUTION PREVENTION

    EPA Science Inventory

    The ability to design or modify chemical processes in a way that minimizes the formation of unwanted by-products is an ongoing goal for process engineers. Two simulation and design methods are discussed here: Process Integration (PI) developed by El-Halwagi and Manousiouthakis a...

  2. Trick Simulation Environment 07

    NASA Technical Reports Server (NTRS)

    Lin, Alexander S.; Penn, John M.

    2012-01-01

    The Trick Simulation Environment is a generic simulation toolkit used for constructing and running simulations. This release includes a Monte Carlo analysis simulation framework and a data analysis package. It produces all auto documentation in XML. Also, the software is capable of inserting a malfunction at any point during the simulation. Trick 07 adds variable server output options and error messaging and is capable of using and manipulating wide characters for international support. Wide character strings are available as a fundamental type for variables processed by Trick. A Trick Monte Carlo simulation uses a statistically generated, or predetermined, set of inputs to iteratively drive the simulation. Also, there is a framework in place for optimization and solution finding where developers may iteratively modify the inputs per run based on some analysis of the outputs. The data analysis package is capable of reading data from external simulation packages such as MATLAB and Octave, as well as the common comma-separated values (CSV) format used by Excel, without the use of external converters. The file formats for MATLAB and Octave were obtained from their documentation sets, and Trick maintains generic file readers for each format. XML tags store the fields in the Trick header comments. For header files, XML tags for structures and enumerations, and the members within are stored in the auto documentation. For source code files, XML tags for each function and the calling arguments are stored in the auto documentation. When a simulation is built, a top level XML file, which includes all of the header and source code XML auto documentation files, is created in the simulation directory. Trick 07 provides an XML to TeX converter. The converter reads in header and source code XML documentation files and converts the data to TeX labels and tables suitable for inclusion in TeX documents. A malfunction insertion capability allows users to override the value of any

  3. ENVIRONMENT DEPENDENCE OF DARK MATTER HALOS IN SYMMETRON MODIFIED GRAVITY

    SciTech Connect

    Winther, Hans A.; Mota, David F.; Li Baojiu

    2012-09-10

    We investigate the environment dependence of dark matter halos in the symmetron modified gravity scenario. The symmetron is one of three known mechanisms for screening a fifth force and thereby recovering general relativity in dense environments. The effectiveness of the screening depends on both the mass of the object and the environment it lies in. Using high-resolution N-body simulations we find a significant difference, which depends on the halo's mass and environment, between the lensing and dynamical masses of dark matter halos similar to the f(R) modified gravity. The symmetron can however yield stronger signatures due to a freedom in the strength of coupling to matter.

  4. Simulation System Fidelity Assessment at the Vertical Motion Simulator

    NASA Technical Reports Server (NTRS)

    Beard, Steven D.; Reardon, Scott E.; Tobias, Eric L.; Aponso, Bimal L.

    2013-01-01

    Fidelity is a word that is often used but rarely understood when talking about groundbased simulation. Assessing the cueing fidelity of a ground based flight simulator requires a comparison to actual flight data either directly or indirectly. Two experiments were conducted at the Vertical Motion Simulator using the GenHel UH-60A Black Hawk helicopter math model that was directly compared to flight data. Prior to the experiment the simulator s motion and visual system frequency responses were measured, the aircraft math model was adjusted to account for the simulator motion system delays, and the motion system gains and washouts were tuned for the individual tasks. The tuned motion system fidelity was then assessed against the modified Sinacori criteria. The first experiments showed similar handling qualities ratings (HQRs) to actual flight for a bob-up and sidestep maneuvers. The second experiment showed equivalent HQRs between flight and simulation for the ADS33 slalom maneuver for the two pilot participants. The ADS33 vertical maneuver HQRs were mixed with one pilot rating the flight and simulation the same while the second pilot rated the simulation worse. In addition to recording HQRs on the second experiment, an experimental Simulation Fidelity Rating (SFR) scale developed by the University of Liverpool was tested for applicability to engineering simulators. A discussion of the SFR scale for use on the Vertical Motion Simulator is included in this paper.

  5. The flow of nitrogen into the euphotic zone of the Baltic Proper as a result of the vertical migration of phytoplankton: An analysis of the long-term observations and ecohydrodynamic model simulation

    NASA Astrophysics Data System (ADS)

    Kowalewski, Marek

    2015-05-01

    The effect of the vertical migration (VM) of phytoplankton on the depletion of mineral nitrogen in the water layer intermediate between the thermocline and halocline during the summer thermal stratification of the Baltic Proper was investigated. The flux of nitrogen transported to the mixed layer from the intermediate layer beneath it was estimated on the basis of long-term observations (1970-2000) made in spring and summer at station BY15 in the Gotland Deep (central part of the Baltic Proper). The total nitrogen flux was estimated at ca 60 mmol m- 2 month- 1 in spring and at ca 4.7 mmol m- 2 month- 1 in summer. The total transport of nitrogen to the euphotic zone from April to August was estimated at 129 mmol m- 2 which, assuming the Redfield ratio to hold, corresponds to a new primary production of ca 10.3 gC m- 2. The deep chlorophyll maxima linked to the VM of phytoplankton may not be remotely sensed, which causes the level of primary production calculated on their basis to be somewhat underestimated. The ProDeMo ecohydrodynamic model was modified in such a way as to take account of the VM of dinoflagellates. Comparison of the model results with measured vertical distributions of mineral nitrogen enabled the choice of an appropriate numerical algorithm and confirmed the hypothesis that dinoflagellate VM may be responsible for the depletion of mineral nitrogen beneath the thermocline.

  6. Nonlinear growth in modified gravity theories of dark energy

    SciTech Connect

    Laszlo, Istvan; Bean, Rachel

    2008-01-15

    Theoretical differences in the growth of structure offer the possibility that we might distinguish between modified gravity theories of dark energy and {lambda}CDM. A significant impediment to applying current and prospective large scale galaxy and weak lensing surveys to this problem is that, while the mildly nonlinear regime is important, there is a lack of numerical simulations of nonlinear growth in modified gravity theories. A major question exists as to whether existing analytical fits, created using simulations of standard gravity, can be confidently applied. In this paper we address this, presenting results of N-body simulations of a variety of models where gravity is altered including the Dvali, Gabadadze, and Porrati model. We consider modifications that alter the Poisson equation and also consider the presence of anisotropic shear stress that alters how particles respond to the gravitational potential gradient. We establish how well analytical fits of the matter power spectrum by Peacock and Dodds and Smith et al. are able to predict the nonlinear growth found in the simulations from z=50 up to today, and also consider implications for the weak lensing convergence power spectrum. We find that the analytical fits provide good agreement with the simulations, being within 1{sigma} of the simulation results for cases with and without anisotropic stress and for scale-dependent and independent modifications of the Poisson equation. No strong preference for either analytical fit is found.

  7. Snapshot imaging polarimeter using modified Savart polariscopes.

    PubMed

    Cao, Qizhi; Zhang, Chunmin; DeHoog, Edward

    2012-08-20

    In this paper, based on the combination of two modified Savart polariscopes, we present a snapshot imaging polarimeter and show that the carrier frequency is two times higher than that of the snapshot imaging polarimeter using two conventional Savart polariscopes. The signal-to-noise ratio and the spatial resolution of imagery in each channel are improved due to the increase of the carrier frequency when we filter the channels to recover the Stokes vector images. Moreover, compared with conventional imaging polarimetry, the remarkable advantage of the proposed instrument is that it is also simple, compact, miniature, snapshotted, and static (no moving parts). To demonstrate the feasibility of the proposed snapshot imaging polarimeter, the numerical simulation of a design example is presented in detail. PMID:22907005

  8. MODIFIED GRAVITY SPINS UP GALACTIC HALOS

    SciTech Connect

    Lee, Jounghun; Zhao, Gong-Bo; Li, Baojiu; Koyama, Kazuya

    2013-01-20

    We investigate the effect of modified gravity on the specific angular momentum of galactic halos by analyzing the halo catalogs at z = 0 from high-resolution N-body simulations for a f(R) gravity model that meets the solar-system constraint. It is shown that the galactic halos in the f(R) gravity model tend to acquire significantly higher specific angular momentum than those in the standard {Lambda}CDM model. The largest difference in the specific angular momentum distribution between these two models occurs for the case of isolated galactic halos with mass less than 10{sup 11} h {sup -1} M {sub Sun }, which are likely least shielded by the chameleon screening mechanism. As the specific angular momentum of galactic halos is rather insensitive to other cosmological parameters, it can in principle be an independent discriminator of modified gravity. We speculate a possibility of using the relative abundance of low surface brightness galaxies (LSBGs) as a test of general relativity given that the formation of the LSBGs occurs in fast spinning dark halos.

  9. Hydroxyapatite growth on cotton fibers modified chemically

    NASA Astrophysics Data System (ADS)

    Varela Caselis, J. L.; Reyes Cervantes, E.; Landeta Cortés, G.; Agustín Serrano, R.; Rubio Rosas, E.

    2014-09-01

    We have prepared carboxymethyl cellulose fibers (CMC) by chemically modifying cotton cellulose with monochloroacetic acid and calcium chloride solution. This modification favored the growth of hydroxyapatite (HAP) on the surface of the CMC fibers in contact with simulated body fluid solutions (SBF). After soaking in SBF for periods of 7, 14 and 21 days, formation of HAP was observed. Analysis by scanning electron microscopy and X-ray diffraction showed that crystallinity, crystallite size, and growth of HAP increased with the soaking time. The amount of HAP deposited on CMC fibers increased greatly after 21 days of immersion in the SBF, while the substrate surface was totally covered with hemispherical aggregates with the size of the order of 2 microns. Elemental analysis showed the presence of calcium and phosphate, with calcium/phosphate atomic ratio of 1.54. Fourier transform infrared spectroscopy bands confirmed the presence of HAP. The results suggest that cotton modified by calcium treatment has a nucleating ability and can accelerate the nucleation of HAP crystals.

  10. New variables for gyrokinetic electromagnetic simulations

    SciTech Connect

    Mishchenko, Alexey Cole, Michael; Kleiber, Ralf; Könies, Axel

    2014-05-15

    A new approach to electromagnetic gyrokinetic simulations based on modified gyrokinetic theory is described. The method is validated using a particle-in-cell code. The Toroidal Alfvén Eigenmode at low perpendicular mode numbers, the so-called “magnetohydrodynamical limit,” has been successfully simulated using this method.

  11. Simulating Evolution

    ERIC Educational Resources Information Center

    Stebbins, Robert C.; Allen, Brockenbrough

    1975-01-01

    Described are simulations that can be used to illustrate evolution by natural selection. Suggestions for simulating phenomena such as adaptive radiation, color match to background and vision of predators are offered. (BR)

  12. Autoimmunity and oxidatively modified autoantigens

    PubMed Central

    Kurien, Biji T.; Scofield, R. Hal

    2008-01-01

    Oxidative damage mediated by reactive oxygen species results in the generation of deleterious by-products. The oxidation process itself and the proteins modified by these molecules are important mediators of cell toxicity and disease pathogenesis. Aldehydic products, mainly the 4-hydroxy-2-alkenals, form adducts with proteins and make them highly immunogenic. Proteins modified in this manner have been shown to induce pathogenic antibodies in a variety of diseases including systemic lupus erythematosus (SLE), alcoholic liver disease, diabetes mellitus (DM) and rheumatoid arthritis (RA). 8-oxodeoxyguanine (oxidatively modified DNA) and low density lipoproteins (LDL) occur in SLE, a disease in which premature atherosclerosis is a serious problem. In addition, immunization with 4-hydroxy-2-nonenal (HNE) modified 60 kD Ro autoantigen induces an accelerated epitope spreading in an animal model of SLE. Advanced glycation end product (AGE) pentosidine and AGE modified IgG have been shown to correlate with RA disease activity. Oxidatively modified glutamic acid decarboxylase is important in type 1 DM, while autoantibodies against oxidized LDL are prevalent in Behcet’s disease. The fragmentation of scleroderma specific autoantigens occurs as a result of oxidative modification and is thought to be responsible for the production of autoantibodies through the release of cryptic epitopes. The administration of antioxidants is a viable untried alternative for preventing or ameliorating autoimmune disease, particularly on account of the overwhelming evidence for the involvement of oxidative damage in autoimmunity. However, this should be viewed in the light of disappointing results obtained with the use of antioxidants in cardiovascular disease. PMID:18625446

  13. Modified Acyl-ACP desaturase

    DOEpatents

    Cahoon, E.B.; Shanklin, J.; Lindqvist, Y.; Schneider, G.

    1999-03-30

    Disclosed is a method for modifying the chain length and double bond positional specificities of a soluble plant fatty acid desaturase. More specifically, the method involves modifying amino acid contact residues in the substrate binding channel of the soluble fatty acid desaturase which contact the fatty acid. Specifically disclosed is the modification of an acyl-ACP desaturase. Amino acid contact residues which lie within the substrate binding channel are identified, and subsequently replaced with different residues to effect the modification of activity. 2 figs.

  14. Synthesis of chemically modified DNA.

    PubMed

    Shivalingam, Arun; Brown, Tom

    2016-06-15

    Naturally occurring DNA is encoded by the four nucleobases adenine, cytosine, guanine and thymine. Yet minor chemical modifications to these bases, such as methylation, can significantly alter DNA function, and more drastic changes, such as replacement with unnatural base pairs, could expand its function. In order to realize the full potential of DNA in therapeutic and synthetic biology applications, our ability to 'write' long modified DNA in a controlled manner must be improved. This review highlights methods currently used for the synthesis of moderately long chemically modified nucleic acids (up to 1000 bp), their limitations and areas for future expansion. PMID:27284032

  15. Modified acyl-ACP desaturase

    DOEpatents

    Cahoon, E.B.; Shanklin, J.; Lindgvist, Y.; Schneider, G.

    1998-01-06

    Disclosed is a method for modifying the chain length and double bond positional specificities of a soluble plant fatty acid desaturase. More specifically, the method involves modifying amino acid contact residues in the substrate binding channel of the soluble fatty acid desaturase which contact the fatty acid. Specifically disclosed is the modification of an acyl-ACP desaturase. Amino acid contact residues which lie within the substrate binding channel are identified, and subsequently replaced with different residues to effect the modification of activity. 1 fig.

  16. Modified shielding jet model for twin-jet shielding analysis

    NASA Technical Reports Server (NTRS)

    Gerhold, C. H.; Gilbride, J.

    1983-01-01

    An analytical model to estimate the shielding of noise emitted from a point noise source has been developed assuming the shielding jet to be a cylinder of constant radius with uniform flow across the cross section. Comparison to experiment indicated that the model overestimates diffraction of sound around the jet in the far downstream region. The shielding jet model is modified to include widening downstream of the nozzle exit. This not only represents a more realistic model of the jet, but is also expected to improve the shielding estimate downstream. The modified jet model incorporates a Mach number dependent widening rate, a corresponding decrease in flow velocity downstream and an equivalent slug flow evaluation to retain the locally parallel flow approximation of the model development. The shielding analysis with modified jet model is compared to measured data for a subsonic isothermal air jet and a simulated hot subsonic jet. Improvement of the shielding estimate is discussed.

  17. Modifying Students' Tastes in Poetry.

    ERIC Educational Resources Information Center

    Erickson, John Edward

    To test whether student tastes in poetry could be modified by a particular method of teaching it, the poetic preferences of 751 eighth grade students were pretested and compared with the poetic choices made by a panel of English educators, 35 student teachers in English, and the students' own English teachers. Consistently, poems selected by any…

  18. Cosmological hints of modified gravity?

    NASA Astrophysics Data System (ADS)

    Di Valentino, Eleonora; Melchiorri, Alessandro; Silk, Joseph

    2016-01-01

    The recent measurements of cosmic microwave background (CMB) temperature and polarization anisotropies made by the Planck satellite have provided impressive confirmation of the Λ CDM cosmological model. However interesting hints of slight deviations from Λ CDM have been found, including a 95% C.L. preference for a "modified gravity" (MG) structure formation scenario. In this paper we confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called Alens anomaly in the CMB angular spectrum, and constrains the amplitude of matter density fluctuations to σ8=0.81 5-0.048+0.032 , in better agreement with weak lensing constraints. Moreover, we find a lower value for the reionization optical depth of τ =0.059 ±0.020 (to be compared with the value of τ =0.079 ±0.017 obtained in the standard scenario), more consistent with recent optical and UV data. We check the stability of this result by considering possible degeneracies with other parameters, including the neutrino effective number, the running of the spectral index and the amount of primordial helium. The indication for modified gravity is still present at about 95% C.L., and could become more significant if lower values of τ were to be further confirmed by future cosmological and astrophysical data. When the CMB lensing likelihood is included in the analysis the statistical significance for MG simply vanishes, indicating also the possibility of a systematic effect for this MG signal.

  19. Jogging Can Modify Disruptive Behaviors.

    ERIC Educational Resources Information Center

    Allen, Jill I.

    1980-01-01

    Jogging was used to modify disruptive behavior as part of the classroom routine for 12 learning disabled elementary-grade boys. The number of incidents of each of five negative behaviors were reduced by half following the 10-minute jogging routine. (SBH)

  20. Modified immunotherapy for alopecia areata.

    PubMed

    Yoshimasu, Takashi; Furukawa, Fukumi

    2016-07-01

    Squaric acid dibutylester (SADBE) is a commonly used contact sensitizer in immunotherapy for alopecia areata (AA). Severe contact dermatitis is induced by the currently high recommended sensitization dose of 1%-2% SADBE, often decreasing patient compliance. We assessed a modified immunotherapy for AA using SADBE at a starting concentration of 0.01% without sensitization. After one or two weeks of initial 0.01% SADBE application, the concentration of SADBE was increased gradually to 0.025%, 0.05%, 0.1%, 0.25%, 0.5%, 1% and 2% until the patients felt itching or erythema at the AA lesion site. The modified immunotherapy showed a response rate of 69.4% (25/36), equivalent to conventional immunotherapy using SADBE starting at 1%-2% sensitization. Furthermore, we investigated the combination therapy of SADBE and multiple courses of steroid pulses for AA. The response rate for combination therapy was 73.7% (28/38); however, the group receiving combination therapy showed a significant prevalence of severe AA compared with the group receiving modified immunotherapy only. We reviewed the efficacy and safety of modified immunotherapy without initial sensitization and combination therapy with immunotherapy and multiple courses of pulses for AA.

  1. Asthma Exacerbation: An Emergency Medicine Simulation Scenario

    PubMed Central

    Angus, Karen; Parsons, Michael; Cheeseman, Neil

    2015-01-01

    In the practice of emergency medicine, simulation is a valuable tool that allows medical students and postgraduate residents to develop skills in a safe environment at no risk to patients. In this report, we present a case simulation of an acute asthma exacerbation utilizing a human patient simulator. The case is designed such that it can be easily modified to accommodate the trainee’s level of expertise, allowing instructors to challenge both the novice and advanced learner alike. PMID:26180682

  2. Cluster modified projective synchronization between networks with distinct topologies

    NASA Astrophysics Data System (ADS)

    Vahedi, Shahed; Noorani, Mohd Salmi Md

    2016-02-01

    Cluster modified projective synchronization (CMPS) between two topologically distinct community networks is studied in this paper. Each cluster here has a unique dynamics at least with respect to the parameter sets. Using an adaptive feedback control gain and a matrix scaling factor, we show that CMPS between two community networks can be realized with considering minimum assumptions and imposing just few restrictions on the configuration set. We use Lyapunov stability theory for the proof and employ computer simulation to confirm our result on randomly generated community networks. Simulations also show the possibility of having hybrid synchronization between the two networks.

  3. Ultrasound speckle reduction using modified Gabor filters.

    PubMed

    Dantas, Ricardo G; Costa, Eduardo T

    2007-03-01

    B-mode ultrasound images are characterized by speckle artifact, which may make the interpretation of images difficult. One widely used method for ultrasound speckle reduction is the split spectrum processing (SSP), but the use of one-dimensional (1-D), narrow-band filters makes the resultant image experience a significant resolution loss. In order to overcome this critical drawback, we propose a novel method for speckle reduction in ultrasound medical imaging, which uses a bank of wideband 2-D directive filters, based on modified Gabor functions. Each filter is applied to the 2-D radio-frequency (RF) data, resulting in a B-mode image filtered in a given direction. The compounding of the filters outputs give rise to a final image in which speckle is reduced and the structure is enhanced. We have denoted this method as directive filtering (DF). Because the proposed filters have effectively the same bandwidth as the original image, it is possible to avoid the resolution loss caused by the use of narrow-band filters, as with SSP. The tests were carried out with both simulated and real clinical data. Using the signal-to-noise ratio (SNR) to quantify the amount of speckle of the ultrasound images, we have achieved an average SNR enhancement of 2.26 times with simulated data and 1.18 times with real clinical data.

  4. Cosmological probes of modified gravity: the nonlinear regime.

    PubMed

    Schmidt, Fabian

    2011-12-28

    We review the effects of modified gravity on large-scale structure in the nonlinear regime, focusing on f(R) gravity and the Dvali-Gabadadze-Porrati model, for which full N-body simulations have been performed. In particular, we discuss the abundance of massive halos, the nonlinear matter power spectrum and the dynamics within clusters and galaxies, with particular emphasis on the screening mechanisms present in these models. PMID:22084294

  5. Decoy state quantum key distribution with modified coherent state

    SciTech Connect

    Yin Zhenqiang; Han Zhengfu; Sun Fangwen; Guo Guangcan

    2007-07-15

    To beat photon-number splitting attack, decoy state quantum key distribution (QKD) based on the coherent state has been studied widely. We present a decoy state QKD protocol with a modified coherent state (MCS). By destructive quantum interference, a MCS with fewer multiphoton events can be obtained, which may improve the key bit rate and security distance of QKD. Through numerical simulation, we show about a 2-dB increment on the security distance for Bennett-Brassard (1984) protocol.

  6. Development of an Improved Permeability Modification Simulator

    SciTech Connect

    Gao, H.W.; Elphnick, J.

    1999-03-09

    This report describes the development of an improved permeability modification simulator performed jointly by BDM Petroleum Technologies and Schlumberger Dowell under a cooperative research and development agreement (CRADA) with the US Department of Energy. The improved simulator was developed by modifying NIPER's PC-GEL permeability modification simulator to include a radial model, a thermal energy equation, a wellbore simulator, and a fully implicit time-stepping option. The temperature-dependent gelation kinetics of a delayed gel system (DGS) is also included in the simulator.

  7. Quantum simulation

    NASA Astrophysics Data System (ADS)

    Georgescu, I. M.; Ashhab, S.; Nori, Franco

    2014-01-01

    Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry, and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins, and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

  8. Simulation Accelerator

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Under a NASA SBIR (Small Business Innovative Research) contract, (NAS5-30905), EAI Simulation Associates, Inc., developed a new digital simulation computer, Starlight(tm). With an architecture based on the analog model of computation, Starlight(tm) outperforms all other computers on a wide range of continuous system simulation. This system is used in a variety of applications, including aerospace, automotive, electric power and chemical reactors.

  9. Interactive reservoir simulation

    SciTech Connect

    McVay, D.A.; Bastian, P.A. ); Epperson, B.D. )

    1991-11-01

    This paper describes a system that allows engineers to monitor and control a reservoir simulation run during its execution. The system consists of a 3D, three-phase black-oil reservoir simulator running simultaneously with an interactive graphics pre- and postprocessor. Previous authors have described systems that allow monitoring of job execution with simultaneous graphics displays; the system described here is unique in that the engineer can modify simulator and well-control parameters during the execution. While the system will be helpful in detection and correction of time-dependent data problems, it will be very useful in optimizing reservoir management decisions in future performance projections. The system is implemented on an IBM-compatible 486 microcomputer with commercially available multitasking software, although it can be implemented easily on any microcomputer or workstation capable of multitasking. The authors show that implementation of the system required only a moderate amount of modification of the pre- and postprocessor and even less modification of the reservoir simulator.

  10. Quantitative Simulation Games

    NASA Astrophysics Data System (ADS)

    Černý, Pavol; Henzinger, Thomas A.; Radhakrishna, Arjun

    While a boolean notion of correctness is given by a preorder on systems and properties, a quantitative notion of correctness is defined by a distance function on systems and properties, where the distance between a system and a property provides a measure of "fit" or "desirability." In this article, we explore several ways how the simulation preorder can be generalized to a distance function. This is done by equipping the classical simulation game between a system and a property with quantitative objectives. In particular, for systems that satisfy a property, a quantitative simulation game can measure the "robustness" of the satisfaction, that is, how much the system can deviate from its nominal behavior while still satisfying the property. For systems that violate a property, a quantitative simulation game can measure the "seriousness" of the violation, that is, how much the property has to be modified so that it is satisfied by the system. These distances can be computed in polynomial time, since the computation reduces to the value problem in limit average games with constant weights. Finally, we demonstrate how the robustness distance can be used to measure how many transmission errors are tolerated by error correcting codes.

  11. Perioperative pharmacology: blood coagulation modifiers.

    PubMed

    Hicks, Rodney W; Wanzer, Linda J; Goeckner, Bradlee

    2011-06-01

    Blood coagulation is the process that results in the formation of a blood clot to stop bleeding from a damaged blood vessel. Various pharmacologic agents can affect the coagulation process. The American College of Chest Physicians' evidence-based practice guidelines for perioperative management of antithrombotic therapy provide guidance for anticoagulant or antiplatelet therapy and bridge therapy. Perioperative nurses must understand the pharmacologic principles of the most common blood coagulation modifiers related to perioperative use. The perioperative nurse's responsibilities regarding administration of blood coagulation modifiers include reviewing the patient's pertinent laboratory results (eg, prothrombin time, partial thromboplastin time, international normalized ratio), recognizing the underlying conditions that require blood coagulation therapy, and documenting all pertinent information. Perioperative nurses also should participate in development of detailed storage and retrieval policies related to heparin.

  12. Modified gravity inside astrophysical bodies

    SciTech Connect

    Saito, Ryo; Langlois, David; Yamauchi, Daisuke; Mizuno, Shuntaro; Gleyzes, Jérôme E-mail: yamauchi@resceu.s.u-tokyo.ac.jp E-mail: jerome.gleyzes@cea.fr

    2015-06-01

    Many theories of modified gravity, including the well studied Horndeski models, are characterized by a screening mechanism that ensures that standard gravity is recovered near astrophysical bodies. In a recently introduced class of gravitational theories that goes beyond Horndeski, it has been found that new derivative interactions lead to a partial breaking of the Vainshtein screening mechanism inside any gravitational source, although not outside. We study the impact of this new type of deviation from standard gravity on the density profile of a spherically symmetric matter distribution, in the nonrelativistic limit. For simplicity, we consider a polytropic equation of state and derive the modifications to the standard Lane-Emden equations. We also show the existence of a universal upper bound on the amplitude of this type of modified gravity, independently of the details of the equation of state.

  13. Energy conditions in modified gravity

    NASA Astrophysics Data System (ADS)

    Capozziello, Salvatore; Lobo, Francisco S. N.; Mimoso, José P.

    2014-03-01

    We consider generalized energy conditions in modified theories of gravity by taking into account the further degrees of freedom related to scalar fields and curvature invariants. The latter are usually recast as generalized geometrical fluids that have different meanings with respect to the standard matter fluids generally adopted as sources of the field equations. More specifically, in modified gravity the curvature terms are grouped in a tensor H and a coupling g(Ψi) that can be reorganized in effective Einstein field equations, as corrections to the energy-momentum tensor of matter. The formal validity of such inequalities does not assure some basic requirements such as the attractive nature of gravity, so that the energy conditions have to be considered in a wider sense.

  14. Modified muscle sparing posterolateral thoracotomy.

    PubMed Central

    Ashour, M

    1990-01-01

    A modified posterolateral thoracotomy is described that combines the advantages of complete muscle sparing through a thoracolumbar fascial slide with excellent exposure. The technique is easy to perform. The procedure was associated with relatively little postoperative pain, coughing was effective, and early ambulation was achieved. Experience with this approach in the first 49 patients suggests that it offers an attractive alternative to the standard muscle cutting posterolateral thoracotomy approach for elective procedures. PMID:2281426

  15. QGP and Modified Jet Fragmentation

    SciTech Connect

    Wang, Xin-Nian

    2005-04-18

    Recent progresses in the study of jet modification in hotmedium and their consequences in high-energy heavy-ion collisions are reviewed. In particular, I will discuss energy loss for propagating heavy quarks and the resulting modified fragmentation function. Medium modification of the parton fragmentation function due to quark recombination are formulated within finite temperature field theory and their implication on the search for deconfined quark-gluon plasma is also discussed.

  16. Using Computational Simulations to Confront Students' Mental Models

    ERIC Educational Resources Information Center

    Rodrigues, R.; Carvalho, P. Simeão

    2014-01-01

    In this paper we show an example of how to use a computational simulation to obtain visual feedback for students' mental models, and compare their predictions with the simulated system's behaviour. Additionally, we use the computational simulation to incrementally modify the students' mental models in order to accommodate new data,…

  17. Modified Pechini synthesis of tricalcium aluminate powder

    SciTech Connect

    Voicu, Georgeta Ghitulica, Cristina Daniela; Andronescu, Ecaterina

    2012-11-15

    Tricalcium aluminate (Ca{sub 3}Al{sub 2}O{sub 6}-C{sub 3}A) was obtained by a modified Pechini synthesis in order to eliminate successive thermal treatments and intermediate grinding usually performed between the two sintering steps and in order to reduce the sintering temperature. Our results indicated that pure C{sub 3}A was obtained, by a single step thermal treatment at 1300 Degree-Sign C for 4 h and 1350 Degree-Sign C for 1 h. The synthesis was confirmed by XRD, FT-IR and free lime analyses. The morphology of synthesised C{sub 3}A was assessed by electron microscopy (SEM and TEM, HRTEM) and it was observed a high tendency of the particles to form aggregates and the individual particles seem to be single crystals. The bioactivity was assessed by specimen soaking in simulated body fluid (SBF) for 7 days; the hydrate (i.e. 3CaO Bullet-Operator Al{sub 2}O{sub 3} Bullet-Operator 6H{sub 2}O formed at the C{sub 3}A surface), can act as nucleation centers for the resulted phosphate phases. - Highlights: Black-Right-Pointing-Pointer A modified Pechini synthesis was used for obtained of tricalcium aluminate. Black-Right-Pointing-Pointer C{sub 3}A was obtained at 1300 Degree-Sign C/4 h and 1350 Degree-Sign C/1 h. Black-Right-Pointing-Pointer Were eliminated successive thermal treatments and intermediate grinding. Black-Right-Pointing-Pointer The morphology of synthesised C{sub 3}A was assessed by electron microscopy (SEM, TEM). Black-Right-Pointing-Pointer Was observed a high tendency of the particles to form aggregates.

