Science.gov

Sample records for modified redfield simulations

  1. Ultrafast energy transfer with competing channels: Non-equilibrium Förster and Modified Redfield theories.

    PubMed

    Seibt, Joachim; Mančal, Tomáš

    2017-05-07

    We derive equations of motion for the reduced density matrix of a molecular system which undergoes energy transfer dynamics competing with fast internal conversion channels. Environmental degrees of freedom of such a system have no time to relax to quasi-equilibrium in the electronic excited state of the donor molecule, and thus the conditions of validity of Förster and Modified Redfield theories in their standard formulations do not apply. We derive non-equilibrium versions of the two well-known rate theories and apply them to the case of carotenoid-chlorophyll energy transfer. Although our reduced density matrix approach does not account for the formation of vibronic excitons, it still confirms the important role of the donor ground-state vibrational states in establishing the resonance energy transfer conditions. We show that it is essential to work with a theory valid in a strong system-bath interaction regime to obtain correct dependence of the rates on donor-acceptor energy gap.

  2. Excitation dynamics in Phycoerythrin 545: modeling of steady-state spectra and transient absorption with modified Redfield theory.

    PubMed

    Novoderezhkin, Vladimir I; Doust, Alexander B; Curutchet, Carles; Scholes, Gregory D; van Grondelle, Rienk

    2010-07-21

    We model the spectra and excitation dynamics in the phycobiliprotein antenna complex PE545 isolated from the unicellular photosynthetic cryptophyte algae Rhodomonas CS24. The excitonic couplings between the eight bilins are calculated using the CIS/6-31G method. The site energies are extracted from a simultaneous fit of the absorption, circular dichroism, fluorescence, and excitation anisotropy spectra together with the transient absorption kinetics using the modified Redfield approach. Quantitative fit of the data enables us to assign the eight exciton components of the spectra and build up the energy transfer picture including pathways and timescales of energy relaxation, thus allowing a visualization of excitation dynamics within the complex.

  3. Redfield Energy Approval

    EPA Pesticide Factsheets

    This September 19, 2016 letter from EPA approves the petition from Poet Biorefining-Lake Crystal, regarding non-This October 27, 2016 letter from EPA approves the petition from Redfield Energy, LLC, regarding non-grandfathered ethanol produced

  4. Ecological modelling in a sea of variable stoichiometry: Dysfunctionality and the legacy of Redfield and Monod

    NASA Astrophysics Data System (ADS)

    Flynn, Kevin J.

    2010-01-01

    Traditionally models of oceanic pelagic ecology, which also lay at the heart of general circulation models used for climate change simulations and of models describing coastal ecosystem dynamics have employed descriptions of plankton that assume fixed Redfield elemental compositions as inputs for rectangular-hyperbolic (Monod-type, Holling type II) descriptions of resource-limited growth and predation kinetics. The performances of Redfield-Monod and variable stoichiometric models are compared with theoretical expectations and experimental data for descriptions of multi-nutrient limited phytoplankton growth and predator-prey interactions. Serious deficiencies are revealed in Redfield-Monod implementations; such constructs have outputs and/or structural logic contrary to empirical biological knowledge. For example, Redfield-Monod models often employ nutrient limitation as a significant factor controlling phytoplankton growth, and yet biologically such nutrient limitation is associated with significant variation in elemental stoichiometry. One could argue that reliance on such dysfunctional descriptions is unacceptable, especially in an era when increasing political play is made of model simulations and predictions. Biological studies should examine the consumption and fate of all major nutrients, not just of the limiting nutrient, in order to furnish modellers with the mechanistic understanding, and data, to enable a refined description of the organisms responsible for biogeochemical cycling. Modellers, in turn, should embrace existing experimental and phenomenological observations and update their models accordingly. Simplifications in model structure can then be made from a sound knowledge base rather than by making potentially incorrect a priori assumptions.

  5. Redfield ratios along isopycnal surfaces—a complementary study

    NASA Astrophysics Data System (ADS)

    Minster, Jean-François; Boulahdid, Mostefa

    1987-12-01

    The recent suggestion by TAKAHASHIet al. (1985, Journal of Geophysical Research, 90, 6907-6924) to change the Redfield ratios from P/N/O 2 = 1/18/138 to 1/17/172 is critically examined. As a complementary analysis we process the GEOSECS and TTO data in the Atlantic and Indian oceans along four isopycnal horizons. This is done separately for each basin in order to diminish the possible effects of diapycnal mixing. The occurrence of two or three end-member mixing is assessed through "NO" vs salinity plots. End-members are selected among stations at the geographical border of the basins. The Redfield ratios are calculated in a two or three end-member mixing and consumption model via a direct non-linear least-squares technique. The N/O 2 Redfield ratio appears constant and equal to 9.1 ± 0.4. For P/O 2, we confirm the Takahashi et al. value for στ = 27.0 and 27.2%. For στ = 27.4%, we find a ratio of 1/141 and for στ = 27.8%, a value of 1/115. This change is related to the nitrate to phosphate ratio. These results suggest that phosphorus is less easily remobilized, or more strongly recycled in shallow levels, than nitrogen.

  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. Systematic simulations of modified gravity: chameleon 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

    2013-04-01

    In this work we systematically study the linear and nonlinear structure formation in chameleon theories of modified gravity, using a generic parameterisation which describes a large class of models using only 4 parameters. For this we have modified the N-body simulation code ecosmog to perform a total of 65 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a significant 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 paradigm cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc{sup −1}, since the latter incorrectly assumes that the modification of gravity depends only on the background matter density. Our results show that the chameleon screening mechanism is significantly more efficient than other mechanisms such as the dilaton and symmetron, especially in high-density regions and at early times, and can serve as a guidance to determine the parts of the chameleon parameter space which are cosmologically interesting and thus merit further studies in the future.

  8. Ecological Stoichiometry beyond Redfield: An Ionomic Perspective on Elemental Homeostasis.

    PubMed

    Jeyasingh, Punidan D; Goos, Jared M; Thompson, Seth K; Godwin, Casey M; Cotner, James B

    2017-01-01

    Elemental homeostasis has been largely characterized using three important elements that were part of the Redfield ratio (i.e., carbon: nitrogen: phosphorus). These efforts have revealed substantial diversity in homeostasis among taxonomic groups and even within populations. Understanding the evolutionary basis, and ecological consequences of such diversity is a central challenge. Here, we propose that a more complete understanding of homeostasis necessitates the consideration of other elements beyond C, N, and P. Specifically, we posit that physiological complexity underlying maintenance of elemental homeostasis along a single elemental axis impacts processing of other elements, thus altering elemental homeostasis along other axes. Indeed, transcriptomic studies in a wide variety of organisms have found that individuals differentially express significant proportions of the genome in response to variability in supply stoichiometry in order to maintain varying levels of homeostasis. We review the literature from the emergent field of ionomics that has established the consequences of such physiological trade-offs on the content of the entire suite of elements in an individual. Further, we present experimental data on bacteria exhibiting divergent phosphorus homeostasis phenotypes demonstrating the fundamental interconnectedness among elemental quotas. These observations suggest that physiological adjustments can lead to unexpected patterns in biomass stoichiometry, such as correlated changes among suites of non-limiting microelements in response to limitation by macroelements. Including the entire suite of elements that comprise biomass will foster improved quantitative understanding of the links between chemical cycles and the physiology of organisms.

  9. Ecological Stoichiometry beyond Redfield: An Ionomic Perspective on Elemental Homeostasis

    PubMed Central

    Jeyasingh, Punidan D.; Goos, Jared M.; Thompson, Seth K.; Godwin, Casey M.; Cotner, James B.

    2017-01-01

    Elemental homeostasis has been largely characterized using three important elements that were part of the Redfield ratio (i.e., carbon: nitrogen: phosphorus). These efforts have revealed substantial diversity in homeostasis among taxonomic groups and even within populations. Understanding the evolutionary basis, and ecological consequences of such diversity is a central challenge. Here, we propose that a more complete understanding of homeostasis necessitates the consideration of other elements beyond C, N, and P. Specifically, we posit that physiological complexity underlying maintenance of elemental homeostasis along a single elemental axis impacts processing of other elements, thus altering elemental homeostasis along other axes. Indeed, transcriptomic studies in a wide variety of organisms have found that individuals differentially express significant proportions of the genome in response to variability in supply stoichiometry in order to maintain varying levels of homeostasis. We review the literature from the emergent field of ionomics that has established the consequences of such physiological trade-offs on the content of the entire suite of elements in an individual. Further, we present experimental data on bacteria exhibiting divergent phosphorus homeostasis phenotypes demonstrating the fundamental interconnectedness among elemental quotas. These observations suggest that physiological adjustments can lead to unexpected patterns in biomass stoichiometry, such as correlated changes among suites of non-limiting microelements in response to limitation by macroelements. Including the entire suite of elements that comprise biomass will foster improved quantitative understanding of the links between chemical cycles and the physiology of organisms. PMID:28487686

  10. Spectra and dynamics in the B800 antenna: comparing hierarchical equations, Redfield and Förster theories.

    PubMed

    Novoderezhkin, Vladimir; van Grondelle, Rienk

    2013-09-26

    We model the spectra (absorption and circular dichroism) and excitation dynamics in the B800 ring of the LH2 antenna complex from Rs. molischianum using different theoretical approaches, i.e., Förster theory, standard and modified versions of the Redfield theory, and the more versatile nonperturbative approach based on hierarchically coupled equations for the reduced density operator. We demonstrate that, although excitations in the B800 ring are localized due to disorder, thermal effects, and phonons, there are still sizable excitonic effects producing shift, narrowing, and asymmetry of the spectra. Moreover, the excitation dynamics reveals the presence of long-lived (up to 1 ps) non-oscillatory coherences between the exciton states maintained due to nonsecular population-to-coherence transfers. The sub-ps decay of the coherences is followed by slow motion of the excitation around the ring, producing equilibration of the site populations with a time constant of about 3-4 ps, which is slower than the B800 → B850 transfer. The exact solution obtained with the hierarchical equations is compared with other approaches, thus illustrating limitations of the Förster and Redfield pictures.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

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

    PubMed

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

    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.

  17. 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

  18. Quantum transport under ac drive from the leads: A Redfield quantum master equation approach

    NASA Astrophysics Data System (ADS)

    Purkayastha, Archak; Dubi, Yonatan

    2017-08-01

    Evaluating the time-dependent dynamics of driven open quantum systems is relevant for a theoretical description of many systems, including molecular junctions, quantum dots, cavity-QED experiments, cold atoms experiments, and more. Here, we formulate a rigorous microscopic theory of an out-of-equilibrium open quantum system of noninteracting particles on a lattice weakly coupled bilinearly to multiple baths and driven by periodically varying thermodynamic parameters like temperature and chemical potential of the bath. The particles can be either bosonic or fermionic and the lattice can be of any dimension and geometry. Based on the Redfield quantum master equation under Born-Markov approximation, we derive a linear differential equation for an equal time two point correlation matrix, sometimes also called a single-particle density matrix, from which various physical observables, for example, current, can be calculated. Various interesting physical effects, such as resonance, can be directly read off from the equations. Thus, our theory is quite general and gives quite transparent and easy-to-calculate results. We validate our theory by comparing with exact numerical simulations. We apply our method to a generic open quantum system, namely, a double quantum dot coupled to leads with modulating chemical potentials. The two most important experimentally relevant insights from this are as follows: (i) Time-dependent measurements of current for symmetric oscillating voltages (with zero instantaneous voltage bias) can point to the degree of asymmetry in the system-bath coupling and (ii) under certain conditions time-dependent currents can exceed time-averaged currents by several orders of magnitude, and can therefore be detected even when the average current is below the measurement threshold.

  19. Harmful algal blooms and eutrophication: "strategies" for nutrient uptake and growth outside the Redfield comfort zone

    NASA Astrophysics Data System (ADS)

    Glibert, Patricia M.; Burkholder, Joann M.

    2011-07-01

    While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.

  20. 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.

  1. Non-Redfield carbon and nitrogen cycling in the Arctic: Effects of ecosystem structure and dynamics

    NASA Astrophysics Data System (ADS)

    Daly, Kendra L.; Wallace, Douglas W. R.; Smith, Walker O.; Skoog, Annelie; Lara, RubéN.; Gosselin, Michel; Falck, Eva; Yager, Patricia L.

    1999-02-01

    The C:N ratio is a critical parameter used in both global ocean carbon models and field studies to understand carbon and nutrient cycling as well as to estimate exported carbon from the euphotic zone. The so-called Redfield ratio (C:N = 6.6 by atoms) [Redfield et al., 1963] is widely used for such calculations. Here we present data from the NE Greenland continental shelf that show that most of the C:N ratios for particulate (autotrophic and heterotrophic) and dissolved pools and rates of transformation among them exceed Redfield proportions from June to August, owing to species composition, size, and biological interactions. The ecosystem components that likely comprised sinking particles and had relatively high C:N ratios (geometric means) included (1) the particulate organic matter (C:N = 8.9) dominated by nutrient-deficient diatoms, resulting from low initial nitrate concentrations (approximately 4 μM) in Arctic surface waters; (2) the dominant zooplankton, herbivorous copepods (C:N = 9.6), having lipid storage typical of Arctic copepods; and (3) copepod fecal pellets (C:N = 33.2). Relatively high dissolved organic carbon concentrations (median 105 μM) were approximately 25 to 45 μM higher than reported for other systems and may be broadly characteristic of Arctic waters. A carbon-rich dissolved organic carbon pool also was generated during summer. Since the magnitude of carbon and nitrogen uncoupling in the surface mixed layer appeared to be greater than in other regions and occurred throughout the productive season, the C:N ratio of particulate organic matter may be a better conversion factor than the Redfield ratio to estimate carbon export for broad application in northern high-latitude systems.

  2. Modified Numerical Simulation Model of Blood Flow in Bend

    PubMed Central

    Liu, X; Zhou, X; Hao, X; Sang, X

    2015-01-01

    ABSTRACT The numerical simulation model of blood flow in bend is studied in this paper. The curvature modification is conducted for the blood flow model in bend to obtain the modified blood flow model in bend. The modified model is verified by U tube. By comparing the simulation results with the experimental results obtained by measuring the flow data in U tube, it was found that the modified blood flow model in bend can effectively improve the prediction accuracy of blood flow data affected by the curvature effect. PMID:27398727

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Molecular dynamics simulation of wetting on modified amorphous silica surface

    NASA Astrophysics Data System (ADS)

    Chai, Jingchun; Liu, Shuyan; Yang, Xiaoning

    2009-08-01

    The microscopic wetting of water on amorphous silica surfaces has been investigated by molecular dynamics simulation. Different degrees of surface hydroxylation/silanization were considered. It was observed that the hydrophobicity becomes enhanced with an increase in the degree of surface silanization. A continuous transformation from hydrophilicity to hydrophobicity can be attained for the amorphous silica surfaces through surface modification. From the simulation result, the contact angle can exceed 90° when surface silanization percentage is above 50%, showing a hydrophobic character. It is also found that when the percentage of surface silanization is above 70% on the amorphous silica surface, the water contact angle almost remains unchanged (110-120°). This phenomenon is a little different from the wetting behavior on smooth quartz plates in previous experimental report. This change in the wettability on modified amorphous silica surfaces can be interpreted in terms of the interaction between water molecules and the silica surfaces.

  9. ECOSMOG: an Efficient COde for Simulating MOdified Gravity

    NASA Astrophysics Data System (ADS)

    Li, Baojiu; Zhao, Gong-Bo; Teyssier, Romain; Koyama, Kazuya

    2012-01-01

    We introduce a new code, ECOSMOG, to run N-body simulations for a wide class of modified gravity and dynamical dark energy theories. These theories generally have one or more new dynamical degrees of freedom, the dynamics of which are governed by their (usually rather nonlinear) equations of motion. Solving these non-linear equations has been a great challenge in cosmology. Our code is based on the RAMSES code, which solves the Poisson equation on adaptively refined meshes to gain high resolutions in the high-density regions. We have added a solver for the extra degree(s) of freedom and performed numerous tests for the f(R) gravity model as an example to show its reliability. We find that much higher efficiency could be achieved compared with other existing mesh/grid-based codes thanks to two new features of the present code: (1) the efficient parallelisation and (2) the usage of the multigrid relaxation to solve the extra equation(s) on both the regular domain grid and refinements, giving much faster convergence even under much more stringent convergence criteria. This code is designed for performing high-accuracy, high-resolution and large-volume cosmological simulations for modified gravity and general dark energy theories, which can be utilised to test gravity and the dark energy hypothesis using the upcoming and future deep and high-resolution galaxy surveys.

  10. Monte Carlo simulation and dosimetric verification of radiotherapy beam modifiers

    NASA Astrophysics Data System (ADS)

    Spezi, E.; Lewis, D. G.; Smith, C. W.

    2001-11-01

    Monte Carlo simulation of beam modifiers such as physical wedges and compensating filters has been performed with a rectilinear voxel geometry module. A modified version of the EGS4/DOSXYZ code has been developed for this purpose. The new implementations have been validated against the BEAM Monte Carlo code using its standard component modules (CMs) in several geometrical conditions. No significant disagreements were found within the statistical errors of 0.5% for photons and 2% for electrons. The clinical applicability and flexibility of the new version of the code has been assessed through an extensive verification versus dosimetric data. Both Varian multi-leaf collimator (MLC) wedges and standard wedges have been simulated and compared against experiments for 6 MV photon beams and different field sizes. Good agreement was found between calculated and measured depth doses and lateral dose profiles along both wedged and unwedged directions for different depths and focus-to-surface distances. Furthermore, Monte Carlo-generated output factors for both open and wedged fields agreed with linac commissioning beam data within statistical uncertainties of the calculations (<3% at largest depths). Compensating filters of both low-density and high-density materials have also been successfully simulated. As a demonstration, a wax compensating filter with a complex three-dimensional concave and convex geometry has been modelled through a CT scan import. Calculated depth doses and lateral dose profiles for different field sizes agreed well with experiments. The code was used to investigate the performance of a commercial treatment planning system in designing compensators. Dose distributions in a heterogeneous water phantom emulating the head and neck region were calculated with the convolution-superposition method (pencil beam and collapsed cone implementations) and compared against those from the MC code developed herein. The new technique presented in this work is

  11. 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.

  12. Modified Lattice Boltzmann method for compressible fluid simulations

    SciTech Connect

    Hinton, F. L.; Rosenbluth, M. N.; Wong, S. K.; Lin-Liu, Y. R.; Miller, R. L.

    2001-06-01

    A modified lattice Boltzmann algorithm is shown to have much better stability to growing temperature perturbations, when compared with the standard lattice Boltzmann algorithm. The damping rates of long-wavelength waves, which determine stability, are derived using a collisional equilibrium distribution function which has the property that the Euler equations are obtained exactly in the limit of zero time step. Using this equilibrium distribution function, we show that our algorithm has inherent positive hyperviscosity and hyperdiffusivity, for very small values of viscosity and thermal diffusivity, which are lacking in the standard algorithm. Short-wavelength modes are shown to be stable for temperatures greater than a lower limit. Results from a computer code are used to compare these algorithms, and to confirm the damping rate predictions made analytically. Finite amplitude sound waves in the simulated fluid steepen, as expected from gas dynamic theory.

  13. Ocean's 16: Optimal protein:RNA ratio has near Redfield nitrogen:phosphorus ratio

    NASA Astrophysics Data System (ADS)

    Elser, J. J.; Loladze, I.

    2010-12-01

    One of the biosphere’s most intriguing patterns is the near equality of the atomic nitrogen:phosphorus ratio (N:P) found in waters throughout the deep ocean (~16) and its average in plankton in the upper ocean. When Redfield discovered this pattern 75 years ago, he suggested that it is driven by the cellular composition of plankton. However, no theoretical explanation for an N:P ~16 in microorganisms has ever been found. Moreover, recently it has been suggested that N:P ~16 may have no significance for either plankton nor for N/P cycling on geological time scales. Here we show that an N:P ratio of 16 emerges from fundamental biochemical and biomolecular properties: N in amino acids, N and P in nucleotides, and the square root of the ratio of the maximal translation and transcription rates. Our theoretical results are supported by a comprehensive compilation of literature data on microbial protein:rRNA ratios. Thus, the N:P ratio of ~16 appears to correspond to the biochemically optimal protein:RNA ratio for maximal growth rates for both prokaryotes and eukaryotes.

  14. Non-Redfield, nutrient synergy and flexible internal elemental stoichiometry in a marine bacterium

    PubMed Central

    Trautwein, Kathleen; Feenders, Christoph; Hulsch, Reiner; Ruppersberg, Hanna S.; Strijkstra, Annemieke; Kant, Mirjam; Vagts, Jannes; Wünsch, Daniel; Michalke, Bernhard; Maczka, Michael; Schulz, Stefan; Hillebrand, Helmut; Blasius, Bernd

    2017-01-01

    Abstract The stoichiometric constraints of algal growth are well understood, whereas there is less knowledge for heterotrophic bacterioplankton. Growth of the marine bacterium Phaeobacter inhibens DSM 17395, belonging to the globally distributed Roseobacter group, was studied across a wide concentration range of NH4+ and PO43−. The unique dataset covers 415 different concentration pairs, corresponding to 207 different molar N:P ratios (from 10−2 to 105). Maximal growth (by growth rate and biomass yield) was observed within a restricted concentration range at N:P ratios (∼50−120) markedly above Redfield. Experimentally determined growth parameters deviated to a large part from model predictions based on Liebig's law of the minimum, thus implicating synergistic co-limitation due to biochemical dependence of resources. Internal elemental ratios of P. inhibens varied with external nutrient supply within physiological constraints, thus adding to the growing evidence that aquatic bacteria can be flexible in their internal elemental composition. Taken together, the findings reported here revealed that P. inhibens is well adapted to fluctuating availability of inorganic N and P, expected to occur in its natural habitat (e.g. colonized algae, coastal areas). Moreover, this study suggests that elemental variability in bacterioplankton needs to be considered in the ecological stoichiometry of the oceans. PMID:28486660

  15. The origins of the Redfield nitrogen-to-phosphorus ratio are in a homoeostatic protein-to-rRNA ratio.

    PubMed

    Loladze, Irakli; Elser, James J

    2011-03-01

    One of the most intriguing patterns in the biosphere is the similarity of the atomic nitrogen-to-phosphorus ratio (N:P) = 16 found in waters throughout the deep ocean and in the plankton in the upper ocean. Although A.C. Redfield proposed in 1934 that the intracellular properties of plankton were central to this pattern, no theoretical significance for N:P = 16 in cells had been found. Here, we use theoretical modelling and a compilation of literature data for prokaryotic and eukaryotic microbes to show that the balance between two fundamental processes, protein and rRNA synthesis, results in a stable biochemical attractor that homoeostatically produces a given protein:rRNA ratio. Furthermore, when biochemical constants and reasonable kinetic parameters for protein synthesis and ribosome production under nutrient-replete conditions are applied in the model, it predicts a stable protein:rRNA ratio of 3 ± 0.7, which corresponds to N:P = 16 ± 3. The model also predicts that N-limitation, by constraining protein synthesis rates, will result in N:P ratios below the Redfield value while P-limitation, by constraining RNA production rates, will produce ratios above the Redfield value. Hence, one of most biogeochemically significant patterns on Earth is inherently rooted in the fundamental structure of life.