  18. Impact of Rheological Modifiers on Various Slurries Supporting DOE Waste Processing

    SciTech Connect

    Chun, Jaehun; Bredt, Paul R.; Hansen, Erich; Bhosale, Prasad S.; Berg, John C.

    2010-03-11

    Controlling the stability and subsequent rheological properties of slurries has been an important but challenging issue in nuclear waste treatment, one that previous research has yet to sufficiently address. At the Hanford and Savannah River sites, operation of the waste treatment facilities at increased solids loading reduces the evaporative load on the melter systems and thereby increases waste processing rates. However, at these higher solids loadings, increased slurry rheology becomes a significant processing issue. The current study evaluates the use of several rheological modifiers to alleviate increased slurry rheology at high waste solids concentrations. Rheological modifiers change particle interactions in slurry. For colloidal slurries, modifiers mainly alter the electrostatic and steric interactions between particles, leading to a change in slurry rheology. Weak organic acid type rheological modifiers strengthen electrostatic repulsion whereas nonionic/polymer surfactant type rheological modifiers introduce a steric repulsion. We investigated various rheological modifiers using high level waste (HLW) nuclear waste simulants characterized typically by high ionic strength and a wide range of pH from 4 to 13. Using rheological analysis, it was found that citric acid and polyacrylic acid would be good rheological modifiers for the HLW simulants tested, effectively reducing slurry rheology by 40% or more. Physical insights into the mechanisms driving stabilization by these rheological modifiers will be discussed.

  19. Simulating Science

    ERIC Educational Resources Information Center

    Markowitz, Dina; Holt, Susan

    2011-01-01

    Students use manipulative models and small-scale simulations that promote learning of complex biological concepts. The authors have developed inexpensive wet-lab simulations and manipulative models for "Diagnosing Diabetes," "A Kidney Problem?" and "A Medical Mystery." (Contains 5 figures and 3 online resources.)

  20. Motion Simulator

    NASA Technical Reports Server (NTRS)

    1993-01-01

    MOOG, Inc. supplies hydraulic actuators for the Space Shuttle. When MOOG learned NASA was interested in electric actuators for possible future use, the company designed them with assistance from Marshall Space Flight Center. They also decided to pursue the system's commercial potential. This led to partnership with InterActive Simulation, Inc. for production of cabin flight simulators for museums, expositions, etc. The resulting products, the Magic Motion Simulator 30 Series, are the first electric powered simulators. Movements are computer-guided, including free fall to heighten the sense of moving through space. A projection system provides visual effects, and the 11 speakers of a digital laser based sound system add to the realism. The electric actuators are easier to install, have lower operating costs, noise, heat and staff requirements. The U.S. Space & Rocket Center and several other organizations have purchased the simulators.

  1. Inter-Rater Reliability of the Modified Ashworth Scale and Modified Modified Ashworth Scale in Assessing Poststroke Elbow Flexor Spasticity

    ERIC Educational Resources Information Center

    Kaya, Taciser; Goksel Karatepe, Altinay; Gunaydin, Rezzan; Koc, Aysegul; Altundal Ercan, Ulku

    2011-01-01

    The Modified Ashworth Scale (MAS) is commonly used in clinical practice for grading spasticity. However, it was modified recently by omitting grade "1+" of the MAS and redefining grade "2". The aim of this study was to investigate the inter-rater reliability of MAS and modified MAS (MMAS) for the assessment of poststroke elbow flexor spasticity.…

  2. Gene transfer from genetically modified food.

    PubMed

    Gasson, M J

    2000-10-01

    The current debate about the safety of genetically modified food includes some important scientific issues where more scientific data would aid the robustness of safety evaluation. One example is the possibility of gene transfer, especially from genetically modified plant material.

  3. Observational tests of modified gravity

    SciTech Connect

    Jain, Bhuvnesh; Zhang Pengjie

    2008-09-15

    Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the Universe. Modified gravity theories have richer observational consequences for large-scale structures than conventional dark energy models, in that different observables are not described by a single growth factor even in the linear regime. We examine the relationships between perturbations in the metric potentials, density and velocity fields, and discuss strategies for measuring them using gravitational lensing, galaxy cluster abundances, galaxy clustering/dynamics, and the integrated Sachs-Wolfe effect. We show how a broad class of gravity theories can be tested by combining these probes. A robust way to interpret observations is by constraining two key functions: the ratio of the two metric potentials, and the ratio of the gravitational 'constant' in the Poisson equation to Newton's constant. We also discuss quasilinear effects that carry signatures of gravity, such as through induced three-point correlations. Clustering of dark energy can mimic features of modified gravity theories and thus confuse the search for distinct signatures of such theories. It can produce pressure perturbations and anisotropic stresses, which break the equality between the two metric potentials even in general relativity. With these two extra degrees of freedom, can a clustered dark energy model mimic modified gravity models in all observational tests? We show with specific examples that observational constraints on both the metric potentials and density perturbations can in principle distinguish modifications of gravity from dark energy models. We compare our result with other recent studies that have slightly different assumptions (and apparently contradictory conclusions)

  4. Crystallization modifiers in lipid systems.

    PubMed

    Ribeiro, Ana Paula Badan; Masuchi, Monise Helen; Miyasaki, Eriksen Koji; Domingues, Maria Aliciane Fontenele; Stroppa, Valter Luís Zuliani; de Oliveira, Glazieli Marangoni; Kieckbusch, Theo Guenter

    2015-07-01

    Crystallization of fats is a determinant physical event affecting the structure and properties of fat-based products. The stability of these processed foods is regulated by changes in the physical state of fats and alterations in their crystallization behavior. Problems like polymorphic transitions, oil migration, fat bloom development, slow crystallization and formation of crystalline aggregates stand out. The change of the crystallization behavior of lipid systems has been a strategic issue for the processing of foods, aiming at taylor made products, reducing costs, improving quality, and increasing the applicability and stability of different industrial fats. In this connection, advances in understanding the complex mechanisms that govern fat crystallization led to the development of strategies in order to modulate the conventional processes of fat structuration, based on the use of crystallization modifiers. Different components have been evaluated, such as specific triacyglycerols, partial glycerides (monoacylglycerols and diacylglycerols), free fatty acids, phospholipids and emulsifiers. The knowledge and expertise on the influence of these specific additives or minor lipids on the crystallization behavior of fat systems represents a focus of current interest for the industrial processing of oils and fats. This article presents a comprehensive review on the use of crystallization modifiers in lipid systems, especially for palm oil, cocoa butter and general purpose fats, highlighting: i) the removal, addition or fractionation of minor lipids in fat bases; ii) the use of nucleating agents to modify the crystallization process; iii) control of crystallization in lipid bases by using emulsifiers. The addition of these components into lipid systems is discussed in relation to the phenomena of nucleation, crystal growth, morphology, thermal behavior and polymorphism, with the intention of providing the reader with a complete panorama of the associated mechanisms

  5. Cosmological tests of modified gravity.

    PubMed

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years. PMID:27007681

  6. Cosmological tests of modified gravity.

    PubMed

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

  7. Cosmological tests of modified gravity

    NASA Astrophysics Data System (ADS)

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein’s theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard Λ CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

  8. Solar Simulator

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Oriel Corporation's simulators have a high pressure xenon lamp whose reflected light is processed by an optical system to produce a uniform solar beam. Because of many different types of applications, the simulators must be adjustable to replicate many different areas of the solar radiation spectrum. Simulators are laboratory tools for such purposes as testing and calibrating solar cells, or other solar energy systems, testing dyes, paints and pigments, pharmaceuticals and cosmetic preparations, plant and animal studies, food and agriculture studies and oceanographic research.

  9. Metabolomics of genetically modified crops.

    PubMed

    Simó, Carolina; Ibáñez, Clara; Valdés, Alberto; Cifuentes, Alejandro; García-Cañas, Virginia

    2014-01-01

    Metabolomic-based approaches are increasingly applied to analyse genetically modified organisms (GMOs) making it possible to obtain broader and deeper information on the composition of GMOs compared to that obtained from traditional analytical approaches. The combination in metabolomics of advanced analytical methods and bioinformatics tools provides wide chemical compositional data that contributes to corroborate (or not) the substantial equivalence and occurrence of unintended changes resulting from genetic transformation. This review provides insight into recent progress in metabolomics studies on transgenic crops focusing mainly in papers published in the last decade. PMID:25334064

  10. Ionene modified small polymeric beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor)

    1977-01-01

    Linear ionene polyquaternary cationic polymeric segments are bonded by means of the Menshutkin reaction (quaternization) to biocompatible, extremely small, porous particles containing halide or tertiary amine sites which are centers for attachment of the segments. The modified beads in the form of emulsions or suspensions offer a large, positively-charged surface area capable of irreversibly binding polyanions such as heparin, DNA, RNA or bile acids to remove them from solution or of reversibly binding monoanions such as penicillin, pesticides, sex attractants and the like for slow release from the suspension.

  11. Modified QKLOOK program, change 1

    NASA Astrophysics Data System (ADS)

    1983-07-01

    Recently, the four QKLOOK programs, in the earlier reports, were extensively modified. The modification were made to increase the usefulness and ease of use of the QKLOOK model. The changes made (1) increase the user's control of the PK/H functions used in QKLOOK, (2) allow the user to select true or incremental vulnerable areas, and (3) brought the programs in line with the FORTRAN 77 standards. All the changes are thoroughly documented. The program VAMERGE, which re-formats the QKLOOK output into a form usable by the ASALT program, has been documented and is also included in this change.

  12. Adhesives from modified soy protein

    DOEpatents

    Sun, Susan; Wang, Donghai; Zhong, Zhikai; Yang, Guang

    2008-08-26

    The, present invention provides useful adhesive compositions having similar adhesive properties to conventional UF and PPF resins. The compositions generally include a protein portion and modifying ingredient portion selected from the group consisting of carboxyl-containing compounds, aldehyde-containing compounds, epoxy group-containing compounds, and mixtures thereof. The composition is preferably prepared at a pH level at or near the isoelectric point of the protein. In other preferred forms, the adhesive composition includes a protein portion and a carboxyl-containing group portion.

  13. Metabolomics of Genetically Modified Crops

    PubMed Central

    Simó, Carolina; Ibáñez, Clara; Valdés, Alberto; Cifuentes, Alejandro; García-Cañas, Virginia

    2014-01-01

    Metabolomic-based approaches are increasingly applied to analyse genetically modified organisms (GMOs) making it possible to obtain broader and deeper information on the composition of GMOs compared to that obtained from traditional analytical approaches. The combination in metabolomics of advanced analytical methods and bioinformatics tools provides wide chemical compositional data that contributes to corroborate (or not) the substantial equivalence and occurrence of unintended changes resulting from genetic transformation. This review provides insight into recent progress in metabolomics studies on transgenic crops focusing mainly in papers published in the last decade. PMID:25334064

  14. Metabolomics of genetically modified crops.

    PubMed

    Simó, Carolina; Ibáñez, Clara; Valdés, Alberto; Cifuentes, Alejandro; García-Cañas, Virginia

    2014-10-20

    Metabolomic-based approaches are increasingly applied to analyse genetically modified organisms (GMOs) making it possible to obtain broader and deeper information on the composition of GMOs compared to that obtained from traditional analytical approaches. The combination in metabolomics of advanced analytical methods and bioinformatics tools provides wide chemical compositional data that contributes to corroborate (or not) the substantial equivalence and occurrence of unintended changes resulting from genetic transformation. This review provides insight into recent progress in metabolomics studies on transgenic crops focusing mainly in papers published in the last decade.

  15. The Modifier Effect and Property Mutability

    ERIC Educational Resources Information Center

    Hampton, James A.; Passanisi, Alessia; Jonsson, Martin L.

    2011-01-01

    The modifier effect is the reduction in perceived likelihood of a generic property sentence, when the head noun is modified. We investigated the prediction that the modifier effect would be stronger for mutable than for central properties, without finding evidence for this predicted interaction over the course of five experiments. However…

  16. Measuring cerebral hemodynamics with a modified magnetoencephalography system.

    PubMed

    Burke, Broc A; Diamond, Solomon G

    2012-12-01

    Magnetoencephalography (MEG) systems are designed to noninvasively measure magnetic fields produced by neural electrical currents. This project examines the possibility of measuring hemodynamics with an MEG system that has been modified with dc electromagnets to measure magnetic susceptibility while maintaining the capability of measuring neural dynamics. A forward model is presented that simulates the interaction of an applied magnetic field with changes in magnetic susceptibility in the brain associated with hemodynamics. Model predictions are compared with an experiment where deionized water was pumped into an inverted flask under the MEG sensor array of superconducting quantum interference device (SQUID) gradiometers (R(2) = 0.98, p < 0.001). The forward model was used to simulate the SQUID readouts from hemodynamics in the scalp and brain induced by performing the Valsalva maneuver. Experimental human subject recordings (N = 10) were made from the prefrontal region during Valsalva using concurrent measurement with the modified MEG system and near-infrared spectroscopy (NIRS). The NIRS deoxyhemoglobin signal was found to correlate significantly with the SQUID readouts (R(2) = 0.84, p < 0.01). SQUID noise was found to increase with the applied field, which will need to be mitigated in future work. These results demonstrate the potential and technical challenges of measuring cerebral hemodynamics with a modified MEG system.

  17. Estimates of the trace of the inverse of a symmetric matrix using the modified Chebyshev algorithm

    NASA Astrophysics Data System (ADS)

    Meurant, Gérard

    2009-07-01

    In this paper we study how to compute an estimate of the trace of the inverse of a symmetric matrix by using Gauss quadrature and the modified Chebyshev algorithm. As auxiliary polynomials we use the shifted Chebyshev polynomials. Since this can be too costly in computer storage for large matrices we also propose to compute the modified moments with a stochastic approach due to Hutchinson (Commun Stat Simul 18:1059-1076, 1989).

  18. Wind Simulation

    2008-12-31

    The Software consists of a spreadsheet written in Microsoft Excel that provides an hourly simulation of a wind energy system, which includes a calculation of wind turbine output as a power-curve fit of wind speed.

  19. Mission Simulators

    NASA Video Gallery

    Students will use NASA Web-based simulators to follow sequenced directions and complete ordered tasks while learning how the shuttle is made ready for flight, how the shuttle docks with the Interna...

  20. Parametrized post-Friedmann framework for modified gravity

    NASA Astrophysics Data System (ADS)

    Hu, Wayne; Sawicki, Ignacy

    2007-11-01

    We develop a parametrized post-Friedmann (PPF) framework which describes three regimes of modified gravity models that accelerate the expansion without dark energy. On large scales, the evolution of scalar metric and density perturbations must be compatible with the expansion history defined by distance measures. On intermediate scales in the linear regime, they form a scalar-tensor theory with a modified Poisson equation. On small scales in dark matter halos such as our own galaxy, modifications must be suppressed in order to satisfy stringent local tests of general relativity. We describe these regimes with three free functions and two parameters: the relationship between the two metric fluctuations, the large and intermediate scale relationships to density fluctuations, and the two scales of the transitions between the regimes. We also clarify the formal equivalence of modified gravity and generalized dark energy. The PPF description of linear fluctuation in f(R) modified action and the Dvali-Gabadadze-Porrati braneworld models show excellent agreement with explicit calculations. Lacking cosmological simulations of these models, our nonlinear halo-model description remains an ansatz but one that enables well-motivated consistency tests of general relativity. The required suppression of modifications within dark matter halos suggests that the linear and weakly nonlinear regimes are better suited for making a complementary test of general relativity than the deeply nonlinear regime.

  1. Weak lensing by voids in modified lensing potentials

    SciTech Connect

    Barreira, Alexandre; Cautun, Marius; Li, Baojiu; Baugh, Carlton M.; Pascoli, Silvia E-mail: m.c.cautun@durham.ac.uk E-mail: c.m.baugh@durham.ac.uk

    2015-08-01

    We study lensing by voids in Cubic Galileon and Nonlocal gravity cosmologies, which are examples of theories of gravity that modify the lensing potential. We find voids in the dark matter and halo density fields of N-body simulations and compute their lensing signal analytically from the void density profiles, which we show are well fit by a simple analytical formula. In the Cubic Galileon model, the modifications to gravity inside voids are not screened and they approximately double the size of the lensing effects compared to GR. The difference is largely determined by the direct effects of the fifth force on lensing and less so by the modified density profiles. For this model, we also discuss the subtle impact on the force and lensing calculations caused by the screening effects of haloes that exist in and around voids. In the Nonlocal model, the impact of the modified density profiles and the direct modifications to lensing are comparable, but they boost the lensing signal by only ≈ 10%, compared with that of GR. Overall, our results suggest that lensing by voids is a promising tool to test models of gravity that modify lensing.

  2. Investigation of modified asphalt concrete

    NASA Astrophysics Data System (ADS)

    Zimich, Vita

    2016-01-01

    Currently the problem of improving the asphalt quality is very urgent. It is used primarily as topcoats exposed to the greatest relative to the other layers of the road, dynamic load - impact and shear. The number of cars on the road, the speed of their movement, as well as the traffic intensity increase day by day. We have to upgrade motor roads, which entails a huge cost. World experience shows that the issue is urgent not only in Russia, but also in many countries in Europe, USA and Asia. Thus, the subject of research is the resistance of asphalt concrete to water and its influence on the strength of the material at different temperatures, and resistance of pavement to deformation. It is appropriate to search for new modifiers for asphaltic binder and mineral additives for asphalt mix to form in complex the skeleton of the future asphalt concrete, resistant to atmospheric condensation, soil characteristics of the road construction area, as well as the growing road transport load. The important task of the work is searching special modifying additives for bitumen binder and asphalt mixture as a whole, which will improve the quality of highways, increasing the period between repairs. The methods described in the normative-technical documentation were used for the research. The conducted research allowed reducing the frequency of road maintenance for 7 years, increasing it from 17 to 25 years.

  3. Genetic modifiers of Huntington's disease.

    PubMed

    Gusella, James F; MacDonald, Marcy E; Lee, Jong-Min

    2014-09-15

    Huntington's disease (HD) is a devastating neurodegenerative disorder that directly affects more than 1 in 10,000 persons in Western societies but, as a family disorder with a long, costly, debilitating course, it has an indirect impact on a far greater proportion of the population. Although some palliative treatments are used, no effective treatment exists for preventing clinical onset of the disorder or for delaying its inevitable progression toward premature death, approximately 15 years after diagnosis. Huntington's disease involves a movement disorder characterized by chorea, as well as a variety of psychiatric disturbances and intellectual decline, with a gradual loss of independence. A dire need exists for effective HD therapies to alleviate the suffering and costs to the individual, family, and health care system. In past decades, genetics, the study of DNA sequence variation and its consequences, provided the tools to map the HD gene to chromosome 4 and ultimately to identify its mutation as an expanded CAG trinucleotide repeat in the coding sequence of a large protein, dubbed huntingtin. Now, advances in genetic technology offer an unbiased route to the identification of genetic factors that are disease-modifying agents in human patients. Such genetic modifiers are expected to highlight processes capable of altering the course of HD and therefore to provide new, human-validated targets for traditional drug development, with the goal of developing rational treatments to delay or prevent onset of HD clinical signs.

  4. Genetic modifiers of Huntington's disease.

    PubMed

    Gusella, James F; MacDonald, Marcy E; Lee, Jong-Min

    2014-09-15

    Huntington's disease (HD) is a devastating neurodegenerative disorder that directly affects more than 1 in 10,000 persons in Western societies but, as a family disorder with a long, costly, debilitating course, it has an indirect impact on a far greater proportion of the population. Although some palliative treatments are used, no effective treatment exists for preventing clinical onset of the disorder or for delaying its inevitable progression toward premature death, approximately 15 years after diagnosis. Huntington's disease involves a movement disorder characterized by chorea, as well as a variety of psychiatric disturbances and intellectual decline, with a gradual loss of independence. A dire need exists for effective HD therapies to alleviate the suffering and costs to the individual, family, and health care system. In past decades, genetics, the study of DNA sequence variation and its consequences, provided the tools to map the HD gene to chromosome 4 and ultimately to identify its mutation as an expanded CAG trinucleotide repeat in the coding sequence of a large protein, dubbed huntingtin. Now, advances in genetic technology offer an unbiased route to the identification of genetic factors that are disease-modifying agents in human patients. Such genetic modifiers are expected to highlight processes capable of altering the course of HD and therefore to provide new, human-validated targets for traditional drug development, with the goal of developing rational treatments to delay or prevent onset of HD clinical signs. PMID:25154728

  5. Modified Bootstrap Sensitometry In Radiography

    NASA Astrophysics Data System (ADS)

    Bednarek, Daniel R.; Rudin, Stephen

    1981-04-01

    A new modified bootstrap approach to sensitometry is presented which provides H and D curves that show almost exact agreement with those obtained using conventional methods. Two bootstrap techniques are described; both involve a combination of inverse-square and stepped-wedge modulation of the radiation field and provide intensity-scale sensitometric curves as appropriate for medical radiography. H and D curves obtained with these modified techniques are compared with those obtained for screen-film combinations using inverse-square sensitometry as well as with those obtained for direct x-ray film using time-scale sensitometry. The stepped wedge of the Wisconsin X-Ray Test Cassette was used in the bootstrap approach since it provides sufficient exposure latitude to encompass the useful density range of medical x-ray film. This approach makes radiographic sensitometry quick and convenient, allowing accurate characteristic curves to be obtained for any screen-film cassette using standard diagnostic x-ray equipment.

  6. Modified sparse regularization for electrical impedance tomography.

    PubMed

    Fan, Wenru; Wang, Huaxiang; Xue, Qian; Cui, Ziqiang; Sun, Benyuan; Wang, Qi

    2016-03-01

    Electrical impedance tomography (EIT) aims to estimate the electrical properties at the interior of an object from current-voltage measurements on its boundary. It has been widely investigated due to its advantages of low cost, non-radiation, non-invasiveness, and high speed. Image reconstruction of EIT is a nonlinear and ill-posed inverse problem. Therefore, regularization techniques like Tikhonov regularization are used to solve the inverse problem. A sparse regularization based on L1 norm exhibits superiority in preserving boundary information at sharp changes or discontinuous areas in the image. However, the limitation of sparse regularization lies in the time consumption for solving the problem. In order to further improve the calculation speed of sparse regularization, a modified method based on separable approximation algorithm is proposed by using adaptive step-size and preconditioning technique. Both simulation and experimental results show the effectiveness of the proposed method in improving the image quality and real-time performance in the presence of different noise intensities and conductivity contrasts. PMID:27036798

  7. Optics Program Modified for Multithreaded Parallel Computing

    NASA Technical Reports Server (NTRS)

    Lou, John; Bedding, Dave; Basinger, Scott

    2006-01-01

    A powerful high-performance computer program for simulating and analyzing adaptive and controlled optical systems has been developed by modifying the serial version of the Modeling and Analysis for Controlled Optical Systems (MACOS) program to impart capabilities for multithreaded parallel processing on computing systems ranging from supercomputers down to Symmetric Multiprocessing (SMP) personal computers. The modifications included the incorporation of OpenMP, a portable and widely supported application interface software, that can be used to explicitly add multithreaded parallelism to an application program under a shared-memory programming model. OpenMP was applied to parallelize ray-tracing calculations, one of the major computing components in MACOS. Multithreading is also used in the diffraction propagation of light in MACOS based on pthreads [POSIX Thread, (where "POSIX" signifies a portable operating system for UNIX)]. In tests of the parallelized version of MACOS, the speedup in ray-tracing calculations was found to be linear, or proportional to the number of processors, while the speedup in diffraction calculations ranged from 50 to 60 percent, depending on the type and number of processors. The parallelized version of MACOS is portable, and, to the user, its interface is basically the same as that of the original serial version of MACOS.

  8. Modified betatron accelerator studies. Final report

    SciTech Connect

    Hughes, T.P.; Godfrey, B.B.

    1984-12-01

    This final report describes work carried out on the equilibrium and stability properties of circular accelerators. A rigid-disk beam model in which the fields are treated exactly is used to study linear instabilities. This approach has uncovered an important inductive effect which at high toroidal mode numbers leads to either stability or to a hybrid instability. A corresponding effect has been found in electron-layer geometry. The new theory also shows that moving the equilibrium position toward the inner wall can stabilize low mode numbers. With the aid of IVORY code simulation results it is shown that the transverse motion of beam partilces is a key factor in determining beam stability. The upper bound on particle circulation frequency spread is shown to be a function only of the beam major and minor radii. This leads to upper bounds on stable currents in the modified betatron. Numerical results on stability in the stellatron and reversing-solenoidal-lens betatrons are presented. In addition, the sensitivity of equilibrium particle orbits in the stellatron to initial conditions is calculated.

  9. Modified sparse regularization for electrical impedance tomography.

    PubMed

    Fan, Wenru; Wang, Huaxiang; Xue, Qian; Cui, Ziqiang; Sun, Benyuan; Wang, Qi

    2016-03-01

    Electrical impedance tomography (EIT) aims to estimate the electrical properties at the interior of an object from current-voltage measurements on its boundary. It has been widely investigated due to its advantages of low cost, non-radiation, non-invasiveness, and high speed. Image reconstruction of EIT is a nonlinear and ill-posed inverse problem. Therefore, regularization techniques like Tikhonov regularization are used to solve the inverse problem. A sparse regularization based on L1 norm exhibits superiority in preserving boundary information at sharp changes or discontinuous areas in the image. However, the limitation of sparse regularization lies in the time consumption for solving the problem. In order to further improve the calculation speed of sparse regularization, a modified method based on separable approximation algorithm is proposed by using adaptive step-size and preconditioning technique. Both simulation and experimental results show the effectiveness of the proposed method in improving the image quality and real-time performance in the presence of different noise intensities and conductivity contrasts.

  10. [Antifibrosis effect of modified forms of catalase and superoxide dismutase in experimental silicosis].

    PubMed

    Maksimenko, A V; Bezrukavnikova, L M; Grigor'eva, E L; Tishchenko, E G; Arkhipova, O G; Iaglov, V V; Torchilin, V P

    1992-01-01

    The forms of catalase modified by treatment with dextran aldehyde were obtained and studied. Efficacy of the preparations containing native and modified forms of catalase and superoxide dismutase as well as their covalent bienzyme conjugate containing catalase-dextran aldehyde-superoxide dismutase was studied in rats with simulated silicosis. The preparations were administered into rats by means of inhalation and intraperitoneal injection. Positive protective effect exhibited a mixture of native enzymes and their covalent conjugate. The most pronounced additional effect was caused by the mixture of native catalase and superoxide dismutase as compared with modified preparation of superoxide dismutase. The preparation of bienzyme containing conjugate was less effective. PMID:1384235

  11. A modified method of vibration surveillance by using the optimal control at energy performance index

    NASA Astrophysics Data System (ADS)

    Kaliński, Krzysztof J.; Galewski, Marek A.

    2015-06-01

    A method of vibration surveillance by using the optimal control at energy performance index has been creatively modified. The suggested original modification depends on consideration of direct relationship between the measured acceleration signal and the optimal control command. The paper presents the results of experiments and Hardware-in-the-loop simulations of a new active vibration reduction algorithm based on the energy performance index idea modified in such a way, that it directly utilises the acceleration feedback signal. Promising prospects towards real application of the modified method in case of the high speed milling are predicted as well.

  12. Modified generalized sample entropy and surrogate data analysis for stock markets

    NASA Astrophysics Data System (ADS)

    Xu, Mengjia; Shang, Pengjian; Huang, Jingjing

    2016-06-01

    In this paper a modified method of generalized sample entropy and surrogate data analysis is proposed as a new measure to assess the complexity of a complex dynamical system such as stock market. The method based on Hausdorff distance presents a different way of time series patterns match showing distinct behaviors of complexity. Simulations are conducted over synthetic and real-world data for providing the comparative study. Results show that the modified method is more sensitive to the change of dynamics and has richer information. In addition, exponential functions can be used to successfully fit the curves obtained from the modified method and quantify the changes of complexity for stock market data.

  13. Additive CHARMM force field for naturally occurring modified ribonucleotides

    PubMed Central

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D.

    2016-01-01

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all‐atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26841080

  14. Electrochemical Detection of Hydrazine Using Poly(dopamine)-Modified Electrodes

    PubMed Central

    Lee, Ji Young; Nguyen, Truc Ly; Park, Jun Hui; Kim, Byung-Kwon

    2016-01-01

    We have developed a simple and selective method for the electrochemical detection of hydrazine (HZ) using poly(dopamine) (pDA)-modified indium tin oxide (ITO) electrodes. Modification with pDA was easily achieved by submerging the ITO electrode in a DA solution for 30 min. The electrocatalytic oxidation of HZ on the pDA-modified ITO electrode was measured by cyclic voltammetry. In buffer solution, the concentration range for linear HZ detection was 100 µM–10 mM, and the detection limit was 1 µM. The proposed method was finally used to determine HZ in tap water to simulate the analysis of real samples. This method showed good recovery (94%–115%) and was not affected by the other species present in the tap water samples. PMID:27164108

  15. Additive CHARMM force field for naturally occurring modified ribonucleotides.

    PubMed

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D; Nilsson, Lennart

    2016-04-15

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all-atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. PMID:26841080

  16. Additive CHARMM force field for naturally occurring modified ribonucleotides.

    PubMed

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D; Nilsson, Lennart

    2016-04-15

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all-atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs.

  17. Galactic Cosmic Ray Simulator at the NASA Space Radiation Laboratory

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Slaba, Tony C.; Rusek, Adam

    2015-01-01

    The external Galactic Cosmic Ray (GCR) spectrum is significantly modified when it passes through spacecraft shielding and astronauts. One approach for simulating the GCR space radiation environment is to attempt to reproduce the unmodified, external GCR spectrum at a ground based accelerator. A possibly better approach would use the modified, shielded tissue spectrum, to select accelerator beams impinging on biological targets. NASA plans for implementation of a GCR simulator at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory will be discussed.

  18. Simulation of thick film PZT actuators with interdigitated electrodes

    NASA Astrophysics Data System (ADS)

    Zaki, Mohanad M.; Zähringer, Sandy; Schwesinger, Norbert

    2013-05-01

    This paper deals with the simulation of membrane actuators based on thick film piezoelectric ceramics with interdigitated electrodes using the finite element method. A modified piezoelectric coupling matrix is introduced to account for the piezoelectric non-linearity due to poling and actuation at high electric fields. Electrodes were fabricated on top of 250 μm thick PZT substrates which were characterized. The experimental data verified the simulation results and proved the necessity of the modified coupling matrix.

  19. Simulation of Ultrasonic-driven Gas Separations

    SciTech Connect

    Rector, David R.; Greenwood, Margaret S.; Ahmed, Salahuddin; Doctor, Steven R.; Posakony, Gerald J.; Stenkamp, Victoria S.

    2007-06-01

    The separation of components in a gas mixture is important for a wide range of applications. One method for achieving this separation is by passing a traveling acoustic wave through the gas mixture, which creates a flux of the lighter components away from the transducer. A series of simulation were performed to assess the effectiveness of this method for separating a binary mixture of argon and helium using the lattice kinetics method. The energy transport equation was modified to account for adiabatic expansion and compression. The species transport equation was modified to include a barodiffusion term. Simulations were performed on two different scales; detailed acoustic wave simulations to determine the net component flux as a function of local concentration, pressure, etc., and device scale simulations to predict the gas composition as a function of time inside a gas separation cylinder. The method is first validated using data from literature and then applied to mixtures of argon and helium. Results are presented and discussed.

  20. Simulation of ultrasonic-driven gas separations.

    PubMed

    Rector, David R; Greenwood, Margaret S; Ahmed, Salahuddin; Doctor, Steven R; Posakony, Gerry J; Stenkamp, V Susan

    2007-06-01

    The separation of components in a gas mixture is important for a wide range of applications. One method for achieving this separation is by passing a traveling acoustic wave through the gas mixture, which creates a flux of the lighter components away from the transducer. A series of simulations was performed to assess the effectiveness of this method for separating a binary mixture of argon and helium using the lattice kinetics method. The energy transport equation was modified to account for adiabatic expansion and compression. The species transport equation was modified to include a barodiffusion term. Simulations were performed on two different scales; detailed acoustic wave simulations to determine the net component flux as a function of local concentration, pressure, etc. and device scale simulations to predict the gas composition as a function of time inside a gas separation cylinder. The method is first validated using data from literature and then applied to mixtures of argon and helium. Results are presented and discussed.

  1. In vivo studies on possible health consequences of genetically modified food and feed--with particular regard to ingredients consisting of genetically modified plant materials.

    PubMed

    Pryme, Ian F; Lembcke, Rolf

    2003-01-01

    This synopsis reviews published in vivo studies on possible health consequences of genetically modified food and feed where the ingredients in question have consisted of genetically modified plant materials. The following, however, have not been taken into consideration:--ingredients consisting of genetically modified microorganisms or parts of animals/fish--ingredients produced by/from genetically modified organisms but without any DNA present--studies on consequences for the environment or biodiversity--in vitro studies or computer simulations. According to a Norwegian report "Gen-mat" (NOU 2000:29), and a more recent search in Medline and Citations Index, to our knowledge a total of ten studies have been published on the health effects of GM-foods and feeds. In this minireview the data made available in these published studies is discussed.

  2. Resorption Rate Tunable Bioceramic: Si, Zn-Modified Tricalcium Phosphate

    SciTech Connect

    Wei, Xiang

    2006-01-01

    This dissertation is organized in an alternate format. Several manuscripts which have already been published or are to be submitted for publication have been included as separate chapters. Chapter 1 is a general introduction which describes the dissertation organization and introduces the human bone and ceramic materials as bone substitute. Chapter 2 is the background and literature review on dissolution behavior of calcium phosphate, and discussion of motivation for this research. Chapter 3 is a manuscript entitled ''Si,Zn-modified tricalcium phosphate: a phase composition and crystal structure study'', which was published in ''Key Engineering Materials'' [1]. Chapter 4 gives more crystal structure details by neutron powder diffraction, which identifies the position for Si and Zn substitution and explains the stabilization mechanism of the structure. A manuscript entitled ''Crystal structure analysis of Si, Zn-modified Tricalcium phosphate by Neutron Powder Diffraction'' will be submitted to Biomaterials [2]. Chapter 5 is a manuscript, entitled ''Dissolution behavior and cytotoxicity test of Si, Zn-modified tricalcium phosphate'', which is to be submitted to Biomaterials [3]. This paper discusses the additives effect on the dissolution behavior of TCP, and cytotoxicity test result is also included. Chapter 6 is the study of hydrolysis process of {alpha}-tricalcium phosphate in the simulated body fluid, and the phase development during drying process is discussed. A manuscript entitled ''Hydrolysis of {alpha}-tricalcium phosphate in simulated body fluid and phase transformation during drying process'' is to be submitted to Biomaterials [4]. Ozan Ugurlu is included as co-authors in these two papers due to his TEM contributions. Appendix A is the general introduction of the materials synthesis, crystal structure and preliminary dissolution result. A manuscript entitled ''Resorption rate tunable bioceramic: Si and Zn-modified tricalcium phosphate'' was published in

  3. Modifying gravity at low redshift

    SciTech Connect

    Brax, Philippe; Davis, Anne-Christine; Shaw, Douglas E-mail: c.vandebruck@sheffield.ac.uk E-mail: d.shaw@qmul.ac.uk

    2010-04-01

    We consider the growth of cosmological perturbations in modified gravity models where a scalar field mediates a non-universal Yukawa force between different matter species. The growth of the density contrast is altered for scales below the Compton wave-length of the scalar field. As the universe expands, the Compton wave-length varies in time in such a way that scales which were outside the range of the scalar field force may feel it at a lower redshift. In this case, both the exponent γ measuring the growth of Cold Dark Matter perturbations and the slip function representing the ratio of the two Newtonian potentials ψ and φ may differ from their values in General Relativity at low redshift.

  4. Method of modifying a surface

    DOEpatents

    Renk, Timothy J.; Sorensen, Neil R.; Senft, Donna Cowell; Buchheit, Jr., Rudolph G.; Thompson, Michael O.; Grabowski, Kenneth S.

    2000-01-01

    The present invention provides a surface modification method that provides beneficial changes in surface properties, can modify a surface to a greater depth than previous methods, and that is suitable for industrial application. The present method comprises applying a thin-film coating to a surface of a substrate, then subjecting the coated surface to an ion beam. The ion beam power pulse heats the coated surface, leading to alloying between the material in the coating and the material of the substrate. Rapid cooling of the alloyed layer after an ion beam pulse can lead to formation of metastable alloys and microstructures not accessible by conventional alloying methods or intense ion beam treatment of the substrate alone.

  5. Chern-Simons Modified Gravity

    NASA Astrophysics Data System (ADS)

    Efstratiou, P.

    2013-09-01

    This presentation will be based on my, undergraduate, thesis at Aristotle University of Thessoliniki with the same subject, supervised by Professor Demetrios Papadopoulos. I will first present the general mathematical formulation of the Chern-Simons (CS) modified gravity, which is split in a dynamical and a non-dynamical context, and the different physical theories which suggest this modification. Then proceed by examing the possibility that the CS theory shares solutions with General Relativity in both contexts. In the non-dynamical context I will present a new, undocumented solution as well as all the other possible solutions found to date. I will conclude by arguing that General Relativity and CS Theory share any solutions in the dynamical context.

  6. Simulations of Fluvial Landscapes

    NASA Astrophysics Data System (ADS)

    Cattan, D.; Birnir, B.

    2013-12-01

    The Smith-Bretherton-Birnir (SBB) model for fluvial landsurfaces consists of a pair of partial differential equations, one governing water flow and one governing the sediment flow. Numerical solutions of these equations have been shown to provide realistic models in the evolution of fluvial landscapes. Further analysis of these equations shows that they possess scaling laws (Hack's Law) that are known to exist in nature. However, the simulations are highly dependent on the numerical methods used; with implicit methods exhibiting the correct scaling laws, but the explicit methods fail to do so. These equations, and the resulting models, help to bridge the gap between the deterministic and the stochastic theories of landscape evolution. Slight modifications of the SBB equations make the results of the model more realistic. By modifying the sediment flow equation, the model obtains more pronounced meandering rivers. Typical landsurface with rivers.

  7. Mesh-free modeling of liquid crystals using modified smoothed particle hydrodynamics.

    PubMed

    Yakutovich, M V; Care, C M; Newton, C J P; Cleaver, D J

    2010-10-01

    We present a generalization of the modified smooth particle hydrodynamics simulation technique capable of simulating static and dynamic liquid crystalline behavior. This generalization is then implemented in the context of the Qian-Sheng description of nematodynamics. To test the method, we first use it to simulate switching in both a Fréedericksz setup and a chiral hybrid aligned nematic cell. In both cases, the results obtained give excellent agreement with previously published results. We then apply the technique in a three-dimensional simulation of the switching dynamics of the post aligned bistable nematic device.

  8. Simulation Software

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Various NASA Small Business Innovation Research grants from Marshall Space Flight Center, Langley Research Center and Ames Research Center were used to develop the 'kernel' of COMCO's modeling and simulation software, the PHLEX finite element code. NASA needed it to model designs of flight vehicles; one of many customized commercial applications is UNISIM, a PHLEX-based code for analyzing underground flows in oil reservoirs for Texaco, Inc. COMCO's products simulate a computational mechanics problem, estimate the solution's error and produce the optimal hp-adapted mesh for the accuracy the user chooses. The system is also used as a research or training tool in universities and in mechanical design in industrial corporations.

  9. Simulated Craters on Venus

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Cuzzi, Jeffrey N. (Technical Monitor)

    1995-01-01

    The thick atmosphere of Venus prevents all but the largest impactors from cratering the surface. The number of small craters on Venus provides an interesting, and statistically significant test of models for the disruption and deceleration of impacting bodies. Here we compare Monte Carlo simulated crater distributions to the observed crater distribution on Venus. The simulation assumes: (1) a power law mass distribution for impactors of the form N(sub cum) alpha m (exp-b) where b=0.8; (2) isotropic incidence angles; (3) velocity at the top of the atmosphere of 20 kilometers per second (more realistic velocity distributions are also considered); (4) Schmidt-Housen crater scaling, modified such that only the normal component of the impact velocity contributes to cratering, and using crater slumping as parameterized (5) and modern populations (60% carbonaceous, 40% stone, 3% iron) and fluxes of asteroids. We use our previously developed model for the disruption and deceleration of large bodies striking thick planetary atmospheres to calculate the impact velocity at the surface as a function of impactor mass, incident velocity, and incident angle. We use a drag coefficient c(sub d) =1; other parameters are as described in Chyba et al. We set a low velocity cutoff of 500 meters per second on crater-forming impacts. Venus's craters are nicely matched by the simulated craters produced by 700 million years of striking asteroids. Shown for comparison are the simulated craters produced by incident comets over the same period, where for comets we have assumed b=0.7 and a flux at 10(exp 14) g 30% that of asteroids. Systematic uncertainties in crater scaling and crater slumping may make the surface age uncertain by a factor of two.

  10. Lactone modified viscosity modifiers useful in oleaginous compositions

    SciTech Connect

    Gutierrez, A.; Lundberg, R.D.

    1990-06-12

    This patent describes a lactone modified reaction product useful as a viscosity index improver additive for lubricating oil compositions. It comprises: the reaction produce of: oil soluble ethylene copolymer comprising within the range of about 15 to 90 wt.% ethylene and about 10 to 85 wt.% of one or more C{sub 3} to C{sub 28} alpha-olefin, having a number average molecular weight within a range of about 15,000 to 500,000 and grafted with ethylenically unsaturated C{sub 4}--C{sub 10} monocarboxylic acid or anhydride or C{sub 4}--C{sub 0} dicarboxylic acid or anhydride wherein the carboxylic acid groups or anhydride groups are located on vicinal carbon atoms; amine selected from the group consisting of amines having at least two primary amine groups and amines having at least one primary amine group and at least one secondary amine group; long chain hydrocarbyl substituted succinic anhydride or acid having 25 to 400 carbon atoms; and lactone.

  11. A GC Instrument Simulator

    NASA Astrophysics Data System (ADS)

    Armitage, D. Bruce

    1999-02-01

    the difference between the boiling point of the component and the temperature of the column. The polarity difference between the column packing and the component is also used to modify the retention time. The retention time decreases as the difference between the boiling point of the component and the temperature of the column increases, and retention time increases as the polarity of the component approaches the polarity of the column. If the temperature of the column is too low, a warning message is given and the chromatogram does not show that component. There is no "carry-over" to the next chromatogram, as might be the case for an actual instrument. Carrier-gas flow rate is fixed and is not part of the retention-time calculation. Because of this latter condition and the method used to determine retention time, this simulator is not useful for gas chromatography method development and is not intended for such use. The purpose of the simulator is to give a beginning student experience in what happens as column temperature is varied, why one might need temperature programming, why an autosampler might be useful, and the pitfalls of "smart" integrators. When students make mistakes in instrument setup with the simulator the consequences are not damaging to the simulator but might cause serious problems with a real instrument. Hardware and Software Requirements Hardware and software requirements for A GC Instrument Simulator are shown in Table 1.

    Shown (right to left) are the main instrument control window and the manual injection window from A GC Instrument Simulator.

  12. Simulating Electrophoresis.

    ERIC Educational Resources Information Center

    Moertel, Cheryl; Frutiger, Bruce

    1996-01-01

    Describes a DNA fingerprinting simulation that uses vegetable food coloring and plastic food containers instead of DNA and expensive gel electrophoresis chambers. Allows students to decipher unknown combinations of dyes in a method similar to that used to decipher samples of DNA in DNA fingerprint techniques. (JRH)

  13. Simulation Distances

    NASA Astrophysics Data System (ADS)

    Černý, Pavol; Henzinger, Thomas A.; Radhakrishna, Arjun

    Boolean notions of correctness are formalized by preorders on systems. Quantitative measures of correctness can be formalized by real-valued distance functions between systems, where the distance between implementation and specification provides a measure of "fit" or "desirability." We extend the simulation preorder to the quantitative setting, by making each player of a simulation game pay a certain price for her choices. We use the resulting games with quantitative objectives to define three different simulation distances. The correctness distance measures how much the specification must be changed in order to be satisfied by the implementation. The coverage distance measures how much the implementation restricts the degrees of freedom offered by the specification. The robustness distance measures how much a system can deviate from the implementation description without violating the specification. We consider these distances for safety as well as liveness specifications. The distances can be computed in polynomial time for safety specifications, and for liveness specifications given by weak fairness constraints. We show that the distance functions satisfy the triangle inequality, that the distance between two systems does not increase under parallel composition with a third system, and that the distance between two systems can be bounded from above and below by distances between abstractions of the two systems. These properties suggest that our simulation distances provide an appropriate basis for a quantitative theory of discrete systems. We also demonstrate how the robustness distance can be used to measure how many transmission errors are tolerated by error correcting codes.

  14. Simulating Gravity

    ERIC Educational Resources Information Center

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…

  15. Bouncing universe with modified dispersion relation

    NASA Astrophysics Data System (ADS)

    Pan, Wen-Jian; Huang, Yong-Chang

    2016-11-01

    In this paper, employing the modified dispersion relation, we have derived the general modified Friedmann equations and the corresponding modified entropy relations for the Friedmann-Robertson-Walker (FRW) Universe. In this setup, we find that when the big bounce happens, its energy scale and its corresponding modified entropy behavior are sensitive to the value of k. In contrast to the previous work with k=0, our work mainly demonstrates that the bouncing behavior for the closed Universe with k=1 appears at the normal energy limit of the modified dispersion relation introduced, and when bouncing phenomenon is in presence, its modified entropy is just equal to zero. Surprisingly, when k=-1, the bouncing behavior is in absence.

  16. Modified DNA aptamers against sweet agent aspartame.

    PubMed

    Saitoh, Hiroshi; Nakamura, Akiko; Kuwahara, Masayasu; Ozaki, Hiroaki; Sawai, Hiroaki

    2002-01-01

    We obtained a modified DNA aptamer against sweetener, aspartame, by in vitro selection method. The modified DNA was prepared from dATP, dGTP, dCTP and a modified dTTP bearing a terminal amino group at C-5 position in place of thymidine by PCR using a hyper thermophilic DNA polymerase, KOD Dash DNA polymerase. The synthetic 102-mer DNA with a 60-mer random region was used as an initial template for the PCR. The PCR-amplified modified DNA library was applied to an aspartame-agarose column, and then the bound modified DNA was eluted from the column for the affinity chromatography selection. Repeating the procedure, we selected the modified DNA aptamer against aspartame.

  17. Infectious diseases: Surveillance, genetic modification and simulation

    USGS Publications Warehouse

    Koh, H. L.; Teh, S.Y.; De Angelis, D. L.; Jiang, J.

    2011-01-01

    Infectious diseases such as influenza and dengue have the potential of becoming a worldwide pandemic that may exert immense pressures on existing medical infrastructures. Careful surveillance of these diseases, supported by consistent model simulations, provides a means for tracking the disease evolution. The integrated surveillance and simulation program is essential in devising effective early warning systems and in implementing efficient emergency preparedness and control measures. This paper presents a summary of simulation analysis on influenza A (H1N1) 2009 in Malaysia. This simulation analysis provides insightful lessons regarding how disease surveillance and simulation should be performed in the future. This paper briefly discusses the controversy over the experimental field release of genetically modified (GM) Aedes aegypti mosquito in Malaysia. Model simulations indicate that the proposed release of GM mosquitoes is neither a viable nor a sustainable control strategy. ?? 2011 WIT Press.

  18. Flight simulator fidelity assessment in a rotorcraft lateral translation maneuver

    NASA Technical Reports Server (NTRS)

    Hess, R. A.; Malsbury, T.; Atencio, A., Jr.

    1992-01-01

    A model-based methodology for assessing flight simulator fidelity in closed-loop fashion is exercised in analyzing a rotorcraft low-altitude maneuver for which flight test and simulation results were available. The addition of a handling qualities sensitivity function to a previously developed model-based assessment criteria allows an analytical comparison of both performance and handling qualities between simulation and flight test. Model predictions regarding the existence of simulator fidelity problems are corroborated by experiment. The modeling approach is used to assess analytically the effects of modifying simulator characteristics on simulator fidelity.

  19. Certification of a Modified Research Public Aircraft

    NASA Technical Reports Server (NTRS)

    Forsyth, T. J.; Reynolds, R. S.; Mountz, D. L.

    1997-01-01

    NASA Ames Research Center has several aircraft that have been modified to conduct aeronautical and scientific research. NASA's purpose is to provide research to improve safety of flight and support scientific research for Mission to Planet Earth. Our research and platform aircraft have been modified to fit the needs of the scientific and research programs. Because NASA's aircraft have been modified and operated as public aircraft, certification of airworthiness on many are not current. Some of our aircraft are military aircraft and were never certificated. This paper discusses the process of bringing a modified B200 King Air aircraft certification current to meet Federal Aviation Regulations.

  20. Contact Stress of Modified Curvilinear Gears

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Cheng; Gu, Ming-Lune

    2010-10-01

    The contact characteristics of a modified curvilinear gear set were investigated based on finite element analysis in this study. Firstly, the mathematical model of the modified curvilinear gears was developed based on the theory of gearing. Then a solid model of a modified curvilinear gear set was built by utilizing computer-aided design software. Finite element analysis enabled us to investigate the contact stress of a contact teeth pair. The variation and distribution of the contact stresses and bending stresses are also studied under different gear design parameters. Finally, illustrative examples were presented to demonstrate the contact characteristics of the modified curvilinear gears.

  1. Geometry of modified Newtonian dynamics

    NASA Astrophysics Data System (ADS)

    Skordis, Constantinos; Zlosnik, Tom

    2012-02-01

    Modified Newtonian dynamics is an empirical modification to Poisson’s equation which has had success in accounting for the “gravitational field” Φ in a variety of astrophysical systems. The field Φ may be interpreted in terms of the weak-field limit of a variety of spacetime geometries. Here we consider three of these geometries in a more comprehensive manner and look at the effect on timelike and null geodesics. In particular we consider the aquadratic Lagrangian (AQUAL) theory, tensor-vector-scalar (TeVeS) theory and generalized Einstein-aether theory. We uncover a number of novel features, some of which are specific to the theory considered while others are generic. In the case of AQUAL and TeVeS theories, the spacetime exhibits an excess (AQUAL) or deficit TeVeS solid angle akin to the case of a Barriola-Vilenkin global monopole. In the case of generalized Einstein-aether, a disformal symmetry of the action emerges in the limit of ∇→Φ→0. Finally, in all theories studied, massive particles can never reach spatial infinity while photons can do so only after experiencing infinite redshift.

  2. Photodegradation of thermally modified wood.

    PubMed

    Srinivas, Kavyashree; Pandey, Krishna K

    2012-12-01

    Natural wood, being biological material, undergoes rapid degradation by ultraviolet (UV) radiations and other environmental factors under outdoor exposure. In order to protect wood from such degradation, the chemical structure of wood is altered by chemical modification or heat treatment. In the present study, heat treated specimens of rubberwood (Hevea brasiliensis) were exposed to xenon light source in a weather-o-meter for different periods up to 300 h. Photostability of modified and unmodified wood was evaluated in terms of colour and chemical changes. Light coloured untreated wood became dark upon UV irradiation whereas, dark colour of heat treated wood lightened on UV exposure. CIE lightness parameter (L(*)) decreased for untreated wood whereas its value increased for heat treated wood upon irradiation. Other colour coordinates a(*) and b(*) increased with exposure duration for both untreated and heat treated wood. The overall colour change (ΔE(*)) increased for both untreated and heat treated wood. The Fourier Transform Infrared (FTIR) spectroscopic studies revealed severe lignin degradation of heat treated wood due to UV light exposure. Colour changes and FTIR measurements indicate that thermal modification of wood was ineffective in restricting light induced colour changes and photodegradation of wood polymers.

  3. Nonderivative modified gravity: a classification

    SciTech Connect

    Comelli, D.; Nesti, F.; Pilo, L. E-mail: fabrizio.nesti@irb.hr

    2014-11-01

    We analyze the theories of gravity modified by a generic nonderivative potential built from the metric, under the minimal requirement of unbroken spatial rotations. Using the canonical analysis, we classify the potentials V according to the number of degrees of freedom (DoF) that propagate at the nonperturbative level. We then compare the nonperturbative results with the perturbative DoF propagating around Minkowski and FRW backgrounds. A generic V implies 6 propagating DoF at the non-perturbative level, with a ghost on Minkowski background. There exist potentials which propagate 5 DoF, as already studied in previous works. Here, no V with unbroken rotational invariance admitting 4 DoF is found. Theories with 3 DoF turn out to be strongly coupled on Minkowski background. Finally, potentials with only the 2 DoF of a massive graviton exist. Their effect on cosmology is simply equivalent to a cosmological constant. Potentials with 2 or 5 DoF and explicit time dependence appear to be a further viable possibility.

  4. Genetically modified organisms and monitoring.

    PubMed

    Diamand, E

    1999-12-01

    The genetic modification of organisms for food use has raised serious concern about the potential for adverse effects on the environment, ecosystems and on the health of humans and animals. As a relatively new technology, its impacts remain uncertain but could range from disturbances to the genetic functioning of individual organisms to a reduction in the biodiversity of farmland. As a result, the question of how to monitor for potential impacts is beset with problems. The fact that genetic modification can be used on a range of organisms for a variety of purposes means that those developing monitoring systems will need to be as imaginative as those developing GMOs. In the case of genetically modified organisms (GMOs) for food use, concern has focussed on the transfer of genes to other organisms, the potential for effects on non-target organisms, or on the health of humans and animals, and the likelihood of adverse effects on wildlife due to changes in farming practice. As with other new and unfamiliar technologies, genetic modification is also plagued by the problem of uncertainty. Novel genes are inserted randomly into the genome of the host organisms, and this leads to the possibility of unexpected effects. Unanticipated environmental disasters, such as the concentration of persistent organic pollutants in ecosystems at high latitudes, have highlighted the need for monitoring despite the obvious difficulties inherent in monitoring for unexpected effects.

  5. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1984-01-01

    The results of a program designed to develop tough imide modified epoxy resins cured by bisimide amine (BIA) hardeners are described. State-of-the-art epoxides MY720 and DER383 were used, and four bismide amines were evaluated. These were the BIA's derived from the 6F anhydride (4,4'-(hexafluoroisopropylidene) bis(phthalic anhydride) and the diamines 3,3'-diaminodiphynyl sulfone, 4,4'-oxygianiline, 4,4'-methylene dianiline, and 1,12-dodecane diamine. A key intermediate, designated 6F anhydride, is required for the synthesis of the bisimide amines. Reaction parameters to synthesize a precursor to the 6F anhydride (6FHC) in high yields were investigated. The catalyst trifluoromethane sulfonic acid was studied. Although small scale runs yielded the 6FHC in 50 percent yield, efforts to ranslate these results to a larger scale synthesis gave the 6FHC in only 9 percent yield. Results show that the concept of using bisimide amine as curing agents to improve the toughness properties of epoxies is valid.

  6. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.; Pater, R. H.

    1981-01-01

    High char yield epoxy using novel bisimide amines (BIA's) as curing agents with a state of the art epoxy resin was developed. Stoichiometric quantities of the epoxy resin and the BIA's were studied to determine the cure cycle required for preparation of resin specimens. The bisimide cured epoxies were designated IME's (imide modified epoxy). The physical, thermal and mechanical properties of these novel resins were determined. The levels of moisture absorption exhibited by the bisimide amine cured expoxies (IME's) were considerably lower than the state of the art epoxies. The strain-to-failure of the control resin system was improved 25% by replacement of DDS with 6F-DDS. Each BIA containing resin exhibited twice the char yield of the control resin MY 720/DDS. Graphite fiber reinforced control (C) and IME resins were fabricated and characterized. Two of the composite systems showed superior properties compared to the other Celion 6000/IME composite systems and state of the art graphite epoxy systems. The two systems exhibited excellent wet shear and flexural strengths and moduli at 300 and 350 F.

  7. Traceability of genetically modified organisms.

    PubMed

    Aarts, Henk J M; van Rie, Jean-Paul P F; Kok, Esther J

    2002-01-01

    EU regulations stipulate the labeling of food products containing genetically modified organisms (GMOs) unless the GMO content is due to adventitious and unintended 'contamination' and not exceeding the 1% level at ingredient basis. In addition, member states have to ensure full traceability at all stages of the placing on the market of GMOs. Both requirements ensure consumers 'right to know', facilitate enforcement of regulatory requirements and are of importance for environmental monitoring and postmarket surveillance. Besides administrative procedures, such as used in quality certification systems, the significance of adequate molecular methods becomes more and more apparent. During the last decade a considerable number of molecular methods have been developed and validated that enable the detection, identification and quantification of GMO impurities. Most of them rely on the PCR technology and can only detect one specific stretch of DNA. It can, however, be anticipated that in the near future the situation will become more complex. The number of GMO varieties, including 'stacked-gene' varieties, which will enter the European Market will increase and it is likely that these varieties will harbor more variable constructs. New tools will be necessary to keep up with these developments. One of the most promising techniques is microarray analysis. This technique enables the screening for a large number of different GMOs within a single experiment.

  8. Evaluation of anti-freeze viscosity modifier for potential external tank applications

    NASA Technical Reports Server (NTRS)

    Lynn, R. O. L.

    1981-01-01

    Viscosity modifiers and gelling agents were evaluated in combination with ethylene glycol and dimethyl sulfoxide water eutectics. Pectin and agarose are found to gel these eutectics effectively in low concentration, but the anti-freeze protection afforded by these compositions is found to be marginal in simulations of the intended applications. Oxygen vent shutters and vertical metallic surfaces were simulated, with water supplied as a spray, dropwise, and by condensation from the air.

  9. Guided crowd dynamics via modified social force model

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoxia; Dong, Hairong; Wang, Qianling; Chen, Yao; Hu, Xiaoming

    2014-10-01

    Pedestrian dynamics is of great theoretical significance for strategy design of emergency evacuation. Modification of pedestrian dynamics based on the social force model is presented to better reflect pedestrians' behavioral characteristics in emergency. Specifically, the modified model can be used for guided crowd dynamics in large-scale public places such as subway stations and stadiums. This guided crowd model is validated by explicitly comparing its density-speed and density-flow diagrams with fundamental diagrams. Some social phenomena such as gathering, balance and conflicts are clearly observed in simulation, which further illustrate the effectiveness of the proposed modeling method. Also, time delay for pedestrians with time-dependent desired velocities is observed and explained using the established model in this paper. Furthermore, this guided crowd model is applied to the simulation system of Beijing South Railway Station for predictive evacuation experiments.