  16. 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.

  17. Adaptive optics simulation of intraocular lenses with modified spherical aberration.

    PubMed

    Piers, Patricia A; Fernandez, Enrique J; Manzanera, Silvestre; Norrby, Sverker; Artal, Pablo

    2004-12-01

    Adaptive optics systems can be used to investigate the potential visual benefit associated with correcting ocular wave-front aberration. In this study, adaptive optics techniques were used to evaluate the potential advantages and disadvantages associated with intraocular lenses (IOLs) with modified spherical aberration profiles. An adaptive optics vision simulator was constructed that allows psychophysical tests to be performed while viewing targets through any desired ocular wave-front profile. With this simulator, the subjective visual performance of four subjects was assessed by letter acuity and contrast sensitivity (at 3, 6, and 15 cyc/deg) for two different values of induced spherical aberration. The values of spherical aberration were chosen to reproduce two conditions: the average amount measured in pseudophakic patients with implanted IOLs having spherical surfaces and the complete correction of the individual's spherical aberration. Visual performance was assessed in both white and green light, at best focus and for defocus of +/-0.5 and +/-1.0 D. There was an average improvement in visual acuity associated with the correction of spherical aberration of 10% and 38% measured in white and green light, respectively. Similarly, average contrast sensitivity measurements improved 32% and 57% in white and green light. When spherical aberration was corrected, visual performance was as good as or better than for the normal spherical aberration case for defocus as large as +/-1 D. Correcting ocular spherical aberration improves spatial vision in the best-focus position without compromising the subjective tolerance to defocus.

  18. 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.

  19. Simulation of triaxial response of granular materials by modified DEM

    NASA Astrophysics Data System (ADS)

    Wang, XiaoLiang; Li, JiaChun

    2014-12-01

    A modified discrete element method (DEM) with rolling effect taken into consideration is developed to examine macroscopic behavior of granular materials in this study. Dimensional analysis is firstly performed to establish the relationship between macroscopic mechanical behavior, mesoscale contact parameters at particle level and external loading rate. It is found that only four dimensionless parameters may govern the macroscopic mechanical behavior in bulk. The numerical triaxial apparatus was used to study their influence on the mechanical behavior of granular materials. The parametric study indicates that Poisson's ratio only varies with stiffness ratio, while Young's modulus is proportional to contact modulus and grows with stiffness ratio, both of which agree with the micromechanical model. The peak friction angle is dependent on both inter-particle friction angle and rolling resistance. The dilatancy angle relies on inter-particle friction angle if rolling stiffness coefficient is sufficiently large. Finally, we have recommended a calibration procedure for cohesionless soil, which was at once applied to the simulation of Chende sand using a series of triaxial compression tests. The responses of DEM model are shown in quantitative agreement with experiments. In addition, stress-strain response of triaxial extension was also obtained by numerical triaxial extension tests.

  20. Modified sequential fully implicit scheme for compositional flow simulation

    NASA Astrophysics Data System (ADS)

    Moncorgé, A.; Tchelepi, H. A.; Jenny, P.

    2017-05-01

    The fully implicit (FI) method is widely used for numerical modeling of multiphase flow and transport in porous media. The FI method is unconditionally stable, but that comes at the cost of a low-order approximation and high computational cost. The FI method entails iterative linearization and solution of fully-coupled linear systems with mixed elliptic/hyperbolic character. However, in methods that treat the near-elliptic (flow) and hyperbolic (transport) separately, such as multiscale formulations, sequential solution strategies are used to couple the flow (pressures and velocities) and the transport (saturations/compositions). The most common sequential schemes are: the implicit pressure explicit saturation (IMPES), and the sequential fully implicit (SFI) schemes. Problems of practical interest often involve tightly coupled nonlinear interactions between the multiphase flow and the multi-component transport. For such problems, the IMPES approach usually suffers from prohibitively small timesteps in order to obtain stable numerical solutions. The SFI method, on the other hand, does not suffer from a temporal stability limit, but the convergence rate can be extremely slow. This slow convergence rate of SFI can offset the gains obtained from separate and specialized treatments of the flow and transport problems. In this paper, we analyze the nonlinear coupling between flow and transport for compressible, compositional systems with complex interphase mass transfer. We isolate the nonlinear effects related to transmissibility and compressibility from those due to interphase mass transfer, and we propose a modified SFI (m-SFI) method. The new scheme involves enriching the 'standard' pressure equation with coupling between the pressure and the saturations/compositions. The modification resolves the convergence problems associated with SFI and provides a strong basis for using sequential formulations for general-purpose simulation. For a wide parameter range, we show

  1. Pesticide trapping efficiency of a modified backwater wetland using a simulated runoff event

    USDA-ARS?s Scientific Manuscript database

    This study examined the trapping efficiency of a modified backwater wetland amended with a mixture of three pesticides, atrazine, metolachlor, and fipronil, using a simulated runoff event. The 700 m long, 25 m wide wetland, located along the Coldwater River in Tunica County, Mississippi, was modifie...

  2. Modified Evacuated-Tube Collector Tested in Solar Simulator

    NASA Technical Reports Server (NTRS)

    1982-01-01

    According to report, particular commercial evacuated-tube solar collector performs slightly more efficiently with larger manifold. Tests were performed with Marshall Space Flight Center solar simulator. Report describes test conditions and procedures, provides analysis of results, and presents tables and graphs of data, both measured and calculated.

  3. Fertilizing the Ocean Deserts During the LGM: Is There Evidence for Increased Paleoproductivity and Redfield Decoupling in the Glacial Tropical/Subtropical World Ocean?

    NASA Astrophysics Data System (ADS)

    Archer, R. B.; Stott, L. D.

    2002-12-01

    Twenty-five cores were taken from all three tropical and subtropical ocean basins to evaluate changes in surface water productivity as a function of Dd13Ccalcite G. ruber (LGM-HOL) of the low latitude biological pump in a cool glacial world. Corrections applied to the data included a -0.32% carbon reservoir effect, as well as correcting for temperature dependent atmospheric-oceanic CO2 equilibrium. Evidence for productivity in excess of Redfield Dd13Ccalcite G. ruber : [PO4- ] limitations is taken where Dd13Ccalcite G. ruber (LGM-HOL) in excess of Redfield = Dd13Ccalcite G. ruber (LGM-HOL) -0.93 _%umol*kg [PO4- ]. Dd13Ccalcite G. ruber distributions allow for three main conclusions regarding the strength of the biological pump in tropical and subtropical HNLP and LNLP zones during the Last Glacial Maximum: 1.) Nutrient fronts associated with HNLP regions today expanded further into subtropical oligotrophic gyres, where iron deposition in a dustier glacial world freed phytoplankton from iron limitation, thus allowing for enhanced carbon export out of surface waters. Almost all sites demonstrated increased export in these regions in accordance to and within detectable bounds of presently understood Redfield nutrient dynamics. 2.) Evidence for decoupling of Redfield occurs in the oligotrophic world ocean along HNLP-LNLP transitional niche ecotomes. Redfield decoupling in these zones can be associated with sites of large diatom paleo-depositional events limited in spatial extent, but very intense in production through time during the Last Glacial. Diatom species associated with large Dd13Ccalcite G. ruber isotopic excursions beyond Redfield constraints are non-obligate diazotrophs Rhizosolenia sp and Ethmodiscus Rex. Decoupling of Redfield at these sites leaves unique isotopic signatures in marine sedimentary records despite lack of preservation for other diazotrophs such as cyanobacterial Trichodesmium sp. 3.) Despite the presence of smaller diazotrophs in the modern

  4. Modified social force model based on information transmission toward crowd evacuation simulation

    NASA Astrophysics Data System (ADS)

    Han, Yanbin; Liu, Hong

    2017-03-01

    In this paper, the information transmission mechanism is introduced into the social force model to simulate pedestrian behavior in an emergency, especially when most pedestrians are unfamiliar with the evacuation environment. This modified model includes a collision avoidance strategy and an information transmission model that considers information loss. The former is used to avoid collision among pedestrians in a simulation, whereas the latter mainly describes how pedestrians obtain and choose directions appropriate to them. Simulation results show that pedestrians can obtain the correct moving direction through information transmission mechanism and that the modified model can simulate actual pedestrian behavior during an emergency evacuation. Moreover, we have drawn four conclusions to improve evacuation based on the simulation results; and these conclusions greatly contribute in optimizing a number of efficient emergency evacuation schemes for large public places.

  5. Simulated Stellarator Edge Behavior with Modified HSX Coils

    NASA Astrophysics Data System (ADS)

    Bader, A.; Stephey, L. A.; Anderson, D. T.; Feng, Y.; Hegna, C. C.; Schmitz, O.; Talmadge, J. N.

    2014-10-01

    Predicting the edge behavior of a 3D device is a difficult but necessary requirement in the design of new fusion devices. In this poster we focus on prototypical stellarators generated through modifications to the HSX coils. We employ both helical coils to change the island size without altering the rotational transform, and divertor dipole coils to alter the internal structure of the islands. To determine the edge behavior of the designs we use simple metrics obtained through vacuum field-line following along with advanced simulation capabilities from the coupled codes EMC3-EIRENE. We show that strike point locations and concentrations can be altered with substantial changes to edge island sizes. Changes to the internal structure of the islands, producing alterations to flow structures and plasma density, but do not have a significant impact on strike point calculations or predicted heat flux. Results have implications on the role of islands in edges of stellarators and other 3D devices. Work supported by DOE-SC0006103.

  6. New wave simulations to the (3+1)-dimensional modified Kdv-Zakharov-Kuznetsov equation

    NASA Astrophysics Data System (ADS)

    Baskonus, Haci Mehmet; Koç, Dilara Altan; Gülsu, Mustafa; Bulut, Hasan

    2017-07-01

    In this study, we apply an effective method which is improved Bernoulli sub-equation function method (IBSEFM) to the (3+1)-dimensional modified KdV-Zakharov-Kuznetsov equation. It gives some new wave simulations such as complex and exponential structures. We check up whether all structures verify the (3+1)-dimensional modified KdV-Zakharov-Kuznetsov model. Then, we plot three and two dimensional surfaces of obtained solutions by using Wolfram Mathematica 9.

  7. Optimal actuator placement on an active reflector using a modified simulated annealing technique

    NASA Technical Reports Server (NTRS)

    Kuo, Chin-Po; Bruno, Robin

    1991-01-01

    The development of a lightweight actuation system for maintaining the surface accuracy of a composite honeycomb panel using piezoelectric actuators is discussed. A modified simulated annealing technique is used to optimize the problem with both combinatorial and continuous criteria and with inequality constraints. Near optimal solutions for the location of the actuators, using combinatorial optimization, and for the required actuator forces, employing continuous optimization, are sought by means of the modified simulated annealing technique. The actuator locations are determined by first seeking a near optimum solution using the modified simulated annealing technique. The final actuator configuration consists of an arrangement wherein the piezoelectric actuators are placed along six radial lines. Numerical results showing the achievable surface correction by means of this configuration are presented.

  8. 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)

  9. Simulation of a photovoltaic/thermal heat pump system having a modified collector/evaporator

    SciTech Connect

    Xu, Guoying; Deng, Shiming; Zhang, Xiaosong; Yang, Lei; Zhang, Yuehong

    2009-11-15

    A new photovoltaic/thermal heat pump (PV/T-HP) system having a modified collector/evaporator (C/E) has been developed and numerically studied. Multi-port flat extruded aluminum tubes were used in the modified C/E, as compared to round copper tubes used in a conventional C/E. Simulation results suggested that a better operating performance can be achieved for a PV/T-HP system having such a modified C/E. In addition, using the meteorological data in both Nanjing and Hong Kong, China, the simulation results showed that this new PV/T-HP system could efficiently generate electricity and thermal energy simultaneously in both cities all-year-round. Furthermore, improved operation by using variable speed compressor has been designed and discussed. (author)

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Bose, Sownak; Li, Baojiu; Barreira, Alexandre; He, Jian-hua; Hellwing, Wojciech A.; Koyama, Kazuya; Llinares, Claudio; Zhao, Gong-Bo

    2017-02-01

    We describe and demonstrate the potential of a new and very efficient method for simulating certain classes of modified gravity theories, such as the widely studied f(R) gravity models. High resolution simulations for such models are currently very slow due to the highly nonlinear partial differential equation that needs to be solved exactly to predict the modified gravitational force. This nonlinearity is partly inherent, but is also exacerbated by the specific numerical algorithm used, which employs a variable redefinition to prevent numerical instabilities. The standard Newton-Gauss-Seidel iterative method used to tackle this problem has a poor convergence rate. Our new method not only avoids this, but also allows the discretised equation to be written in a form that is analytically solvable. We show that this new method greatly improves the performance and efficiency of f(R) simulations. For example, a test simulation with 5123 particles in a box of size 512 Mpc/h is now 5 times faster than before, while a Millennium-resolution simulation for f(R) gravity is estimated to be more than 20 times faster than with the old method. Our new implementation will be particularly useful for running very high resolution, large-sized simulations which, to date, are only possible for the standard model, and also makes it feasible to run large numbers of lower resolution simulations for covariance analyses. We hope that the method will bring us to a new era for precision cosmological tests of gravity.

  12. Nonequilibrium molecular dynamics simulation of pressure-driven water transport through modified CNT membranes.

    PubMed

    Wang, Luying; Dumont, Randall S; Dickson, James M

    2013-03-28

    Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.

  13. Nonequilibrium molecular dynamics simulation of pressure-driven water transport through modified CNT membranes

    NASA Astrophysics Data System (ADS)

    Wang, Luying; Dumont, Randall S.; Dickson, James M.

    2013-03-01

    Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.

  14. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    SciTech Connect

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

    2016-03-14

    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.

  16. A Modified Shake Algorithm for Maintaining Rigid Bonds in Molecular Dynamics Simulations of Large Molecules

    NASA Astrophysics Data System (ADS)

    Lambrakos, S. G.; Boris, J. P.; Oran, E. S.; Chandrasekhar, I.; Nagumo, M.

    1989-12-01

    We present a new modification of the SHAKE algorithm, MSHAKE, that maintains fixed distances in molecular dynamics simulations of polyatomic molecules. The MSHAKE algorithm, which is applied by modifying the leapfrog algorithm to include forces of constraint, computes an initial estimate of constraint forces, then iteratively corrects the constraint forces required to maintain the fixed distances. Thus MSHAKE should always converge more rapidly than SHAKE. Further, the explicit determination of the constraint forces at each timestep makes MSHAKE convenient for use in molecular dynamics simulations where bond stress is a significant dynamical quantity.

  17. Adaptive Splitting Integrators for Enhancing Sampling Efficiency of Modified Hamiltonian Monte Carlo Methods in Molecular Simulation.

    PubMed

    Akhmatskaya, Elena; Fernández-Pendás, Mario; Radivojević, Tijana; Sanz-Serna, J M

    2017-08-02

    The modified Hamiltonian Monte Carlo (MHMC) methods, i.e., importance sampling methods that use modified Hamiltonians within a Hybrid Monte Carlo (HMC) framework, often outperform in sampling efficiency standard techniques such as molecular dynamics (MD) and HMC. The performance of MHMC may be enhanced further through the rational choice of the simulation parameters and by replacing the standard Verlet integrator with more sophisticated splitting algorithms. Unfortunately, it is not easy to identify the appropriate values of the parameters that appear in those algorithms. We propose a technique, that we call MAIA (Modified Adaptive Integration Approach), which, for a given simulation system and a given time step, automatically selects the optimal integrator within a useful family of two-stage splitting formulas. Extended MAIA (or e-MAIA) is an enhanced version of MAIA, which additionally supplies a value of the method-specific parameter that, for the problem under consideration, keeps the momentum acceptance rate at a user-desired level. The MAIA and e-MAIA algorithms have been implemented, with no computational overhead during simulations, in MultiHMC-GROMACS, a modified version of the popular software package GROMACS. Tests performed on well-known molecular models demonstrate the superiority of the suggested approaches over a range of integrators (both standard and recently developed), as well as their capacity to improve the sampling efficiency of GSHMC, a noticeable method for molecular simulation in the MHMC family. GSHMC combined with e-MAIA shows a remarkably good performance when compared to MD and HMC coupled with the appropriate adaptive integrators.

  18. 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.

  19. Ammonia-nitrogen and phosphates sorption from simulated reclaimed waters by modified clinoptilolite.

    PubMed

    Huo, Hanxin; Lin, Hai; Dong, Yingbo; Cheng, Huang; Wang, Han; Cao, Lixia

    2012-08-30

    This paper presents the investigation of the ammonia-nitrogen and phosphates sorption from simulated reclaimed wastewater by modified clinoptilolite. The results showed that the modified clinoptilolite has a high sorption efficiency and removal performance. The ammonia-nitrogen and phosphates removal rate of the modified clinoptilolite reached to 98.46% and 99.80%, respectively. The surface of modified clinoptilolite became loose and some pores appeared, which enlarged the specific surface area; the contents of Na and Fe increased, and the contents of Ca and Mg decreased. The modified clinoptilolite possesses rapid sorption and slow balance characteristics and ammonia-nitrogen and phosphates sorption is more consistent with the Langmuir isotherm model. The adsorption kinetics of ammonia-nitrogen and phosphates follows the Elovich adsorption dynamics equation, which describes the sorption of ammonia-nitrogen and phosphates in aqueous solution as mainly a chemical sorption. Results from the thermodynamics experiment involving ammonia-nitrogen and phosphates sorption reveal that the process is a spontaneous and endothermic process, and is mainly driven by entropy effect. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Simulation of fluid-solid coexistence via thermodynamic integration using a modified cell model.

    PubMed

    Nayhouse, Michael; Amlani, Ankur M; Heng, Vincent R; Orkoulas, G

    2012-04-18

    Despite recent advances, precise simulation of fluid-solid transitions still remains a challenging task. Thermodynamic integration techniques are the simplest methods to study fluid-solid coexistence. These methods are based on the calculation of the free energies of the fluid and the solid phases, starting from a state of known free energy which is usually an ideal-gas state. Despite their simplicity, the main drawback of thermodynamic integration techniques is the large number of states that must be simulated. In the present work, a thermodynamic integration technique, which reduces the number of simulated states, is proposed and tested on a system of particles interacting via an inverse twelfth-power potential energy function. The simulations are implemented at constant pressure and the solid phase is modeled according to the constrained cell model of Hoover and Ree. The fluid and the solid phases are linked together by performing constant-pressure simulations of a modified cell model. The modified cell model, which was originally proposed by Hoover and Ree, facilitates transitions between the fluid and the solid phase by tuning a homogeneous external field. This model is simulated on a constant-pressure path for a series of progressively increasing values of the field, thus allowing for direct determination of the free energy difference between the fluid and the solid phase via histogram reweighting. The size-dependent results are analyzed using histogram reweighting and finite-size scaling techniques. The scaling analysis is based on studying the size-dependent behavior of the second- and higher-order derivatives of the free energy as well as the dimensionless moment ratios of the order parameter. The results clearly demonstrate the importance of accounting for size effects in simulation studies of fluid-solid transitions.

  1. 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.

  2. Modified three-dimensional percolation simulation of char fragmentation and particulate formation

    NASA Astrophysics Data System (ADS)

    Wang, Huashan; Li, Huiyi; Chen, Qingjie; Gao, Jianmin; Wang, Chunsheng

    2017-02-01

    The current numerical calculation of particulate formation during char combustion mainly adopts the two-dimensional model. In this paper, based on the introduction of the concept of diffusion depth, the char combustion is simulated with a three-dimensional model. The modified model can simulate the actual situation that the reactant gas dose not diffuse into the char completely. The approach to realize the combustion process of char in chemical controlled zone (zone I) and transitional controlled zone (zone II) is given, and the results are compared with those in the diffusion controlled zone (zone III). The characteristic impact of initial porosity and mineral content on particulate formation in different zones is analyzed through the simulation and comparison. It can be seen from the results that the diffusion depth do put some limits on char fragmentation and mass distribution of ash particulates, which provides theoretical basis for the further study of particulate formation during char combustion and the reduction of particulate emission.

  3. A model to simulate the haemodynamic effects of right heart pulsatile flow after modified Fontan procedure.

    PubMed Central

    Tamaki, S; Kawazoe, K; Yagihara, T; Abe, T

    1992-01-01

    The effect of pulsatile pulmonary flow after the modified Fontan procedure was examined in a model that simulated the right heart. An inlet overflow tank (preload), axial pulsatile pump, Wind-Kessel model (afterload), and an outlet overflow tank were connected in series. The standard conditions were flow 2.00 l/min with 12 mm Hg preload pressure, 3.0 Wood units resistance, and an outlet overflow tank pressure at 6 mm Hg. The pump rate was set at 80 beats/min. The simulated pulmonary arterial pressure and pulmonary flow waves produced by this model closely resembled those obtained from patients who had undergone the modified Fontan procedure. All variables except the preload were fixed and changes in pulmonary flow were examined at preload pressures of 8, 12, 15, and 17 mm Hg. As the peak pulmonary arterial pressure increased so did pulmonary flow, until it was greater than during the non-pulsatile state. Because the afterload of this model was fixed, this result suggests that there was a concomitant decrease in resistance. This model indicates that pulsatile pulmonary blood flow is likely to have a beneficial effect on the pulmonary circulation after the modified Fontan procedure. PMID:1540439

  4. Simulating a cyclic activated sludge system by employing a modified ASM3 model for wastewater treatment.

    PubMed

    Gao, Feng; Nan, Jun; Zhang, Xinhui

    2017-03-13

    To interpret the biological nutrient removal in a cyclic activated sludge system (CAS), a modified model was developed by combining the process of simultaneous storage and growth, and the kinetics of soluble microbial product (S SMP) and extracellular polymeric substance (X EPS) with activated sludge model no. 3 (ASM3). These most sensitive parameters were initially selected whilst parameters with low sensitivity were given values from literature. The selected parameters were then calibrated on an oxygen uptake rate test and a batch CAS reactor on an operational cycle. The calibrated model was validated using a combination of the measurements from a batch CAS reactor operated for 1 month and the average deviation method. The simulations demonstrated that the modified model was capable of predicting higher effluent concentrations compared to outputs of the ASM3 model. Additionally, it was also shown that the average deviation of effluent S COD, S NH, S SMP and X EPS simulated with the modified model was all less than 1 mg L(-1). In summary, the model could effectively describe biological processes in a CAS reactor and provide a wonderful tool for operation.

  5. Simulations of a modified SOP model applied to retrospective revaluation of human causal learning.

    PubMed

    Aitken, Michael R F; Dickinson, Anthony

    2005-05-01

    Dickinson and Burke (1996) proposed a modified version of Wagner's (1981) SOP associative theory to explain retrospective revaluation of human causal judgments. In this modified SOP (MSOP), excitatory learning occurs when cue and outcome representations are either both directly activated or both associatively activated. By contrast, inhibitory learning occurs when one representation is directly activated while the other is associatively activated. Finite node simulations of MSOP yielded simple acquisition, overshadowing, blocking, and inhibitory learning under forward contingencies. Importantly, retrospective revaluation was predicted in the form of unovershadowing and backward inhibitory learning. However, MSOP did not yield backward blocking. These predictions are evaluated against the relevant empirical evidence and contrasted with the predictions of other associative theories that have been applied to retrospective revaluation of human causal and predictive learning.

  6. 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.

  7. 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.

  8. Simulation and applications of a novel modified SBR system for biological nutrient removal.

    PubMed

    Wu, W; Timpany, P; Dawson, B

    2001-01-01

    Dynamic simulation and applications of a novel, continuous-fed, constant level modified sequencing batch reactor for biological nutrient removal are presented. The underlying mathematical model and practical applications of the simulation are discussed. Case studies are presented to illustrate the applications as well as the flexibility of the system in meeting different wastewater treatment requirements. Operation experience from full-scale wastewater treatment plant demonstrates the reliability, ease of operation and high efficiency of the system. Average BOD5, total nitrogen, total phosphorus and TSS removals of 97, 81, 88 and 94% are achieved respectively on an annual basis with little operator attention. Consistently high waste activated sludge concentrations are demonstrated, averaging approximately 20,000 mg/L.

  9. The simulation of circuit breaker switching using a composite Cassie-modified Mayr model

    SciTech Connect

    Thomas, D.W.P.; Pereira, E.T.; Christopoulos, C.; Howe, A.F.

    1995-10-01

    In substation electromagnetic compatibility studies or insulation coordination studies it is desirable to get as accurate a representation as possible of the transients generated by faults and switching events. A method of simulating the voltage and current transients generated by a gas blast circuit breaker operation using a composite Cassie-modified Mayr model of the circuit breaker arc is described. It is demonstrated that this gives good agreement with published laboratory measurements of the circuit breaker voltage and current. The transmission line modeling method is used int the construction of the simulation algorithm of the circuit breaker circuit. A method, based on describing the circuit breaker by a transmission-line model (TLM), is used to decouple the non-linear characteristics from the rest of the network.

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

    NASA Astrophysics Data System (ADS)

    Porciani, Cristiano

    2016-12-01

    Constrained realizations 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 realizations 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 pre-selected 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.

  11. Improved simulation of precipitation in the tropics using a modified BMJ scheme in the WRF model

    NASA Astrophysics Data System (ADS)

    Fonseca, R. M.; Zhang, T.; Yong, K.-T.

    2015-09-01

    The successful modelling of the observed precipitation, a very important variable for a wide range of climate applications, continues to be one of the major challenges that climate scientists face today. When the Weather Research and Forecasting (WRF) model is used to dynamically downscale the Climate Forecast System Reanalysis (CFSR) over the Indo-Pacific region, with analysis (grid-point) nudging, it is found that the cumulus scheme used, Betts-Miller-Janjić (BMJ), produces excessive rainfall suggesting that it has to be modified for this region. Experimentation has shown that the cumulus precipitation is not very sensitive to changes in the cloud efficiency but varies greatly in response to modifications of the temperature and humidity reference profiles. A new version of the scheme, denoted "modified BMJ" scheme, where the humidity reference profile is more moist, was developed. In tropical belt simulations it was found to give a better estimate of the observed precipitation as given by the Tropical Rainfall Measuring Mission (TRMM) 3B42 data set than the default BMJ scheme for the whole tropics and both monsoon seasons. In fact, in some regions the model even outperforms CFSR. The advantage of modifying the BMJ scheme to produce better rainfall estimates lies in the final dynamical consistency of the rainfall with other dynamical and thermodynamical variables of the atmosphere.

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

    PubMed

    Jeppu, Gautham P; Clement, T Prabhakar

    2012-03-15

    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.

  13. 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.

  14. Multiobjective optimization with a modified simulated annealing algorithm for external beam radiotherapy treatment planning

    SciTech Connect

    Aubry, Jean-Francois; Beaulieu, Frederic; Sevigny, Caroline; Beaulieu, Luc; Tremblay, Daniel

    2006-12-15

    Inverse planning in external beam radiotherapy often requires a scalar objective function that incorporates importance factors to mimic the planner's preferences between conflicting objectives. Defining those importance factors is not straightforward, and frequently leads to an iterative process in which the importance factors become variables of the optimization problem. In order to avoid this drawback of inverse planning, optimization using algorithms more suited to multiobjective optimization, such as evolutionary algorithms, has been suggested. However, much inverse planning software, including one based on simulated annealing developed at our institution, does not include multiobjective-oriented algorithms. This work investigates the performance of a modified simulated annealing algorithm used to drive aperture-based intensity-modulated radiotherapy inverse planning software in a multiobjective optimization framework. For a few test cases involving gastric cancer patients, the use of this new algorithm leads to an increase in optimization speed of a little more than a factor of 2 over a conventional simulated annealing algorithm, while giving a close approximation of the solutions produced by a standard simulated annealing. A simple graphical user interface designed to facilitate the decision-making process that follows an optimization is also presented.

  15. 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).

  16. Electrochemical behavior of a typical redox mediator on a modified electrode surface: Experiment and computer simulations

    NASA Astrophysics Data System (ADS)

    Gavilán Arriazu, E. M.; Paz Zanini, Verónica I.; Gulotta, Florencia A.; Araujo, Virginia M.; Pinto, O. A.

    2017-04-01

    This paper describes the study of a redox species electrosorption on a modified electrode by experimental measurements and computer simulation. The propose model is based on the fact that charges are transferred to the electrode when an electroactive species is adsorbed on its surface. The electrode surface is modified by the irreversible adsorption of a non-electroactive species, which blocks a percentage of the adsorption sites. Hence, the electroactive species can only be adsorbed on the surface vacancies, and, when this phenomenon occurs, interact laterally with the non-electroactive one. Lattice-gas models and Monte Carlo simulations in the Gran Canonical Ensemble are used. The analysis conducted is based on the study of adsorption isotherms and voltammograms, for several values of energies and adsorption degrees of the non-electroactive species. In the case of experimental measurements, an artificial clay (Laponite®) represents the non-electroactive species while the redox probe Fe(CN)64- is the electroactive one. The results obtained by the proposed model are compared with experimental voltammograms.

  17. Molecular dynamics simulations to aid the rational design of organic friction modifiers.

    PubMed

    Davidson, J E; Hinchley, S L; Harris, S G; Parkin, A; Parsons, S; Tasker, P A

    2006-12-01

    Molecular dynamics simulations were performed under conditions of constant volume and temperature and of constant pressure and temperature to elucidate the structure activity relationships of a series of non-ionic surfactant molecules derived from vegetable fat and employed as friction modifiers in commercial engine oils. The simulations show the extent to which intermolecular hydrogen bonding is important in determining the stability of the monolayer formed by the surfactant molecules and show that mono-alkanoyl glyceride molecules are able to pack more efficiently, forming significantly more intermolecular hydrogen bonds and occupying approximately half the volume needed by di-alkanoyl glyceride molecules. Density profiles are presented which show significant mixing of the hydrophobic tail groups and a non-polar solvent. The distribution of torsion angles in the tail groups shows that the conformation is consistent with a liquid at finite temperature rather than a crystal structure. The measured friction coefficients of equimolar solutions of the glycerides show that the efficacy as friction modifiers varies in the order mono-, di- and the tri-oleyl glyceride, which is consistent with the efficacy of film formation predicted by the molecular dynamics calculations.

  18. Modified Beef Tongue Model for Fourth-Degree Laceration Repair Simulation.

    PubMed

    Illston, Jana D; Ballard, Alicia C; Ellington, David R; Richter, Holly E

    2017-03-01

    An existing model for fourth-degree laceration repair uses beef tongue with plastic or vinyl tubing. This modified model substitutes beef tripe for the anal mucosa and chicken leg muscles for the anal sphincter muscle analogs to create a realistic model. Tripe is tunneled through the body of the trimmed beef tongue and sutured like an ostomy to simulate the anal canal. The tongue is incised toward the tripe "anal canal." Chicken leg muscles are tunneled from the incision out to the cut edges of the beef tongue to create anal sphincter muscle analogs. Procedures can be repeated on the opposite side. Two double-sided models can be made per tongue. The model can be refrigerated or frozen and thawed before use. A fourth-degree laceration can be cut immediately before use. Materials were obtained at a local supermarket for $5-7 per half-tongue, double-sided model. Residents responded positively to the model and stated that animal tissue provided realistic haptic simulation. The modified beef tongue model utilizing tripe and chicken leg muscles as anal mucosa and anal sphincter muscle analogs, respectively, provided excellent perceived haptic fidelity. Moreover, it is an innovative, inexpensive, and well-received teaching tool to augment resident education.

  19. 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.

  20. 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.

  1. 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

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

    PubMed Central

    2014-01-01

    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. PMID:25277743

  3. Revisiting N2 fixation in the North Atlantic Ocean: Significance of deviations from the Redfield Ratio, atmospheric deposition and climate variability

    NASA Astrophysics Data System (ADS)

    Singh, Arvind; Lomas, M. W.; Bates, N. R.

    2013-09-01

    The average oceanic nitrate-to-phosphate molar ratio (NO3-:PO43-≈16:1, referred to as the Redfield Ratio) in subsurface waters, which is similar to the average ratio of particulate nitrogen (N)-to-phosphorus (P) in phytoplankton, is the cornerstone in calculating geochemical estimates of N2 fixation and denitrification rates. Any deviations from this canonical Redfield Ratio in intermediate ocean waters, expressed as N* (a measure of NO3- in excess or deficit of 16×PO43-), provides an integrated estimate of net N fluxes into and out of the ocean. In well-oxygenated ocean basins such as the North Atlantic Ocean, N* estimates are usually positive and can be used to infer that rates of N2 fixation exceed rates of denitrification. We use this approach to estimate N2 fixation over the last two decades (1988-2009) based on data collected at the Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic Ocean near Bermuda. Our results indicate that interpretation of the N* tracer as an estimate of N2 fixation should be undertaken with caution, as N2 fixation is not the only process that results in a positive N* estimate. The impacts of a locally variable nitrogen-to-phosphorus ratio, relative to the fixed Redfield Ratio, in the suspended particulate matter as well as in the subsurface water nutrients and atmospheric N deposition on N* variability were examined. Furthermore, we explored the role of climate modes (i.e., North Atlantic Oscillation and Arctic Oscillation) on N* variability. We found that N* in the subsurface waters was significantly affected by these factors and hence previous estimates of N2 fixation using this technique might have been substantially overestimated. Our revised estimate of N2 fixation in the North Atlantic Ocean (0°N-50°N, 20°W-80°W) is 12.2±0.9×1011 mol N yr-1, and based on long-term BATS data provides better constraints than both earlier indirect and direct estimates N2 fixation.

  4. Modified impedance control for robotic saw cutting: Simulation and implementation in three degrees of freedom

    SciTech Connect

    Kriikku, E.M.; Reynolds, D.L.; Carroll, J.J.; Dawson, D.M.

    1993-12-31

    The Savannah River Site (SRS) production and decommissioning operations produce solid radioactive transuranic (TRU) waste. This waste must be repackaged and sent to the Waste Isolation Pilot Plant (WIPP) for permanent disposal. The Savannah River Technology Center (SRTC) built a test facility to demonstrate simulated waste processing. The test facility use`s a CIMCORP multi-axis robot system, a CIMROC{trademark} II robot controller, and an electric circular saw to remotely open and size reduce plywood crates. The robot can either be teleoperated using joysticks or autonomously controlled via the, CIMROC{trademark} II. Both methods are inadequate for circular saw cutting of plywood crates due to frequent saw blade binding. Blade binding results from the current commercial robot controller limitations. The limitations are overcome by incorporating additional sensor information into the existing controller structure. In this paper we utilize a force sensor and a frequency counter to implement a modified impedance controller which prevents saw blade binding.

  5. Modified impedance control for robotic saw cutting: Simulation and implementation in three degrees of freedom

    SciTech Connect

    Kriikku, E.M. ); Reynolds, D.L.; Carroll, J.J.; Dawson, D.M. . School of Electrical and Computer Engineering)

    1993-01-01

    The Savannah River Site (SRS) production and decommissioning operations produce solid radioactive transuranic (TRU) waste. This waste must be repackaged and sent to the Waste Isolation Pilot Plant (WIPP) for permanent disposal. The Savannah River Technology Center (SRTC) built a test facility to demonstrate simulated waste processing. The test facility use's a CIMCORP multi-axis robot system, a CIMROC[trademark] II robot controller, and an electric circular saw to remotely open and size reduce plywood crates. The robot can either be teleoperated using joysticks or autonomously controlled via the, CIMROC[trademark] II. Both methods are inadequate for circular saw cutting of plywood crates due to frequent saw blade binding. Blade binding results from the current commercial robot controller limitations. The limitations are overcome by incorporating additional sensor information into the existing controller structure. In this paper we utilize a force sensor and a frequency counter to implement a modified impedance controller which prevents saw blade binding.

  6. Modified shock waves for extracorporeal shock wave lithotripsy: a simulation based on the Gilmore formulation.

    PubMed

    Canseco, Guillermo; de Icaza-Herrera, Miguel; Fernández, Francisco; Loske, Achim M

    2011-10-01

    Extracorporeal shock wave lithotripsy (SWL) is a reliable therapy for the treatment of urolithiasis. Nevertheless, improvements to enhance stone fragmentation and reduce tissue damage are still needed. During SWL, cavitation is one of the most important stone fragmentation mechanisms. Bubbles with a diameter between about 7 and 55μm have been reported to expand and collapse after shock wave passage, forming liquid microjets at velocities of up to 400m/s that contribute to the pulverization of renal calculi. Several authors have reported that the fragmentation efficiency may be improved by using tandem shock waves. Tandem SWL is based on the fact that the collapse of a bubble can be intensified if a second shock wave arrives tenths or even a few hundredths of microseconds before its collapse. The object of this study is to determine if tandem pulses consisting of a conventional shock wave (estimated rise time between 1 and 20ns), followed by a slower second pressure profile (0.8μs rise time), have advantages over conventional tandem SWL. The Gilmore equation was used to simulate the influence of the modified pressure field on the dynamics of a single bubble immersed in water and compare the results with the behavior of the same bubble subjected to tandem shock waves. The influence of the delay between pulses on the dynamics of the collapsing bubble was also studied for both conventional and modified tandem waves. For a bubble of 0.07mm, our results indicate that the modified pressure profile enhances cavitation compared to conventional tandem waves at a wide range of delays (10-280μs). According to this, the proposed pressure profile could be more efficient for SWL than conventional tandem shock waves. Similar results were obtained for a ten times smaller bubble.

  7. A modified Kelvin impact model for pounding simulation of base-isolated building with adjacent structures

    NASA Astrophysics Data System (ADS)

    Ye, Kun; Li, Li; Zhu, Hongping

    2009-09-01

    Base isolation can effectively reduce the seismic forces on a superstructure, particularly in low- to medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the base-isolated building (BIB) and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference between the numerical results from the various impact analytical models is not significant. Many numerical simulations of BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drifts and floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the ground floor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible to pounding

  8. Evaluating and Modifying a Partially Double Moment Microphysics Scheme for Hurricane Simulations

    NASA Astrophysics Data System (ADS)

    Brown, B. R.; Bell, M. M.; Thompson, G.

    2016-12-01

    Accurately parameterized microphysical processes are integral to accurate tropical cyclone (TC) numerical predictions given that latent heat release is an important source of energy for TCs. Brown et al (2016, GRL) showed that the aerosol-aware Thompson scheme as implemented in the Weather Research and Forecasting (WRF) model version 3.6.1 produced more accurate TC intensity forecasts (as measured by maximum 10m wind speed) than other bulk microphysical parameterizations tested; however, there were clearly regions where the Thompson scheme overpredicted simulated differential reflectivity. Differential reflectivity, the difference between the horizontal and vertical reflectivity factors measured by dual-polarized radar, is dependent on the median drop size of a population of liquid drops. Here, we show that the relatively large differential reflectivity produced by the Thompson scheme is generally located in the stratiform regions in simulations of hurricanes Arthur and Ana (both 2014). In addition to evaluating the simulations against ground-based NEXRAD radar observations, we provide drop size distributions (DSD) estimates from the dual-frequency precipitation radar onboard the Global Precipitation Measurement (GPM) satellite. The vertical structure of the simulated differential reflectivity from rain suggests that melting snow or graupel is the source of increased median drop size of the DSDs in this case. Joint probability frequency distributions in horizontal and differential reflectivity space make a comprehensive microphysical evaluation straightforward as we modify the melting processes in the Thompson scheme to reduce the median drop size of the DSD in targeted regions of the phase space. We find that the joint probability distribution more closely resembles that from the radar observations as we increase the number of liquid particles resulting from the melting of snow, a process which contains several tunable parameters as the Thompson scheme is double

  9. Modified Motor Unit Number Index: A Simulation Study of the First Dorsal Interosseous Muscle

    PubMed Central

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

    2015-01-01

    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

  10. Performance of a 16.6 Meter Diameter Modified Ringsail Parachute in a Simulated Martian Environment

    NASA Technical Reports Server (NTRS)

    1968-01-01

    Performance of a 16.6 Meter Diameter Modified Ringsail Parachute in a Simulated Martian Environment. Inflation, drag, and stability characteristics of a 54.5 -foot nominal-diameter (16.6-meter) modified ringsail parachute deployed in the wake of a 15-foot-diameter (4.6-meter) spacecraft traveling at a Mach number of 1.6 and a dynamic pressure equal to 11.6 psf (555 N/m(exp 2)) were obtained from the third balloon-launched flight test of the Planetary Entry Parachute Program. After deployment, the parachute inflated rapidly to a full condition, partially collapsed, and reinflated to a stable configuration. After reinflation, an average drag coefficient near 0.6 based on nominal surface area was obtained. During descent, an aerodynamic trim angle was observed in a plane near several torn sails. Amplitude of the trim was approximately 15 degrees and oscillation about trim was less than 11 degrees. [Entire movie available on DVD from CASI as Doc ID 20070030996. Contact help@sti.nasa.gov

  11. Simulation and experiment research of face recognition with modified multi-method morphological correlation algorithm

    NASA Astrophysics Data System (ADS)

    Yang, Yu; Xuping, Zhang

    2007-03-01

    Morphological definition of similarity degree of gray-scale image and general definition of morphological correlation (GMC) are proposed. Hardware and software design for a compact joint transform correlator are presented in order to implement GMC. Two kinds of modified general morphological correlation algorithm are proposed. The gray-scale image is decomposed into a set of binary image slices in certain decomposition method. In the first algorithm, the edge of each binary joint image slice is detected, width adjustability of which is investigated, and the joint power spectrum of the edge is summed. In the second algorithm, the joint power spectrum of each pair is binarized or thinned and then summed in one situation, and the summation of the joint power spectrums of these pairs is binarized or thinned in the other situation. Computer-simulation results and real face image recognition results indicate that the modified algorithm can improve the discrimination capabilities with respect to the gray-scale face images of high similarity.

  12. The abundance of galaxy clusters in modified Newtonian dynamics: cosmological simulations with massive neutrinos

    NASA Astrophysics Data System (ADS)

    Angus, G. W.; Diaferio, Antonaldo

    2011-10-01

    We present a new particle mesh cosmological N-body code for accurately solving the modified Poisson equation of the quasi-linear formulation of modified Newtonian dynamics (MOND). We generate initial conditions for the Angus cosmological model, which is identical to Λ cold dark matter (ΛCDM) except that the CDM is switched for a single species of thermal sterile neutrinos. We set the initial conditions at z= 250 for a (512 Mpc h-1)3 box with 2563 particles, and we evolve them down to z= 0. We clearly demonstrate the ability of MOND to develop the large-scale structure in a hot dark matter cosmology and contradict the naive expectation that MOND cannot form galaxy clusters. We find that the correct order of magnitude of X-ray clusters (with TX > 4.5 keV) can be formed, but that we overpredict the number of very rich clusters and seriously underpredict the number of lower mass clusters. We present evidence that suggests the density profiles of our simulated clusters are compatible with those of the observed X-ray clusters in MOND. As a last test, we computed the relative velocity between pairs of haloes within 10 Mpc and find that pairs with velocities larger than 3000 km s-1, like the bullet cluster, can form without difficulty.

  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. Molecular dynamics simulations of AP/HMX composite with a modified force field.

    PubMed

    Zhu, Wei; Wang, Xijun; Xiao, Jijun; Zhu, Weihua; Sun, Huai; Xiao, Heming

    2009-08-15

    An all-atom force field for ammonium perchlorate (AP) is developed with the framework of pcff force field. The structural parameters of AP obtained with the modified force field are in good agreement with experimental values. Molecular dynamics (MD) simulations have been performed to investigate AP/HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) composite at different temperatures. The binding energies, thermal expansion coefficient, and the trigger bond lengths of HMX in the AP/HMX composite have been obtained. The binding energies of the system increase slightly with temperature increasing, peak at 245K, and then gradually decrease. The volume thermal expansion coefficient of the AP/HMX composite has been derived from the volume variation with temperature. As the temperature rises, the maximal lengths of the trigger bond N-NO(2) of HMX increase gradually. The simulated results indicate that the maximal length of trigger bond can be used as a criterion for judging the sensitivity of energetic composite.

  15. 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.

  16. 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

  17. 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. Copyright 2010 Elsevier Ltd. All

  18. 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.

  19. Removal of heavy metal Cu(II) in simulated aquaculture wastewater by modified palygorskite.

    PubMed

    Cao, Jia-Shun; Wang, Cheng; Fang, Fang; Lin, Jun-Xiong

    2016-12-01

    Palygorskite (PAL) is a good heavy metal adsorbent due to its high surface area, low cost, and environmentally compatibility. But the natural PAL has limited its adsorption capacity and selectivity. In this study, a cost-effective and readily-generated absorbent, l-threonine-modified palygorskite (L-PAL), was used and its performance for Cu(II) removal in simulated aquaculture wastewater was evaluated. After preparation, L-PAL was characterized by using Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis. The impacts of pH, adsorbent dosage, contact time, and initial Cu(II) concentration on the adsorption capacity of L-PAL were examined. The Cu(II) adsorption capacity on L-PAL was enhanced almost 10 times than that of raw PAL. The adsorption isotherms of Cu(II) fit the Langmuir isotherms, and the adsorption kinetics was dominated by the pseudo-second-order model. The thermodynamic parameters at four temperatures were calculated, which indicated that the adsorption was spontaneous and endothermic. The adsorption mechanism involves complexation, chelation, electrostatic attraction, and micro-precipitation. Furthermore, L-PAL is shown to have a high regeneration capacity. These results indicate that L-PAL is a cheap and promising absorbent for Cu(II) removal and hold potential to be used for aquaculture wastewater treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Characterizations of Bone-Like Apatite Powder Fabricated Using Modified Simulated Body Fluid.