  10. Multibody simulation

    NASA Astrophysics Data System (ADS)

    Cheng, Yen-Ming

    Simulation of the dynamics of physical systems is an important aspect of the engineering discipline for approximating the dynamics of real life. The simulation of complex multibody systems to an acceptable degree of accuracy involves the mathematical modeling and computer implementation of systems such as mechanisms and vehicles comprised of multiple parts. In this dissertation, new algorithms are developed for multibody simulation using a rather general mathematical model. Both open-tree and closed-loop topologies are implemented. Constraints, specifically, joint constraints, are investigated. A new algorithm is developed that projects the original configuration space into the unconstrained orthogonal subspace, thereby reducing the dimension of the system equations without resorting to complicated transformations. The reduced set of equations not only increases the simulation speed, but also improves the numerical accuracy of the simulation results by reducing the number of calculations performed. Constraint forces can easily be obtained if required for analyzing the multibody system. Algorithms by themselves are not immediately useful to users. A program was developed to implement the algorithms. The program, which was written in C/C++, incorporated the use of Microsoft Windows Application Programming Interfaces (Windows API), Microsoft Foundation Classes (MFC), and OpenGL graphics language. The system states are integrated by applying standard numerical techniques for integrating a set of first-order differential equations. Accelerations and constraint forces are obtained using direct and/or iterative techniques for solving a set of simultaneous equations. With today's powerful computers, a graphical interface becomes feasible to serve as the communicator between the program and the user. The software therefore includes a graphical user interface. Concurrent graphical animations of the motion of the system simulated are created. These are important to the user

  11. Improved wind and precipitation forecasts over South China using a modified orographic drag parameterization scheme

    NASA Astrophysics Data System (ADS)

    Zhong, Shuixin; Chen, Zitong

    2015-02-01

    To improve the wind and precipitation forecasts over South China, a modified orographic drag parameterization (OP) scheme that considers both the gravity wave drag (GWD) and the mountain blocking drag (MBD) effects was implemented in the Global/Regional Assimilation and Prediction System Tropical Mesoscale Model (GRAPES_TMM). Simulations were performed over one month starting from 1200 UTC 19 June 2013. The initial and lateral boundary conditions were obtained from the NCEP global forecast system output. The simulation results were compared among a control (CTL) experiment without the OP scheme, a GWDO experiment with the OP scheme that considers only the GWD effect, and an MBD experiment with the modified OP scheme (including both GWD and MBD). The simulation with the modified OP scheme successfully captured the main features of precipitation, including its distribution and intensity, and improved the wind circulation forecast in the lower troposphere. The modified OP scheme appears to improve the wind forecast by accelerating the ascending air motion and reinforcing the convergence in the rainfall area. Overall, the modified OP scheme exerts positive impacts on the forecast of large-scale atmospheric fields in South China.

  12. Simulating Combustion

    NASA Astrophysics Data System (ADS)

    Merker, G.; Schwarz, C.; Stiesch, G.; Otto, F.

    The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be used as the engineers testbench following the rules and recommendations described here.

  13. Interaction of Surface Modified Carbon Nanotubes with Supercritical Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Baysal, Nihat; Unsal, Banu; Ozisik, Rahmi

    2006-03-01

    The properties of carbon nanotube (CNT)-polymer nanocomposites are far below than those calculated, mainly due to poor dispersion or interface quality. This is particularly difficult for single walled carbon nanotubes (SWNTs) as they tend to form bundles or ropes that are difficult to exfoliate. Supercritical fluid (SCF) assisted processing is one of the methods that can be used to exfoliate/disperse CNTs along with modifiying the interface of the CNTs. Molecular dynamics simulations were performed to understand how the surface modifiers behave near SWNT surface with and without the presence of SCF molecules. It is also important to understand the diffusivity of SCF molecules between SWNT bundles and the effect of surface modifiers on diffusion. Octane and n-perflourooctane molecules were used as surface modifiers with varying tethering density and carbon dioxide (CO2) was chosen as the SCF. Results showed that the system with highest number of n-perfluorooctanes presented the highest degree of success in separating the SWNTs in the presence of CO2.

  14. Modified multi-load method for nonlinear source characterisation

    NASA Astrophysics Data System (ADS)

    Rämmal, Hans; Bodén, Hans

    2007-02-01

    Linear frequency domain prediction codes are useful for calculation of low-frequency sound transmission in duct and pipe systems. To calculate insertion loss of mufflers or the level of radiated sound information about the acoustic source is needed. The source model used in the low-frequency plane wave range is the linear time invariant one-port model. The acoustic source data is usually obtained from experimental tests where multi-load methods and especially the two-load method are most commonly used. The exhaust pulsations of for example an IC-engine are of high level, and the engine is not a perfectly linear and time invariant source. It is therefore of interest to develop source models and experimental techniques that try to take this nonlinearity into account. In this paper a modified version of the two-load method to improve the characterisation of nonlinear acoustic one-port sources has been developed and tested. Simulation results as well as experimental data from various source configurations for a modified compressor and experimental data from 6-cylinder turbocharged truck diesel engine were used to validate the method. The influence of parameters controlling the linearity of the system was investigated. The time-variance of the source model was varied and the accuracy of source characterisation results using the two-load method and the modified two-load method was evaluated.

  15. a Modified Method for Polarimetric SAR Calibration Algorithm

    NASA Astrophysics Data System (ADS)

    Liao, L.; Li, P.; Yang, J.

    2013-07-01

    Present fully polarimetric synthetic aperture radar (SAR) systems often update calibration techniques to further enhance the accuracy to the polarimetric data. In this paper, we propose a modified method to estimate the value of crosstalk based on the corrected observed value. Since Ainsworth calibration algorithm firstly set the value of k to be one. And the value of k relates to the copolarization channel imbalance .We consider the effects of value of k and analyze it. Through comparison to crosstalk results between the stimulated parameters and the estimated parameters, we assume high co-polarization channel imbalance will be obviously to affect crosstalk results. Then, used covariance observation value of the initial value of k rewrites the model to solve related parameters. And crosstalk parameter is calculated by the same iterative method. To verify the effect of the modified calibration method, this letter compares the accuracy of the two methods using the simulated polarimetric SAR data and Chinese airborne X-band polarimetric SAR data. The results confirm that the modified method tends to get more accurate crosstalk results.

  16. Numerical Propulsion System Simulation for Space Transportation

    NASA Technical Reports Server (NTRS)

    Owen, Karl

    2000-01-01

    Current system simulations are mature, difficult to modify, and poorly documented. Probabilistic life prediction techniques for space applications are in their early application stage. Many parts of the full system, variable fidelity simulation, have been demonstrated individually or technology is available from aeronautical applications. A 20% reduction in time to design with improvements in performance and risk reduction is anticipated. GRC software development will proceed with similar development efforts in aeronautical simulations. Where appropriate, parallel efforts will be encouraged/tracked in high risk areas until success is assured.

  17. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1982-01-01

    Results of a program designed to develop tough imide modified epoxy (IME) resins cured by bisimide amine (BIA) hardeners are presented. State of the art epoxy resin, MY720, was used. Three aromatic bisimide amines and one aromatic aliphatic BIA were evaluated. BIA's derived from 6F anhydride (3,3 prime 4,4 prime-(hexafluoro isopropyl idene) bis (phthalic anhydride) and diamines, 3,3 prime-diam nodiphenyl sulfone (3,3 prime-DDS), 4,4 prime-diamino diphenyl sulfone (4,4 prime-DDS), 1.12-dodecane diamine (1,12-DDA) were used. BIA's were abbreviated 6F-3,3 prime-DDS, 6F-4,4 prime-DDS, 6F-3,3 prime-DDS-4,4 prime DDS, and 6F-3,3 prime-DDS-1,12-DDA corresponding to 6F anhydride and diamines mentioned. Epoxy resin and BIA's (MY720/6F-3,3 prime-DDS, MY720/6F-3,3 prime-DDS-4,4 prime-DDS, MY720/6F-3,3 prime-DDS-1,12-DDA and a 50:50 mixture of a BIA and parent diamine, MY720/6F-3,3 prime-DDS/3,3 prime-DDS, MY720/6F-3,3 prime-DDS-4,4 prime-DDS/3,3 prime-DDS, MY720/6F-3,3 prime-DDS-1,12-DDA/3,3 prime-DDS were studied to determine effect of structure and composition. Effect of the addition of two commercial epoxies, glyamine 200 and glyamine 100 on the properties of several formulations was evaluated. Bisimide amine cured epoxies were designated IME's (imide modified epoxy). Physical, thermal and mechanical properties of these resins were determined. Moisture absorption in boiling water exhibited by several of the IME's was considerably lower than the state of the art epoxies (from 3.2% for the control and state of the art to 2.0 wt% moisture absorption). Char yields are increased from 20% for control and state of the art epoxies to 40% for IME resins. Relative toughness characteristics of IME resins were measured by 10 deg off axis tensile tests of Celion 6000/IME composites. Results show that IME's containing 6F-3,3 prime-DDS or 6F-3,3 prime-DDS-1,12-DDA improved the "toughness" characteristics of composites by about 35% (tensile strength), about 35% (intralaminar shear

  18. X-0557 modified Steven tests.

    SciTech Connect

    Idar, D. J.; Mang, J. T.; Straight, J. W.; Schafstall, P.; Pacheco, A. H.; Osborn, M. A.; Coulter, W. L.; DeLuca, R. A.; Chavez, Peter J., Jr.

    2004-01-01

    Low-velocity mechanical impact leading to unintentional reaction is of concern in accident scenarios involving the handling, transport, and storage of high explosives (HE). Various experimental techniques, from small- to large-scale, have been used to investigate the potential conditions leading to a high explosive violent reaction (HEVR) for pristine as well as aged materials. PBX 9501, one of the Los Alamos National Laboratory (LANL) HE formulations, is routinely evaluated for potential aging mechanisms that may influence performance and or safety criteria. Ultimately, the data derived from the aging analyses will be used to further advance 3-D finite element analysis predictive capability with improved bulk constitutive HE models for the assessment of HE response to mechanical insult. The Modified Steven test geometry was used to investigate the mechanical loading behavior and response of baseline and virtually-aged PBX 9501 lots. The PBX 9501 binder system is composed of nitroplasticized Estane 5703{trademark}, a polyester polyurethane copolymer. The nitroplasticizer (NP) can migrate out of the PBX 9501 as a function of time, resulting in increased brittle behavior and response. To mimic extreme NP depletion four lots of X-0557 were formulated with reduced NP concentrations for comparison to the baseline PBX 9501. Changes to the mechanical behavior response of the PBXs as a function of plasticizer loss may eventually affect the response of the HE to low amplitude impact. The threshold velocity to reaction, and energy release for the different lots are reported, compared and evaluated for trends as a function of NP weight percent.

  19. Modified aspirated internal combustion engine

    SciTech Connect

    Smith, J.E.

    1993-06-01

    An internal combustion engine is described, comprising: an engine block; at least one cylinder; at least one piston, each piston being reciprocally movable in the cylinder; a head connected with the engine block so as to form a combustion chamber above each piston; aspiration means for providing gas entry into and gas exit from the combustion chamber of each cylinder; valves for controlling gas entry and exit; ignition for initiating and timing combustion in each combustion chamber; a crankshaft rotatably mounted to the engine block, the crankshaft having at least one crank arm; connecting rod between each piston and the crank arm for translating reciprocation of each piston into rotation of each crankshaft; mounting means for rotatably mounting crankshaft to the engine block, the mounting means at each mounting location comprising: a crankshaft journal located on the crankshaft, the crankshaft journal having a crankshaft cross-section and an off-set portion, the off-set portion having a maximum which is equal to a predetermined off-set, the maximum off-set being located on a predetermined side of the crankshaft, the off-set portion smoothly decreasing from the maximum to a minimum from each side of the maximum, the minimum being equal to a zero off-set, the minimum off-set being located on the crankshaft opposite maximum off-set; and an engine block bearing connected with the engine block, wherein the crankshaft rotates in relation to the engine block about an eccentric centerline passing axially through the crankshaft journal cross-section, the eccentric centerline being displaced from a true centerline passing axially through said crankshaft cross-section by a distance equal to one-half the off-set, wherein the crank arm has a predetermined radial length centered on the eccentric centerline, and wherein the modified crankshaft has at least one output shaft portion axially aligned with the eccentric centerline.

  20. Computer Simulation of the Population Growth (Schizosaccharomyces Pombe) Experiment.

    ERIC Educational Resources Information Center

    Daley, Michael; Hillier, Douglas

    1981-01-01

    Describes a computer program (available from authors) developed to simulate "Growth of a Population (Yeast) Experiment." Students actively revise the counting techniques with realistically simulated haemocytometer or eye-piece grid and are reminded of the necessary dilution technique. Program can be modified to introduce such variables as…

  1. Solar Simulator Represents the Mars Surface Solar Environment

    NASA Technical Reports Server (NTRS)

    Stella, Paul M.; Dawson, Stephen F.; Mueller, Robert L.; Mardesich, Nick; Rapp, Donald

    2009-01-01

    A report discusses the development of a Mars surface, laboratory-based solar simulator to create solar cells that can function better on Mars. The Mars Optimized Solar cell Technology (MOST) required defining the surface incident spectrum, developing an appropriate laboratory solar simulator measurement capability, and developing and testing commercial cells modified for the Mars surface spectrum.

  2. Modified LaRC(TM)-IA Polyimides

    NASA Technical Reports Server (NTRS)

    St. Clair, Terry L.; Chang, Alice C.; Hou, Tan H.; Working, Dennis C.

    1994-01-01

    Modified versions of thermoplastic polyimide LaRC(TM)-IA incorporate various amounts of additional, rigid moieties into backbones of LaRC(TM)-IA molecules. Modified versions more resistant to solvents and exhibit higher glass-transition temperatures, yet retain melt-flow processability of unmodified LaRC(TM)-IA.

  3. Teaching the Extended Modifier: A Transformational Approach.

    ERIC Educational Resources Information Center

    Mann, G. Thomas

    1985-01-01

    Offers a practical model for teaching the extended modifier that is economical and linguistically sound, based on the insights and methodology of transformational generative grammar. Five transformational rules are given for generating extended modifiers from relative clauses. Examples of transformations and two class exercises in German are also…

  4. Effects of modified gravity in galactic clustering

    NASA Astrophysics Data System (ADS)

    Verma, Murli; Krishna Yadav, Bal

    2016-07-01

    We discuss the distinct effects of the modified gravity, especially f(R) gravity in structure formation. The small redshift as well as high redshift epochs are studied with a potential set of diagnostics distinguishing between the standard general relativistic and the modified gravity. These diagnostics are further put to test against the observations obtained in clustering surveys.

  5. Analysis of bit error rate for modified T-APPM under weak atmospheric turbulence channel

    NASA Astrophysics Data System (ADS)

    Liu, Zhe; Zhang, Qi; Wang, Yong-jun; Liu, Bo; Zhang, Li-jia; Wang, Kai-min; Xiao, Fei; Deng, Chao-gong

    2013-12-01

    T-APPM is combined of TCM (trellis-coded modulation) and APPM (Amplitude-Pulse-position modulation) and has broad application prospects in space optical communication. Set partitioning in standard T-APPM algorithm has the optimal performance in a multi-carrier system, but whether this method has the optimal performance in APPM which is a single-carrier system is unknown. To solve this problem, we first research the atmospheric channel model with weak turbulence; then a modified T-APPM algorithm was proposed, compared to the standard T-APPM algorithm, modified algorithm uses Gray code mapping instead of set partitioning mapping; finally, simulate the two algorithms with Monte-Carlo method. Simulation results showed that, when bit error rate at 10-4, the modified T-APPM algorithm achieved 0.4dB in SNR, effectively improve the system error performance.

  6. Teaching and Assessing Clinical Skills Using a Modified Essay Examination. Teaching Activity Poster.

    ERIC Educational Resources Information Center

    Brown, Stephen W.

    A "modified essay examination" was used to help teach and to assess clinical problem-solving skills with 11 first trimester doctoral students. This examination provided a paper-and-pencil simulation of problems encountered in case management. Students were required to generate hypotheses, formulate questions, discuss issues, and make management…

  7. A Modified Frequency Estimation Equating Method for the Common-Item Nonequivalent Groups Design

    ERIC Educational Resources Information Center

    Wang, Tianyou; Brennan, Robert L.

    2009-01-01

    Frequency estimation, also called poststratification, is an equating method used under the common-item nonequivalent groups design. A modified frequency estimation method is proposed here, based on altering one of the traditional assumptions in frequency estimation in order to correct for equating bias. A simulation study was carried out to…

  8. Development of a Headlight Glare Simulator for a Driving Simulator

    PubMed Central

    Hwang, Alex D.; Peli, Eli

    2012-01-01

    We describe the design and construction of a headlight glare simulator to be used with a driving simulator. The system combines a modified programmable off–the-shelf LED display board and a beamsplitter so that the LED lights, representing the headlights of oncoming cars, are superimposed over the driving simulator headlights image. Ideal spatial arrangement of optical components to avoid misalignments of the superimposed images is hard to achieve in practice and variations inevitably introduce some parallax. Furthermore, the driver’s viewing position varies with driver’s height and seating position preferences exacerbate such misalignment. We reduce the parallax errors using an intuitive calibration procedure (simple drag-and-drop alignment of nine LED positions with calibration dots on the screen). To simulate the dynamics of headlight brightness changes when two vehicles are approaching, LED intensity control algorithms based on both headlight and LED beam shapes were developed. The simulation errors were estimated and compared to real-world headlight brightness variability. PMID:24443633

  9. 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.

  10. Exposure simulation of electron beam microcolumn lithography

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Kon; Oh, Hye-Keun

    2004-05-01

    We propose an improved method to describe the electron-resist interaction based on Dill"s model for exposure simulation. For this purpose, Monte Carlo simulation was performed to obtain the energy intensity distribution in the chemically amplified resist. Tabulated Mott data for elastic scattering, Moller and Vriens cross sections for inelastic scattering, and Modified Bethe equation plus discrete energy loss for energy loss are used for the calculation of the energy intensity distribution. Through the electron-resist interaction, the energy intensity distribution changes resist components into the exposure production such as the photoacid concentration or the photoacid generator inside resists with various pattern shapes by using the modified Dill"s model. Our simulation profiles show a good agreement with experimental profiles.

  11. Genistein Modified Polymer Blends for Hemodialysis Membranes

    NASA Astrophysics Data System (ADS)

    Chang, Teng; Kyu, Thein; Define, Linda; Alexander, Thomas

    2012-02-01

    A soybean-derived phytochemical called genistein was used as a modifying agent to polyether sulfone/polyvinyl pyrrolidone (PES/PVP) blends to produce multi-functional hemodialysis membranes. With the aid of phase diagrams of PES/PVP/genistein blends, asymmetric porous membranes were fabricated by coagulating in non-solvent. Both unmodified and genistein modified PES/PVP membranes were shown to be non-cytotoxic to the blood cells. Unmodified PES/PVP membranes were found to reduce reactive oxygen species (ROS) levels, whereas the genistein modified membranes exhibited suppression for ˜60% of the ROS levels. Also, the genistein modified membranes revealed significant suppression of pro-inflammatory cytokines: IL-1β, IL-6, and TNF-α. Moreover, addition of PVP to PES showed the reduced trend of platelet adhesion and then leveled off. However, the modified membranes exhibited suppression of platelet adhesion at low genistein loading, but beyond 15 wt%, the platelet adhesion level rised up.

  12. Phosphonium modified clay/polyimide nanocomposites

    NASA Astrophysics Data System (ADS)

    Ceylan, Hatice; Çakmakçi, Emrah; Beyler-Çiǧil, Asli; Vezir Kahraman, Memet

    2014-08-01

    In this study, octyltriphenylphosphonium bromide [OTPP-Br] was prepared from the reaction of triphenylphosphine and 1 -bromooctane. The modification of clay was done by ion exchange reaction using OTPP-Br in water medium. Poly(amic acid) was prepared from the reaction of 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-Oxydianiline (ODA). Polyimide(PI)/clay hybrids were prepared by blending of poly(amic acid) and organically modified clay as a type of layered clays. The morphology of the Polyimide/ phosphonium modified clay hybrids was characterized by scanning electron microscopy (SEM). Chemical structures of polyimide and Polyimide/ phosphonium modified clay hybrids were characterized by FTIR. SEM and FTIR results showed that the Polyimide/ phosphonium modified clay hybrids were successfully prepared. Thermal properties of the Polyimide/ phosphonium modified clay hybrids were characterized by thermogravimetric analysis (TGA).

  13. Detection of Genetically Modified Food: Has Your Food Been Genetically Modified?

    ERIC Educational Resources Information Center

    Brandner, Diana L.

    2002-01-01

    Explains the benefits and risks of genetically-modified foods and describes methods for genetically modifying food. Presents a laboratory experiment using a polymerase chain reaction (PCR) test to detect foreign DNA in genetically-modified food. (Contains 18 references.) (YDS)

  14. Biomimetic synthesis of modified calcium phosphate fine powders and their in vitro studies

    SciTech Connect

    Gergulova, R. Tepavitcharova, S. Rabadjieva, D. Sezanova, K. Ilieva, R.; Alexandrova, R.; Andonova-Lilova, B.

    2013-12-16

    Biomimetic approach and subsequent high-temperature treatment were used to synthesize ion modified calcium phosphate fine powders. Thus, using Simulated Body Fluid (SBF) as an ion modifier, a bi-phase mixture of ion modified β-tricalcium phosphate and hydroxyapatite (β-TCP + HA) was prepared. The use of SBF electrolyte solution enriched with Mg{sup 2+} or Zn{sup 2+} yielded monophase β-tricalcium phosphate additionally modified with Mg{sup 2+} or Zn{sup 2+} (Mg-β-TCP or Zn-β-TCP). The in vitro behavior of the prepared powders on cell viability and proliferation of murine BALB/c 3T3 fibroblasts and of human Lep 3 cells was studied by MTT test assays and Mosmann method after 72 h incubation. The relative cell viability was calculated.

  15. Biomimetic synthesis of modified calcium phosphate fine powders and their in vitro studies

    NASA Astrophysics Data System (ADS)

    Gergulova, R.; Tepavitcharova, S.; Rabadjieva, D.; Sezanova, K.; Ilieva, R.; Alexandrova, R.; Andonova-Lilova, B.

    2013-12-01

    Biomimetic approach and subsequent high-temperature treatment were used to synthesize ion modified calcium phosphate fine powders. Thus, using Simulated Body Fluid (SBF) as an ion modifier, a bi-phase mixture of ion modified β-tricalcium phosphate and hydroxyapatite (β-TCP + HA) was prepared. The use of SBF electrolyte solution enriched with Mg2+ or Zn2+ yielded monophase β-tricalcium phosphate additionally modified with Mg2+ or Zn2+ (Mg-β-TCP or Zn-β-TCP). The in vitro behavior of the prepared powders on cell viability and proliferation of murine BALB/c 3T3 fibroblasts and of human Lep 3 cells was studied by MTT test assays and Mosmann method after 72 h incubation. The relative cell viability was calculated.

  16. A modified evaluation method to reduce finite pulse time effects in flash diffusivity measurement

    NASA Astrophysics Data System (ADS)

    Tao, Ye; Yang, Liping; Zhong, Qiu; Xu, Zijun; Luo, Caiyun

    2015-12-01

    A modified evaluation method for laser flash is proposed. In this method, the moment of laser-heating cutoff time is considered as zero point. The penetration depth and formula equation of the sample temperature distribution are obtained with the approximate analytical solution before time zero (during laser heating) for the physical model of a continuously heated half-infinite, well-distributed sample. The weighted-average and approximate-equation methods are then used to quantitatively determine the laser effect depth, which leads to the formulation of a modified evaluation method in flash thermal diffusivity measurement. Results of the simulation calculations and experiments confirm the correctness of the modified method, which remarkably increases flash method applications. The modified method is applicable only to cases in which δ(x) does not exceed the sample thickness ( √{ 12 α τ 0 } ≤ L ) during laser heating.

  17. Modified magnetic field distribution in relativistic magnetron with diffraction output for compact operation

    SciTech Connect

    Li Wei; Liu Yonggui

    2011-02-15

    A modified magnetic field distribution in relativistic magnetron with diffraction output (MDO) for compact operation is proposed in this paper. The principle of how the modified magnetic field confines electrons drifting out of the interaction space is analyzed. The results of the particle-in-cell (PIC) simulations of the MDO with the modified magnetic field distribution show that the output power of the MDO is improved, and the long cylindrical waveguide used for collecting the drifting electrons can be omitted. The latter measure allows the horn antenna of the MDO to produce more focused energy with better directivity in the far field than it does with the long cylindrical waveguide. The MDO with the modified magnetic field distribution promises to be the real most compact narrow band high power microwave source.

  18. Complexation thermodynamics of modified cyclodextrins: extended cavities and distorted structures.

    PubMed

    Schönbeck, Christian; Westh, Peter; Holm, René

    2014-08-28

    Inclusion complexes between two bile salts and a range of differently methylated β-cyclodextrins were studied in an attempt to rationalize the complexation thermodynamics of modified cyclodextrins. Calorimetric titrations at a range of temperatures provided precise values of the enthalpies (ΔH°), entropies (ΔS°), and heat capacities (ΔCp) of complexation, while molecular dynamics simulations assisted the interpretation of the obtained thermodynamic parameters. As previously observed for several types of modified cyclodextrins, the substituents at the rims of the cyclodextrin induced large changes in ΔH° and ΔS°, but due to enthalpy-entropy compensation the changes in Gibbs free energy, and the binding constant, were much smaller. For the methylated β-cyclodextrins, the substituent-induced increments in ΔH° and ΔS° were nonmonotonic with an initial strong increase in both ΔH° and ΔS° and then a strong decrease when the degree of substitution exceeded some threshold. Exactly the same trend was observed for ΔCp. The dehydration of nonpolar surface, as quantified by the simulations, can to a large extent explain the variation in the thermodynamic parameters. The methyl substituents form additional hydrophobic contacts with the bile salt, but at high degrees of methylation they also cause significant distortion of the otherwise circular cyclodextrin structure. These two opposing contributions to the dehydration are the major causes for the observed variations in the thermodynamic functions. The structural effects are not expected to be specific for methylated cyclodextrins but should be observed for most modified cyclodextrins. An even more general conclusion is that variations in the extent of hydration are an important underlying reason for the commonly observed phenomenon termed enthalpy-entropy compensation and also for the less frequent reports of entropy convergence around 110 °C.

  19. Voids in modified gravity reloaded: Eulerian void assignment

    NASA Astrophysics Data System (ADS)

    Lam, Tsz Yan; Clampitt, Joseph; Cai, Yan-Chuan; Li, Baojiu

    2015-07-01

    We revisit the excursion set approach to calculate void abundances in chameleon-type modified gravity theories, which was previously studied by Clampitt, Cai & Li. We focus on properly accounting for the void-in-cloud effect, i.e. the growth of those voids sitting in overdense regions may be restricted by the evolution of their surroundings. This effect may change the distribution function of voids hence affect predictions on the differences between modified gravity (MG) and general relativity (GR). We show that the thin-shell approximation usually used to calculate the fifth force is qualitatively good but quantitatively inaccurate. Therefore, it is necessary to numerically solve the fifth force in both overdense and underdense regions. We then generalize the Eulerian-void-assignment method of Paranjape, Lam & Sheth to our modified gravity model. We implement this method in our Monte Carlo simulations and compare its results with the original Lagrangian methods. We find that the abundances of small voids are significantly reduced in both MG and GR due to the restriction of environments. However, the change in void abundances for the range of void radii of interest for both models is similar. Therefore, the difference between models remains similar to the results from the Lagrangian method, especially if correlated steps of the random walks are used. As Clampitt et al., we find that the void abundance is much more sensitive to MG than halo abundances. Our method can then be a faster alternative to N-body simulations for studying the qualitative behaviour of a broad class of theories. We also discuss the limitations and other practical issues associated with its applications.

  20. Synthesis of molecular imprinted polymer modified TiO{sub 2} nanotube array electrode and their photoelectrocatalytic activity

    SciTech Connect

    Lu Na; Chen Shuo; Wang Hongtao; Quan Xie Zhao Huimin

    2008-10-15

    A tetracycline hydrochloride (TC) molecularly imprinted polymer (MIP) modified TiO{sub 2} nanotube array electrode was prepared via surface molecular imprinting. Its surface was structured with surface voids and the nanotubes were open at top end with an average diameter of approximately 50 nm. The MIP-modified TiO{sub 2} nanotube array with anatase phase was identified by XRD and a distinguishable red shift in the absorption spectrum was observed. The MIP-modified electrode also exhibited a high adsorption capacity for TC due to its high surface area providing imprinted sites. Photocurrent was generated on the MIP-modified photoanode using the simulated solar spectrum and increased with the increase of positive bias potential. Under simulated solar light irradiation, the MIP-modified TiO{sub 2} nanotube array electrode exhibited enhanced photoelectrocatalytic (PEC) activity with the apparent first-order rate constant being 1.2-fold of that with TiO{sub 2} nanotube array electrode. The effect of the thickness of the MIP layer on the PEC activity was also evaluated. - Graphical abstract: A tetracycline hydrochloride molecularly imprinted polymer modified TiO{sub 2} nanotube array electrode was prepared via surface molecular imprinting. It showed improved response to simulated solar light and higher adsorption capability for tetracycline hydrochloride, thereby exhibiting increased PEC activity under simulated solar light irradiation. The apparent first-order rate constant was 1.2-fold of that on TiO{sub 2} nanotube array electrode.