    PubMed

    An, Ji-Hae; Han, Ok-Seong; Kohn, David H; Park, Yeong-Joon; Song, Ho-Jun

    2015-08-01

    The objective of this study is to fabricate bone-like apatite (BLAp) powder using the modified simulated body fluid (SBF). The SBF2X and SBF4X groups were prepared by increasing the concentration of inorganic ions by two and four times, respectively, to that of the standard SBF. The mSBF4X group was prepared by particularly increasing the concentrations of calcium and phosphate ions in SBF. Bovine serum albumin (BSA) was added for SBF2X-BSA, SBF4X-BSA, and mSBF4X-BSA groups. BLAp powders were precipitated in these SBFs while being kept at 60 °C. Micro-morphology of BLAp powders showed tens of micrometers-sized rounded clusters which composed with sheet-like nano crystallites. The radius of BLAp clusters were decreased by increasing the concentration of inorganic ions and by incorporating the BSA. The hydroxyapatite crystalline structure was dominant for all sample groups. Further, octacalcium phosphate structure was detected in the mSBF4X group. However, these peaks were decreased in mSBF4X-BSA. FT-IR spectra demonstrated that BSA was co-precipitated in BLAp crystallites, and the amount of BSA was higher in the mSBF4X-BSA group than in the SBF4X-BSA group.

  1. Controllable Nanoparticle Assembly and Actuation with Modified Dipole Potentials in Simulation

    NASA Astrophysics Data System (ADS)

    Dempster, Joshua

    Science at the nanoscale poses several recurring difficulties. How can we control the assembly of objects too small for direct manipulation to be practical? How can we extend that control to in vivo systems so we can make use of nanotechnology in medicine? And how can we recreate the extraordinary capacities of Nature: healing, replication, growth, adaptation, self-regulation? One of the most powerful tools for addressing these challenges is the simple, familiar dipole moment. Since their debut as fuel control devices at NASA in the early sixties, possible applications for dipole suspensions have grown to areas far beyond what their creators envisioned. A multitude of ambitious new medical and mechanical applications make use of dipolar colloids. Dipoles are attractive from a practical standpoint because one can use fields to control not just their orientation and location, but also their mutual interactions. From a physical standpoint, dipoles are compelling as an exceptionally simple form of symmetry-breaking that leads to a variety of complex phenomena. This thesis studies the assembly and control of spherical colloids with a dipolar interaction modified by additional conditions using simulations. Three cases are examined in detail. The first is the case of an electrical dipole moment created by regions of opposite charge density on the surface of a colloid. Here the dipole potential is modified by strong screening. Such a system is interesting as a model for certain proteins in a high-salt solution and suggests possible uses for inverse Janus colloids. The resulting phases have little resemblance to the usual dipole phases and can be controlled with small quantities of homogeneously charged particles. In the second case, superparamagnetic dipoles are linked into chains. Such chains have been realized in a wide variety of experimental schemes. A general theory is developed for the equilibrium shapes of the chains in a precessing field when their endpoints are

  2. Comparative assessment of surgeons' task performance and surgical ergonomics associated with conventional and modified flank positions: a simulation study.

    PubMed

    Fan, Yu; Kong, Gaiqing; Meng, Yisen; Tan, Shutao; Wei, Kunlin; Zhang, Qian; Jin, Jie

    2014-11-01

    Flank position is extensively used in retroperitoneoscopic urological practice. Most surgeons follow the patients' position in open approaches. However, surgical ergonomics of the conventional position in the retroperitoneoscopic surgery is poor. We introduce a modified position and evaluated task performance and surgical ergonomics of both positions with simulated surgical tasks. Twenty-one novice surgeons were recruited to perform four tasks: bead transfer, ring transfer, continuous suturing, and cutting a circle. The conventional position was simulated by setting an endo-surgical simulator parallel to the long axis of a surgical desk. The modified position was simulated by rotating the simulator 30° with respect to the long axis of the desk. The outcome measurements include task performance measures, kinematic measures for body alignment, surface electromyography, relative loading between feet, and subjective ratings of fatigue. We observed significant improvements in both task performance and surgical ergonomics parameters under the modified position. For all four tasks, subjects finished tasks faster with higher accuracy (p < 0.005 or < 0.001). For ergonomics part: (1) The angle between the upper body and the head was decreased by 7.4 ± 1.7°; (2) The EMG amplitude collected from shoulders and left lumber was significantly lower (p < 0.05); (3) Relative loading between feet was more balanced (p < 0.001); (4) Manual-action muscles and postural muscles are rated less fatiguing according to the questionnaire (p < 0.05). Conventional position of patient in retroperitoneoscopic upper urinary tract surgery is associated with poor surgical ergonomics. With a simulated surgery, we demonstrated that our modified position could significantly improve task performance and surgical ergonomics. Further studies are still warranted to validate these benefits for both patients and surgeons.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26086702

  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. 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.

  7. Redfield Ratios in Inland Waters: Higher Biological Control of C:N:P Ratios in Tropical Semi-arid High Water Residence Time Lakes

    PubMed Central

    They, Ng H.; Amado, André M.; Cotner, James B.

    2017-01-01

    The canonical Redfield C:N:P ratio for algal biomass is often not achieved in inland waters due to higher C and N content and more variability when compared to the oceans. This has been attributed to much lower residence times and higher contributions of the watershed to the total organic matter pool of continental ecosystems. In this study we examined the effect of water residence times in low latitude lakes (in a gradient from humid to a semi-arid region) on seston elemental ratios in different size fractions. We used lake water specific conductivity as a proxy for residence time in a region of Eastern Brazil where there is a strong precipitation gradient. The C:P ratios decreased in the seston and bacterial size-fractions and increased in the dissolved fraction with increasing water retention time, suggesting uptake of N and P from the dissolved pool. Bacterial abundance, production and respiration increased in response to increased residence time and intracellular nutrient availability in agreement with the growth rate hypothesis. Our results reinforce the role of microorganisms in shaping the chemical environment in aquatic systems particularly at long water residence times and highlights the importance of this factor in influencing ecological stoichiometry in all aquatic ecosystems. PMID:28848518

  8. Redfield Ratios in Inland Waters: Higher Biological Control of C:N:P Ratios in Tropical Semi-arid High Water Residence Time Lakes.

    PubMed

    They, Ng H; Amado, André M; Cotner, James B

    2017-01-01

    The canonical Redfield C:N:P ratio for algal biomass is often not achieved in inland waters due to higher C and N content and more variability when compared to the oceans. This has been attributed to much lower residence times and higher contributions of the watershed to the total organic matter pool of continental ecosystems. In this study we examined the effect of water residence times in low latitude lakes (in a gradient from humid to a semi-arid region) on seston elemental ratios in different size fractions. We used lake water specific conductivity as a proxy for residence time in a region of Eastern Brazil where there is a strong precipitation gradient. The C:P ratios decreased in the seston and bacterial size-fractions and increased in the dissolved fraction with increasing water retention time, suggesting uptake of N and P from the dissolved pool. Bacterial abundance, production and respiration increased in response to increased residence time and intracellular nutrient availability in agreement with the growth rate hypothesis. Our results reinforce the role of microorganisms in shaping the chemical environment in aquatic systems particularly at long water residence times and highlights the importance of this factor in influencing ecological stoichiometry in all aquatic ecosystems.

  9. 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.

  10. Simulation and Testing of a Linear Array of Modified Four-Square Feed Antennas for the Tianlai Cylindrical Radio Telescope

    NASA Astrophysics Data System (ADS)

    Cianciara, Aleksander J.; Anderson, Christopher J.; Chen, Xuelei; Chen, Zhiping; Geng, Jingchao; Li, Jixia; Liu, Chao; Liu, Tao; Lu, Wing; Peterson, Jeffrey B.; Shi, Huli; Steffel, Catherine N.; Stebbins, Albert; Stucky, Thomas; Sun, Shijie; Timbie, Peter T.; Wang, Yougang; Wu, Fengquan; Zhang, Juyong

    A wide bandwidth, dual polarized, modified four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical reflectors for Tianlai, a radio interferometer designed for 21cm intensity mapping. Simulations of the feed antenna beam patterns and scattering parameters are compared to experimental results at multiple frequencies across the 650-1420MHz range. Simulations of the beam patterns of the combined feed array/reflector are presented as well.

  11. Numerical simulating the two-dimensional structure of the Penning discharge using the modified drift-diffusion model

    NASA Astrophysics Data System (ADS)

    Surzhikov, S. T.

    2017-02-01

    Spatial structure of the Penning discharge at pressures p = 0.1 - 0.01 Torr is investigated within the framework of the modified drift-diffusion model. This modification includes three models of elementary physical processes, which take into account peculiarities of gas discharge processes at low pressures and large reduced electric fields. Presented results of numerical simulations are in reasonable agreement with available experimental data.

  12. A review on the application of modified continuum models in modeling and simulation of nanostructures

    NASA Astrophysics Data System (ADS)

    Wang, K. F.; Wang, B. L.; Kitamura, T.

    2016-02-01

    Analysis of the mechanical behavior of nanostructures has been very challenging. Surface energy and nonlocal elasticity of materials have been incorporated into the traditional continuum analysis to create modified continuum mechanics models. This paper reviews recent advancements in the applications of such modified continuum models in nanostructures such as nanotubes, nanowires, nanobeams, graphenes, and nanoplates. A variety of models for these nanostructures under static and dynamic loadings are mentioned and reviewed. Applications of surface energy and nonlocal elasticity in analysis of piezoelectric nanomaterials are also mentioned. This paper provides a comprehensive introduction of the development of this area and inspires further applications of modified continuum models in modeling nanomaterials and nanostructures.

  13. SED-ML web tools: generate, modify and export standard-compliant simulation studies.

    PubMed

    Bergmann, Frank T; Nickerson, David; Waltemath, Dagmar; Scharm, Martin

    2017-04-15

    The Simulation Experiment Description Markup Language (SED-ML) is a standardized format for exchanging simulation studies independently of software tools. We present the SED-ML Web Tools, an online application for creating, editing, simulating and validating SED-ML documents. The Web Tools implement all current SED-ML specifications and, thus, support complex modifications and co-simulation of models in SBML and CellML formats. Ultimately, the Web Tools lower the bar on working with SED-ML documents and help users create valid simulation descriptions. http://sysbioapps.dyndns.org/SED-ML_Web_Tools/ . fbergman@caltech.edu .

  14. Application of modified integration rule to time-domain finite-element acoustic simulation of rooms.

    PubMed

    Okuzono, Takeshi; Otsuru, Toru; Tomiku, Reiji; Okamoto, Noriko

    2012-08-01

    The applicability of the modified integration rule for time-domain finite-element analysis is tested in sound field analysis of rooms involving rectangular elements, distorted elements, and finite impedance boundary conditions. Dispersion error analysis in three dimensions is conducted to evaluate the dispersion error in time-domain finite-element analysis using eight-node hexahedral elements. The results of analysis confirmed that fourth-order accuracy with respect to dispersion error is obtainable using the Fox-Goodwin method (FG) with a modified integration rule, even for rectangular elements. The stability condition in three-dimensional analysis using the modified integration rule is also presented. Numerical experiments demonstrate that FG with a modified integration rule performs much better than FG with the conventional integration rule for problems with rectangular elements, distorted elements, and with finite impedance boundary conditions. Further, as another advantage, numerical results revealed that the use of modified integration rule engenders faster convergence of the iterative solver than a conventional rule for problems with the same degrees of freedom.

  15. Modified Approach for Robotic Retroauricular Thyroidectomy: Preclinical Simulation and a Surgical Case.

    PubMed

    Saeed, Ahmad; Alsaleh, Nuha; Moulthrop, Thomas; Aslam, Rizwan; Kandil, Emad

    2015-12-01

    Recently, a single remote access retroauricular robotic technique has been described for thyroid lobectomy. We aimed to explore the feasibility and safety of modifying this novel approach using preclinical cadaver model followed by performing the same operation in a real patient. The modified retroauricular approach was performed by creating a working space between the 2 heads of the sternocleidomastoid muscle, instead of that anterior to muscle. This was performed to create a wider working space. Two operations were initially performed in human cadavers. Subsequently, robotic-assisted thyroid lobectomy was performed using this novel modified retroauricular approach. Robotic-assisted hemithyroidectomy was performed successfully in 2 cadavers and subsequently in one patient using modified approach. The patient was discharged on the same day of surgery and had no complications. The modified retroauricular approach with creation of a working space between the 2 heads of sternocleidomastoid muscle is safe and feasible, and offers a wider working space for robotic thyroid surgery. © The Author(s) 2014.

  16. Fluid Structure Modeling and SImulation of a Modified KC-135R Icing Tanker Boom

    DTIC Science & Technology

    2013-01-07

    Airborne Icing Tanker (AIT) boom system to provide an aeroelastic modeling and simulation (M&S) capability to complement flight test. The AIT boom system...Aerodynamics, Aeroelasticity , Modeling and Simulation 16. SECURITY CLASSIFICATION OF: Unclassified 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a...boom system to provide an aeroelastic modeling and simulation (M&S) capability to complement flight test. The AIT boom system is a KC-135R air- craft

  17. Fluid-Structure Modeling and Simulation of a Modified KC-135R Icing Tanker Boom

    DTIC Science & Technology

    2013-01-07

    Airborne Icing Tanker (AIT) boom system to provide an aeroelastic modeling and simulation (M&S) capability to complement flight test. The AIT boom system...Aerodynamics, Aeroelasticity , Modeling and Simulation 16. SECURITY CLASSIFICATION OF: Unclassified 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a...boom system to provide an aeroelastic modeling and simulation (M&S) capability to complement flight test. The AIT boom system is a KC-135R air- craft

  18. Process simulation of modified dry grind ethanol plant with recycle of pretreated and enzymatically hydrolyzed distillers' grains.

    PubMed

    Kim, Youngmi; Mosier, Nathan; Ladisch, Michael R

    2008-08-01

    Distillers' grains (DG), a co-product of a dry grind ethanol process, is an excellent source of supplemental proteins in livestock feed. Studies have shown that, due to its high polymeric sugar contents and ease of hydrolysis, the distillers' grains have potential as an additional source of fermentable sugars for ethanol fermentation. The benefit of processing the distillers' grains to extract fermentable sugars lies in an increased ethanol yield without significant modification in the current dry grind technology. Three different potential configurations of process alternatives in which pretreated and hydrolyzed distillers' grains are recycled for an enhanced overall ethanol yield are proposed and discussed in this paper based on the liquid hot water (LHW) pretreatment of distillers' grains. Possible limitations of each proposed process are also discussed. This paper presents a compositional analysis of distillers' grains, as well as a simulation of the modified dry grind processes with recycle of distillers' grains. Simulated material balances for the modified dry grind processes are established based on the base case assumptions. These balances are compared to the conventional dry grind process in terms of ethanol yield, compositions of its co-products, and accumulation of fermentation inhibitors. Results show that 14% higher ethanol yield is achievable by processing and hydrolyzing the distillers' grains for additional fermentable sugars, as compared to the conventional dry grind process. Accumulation of fermentation by-products and inhibitory components in the proposed process is predicted to be 2-5 times higher than in the conventional dry grind process. The impact of fermentation inhibitors is reviewed and discussed. The final eDDGS (enhanced dried distillers' grains) from the modified processes has 30-40% greater protein content per mass than DDGS, and its potential as a value-added process is also analyzed. While the case studies used to illustrate the

  19. Numerical Simulation of the Microtron Electron Beam Absorption by the Modified ABS-Plastic

    NASA Astrophysics Data System (ADS)

    Stuchebrov, S. G.; Miloichikova, I. A.; Melnikov, A. L.; Pereverzeva, M. A.

    2016-01-01

    Each specific task of the electron beam application imposes requirements for the beam profile and shape. One of the methods allows achieving high accuracy and low cost of the filters production is the 3D print method. The required properties of the electron beam interaction with the material can be achieved by using the modified plastic filaments. In this paper, the results of the model creation of the electron beams interaction with the ABS-plastic doped with different concentrations are presented. The depth dose distributions of the electron beam in the modified ABS-plastic are sown. The electron beam profiles and the electron beam distribution in the modified ABS-plastic are illustrated.

  20. 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.

  1. Modified MODFLOW-based model for simulating the agglomeration and transport of polymer-modified Fe(0) nanoparticles in saturated porous media.

    PubMed

    Babakhani, Peyman; Fagerlund, Fritjof; Shamsai, Abolfazl; Lowry, Gregory V; Phenrat, Tanapon

    2015-08-25

    The solute transport model MODFLOW has become a standard tool in risk assessment and remediation design. However, particle transport models that take into account both particle agglomeration and deposition phenomena are far less developed. The main objective of the present study was to evaluate the feasibility of adapting the standard code MODFLOW/MT3D to simulate the agglomeration and transport of three different types of polymer-modified nanoscale zerovalent iron (NZVI) in one-dimensional (1-D) and two-dimensional (2-D) saturated porous media. A first-order decay of the particle population was used to account for the agglomeration of particles. An iterative technique was used to optimize the model parameters. The model provided good matches to 1-D NZVI-breakthrough data sets, with R (2) values ranging from 0.96 to 0.99, and mass recovery differences between the experimental results and simulations ranged from 0.1 to 1.8 %. Similarly, simulations of NZVI transport in the heterogeneous 2-D model demonstrated that the model can be applied to more complicated heterogeneous domains. However, the fits were less good, with the R (2) values in the 2-D modeling cases ranging from 0.75 to 0.95, while the mass recovery differences ranged from 0.7 to 6.5 %. Nevertheless, the predicted NZVI concentration contours during transport were in good agreement with the 2-D experimental observations. The model provides insights into NZVI transport in porous media by mathematically decoupling agglomeration, attachment, and detachment, and it illustrates the importance of each phenomenon in various situations. Graphical Abstract ᅟ.

  2. 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.

  3. Experimental Simulation in Introductory Sociology: Modifying EXPER-SIM to Meet the Needs of Beginners.

    ERIC Educational Resources Information Center

    Conklin, George H.

    Introductory social science courses could benefit from introducing experiment simulation into the curriculum via the computer. Properly used, the computer should enable the instructor to include the benefits of the laboratory at a reasonable cost into a pre-existing course. The EXPER-SIM (Experiment Simulation) program was combined with PROFIS, a…

  4. Modified symplectic schemes with nearly-analytic discrete operators for acoustic wave simulations

    NASA Astrophysics Data System (ADS)

    Liu, Shaolin; Yang, Dinghui; Lang, Chao; Wang, Wenshuai; Pan, Zhide

    2017-04-01

    Using a structure-preserving algorithm significantly increases the computational efficiency of solving wave equations. However, only a few explicit symplectic schemes are available in the literature, and the capabilities of these symplectic schemes have not been sufficiently exploited. Here, we propose a modified strategy to construct explicit symplectic schemes for time advance. The acoustic wave equation is transformed into a Hamiltonian system. The classical symplectic partitioned Runge-Kutta (PRK) method is used for the temporal discretization. Additional spatial differential terms are added to the PRK schemes to form the modified symplectic methods and then two modified time-advancing symplectic methods with all of positive symplectic coefficients are then constructed. The spatial differential operators are approximated by nearly-analytic discrete (NAD) operators, and we call the fully discretized scheme modified symplectic nearly analytic discrete (MSNAD) method. Theoretical analyses show that the MSNAD methods exhibit less numerical dispersion and higher stability limits than conventional methods. Three numerical experiments are conducted to verify the advantages of the MSNAD methods, such as their numerical accuracy, computational cost, stability, and long-term calculation capability.

  5. Simulation of Couette flow using conventional Burnett equations with modified slip boundary conditions

    NASA Astrophysics Data System (ADS)

    Liu, Hualin; Zhao, Wenwen; Chen, Weifang

    2016-11-01

    Gas or liquid flow through small channels has become more and more popular due to the micro-electro-mechanical systems (MEMS) fabrication technologies such as micro-motors, electrostatic comb-drive, micro-chromatographs, micro-actuators, micro-turbines and micro-pumps, etc. The flow conditions in and around these systems are always recognized as typical transitional regimes. Under these conditions, the mean free path of gas molecules approaches the characteristic scale of the micro-devices itself, and due to the little collisions the heat and momentum cannot equilibrate between the wall and fluids quickly. Couette flow is a simple and critical model in fluid dynamics which focuses on the mechanism of the heat transfer in shear-driven micro-cavities or micro-channels. Despite numerous work on the numerical solutions of the Couette flow, how to propose stable and accurate slip boundary conditions in rarefied flow conditions still remains to be elucidated. In this paper, converged solutions for steady-state micro Couette flows are obtained by using conventional Burnett equations with a set of modified slip boundary conditions. Instead of using the physical variables at the wall, the modified slip conditions use the variables at the edge of the Knudsen layer based on a physically plausible assumption in literature that Knudsen layer has a thickness only in the order of a mean free path and molecules are likely to travel without collision in this layer. Numerical results for non-dimensional wall shear stress and heat flux are compared with those of the DSMC solutions. Although there are not much improvement in the accuracy by using this modified slip conditions, the modified conditions perform much better than the unmodified slip conditions for numerical stabilization. All results show that the set of conventional Burnett equations with second order modified conditions are proved to be an appropriate model for the micro-Couette flows.

  6. 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.

  7. 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

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

    PubMed

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

    2015-02-21

    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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Effect of hydrophobic groups on the adsorption conformation of modified polycarboxylate superplasticizer investigated by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zhao, Hongxia; Wang, Yanwei; Yang, Yong; Shu, Xin; Yan, Han; Ran, Qianping

    2017-06-01

    All-atom molecular dynamics (MD) simulations were used to study the adsorption conformations of hydrophobically-modified comb-shaped polycarboxylate ether-based (PCE) superplasticizer molecules on a model surface of dicalcium silicate (C2S) in vacuum and in an explicit solution, respectively. Three different hydrophobic modifying groups, namely, the ethyl group, the n-butyl group and the phenyl group, decorated to the backbone, were examined. Comparing the hydrophobically-modified PCEs to the unmodified one, differences were found in the binding energy, the adsorption conformation and the water density at the interface. The interaction between PCE molecules and C2S was weakened in a solution with explicit solvents than that obtained from vacuum-based simulations. The presence of hydrophobic groups lowered the polymer-surface binding energy, decreased the radius of gyration (Rg) of the adsorbed polymer, increased the peak position in the heavy-atom density profiles in the direction perpendicular to the surface, and also caused the adsorbed conformations to be more globular in shape. The parallel and perpendicular components (relative to the surface plane) of the geometric sizes of the adsorbed polymers were calculated, and the results showed that the presence of hydrophobically modifying groups decreased the in-plane radius while increased the adsorption layer thickness compared to the unmodified control. The presence of PCEs perturbed the dense water layer above the C2S surface and lowered the water density. Perturbations to the interfacial water density were found to correlate nicely with the adsorbed conformations of PCEs.

  14. A modified Picard iteration scheme for overcoming numerical difficulties of simulating infiltration into dry soil

    NASA Astrophysics Data System (ADS)

    Zha, Yuanyuan; Yang, Jinzhong; Yin, Lihe; Zhang, Yonggen; Zeng, Wenzhi; Shi, Liangsheng

    2017-08-01

    Numerical models based on Richards' equation are often employed to simulate the soil water dynamics. Among them, those Picard iteration models which use the head as primary variable are widely adopted due to their simplicity and capability for handling partially saturated flow conditions. However, it is well-known that those models are prone to convergence failure in some unfavorable flow conditions, especially when simulating infiltration into initially dry soils. Here we analyze the reasons that give rise to the numerical difficulty. Moreover, several modifications to the mass-conservative Picard iteration method are proposed so that numerical difficulty is avoided in these unfavorable flow conditions. Our proposed modifications do not degrade the simulated results, while they lead to more robust convergence performances and cost-effective simulations.

  15. A research on short-term hydro-wind economic dispatch problem simulated with a modified differential evolution algorithm

    NASA Astrophysics Data System (ADS)

    Xuemin, Wang; Anqiang, Li; Rui, Zhang

    2017-05-01

    Due to the wide construction of wind power and the difficulty for it to join the power grid, a short-term hydro-wind economic dispatch (WHED) problem is proposed. WHED system contains several wind power units and hydropower plants, which are renewable and clean. Combined with hydropower plants, the wind power units can join the power grid stably. Then, a WHED system with four cascaded hydropower plants and two wind units is established, and a modified differential evolution (DE) algorithm with chaotic perturbation is proposed for optimizing. Finally, two cases are simulated and analysed, the dispatch results show that the presented model and algorithm are feasible and effective.

  16. Application of modified difference absorption method to stand-off detection of alcohol in simulated car cabins

    NASA Astrophysics Data System (ADS)

    Kubicki, Jan; Młyńczak, Jaroslaw; Kopczyński, Krzysztof

    2013-01-01

    Some aspects of stand-off detection of alcohol in simulated car cabins are described. The proposed method is the well-known "difference absorption" method applied to the differential absorption lidar system, modified by taking advantage of a third laser beam. The modification was motivated by the familiar physical phenomena such as dispersion and different absorption coefficients in window panes for applied laser wavelengths. The mathematical expressions for the method were derived and confirmed by experiments. The presented investigations indicate that the method can be successfully applied to stand-off detection of ethyl alcohol in moving cars.

  17. 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).

  18. Brownian dynamics simulation of the cross-talking effect among modified histones on conformations of nucleosomes

    NASA Astrophysics Data System (ADS)

    Duan, Zhao-Wen; Li, Wei; Xie, Ping; Dou, Shuo-Xing; Wang, Peng-Ye

    2010-04-01

    Using Brownian dynamics simulation, we studied the effect of histone modifications on conformations of an array of nucleosomes in a segment of chromatin. The simulation demonstrated that the segment of chromatin shows the dynamic behaviour that its conformation can switch between a state with nearly all of the histones being wrapped by DNA and a state with nearly all of the histones being unwrapped by DNA, thus involving the “cross-talking" interactions among the histones. Each state can stay for a sufficiently long time. These conformational states are essential for gene expression or gene silence. The simulation also shows that these conformational states can be inherited by the daughter DNAs during DNA replication, giving a theoretical explanation of the epigenetic phenomenon.

  19. 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.

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

    PubMed

    Zhao, Qian; Burns, Susan E

    2012-04-03

    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

  1. Revisiting the concept of Redfield ratios applied to plankton stoichiometry - Addressing model uncertainties with respect to the choice of C:N:P ratios for phytoplankton

    NASA Astrophysics Data System (ADS)

    Kreus, Markus; Paetsch, Johannes; Grosse, Fabian; Lenhart, Hermann; Peck, Myron; Pohlmann, Thomas

    2017-04-01

    Ongoing Ocean Acidification (OA) and climate change related trends impact on physical (temperature), chemical (CO2 buffer capacity) and biological (stoichiometric) properties of the marine environment. These threats affect the global ocean but they appear particularly pronounced in marginal and shelf seas. Marine biogeochemical models are often used to investigate the impacts of climate change and changes in OA on the marine system as well as its exchange with the atmosphere. Different studies showed that both the structural composition of the models and the elemental ratios of particulate organic matter in the surface ocean affect the key processes controlling the ocean's efficiency storing atmospheric excess carbon. Recent studies focus on the variability of the elemental ratios of phytoplankton and found that the high plasticity of C:N:P ratios enables the storage of large amounts of carbon by incorporation into carbohydrates and lipids. Our analysis focuses on the North Sea, a temperate European shelf sea, for the period 2000-2014. We performed an ensemble of model runs differing only in phytoplankton stoichiometry, representing combinations of C:P = [132.5, 106, 79.5] and N:P=[20, 16, 12] (i.e., Redfield ratio +/- 25%). We examine systematically the variations in annual averages of net primary production (NPP), net ecosystem production in the upper 30 m (NEP30), export production below 30 m depth (EXP30), and the air-sea flux of CO2 (ASF). Ensemble average fluxes (and standard deviations) resulted in NPP = 15.4 (2.8) mol C m-2 a-1, NEP30 = 5.4 (1.1) mol C m-2 a-1, EXP30 = 8.1 (1.1) mol C m-2 a-1 and ASF = 1.1 (0.5) mol C m-2 a-1. All key parameters exhibit only minor variations along the axis of constant C:N, but correlate positively with increasing C:P and decreasing N:P ratios. Concerning regional differences, lowest variations in local fluxes due to different stoichiometric ratios can be found in the shallow southern and coastal North Sea. Highest

  2. A modified Lagrangian-volumes method to simulate chemical transport in heterogeneous porous media

    NASA Astrophysics Data System (ADS)

    de Dreuzy, J.; Davy, P.

    2008-12-01

    Transport in subsurface environments is conditioned by physical and chemical processes in interaction, the most common being advection and dispersion for the physical processes and sorption for chemical reactions. Several numerical approaches have been developed to solve the complex set of equations governing this type of solute transport. These methods become time consuming in highly heterogeneous porous media having a broad-range velocity distribution. In this paper; we discuss a new efficient Lagrangian method. This method, modified from the Lagrangian-volumes approach, consists in dividing the aqueous phase in elementary volumes moved with the flow and interacting with the solid phase. Like in continuous time random walk algorithms, rather than keeping a constant time step, the time is adapted to the mesh velocity and computed so that an elementary volume crosses a mesh in a single numerical step. The modified Lagrangian-volume approach remains thus efficient whatever the velocity field. This approach is also highly flexible as it achieves a decoupling of the physical and chemical processes at the elementary volume scale, i.e. at the lowest considered scale, giving way to model virtually all possible chemical reactions. The modified Lagrangian volume approach can model both reactions between species in solution and sorption reactions. Reactions in solution are modeled by exchanges of solutes between Lagrangian volumes. For sorption reactions, the surface-to-volume ratio variability, a key parameter of sorption reactions, is accounted for by deforming the shape of the elementary volume. We implement and validate the algorithm on the specific case of the nonlinear Freundlich kinetic sorption in highly heterogeneous lognormal and multifractal permeability fields.

  3. Evolution of stress concentration along curvilinear modified surface layer—base material interface. Numerical simulation

    NASA Astrophysics Data System (ADS)

    Balokhonov, Ruslan R.; Martynov, Sergei A.; Romanova, Varvara A.; Batukhtina, Ekaterina E.

    2015-10-01

    The interfacial mechanisms of the stress concentration in materials with modified surface layers are investigated. A dynamic boundary-value problem in a plane-strain formulation is solved numerically by the finite-difference method. Serrated and wavy base material-surface layer interfaces observed experimentally are assigned explicitly in calculations. Two stages in the evolution of the stress concentration are found to occur due to irregular interfacial geometry. The stress concentration in near-interfacial regions turns out to depend on the sinusoidal wavy interface thickness and roughness.

  4. MD simulations of HIV-1 RT primer-template complex: effect of modified nucleosides and antisense PNA oligomer.

    PubMed

    Uppuladinne, Mallikarjunachari V N; Sonavane, Uddhavesh B; Joshi, Rajendra R

    2013-01-01

    Human immunodeficiency virus type 1 (HIV-1) requires the human tRNA(3)(Lys) as a reverse transcriptase (RT) primer. The annealing of 3' terminal 18 nucleotides of tRNA(3)(Lys) with the primer binding site (PBS) of viral RNA (vRNA) is crucial for reverse transcription. Additional contacts between the A rich (A-loop) region of vRNA and the anticodon domain of tRNA(3)(Lys) are necessary, which show the specific requirement of tRNA(3)(Lys). The importance of modified nucleosides, present in tRNA(3)(Lys), in giving stability to the primer-template complex has been determined in earlier experiments. It has been observed that the PNA oligomer targeted to PBS of vRNA destabilized the crucial interactions between primer and template due to which the reverse transcription is inhibited. Molecular dynamics simulations have been carried out to study the effect of modified nucleosides on the vRNA-tRNA(3)(Lys) complex stability and the destabilization effect of PNA oligomer on the vRNA-tRNA(3)(Lys)-PNA complex. The root-mean-square deviation, hydrogen bonding, tertiary interactions, and free energy calculations of the simulation data support the experimental results. The analyses have revealed the structural changes in PBS region of vRNA which might be another strong reason for the inability of RT binding to 7F helix for its normal functioning of reverse transcription.

  5. Dielectric permittivity simulation of random irregularly shaped particle composites and approximation using modified dielectric mixing laws

    NASA Astrophysics Data System (ADS)

    Calame, J. P.

    2008-12-01

    Finite difference quasielectrostatic modeling is used to predict the dielectric permittivity of composites consisting of irregular particles in a background matrix. Representations of particles having undulating surfaces described by sums of harmonic functions are created on the computer and subsequently packed into a three-dimensional cellular model space. Composite dielectric permittivities as a function of volumetric filling fraction and particle undulation amplitude were simulated using constituent permittivities similar to the low-field behavior of barium titanium oxide (particles) and polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (terpolymer matrix). An increase in particle roughness (undulation amplitude) causes a more rapid increase in composite permittivity than that predicted by random spherical particle simulations. The dielectric behavior of irregular particle composites is also simulated over a wide range of ratios of particle permittivity to matrix permittivity, where both permittivities are purely real. An empirical mixing law, which is a modification of the Hanai equation with an exponent 1/μ instead of 1/3, is investigated and found to be in excellent agreement with the simulations. Additional empirical expressions that provide approximate values of μ in terms of the particle undulation amplitude and the ratio of constituent permittivities are developed. Together, the empirical expressions are potentially useful as a predictive mixing law for irregular particle systems.

  6. Modifying WEPP to improve streamflow simulation in a Pacific Northwest watershed

    Treesearch

    A. Srivastava; M. Dobre; J. Q. Wu; W. J. Elliot; E. A. Bruner; S. Dun; E. S. Brooks; I. S. Miller

    2013-01-01

    The assessment of water yield from hillslopes into streams is critical in managing water supply and aquatic habitat. Streamflow is typically composed of surface runoff, subsurface lateral flow, and groundwater baseflow; baseflow sustains the stream during the dry season. The Water Erosion Prediction Project (WEPP) model simulates surface runoff, subsurface lateral flow...

  7. Evaluating Forest Vegetation Simulator predictions for southern Appalachian upland hardwoods with a modified mortality model

    Treesearch

    Philip J. Radtke; Nathan D. Herring; David L. Loftis; Chad E. Keyser

    2012-01-01

    Prediction accuracy for projected basal area and trees per acre was assessed for the growth and yield model of the Forest Vegetation Simulator Southern Variant (FVS-Sn). Data for comparison with FVS-Sn predictions were compiled from a collection of n

  8. 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.

  9. Simulation of Maneuvering Characteristics of a Destroyer Study Ship Using a Modified Nonlinear Model.

    DTIC Science & Technology

    propulsion machinery dynamics and the ship equations of motion. The model couples the ship propulsion dynamics equations with nonlinear maneuvering...This report describes an analog computer maneuvering simulation of a destroyer study ship. The mathematical model which is used includes the ship

  10. Numerical simulation of supersonic jet flow using a modified k-ɛ model

    NASA Astrophysics Data System (ADS)

    Tandra, D. S.; Kaliazine, A.; Cormack, D. E.; Tran, H. N.

    2006-01-01

    Many papers have reported that the standard k-ɛ model fails to accurately predict the mean velocity profile of turbulent axisymmetric jets (Thies and Tam, Computation of turbulent axisymmetric and nonaxisymmetric jet flows using the K-ɛ model, AIAA J., 1996, 34(2), 309 316; Pope, Turbulent Flows, 2002 (Cambridge University press: Cambridge). As the jet velocity increases, the deviation of the model with respect to the experimental measurements also increases. This work is aimed at the development of a modified k-ɛ model that can be used to predict the mean properties of an axisymmetric jet as it (i) flows as a free jet, (ii) propagates between walls, and (iii) impinges on a solid object. Three additional terms are proposed to improve the standard k-ɛ model predictions. They are Durbin realizable, Heinz turbulence production and Sarkar compressibility correction terms. The performance of the modified model in predicting the velocity and the impact pressure profiles of a free jet with an exit Mach number range of 0.6 2.8 has been confirmed by its close agreement with the experimental measurements. In addition, the study suggests that the model is also capable of predicting the impact pressure of a supersonic jet propagating between smooth walls and impinging on the front edge of the wall in various degrees of intensity.

  11. Mercury adsorption of modified mulberry twig chars in a simulated flue gas.

    PubMed

    Shu, Tong; Lu, Ping; He, Nan

    2013-05-01

    Mulberry twig chars were prepared by pyrolysis, steam activation and impregnation with H2O2, ZnCl2 and NaCl. Textural characteristics and surface functional groups were performed using nitrogen adsorption and FTIR, respectively. Mercury adsorption of different modified MT chars was investigated in a quartz fixed-bed absorber. The results indicated that steam activation and H2O2-impregnation can improve pore structure significantly and H2O2-impregnation and chloride-impregnation promote surface functional groups. However, chloride-impregnation has adverse effect on pore structure. Mercury adsorption capacities of impregnated MT chars with 10% or 30% H2O2 are 2.02 and 1.77 times of steam activated MT char, respectively. Mercury adsorption capacity of ZnCl2-impregnated MT char increase with increasing ZnCl2 content and is better than that of NaCl-impregnated MT char at the same chloride content. The modified MT char (MT873-A-Z5) prepared by steam activation following impregnation with 5% ZnCl2 exhibits a higher mercury adsorption capacity (29.55 μg g(-1)) than any other MT chars.

  12. Toxicity of Modified HL Simulant and Methyl Salicylate in Soil on Cucumbers and Earthworms

    DTIC Science & Technology

    1993-04-01

    SUBJECT TERMS 15. NUMBER OF PAGES HL simulant Terrestrial plants 32 Phytotoxicity Earthworms (Eisenia foetida ) 16. PRICE CODE Methyl salicylate...hazards of chemicals to these nontarget organisms. Heimbach 4 compared laboratory methods using Eisenia foetida and Lumbricus terrestris to assess the...hazards of chemicals to earthworms in an artificial soil. Based on this review, Heimbach recommended that Eisenia foetida be used as a representative

  13. Numerical simulation for peristaltic activity of Sutterby fluid with modified Darcy's law

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Ayub, S.; Alsaedi, A.; Tanveer, A.; Ahmad, B.

    The current work examines the peristaltic flow of Sutterby fluid in a planar symmetric channel. Electrically conducting fluid is considered via imposed magnetic field. An incompressible Sutterby fluid saturates the porous medium. Modified Darcy's law has been employed for the porous medium effect. The channel walls are compliant. Convective conditions of heat and mass transfer are imposed. Viscous dissipation and Joule heating are retained. Problem for large wavelength are numerically solved. The graphs are obtained for the velocity, temperature, concentration and heat transfer rate. Velocity and concentration profiles are observed to have opposite behavior for increasing Darcy number. It is found that the effect of Hartman number on the velocity and temperature profiles is similar. Further heat transfer coefficient strengthened when heat transfer Biot number is increased.

  14. 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.

  15. Analytical simulation of water system capacity reliability, 1. Modified frequency-duration analysis

    NASA Astrophysics Data System (ADS)

    Hobbs, Benjamin F.; Beim, Gina K.

    1988-09-01

    The problem addressed is the computation of the unavailability and expected unserved demand of a water supply system having random demand, finished water storage, and unreliable capacity components. Examples of such components include pumps, treatment plants, and aqueducts. Modified frequency-duration analysis estimates these reliability statistics by, first, calculating how often demand exceeds available capacity and, second, comparing the amount of water in storage with how long such capacity deficits last. This approach builds upon frequency-duration methods developed by the power industry for analyzing generation capacity deficits. Three versions of the frequency-duration approach are presented. Two yield bounds to system unavailability and unserved demand and the third gives an estimate of their true values between those bounds.

  16. Generation and computerized simulation of meshing and contact of modified involute helical gears

    NASA Astrophysics Data System (ADS)

    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.

  17. Performance of a 16.6 Meter Diameter Modified Ringsail Parachute in a Simulated Martian Environment

    NASA Technical Reports Server (NTRS)

    Whitlock, Charles H.; Henning, Allen B.; Coltrane, Lucille C.

    1968-01-01

    Inflation, drag, and stability characteristics of a 54.5 -foot nominal-diameter (16.6-meter) modified ringsail parachute deployed in the wake of a 15-foot-diameter (4.6-meter) spacecraft traveling at a Mach number of 1.6 and a dynamic pressure equal to 11.6 psf (555 N/m(exp 2)) were obtained from the third balloon-launched flight test of the Planetary Entry Parachute Program. After deployment, the parachute inflated rapidly to a full condition, partially collapsed, and reinflated to a stable configuration. After reinflation, an average drag coefficient near 0.6 based on nominal surface area was obtained. During descent, an aerodynamic trim angle was observed in a plane near several torn sails. Amplitude of the trim was approximately 15 degrees and oscillation about trim was less than 11 degrees.

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

    DOE PAGES

    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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Comparison of a modified longitudinal simulation-based advanced cardiovascular life support to a traditional advanced cardiovascular life support curriculum in third-year medical students.

    PubMed

    Ko, Paul Y; Scott, Jay M; Mihai, Aurel; Grant, William D

    2011-10-01

    Simulation is an effective tool for teaching medical students in cardiac arrest management. The purpose of this article is to compare the efficacy of a traditional Advanced Cardiovascular Life Support (ACLS) course versus a modified longitudinal ACLS course using high-fidelity simulation in medical students. One group enrolled in a 2-day traditional ACLS course while another group participated in independent learning over 2 weeks and 2 simulation sessions using Laerdal Sim-Man. The modified curriculum also included environmental fidelity with simulation, access to materials electronically, smaller class sizes, and integration of real experiences in the Emergency Department into their learning. Student performance was measured with a scripted, videotaped mega code, followed by a survey. We enrolled 21 students in a traditional ACLS program and 29 students in the simulation-based program (15 and 26 videos available for analysis). There was no difference in Time to Initiate CPR or Time to Shock between the groups, but the modified curriculum group demonstrated higher performance scores. They also felt better prepared to run the code during a simulation and in a hospital setting compared to students in the traditional ACLS curriculum. Students in a modified longitudinal simulation-based ACLS curriculum demonstrated better proficiency in learning ACLS compared to a traditional curriculum.

  7. Three-lane changing behaviour simulation using a modified optimal velocity model

    NASA Astrophysics Data System (ADS)

    Lv, Wei; Song, Wei-guo; Fang, Zhi-ming

    2011-06-01

    In real urban traffic, roadways are usually multilane and are divided into fast, medium and slow lanes according to different velocity restrictions. Microscopic modelling of single lane has been studied widely using discrete cellular automata and continuous optimal velocity models. In this paper, we extend the continuous single-lane models (OV model and FVD model) to simulate the lane-changing behaviour on an urban roadway that consists of three lanes. Considering headway difference, velocity difference, safety distance, and the probability of lane-changing intention, a comprehensive lane-changing rule set is constructed. We analyse the fundamental diagram and reveal the “faster-is-slower” effect in urban traffic induced by lane-changing behaviour. We also investigate the effect of lane-changing behaviour on the distribution of vehicles, velocity, flow and headway. Asymmetrical phenomenon with symmetrical rules on urban roadway and density inversion on the slow lane were also found. The simulation results indicate that lane-changing behaviour is not advisable on crowded urban roadway. It is hoped that information from this study may be useful for traffic control and individual moving strategy on urban roadway.

  8. Atomic-level simulations of biomolecular systems with a modified Amber force field

    NASA Astrophysics Data System (ADS)

    Simmerling, Carlos L.

    2008-03-01

    Experimental methods have been highly successful in determining 3-dimensional biomolecular structures. However, most approaches provide only time- or ensemble-averaged data, making it much more difficult to study the dynamic and energetic aspects of biological systems. Atomic-resolution simulations are highly complementary to experiments, and can provide data with unparalleled resolution in time and space. Due to the long timescales of biologically relevant events, as well as the complexity of the energy function, accurate and precise simulations remain highly computationally challenging. This seminar will highlight recent progress in both areas, illustrating how energy functions that have been trained on simple peptide models can be successfully used for the study of much more complex systems. We demonstrate that our newly trained energy parameters significantly reduce the secondary structure bias reported for previous Amber parameter sets. Applications of the parameters include studies of folding behavior of peptides and small proteins, and the dynamic behavior of larger biomolecular systems such as conformational changes during drug binding in HIV-1 protease.

  9. Assessing and simulation of membrane technology for modifying starchy wastewater treatment

    NASA Astrophysics Data System (ADS)

    Hedayati Moghaddam, Amin; Hazrati, Hossein; Sargolzaei, Javad; Shayegan, Jalal

    2016-11-01

    In this study, a hydrophilic polyethersulfone membrane was used to modify the expensive and low efficient conventional treatment method of wheat starch production that would result in a cleaner starch production process. To achieve a cleaner production, the efficiency of starch production was enhanced and the organic loading rate of wastewater that was discharged into treatment system was decreased, simultaneously. To investigate the membrane performance, the dependency of rejection factor and permeate flux on operative parameters such as temperature, flow rate, concentration, and pH of feed were studied. Response surface methodology (RSM) has been applied to arrange the experimental layout which reduced the number of experiments and also the interactions between the parameters were considered. The maximum achieved rejection factor and permeate flux were 97.5% and 2.42 L min-1 m-2, respectively. Furthermore, a fuzzy inference system was selected to model the non-linear relations between input and output variable which cannot easily explained by physical models. The best agreement between the experimental and predicted data for permeate flux was denoted by correlation coefficient index (R 2) of 0.9752 and mean square error (MSE) of 0.0072 where defuzzification operator was center of rotation (centroid). Similarly, the maximum R 2 for rejection factor was 0.9711 where the defuzzification operator was mean of maxima (mom).