  1. Modified Fittings Enhance Industrial Safety

    NASA Technical Reports Server (NTRS)

    2012-01-01

    Kennedy Space Center is not only home to one of the largest buildings in the world - the massive Vehicle Assembly Building - it also hosts a number of one-of-a-kind facilities. The more than 30-mile-long campus has witnessed every launch from the Space Shuttle Launch Pad, as well as many homecomings at the Shuttle Landing Facility. Just as important, the Space Station Processing Facility (SSPF) has seen each element of the International Space Station (ISS) that passes through Kennedy before it goes into orbit. The SSPF is where ISS components are checked, tested, and adjusted before being packed into the Space Shuttle for transport. In an environment like the SSPF - spanning 457,000 square feet of processing areas, operational control rooms, laboratories, logistics areas, and office space - large workstands and equipment used to support the processing of ISS components need to be moved around the facility. One of the devices employed for this task is an air pallet. An air pallet moves on cushions of air instead of wheels. Compressed air inflates the cushions underneath the pallet and is then expelled through exhaust holes. This forms a thin film of air between the cushions and the floor, lifting the platform off the floor and making it easy to move the heavy workstands, equipment, and ISS components. Concerned with the safety of the connections on the pressurized air hoses used for the air pallets, engineers at Kennedy modified an existing commercial cam and groove fitting to control the air supply hose in the event of an accidental release of a pressurized hose. This modification prevented the hose from detaching and, propelled by compressed air, striking workers or equipment. "At the time, these were not available on commercial coupling halves, so NASA made a modification and then put them into use. If a worker were to accidentally try to remove a pressurized hose from the pallet, it no longer rapidly separated, and it safely relieved the pressure," says Paul

  2. Visual Interface for Materials Simulations

    2004-08-01

    VIMES (Visual Inteface for Materials Simulations) is a graphical user interface (GUI) for pre- and post-processing alomistic materials science calculations. The code includes tools for building and visualizing simple crystals, supercells, and surfaces, as well as tools for managing and modifying the input to Sandia materials simulations codes such as Quest (Peter Schultz, SNL 9235) and Towhee (Marcus Martin, SNL 9235). It is often useful to have a graphical interlace to construct input for materialsmore » simulations codes and to analyze the output of these programs. VIMES has been designed not only to build and visualize different materials systems, but also to allow several Sandia codes to be easier to use and analyze. Furthermore. VIMES has been designed to be reasonably easy to extend to new materials programs. We anticipate that users of Sandia materials simulations codes will use VIMCS to simplify the submission and analysis of these simulations. VIMES uses standard OpenGL graphics (as implemented in the Python programming language) to display the molecules. The algorithms used to rotate, zoom, and pan molecules are all standard applications using the OpenGL libraries. VIMES uses the Marching Cubes algorithm for isosurfacing 3D data such as molecular orbitals or electron densities around the molecules.« less

  3. Surfactants modify the release from tablets made of hydrophobically modified poly (acrylic acid).

    PubMed

    Knöös, Patrik; Onder, Sebla; Pedersen, Lina; Piculell, Lennart; Ulvenlund, Stefan; Wahlgren, Marie

    2013-01-01

    Many novel pharmaceutically active substances are characterized by a high hydrophobicity and a low water solubility, which present challenges for their delivery as drugs. Tablets made from cross-linked hydrophobically modified poly (acrylic acid) (CLHMPAA), commercially available as Pemulen™, have previously shown promising abilities to control the release of hydrophobic model substances. This study further investigates the possibility to use CLHMPAA in tablet formulations using ibuprofen as a model substance. Furthermore, surfactants were added to the dissolution medium in order to simulate the presence of bile salts in the intestine. The release of ibuprofen is strongly affected by the presence of surfactant and/or buffer in the dissolution medium, which affect both the behaviour of CLHMPAA and the swelling of the gel layer that surrounds the disintegrating tablets. Two mechanisms of tablet disintegration were observed under shear, namely conventional dissolution of a soluble tablet matrix and erosion of swollen insoluble gel particles from the tablet. The effects of surfactant in the surrounding medium can be circumvented by addition of surfactant to the tablet. With added surfactant, tablets that may be insusceptible to the differences in bile salt level between fasted or fed states have been produced, thus addressing a central problem in controlled delivery of hydrophobic drugs. In other words CLHMPAA is a potential candidate to be used in tablet formulations for controlled release with poorly soluble drugs.

  4. Hybrid Simulator

    2005-10-15

    HybSim (short for Hybrid Simulator) is a flexible, easy to use screening tool that allows the user to quanti the technical and economic benefits of installing a village hybrid generating system and simulates systems with any combination of —Diesel generator sets —Photovoltaic arrays -Wind Turbines and -Battery energy storage systems Most village systems (or small population sites such as villages, remote military bases, small communities, independent or isolated buildings or centers) depend on diesel generationmore » systems for their source of energy. HybSim allows the user to determine other "sources" of energy that can greatly reduce the dollar to kilo-watt hour ratio. Supported by the DOE, Energy Storage Program, HybSim was initially developed to help analyze the benefits of energy storage systems in Alaskan villages. Soon after its development, other sources of energy were added providing the user with a greater range of analysis opportunities and providing the village with potentially added savings. In addition to village systems, HybSim has generated interest for use from military institutions in energy provisions and USAID for international village analysis.« less

  5. A modified siphon sampler for shallow water

    USGS Publications Warehouse

    Diehl, Timothy H.

    2008-01-01

    A modified siphon sampler (or 'single-stage sampler') was developed to sample shallow water at closely spaced vertical intervals. The modified design uses horizontal rather than vertical sample bottles. Previous siphon samplers are limited to water about 20 centimeters (cm) or more in depth; the modified design can sample water 10 cm deep. Several mounting options were used to deploy the modified siphon sampler in shallow bedrock streams of Middle Tennessee, while minimizing alteration of the stream bed. Sampling characteristics and limitations of the modified design are similar to those of the original design. Testing showed that the modified sampler collects unbiased samples of suspended silt and clay. Similarity of the intake to the original siphon sampler suggests that the modified sampler would probably take downward-biased samples of suspended sand. Like other siphon samplers, it does not sample isokinetically, and the efficiency of sand sampling can be expected to change with flow velocity. The sampler needs to be located in the main flow of the stream, and is subject to damage from rapid flow and floating debris. Water traps were added to the air vents to detect the flow of water through the sampler, which can cause a strong upward bias in sampled suspended-sediment concentration. Water did flow through the sampler, in some cases even when the top of the air vent remained above water. Air vents need to be extended well above maximum water level to prevent flow through the sampler.

  6. A modified surgical procedure for concealed penis

    PubMed Central

    Cheng, Gong; Liu, Bianjiang; Guan, Zhaolong; Huang, Yuan; Qin, Chao; Song, Ninghong; Wang, Zengjun

    2015-01-01

    Introduction: We described a modified surgical procedure for repairing a concealed penis and compared the efficacy and feasibility of modified repair with traditional repair. Methods: From March 2003 to December 2012, 96 patients with a concealed penis were recruited to undergo penile repair at our centre. Modified repair and traditional repair were performed respectively on 46 and 50 cases. We compared operative time, intraoperative blood loss, cosmetic result of operative scars, postoperative penile retraction, and complications. Results: All operations were completed successfully without serious complications. The mean operative time, intraoperative blood loss, and cosmetic result of the operative scar between the two surgical methods were similar. However, the postoperative penile retraction rate in patients undergoing modified repair decreased significantly than in the traditional repair. Conclusions: Our modified surgical procedure is effective and feasible for a concealed penis. Although extra procedures were needed for the modified repair, the operative time, intraoperative blood loss and cosmetic result of operative scar between the two procedures were similar. Compared with traditional repair, modified repair has better clinical outcomes. PMID:26664507

  7. Nanoparticles modified with multiple organic acids

    NASA Technical Reports Server (NTRS)

    Cook, Ronald Lee (Inventor); Luebben, Silvia DeVito (Inventor); Myers, Andrew William (Inventor); Smith, Bryan Matthew (Inventor); Elliott, Brian John (Inventor); Kreutzer, Cory (Inventor); Wilson, Carolina (Inventor); Meiser, Manfred (Inventor)

    2007-01-01

    Surface-modified nanoparticles of boehmite, and methods for preparing the same. Aluminum oxyhydroxide nanoparticles are surface modified by reaction with selected amounts of organic acids. In particular, the nanoparticle surface is modified by reactions with two or more different carboxylic acids, at least one of which is an organic carboxylic acid. The product is a surface modified boehmite nanoparticle that has an inorganic aluminum oxyhydroxide core, or part aluminum oxyhydroxide core and a surface-bonded organic shell. Organic carboxylic acids of this invention contain at least one carboxylic acid group and one carbon-hydrogen bond. One embodiment of this invention provides boehmite nanoparticles that have been surface modified with two or more acids one of which additional carries at least one reactive functional group. Another embodiment of this invention provides boehmite nanoparticles that have been surface modified with multiple acids one of which has molecular weight or average molecular weight greater than or equal to 500 Daltons. Yet, another embodiment of this invention provides boehmite nanoparticles that are surface modified with two or more acids one of which is hydrophobic in nature and has solubility in water of less than 15 by weight. The products of the methods of this invention have specific useful properties when used in mixture with liquids, as filler in solids, or as stand-alone entities.

  8. Nanoparticles modified with multiple organic acids

    DOEpatents

    Cook, Ronald Lee; Luebben, Silvia DeVito; Myers, Andrew William; Smith, Bryan Matthew; Elliott, Brian John; Kreutzer, Cory; Wilson, Carolina; Meiser, Manfred

    2007-07-17

    Surface-modified nanoparticles of boehmite, and methods for preparing the same. Aluminum oxyhydroxide nanoparticles are surface modified by reaction with selected amounts of organic acids. In particular, the nanoparticle surface is modified by reactions with two or more different carboxylic acids, at least one of which is an organic carboxylic acid. The product is a surface modified boehmite nanoparticle that has an inorganic aluminum oxyhydroxide core, or part aluminum oxyhydroxide core and a surface-bonded organic shell. Organic carboxylic acids of this invention contain at least one carboxylic acid group and one carbon-hydrogen bond. One embodiment of this invention provides boehmite nanoparticles that have been surface modified with two or more acids one of which additional carries at least one reactive functional group. Another embodiment of this invention provides boehmite nanoparticles that have been surface modified with multiple acids one of which has molecular weight or average molecular weight greater than or equal to 500 Daltons. Yet, another embodiment of this invention provides boehmite nanoparticles that are surface modified with two or more acids one of which is hydrophobic in nature and has solubility in water of less than 15 by weight. The products of the methods of this invention have specific useful properties when used in mixture with liquids, as filler in solids, or as stand-alone entities.

  9. SCREAMm - modified code SCREAM to sumulate the acceleration of a pulsed beam through the superconducting linac

    SciTech Connect

    Eidelman, Yu.; Nagaitsev, S.; Solyak, N.; /Fermilab

    2011-07-01

    The code SCREAM - SuperConducting RElativistic particle Accelerator siMulation - was significantly modified and improved. Some misprints in the formulae used have been fixed and a more realistic expression for the vector-sum introduced. The realistic model of Lorentz-force detuning (LFD) is developed and will be implemented to the code. A friendly GUI allows various parameters of the simulated problem to be changed easily and quickly. Effective control of various output data is provided. A change of various parameters during the simulation process is controlled by plotting the corresponding graphs 'on the fly'. A large collection of various graphs can be used to illustrate the results.

  10. Dynamic simulation of a reverse Brayton refrigerator

    SciTech Connect

    Peng, N.; Xiong, L. Y.; Dong, B.; Liu, L. Q.; Lei, L. L.; Tang, J. C.

    2014-01-29

    A test refrigerator based on the modified Reverse Brayton cycle has been developed in the Chinese Academy of Sciences recently. To study the behaviors of this test refrigerator, a dynamic simulation has been carried out. The numerical model comprises the typical components of the test refrigerator: compressor, valves, heat exchangers, expander and heater. This simulator is based on the oriented-object approach and each component is represented by a set of differential and algebraic equations. The control system of the test refrigerator is also simulated, which can be used to optimize the control strategies. This paper describes all the models and shows the simulation results. Comparisons between simulation results and experimental data are also presented. Experimental validation on the test refrigerator gives satisfactory results.

  11. MHD simulation of the Bastille day event

    NASA Astrophysics Data System (ADS)

    Linker, Jon; Torok, Tibor; Downs, Cooper; Lionello, Roberto; Titov, Viacheslav; Caplan, Ronald M.; Mikić, Zoran; Riley, Pete

    2016-03-01

    We describe a time-dependent, thermodynamic, three-dimensional MHD simulation of the July 14, 2000 coronal mass ejection (CME) and flare. The simulation starts with a background corona developed using an MDI-derived magnetic map for the boundary condition. Flux ropes using the modified Titov-Demoulin (TDm) model are used to energize the pre-event active region, which is then destabilized by photospheric flows that cancel flux near the polarity inversion line. More than 1033 ergs are impulsively released in the simulated eruption, driving a CME at 1500 km/s, close to the observed speed of 1700km/s. The post-flare emission in the simulation is morphologically similar to the observed post-flare loops. The resulting flux rope that propagates to 1 AU is similar in character to the flux rope observed at 1 AU, but the simulated ICME center passes 15° north of Earth.

  12. Biologic response modifiers in pediatric cancer.

    PubMed

    Worth, L L; Jeha, S S; Kleinerman, E S

    2001-08-01

    Biologic response modifiers are becoming an important addition to surgery, chemotherapy, and radiotherapy in the management of cancer. As this field of research grows and expands, more biologic response modifiers will be incorporated into therapeutic regimens. By stimulating the immune system to eradicate minimal residual disease, these agents may improve the disease-free and long-term survival rates of patients with a variety of malignancies. The challenge is to incorporate biologic response modifiers into the treatment armamentarium in ways that will maximize their tumorigenicity.

  13. Ion exchanger from chemically modified banana leaves.

    PubMed

    El-Gendy, Ahmed A; Mohamed, Samar H; Abd-Elkader, Amal H

    2013-07-25

    Cation exchangers from chemically modified banana leaves have been prepared. Banana leaves were treated with different molarities of KMnO4 and cross linked with epichlorohydrin and their effect on metal ion adsorption was investigated. Phosphorylation of chemically modified banana leaves was also studied. The metal ion uptake by these modified banana leaves was clarified. Effect of different varieties, e.g. activation of produced cation exchanger, concentration of metal ions was also investigated. Characterization of the prepared ion exchangers by using infrared and thermal analysis was also taken in consideration. PMID:23768590

  14. Chemically modified graphite for electrochemical cells

    DOEpatents

    Greinke, Ronald Alfred; Lewis, Irwin Charles

    1998-01-01

    This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (i) the electrode, (ii) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (iii) a counterelectrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes.

  15. Chemically modified graphite for electrochemical cells

    DOEpatents

    Greinke, R.A.; Lewis, I.C.

    1998-05-26

    This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (1) the electrode, (2) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (3) a counter electrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes. 3 figs.

  16. Characterization of Polyethylene Glycol Modified Hemoglobins

    NASA Astrophysics Data System (ADS)

    Salazar, Gil; Barr, James; Morgan, Wayne; Ma, Li

    2011-03-01

    Polyethylene glycol modified hemoglobins (PEGHbs) was characterized by liquid chromatography and fluorescence methods. We prepared four samples of two different molecular weight PEG, 5KDa and 20KDa, modified bovine and human hemoglobin. We studied the oxygen affinities, stabilities, and peroxidase activities of PEGHbs. We have related oxygen affinities with different degrees of modifications. The data showed that the modification on the beta subunits was less stable than that of the alpha subunits on the human Hb based samples especially. We also compared peroxidase activities among different modified PEGHbs.

  17. A modified thermal conductivity for low density plasma magnetic flux tubes

    NASA Technical Reports Server (NTRS)

    Comfort, R. H.; Craven, P. D.; Richards, P. G.

    1995-01-01

    In response to inconsistencies which have arisen in results from a hydrodynamic model in simulation of high ion temperature (1-2 eV) observed in low density, outer plasmasphere flux tubes, we postulate a reduced thermal conductivity coefficient in which only particles in the loss cone of the quasi-collisionless plasma contribute to the thermal conduction. Other particles are assumed to magnetically mirror before they reach the topside ionosphere and therefore not to remove thermal energy from the plasmasphere. This concept is used to formulate a mathematically simple, but physically limiting model for a modified thermal conductivity coefficient. When this modified coefficient is employed in the hydrodynamic model in a case study, the inconsistencies between simulation results and observations are largely resolved. The high simulated ion temperatures are achieved with significantly lower ion temperatures in the topside ionosphere. We suggest that this mechanism may be operative under the limited low density, refilling conditions in which high ion temperatures are observed.

  18. Modelling and design of modified Wollaston prisms and the application in differential interference contrast microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Site; Zhong, Huiying; Wyrowski, Frank

    2016-03-01

    Wollaston prisms and the modified Wollaston prisms, which are interesting for various applications like optical metrology, topography of surfaces and biological imaging, has been theoretically studied and also been practically applied. The previous studies are mostly based on ray tracing analysis and, as a result, the information that can be obtained are somehow restricted. In this paper, we propose a geometric field tracing technique for the simulation of light propagation through Wollaston prisms. In geometric field tracing we seek for the solutions to Maxwell's equations under the geometrical optics approximation, so that all the properties of light as electromagnetic field are retained. Using the proposed simulation technique, we present the simulation of a differential interference contrast (DIC) microscopy, in which the modified Wollaston prism is used as the key component.

  19. Lineshape theory of pigment-protein complexes: How the finite relaxation time of nuclei influences the exciton relaxation-induced lifetime broadening.

    PubMed

    Dinh, Thanh-Chung; Renger, Thomas

    2016-07-21

    In pigment-protein complexes, often the excited states are partially delocalized and the exciton-vibrational coupling in the basis of delocalized states contains large diagonal and small off-diagonal elements. This inequality may be used to introduce potential energy surfaces (PESs) of exciton states and to treat the inter-PES coupling in Markov and secular approximations. The resulting lineshape function consists of a Lorentzian peak that is broadened by the finite lifetime of the exciton states caused by the inter-PES coupling and a vibrational sideband that results from the mutual displacement of the excitonic PESs with respect to that of the ground state. So far analytical expressions have been derived that relate the exciton relaxation-induced lifetime broadening to the Redfield [T. Renger and R. A. Marcus, J. Chem. Phys. 116, 9997 (2002)] or modified Redfield [M. Schröder, U. Kleinekathöfer, and M. Schreiber, J. Chem. Phys. 124, 084903 (2006)] rate constants of exciton relaxation, assuming that intra-PES nuclear relaxation is fast compared to inter-PES transfer. Here, we go beyond this approximation and provide an analytical expression, termed Non-equilibrium Modified Redfield (NeMoR) theory, for the lifetime broadening that takes into account the finite nuclear relaxation time. In an application of the theory to molecular dimers, we find that, for a widely used experimental spectral density of the exciton-vibrational coupling of pigment-protein complexes, the NeMoR spectrum at low-temperatures (T < 150 K) is better approximated by Redfield than by modified Redfield theory. At room temperature, the lifetime broadening obtained with Redfield theory underestimates the NeMoR broadening, whereas modified Redfield theory overestimates it by a similar amount. A fortuitous error compensation in Redfield theory is found to explain the good performance of this theory at low temperatures. Since steady state spectra of PPCs are often measured at low temperatures

  20. Lineshape theory of pigment-protein complexes: How the finite relaxation time of nuclei influences the exciton relaxation-induced lifetime broadening

    NASA Astrophysics Data System (ADS)

    Dinh, Thanh-Chung; Renger, Thomas

    2016-07-01

    In pigment-protein complexes, often the excited states are partially delocalized and the exciton-vibrational coupling in the basis of delocalized states contains large diagonal and small off-diagonal elements. This inequality may be used to introduce potential energy surfaces (PESs) of exciton states and to treat the inter-PES coupling in Markov and secular approximations. The resulting lineshape function consists of a Lorentzian peak that is broadened by the finite lifetime of the exciton states caused by the inter-PES coupling and a vibrational sideband that results from the mutual displacement of the excitonic PESs with respect to that of the ground state. So far analytical expressions have been derived that relate the exciton relaxation-induced lifetime broadening to the Redfield [T. Renger and R. A. Marcus, J. Chem. Phys. 116, 9997 (2002)] or modified Redfield [M. Schröder, U. Kleinekathöfer, and M. Schreiber, J. Chem. Phys. 124, 084903 (2006)] rate constants of exciton relaxation, assuming that intra-PES nuclear relaxation is fast compared to inter-PES transfer. Here, we go beyond this approximation and provide an analytical expression, termed Non-equilibrium Modified Redfield (NeMoR) theory, for the lifetime broadening that takes into account the finite nuclear relaxation time. In an application of the theory to molecular dimers, we find that, for a widely used experimental spectral density of the exciton-vibrational coupling of pigment-protein complexes, the NeMoR spectrum at low-temperatures (T < 150 K) is better approximated by Redfield than by modified Redfield theory. At room temperature, the lifetime broadening obtained with Redfield theory underestimates the NeMoR broadening, whereas modified Redfield theory overestimates it by a similar amount. A fortuitous error compensation in Redfield theory is found to explain the good performance of this theory at low temperatures. Since steady state spectra of PPCs are often measured at low temperatures

  1. Lineshape theory of pigment-protein complexes: How the finite relaxation time of nuclei influences the exciton relaxation-induced lifetime broadening.

    PubMed

    Dinh, Thanh-Chung; Renger, Thomas

    2016-07-21

    In pigment-protein complexes, often the excited states are partially delocalized and the exciton-vibrational coupling in the basis of delocalized states contains large diagonal and small off-diagonal elements. This inequality may be used to introduce potential energy surfaces (PESs) of exciton states and to treat the inter-PES coupling in Markov and secular approximations. The resulting lineshape function consists of a Lorentzian peak that is broadened by the finite lifetime of the exciton states caused by the inter-PES coupling and a vibrational sideband that results from the mutual displacement of the excitonic PESs with respect to that of the ground state. So far analytical expressions have been derived that relate the exciton relaxation-induced lifetime broadening to the Redfield [T. Renger and R. A. Marcus, J. Chem. Phys. 116, 9997 (2002)] or modified Redfield [M. Schröder, U. Kleinekathöfer, and M. Schreiber, J. Chem. Phys. 124, 084903 (2006)] rate constants of exciton relaxation, assuming that intra-PES nuclear relaxation is fast compared to inter-PES transfer. Here, we go beyond this approximation and provide an analytical expression, termed Non-equilibrium Modified Redfield (NeMoR) theory, for the lifetime broadening that takes into account the finite nuclear relaxation time. In an application of the theory to molecular dimers, we find that, for a widely used experimental spectral density of the exciton-vibrational coupling of pigment-protein complexes, the NeMoR spectrum at low-temperatures (T < 150 K) is better approximated by Redfield than by modified Redfield theory. At room temperature, the lifetime broadening obtained with Redfield theory underestimates the NeMoR broadening, whereas modified Redfield theory overestimates it by a similar amount. A fortuitous error compensation in Redfield theory is found to explain the good performance of this theory at low temperatures. Since steady state spectra of PPCs are often measured at low temperatures

  2. Compatibilizer for crumb rubber modified asphalt

    SciTech Connect

    Labib, M.E.; Memon, G.M.; Chollar, B.H.

    1996-12-31

    The United States of America discards more than 300 million tires each year, and out of that a large fraction of the tires is dumped into stock piles. This large quantity of tires creates an environmental problem. The use of scrap tires is limited. There is a usage potential in such fields as fuel for combustion and Crumb Rubber-Modified Asphalt binder (CRMA). The use of crumb rubber in modifying asphalt is not a new technique; it is been used since early 1960 by pavement engineers. Crumb rubber is a composite of different blends of natural and synthetic rubber (natural rubber, processing oils, polybutadiene, polystyrene butadiene, and filler). Prior research had concluded that the performance of crumb rubber modified asphalt is asphalt dependent. In some cases it improves the Theological properties and in some cases it degrades the properties of modified asphalt.

  3. Observational bounds on modified gravity models

    SciTech Connect

    De Felice, Antonio; Mukherjee, Pia; Wang Yun

    2008-01-15

    Modified gravity provides a possible explanation for the currently observed cosmic acceleration. In this paper, we study general classes of modified gravity models. The Einstein-Hilbert action is modified by using general functions of the Ricci and the Gauss-Bonnet scalars, both in the metric and in the Palatini formalisms. We do not use an explicit form for the functions, but a general form with a valid Taylor expansion up to second order about redshift zero in the Riemann-scalars. The coefficients of this expansion are then reconstructed via the cosmic expansion history measured using current cosmological observations. These are the quantities of interest for theoretical considerations relating to ghosts and instabilities. We find that current data provide interesting constraints on the coefficients. The next-generation dark energy surveys should shrink the allowed parameter space for modified gravity models quite dramatically.

  4. A flame-resistant modified polystyrene

    NASA Technical Reports Server (NTRS)

    Karle, D. W.; Kratze, R. H.; Pacioren, K. L.

    1975-01-01

    Several modified polystyrenes have been developed that are self-extinguishing in air. Information is included in report that also describes molding and fabrication properties, toxicology, and thermal behavior of the polymers.

  5. Active containment systems incorporating modified pillared clays

    SciTech Connect

    Lundie, P. |; McLeod, N.

    1997-12-31

    The application of treatment technologies in active containment systems provides a more advanced and effective method for the remediation of contaminated sites. These treatment technologies can be applied in permeable reactive walls and/or funnel and gate systems. The application of modified pillared clays in active containment systems provides a mechanism for producing permeable reactive walls with versatile properties. These pillared clays are suitably modified to incorporate reactive intercalatants capable of reacting with both a broad range of organic pollutants of varying molecular size, polarity and reactivity. Heavy metals can be removed from contaminated water by conventional ion-exchange and other reactive processes within the clay structure. Complex contamination problems can be addressed by the application of more than one modified clay on a site specific basis. This paper briefly describes the active containment system and the structure/chemistry of the modified pillared clay technology, illustrating potential applications of the in-situ treatment process for contaminated site remediation.

  6. 21 CFR 184.1287 - Enzyme-modified fats.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Enzyme-modified fats. 184.1287 Section 184.1287... Listing of Specific Substances Affirmed as GRAS § 184.1287 Enzyme-modified fats. (a) Enzyme-modified refined beef fat, enzyme-modified butterfat, and enzyme-modified steam-rendered chicken fat are...

  7. 21 CFR 184.1287 - Enzyme-modified fats.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Enzyme-modified fats. 184.1287 Section 184.1287... Listing of Specific Substances Affirmed as GRAS § 184.1287 Enzyme-modified fats. (a) Enzyme-modified refined beef fat, enzyme-modified butterfat, and enzyme-modified steam-rendered chicken fat are...

  8. 21 CFR 184.1287 - Enzyme-modified fats.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Enzyme-modified fats. 184.1287 Section 184.1287... GRAS § 184.1287 Enzyme-modified fats. (a) Enzyme-modified refined beef fat, enzyme-modified butterfat, and enzyme-modified steam-rendered chicken fat are prepared from refined beef fat; butterfat...

  9. 21 CFR 184.1287 - Enzyme-modified fats.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Enzyme-modified fats. 184.1287 Section 184.1287... Listing of Specific Substances Affirmed as GRAS § 184.1287 Enzyme-modified fats. (a) Enzyme-modified refined beef fat, enzyme-modified butterfat, and enzyme-modified steam-rendered chicken fat are...

  10. 21 CFR 184.1287 - Enzyme-modified fats.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Enzyme-modified fats. 184.1287 Section 184.1287... Listing of Specific Substances Affirmed as GRAS § 184.1287 Enzyme-modified fats. (a) Enzyme-modified refined beef fat, enzyme-modified butterfat, and enzyme-modified steam-rendered chicken fat are...

  11. Implementation of interconnect simulation tools in spice

    NASA Technical Reports Server (NTRS)

    Satsangi, H.; Schutt-Aine, J. E.

    1993-01-01

    Accurate computer simulation of high speed digital computer circuits and communication circuits requires a multimode approach to simulate both the devices and the interconnects between devices. Classical circuit analysis algorithms (lumped parameter) are needed for circuit devices and the network formed by the interconnected devices. The interconnects, however, have to be modeled as transmission lines which incorporate electromagnetic field analysis. An approach to writing a multimode simulator is to take an existing software package which performs either lumped parameter analysis or field analysis and add the missing type of analysis routines to the package. In this work a traditionally lumped parameter simulator, SPICE, is modified so that it will perform lossy transmission line analysis using a different model approach. Modifying SPICE3E2 or any other large software package is not a trivial task. An understanding of the programming conventions used, simulation software, and simulation algorithms is required. This thesis was written to clarify the procedure for installing a device into SPICE3E2. The installation of three devices is documented and the installations of the first two provide a foundation for installation of the lossy line which is the third device. The details of discussions are specific to SPICE, but the concepts will be helpful when performing installations into other circuit analysis packages.

  12. Design of Novel Visible Light Active Photocatalyst Materials: Surface Modified TiO2.

    PubMed

    Nolan, Michael; Iwaszuk, Anna; Lucid, Aoife K; Carey, John J; Fronzi, Marco

    2016-07-01

    Work on the design of new TiO2 based photocatalysts is described. The key concept is the formation of composite structures through the modification of anatase and rutile TiO2 with molecular-sized nanoclusters of metal oxides. Density functional theory (DFT) level simulations are compared with experimental work synthesizing and characterizing surface modified TiO2 . DFT calculations are used to show that nanoclusters of metal oxides such as TiO2 , SnO/SnO2 , PbO/PbO2 , ZnO and CuO are stable when adsorbed at rutile and anatase surfaces, and can lead to a significant red shift in the absorption edge which will induce visible light absorption; this is the first requirement for a useful photocatalyst. The origin of the red shift and the fate of excited electrons and holes are determined. For p-block metal oxides the oxidation state of Sn and Pb can be used to modify the magnitude of the red shift and its mechanism. Comparisons of recent experimental studies of surface modified TiO2 that validate our DFT simulations are described. These nanocluster-modified TiO2 structures form the basis of a new class of photocatalysts which will be useful in oxidation reactions and with a correct choice of nanocluster modified can be applied to other reactions. PMID:26833714

  13. The modified atkins diet in refractory epilepsy.

    PubMed

    Sharma, Suvasini; Jain, Puneet

    2014-01-01

    The modified Atkins diet is a less restrictive variation of the ketogenic diet. This diet is started on an outpatient basis without a fast, allows unlimited protein and fat, and does not restrict calories or fluids. Recent studies have shown good efficacy and tolerability of this diet in refractory epilepsy. In this review, we discuss the use of the modified Atkins diet in refractory epilepsy.