  10. 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.

  11. Seismic wavefield simulation by a modified finite element method with a perfectly matched layer absorbing boundary

    NASA Astrophysics Data System (ADS)

    Meng, Weijuan; Fu, Li-Yun

    2017-08-01

    The finite element method is a very important tool for modeling seismic wave propagation in complex media, but it usually consumes a large amount of memory which significantly decreases computational efficiency when solving large-scale seismic problems. Here, a modified finite element method (MFEM) is proposed to improve efficiency. Triangular elements are employed to mesh the topography and the discontinuous interface more flexibly. In the two-dimensional case, the Jacobian matrix is obtained by using three controlling points instead of all nodes in each element with MFEM, which separates the Jacobian matrix from the stiffness matrix. The kernel matrices of the stiffness matrix rather than the global matrix are stored, and memory requirements are thus reduced significantly. Meanwhile, the element-by-element scheme is adopted to spare large sparse matrices and make the program easily parallelized. A second-order perfectly matched layer (PML) is also implemented to eliminate artificial reflections. Finally, the accuracy and efficiency of our algorithm are validated by numerical tests.

  12. A Physical Heart Failure Simulation System Utilizing the Total Artificial Heart and Modified Donovan Mock Circulation.

    PubMed

    Crosby, Jessica R; DeCook, Katrina J; Tran, Phat L; Betterton, Edward; Smith, Richard G; Larson, Douglas F; Khalpey, Zain I; Burkhoff, Daniel; Slepian, Marvin J

    2017-07-01

    With the growth and diversity of mechanical circulatory support (MCS) systems entering clinical use, a need exists for a robust mock circulation system capable of reliably emulating and reproducing physiologic as well as pathophysiologic states for use in MCS training and inter-device comparison. We report on the development of such a platform utilizing the SynCardia Total Artificial Heart and a modified Donovan Mock Circulation System, capable of being driven at normal and reduced output. With this platform, clinically relevant heart failure hemodynamics could be reliably reproduced as evidenced by elevated left atrial pressure (+112%), reduced aortic flow (-12.6%), blunted Starling-like behavior, and increased afterload sensitivity when compared with normal function. Similarly, pressure-volume relationships demonstrated enhanced sensitivity to afterload and decreased Starling-like behavior in the heart failure model. Lastly, the platform was configured to allow the easy addition of a left ventricular assist device (HeartMate II at 9600 RPM), which upon insertion resulted in improvement of hemodynamics. The present configuration has the potential to serve as a viable system for training and research, aimed at fostering safe and effective MCS device use. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

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

    PubMed Central

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

    2009-01-01

    A key application of Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) has been in selectively transmitting trace analyte ions that are present in a complex ion mixture to a Mass Spectrometer (MS) downstream for identification and quantification. The overall sensitivity of FAIMS-MS, however, still needs to be significantly improved through the optimization of the ion transmission in and out of FAIMS. Processes that can cause ion losses include diffusion, space charge, separation field in the FAIMS and fringe fields around the edges of the FAIMS electrodes. These were studied here by first developing an algorithm using SIMION™ as its core structure to compute ion trajectory at different ratios of electric field to buffer gas number density (E/N). The E/N was varied from a few Td to ~80 Td by using an asymmetric square waveform. The algorithm was then combined with Statistical Diffusion Simulation (SDS) model, columbic repulsion, and a parabolic gas flow profile to realistically simulate current transmission and resolution of the FAIMS. The algorithm was validated using a FAIMS model similar to the Sionex Corporation model SVAC in terms of its dimensions and geometry and selected low mass ions with Ko in the range of 2.17 (m=55) to 1.39 cm2.V−1.s−1 (m=368). Good agreement was achieved between simulated and experimental CV (peak maxima) values, peak width (FWHM), and transmitted ion current Ioutput. The model was then used to study fringe fields in a simple arrangement where a 0.5 mm (w) gap was created between the FAIMS exit and a capillary inlet (i.d = 0.5 mm). At an optimum CV (11.8 V), only ~18% (1.3 pA) of the total ion current that correlate to CV = 11.8V, entered the capillary; bulk of the ion loss was caused by the fringe fields. Current transmission into the capillary was improved, however, by applying a 500V DC bias across w (0.5 mm). PMID:19785446

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

    NASA Astrophysics Data System (ADS)

    Angraini, Lily Maysari; Suparmi, Variani, Viska Inda

    2010-12-01

    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.

  15. 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.

  16. 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).

  17. 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.

  18. Recognition of RNA by amide modified backbone nucleic acids: molecular dynamics simulations of DNA-RNA hybrids in aqueous solution.

    PubMed

    Nina, Mafalda; Fonné-Pfister, Raymonde; Beaudegnies, Renaud; Chekatt, Habiba; Jung, Pierre M J; Murphy-Kessabi, Fiona; De Mesmaeker, Alain; Wendeborn, Sebastian

    2005-04-27

    Thermodynamic and structural properties of a chemically modified DNA-RNA hybrid in which a phosphodiester linkage is replaced by a neutral amide-3 linkage (3'-CH(2)-CONH-5') were investigated using UV melting experiments, molecular dynamics simulations in explicit water, and continuum solvent models. van't Hoff analysis of the experimental UV melting curves suggests that the significant increase of the thermodynamic stability of a 15-mer DNA-RNA with seven alternated amide-3 modifications (+11 degrees C) is mainly due to an increased binding enthalpy. To further evaluate the origin in the observed affinities differences, the electrostatic contribution to the binding free energy was calculated by solving the Poisson-Boltzmann equation numerically. The nonelectrostatic contribution was estimated as the product of a hydrophobic surface tension coefficient and the surface area that is buried upon double strand formation. Structures were taken from 10 ns molecular dynamics simulations computed in a consistent fashion using explicit solvent, counterions, and the particle-mesh Ewald procedure. The present preliminary thermodynamic study suggests that the favorable binding free energy of the amide-3 DNA single strand to the complementary RNA is equally driven by electrostatic and nonpolar contributions to the binding compared to their natural analogues. In addition, molecular dynamics simulations in explicit water were performed on an amide-3 DNA single strand and the corresponding natural DNA. Results from the conformations cluster analysis of the simulated amide-3 DNA single strand ensembles suggest that the 25% of the population sampled within 10 ns has a pre-organized conformation where the sugar C3' endo pucker is favored at the 3'-flanking nucleotides. These structural and thermodynamic features contribute to the understanding of the observed increased affinities of the amide-3 DNA-RNA hybrids at the microscopic level.

  19. Effect of food-simulating liquids on surface characteristics of composite and polyacid-modified composite restoratives.

    PubMed

    Yap, A U; Low, J S; Ong, L F

    2000-01-01

    The chemical environment is one aspect of the oral environment that could have an appreciable influence on the in vivo degradation of composite resins. The effects of food-simulating liquids on the surface roughness and hardness of composite (Silux Plus, Z100, Spectrum TPH, and P50) and polyacid-modified composite resins (F2000 and Dyract AP) were thus investigated and compared. Sixty disks of each material were made. Half were used for microhardness testing and the remaining half for studying surface roughness using profilometry. Each group of 30 disks was subdivided into six groups of five and conditioned for one week as follows--Group 1 (control): air at 37 degrees C; Group 2: distilled water at 37 degrees C; Group 3: 0.02 N citric acid at 37 degrees C; Group 4: 0.02 N lactic acid at 37 degrees C Group 5: heptane at 37 degrees C; Group 6: 50% ethanol-water solution at 37 degrees C. Data were analyzed using one-way ANOVA and Scheffé's test at a significance level of 0.05. Results showed that the surface roughness of all restoratives evaluated was not significantly affected by food-simulating liquids. No significant change in surface hardness was noted with conditioning of Spectrum TPH, Dyract AP, and F2000 in the various food-simulating liquids. The BIS-GMA-based composites Silux Plus, Z100, and P50 appeared to be more susceptible to the softening effects of some food-simulating liquids.

  20. Coarse-grained molecular dynamics simulation of DNA translocation in chemically modified nanopores.

    PubMed

    Ramachandran, Abhijit; Guo, Qingjiang; Iqbal, Samir M; Liu, Yaling

    2011-05-19

    Solid-state nanopores provide a direct means to detect and analyze DNA and proteins. In a typical setup, the DNA molecules travel through a nanopore under electrophoretic voltage bias. The nanopore is sandwiched between two chambers that are filled with ionic solution. A major challenge in using solid-state nanopores for DNA sequencing and gene detection is to improve their selectivity and detection sensitivity. To achieve these goals, one solution is to functionalize the nanopores by chemically modifying the pore walls with silanes or nucleic acids. However, little is known about molecular interactions in functionalized nanopores. This paper presents DNA translocation dynamics and the mechanism of DNA sequencing in a functionalized nanopore through a coarse-grained molecular dynamics model. The DNA nucleotide is coarse-grained into two interaction sites: one site corresponds to the base group and the other encompasses the phosphate and sugar groups. The water molecules are included in the model implicitly through Langevin dynamics. The coarse-grained model immensely improves the computational efficiency while still capturing the essential translocation dynamics. The model characterizes important physical properties of functionalized nanopores such as the effective pore diameter and effect of biasing voltage on the DNA translocation dynamics. The model reveals a nonlinear relationship between translocation speed of DNA and applied voltage. Moreover, DNA translocation in nanopores functionalized with hairpin-loop (HPL) DNA and single-stranded DNA (ss-DNA) shows significant differences: a target DNA is found to translocate through a ss-DNA coated nanopore 9 times faster than through an HPL coated one at a bias of 100 mV, putatively from lower stiffness of ss-DNA than that for HPL. The DNA translocation speed is also largely influenced by interaction potential between the DNA and surface-tethered molecules. The results reveal that such selective translocation

  1. Modified morphology of graphene sheets by Argon-atom bombardment: molecular dynamics simulations.

    PubMed

    Wei, Xiao-Lin; Zhang, Kai-Wang; Wang, Ru-Zhi; Liu, Wen-Liang; Zhong, Jian-Xin

    2011-12-01

    By a molecular dynamics method, we simulated the process of Argon-atom bombardment on a graphene sheet with 2720 carbon atoms. The results show that, the damage of the bombardment on the graphene sheet depends not only on the incident energy but also on the particle flux density of Argon atoms. To compare and analyze the effect of the incident energy and the particle flux density in the Argon-atom bombardment, we defined the impact factor on graphene sheet by calculating the broken-hole area. The results indicate that, there is an exponential accumulated-damage for the impact of both the incident energy and the particle flux density and there is a critical incident energy ranging from 20-30 eV/atom in Argon-atom bombardment. Different configurations, such as sieve-like and circle-like graphene can be formed by controlling of different particle flux density as the incident energy is more than the critical value. Our results supply a feasible method on fabrication of porous graphene-based materials for gas-storages and molecular sieves, and it also helps to understand the damage mechanism of graphene-based electronic devices under high particle radiation.

  2. MLNSC instrument design and simulation package, task order 57 (modified). Final report, September 30, 1997

    SciTech Connect

    Seeger, P.A.

    1997-10-03

    The objectives of this task as described in Statement of Work have been met and the documents required as Deliverables have been prepared and submitted to the requester. Specifically, a document titled ``The MCLIB Library: Monte Carlo Simulation of Neutron Scattering Instruments,`` revised September 23, 1997, includes documentation of new standards, code revisions and additions, and some improved efficiency due to improved optimization strategies. The procedures for user implementation of new optical devices, and information on using the package and reading and viewing the output have also been included. Second, a new document entitled ``MCLIB Element Definitions and Help`` was written and revised through the duration of the task, to supply the needed input to group CIC-15 for the purpose of integrating the MCLIB package with a web-based user interface. Finally, an application of the package was presented and a (successful) demonstration of the new user interface was given at a workshop at Argonne National Laboratory, August 24--26, 1997, as described in the modification to the Statement of Work.

  3. 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.

  4. Predictive modelling for packaging design: equilibrium modified atmosphere packages of fresh-cut vegetables subjected to a simulated distribution chain.

    PubMed

    Jacxsens, L; Devlieghere, F; Debevere, J

    2002-03-01

    The impact of temperature fluctuations in a simulated cold distribution chain, typical of commercial practice, was investigated on both the microbial and sensorial quality of equilibrium modified atmosphere (EMA) packaged minimally processed vegetables. The internal O2 concentration of the designed packages could be predicted for the different steps of the simulated distribution chain by applying an integrated mathematical system. The internal atmosphere in the packages remained in its aerobic range during storage in the chain due to the application of high permeable packaging films for O2 and CO2. Spoilage microorganisms were proliferating fast on minimally processed bell peppers and lettuce. Yeasts showed to be the shelf-life limiting group. Visual properties limited the sensorial shelf-life. Listeria monocytogenes was able to multiply on cucumber slices, survived on minimally processed lettuce and decreased in number on bell peppers due to the combination of low pH and refrigeration. Aeromonas caviae was multiplying on both cucumber slices and mixed lettuce, but was as well inhibited by the low pH of bell peppers. Storage temperature control was found to be of paramount importance for the microbial (spoilage and safety) and sensorial quality evaluation of EMA-packaged minimally processed vegetables.

  5. 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

  6. 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.

  7. Novel bioactive materials developed by simulated body fluid evaluation: Surface-modified Ti metal and its alloys.

    PubMed

    Kokubo, Tadashi; Yamaguchi, Seiji

    2016-10-15

    Until the discovery of the bone-bonding activity of Bioglass by Hench et al. in the early 1970s, it had not been demonstrated that a synthetic material could bond to living bone without eliciting a foreign body reaction. Since then, various kinds of materials based on calcium phosphate, such as sintered hydroxyapatite and β-tricalcium phosphate have also been shown to bond to living bone. Until the discovery of the bone-bonding activity of Ti metal formed with a sodium titanate surface layer by the present authors in 1996, it had not been shown that a metallic material could bond to living bone. Since then, various kinds of surface-modified Ti metal and its alloys have been found to bond to living bone. Until the discovery of the osteoinduction of porous hydroxyapatite by Yamasaki in 1990, it was unknown whether a synthetic material could induce bone formation even in muscle tissue. Since then, various kinds of porous calcium phosphate ceramics have been shown to induce osteoinduction. Until the discovery of osteoinduction induced by a porous Ti metal formed with a titanium oxide surface layer by Fujibayashi et al. in 2004, it had been unclear whether porous metals would be able to induce osteoinduction. These novel bioactive materials have been developed by systematic research into the apatite formation that occurs on surface-modified Ti metal and its related materials in an acellular simulated body fluid (SBF) having ion concentrations almost equal to those of human blood plasma. Some of the novel bioactive materials based on Ti metal are already in clinical use or clinical trials, such as artificial hip joints and spinal fusion devices. In the present paper, we review how these novel bioactive materials based on Ti metal have been developed based on an evaluation of apatite formation in SBF. Without the SBF evaluation, these novel bioactive materials would most likely never have been developed. On the basis of systematic study of apatite formation on a material

  8. Effect of addition of Nano hydroxyapatite particles on wear of resin modified glass ionomer by tooth brushing simulation

    PubMed Central

    Poorzandpoush, Kiana; Jafarnia, Shiva H.; Golkar, Parisa; Atai, Mohammad

    2017-01-01

    Background Recently, incorporation of nanohydroxyapatite (NHA) has been suggested to improve the mechanical properties of glass ionomers (GIs). This study aimed to assess the effect of addition of NHA on wear of resin modified glass ionomer (RMGI) by tooth brushing simulation. Material and Methods In this in vitro, experimental study, NHA in 1, 2, 5, 7 and 10wt% concentrations was added to Fuji II LC RMGI powder, and 48 samples (5×5mm) in five experimental and one control group (n=8) were fabricated. After polishing, cleaning and incubation at 37°C for three weeks, the samples were weighed and subjected to tooth brushing simulation in a toothpaste slurry according to ISO14569-1. Then, they were weighed again and the weight loss was calculated. The data were analyzed using one-way ANOVA and Tukey’s test. Results The highest and the lowest weight loss was found in the 0% NHA (-1.052±0.176) and 5% NHA (-0.370±0.143) groups, respectively. Wear was significantly higher in 0% NHA group (P<0.05). No difference was detected in wear between 2 and 5wt% NHA or among 1, 7 and 10wt% NHA groups. Significant differences were noted in wear between 2 and 5wt% NHA and 1, 7 and 10wt% NHA groups (P<0.001). Conclusions Incorporation of up to 10wt% of NHA increases the wear resistance of Fuji II LC RMGI. This increase was the highest when 2 and 5wt% NHA were added. Key words:Glass ionomer, hydroxyapatites, nanoparticles, dental restoration wear. PMID:28298977

  9. In vitro degradation and mechanical integrity of calcium-containing magnesium alloys in modified-simulated body fluid.

    PubMed

    Kannan, M Bobby; Raman, R K Singh

    2008-05-01

    The successful applications of magnesium-based alloys as degradable orthopaedic implants are mainly inhibited due to their high degradation rates in physiological environment and consequent loss in the mechanical integrity. This study examines the degradation behaviour and the mechanical integrity of calcium-containing magnesium alloys using electrochemical techniques and slow strain rate test (SSRT) method, respectively, in modified-simulated body fluid (m-SBF). Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) results showed that calcium addition enhances the general and pitting corrosion resistances of magnesium alloys significantly. The corrosion current was significantly lower in AZ91Ca alloy than that in AZ91 alloy. Furthermore, AZ91Ca alloy exhibited a five-fold increase in the surface film resistance than AZ91 alloy. The SSRT results showed that the ultimate tensile strength and elongation to fracture of AZ91Ca alloy in m-SBF decreased only marginally (approximately 15% and 20%, respectively) in comparison with these properties in air. The fracture morphologies of the failed samples are discussed in the paper. The in vitro study suggests that calcium-containing magnesium alloys to be a promising candidate for their applications in degradable orthopaedic implants, and it is worthwhile to further investigate the in vivo corrosion behaviour of these alloys.

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

    PubMed Central

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

    2016-01-01

    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

  11. Simulation of collaborative studies for real-time PCR-based quantitation methods for genetically modified crops.

    PubMed

    Watanabe, Satoshi; Sawada, Hiroshi; Naito, Shigehiro; Akiyama, Hiroshi; Teshima, Reiko; Furui, Satoshi; Kitta, Kazumi; Hino, Akihiro

    2013-01-01

    To study impacts of various random effects and parameters of collaborative studies on the precision of quantitation methods of genetically modified (GM) crops, we developed a set of random effects models for cycle time values of a standard curve-based relative real-time PCR that makes use of an endogenous gene sequence as the internal standard. The models and data from a published collaborative study for six GM lines at four concentration levels were used to simulate collaborative studies under various conditions. Results suggested that by reducing the numbers of well replications from three to two, and standard levels of endogenous sequence from five to three, the number of unknown samples analyzable on a 96-well PCR plate in routine analyses could be almost doubled, and still the acceptable repeatability RSD (RSDr < or = 25%) and the reproducibility RSD (RSDR < 35%) of the collaborative study could be met. Further, RSDr and RSD(R) were found most sensitive to random effects attributable to inhomogeneity among blind replicates, but they were little influenced by those attributable to DNA extractions. The proposed models are expected to be useful for optimizing standard curve-based relative quantitation methods for GM crops by real-time PCR and their collaborative studies.

  12. Gestational and Early Postnatal Exposure to Simulated High Altitude Does Not Modify Postnatal Body Mass Growth Trajectory in the Rat

    PubMed Central

    Champin, Graciela M.; Bozzini, Clarisa; Alippi, Rosa M.

    2014-01-01

    Abstract Bozzini, Carlos E, Graciela M. Champin, Clarisa Bozzini, and Rosa M. Alippi. Gestational and Early Postnatal Exposure to Simulated High Altitude Does Not Modify Postnatal Body Mass Growth Trajectory in the Rat. High Alt Med Biol 15:418–421, 2014.—Postnatal hypoxia blunts body mass growth. It is also known that the quality of the fetal environment can influence the subsequent adult phenotype. The main purpose of the study was to determine whether gestational hypoxia and early postnatal hypoxia are able to blunt growth when the offspring is raised under normoxia. Hypobaric hypoxia was induced in simulated high altitude (SHA) chambers in which air was maintained at 380 mmHg (5450 m). Mature Sprague-Dawley rats of both sexes were divided in normoxic (NX) and hypoxic (HX) groups and, in the case of the HX group, maintained for 1 month at 5450 m. Mating was then allowed under NX or HX conditions. Offspring were NX-NX, NX-HX, HX-HX, or HX-NX: the first term indicates NX or HX during both gestation and the first 30 days of life; the second term indicates NX or HX during postnatal life between days 30 and 133. Body mass (g) was measured periodically and body mass growth rate (BMGR, g/d) was estimated between days 33 and 65 of postnatal life. Results can be summarized as follows: 1) BM was significantly higher in NX than in HX rats at weaning; 2) BMGR was not significantly different between NX-NX and HX-NX rats, and between HX-HX and NX-HX animals; and 3) BMGR was significantly higher in rats living under NX conditions than in those living under HX conditions during postnatal life. Data suggest that that hypobaric hypoxia during gestational and early postnatal development of rats does not alter the regulation of body mass growth in rats when compared to that seen under sea-level conditions. PMID:25184739

  13. Reversal of the Detrimental Effects of Simulated Microgravity on Human Osteoblasts by Modified Low Intensity Pulsed Ultrasound

    PubMed Central

    Zia Uddin, Sardar M.; Hadjiargyrou, Michael; Cheng, Jiqi; Zhang, Shu; Hu, Minyi; Qin, Yi-Xian

    2013-01-01

    Microgravity (MG) is known to induce bone loss in astronauts during long duration spare mission due to lack of sufficient mechanical stimulation under microgravity. It has been demonstrated that mechanical signals are essential for maintain cell viability and motility, and possibly serve as a countermeasure to the catabolic effects of MG. The objective of this study was to examine the effects of high frequency acoustic wave signals on osteoblasts in a simulated microgravity (SMG) environment (created using 1D clinostat bioreactor) using a modified low intensity pulsed ultrasound (mLIPUS). Specifically, we evaluated the hypothesis that osteoblasts [human fetal osteoblastic (hFob) cell line] exposure to mLIPUS for 20 min per day at 30 mW/cm2 will significantly reduce the detrimental effects of SMG. Effects of SMG with mLIPUS were analyzed using the MTS assay for proliferation, Phalloidin for F-actin staining, Sirius red stain for collagen and Alizarin red for mineralization. Our data showed that osteoblast exposure to SMG results in significant decreases in proliferation (~ −38% and ~ −44% at day 4 and 6, respectively, p<0.01), collagen content (~ −22%, p<0.05) and mineralization (~ −37%, p < 0.05) and actin stress fibers. In contrast, mLIPUS stimulation in SMG condition significantly increases the rate of proliferation (~24% by day 6, p<0.05), collagen content (~52%, p < 0.05) and matrix mineralization (~25%, p<0.001) along with restoring formation of actin stress fibers in the SMG-exposed osteoblasts. These data suggest that the acoustic wave can potentially be used as a countermeasure for disuse osteopenia. PMID:23453382

  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. Modified natural cycle versus controlled ovarian hyperstimulation IVF: a cost-effectiveness evaluation of three simulated treatment scenarios.

    PubMed

    Groen, Henk; Tonch, Nino; Simons, Arnold H M; van der Veen, Fulco; Hoek, Annemieke; Land, Jolande A

    2013-12-01

    Can modified natural cycle IVF or ICSI (MNC) be a cost-effective alternative for controlled ovarian hyperstimulation IVF or ICSI (COH)? The comparison of simulated scenarios indicates that a strategy of three to six cycles of MNC with minimized medication is a cost-effective alternative for one cycle of COH with strict application of single embryo transfer (SET). MNC is cheaper per cycle than COH but also less effective in terms of live birth rate (LBR). However, strict application of SET in COH cycles reduces effectiveness and up to three MNC cycles can be performed at the same costs as one COH cycle. The cost-effectiveness of MNC versus COH was evaluated in three simulated treatment scenarios: three cycles of MNC versus one cycle of COH with SET or double embryo transfer (DET) and subsequent transfer of cryopreserved embryos (Scenario 1); six cycles of MNC versus one cycle of COH with strictly SET and subsequent transfer of cryopreserved embryos (Scenario 2); six cycles of MNC with minimized medication (hCG ovulation trigger only) versus one cycle of COH with SET or DET and subsequent transfer of cryopreserved embryos (Scenario 3). We used baseline data obtained from two retrospective cohorts of consecutive patients (2005-2008) undergoing MNC in the University Medical Center Groningen (n = 499, maximum six cycles per patient) or their first COH cycle with subsequent transfer of cryopreserved embryos in the Academic Medical Center Amsterdam (n = 392). Data from 1994 MNC cycles (958 MNC-IVF and 1036 MNC-ICSI) and 392 fresh COH cycles (one per patient, 196 COH-IVF and 196 COH-ICSI) with subsequent transfer of cryopreserved embryos (n = 72 and n = 94 in MNC and COH cycles, respectively) in ovulatory, subfertile women <36 years of age served as baseline for the three simulated scenarios. To compare the scenarios, the incremental cost-effectiveness ratio (ICER) was calculated, defined as the ratio of the difference in IVF costs up to 6 weeks postpartum to the

  18. Assessment of the modified rotation/curvature correction SST turbulence model for simulating swirling reacting unsteady flows in a solid-fuel ramjet engine

    NASA Astrophysics Data System (ADS)

    Musa, Omer; Xiong, Chen; Changsheng, Zhou; Lunkun, Gong

    2016-12-01

    The present paper presents an assessment of the performance of the modified curvature-correction shear stress transport turbulence model (SST-CCM) proposed by Omer Musa et al. (2016) [12], for simulating swirling reacting unsteady flow in a solid-fuel ramjet engine. Results are compared to both the original SST and rotation-curvature SST (SST-RC) turbulence models. First, a numerical model has been developed to solve axisymmetric unsteady Reynolds-averaged Navier-Stokes equations of the turbulent swirling compressible flow field with chemical reactions. Second, in order to evaluate the accuracy and robustness of the code, experiment on the solid-fuel ramjet without swirl has been performed and simulation on Shock-induced combustion benchmark case is carried out as well. Finally, unsteady simulations are carried out for reacting turbulent flows in a solid-fuel ramjet using Polyethylene (PE) solid fuel with three different turbulence models. It is found that in terms of accuracy for simulating reacting swirling flows the modified model slightly improves the original SST model and is quite similar to the SST-RC.

  19. 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.

  20. Development and validation of a modified Hybrid-III six-year-old dummy model for simulating submarining in motor-vehicle crashes.

    PubMed

    Hu, Jingwen; Klinich, Kathleen D; Reed, Matthew P; Kokkolaras, Michael; Rupp, Jonathan D

    2012-06-01

    In motor-vehicle crashes, young school-aged children restrained by vehicle seat belt systems often suffer from abdominal injuries due to submarining. However, the current anthropomorphic test device, so-called "crash dummy", is not adequate for proper simulation of submarining. In this study, a modified Hybrid-III six-year-old dummy model capable of simulating and predicting submarining was developed using MADYMO (TNO Automotive Safety Solutions). The model incorporated improved pelvis and abdomen geometry and properties previously tested in a modified physical dummy. The model was calibrated and validated against four sled tests under two test conditions with and without submarining using a multi-objective optimization method. A sensitivity analysis using this validated child dummy model showed that dummy knee excursion, torso rotation angle, and the difference between head and knee excursions were good predictors for submarining status. It was also shown that restraint system design variables, such as lap belt angle, D-ring height, and seat coefficient of friction (COF), may have opposite effects on head and abdomen injury risks; therefore child dummies and dummy models capable of simulating submarining are crucial for future restraint system design optimization for young school-aged children. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

  1. Synthesis and characterization of Fullerene modified ZnAlTi-LDO in photo-degradation of Bisphenol A under simulated visible light irradiation.

    PubMed

    Ju, Liting; Wu, Pingxiao; Lai, Xiaolin; Yang, Shanshan; Gong, Beini; Chen, Meiqing; Zhu, Nengwu

    2017-09-01

    In this study, ZnAlTi layered double hydroxide (ZnAlTi-LDH) combined with fullerene (C60) was fabricated by the urea method, and calcined under vacuum atmosphere to obtain nanocomposites of C60-modified ZnAlTi layered double oxide (ZnAlTi-LDO). The morphology, structure and composition of the nanocomposites were analyzed by Scanning Electron Microscopy, High-resolution transmission electron microscopy, X-ray diffraction patterns, Fourier transform infrared and specific surface area. The UV-vis diffuse reflectance spectra indicated that the incorporation of C60 expanded the absorption of ZnAlTi-LDO to visible-light region. The photo-degradation experiment was conducted by using a series of C60 modified ZnAlTi-LDO with different C60 weight percentage to degrade Bisphenol A (BPA) under simulated visible light irradiation. In this experiment, the degradation rate of C60 modified ZnAlTi-LDO in photo-degradation of BPA under simulated visible light irradiation was over 80%. The intermediates formed in the degradation of BPA process by using LDO/C60-5% were 4-hydroxyphenyl-2-propanol, 4-isopropenylphenol and Phenol. Photogenerated holes, superoxide radical species, ·OH and singlet oxygen were considered to be responsible for the photodegradation process, among which superoxide radical species and ·OH played a predominant role in the photocatalytic reaction system. C60 modified ZnAlTi-LDO catalysts for photocatalytic reduction shows great potential in degradation of organic pollutants and environmental remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Simulation

    NASA Technical Reports Server (NTRS)

    Foster, F.; Randle, R.

    1984-01-01

    The application of flight simulation in regional airline training programs is discussed. Specifically, the use of simulation in cockpit resources management training (CRMT) is investigated. The availability of simulation resources is explored and the simulator disadvantages and advantages are cited. Problems with simulator specification, procurement, validation and use that have plagued the major air carriers over several decades are addressed.

  3. Tally modifying of MCNP and post processing of pile-up simulation with time convolution method in PGNAA

    NASA Astrophysics Data System (ADS)

    Asghar Mowlavi, Ali; Koohi-Fayegh, Rahim

    2005-11-01

    Time convolution method has been employed for pile-up simulation in prompt gamma neutron activation analysis with an Am-Be neutron source and a 137Cs gamma source. A TALLYX subroutine has been written to design a new tally in the MCNP code. This tally records gamma particle information for the detector cell into an output file to be processed later. The times at which the particles are emitted by the source have been randomly generated following an exponential decay time distribution. A time convolution program was written to process the data produced and simulate more realistic pile-up. This method can be applied in optimization studies.

  4. Size-controlled preparation of α-calcium sulphate hemihydrate starting from calcium sulphate dihydrate in the presence of modifiers and the dissolution rate in simulated body fluid.

    PubMed

    Chen, Jianmin; Gao, Jun; Yin, Hengbo; Liu, Fanggang; Wang, Aili; Zhu, Yongqiang; Wu, Zhanao; Jiang, Tingshun; Qin, Daming; Chen, Bujun; Ji, Yuqin; Sun, Min

    2013-08-01

    Different-sized α-calcium sulphate hemihydrate (α-CSH) rods were hydrothermally prepared by converting calcium sulphate dihydrate at 110-140°C in the presence of MgCl2, sodium citrate (CANa), and sodium dodecyl benzene sulfonate (SDBS) as the modifiers. The α-CSH rods with the average diameters and the average lengths in the ranges of 2.6-5.2 and 17.5-33.1 μm, respectively, were tunably prepared. The presence of the modifiers favoured the formation of small-sized α-CSH rods. The effect of the modifiers on decreasing the diameters of α-CSH rods was in an order of SDBS>CANa>MgCl2. The dissolution rates of the different-sized α-CSH rods prepared at 140°C in simulated body fluid were in an order of α-CSH (CANa)>α-CSH (MgCl2)>α-CSH (reference)>α-CSH (SDBS). The naked and small-sized α-CSH rods had high dissolution rates. The adsorption of SDBS on the surfaces of α-CSH rods decreased their dissolution rates. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. 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.

  6. 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.

  7. Monte Carlo simulations of the pulsed thermal neutron flux in two-zone systems with Plexiglas - Using the MCNP code with a modified hydrogen-data library

    NASA Astrophysics Data System (ADS)

    Krynicka, Ewa; Wiącek, Urszula; Drozdowicz, Krzysztof; Gabańska, Barbara; Tracz, Grzegorz

    2006-09-01

    A comparison of real and Monte Carlo simulated pulsed neutron experiments in two-zone cylindrical systems is presented. Such geometry is met when a neutron moderator surrounds a sample of the investigated material. In this study, a Plexiglas shell (hydrogenous medium) surrounds the inner zone filled with a non-hydrogenous medium: copper oxide or chrome oxide. The time decay constant of the thermal neutron flux is determined as the result of the experiment. The primary simulations have been made using the MCNP code with the attached standard thermal neutron scattering library for hydrogen in polyethylene (poly.01t). A modification of this library is proposed to obtain the data dedicated more precisely for scattering of neutrons on hydrogen in Plexiglas in the thermal energy region. Results of the simulations for two-zone cylindrical systems, using the MCNP code with the modified hydrogen-data library, show a considerably better agreement with the experimental results. The average relative deviations have decreased from about 2% (always positive) to less than 0.5% fluctuating around zero. Adequacy of the applied modification is also confirmed in simulations of the pulsed neutron experiments on homogeneous cylinders of Plexiglas.

  8. Measuring the impact of a 3D simulation experience on nursing students' cultural empathy using a modified version of the Kiersma-Chen Empathy Scale.

    PubMed

    Everson, Naleya; Levett-Jones, Tracy; Lapkin, Samuel; Pitt, Victoria; van der Riet, Pamela; Rossiter, Rachel; Jones, Donovan; Gilligan, Conor; Courtney-Pratt, Helen

    2015-10-01

    To determine the effect of immersive 3D cultural simulation on nursing students' empathy towards culturally and linguistically diverse patients. Accelerated globalisation has seen a significant increase in cultural diversity in most regions of the world over the past forty years. Clinical encounters that do not acknowledge cultural factors contribute to adverse patient outcomes and health care inequities for culturally and linguistically diverse people. Cultural empathy is an antecedent to cultural competence. Thus, appropriate educational strategies are needed to enhance nursing students' cultural empathy and the capacity to deliver culturally competent care. A one-group pretest, post-test design was used for this study. The simulation exposed students to an unfolding scene in a hospital ward of a developing county. A convenience sample of second-year undergraduate nursing students (n = 460) from a semi-metropolitan university in Australia were recruited for the study. Characteristics of the sample were summarised using descriptive statistics. T-tests were performed to analyse the differences between pre- and post simulation empathy scores using an eight item modified version of the Kiersma-Chen Empathy Scale. Students' empathy towards culturally and linguistically diverse patients significantly improved after exposure to the 3D simulation experience. The mean scores for the Perspective Taking and Valuing Affective Empathy subscales also increased significantly postsimulation. The immersive 3D simulation had a positive impact on nursing students' empathy levels in regards to culturally and linguistically diverse groups. Research with other cohorts and in other contexts is required to further explore the impact of this educational approach. Immersive cultural simulation experiences offer opportunities to enhance the cultural empathy of nursing students. This may in turn have a positive impact on their cultural competence and consequently the quality of care they

  9. A modified Holly-Preissmann scheme for simulating sharp concentration fronts in streams with steep velocity gradients using RIV1Q

    NASA Astrophysics Data System (ADS)

    Liu, Zhao-wei; Zhu, De-jun; Chen, Yong-can; Wang, Zhi-gang

    2014-12-01

    RIV1Q is the stand-alone water quality program of CE-QUAL-RIV1, a hydraulic and water quality model developed by U.S. Army Corps of Engineers Waterways Experiment Station. It utilizes an operator-splitting algorithm and the advection term in governing equation is treated using the explicit two-point, fourth-order accurate, Holly-Preissmann scheme, in order to preserve numerical accuracy for advection of sharp gradients in concentration. In the scheme, the spatial derivative of the transport equation, where the derivative of velocity is included, is introduced to update the first derivative of dependent variable. In the stream with larger cross-sectional variation, steep velocity gradient can be easily found and should be estimated correctly. In the original version of RIV1Q, however, the derivative of velocity is approximated by a finite difference which is first-order accurate. Its leading truncation error leads to the numerical error of concentration which is related with the velocity and concentration gradients and increases with the decreasing Courant number. The simulation may also be unstable when a sharp velocity drop occurs. In the present paper, the derivative of velocity is estimated with a modified second-order accurate scheme and the corresponding numerical error of concentration decreases. Additionally, the stability of the simulation is improved. The modified scheme is verified with a hypothetical channel case and the results demonstrate that satisfactory accuracy and stability can be achieved even when the Courant number is very low. Finally, the applicability of the modified scheme is discussed.

  10. Direct Analysis of Aerosolized Chemical Warfare Simulants Captured on a Modified Glass-Based Substrate by "Paper-Spray" Ionization.

    PubMed

    Dhummakupt, Elizabeth S; Mach, Phillip M; Carmany, Daniel; Demond, Paul S; Moran, Theodore S; Connell, Theresa; Wylie, Harold S; Manicke, Nicholas E; Nilles, J Michael; Glaros, Trevor

    2017-09-25

    Paper spray ionization mass spectrometry offers a rapid alternative platform requiring no sample preparation. Aerosolized chemical warfare agent (CWA) simulants trimethyl phosphate, dimethyl methylphosphonate, and diisopropyl methylphosphonate were captured by passing air through a glass fiber filter disk within a disposable paper spray cartridge. CWA simulants were aerosolized at varying concentrations using an in-house built aerosol chamber. A custom 3D-printed holder was designed and built to facilitate the aerosol capture onto the paper spray cartridges. The air flow through each of the collection devices was maintained equally to ensure the same volume of air sampled across methods. Each approach yielded linear calibration curves with R(2) values between 0.98-0.99 for each compound and similar limits of detection in terms of disbursed aerosol concentration. While the glass fiber filter disk has a higher capture efficiency (≈40%), the paper spray method produces analogous results even with a lower capture efficiency (≈1%). Improvements were made to include glass fiber filters as the substrate within the paper spray cartridge consumable. Glass fiber filters were then treated with ammonium sulfate to decrease chemical interaction with the simulants. This allowed for improved direct aerosol capture efficiency (>40%). Ultimately, the limits of detection were reduced to levels comparable to current worker population limits of 1 × 10(-6) mg/m(3).

  11. Can nutritional information modify purchase of ultra-processed products? Results from a simulated online shopping experiment.

    PubMed

    Machín, Leandro; Arrúa, Alejandra; Giménez, Ana; Curutchet, María Rosa; Martínez, Joseline; Ares, Gastón

    2017-07-18

    The aim of the present work was to evaluate the influence of two front-of-pack nutrition information schemes (traffic-light system and Chilean warning system) on consumer purchase of ultra-processed foods in a simulated online grocery store. Following a between-subjects design, participants completed a simulated weekly food purchase in an online grocery store under one of three experimental conditions: (i) a control condition with no nutrition information, (ii) a traffic-light system and (iii) the Chilean warning system. Information about energy (calories), sugar, saturated fats and salt content was included in the nutrition information schemes. Participants were recruited from a consumer database and a Facebook advertisement. People from Montevideo (Uruguay), aged 18-77 years (n 437; 75 % female), participated in the study. All participants were in charge of food purchase in the household, at least occasionally. No significant differences between experimental conditions were found in the mean share of ultra-processed foods purchased by participants, both in terms of number of products and expenditure, or in the mean energy, sugar, saturated fat and salt content of the purchased items. However, the Chilean warning system decreased intended purchase of sweets and desserts. Results from this online simulation provided little evidence to suggest that the traffic-light system or the Chilean warning system in isolation could be effective in reducing purchase of ultra-processed foods or improving the nutritional composition of the purchased products.

  12. Molecular dynamics simulations of human tRNA Lys,3 UUU: the role of modified bases in mRNA recognition.

    PubMed

    McCrate, Nina E; Varner, Mychel E; Kim, Kenneth I; Nagan, Maria C

    2006-01-01

    Accuracy in translation of the genetic code into proteins depends upon correct tRNA-mRNA recognition in the context of the ribosome. In human tRNA(Lys,3)UUU three modified bases are present in the anticodon stem-loop--2-methylthio-N6-threonylcarbamoyladenosine at position 37 (ms2t6A37), 5-methoxycarbonylmethyl-2-thiouridine at position 34 (mcm5s2U34) and pseudouridine (psi) at position 39--two of which, ms2t6A37 and mcm5s2U34, are required to achieve wild-type binding activity of wild-type human tRNA(Lys,3)UUU [C. Yarian, M. Marszalek, E. Sochacka, A. Malkiewicz, R. Guenther, A. Miskiewicz and P. F. Agris (2000) Biochemistry, 39, 13390-13395]. Molecular dynamics simulations of nine tRNA anticodon stem-loops with different combinations of nonstandard bases were performed. The wild-type simulation exhibited a canonical anticodon stair-stepped conformation. The ms2t6 modification at position 37 is required for maintenance of this structure and reduces solvent accessibility of U36. Ms2t6A37 generally hydrogen bonds across the loop and may prevent U36 from rotating into solution. A water molecule does coordinate to psi39 most of the simulation time but weakly, as most of the residence lifetimes are <40 ps.

  13. 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.

  14. 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

  15. A Modified Parallel Tree Code for N-Body Simulation of the Large-Scale Structure of the Universe

    NASA Astrophysics Data System (ADS)

    Becciani, U.; Antonuccio-Delogu, V.; Gambera, M.

    2000-09-01

    N-body codes for performing simulations of the origin and evolution of the large-scale structure of the universe have improved significantly over the past decade in terms of both the resolution achieved and the reduction of the CPU time. However, state-of-the-art N-body codes hardly allow one to deal with particle numbers larger than a few 107, even on the largest parallel systems. In order to allow simulations with larger resolution, we have first reconsidered the grouping strategy as described in J. Barnes (1990, J. Comput. Phys. 87, 161) (hereafter B90) and applied it with some modifications to our WDSH-PT (Work and Data SHaring-Parallel Tree) code (U. Becciani et al., 1996, Comput. Phys. Comm. 99, 1). In the first part of this paper we will give a short description of the code adopting the algorithm of J. E. Barnes and P. Hut (1986, Nature 324, 446) and in particular the memory and work distribution strategy applied to describe the data distribution on a CC-NUMA machine like the CRAY-T3E system. In very large simulations (typically N>=107), due to network contention and the formation of clusters of galaxies, an uneven load easily verifies. To remedy this, we have devised an automatic work redistribution mechanism which provided a good dynamic load balance without adding significant overhead. In the second part of the paper we describe the modification to the Barnes grouping strategy we have devised to improve the performance of the WDSH-PT code. We will use the property that nearby particles have similar interaction lists. This idea has been checked in B90, where an interaction list is built which applies everywhere within a cell Cgroup containing a small number of particles Ncrit. B90 reuses this interaction list for each particle p∈Cgroup in the cell in turn. We will assume each particle p to have the same interaction list. We consider that the agent force Fp on a particle p can be decomposed into two terms Fp=Ffar+Fnear. The first term Ffar is the same for

  16. pH-controlled doxorubicin anticancer loading and release from carbon nanotube noncovalently modified by chitosan: MD simulations.

    PubMed

    Rungnim, Chompoonut; Rungrotmongkol, Thanyada; Poo-Arporn, Rungtiva P

    2016-11-01

    In the present study, we describe here the pH condition activating doxorubicin (DOX) anticancer drugs loading and release over single-wall carbon nanotube (SWNT) non-covalently wrapped with chitosan (CS). The possibility of drug displacement on DOX/CS/SWNT nanocarrier was investigated using molecular dynamics simulations. The drug loading and release were monitored via displacement analysis and binding energy calculations. The simulated results clearly showed that the drugs well interacted with the CS/SWNT at physiological pH (pH 7.4), where CS was in the deprotonated form. Contrastingly, in weakly acidic environments (pH 5.0-6.5) which is a pH characteristics of certain cancer environments, the protonated CS became loosen wrapped around the SWNT and triggered drugs release as a result of charge-charge repulsion between CS and drug molecules. The obtained data fulfil the understanding at atomic level of drug loading and release controlled by pH-sensitive polymer, which might be useful for further cancer therapy researches.

  17. 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%.

  18. 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%.

  19. 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.

  20. Simulation for F.C.C. deformation texture by modified pencil glide theory[Face Centered Cubic

    SciTech Connect

    Masui, H.

    1999-11-26

    Inspired by the pencil glide theory for b.c.c. metal, modified pencil glide theory for f.c.c. metal was proposed, dividing the 12 glide systems of f.c.c. metal into three groups individually composed of eight {l{underscore}brace}111{r{underscore}brace}{l{underscore}angle}110{r{underscore}angle} glide systems around the principal axes X[100], Y[010] and Z[001]. These assumptions yielded two mathematical solutions {Omega}(3) and {Omega}(1). In {Omega}(3), from the three groups with four complete conjugated glide systems composed of, respectively, two glide systems of common {l{underscore}angle}110{r{underscore}angle} direction, only one group with the maximum plastic work may operate if the requirements are satisfied, otherwise glide systems in {Omega}(1) where one of the four conjugated glide systems is zero are activated. The model considering the 12 glide systems of f.c.c. as a whole explained many experimentally stable orientations in axisymmetric and rolling deformation. The differences between the two pencil glide theories for b.c.c. and f.c.c. are also discussed with data.