  14. Modified locking thread form for fastener

    NASA Technical Reports Server (NTRS)

    Roopnarine, (Inventor); Vranish, John D. (Inventor)

    1998-01-01

    A threaded fastener has a standard part with a standard thread form characterized by thread walls with a standard included angle, and a modified part complementary to the standard part having a modified thread form characterized by thread walls which are symmetrically inclined with a modified included angle that is different from the standard included angle of the standard part's thread walls, such that the threads of one part make pre-loaded edge contact with the thread walls of the other part. The thread form of the modified part can have an included angle that is greater, less, or compound as compared to the included angle of the standard part. The standard part may be a bolt and the modified part a nut, or vice versa. The modified thread form holds securely even under large vibrational forces, it permits bi-directional use of standard mating threads, is impervious to the build up of tolerances and can be manufactured with a wider range of tolerances without loss of functionality, and distributes loading stresses (per thread) in a manner that decreases the possibility of single thread failure.

  15. Update on gene modifiers in cystic fibrosis

    PubMed Central

    Collaco, Joseph M.; Cutting, Garry R.

    2009-01-01

    Purpose of review Cystic fibrosis (CF) is a common, life-limiting monogenic disease, which typically manifests as progressive bronchiectasis, exocrine pancreatic dysfunction, and recurrent sinopulmonary infections. Although the gene responsible for CF (CFTR) was described in 1989, it has become increasingly evident that modifier genes and environmental factors play substantial roles in determining the severity of disease, particularly lung disease. Identifying these factors is crucial in devising therapies and other interventions to decrease the morbidity and mortality associated with this disorder. Recent findings Although many genes have been proposed as potential modifiers of CF, only a handful have withstood the test of replication. Several of the replicated findings reveal that genes affecting inflammation and infection response play a key role in modifying CF lung disease severity. Interactions between CFTR genotype, modifier genes, and environmental factors have been documented to influence lung function measures and infection status in CF patients. Summary Several genes have been demonstrated to affect disease severity in CF. Furthermore, it is likely that gene–gene and gene–environment interactions can explain a substantial portion of the variation of lung disease. Ongoing genome-wide studies are likely to identify novel genetic modifiers. Continued exploration of the role of genetic and nongenetic modifiers of CF is likely to yield new options for combating this debilitating disease. PMID:18812833

  16. Thrust calculation of electric solar wind sail by particle-in-cell simulation

    NASA Astrophysics Data System (ADS)

    Hoshi, Kento; Kojima, Hirotsugu; Muranaka, Takanobu; Yamakawa, Hiroshi

    2016-09-01

    In this study, thrust characteristics of an electric solar wind sail were numerically evaluated using full three-dimensional particle-in-cell (PIC) simulation. The thrust obtained from the PIC simulation was lower than the thrust estimations obtained in previous studies. The PIC simulation indicated that ambient electrons strongly shield the electrostatic potential of the tether of the sail, and the strong shield effect causes a greater thrust reduction than has been obtained in previous studies. Additionally, previous expressions of the thrust estimation were modified by using the shielded potential structure derived from the present simulation results. The modified thrust estimation agreed very well with the thrust obtained from the PIC simulation.

  17. Introduction to Quantum Simulation

    NASA Technical Reports Server (NTRS)

    Williams, Colin P.

    2005-01-01

    This viewgraph presentation addresses the problem of efficiently simulating the evolution of a quantum system. The contents include: 1) Quantum Simulation; 2) Extracting Answers from Quantum Simulations; 3) Quantum Fourier Transform; 4) Eigenvalue Estimation; 5) Fermionic Simulations.

  18. Expansion of flight simulator capability for study and solution of aircraft directional control problems on runways

    NASA Technical Reports Server (NTRS)

    Kibbee, G. W.

    1978-01-01

    The development, evaluation, and evaluation results of a DC-9-10 runway directional control simulator are described. An existing wide bodied flight simulator was modified to this aircraft configuration. The simulator was structured to use either two of antiskid simulations; (1) an analog mechanization that used aircraft hardware; or (2) a digital software simulation. After the simulation was developed it was evaluated by 14 pilots who made 818 simulated flights. These evaluations involved landings, rejected takeoffs, and various ground maneuvers. Qualitatively most pilots evaluated the simulator as realistic with good potential especially for pilot training for adverse runway conditions.

  19. Predicting Run Distances for a Modified Wedge Test

    NASA Astrophysics Data System (ADS)

    Dorgan, Robert J.; Lee, Richard; Sutherland, Gerrit

    2012-03-01

    Simulations were used to aid in the development of a modified wedge test (MWT). This explosive sensitivity experiment allows the shockwave curvature to be defined in order to investigate the effect of combined shock-shear loading on sensitivity. Various widths of PBXN-110 donor slabs were used to define the shockwave curvature introduced to wedge samples of the same explosive. The donor slabs were initiated with a linewave generator and a Detasheet booster, and the shock wave was attenuated using a slab of PMMA. In developing simulations for these three material experiments, calibrations of the PBXN-110 ignition and growth model and of the PMMA constitutive model were investigated in order to choose between several models found in the literature. A calibration shot from the MWT was also used to demonstrate the appropriateness of the models selected. Experimental results were compared to CTH calculations to indicate if there were effects associated with highly curved shock fronts that could not be adequately predicted. The run distances predicted in CTH for the thicker donor slab compare very favorably with the actual experiments; however, for thinner donor slabs, the actual experimental results seem to suggest a more sensitive behavior than the simulations are able to capture.

  20. Predicting Run Distances for a Modified Wedge Test

    NASA Astrophysics Data System (ADS)

    Dorgan, Robert; Lee, Richard; Sutherland, Gerrit

    2011-06-01

    Simulations were used to aid in the development of a modified wedge test (MWT). This explosive sensitivity experiment allows the shockwave curvature to be defined in order to investigate the effect of combined shock-shear loading on sensitivity. Various widths of PBXN-110 donor slabs were used to define the shockwave curvature introduced to wedge samples of the same explosive. The donor slabs were initiated with a linewave generator and a Detasheet booster, and the shock wave was attenuated using a slab of PMMA. In developing simulations for these three material experiments, calibrations of the PBXN-110 ignition and growth model and of the PMMA constitutive model were investigated in order to choose between several models found in the literature. A calibration shot from the MWT was also used to demonstrate the appropriateness of the models selected. Experimental results were compared to CTH calculations to indicate if there were effects associated with highly curved shock fronts that could not be adequately predicted. The run distances predicted in CTH for the thicker donor slab compare very favorably with the actual experiments; however, for thinner donor slabs, the actual experimental results seem to suggest a more sensitive behavior than the simulations are able to capture. DISTRIBUTION A. Approved for public release, distribution unlimited. (96ABW-2011-0053)

  1. A modified Monte Carlo 'local importance function transform' method

    SciTech Connect

    Keady, K. P.; Larsen, E. W.

    2013-07-01

    The Local Importance Function Transform (LIFT) method uses an approximation of the contribution transport problem to bias a forward Monte-Carlo (MC) source-detector simulation [1-3]. Local (cell-based) biasing parameters are calculated from an inexpensive deterministic adjoint solution and used to modify the physics of the forward transport simulation. In this research, we have developed a new expression for the LIFT biasing parameter, which depends on a cell-average adjoint current to scalar flux (J{sup *}/{phi}{sup *}) ratio. This biasing parameter differs significantly from the original expression, which uses adjoint cell-edge scalar fluxes to construct a finite difference estimate of the flux derivative; the resulting biasing parameters exhibit spikes in magnitude at material discontinuities, causing the original LIFT method to lose efficiency in problems with high spatial heterogeneity. The new J{sup *}/{phi}{sup *} expression, while more expensive to obtain, generates biasing parameters that vary smoothly across the spatial domain. The result is an improvement in simulation efficiency. A representative test problem has been developed and analyzed to demonstrate the advantage of the updated biasing parameter expression with regards to solution figure of merit (FOM). For reference, the two variants of the LIFT method are compared to a similar variance reduction method developed by Depinay [4, 5], as well as MC with deterministic adjoint weight windows (WW). (authors)

  2. An intermediate-complexity model for simulating marine biogeochemistry in deep time: Validation against the modern global ocean

    NASA Astrophysics Data System (ADS)

    Romaniello, Stephen J.; Derry, Louis A.

    2010-08-01

    We present a new high-resolution 1-D intermediate-complexity box model (ICBM) of ocean biogeochemical processes for paleoceanographic applications. The model contains 79 reservoirs in three regions that should be generally applicable throughout much of Earth history: (1) a stratified gyre region, (2) a high-latitude convective region, and (3) an upwelling region analogous to those found associated with eastern boundary currents. Transport processes are modeled as exchange fluxes between boxes and by eddy diffusion terms. Significant improvement in the representation of middepth oxygen budgets was achieved by implementing nonlocal mixing between the high-latitude surface and gyre thermocline reservoirs. The biogeochemical submodel simulates coupled C, N, P, O, and S systematics with explicit representation of microbial populations, using a process-based approach. Primary production follows Redfield stoichiometry, while water column remineralization is depth- and redox couple-dependent. Settling particulate organic matter is incorporated into a benthic submodel that accounts for burial and remineralization. The C/P ratio of burial depends on bottom water oxygen. Denitrification takes place both by classical and anammox pathways. The ICBM was tested against modern oceanographic observations from the Global Ocean Data Analysis Project, Joint Global Ocean Flux Study, and other databases. Comparisons of model output with circulation tracers including θ, salinity, CFC-12, and radiocarbon permit a test of the physical exchange scheme. Vertical profiles of biogeochemically reactive components in each of the three regions are in good agreement with observations. Under modern conditions the upwelling zone displays a pronounced oxygen minimum zone and water column denitrification, while these are not present in the high-latitude or gyre regions. Model-generated global fluxes also compare well to independent estimates of primary production, burial, and phosphorous and nitrogen

  3. Quantification in MALDI-TOF mass spectrometry of modified polymers.

    PubMed

    Walterová, Zuzana; Horský, Jiří

    2011-05-01

    MALDI-TOF mass spectrometry quantification is hampered by the poor reproducibility of the signal intensity and by molecular-mass and compositional discrimination. The addition of a suitable compound as an internal standard increases reproducibility and allows a calibration curve to be constructed. The concept was also verified with synthetic polymers but no instructions for practical implementation were given [H. Chen, M. He, J. Pei, H. He, Anal. Chem. 75 (2003) 6531-6535.], even though synthetic polymers are generally non-uniform with respect to molecular mass and composition and access to the polymer of the same molecular mass distribution and composition as that of the quantified one is thus the exception rather than rule. On the other hand, relative quantification of polymers e.g., the content of the precursor polymer in a batch of a modified polymer, is usually sought. In this particular case, the pure precursor is usually available and the modified polymer can serve as an internal standard. However, the calibration curve still cannot be constructed and the use of the internal standard has to be combined with the method of standard addition in which the precursor polymer is added directly to the analyzed sample. The experiments with simulated modified polymers, mixtures of poly(ethylene glycol) (PEG) and poly(ethylene glycol) monomethyl ether (MPEG) of similar molecular-mass distribution, revealed a power dependence of the PEG/MPEG signal-intensity ratio (MS ratio) on the PEG/MPEG concentrations ratio in the mixture (gravimetric ratio). The result was obtained using standard procedures and instrumentation, which means that the basic assumption of the standard-addition method, i.e., the proportionality of the MS and gravimetric ratios, generally cannot be taken for granted. Therefore, the multi-point combined internal-standard standard-addition method was developed and experimentally verified for the quantification of the precursor in modified polymers. In this

  4. Simulation of Tropical Biomass Burning

    NASA Technical Reports Server (NTRS)

    Hamill, Patrick; Guo, Zitian

    1998-01-01

    The work proposed was carried out as planned. The work described in this final report formed the basis for a follow-on research grant research grant from NASA Ames Research Center. The research objectives that were achieved during the course of our studies include the following: (1) the evaluation of several components of MM5 (Meteorological Model 5 version 2) and the Global/Regional Atmospheric Chemistry Event Simulator (GRACES) combined modeling system; (2) improved calculations of the transport of tracers for both NASA airborne missions, Study of Ozone and Nitrogen oxides experiment (SONEX) and Pacific Exploratory MIssion in the Tropics (PEM-Tropics); (3) improved source strength estimates for isoprene, dust and similar emissions from the Earth's surface. This required the use of newly available databases on the Earth's surface and vegetation; (4) completed atmospheric chemistry simulations of radicals and nitrogen oxide species; (5)improved the handling of cumulonimbus convection by modifying the existing scheme; (6) identified the role of the African Intertropical Front, using MM5's nesting capability to refine model resolution in crucial areas; modified the MM5 trajectory program to allow it to work much better for a parcel crossing the west/east boundaries.

  5. Simulator sickness during driving simulation studies.

    PubMed

    Brooks, Johnell O; Goodenough, Richard R; Crisler, Matthew C; Klein, Nathan D; Alley, Rebecca L; Koon, Beatrice L; Logan, William C; Ogle, Jennifer H; Tyrrell, Richard A; Wills, Rebekkah F

    2010-05-01

    While driving simulators are a valuable tool for assessing multiple dimensions of driving performance under relatively safe conditions, researchers and practitioners must be prepared for participants that suffer from simulator sickness. This paper describes multiple theories of motion sickness and presents a method for assessing and reacting to simulator sickness symptoms. Results showed that this method identified individuals who were unable to complete a driving simulator study due to simulator sickness with greater than 90% accuracy and that older participants had a greater likelihood of simulator sickness than younger participants. Possible explanations for increased symptoms experienced by older participants are discussed as well as implications for research ethics and simulator sickness prevention.

  6. Simulated Breeding

    NASA Astrophysics Data System (ADS)

    Unemi, Tatsuo

    This chapter describes a basic framework of simulated breeding, a type of interactive evolutionary computing to breed artifacts, whose origin is Blind Watchmaker by Dawkins. These methods make it easy for humans to design a complex object adapted to his/her subjective criteria, just similarly to agricultural products we have been developing over thousands of years. Starting from randomly initialized genome, the solution candidates are improved through several generations with artificial selection. The graphical user interface helps the process of breeding with techniques of multifield user interface and partial breeding. The former improves the diversity of individuals that prevents being trapped at local optimum. The latter makes it possible for the user to fix features he/she already satisfied. These methods were examined through artistic applications by the author: SBART for graphics art and SBEAT for music. Combining with a direct genome editor and exportation to another graphical or musical tool on the computer, they can be powerful tools for artistic creation. These systems may contribute to the creation of a type of new culture.

  7. Summary report on geochemical barrier special study. [Geochemically modify tailings to immobilize contaminants with modifiers such as peat, limestone, and hydrated lime

    SciTech Connect

    Not Available

    1988-12-01

    Long-term management of uranium mill tailings must provide assurance that soluble contaminants will not migrate beyond the Point of Compliance. Conventional management alternatives provide containment through the use of physical barriers which are designed to prevent migration of water through the tailings pile. An alternative is to geochemically modify the tailings to immobilize the contaminants. This investigation examined three potential geochemical modifiers to determine their ability to immobilize inorganic groundwater contaminants found in uranium mill tailings. These modifiers were hydrated lime (Ca(OH)[sub 2]), limestone (CaCO[sub 3]), and a sphaegnum peat moss. This investigation focused on both the geochemical interactions between the tailings and the modifiers, and the effects the modifiers had on the physical strength of the tailings. The geochemical investigations began with characterization of the tailings by X-ray diffraction and scanning electron microscopy. This was followed by batch leaching experiments in which various concentrations of each modifier were added to tailings in shaker flasks and allowed to come to equilibrium. Finally, column experiments were conducted to simulate flow through a tailings pile. The results show that all of the modifiers were at least moderately effective at immobilizing most of the groundwater contaminants of concern at uranium mill tailings sites. Hydrated lime was able to achieve 90 percent concentration reduction of arsenic, cadmium, selenium, uranium, and sulfate when added at a two percent concentration. Limestone was somewhat less effective and peat removed greater than 90 percent of arsenic, lead, uranium, and sulfate at a one percent concentration. The column tests showed that kinetic and/or mass transfer limitations are important and that sufficient time must be allowed for the immobilization reactions to occur.

  8. Hierarchical dynamic allocation procedures based on modified Zelen's approach in multiregional studies with unequal allocation.

    PubMed

    Kuznetsova, Olga M; Tymofyeyev, Yevgen

    2014-01-01

    Morrissey, McEntegart, and Lang (2010) showed that in multicenter studies with equal allocation to several treatment arms, the modified Zelen's approach provides excellent within-center and across-study balance in treatment assignments. In this article, hierarchical balancing procedures for equal allocation to more than two arms (with some elements different from earlier versions) and their unequal allocation expansions that incorporate modified Zelen's approach at the center level are described. The balancing properties of the described procedures for a case study of a multiregional clinical trial with 1:2 allocation where balance within regions as well as in other covariates is required are examined through simulations.

  9. Graphene-based room-temperature implementation of a modified Deutsch-Jozsa quantum algorithm.

    PubMed

    Dragoman, Daniela; Dragoman, Mircea

    2015-12-01

    We present an implementation of a one-qubit and two-qubit modified Deutsch-Jozsa quantum algorithm based on graphene ballistic devices working at room temperature. The modified Deutsch-Jozsa algorithm decides whether a function, equivalent to the effect of an energy potential distribution on the wave function of ballistic charge carriers, is constant or not, without measuring the output wave function. The function need not be Boolean. Simulations confirm that the algorithm works properly, opening the way toward quantum computing at room temperature based on the same clean-room technologies as those used for fabrication of very-large-scale integrated circuits. PMID:26541203

  10. Development of a thermal storage module using modified anhydrous sodium hydroxide

    NASA Technical Reports Server (NTRS)

    Rice, R. E.; Rowny, P. E.

    1980-01-01

    The laboratory scale testing of a modified anhydrous NaOH latent heat storage concept for small solar thermal power systems such as total energy systems utilizing organic Rankine systems is discussed. A diagnostic test on the thermal energy storage module and an investigation of alternative heat transfer fluids and heat exchange concepts are specifically addressed. A previously developed computer simulation model is modified to predict the performance of the module in a solar total energy system environment. In addition, the computer model is expanded to investigate parametrically the incorporation of a second heat exchange inside the module which will vaporize and superheat the Rankine cycle power fluid.

  11. Formation of fragments in heavy-ion collisions using a modified clusterization method

    SciTech Connect

    Goyal, Supriya; Puri, Rajeev K.

    2011-04-15

    We study the formation and stability of the fragments by extending the minimum spanning tree method (MST) for clusterization. In this extension, each fragment is subjected to a binding-energy check calculated using the modified Bethe-Weizsaecker formula. Earlier, a constant binding-energy cut of 4 MeV/nucleon was imposed. Our results for {sup 197}Au+{sup 197}Au collisions are compared with ALADiN data and also with the calculations based on the simulated annealing technique. We shall show that the present modified version improves the agreement compared to the MST method.

  12. Graphene-based room-temperature implementation of a modified Deutsch-Jozsa quantum algorithm

    NASA Astrophysics Data System (ADS)

    Dragoman, Daniela; Dragoman, Mircea

    2015-12-01

    We present an implementation of a one-qubit and two-qubit modified Deutsch-Jozsa quantum algorithm based on graphene ballistic devices working at room temperature. The modified Deutsch-Jozsa algorithm decides whether a function, equivalent to the effect of an energy potential distribution on the wave function of ballistic charge carriers, is constant or not, without measuring the output wave function. The function need not be Boolean. Simulations confirm that the algorithm works properly, opening the way toward quantum computing at room temperature based on the same clean-room technologies as those used for fabrication of very-large-scale integrated circuits.

  13. DNA polymerase having modified nucleotide binding site for DNA sequencing

    DOEpatents

    Tabor, Stanley; Richardson, Charles

    1997-01-01

    Modified gene encoding a modified DNA polymerase wherein the modified polymerase incorporates dideoxynucleotides at least 20-fold better compared to the corresponding deoxynucleotides as compared with the corresponding naturally-occurring DNA polymerase.

  14. DNA polymerase having modified nucleotide binding site for DNA sequencing

    DOEpatents

    Tabor, S.; Richardson, C.

    1997-03-25

    A modified gene encoding a modified DNA polymerase is disclosed. The modified polymerase incorporates dideoxynucleotides at least 20-fold better compared to the corresponding deoxynucleotides as compared with the corresponding naturally-occurring DNA polymerase. 6 figs.

  15. Virtual Instrument Simulator for CERES

    NASA Technical Reports Server (NTRS)

    Chapman, John J.

    1997-01-01

    A benchtop virtual instrument simulator for CERES (Clouds and the Earth's Radiant Energy System) has been built at NASA, Langley Research Center in Hampton, VA. The CERES instruments will fly on several earth orbiting platforms notably NASDA's Tropical Rainfall Measurement Mission (TRMM) and NASA's Earth Observing System (EOS) satellites. CERES measures top of the atmosphere radiative fluxes using microprocessor controlled scanning radiometers. The CERES Virtual Instrument Simulator consists of electronic circuitry identical to the flight unit's twin microprocessors and telemetry interface to the supporting spacecraft electronics and two personal computers (PC) connected to the I/O ports that control azimuth and elevation gimbals. Software consists of the unmodified TRW developed Flight Code and Ground Support Software which serves as the instrument monitor and NASA/TRW developed engineering models of the scanners. The CERES Instrument Simulator will serve as a testbed for testing of custom instrument commands intended to solve in-flight anomalies of the instruments which could arise during the CERES mission. One of the supporting computers supports the telemetry display which monitors the simulator microprocessors during the development and testing of custom instrument commands. The CERES engineering development software models have been modified to provide a virtual instrument running on a second supporting computer linked in real time to the instrument flight microprocessor control ports. The CERES Instrument Simulator will be used to verify memory uploads by the CERES Flight Operations TEAM at NASA. Plots of the virtual scanner models match the actual instrument scan plots. A high speed logic analyzer has been used to track the performance of the flight microprocessor. The concept of using an identical but non-flight qualified microprocessor and electronics ensemble linked to a virtual instrument with identical system software affords a relatively inexpensive

  16. Gout: a review of non-modifiable and modifiable risk factors

    PubMed Central

    MacFarlane, Lindsey A.; Kim, Seoyoung C.

    2014-01-01

    Gout is a common inflammatory arthritis triggered by the crystallization of uric acid within the joints. Gout affects millions worldwide and has an increasing prevalence. Recent research has been carried out to better qualify and quantify the risk factors predisposing individuals to gout. These can largely be broken into non-modifiable risk factors such as sex, age, race, and genetics, and modifiable risk factors such as diet and lifestyle. Increasing knowledge of factors predisposing certain individuals to gout could potentially lead to improved preventive practices. This review summarizes the non-modifiable and modifiable risk factors associated with development of gout. PMID:25437279

  17. Safety assessment of genetically modified foods.

    PubMed

    Taylor, S L

    2001-12-01

    The development of novel foods produced through agricultural biotechnology is a complex three-stage process: gene discovery, line selection, and product advancement to commercialization. The safety of genetically modified foods is an integral part of the overall developmental process throughout all of the stages. In the discovery stage, the safety of the gene, its source, and the gene products must be considered. If any questions arise at this stage, these questions must be answered later in the developmental process. During the line selection stage, the genetically modified seed progresses through a variety of greenhouse and field trials. At this stage, the biological and agronomic equivalence of the genetically modified crop to its traditional counterpart must be compared. While the evaluations made during this stage are not specifically directed toward a safety assessment, many potential products with unusual characteristics are eliminated during this stage of development. However, the elimination of products with unusual agronomic or biological characteristics enhances the likelihood that a safe product will be generated. Finally, in the pre-commercialization stage, the genetically modified product undergoes a detailed safety assessment process. This process focuses on the safety of the gene products associated with the introduced gene and any other likely toxicological or anti-nutrient factors associated with the source of the novel gene and the crop to which it was introduced. The safety of the genetically modified product for both food and feed uses is considered. Thus far, all of the genetically modified products brought into the marketplace have been subjected to such an intensive safety assessment. The safety assessment data have been reviewed by regulatory authorities around the world. The current generation of genetically modified products are quite safe for human and feed animal consumption.

  18. Optimal control strategy of malaria vector using genetically modified mosquitoes.

    PubMed

    Rafikov, M; Bevilacqua, L; Wyse, A P P

    2009-06-01

    The development of transgenic mosquitoes that are resistant to diseases may provide a new and effective weapon of diseases control. Such an approach relies on transgenic mosquitoes being able to survive and compete with wild-type populations. These transgenic mosquitoes carry a specific code that inhibits the plasmodium evolution in its organism. It is said that this characteristic is hereditary and consequently the disease fades away after some time. Once transgenic mosquitoes are released, interactions between the two populations and inter-specific mating between the two types of mosquitoes take place. We present a mathematical model that considers the generation overlapping and variable environment factors. Based on this continuous model, the malaria vector control is formulated and solved as an optimal control problem, indicating how genetically modified mosquitoes should be introduced in the environment. Numerical simulations show the effectiveness of the proposed control.

  19. Optical millimeter-wave generation with modified frequency quadrupling scheme

    NASA Astrophysics Data System (ADS)

    Zhao, Shanghong; Zhu, Zihang; Li, Yongjun; Chu, Xingchun; Li, Xuan

    2013-11-01

    A dispersion-tolerant full-duplex radio-over-fiber (RoF) system based on modified quadrupling-frequency optical millimeter (mm)-wave generation using an integrated nested Mach-Zehnder modulator (MZM), an electrical phase modulator, and an electrical gain is proposed. Not only does the scheme reduce the cost and complexity of base station by reusing the downlink optical carrier, but also the generated optical mm-wave signal with base-band data carried only by 1-s order sideband can overcome both the fading effect and bit walk-off effect caused by the fiber dispersion. Simulation results show that the eye diagram keeps open and clear even when the quadrupling-frequency optical mm-wave is transmitted over 120-km single-mode fiber, and the bidirectional 2.5 Gbit/s data are successfully transmitted over 40 km for both upstream and downstream channels with <1-dB power penalty.

  20. Venus: Interpreting the spatial distribution of volcanically modified craters

    NASA Astrophysics Data System (ADS)

    O'Rourke, Joseph G.; Wolf, Aaron S.; Ehlmann, Bethany L.

    2014-12-01

    To understand the impact cratering record on Venus, we investigate two distinct resurfacing styles: localized, thin flows and large shield volcanoes. We statistically analyze the size-frequency distribution of volcanically modified craters and, using Monte Carlo simulations, their spatial distribution. Lava flows partially fill most craters, darkening their floors in radar images. We find that a model featuring localized, thin flows occurring throughout geologic time predicts their observed distribution. Individual flows may be morphologically indistinguishable, but, combined, they cover large provinces. Recent mantle plumes may drive a small amount of hot spot magmatism that produces the observed clusters of large shield volcanoes and obviously embayed craters. Ultimately, our analysis demonstrates that two styles of volcanism are needed to explain the observed properties of impact craters and that catastrophic resurfacing is not required.

  1. A new modified Smith predictor: the concept, design and tuning.

    PubMed

    Vrecko, D; Vrancić, D; Juricić, D; Strmcnik, S

    2001-01-01

    The paper presents a new modified Smith predictor (MSP) for processes with a long time delay. The MSP appears as an extension of the double controller-scheme (DCS) proposed by Tian and Gao. The important feature of the MSP is that the trade-off between disturbance rejection and robustness to variations in process parameters can be adjusted by means of a single free parameter. The main contribution of the paper concerns tuning of the MSP, which relies on a combination of magnitude optimum criterion with process parameterisation based on multiple integrals of the open-loop step response. In a simulation study the performance of the MSP is compared with that of two known controllers for time delay systems, i.e. DCS of Tian and Gao and Hägglund's predictive PI controller. The results show the advantage of the MSP compared to the two other controllers.

  2. Ultrasonic flaw detection using threshold modified S-transform.

    PubMed

    Benammar, Abdessalem; Drai, Redouane; Guessoum, Abderrezak

    2014-02-01

    Interference noising originating from the ultrasonic testing defect signal seriously influences the accuracy of the signal extraction and defect location. Time-frequency analysis methods are mainly used to improve the defects detection resolution. In fact, the S-transform, a hybrid of the Short time Fourier transform (STFT) and wavelet transform (WT), has a time frequency resolution which is far from ideal. In this paper, a new modified S-transform based on thresholding technique, which offers a better time frequency resolution compared to the original S-transform is proposed. The improvement is achieved by the introduction of a new scaling rule for the Gaussian window used in S-transform. Simulation results are presented and show correct time frequency information of multiple Gaussian echoes under low signal-to-noise ratio (SNR) environment. In addition, experimental results demonstrate better and reliable detection of close echoes drowned in the noise.

  3. Modified Truncated Cone Target Hyperthermal Atomic Oxygen Test Results

    NASA Technical Reports Server (NTRS)

    Vaughn, J. A.; Kamenetsky, R. R.; Finckenor, M. M.

    1999-01-01

    The modified truncated cone target is a docking target planned for use on the International Space Station. The current design consists of aluminum treated with a black dye anodize, then crosshairs are laser etched for a silvery color. Samples of the treated aluminum were exposed to laboratory simulation of atomic oxygen and ultraviolet radiation to determine if significant degradation might occur. Durability was evaluated based on the contrast ratio between the black and silvery white areas of the target. Degradation of optical properties appeared to level off after an initial period of exposure to atomic oxygen. The sample that was not alodined according to MIL-C-5541, type 1A, performed better than alodined samples.

  4. Adaptation to Room Acoustics Using the Modified Rhyme Test

    PubMed Central

    Brandewie, Eugene; Zahorik, Pavel

    2012-01-01

    The negative effect of reverberant sound energy on speech intelligibility is well documented. Recently, however, prior exposure to room acoustics has been shown to increase intelligibility for a number of listeners in simulated room environments. This room adaptation effect, a possible extension of dynamic echo suppression, has been shown to be specific to reverberant rooms and requires binaural input. Because this effect has been demonstrated only using the Coordinated Response Measure (CRM) corpus it is important to determine whether the increase in intelligibility scores reported previously was due to the specific nature of the CRM task. Here we demonstrate a comparable room-acoustic effect using the Modified Rhyme Test (MRT) corpus in multiple room environments. The results are consistent with the idea that the room adaptation effect may be a natural phenomenon of listening in reverberant environments. PMID:23437415

  5. Modulation of Microtubule Interprotofilament Interactions by Modified Taxanes

    PubMed Central

    Matesanz, Ruth; Rodríguez-Salarichs, Javier; Pera, Benet; Canales, Ángeles; Andreu, José Manuel; Jiménez-Barbero, Jesús; Bras, Wim; Nogales, Aurora; Fang, Wei-Shuo; Díaz, José Fernando

    2011-01-01

    Microtubules assembled with paclitaxel and docetaxel differ in their numbers of protofilaments, reflecting modification of the lateral association between αβ-tubulin molecules in the microtubule wall. These modifications of microtubule structure, through a not-yet-characterized mechanism, are most likely related to the changes in tubulin-tubulin interactions responsible for microtubule stabilization by these antitumor compounds. We have used a set of modified taxanes to study the structural mechanism of microtubule stabilization by these ligands. Using small-angle x-ray scattering, we have determined how modifications in the shape and size of the taxane substituents result in changes in the interprotofilament angles and in their number. The observed effects have been explained using NMR-aided docking and molecular dynamic simulations of taxane binding at the microtubule pore and luminal sites. Modeling results indicate that modification of the size of substituents at positions C7 and C10 of the taxane core influence the conformation of three key elements in microtubule lateral interactions (the M-loop, the S3 β-strand, and the H3 helix) that modulate the contacts between adjacent protofilaments. In addition, modifications of the substituents at position C2 slightly rearrange the ligand in the binding site, modifying the interaction of the C7 substituent with the M-loop. PMID:22208196

  6. Chemically modified solid state nanopores for high throughput nanoparticle separation

    NASA Astrophysics Data System (ADS)

    Prabhu, Anmiv S.; Jubery, Talukder Zaki N.; Freedman, Kevin J.; Mulero, Rafael; Dutta, Prashanta; Kim, Min Jun

    2010-11-01

    The separation of biomolecules and other nanoparticles is a vital step in several analytical and diagnostic techniques. Towards this end we present a solid state nanopore-based set-up as an efficient separation platform. The translocation of charged particles through a nanopore was first modeled mathematically using the multi-ion model and the surface charge density of the nanopore membrane was identified as a critical parameter that determines the selectivity of the membrane and the throughput of the separation process. Drawing from these simulations a single 150 nm pore was fabricated in a 50 nm thick free-standing silicon nitride membrane by focused-ion-beam milling and was chemically modified with (3-aminopropyl)triethoxysilane to change its surface charge density. This chemically modified membrane was then used to separate 22 and 58 nm polystyrene nanoparticles in solution. Once optimized, this approach can readily be scaled up to nanopore arrays which would function as a key component of next-generation nanosieving systems.

  7. Unscreening Modified Gravity in the Matter Power Spectrum.

    PubMed

    Lombriser, Lucas; Simpson, Fergus; Mead, Alexander

    2015-06-26

    Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k<0.3h/Mpc can yield constraints on chameleon models that are more stringent than what is inferred from Solar System tests or distance indicators in unscreened dwarf galaxies. Finally, we verify that our method is also applicable to the Vainshtein mechanism. PMID:26197114

  8. Halo velocity profiles in screened modified gravity theories

    NASA Astrophysics Data System (ADS)

    Gronke, M.; Llinares, C.; Mota, D. F.; Winther, H. A.

    2015-05-01

    Screened modified gravity predicts potentially large signatures in the peculiar velocity field that makes it an interesting probe to test gravity on cosmological scales. We investigate the signatures induced by the Symmetron and a Chameleon f(R) model in the peculiar velocity field using N-body simulations. By studying fifth force and halo velocity profiles, we identify three general categories of effects found in screened modified gravity models: a fully screened regime where we recover Λ cold dark matter to high precision, an unscreened regime where the fifth force is in full operation, and, a partially screened regime where screening occurs in the inner part of a halo, but the fifth force is active at larger radii. These three regimes can be pointed out very clearly by analysing the deviation in the maximum cluster velocity. Observationally, the partially screened regime is of particular interest since an uniform increase of the gravitational force - as present in the unscreened regime - is degenerate with the (dynamical) halo mass estimate, and, thus, hard to detect.

  9. Unscreening Modified Gravity in the Matter Power Spectrum.

    PubMed

    Lombriser, Lucas; Simpson, Fergus; Mead, Alexander

    2015-06-26

    Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k<0.3h/Mpc can yield constraints on chameleon models that are more stringent than what is inferred from Solar System tests or distance indicators in unscreened dwarf galaxies. Finally, we verify that our method is also applicable to the Vainshtein mechanism.

  10. Debye Entropic Force and Modified Newtonian Dynamics

    NASA Astrophysics Data System (ADS)

    Li, Xin; Chang, Zhe

    2011-04-01

    Verlinde has suggested that the gravity has an entropic origin, and a gravitational system could be regarded as a thermodynamical system. It is well-known that the equipartition law of energy is invalid at very low temperature. Therefore, entropic force should be modified while the temperature of the holographic screen is very low. It is shown that the modified entropic force is proportional to the square of the acceleration, while the temperature of the holographic screen is much lower than the Debye temperature TD. The modified entropic force returns to the Newton's law of gravitation while the temperature of the holographic screen is much higher than the Debye temperature. The modified entropic force is connected with modified Newtonian dynamics (MOND). The constant a0 involved in MOND is linear in the Debye frequency ωD, which can be regarded as the largest frequency of the bits in screen. We find that there do have a strong connection between MOND and cosmology in the framework of Verlinde's entropic force, if the holographic screen is taken to be bound of the Universe. The Debye frequency is linear in the Hubble constant H0.

  11. Simulations of Boundary Turbulence in Tokamak Experiments

    SciTech Connect

    Nevins, W M; Xu, X Q; Carlstrom, T N; Cohen, R H; Groebner, R; Jennings, T; LaBombard, B; Maqueda, R A; Mazurenko, A; McKee, G R; Moyer, R; Mossessian, D; Porkolab, M; Porter, G D; Rensink, M E; Rhodes, T L; Rognlien, T D; Rost, C; Snipes, J; Stotler, D P; Terry, J; Zweben, S

    2002-10-11

    Comparisons between the boundary plasma turbulence observed in the BOUT code and experiments on C-Mod, NSTX, and DIII-D are presented. BOUT is a 3D non-local electromagnetic turbulence simulation code which models boundary-plasma turbulence in a realistic divertor geometry using the modified Braginskii equations for plasma vorticity, density, the electron and ion temperatures and parallel momenta. Many features of the Quasi-Coherent (QC) mode, observed at high densities during enhanced D-alpha (EDA) H-Mode in Alcator C-Mod, are reproduced in BOUT simulations. The spatial structure of boundary plasma turbulence as observed by gas puff imaging (GPI) from discharges on NSTX and C-Mod are in general (NSTX) to good (CMod) agreement with BOUT simulations. Finally, BOUT simulations of DIII-D L-mode experiments near the Hmode transition threshold are in broad agreement with the experimental results.

  12. Probing hybrid modified gravity by stellar motion around Galactic Center

    NASA Astrophysics Data System (ADS)

    Borka, D.; Capozziello, S.; Jovanović, P.; Borka Jovanović, V.

    2016-06-01

    We consider possible signatures for the so called hybrid gravity within the Galactic Central Parsec. This modified theory of gravity consists of a superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed à la Palatiniand can be easily reduced to an equivalent scalar-tensor theory. Such an approach is introduced in order to cure the shortcomings related to f(R) gravity, in general formulated either in metric or in metric-affine frameworks. Hybrid gravity allows to disentangle the further gravitational degrees of freedom with respect to those of standard General Relativity. The present analysis is based on the S2 star orbital precession around the massive compact dark object at the Galactic Center where the simulated orbits in hybrid modified gravity are compared with astronomical observations. These simulations result with constraints on the range of hybrid gravity interaction parameter ϕ0, showing that in the case of S2 star it is between -0.0009 and -0.0002. At the same time, we are also able to obtain the constraints on the effective mass parameter mϕ, and found that it is between -0.0034 and -0.0025 AU-1 for S2 star. Furthermore, the hybrid gravity potential induces precession of S2 star orbit in the same direction as General Relativity. In previous papers, we considered other types of extended gravities, like metric power law f(R)∝Rn gravity, inducing Yukawa and Sanders-like gravitational potentials, but it seems that hybrid gravity is the best among these models to explain different gravitational phenomena at different astronomical scales.

  13. Numerical analysis of modified Central Solenoid insert design

    DOE PAGESBeta

    Khodak, Andrei; Martovetsky, Nicolai; Smirnov, Aleksandre; Titus, Peter

    2015-06-21

    The United States ITER Project Office (USIPO) is responsible for fabrication of the Central Solenoid (CS) for ITER project. The ITER machine is currently under construction by seven parties in Cadarache, France. The CS Insert (CSI) project should provide a verification of the conductor performance in relevant conditions of temperature, field, currents and mechanical strain. The US IPO designed the CSI that will be tested at the Central Solenoid Model Coil (CSMC) Test Facility at JAEA, Naka. To validate the modified design we performed three-dimensional numerical simulations using coupled solver for simultaneous structural, thermal and electromagnetic analysis. Thermal and electromagneticmore » simulations supported structural calculations providing necessary loads and strains. According to current analysis design of the modified coil satisfies ITER magnet structural design criteria for the following conditions: (1) room temperature, no current, (2) temperature 4K, no current, (3) temperature 4K, current 60 kA direct charge, and (4) temperature 4K, current 60 kA reverse charge. Fatigue life assessment analysis is performed for the alternating conditions of: temperature 4K, no current, and temperature 4K, current 45 kA direct charge. Results of fatigue analysis show that parts of the coil assembly can be qualified for up to 1 million cycles. Distributions of the Current Sharing Temperature (TCS) in the superconductor were obtained from numerical results using parameterization of the critical surface in the form similar to that proposed for ITER. Lastly, special ADPL scripts were developed for ANSYS allowing one-dimensional representation of TCS along the cable, as well as three-dimensional fields of TCS in superconductor material. Published by Elsevier B.V.« less

  14. Numerical analysis of modified Central Solenoid insert design

    SciTech Connect

    Khodak, Andrei; Martovetsky, Nicolai; Smirnov, Aleksandre; Titus, Peter

    2015-06-21

    The United States ITER Project Office (USIPO) is responsible for fabrication of the Central Solenoid (CS) for ITER project. The ITER machine is currently under construction by seven parties in Cadarache, France. The CS Insert (CSI) project should provide a verification of the conductor performance in relevant conditions of temperature, field, currents and mechanical strain. The US IPO designed the CSI that will be tested at the Central Solenoid Model Coil (CSMC) Test Facility at JAEA, Naka. To validate the modified design we performed three-dimensional numerical simulations using coupled solver for simultaneous structural, thermal and electromagnetic analysis. Thermal and electromagnetic simulations supported structural calculations providing necessary loads and strains. According to current analysis design of the modified coil satisfies ITER magnet structural design criteria for the following conditions: (1) room temperature, no current, (2) temperature 4K, no current, (3) temperature 4K, current 60 kA direct charge, and (4) temperature 4K, current 60 kA reverse charge. Fatigue life assessment analysis is performed for the alternating conditions of: temperature 4K, no current, and temperature 4K, current 45 kA direct charge. Results of fatigue analysis show that parts of the coil assembly can be qualified for up to 1 million cycles. Distributions of the Current Sharing Temperature (TCS) in the superconductor were obtained from numerical results using parameterization of the critical surface in the form similar to that proposed for ITER. Lastly, special ADPL scripts were developed for ANSYS allowing one-dimensional representation of TCS along the cable, as well as three-dimensional fields of TCS in superconductor material. Published by Elsevier B.V.

  15. Geographically Isolated Wetlands and Catchment Hydrology: A Modified Model Analyses

    NASA Astrophysics Data System (ADS)

    Evenson, G.; Golden, H. E.; Lane, C.; D'Amico, E.

    2014-12-01

    Geographically isolated wetlands (GIWs), typically defined as depressional wetlands surrounded by uplands, support an array of hydrological and ecological processes. However, key research questions concerning the hydrological connectivity of GIWs and their impacts on downgradient surface waters remain unanswered. This is particularly important for regulation and management of these systems. For example, in the past decade United States Supreme Court decisions suggest that GIWs can be afforded protection if significant connectivity exists between these waters and traditional navigable waters. Here we developed a simulation procedure to quantify the effects of various spatial distributions of GIWs across the landscape on the downgradient hydrograph using a refined version of the Soil and Water Assessment Tool (SWAT), a catchment-scale hydrological simulation model. We modified the SWAT FORTRAN source code and employed an alternative hydrologic response unit (HRU) definition to facilitate an improved representation of GIW hydrologic processes and connectivity relationships to other surface waters, and to quantify their downgradient hydrological effects. We applied the modified SWAT model to an ~ 202 km2 catchment in the Coastal Plain of North Carolina, USA, exhibiting a substantial population of mapped GIWs. Results from our series of GIW distribution scenarios suggest that: (1) Our representation of GIWs within SWAT conforms to field-based characterizations of regional GIWs in most respects; (2) GIWs exhibit substantial seasonally-dependent effects upon downgradient base flow; (3) GIWs mitigate peak flows, particularly following high rainfall events; and (4) The presence of GIWs on the landscape impacts the catchment water balance (e.g., by increasing groundwater outflows). Our outcomes support the hypothesis that GIWs have an important catchment-scale effect on downgradient streamflow.

  16. Satellite ground-terminal user simulation

    NASA Technical Reports Server (NTRS)

    Shalkhauser, Mary Jo W.

    1988-01-01

    Realistic simulation of satellite communication systems and evaluation of satellite networking schemes require emulation of the systems's users. A laboratory model of a Ka-band satellite-switched time-division multiple-access (SS-TDMA) communication network, referred to as the System Integration, Test, and Evaluation (SITE) project, uses special bit-error-rate (BER) test sets to simulate the transmitting and receiving users of a communication network. The bit-error-rate test sets contain circuit boards that can be modified to create a variety of interfaces to satellite system ground terminals.

  17. Computer Simulation of the VASIMR Engine

    NASA Technical Reports Server (NTRS)

    Garrison, David

    2005-01-01

    The goal of this project is to develop a magneto-hydrodynamic (MHD) computer code for simulation of the VASIMR engine. This code is designed be easy to modify and use. We achieve this using the Cactus framework, a system originally developed for research in numerical relativity. Since its release, Cactus has become an extremely powerful and flexible open source framework. The development of the code will be done in stages, starting with a basic fluid dynamic simulation and working towards a more complex MHD code. Once developed, this code can be used by students and researchers in order to further test and improve the VASIMR engine.

  18. Tissue-Simulating Gel For Medical Research

    NASA Technical Reports Server (NTRS)

    Companion, John A.

    1992-01-01

    Nonhardening, translucent gel more nearly simulates soft human or animal tissue. Modified to be softer or harder by altering proportions of ingredients. Fillers added to change electrical, mechanical, heat-conducting, or sound-conducting/scattering properties. Molded to any desired shape and has sufficient mechanical strength to maintain shape without supporting shell. Because of its thermal stability, gel especially useful for investigation of hyperthermia as treatment for cancer.

  19. NASA TileWorld Simulator Program

    NASA Technical Reports Server (NTRS)

    Philips, Andrew; Bresina, John; Drummond, Mark

    1993-01-01

    NASA TileWorld (NTW) computer program formulated to further research on planning, scheduling, and control problems. Designed to focus on three particular attributes of real-world problems: exogenous events, uncertain outcomes of actions, and metric time. Written specifically for use by NASA, NTW modified easily to act as software base for other simulated environments. Written in Allegro Common Lisp for Sun-3-(TM) and Sun-4-series(TM) computers running SunOS(TM).

  20. Plants having modified response to ethylene

    DOEpatents

    Meyerowitz, E.M.; Chang, C.; Bleecker, A.B.

    1997-11-18

    The invention includes transformed plants having at least one cell transformed with a modified ETR nucleic acid. Such plants have a phenotype characterized by a decrease in the response of at least one transformed plant cell to ethylene as compared to a plant not containing the transformed plant cell. Tissue and/or temporal specificity for expression of the modified ETR nucleic acid is controlled by selecting appropriate expression regulation sequences to target the location and/or time of expression of the transformed nucleic acid. The plants are made by transforming at least one plant cell with an appropriate modified ETR nucleic acid, regenerating plants from one or more of the transformed plant cells and selecting at least one plant having the desired phenotype. 31 figs.

  1. Plants having modified response to ethylene

    DOEpatents

    Meyerowitz, Elliot M.; Chang, Caren; Bleecker, Anthony B.

    1998-01-01

    The invention includes transformed plants having at least one cell transformed with a modified ETR nucleic acid. Such plants have a phenotype characterized by a decrease in the response of at least one transformed plant cell to ethylene as compared to a plant not containing the transformed plant cell. Tissue and/or temporal specificity for expression of the modified ETR nucleic acid is controlled by selecting appropriate expression regulation sequences to target the location and/or time of expression of the transformed nucleic acid. The plants are made by transforming at least one plant cell with an appropriate modified ETR nucleic acid, regenerating plants from one or more of the transformed plant cells and selecting at least one plant having the desired phenotype.

  2. Plants having modified response to ethylene

    DOEpatents

    Meyerowitz, Elliott M.; Chang, Caren; Bleecker, Anthony B.

    1997-01-01

    The invention includes transformed plants having at least one cell transformed with a modified ETR nucleic acid. Such plants have a phenotype characterized by a decrease in the response of at least one transformed plant cell to ethylene as compared to a plant not containing the transformed plant cell. Tissue and/or temporal specificity for expression of the modified ETR nucleic acid is controlled by selecting appropriate expression regulation sequences to target the location and/or time of expression of the transformed nucleic acid. The plants are made by transforming at least one plant cell with an appropriate modified ETR nucleic acid, regenerating plants from one or more of the transformed plant cells and selecting at least one plant having the desired phenotype.

  3. Plants having modified response to ethylene

    DOEpatents

    Meyerowitz, E.M.; Chang, C.; Bleecker, A.B.

    1998-10-20

    The invention includes transformed plants having at least one cell transformed with a modified ETR nucleic acid. Such plants have a phenotype characterized by a decrease in the response of at least one transformed plant cell to ethylene as compared to a plant not containing the transformed plant cell. Tissue and/or temporal specificity for expression of the modified ETR nucleic acid is controlled by selecting appropriate expression regulation sequences to target the location and/or time of expression of the transformed nucleic acid. The plants are made by transforming at least one plant cell with an appropriate modified ETR nucleic acid, regenerating plants from one or more of the transformed plant cells and selecting at least one plant having the desired phenotype. 67 figs.

  4. [Genetically modified food and allergies - an update].

    PubMed

    Niemann, Birgit; Pöting, Annette; Braeuning, Albert; Lampen, Alfonso

    2016-07-01

    Approval by the European Commission is mandatory for placing genetically modified plants as food or feed on the market in member states of the European Union (EU). The approval is preceded by a safety assessment based on the guidance of the European Food Safety Authority EFSA. The assessment of allergenicity of genetically modified plants and their newly expressed proteins is an integral part of this assessment process. Guidance documents for the assessment of allergenicity are currently under revision. For this purpose, an expert workshop was conducted in Brussels on June 17, 2015. There, methodological improvements for the assessment of coeliac disease-causing properties of proteins, as well as the use of complex models for in vitro digestion of proteins were discussed. Using such techniques a refinement of the current, proven system of allergenicity assessment of genetically modified plants can be achieved.

  5. Attitudes towards genetically modified and organic foods.

    PubMed

    Saher, Marieke; Lindeman, Marjaana; Hursti, Ulla-Kaisa Koivisto

    2006-05-01

    Finnish students (N=3261) filled out a questionnaire on attitudes towards genetically modified and organic food, plus the rational-experiential inventory, the magical thinking about food and health scale, Schwartz's value survey and the behavioural inhibition scale. In addition, they reported their eating of meat. Structural equation modelling of these measures had greater explanatory power for attitudes towards genetically modified (GM) foods than for attitudes towards organic foods (OF). GM attitudes were best predicted by natural science education and magical food and health beliefs, which mediated the influence of thinking styles. Positive attitudes towards organic food, on the other hand, were more directly related to such individual differences as thinking styles and set of values. The results of the study indicate that OF attitudes are rooted in more fundamental personal attributes than GM attitudes, which are embedded in a more complex but also in a more modifiable network of characteristics.

  6. Genetically Modified Foods and Consumer Perspective.

    PubMed

    Boccia, Flavio; Sarnacchiaro, Pasquale

    2015-01-01

    Genetically modified food is able to oppose the world's hunger and preserve the environment, even if the patents in this matter are symptomatic of several doubts. And also, transgenic consumption causes problems and skepticism among consumers in several European countries, but above all in Italy, where there is a strong opposition over recent years. So, the present study conducted a research to study the consumption of genetically modified food products by Italian young generation. This research presented the following purposes: firstly, to analyze genetically modified products' consumption among a particular category of consumers; secondly, to implement a quantitative model to understand behaviour about this particular kind of consumption and identify the factors that determine their purchase. The proposed model shows that transgenic consumption is especially linked to knowledge and impact on environment and mankind's health.

  7. [Modified albumin in harp seal blood serum].

    PubMed

    Erokhina, I A

    1999-01-01

    The content of modified albumin (Am) in harp seal (Pagophilus groenlandica Erxleben, 1777) blood serum was studied. Am was determined by paper electrophoresis by means of re-precipitation in the trichloroacetic acid-ethanol system. Modified albumin content in normal seal pups' blood serum increased from 1990 to 1994. The Am level in undernourished pups was stable from year to year and higher than in normal pups. In oceanarium investigations it was revealed a low albumin resistance to denaturation and the dependence of Am content on the animals' physiological state. Thus there is a possibility to regard modified albumin content as one of the significant parameters in biomonitoring of harp seal population and, moreover, as a supplementary criterion for estimation of seals' health state in captivity.

  8. [Peroxidase activity of catalase modified by progesterone].

    PubMed

    Artemchik, V D; Matveentsev, V D; Metelitsa, D I

    1986-08-01

    Catalase conjugates with 3, 7, 9 and 42 progesterone molecules were obtained by the reaction between the enzyme and N-oxy-succinimide ether of 3-0-carboxymethyloxime of progesterone. The enzyme modified by 42 progesterone molecules is effective in o-dianisidine oxidation by hydrogen peroxide and has a kcat/KM value of 512 M-1 s-1. The catalase conjugates with 3, 7 and 9 progesterone molecules exhibit a high activity during o-dianisidine oxidation by cumene hydroperoxide. The activity of conjugates is higher than that of the native non-modified enzyme in the same reaction. The maximum effectiveness was observed for catalase modified by 7 progesterone molecules. This conjugate is characterized by kcat/KM of 99,000 M-1 s-1 at 30 degrees C. The effect of the degree of enzyme modification on the kinetic parameters of o-dianisidine oxidation by H2O2 and cumene hydroperoxide is discussed. PMID:3021241

  9. [Genetically modified food and allergies - an update].

    PubMed

    Niemann, Birgit; Pöting, Annette; Braeuning, Albert; Lampen, Alfonso

    2016-07-01

    Approval by the European Commission is mandatory for placing genetically modified plants as food or feed on the market in member states of the European Union (EU). The approval is preceded by a safety assessment based on the guidance of the European Food Safety Authority EFSA. The assessment of allergenicity of genetically modified plants and their newly expressed proteins is an integral part of this assessment process. Guidance documents for the assessment of allergenicity are currently under revision. For this purpose, an expert workshop was conducted in Brussels on June 17, 2015. There, methodological improvements for the assessment of coeliac disease-causing properties of proteins, as well as the use of complex models for in vitro digestion of proteins were discussed. Using such techniques a refinement of the current, proven system of allergenicity assessment of genetically modified plants can be achieved. PMID:27240596

  10. Silicone modified resins for graphite fiber laminates

    NASA Technical Reports Server (NTRS)

    Frost, L. W.; Bower, G. M.

    1979-01-01

    The development of silicon modified resins for graphite fiber laminates which will prevent the dispersal of graphite fibers when the composites are burned is discussed. Eighty-five silicone modified resins were synthesized and evaluated including unsaturated polyesters, thermosetting methacrylates, epoxies, polyimides, and phenolics. Neat resins were judged in terms of Si content, homogeneity, hardness, Char formation, and thermal stability. Char formation was estimated by thermogravimetry to 1,000 C in air and in N2. Thermal stability was evaluated by isothermal weight loss measurements for 200 hrs in air at three temperatures. Four silicone modified epoxies were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 25 to 50%. The highest flexural values measured for the laminates were a strength of 140 kpsi and a modulus of 10 Mpsi. The highest interlaminar shear strength was 5.3 kpsi.

  11. Detection of genetically modified organisms in foods.

    PubMed

    Ahmed, Farid E

    2002-05-01

    Legislation enacted worldwide to regulate the presence of genetically modified organisms (GMOs) in crops, foods and ingredients, necessitated the development of reliable and sensitive methods for GMO detection. In this article, protein- and DNA-based methods employing western blots, enzyme-linked immunosorbant assay, lateral flow strips, Southern blots, qualitative-, quantitative-, real-time- and limiting dilution-PCR methods, are discussed. Where information on modified gene sequences is not available, new approaches, such as near-infrared spectrometry, might tackle the problem of detection of non-approved genetically modified (GM) foods. The efficiency of screening, identification and confirmation strategies should be examined with respect to false-positive rates, disappearance of marker genes, increased use of specific regulator sequences and the increasing number of GM foods.

  12. Safety assessment of a modified acetolactate synthase protein (GM-HRA) used as a selectable marker in genetically modified soybeans.

    PubMed

    Mathesius, C A; Barnett, J F; Cressman, R F; Ding, J; Carpenter, C; Ladics, G S; Schmidt, J; Layton, R J; Zhang, J X Q; Appenzeller, L M; Carlson, G; Ballou, S; Delaney, B

    2009-12-01

    Acetolactate synthase (ALS) enzymes have been isolated from numerous organisms including soybeans (Glycine max; GM-ALS) and catalyze the first common step in biosynthesis of branched chain amino acids. Expression of an ALS protein (GM-HRA) with two amino acid changes relative to native GM-ALS protein in genetically modified soybeans confers tolerance to herbicidal active ingredients and can be used as a selectable transformation marker. The safety assessment of the GM-HRA protein is discussed. Bioinformatics comparison of the amino acid sequence did not identify similarities to known allergenic or toxic proteins. In vitro studies demonstrated rapid degradation in simulated gastric fluid (<30s) and intestinal fluid (<1min). The enzymatic activity was completely inactivated at 50 degrees C for 15 min demonstrating heat lability. The protein expressed in planta is not glycosylated and genetically modified soybeans expressing the GM-HRA protein produced similar protein/allergen profiles as its non-transgenic parental isoline. No adverse effects were observed in mice following acute oral exposure at a dose of at least 436 mg/kg of body weight or in a 28-day repeated dose dietary toxicity study at doses up to 1247 mg/kg of body weight/day. The results demonstrate GM-HRA protein safety when used in agricultural biotechnology.

  13. Modified Kriging: evaluation, modification, and recommendations

    SciTech Connect

    Schultz, C.A.; Myers, S.C.

    1997-09-01

    This report describes modifications to a technique developed by Sandia National Laboratory (SNL) to predict general corrections (traveltime, etc.) for a geographic grid only sparsely covered by calibration points (Hipp and Young, 1997). SNL has worked to create a modified version of linear prediction (kriging) based on the idea of blending the surface back to zero at some distance from the points or, in other words, by damping the solution through the damping of the input data points. LLNL has been working with SNL to evaluate Modified Kriging. This report documents our evaluation of the technique and our resulting recommendations to SNL.

  14. Modified chemiluminescent NO analyzer accurately measures NOX

    NASA Technical Reports Server (NTRS)

    Summers, R. L.

    1978-01-01

    Installation of molybdenum nitric oxide (NO)-to-higher oxides of nitrogen (NOx) converter in chemiluminescent gas analyzer and use of air purge allow accurate measurements of NOx in exhaust gases containing as much as thirty percent carbon monoxide (CO). Measurements using conventional analyzer are highly inaccurate for NOx if as little as five percent CO is present. In modified analyzer, molybdenum has high tolerance to CO, and air purge substantially quenches NOx destruction. In test, modified chemiluminescent analyzer accurately measured NO and NOx concentrations for over 4 months with no denegration in performance.

  15. Magnetically modified microalgae and their applications.

    PubMed

    Safarik, Ivo; Prochazkova, Gita; Pospiskova, Kristyna; Branyik, Tomas

    2016-10-01

    The majority of algal cells can interact with a wide range of nano- and microparticles. Upon interaction the modified cells usually maintain their viability and the presence of foreign material on their surfaces or in protoplasm can provide additional functionalities. Magnetic modification and labeling of microalgal biomass ensures a wide spectrum of biotechnological, bioanalytical and environmental applications. Different aspects of microalgal cell magnetic modification are covered in the review, followed by successful applications of magnetic algae. Modified cells can be employed during their harvesting and removal, applied in toxicity microscreening devices and also as efficient adsorbents of different types of xenobiotics. PMID:26154466

  16. Electrochemical apparatus comprising modified disposable rectangular cuvette

    DOEpatents

    Dattelbaum, Andrew M; Gupta, Gautam; Morris, David E

    2013-09-10

    Electrochemical apparatus includes a disposable rectangular cuvette modified with at least one hole through a side and/or the bottom. Apparatus may include more than one cuvette, which in practice is a disposable rectangular glass or plastic cuvette modified by drilling the hole(s) through. The apparatus include two plates and some means of fastening one plate to the other. The apparatus may be interfaced with a fiber optic or microscope objective, and a spectrometer for spectroscopic studies. The apparatus are suitable for a variety of electrochemical experiments, including surface electrochemistry, bulk electrolysis, and flow cell experiments.

  17. Coprecal: materials accounting in the modified process

    SciTech Connect

    Dayem, H.A.; Kern, E.A.; Shipley, J.P.

    1980-05-01

    This report presents the design and evaluation of an advanced materials accounting system for a uranium-plutonium nitrate-to-oxide coconversion facility based on the General Electric Coprecal process as modified by Savannah River Laboratory and Plant and DuPont Engineering. The modifications include adding small aliquot tanks to feed the process and reconfiguring the calciner filter systems. Diversion detection sensitivities for the modified Coprecal process are somewhat better than the original Coprecal design, but they are still significantly worse than a same-sized conversion facility based on the oxalate (III) precipitation process.

  18. Polysaccharide-Modified Synthetic Polymeric Biomaterials

    PubMed Central

    Baldwin, Aaron D.; Kiick, Kristi L.

    2010-01-01

    This review presents an overview of polysaccharide-conjugated synthetic polymers and their use in tissue-engineered scaffolds and drug-delivery applications. This topic will be divided into four categories: (1) polymeric materials modified with non-mammalian polysaccharides such as alginate, chitin, and dextran; (2) polymers modified with mammalian polysaccharides such as hyaluronan, chondroitin sulfate, and heparin; (3) multi-polysaccharide-derivatized polymer conjugate systems; and (4) polymers containing polysaccharide-mimetic molecules. Each section will discuss relevant conjugation techniques, analysis, and the impact of these materials as micelles, particles, or hydrogels used in in-vitro and in-vivo biomaterial applications. PMID:20091875

  19. Modified negative-branch confocal unstable resonator.

    PubMed

    Hall, Thomas; Duschek, Frank; Grünewald, Karin M; Handke, Jürgen

    2006-12-01

    A new type of unstable resonator, suitable for a laser with a large medium cross section and a small or median output coupling, is presented. The resonator configuration, a modification of a negative-branch confocal unstable resonator, is numerically investigated. The basis of the theory is the Fresnel-Kirchhoff integral equation, and the calculations describe a passive resonator. With respect to output mirror tilting, the calculations confirm that the modified negative-branch confocal unstable resonator is less sensitive to mirror misalignments than the conventional negative-branch confocal unstable resonator. Furthermore, the modified resonator improves the beam quality in comparison with the conventional unstable resonator. PMID:17119575

  20. Thermodynamic properties of modified gravity theories

    NASA Astrophysics Data System (ADS)

    Bamba, Kazuharu

    2016-06-01

    We review thermodynamic properties of modified gravity theories, such as F(R) gravity and f(T) gravity, where R is the scalar curvature and T is the torsion scalar in teleparallelism. In particular, we explore the equivalence between the equations of motion for modified gravity theories and the Clausius relation in thermodynamics. In addition, thermodynamics of the cosmological apparent horizon is investigated in f(T) gravity. We show both equilibrium and nonequilibrium descriptions of thermodynamics. It is demonstrated that the second law of thermodynamics in the universe can be met, when the temperature of the outside of the apparent horizon is equivalent to that of the inside of it.

  1. Polysaccharide-modified synthetic polymeric biomaterials.

    PubMed

    Baldwin, Aaron D; Kiick, Kristi L

    2010-01-01

    This review presents an overview of polysaccharide-conjugated synthetic polymers and their use in tissue-engineered scaffolds and drug-delivery applications. This topic will be divided into four categories: (1) polymeric materials modified with non-mammalian polysaccharides such as alginate, chitin, and dextran; (2) polymers modified with mammalian polysaccharides such as hyaluronan, chondroitin sulfate, and heparin; (3) multi-polysaccharide-derivatized polymer conjugate systems; and (4) polymers containing polysaccharide-mimetic molecules. Each section will discuss relevant conjugation techniques, analysis, and the impact of these materials as micelles, particles, or hydrogels used in in-vitro and in-vivo biomaterial applications. PMID:20091875

  2. Halo scale predictions of symmetron modified gravity

    SciTech Connect

    Clampitt, Joseph; Jain, Bhuvnesh; Khoury, Justin E-mail: bjain@physics.upenn.edu

    2012-01-01

    We offer predictions of symmetron modified gravity in the neighborhood of realistic dark matter halos. The predictions for the fifth force are obtained by solving the nonlinear symmetron equation of motion in the spherical NFW approximation. In addition, we compare the three major known screening mechanisms: Vainshtein, Chameleon, and Symmetron around such dark matter halos, emphasizing the significant differences between them and highlighting observational tests which exploit these differences. Finally, we demonstrate the host halo environmental screening effect (''blanket screening'') on smaller satellite halos by solving for the modified forces around a density profile which is the sum of satellite and approximate host components.

  3. Magnetically modified microalgae and their applications.

    PubMed

    Safarik, Ivo; Prochazkova, Gita; Pospiskova, Kristyna; Branyik, Tomas

    2016-10-01

    The majority of algal cells can interact with a wide range of nano- and microparticles. Upon interaction the modified cells usually maintain their viability and the presence of foreign material on their surfaces or in protoplasm can provide additional functionalities. Magnetic modification and labeling of microalgal biomass ensures a wide spectrum of biotechnological, bioanalytical and environmental applications. Different aspects of microalgal cell magnetic modification are covered in the review, followed by successful applications of magnetic algae. Modified cells can be employed during their harvesting and removal, applied in toxicity microscreening devices and also as efficient adsorbents of different types of xenobiotics.

  4. Modified Coaxial Probe Feeds for Layered Antennas

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W.; Chu, Andrew W.; Dobbins, Justin A.; Lin, Greg Y.

    2006-01-01

    In a modified configuration of a coaxial probe feed for a layered printed-circuit antenna (e.g., a microstrip antenna), the outer conductor of the coaxial cable extends through the thickness of at least one dielectric layer and is connected to both the ground-plane conductor and a radiator-plane conductor. This modified configuration simplifies the incorporation of such radio-frequency integrated circuits as power dividers, filters, and low-noise amplifiers. It also simplifies the design and fabrication of stacked antennas with aperture feeds.

  5. Probe studies in a modified penning discharge

    NASA Technical Reports Server (NTRS)

    Sen, C.

    1976-01-01

    The axial and radial floating potential distribution in a modified Penning discharge were studied at different values of the background pressure, discharge voltage, and magnetic field. An array of small disc probes arranged radially with their planes perpendicular to the magnetic field and movable along the axial direction was inserted in the plasma through one open end of the magnetic mirror system. Results show that depending on the operating conditions, the discharge can undergo different mode transitions in which the plasma can sustain different floating potentials in the radial as well as in the axial directions. Preliminary results of measurement, using RF probes in the modified Penning discharge plasma are also discussed.

  6. [Risk assessment of genetically modified organisms].

    PubMed

    Costa, Thadeu Estevam Moreira Maramaldo; Dias, Aline Peçanha Muzy; Scheidegger, Erica Miranda Damasio; Marin, Victor Augustus

    2011-01-01

    Since the commercial approve in 1996, the global area of transgenic crops has raised more than 50 times. In the last two decades, governments have been planning strategies and protocols for safety assessment of food and feed genetically modified (GM). Evaluation of food safety should be taken on a case-by-case analysis depending on the specific traits of the modified crops and the changes introduced by the genetic modification, using for this the concept of substantial equivalence. This work presents approaches for the risk assessment of GM food, as well as some problems related with the genetic construction or even with the expression of the inserted gene.

  7. Modified Landweber algorithm for robust particle sizing by using Fraunhofer diffraction.

    PubMed

    Xu, Lijun; Wei, Tianxiao; Zhou, Jiayi; Cao, Zhang

    2014-09-20

    In this paper, a robust modified Landweber algorithm was proposed to retrieve the particle size distributions from Fraunhofer diffraction. Three typical particle size distributions, i.e., Rosin-Rammler, lognormal, and bimodal normal distributions for particles ranging from 4.8 to 96 μm, were employed to verify the performance of the algorithm. To show its merits, the proposed algorithm was compared with the Tikhonov regularization algorithm and the ℓ1-norm-based algorithm. Simulation results showed that, for noise-free data, both the modified Landweber algorithm and the ℓ1-norm-based algorithm were better than the Tikhonov regularization algorithm in terms of accuracy. When the data was noise-contaminated, the modified Landweber algorithm was superior to the other two algorithms in both accuracy and speed. An experimental setup was also established and the results validated the feasibility and effectiveness of the proposed method.

  8. Failure Behavior Characterization of Mo-Modified Ti Surface by Impact Test and Finite Element Analysis

    NASA Astrophysics Data System (ADS)

    Ma, Yong; Qin, Jianfeng; Zhang, Xiangyu; Lin, Naiming; Huang, Xiaobo; Tang, Bin

    2015-07-01

    Using the impact test and finite element simulation, the failure behavior of the Mo-modified layer on pure Ti was investigated. In the impact test, four loads of 100, 300, 500, and 700 N and 104 impacts were adopted. The three-dimensional residual impact dents were examined using an optical microscope (Olympus-DSX500i), indicating that the impact resistance of the Ti surface was improved. Two failure modes cohesive and wearing were elucidated by electron backscatter diffraction and energy-dispersive spectrometer performed in a field-emission scanning electron microscope. Through finite element forward analysis performed at a typical impact load of 300 N, stress-strain distributions in the Mo-modified Ti were quantitatively determined. In addition, the failure behavior of the Mo-modified layer was determined and an ideal failure model was proposed for high-load impact, based on the experimental and finite element forward analysis results.

  9. A Modified 8 f Geometry with Reduced Optical Aberrations for Improved Time Domain Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Laurita, N. J.; Cheng, Bing; Barkhouser, R.; Neumann, V. A.; Armitage, N. P.

    2016-09-01

    We present a modified 8 f geometry for time domain terahertz (THz) spectroscopy (TDTS) experiments. We show, through simulations and data, that a simple rearranging of the off-axis parabolic mirrors, which are typically used to focus and direct THz radiation in TDTS experiments, results in a nearly 40 % reduction in the THz focal spot diameter. This effect stems from significant reduction of the principle optical aberrations which are enhanced in the conventional 8 f geometry but partially compensated in the modified 8 f experimental setup. We compare data from our home-built TDTS spectrometer in the modified 8 f geometry to that of previous iterations that were designed in the conventional 8 f geometry to demonstrate the effect.

  10. The analysis of MHD blood flows through porous arteries using a locally modified homogenous nanofluids model.

    PubMed

    Akbarzadeh, Pooria

    2016-05-12

    In this paper, magneto-hydrodynamic blood flows through porous arteries are numerically simulated using a locally modified homogenous nanofluids model. Blood is taken into account as the third-grade non-Newtonian fluid containing nanoparticles. In the modified nanofluids model, the viscosity, density, and thermal conductivity of the solid-liquid mixture (nanofluids) which are commonly utilized as an effective value, are locally combined with the prevalent single-phase model. The modified governing equations are solved numerically using Newton's method and a block tridiagonal matrix solver. The results are compared to the prevalent nanofluids single-phase model. In addition, the efficacies of important physical parameters such as pressure gradient, Brownian motion parameter, thermophoresis parameter, magnetic-field parameter, porosity parameter, and etc. on temperature, velocity and nanoparticles concentration profiles are examined.

  11. The analysis of MHD blood flows through porous arteries using a locally modified homogenous nanofluids model.

    PubMed

    Akbarzadeh, Pooria

    2016-05-12

    In this paper, magneto-hydrodynamic blood flows through porous arteries are numerically simulated using a locally modified homogenous nanofluids model. Blood is taken into account as the third-grade non-Newtonian fluid containing nanoparticles. In the modified nanofluids model, the viscosity, density, and thermal conductivity of the solid-liquid mixture (nanofluids) which are commonly utilized as an effective value, are locally combined with the prevalent single-phase model. The modified governing equations are solved numerically using Newton's method and a block tridiagonal matrix solver. The results are compared to the prevalent nanofluids single-phase model. In addition, the efficacies of important physical parameters such as pressure gradient, Brownian motion parameter, thermophoresis parameter, magnetic-field parameter, porosity parameter, and etc. on temperature, velocity and nanoparticles concentration profiles are examined. PMID:27175464

  12. Modified convolution method to reconstruct particle hologram with an elliptical Gaussian beam illumination.

    PubMed

    Wu, Xuecheng; Wu, Yingchun; Yang, Jing; Wang, Zhihua; Zhou, Binwu; Gréhan, Gérard; Cen, Kefa

    2013-05-20

    Application of the modified convolution method to reconstruct digital inline holography of particle illuminated by an elliptical Gaussian beam is investigated. Based on the analysis on the formation of particle hologram using the Collins formula, the convolution method is modified to compensate the astigmatism by adding two scaling factors. Both simulated and experimental holograms of transparent droplets and opaque particles are used to test the algorithm, and the reconstructed images are compared with that using FRFT reconstruction. Results show that the modified convolution method can accurately reconstruct the particle image. This method has an advantage that the reconstructed images in different depth positions have the same size and resolution with the hologram. This work shows that digital inline holography has great potential in particle diagnostics in curvature containers.

  13. Malingering or simulation in ophthalmology-visual acuity

    PubMed Central

    Incesu, Ali Ihsan; Sobacı, Güngör

    2011-01-01

    Simulation can be defined as malingering, or sometimes functional visual loss (FVL). It manifests as either simulating an ophthalmic disease (positive simulation), or denial of ophthalmic disease (negative simulation). Conscious behavior and compensation or indemnity claims are prominent features of simulation. Since some authors suggest that this is a manifestation of underlying psychopathology, even conversion is included in this context. In today's world, every ophthalmologist can face with simulation of ophthalmic disease or disorder. In case of simulation suspect, the physician's responsibility is to prove the simulation considering the disease/disorder first, and simulation as an exclusion. In simulation examinations, the physician should be firm and smart to select appropriate test(s) to convince not only the subject, but also the judge in case of indemnity or compensation trials. Almost all ophthalmic sensory and motor functions including visual acuity, visual field, color vision and night vision can be the subject of simulation. Examiner must be skillful in selecting the most appropriate test. Apart from those in the literature, we included all kinds of simulation in ophthalmology. In addition, simulation examination techniques, such as, use of OCT (optical coherence tomography), frequency doubling perimetry (FDP), and modified polarization tests were also included. In this review, we made a thorough literature search, and added our experiences to give the readers up-to-date information on malingering or simulation in ophthalmology. PMID:22553721

  14. Galactic Cosmic Ray Simulation at the NASA Space Radiation Laboratory

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Slaba, Tony C.; Rusek, Adam

    2015-01-01

    The external Galactic Cosmic Ray (GCR) spectrum is significantly modified when it passes through spacecraft shielding and astronauts. One approach for simulating the GCR space radiation environment at ground based accelerators would use the modified spectrum, rather than the external spectrum, in the accelerator beams impinging on biological targets. Two recent workshops have studied such GCR simulation. The first workshop was held at NASA Langley Research Center in October 2014. The second workshop was held at the NASA Space Radiation Investigators' workshop in Galveston, Texas in January 2015. The results of these workshops will be discussed in this paper.

  15. Process to Produce Iron Nanoparticle Lunar Dust Simulant Composite

    NASA Technical Reports Server (NTRS)

    Hung, Ching-cheh; McNatt, Jeremiah

    2010-01-01

    A document discusses a method for producing nanophase iron lunar dust composite simulant by heating a mixture of carbon black and current lunar simulant types (mixed oxide including iron oxide) at a high temperature to reduce ionic iron into elemental iron. The product is a chemically modified lunar simulant that can be attracted by a magnet, and has a surface layer with an iron concentration that is increased during the reaction. The iron was found to be -iron and Fe3O4 nanoparticles. The simulant produced with this method contains iron nanoparticles not available previously, and they are stable in ambient air. These nanoparticles can be mass-produced simply.

  16. DELightcurveSimulation: Light curve simulation code

    NASA Astrophysics Data System (ADS)

    Connolly, Samuel D.

    2016-02-01

    DELightcurveSimulation simulates light curves with any given power spectral density and any probability density function, following the algorithm described in Emmanoulopoulos et al. (2013). The simulated products have exactly the same variability and statistical properties as the observed light curves. The code is a Python implementation of the Mathematica code provided by Emmanoulopoulos et al.

  17. Modifying Poisson equation for near-solute dielectric polarization and solvation free energy

    NASA Astrophysics Data System (ADS)

    Yang, Pei-Kun

    2016-06-01

    The dielectric polarization P is important for calculating the stability of protein conformation and the binding affinity of protein-protein/ligand interactions and for exploring the nonthermal effect of an external electric field on biomolecules. P was decomposed into the product of the electric dipole moment per molecule p; bulk solvent density Nbulk; and relative solvent molecular density g. For a molecular solute, 4πr2p(r) oscillates with the distance r to the solute, and g(r) has a large peak in the near-solute region, as observed in molecular dynamics (MD) simulations. Herein, the Poisson equation was modified for computing p based on the modified Gauss's law of Maxwell's equations, and the potential of the mean force was used for computing g. For one or two charged atoms in a water cluster, the solvation free energies of the solutes obtained by these equations were similar to those obtained from MD simulations.

  18. Corrosive characteristics of surface-modified stainless steel bipolar plate in solid polymer fuel cell

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowen; Wang, Lixia; Sun, Juncai

    2015-03-01

    In this paper, corrosion behavior of an AISI 304 stainless steel modified by niobium or niobium nitride (denoted as niobized 304 SS and Nb-N 304 SS, respectively) is investigated in simulated solid polymer fuel cell (SPFC) operating conditions. Potentiodynamic polarizations show that the corrosion potentials of surface modified 304 SS shift to positive direction while the corrosion current densities decrease greatly comparing with the bare 304 SS in simulated anodic SPFC environments. The order of corrosive resistance in corrosive potential, corrosive current density and pitting potential is: Nb-N 304 SS > niobized 304 SS > bare 304 SS. In the methanol-fueled SPFC operating conditions, the results show that the corrosion resistance of bare and niobized 304 SS increases with the methanol concentration increasing in the test solutions.

  19. 21 CFR 177.1600 - Polyethylene resins, carboxyl modified.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Polyethylene resins, carboxyl modified. 177.1600..., carboxyl modified. Carboxyl-modified polyethylene resins may be safely used as the food-contact surface of...) For the purpose of this section, carboxyl-modified polyethylene resins consist of basic...

  20. 21 CFR 177.1600 - Polyethylene resins, carboxyl modified.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Polyethylene resins, carboxyl modified. 177.1600..., carboxyl modified. Carboxyl-modified polyethylene resins may be safely used as the food-contact surface of...) For the purpose of this section, carboxyl-modified polyethylene resins consist of basic...

  1. 21 CFR 177.1600 - Polyethylene resins, carboxyl modified.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Polyethylene resins, carboxyl modified. 177.1600... Use Food Contact Surfaces § 177.1600 Polyethylene resins, carboxyl modified. Carboxyl-modified... paragraph (b) of this section are not applicable to carboxyl-modified polyethylene resins used in...

  2. 21 CFR 178.3520 - Industrial starch-modified.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Industrial starch-modified. 178.3520 Section 178... § 178.3520 Industrial starch-modified. Industrial starch-modified may be safely used as a component of..., transporting, or holding food, subject to the provisions of this section. (a) Industrial starch-modified...

  3. Evolving targets for lipid-modifying therapy

    PubMed Central

    Do, Rose Q; Nicholls, Stephen J; Schwartz, Gregory G

    2014-01-01

    The pathogenesis and progression of atherosclerosis are integrally connected to the concentration and function of lipoproteins in various classes. This review examines existing and emerging approaches to modify low-density lipoprotein and lipoprotein (a), triglyceride-rich lipoproteins, and high-density lipoproteins, emphasizing approaches that have progressed to clinical evaluation. Targeting of nuclear receptors and phospholipases is also discussed. PMID:25172365

  4. Modified host cells with efflux pumps

    DOEpatents

    Dunlop, Mary J.; Keasling, Jay D.; Mukhopadhyay, Aindrila

    2016-08-30

    The present invention provides for a modified host cell comprising a heterologous expression of an efflux pump capable of transporting an organic molecule out of the host cell wherein the organic molecule at a sufficiently high concentration reduces the growth rate of or is lethal to the host cell.

  5. Modified Video Course Methodology for Distance Learning.

    ERIC Educational Resources Information Center

    Springer, Stephen B.

    In recent years, colleges have made extensive efforts to provide distance learning opportunities for adult students. At Southwest Texas State University, a required course in the Occupational Education program has been delivered in a modified video format. The video was made of an actual class being taught in a production studio. The main…

  6. Torsion Modified Plasma Screening in Astrophysics

    NASA Astrophysics Data System (ADS)

    Sivaram, C.; Garcia de Andrade, L. C.

    The torsion modified Maxwell-Proca equations when applied to describe a plasma is shown to lead to a correction to the Debye screening length. For hot new born neutron stars the torsion correction is shown to be significant. This effect may provide an indirect evidence for torsion.

  7. Modified triglyceride oil through reactions with phenyltriazolinedione

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The synthesis of a modified triglyceride oil was achieved through the reactions with 4-phenyl-1,2-4-triazoline-3,5-dione (PTAD). 1H NMR was used for structure determination and to monitor the reactions. Several reaction products were produced, and their relative yields depended on the stoichiometry ...

  8. Modified intraoral film holders for postmortem identification.

    PubMed

    Oeschger, M P; Hubar, J S

    1999-07-01

    To date there have not been any commercial dental X-ray film holders marketed to accommodate the special needs of forensic odontologists. Modification of standard Rinn XCP film holders by the investigators produced self-supporting film holders that do not require the active participation from the examinee. The modified film holders greatly simplify the operator's technique of exposing dental radiographs on cadavers.

  9. [Genetically modified food--unnecessary controversy?].

    PubMed

    Tchórz, Michał; Radoniewicz-Chagowska, Anna; Lewandowska-Stanek, Hanna; Szponar, Elzbieta; Szponar, Jarosław

    2012-01-01

    Fast development of genetic engineering and biotechnology allows use of genetically modified organisms (GMO) more and more in different branches of science and economy. Every year we can see an increase of food amount produced with the use of modification of genetic material. In our supermarkets we can find brand new types of plants, products including genetically modified ingredients or meat from animals fed with food containing GMO. This article presents general information about genetically modified organisms, it also explains the range of genetic manipulation, use of newly developed products and current field area for GMO in the world. Based on scientific data the article presents benefits from development of biotechnology in reference to modified food. It also presents the voice of skeptics who are extremely concerned about the impact of those organisms on human health and natural environment. Problems that appear or can appear as a result of an increase of GMO are very important not only from a toxicologist's or a doctor's point of view but first of all from the point of view of ordinary consumers--all of us.

  10. Cavitation in block copolymer modified epoxy

    NASA Astrophysics Data System (ADS)

    Declet-Perez, Carmelo; Francis, Lorraine; Bates, Frank

    2013-03-01

    Today, brittleness in epoxy networks limits most commercial applications. Significant toughness can be imparted by adding small amounts of micelle forming block copolymers (BCP) without compromising critical properties such as high use temperature and modulus. Curing the network locks in the self-assembled BCP micellar structures formed in the monomer resin providing control of the resulting morphology. Despite significant research over the last decade, a complete description of the parameters influencing toughness in block copolymer modified epoxies is still lacking. In this presentation we compare the ultimate mechanical behavior of epoxies modified with spherical micelle forming BCP's containing rubbery and glassy cores using real-time in-situ small-angle X-ray scattering (SAXS) performed during tensile deformation. Striking differences in the 2D SAXS patterns were documented for epoxies modified with rubbery (PEP) versus glassy (PS) micelle cores. Rubbery cores dilate by 100% in volume upon specimen yielding, while the glassy micelle cores deform at approximately constant volume. These results provide direct evidence of a cavitation mediated mechanism for toughness in block copolymer modified epoxies. We further interpret characteristic butterfly features in the 2D SAXS patterns in terms of epoxy network deformation. Support was provided by the NSF sponsored MRSEC at the University of Minnesota

  11. Generalization of a Modified Food Preference.

    ERIC Educational Resources Information Center

    Birch, Leann Lipps

    1981-01-01

    Assesses preschool children's preferences for eight snack foods and tests procedures to modify preferences for certain foods by having children sort foods according to self-determined categories. Enhanced preferences for target foods generalized to other foods in the same category only for children using semantic sorting categories. (Author/DB)

  12. Genetically Modified Plants: Public and Scientific Perceptions

    PubMed Central

    2013-01-01

    The potential of genetically modified plants to meet the requirements of growing population is not being recognized at present. This is a consequence of concerns raised by the public and the critics about their applications and release into the environment. These include effect on human health and environment, biosafety, world trade monopolies, trustworthiness of public institutions, integrity of regulatory agencies, loss of individual choice, and ethics as well as skepticism about the real potential of the genetically modified plants, and so on. Such concerns are enormous and prevalent even today. However, it should be acknowledged that most of them are not specific for genetically modified plants, and the public should not forget that the conventionally bred plants consumed by them are also associated with similar risks where no information about the gene(s) transfer is available. Moreover, most of the concerns are hypothetical and lack scientific background. Though a few concerns are still to be disproved, it is viewed that, with proper management, these genetically modified plants have immense potential for the betterment of mankind. In the present paper, an overview of the raised concerns and wherever possible reasons assigned to explain their intensity or unsuitability are reviewed. PMID:25937981

  13. Zirconium modified nickel-copper alloy

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D. (Inventor)

    1977-01-01

    An improved material for use in a catalytic reactor which reduces nitrogen oxide from internal combustion engines is in the form of a zirconium-modified, precipitation-strengthened nickel-copper alloy. This material has a nominal composition of Ni-30 Cu-0.2 Zr and is characterized by improved high temperature mechanical properties.

  14. MATCON MODIFIED ASPHALT COVER CONTAINMENT SYSTEM DEMONSTRATION

    EPA Science Inventory

    In order to make improvements to conventional paving asphalt to make it more suitable for containment applications, Wilder Construction Co. of Everett, WA offers MatCon, a polymer modified asphalt system comprised of proprietary binder, when coupled with a selected aggregate type...

  15. Solving Differential Equations Using Modified Picard Iteration

    ERIC Educational Resources Information Center

    Robin, W. A.

    2010-01-01

    Many classes of differential equations are shown to be open to solution through a method involving a combination of a direct integration approach with suitably modified Picard iterative procedures. The classes of differential equations considered include typical initial value, boundary value and eigenvalue problems arising in physics and…

  16. How Landscape Plants Modify the Environment.

    ERIC Educational Resources Information Center

    Blankenship, Sylvia; Wise, Kevin

    1993-01-01

    Presents three experiments that provide examples of how plants modify their surroundings and create microenvironments. Examples demonstrate (1) how types of ground cover influence water quality; (2) how plants can create a thermal microenvironment; and (3) how plants can serve as barriers to wind. (MDH)

  17. Modified fire-resistant foams forseat cushions

    NASA Technical Reports Server (NTRS)

    Gagliani, J.; Lee, R.; Sorathia, U. A. K.; Wilcoxson, A. L.

    1981-01-01

    Modified polyimide-polymer resins are precursors for new family of resilient fire-resistant foams. Terpolyimide foams containing long-chain aliphatic diamines withstand 50,000 cycles of compression over a 200 pound load - an equivalent of 3 years of continuous use as seat cushion filler.

  18. Testing for Genetically Modified Foods Using PCR

    ERIC Educational Resources Information Center

    Taylor, Ann; Sajan, Samin

    2005-01-01

    The polymerase chain reaction (PCR) is a Nobel Prize-winning technique that amplifies a specific segment of DNA and is commonly used to test for the presence of genetic modifications. Students use PCR to test corn meal and corn-muffin mixes for the presence of a promoter commonly used in genetically modified foods, the cauliflower mosaic virus 35S…

  19. Genetically modified pig models for neurodegenerative disorders.

    PubMed

    Holm, Ida E; Alstrup, Aage Kristian Olsen; Luo, Yonglun

    2016-01-01

    Increasing incidence of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease has become one of the most challenging health issues in ageing humans. One approach to combat this is to generate genetically modified animal models of neurodegenerative disorders for studying pathogenesis, prognosis, diagnosis, treatment, and prevention. Owing to the genetic, anatomic, physiologic, pathologic, and neurologic similarities between pigs and humans, genetically modified pig models of neurodegenerative disorders have been attractive large animal models to bridge the gap of preclinical investigations between rodents and humans. In this review, we provide a neuroanatomical overview in pigs and summarize and discuss the generation of genetically modified pig models of neurodegenerative disorders including Alzheimer's diseases, Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, spinal muscular atrophy, and ataxia-telangiectasia. We also highlight how non-invasive bioimaging technologies such as positron emission tomography (PET), computer tomography (CT), and magnetic resonance imaging (MRI), and behavioural testing have been applied to characterize neurodegenerative pig models. We further propose a multiplex genome editing and preterm recloning (MAP) approach by using the rapid growth of the ground-breaking precision genome editing technology CRISPR/Cas9 and somatic cell nuclear transfer (SCNT). With this approach, we hope to shorten the temporal requirement in generating multiple transgenic pigs, increase the survival rate of founder pigs, and generate genetically modified pigs that will more closely resemble the disease-causing mutations and recapitulate pathological features of human conditions. PMID:26446984

  20. 49 CFR 595.6 - Modifier identification.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... that modifies a motor vehicle to enable a person with a disability to operate, or ride as a passenger in, the motor vehicle and intends to avail itself of the exemption provided in 49 CFR 595.7 shall... as a passenger in, the motor vehicle and intends to avail itself of the exemption provided in 49...