  1. Interaction of PLGA and trimethyl chitosan modified PLGA nanoparticles with mixed anionic/zwitterionic phospholipid bilayers studied using molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Novak, Brian; Astete, Carlos; Sabliov, Cristina; Moldovan, Dorel

    2012-02-01

    Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable polymer. Nanoparticles of PLGA are commonly used for drug delivery applications. The interaction of the nanoparticles with the cell membrane may influence the rate of their uptake by cells. Both PLGA and cell membranes are negatively charged, so adding positively charged polymers such as trimethyl chitosan (TMC) which adheres to the PLGA particles improves their cellular uptake. The interaction of 3 nm PLGA and TMC-modified-PLGA nanoparticles with lipid bilayers composed of mixtures of phosphatidylcholine and phosphatidylserine lipids was studied using molecular dynamics simulations. The free energy profiles as function of nanoparticles position along the normal direction to the bilayers were calculated, the distribution of phosphatidylserine lipids as a function of distance of the particle from the bilayer was calculated, and the time scale for particle motion in the directions parallel to the bilayer surface was estimated.

  2. Gravity destabilized non-wetting phase invasion in macro-heterogeneous porous media: Near pore scale macro modified invasion percolation simulation of experiments

    SciTech Connect

    GLASS JR.,ROBERT J.; CONRAD,STEPHEN H.; YARRINGTON,LANE

    2000-03-08

    The authors reconceptualize macro modified invasion percolation (MMIP) at the near pore (NP) scale and apply it to simulate the non-wetting phase invasion experiments of Glass et al [in review] conducted in macro-heterogeneous porous media. For experiments where viscous forces were non-negligible, they redefine the total pore filling pressure to include viscous losses within the invading phase as well as the viscous influence to decrease randomness imposed by capillary forces at the front. NP-MMIP exhibits the complex invasion order seen experimentally with characteristic alternations between periods of gravity stabilized and destabilized invasion growth controlled by capillary barriers. The breaching of these barriers and subsequent pore scale fingering of the non-wetting phase is represented extremely well as is the saturation field evolution, and total volume invaded.

  3. Numerical simulation of optical Stark effect saturable absorbers in mode-locked femtosecond VECSELs using a modified two-level atom model.

    PubMed

    Quarterman, A H; Carswell, S; Daniell, G J; Mihoubi, Z; Wilcox, K G; Chung, A L; Apostolopoulos, V; Tropper, A C

    2011-12-19

    The interaction of an optical pulse with a quantum well saturable absorber is simulated using a semi-classical two-level-atom model which has been modified to approximate spectral hole burning in the carrier distribution. Saturable absorption behaviour is examined in the limit where pulse duration approaches the carrier-carrier scattering time. For long pulses bleaching dominates the absorber response but as the pulse duration approaches the carrier-carrier scattering timescale an additional pulse shaping mechanism becomes active, allowing the absorber to continue to shorten pulses beyond the limit set by bleaching. Examination of the spectral and temporal absorption profiles suggests that intense pulses experience additional pulse shortening from the optical Stark effect.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. The reliability of a modified Kalamazoo Consensus Statement Checklist for assessing the communication skills of multidisciplinary clinicians in the simulated environment.

    PubMed

    Peterson, Eleanor B; Calhoun, Aaron W; Rider, Elizabeth A

    2014-09-01

    With increased recognition of the importance of sound communication skills and communication skills education, reliable assessment tools are essential. This study reports on the psychometric properties of an assessment tool based on the Kalamazoo Consensus Statement Essential Elements Communication Checklist. The Gap-Kalamazoo Communication Skills Assessment Form (GKCSAF), a modified version of an existing communication skills assessment tool, the Kalamazoo Essential Elements Communication Checklist-Adapted, was used to assess learners in a multidisciplinary, simulation-based communication skills educational program using multiple raters. 118 simulated conversations were available for analysis. Internal consistency and inter-rater reliability were determined by calculating a Cronbach's alpha score and intra-class correlation coefficients (ICC), respectively. The GKCSAF demonstrated high internal consistency with a Cronbach's alpha score of 0.844 (faculty raters) and 0.880 (peer observer raters), and high inter-rater reliability with an ICC of 0.830 (faculty raters) and 0.89 (peer observer raters). The Gap-Kalamazoo Communication Skills Assessment Form is a reliable method of assessing the communication skills of multidisciplinary learners using multi-rater methods within the learning environment. The Gap-Kalamazoo Communication Skills Assessment Form can be used by educational programs that wish to implement a reliable assessment and feedback system for a variety of learners. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  10. Comparison of modeling a conical nanotube resting on the Winkler elastic foundation based on the modified couple stress theory and molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Mohammadi, Kianoosh; Mahinzare, Mohammad; Rajabpour, Ali; Ghadiri, Majid

    2017-03-01

    In this article, the free vibration analysis of a thin conical nanotube resting on an elastic foundation is investigated for the first time by means of the modified couple stress theory (MCST) and molecular dynamics (MD) simulation. The proposed model in the MCST framework, its equations of motion and boundary conditions are derived by Hamilton's principle based on the thin shell model of Love. The differential quadrature method (DQM) is applied to discretize the equations of motion. Molecular dynamics (MD) simulation is performed via the AIREBO potential function, which is recommended in vibrational studies. The accuracy of the presented model is verified for previous studies with both methods. The novelty of the current study is reporting a specified length scale parameter of MCST which has a good conformity with MD results. This value is exclusively related to the proposed model of the present study. The effect of the elastic foundation stiffness is investigated with molecular dynamics for the first time as well. The results can have many applications, such as in modeling of scanning probe microscopy and biomedical microsystems.

  11. 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

  12. Follicle-stimulating hormone encapsulation in the cholesterol-modified chitosan nanoparticles via molecular dynamics simulations and binding free energy calculations.

    PubMed

    Yahyaei, Mohammad; Mehrnejad, Faramarz; Naderi-Manesh, Hossein; Rezayan, Ali Hossein

    2017-09-30

    Follicle-stimulating hormone (FSH) is widely applied in the modern ovarian stimulation techniques. However, it must be administered daily because of its short half-life. Recently, the cholesterol (CS) modified chitosan (CTS) nanogels have attracted significant interest as promising controlled release protein delivery because of their ability to minimize the aggregation and irreversible denaturation of proteins. Herein, we report a molecular dynamics (MD) simulation investigation on the molecular mechanisms of FSH encapsulation in the CS-CTS nanogels. The MD simulations have been performed using the GROMACS software for up to 200ns simulation time. Furthermore, the binding free energy has been calculated by the molecular mechanics [MM] with Poisson-Boltzmann [PB] and surface area solvation (MM/PBSA) method by using the g_mmpbsa tool. Our findings suggest that the main driving force of the formation of the CS-CTS nanogels is the hydrophobic interactions between the CS-CS moieties in water. The results have also indicated that the CS-CTS nanogel formation can occur through the hydrogen bonding in addition to the hydrophobic interactions. The obtained data demonstrate that the FSH encapsulation into the CS-CTS nanogels is a gradual process driven by the hydrophobic interactions between the hydrophobic patch of FSH and the hydrophobic nanodomains of the nanogel. Our results also reveal that except in the hydrophobic patch region, the flexibility of FSH was reduced in the presence of the nanogel. This study provides the elucidation of the nanogel-FSH interactions at the molecular level and presents new perspective for the ideal design and applications of the CS-CTS nanogel in protein delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Low-dose gamma-rays and simulated solar particle event protons modify splenocyte gene and cytokine expression patterns.

    PubMed

    Rizvi, Asma; Pecaut, Michael J; Gridley, Daila S

    2011-01-01

    The goal was to investigate the T helper (Th) response in splenocytes of mice exposed to low-dose/low-dose-rate (LDR) γ-rays, simulated solar particle event protons (sSPE), or combination of both. C57BL/6 mice were exposed to LDR γ-radiation ((57)Co) to a total dose of 0.05 Gray (Gy) at 0.024 cGy/h, either with or without subsequent exposure to 2 Gy sSPE protons. Expression of genes related to Th cells was evaluated immediately after exposure (day 0). On day 21, intra- and extracellular cytokine production was assessed after activation with anti-CD3 monoclonal antibodies (mAb) or phorbol 12-myristate 13-acetate/ionophore (PMA/I). Five genes were significantly modulated on day 0 in one or more of the irradiated groups compared to controls (p < 0.05): Ccl11, Ccr5, Cd80, Inha, and Il9. On day 21, numbers of cells positive for interferon-γ were high in the LDR + sSPE group versus 0 Gy and LDR γ-rays (p < 0.05), but there was no difference in IL-2 and TNF-α. Levels of secreted cytokines after anti-CD3 mAb activation were high for 5 (MIP-1α, GM-CSF, IFN-γ, TNF-α, IL-13) and low for 2 (IL-7, IL-9) in all irradiated groups. Priming with LDR photons had a significant effect on IFN-γ and IL-17 compared to sSPE protons alone; IL-2 was low only in the LDR + sSPE group. The cytokine patterns after anti-PMA/I activation were different compared to anti-CD3 mAb and with fewer differences among groups. The data show that total-body exposure to space-relevant radiation has profound effects on Th cell status and that priming with LDR γ-rays can in some cases modulate the response to sSPE.

  14. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. 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.

  16. Anisotropy in geometrically rough structure of ice prismatic plane interface during growth: Development of a modified six-site model of H2O and a molecular dynamics simulation.

    PubMed

    Nada, Hiroki

    2016-12-28

    This paper presents a modified version of the six-site model of H2O [H. Nada and J. P. J. M. van der Eerden, J. Chem. Phys. 118, 7401 (2003)]. Although the original six-site model was optimized by assuming the cut-off of the Coulomb interaction at an intermolecular distance of 10 Å, the modified model is optimized by using the Ewald method for estimating the Coulomb interaction. Molecular dynamics (MD) simulations of an ice-water interface suggest that the melting point of ice at 1 atm in the modified model is approximately 274.5 K, in good agreement with the real melting point of 273.15 K. MD simulations of bulk ice and water suggest that the modified model reproduces not only the structures and density curves of ice and water, but also the diffusion coefficient of water molecules in water near the melting point at 1 atm. Using the modified model, a large-scale MD simulation of the growth at an ice-water interface of the prismatic plane is performed to elucidate the anisotropy in the interface structure during growth. Simulation results indicate that the geometrical roughness of the ice growth front at the interface is greater in the c-axis direction than in the direction normal to the c-axis when it is analyzed along the axes parallel to the prismatic plane. In addition, during the growth at the interface, the transient appearance of specific crystallographic planes, such as a {202¯1} pyramidal plane, occurs preferentially at the ice growth front. The effect of different ensembles with different simulation systems on the anisotropy in the interface structure is also investigated.

  17. Anisotropy in geometrically rough structure of ice prismatic plane interface during growth: Development of a modified six-site model of H2O and a molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Nada, Hiroki

    2016-12-01

    This paper presents a modified version of the six-site model of H2O [H. Nada and J. P. J. M. van der Eerden, J. Chem. Phys. 118, 7401 (2003)]. Although the original six-site model was optimized by assuming the cut-off of the Coulomb interaction at an intermolecular distance of 10 Å, the modified model is optimized by using the Ewald method for estimating the Coulomb interaction. Molecular dynamics (MD) simulations of an ice-water interface suggest that the melting point of ice at 1 atm in the modified model is approximately 274.5 K, in good agreement with the real melting point of 273.15 K. MD simulations of bulk ice and water suggest that the modified model reproduces not only the structures and density curves of ice and water, but also the diffusion coefficient of water molecules in water near the melting point at 1 atm. Using the modified model, a large-scale MD simulation of the growth at an ice-water interface of the prismatic plane is performed to elucidate the anisotropy in the interface structure during growth. Simulation results indicate that the geometrical roughness of the ice growth front at the interface is greater in the c-axis direction than in the direction normal to the c-axis when it is analyzed along the axes parallel to the prismatic plane. In addition, during the growth at the interface, the transient appearance of specific crystallographic planes, such as a {20 2 ¯ 1 } pyramidal plane, occurs preferentially at the ice growth front. The effect of different ensembles with different simulation systems on the anisotropy in the interface structure is also investigated.

  18. Top-down NOX emissions over European cities from LOTOS-EUROS simulated and OMI observed tropospheric NO2 columns using the Exponentially Modified Gaussian approach

    NASA Astrophysics Data System (ADS)

    Verstraeten, Willem W.; Folkert Boersma, K.; Douros, John; Williams, Jason E.; Eskes, Henk H.; Delcloo, Andy

    2017-04-01

    High nitrogen oxides concentrations at the surface (NOX = NO + NO2) impact humans and ecosystem badly and play a key role in tropospheric chemistry. Surface NOX emissions drive major processes in regional and global chemistry transport models (CTM). NOX contributes to the formation of acid rain, act as aerosol precursors and is an important trace gas for the formation of tropospheric ozone (O3). Via tropospheric O3, NOX indirectly affects the production of the hydroxyl radical which controls the chemical lifetime of key atmospheric pollutants and reactive greenhouse gases. High NOX emissions are mainly observed in polluted regions produced by anthropogenic combustion from industrial, traffic and household activities typically observed in large and densely populated urban areas. Accurate NOX inventories are essential, but state-of the- art emission databases may vary substantially and uncertainties are high since reported emissions factors may differ in order of magnitude and more. To date, the modelled NO2 concentrations and lifetimes have large associated uncertainties due to the highly non-linear small-scale chemistry that occurs in urban areas and uncertainties in the reaction rate data, missing nitrogen (N) species and volatile organic compounds (VOC) emissions, and incomplete knowledge of nitrogen oxides chemistry. Any overestimation in the chemical lifetime may mask missing NOX chemistry in current CTM's. By simultaneously estimating both the NO2 lifetime and concentrations, for instance by using the Exponentially Modified Gaussian (EMG), a better surface NOX emission flux estimate can be obtained. Here we evaluate if the EMG methodology can reproduce the emissions input from the tropospheric NO2 columns simulated by the LOTOS-EUROS (Long Term Ozone Simulation-European Ozone Simulation) CTM model. We apply the EMG methodology on LOTOS-EUROS simulated tropospheric NO2 columns for the period April-September 2013 for 21 selected European urban areas under windy

  19. Modified mosquito landing boxes dispensing transfluthrin provide effective protection against Anopheles arabiensis mosquitoes under simulated outdoor conditions in a semi-field system.

    PubMed

    Andrés, Marta; Lorenz, Lena M; Mbeleya, Edgar; Moore, Sarah J

    2015-06-24

    Efforts to control malaria vectors have primarily focused on scaling-up of long-lasting insecticidal nets (LLINs) and indoor residual spraying. Although highly efficient against indoor-biting and indoor-resting vectors, these interventions have lower impact on outdoor-biting mosquitoes. Innovative vector control tools are required to prevent outdoor human-mosquito contacts. In this work, the potential of spatial repellents, delivered in an active system that requires minimal user compliance, to provide personal protection against exophagic mosquitoes active in the early evening was explored. A device previously used as an odour-baited lure and kill apparatus, the mosquito landing box (MLB), was modified to dispense the volatile synthetic pyrethroid, transfluthrin, as a spatial repellent. The MLB has an active odour-dispensing mechanism that uses a solar-powered fan and switches on at dusk to provide long duration dispensing of volatile compounds without the need for the user to remember to employ it. Two MLBs were located 5 m from a human volunteer to investigate the repellent effects of a transfluthrin 'bubble' created between the MLBs. Transfluthrin was emanated from polyester strips, hanging inside the MLB odour-dispensing unit. A fully randomized cross-over design was performed in a large, semi-field, screened cage to assess the effect of the repellent against laboratory-reared Anopheles arabiensis mosquitoes under ambient outdoor conditions. The knock-down capacity of the transfluthrin-treated strips was also evaluated at different time points up to 3 weeks after being impregnated to measure duration of efficacy. The protective transfluthrin bubble provided 68.9% protection against An. arabiensis bites under these simulated outdoor conditions. Volatile transfluthrin caused low mortality among mosquitoes in the semi-field system. Transfluthrin-treated strips continued to knock down mosquitoes in laboratory tests, 3 weeks after impregnation, although this effect

  20. 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.

  1. 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

  2. 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.

  3. Low-dose γ-rays modify CD4(+) T cell signalling response to simulated solar particle event protons in a mouse model.

    PubMed

    Rizvi, Asma; Pecaut, Michael J; Slater, James M; Subramaniam, Shruti; Gridley, Daila S

    2011-01-01

    Astronauts on missions are exposed to low-dose/low-dose-rate (LDR) radiation and could receive high doses during solar particle events (SPE). This study investigated T cell function in response to LDR radiation and simulated SPE (sSPE) protons, alone and in combination. C57BL/6 mice received LDR γ-radiation (⁵⁷Co) to a total dose of 0.01 Gray (Gy) at 0.179 mGy/h, either with or without subsequent exposure to 1.7 Gy sSPE protons delivered over 36 h. Mice were euthanised on days 4 and 21 post-exposure. T cells with cluster of differentiation 4 (CD4(+)) were negatively isolated from spleens and activated with anti-CD3 antibody. Cells and supernatants were evaluated for survival/signalling proteins and cytokines. The most striking effects were noted on day 21. In the survival pathway, nuclear factor-kappaB (NF-κB; total and active forms) and p38 mitogen activated protein kinase (p38MAPK; total) were significantly increased and cJun N-terminal kinase (JNK; total and active) was decreased when mice were primed with LDR γ-rays prior to sSPE exposure (P < 0.001). Evaluation of the T cell antigen receptor (TCR) signalling pathway revealed that LDR γ-ray exposure normalised the high sSPE proton-induced level of lymphocyte specific protein tyrosine kinase (Lck; total and active) on day 21 (P < 0.001 for sSPE vs. LDR + sSPE), while radiation had no effect on active zeta-chain-associated protein kinase 70 (Zap-70). There was increased production of interleukin-2 (IL-2) and IL-4 and decreased transforming growth factor-β1 in the LDR + sSPE group compared to the sSPE group. The data demonstrate, for the first time, that protracted exposure to LDR γ-rays can significantly modify the effects of sSPE protons on critical survival/signalling proteins and immunomodulatory cytokines produced by CD4(+) T cells.

  4. Modified Embedded Atom Method

    SciTech Connect

    Rudd, R. E.

    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.

  5. Simulation of the chromatographic separation process in HPLC employing suspended-state NMR spectroscopy - comparison of interaction behavior for monomeric and hydride-modified C18 stationary phases.

    PubMed

    Yeman, Helen; Nicholson, Tim; Matyska, Maria T; Pesek, Joseph J; Albert, Klaus

    2013-01-01

    The interactions of different analytes with monomeric and hydride-modified stationary phases have been investigated employing suspended-state NMR spectroscopy. The suspended-state high-resolution/magic-angle-spinning (1)H-NMR spectrum of an analyte in the presence of C(18) SP material shows a splitting into two sets of signals for the analyte molecule. One state reflects a closer interaction between analyte and C(18) -modified surface that results in an upfield shift and broader signal half-widths. This phenomenon suggests that the analyte exists in two environments. We report a systematic approach upon the investigation on the interaction in the interface of analyte, mobile phase, and modified silica through synthesis of differently modified silica with a gradual increase in surface coverage. The determination of the signal half-widths and chemical shifts revealed a relationship between the modification technique of the C(18) SPs and the chromatographic and NMR spectroscopic behavior. Increasing ligand density results in higher shielding of the NMR signals for the analyte in the "adsorbed" state. The measurement of spin-lattice relaxation times T(1) of the analyte molecule correlate NMR parameter together with separation behavior in HPLC. Furthermore, suspended-state and solid-state NMR measurements revealed different alkyl chain mobilities for the monomeric and hydride-modified SPs. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. 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

    USDA-ARS?s Scientific Manuscript database

    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...

  7. Modified SEAGULL

    NASA Technical Reports Server (NTRS)

    Salas, M. D.; Kuehn, M. S.

    1994-01-01

    Original version of program incorporated into program SRGULL (LEW-15093) for use on National Aero-Space Plane project, its duty being to model forebody, inlet, and nozzle portions of vehicle. However, real-gas chemistry effects in hypersonic flow fields limited accuracy of that version, because it assumed perfect-gas properties. As a result, SEAGULL modified according to real-gas equilibrium-chemistry methodology. This program analyzes two-dimensional, hypersonic flows of real gases. Modified version of SEAGULL maintains as much of original program as possible, and retains ability to execute original perfect-gas version.

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

    PubMed

    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. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  9. Ab-initio simulations of deformation potentials and electron mobility in chemically modified graphene and two-dimensional hexagonal boron-nitride

    NASA Astrophysics Data System (ADS)

    Bruzzone, Samantha; Fiori, Gianluca

    2011-11-01

    We present an ab-initio study of electron mobility and electron-phonon coupling in chemically modified graphene, considering fluorinated and hydrogenated graphene at different percentage coverage. Hexagonal boron carbon nitrogen is also investigated due the increased interest shown by the research community towards this material. In particular, the deformation potentials are computed by means of density functional theory, while the carrier mobility is obtained according to the Takagi model (S. Takagi, A. Toriumi, and H. Tango, IEEE Trans. Electron Devices 41, 2363 (1994)). We will show that graphene with a reduced degree of hydrogenation can compete, in terms of mobility, with silicon technology.

  10. 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.

  11. Modifiability Tactics

    DTIC Science & Technology

    2007-09-01

    about purchasing paper copies of SEI reports, please visit the publications portion of our Web site (http://www.sei.cmu.edu/ publications /pubweb.html...architects need to understand how architectural tactics and patterns relate and how to use them effectively. In this report, we explore the relation ...architecture transformations that support the achievement of modifiability [Bass 2003]. In this report, we relate coupling and cohesion to tactics

  12. Mixed Mode Stable Tearing of Thin Sheet Al 6061-T6 Specimens: Experimental Measurements and Finite Element Simulations using a Modified Mohr-Coulomb Fracture Criterion

    DTIC Science & Technology

    2010-11-01

    grounding. Oliver (1996a,b), Teng (2008) andXue (2007a) reported on successful application of contin- uum damage mechanics in simulating initiation and...the accumulated damage should reach the critical value and the load carrying capacity must vanish in the post-initiate range. It should be noted that...specimen using fracture coupled with damage plastic- ity approach. Different from Mode I, little thickness reduction is observed for Mode III loading, as

  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. Design of a modified mouse protein with ligand binding properties of its human analog by molecular dynamics simulations: the case of C3 inhibition by compstatin.

    PubMed

    Tamamis, Phanourios; Pierou, Panayiota; Mytidou, Chrystalla; Floudas, Christodoulos A; Morikis, Dimitrios; Archontis, Georgios

    2011-11-01

    The peptide compstatin and its derivatives inhibit the complement-component protein C3 in primate mammals and are potential therapeutic agents against the unregulated activation of complement in humans, but are inactive against C3 from lower mammals. Recent molecular dynamics (MD) simulations showed that the most potent compstatin analog comprised entirely of natural amino acids (W4A9) had a smaller affinity for rat C3, due to reproducible changes in the rat protein structure with respect to the human protein, which eliminated or weakened specific protein-ligand interactions seen in the human C3:W4A9 complex. Here, we study by MD simulations three W4A9 complexes with the mouse C3 protein, and two "transgenic" mouse derivatives, containing a small number (6-9) of human C3 substitutions. The mouse complex experiences the conformational changes and affinity reduction of the rat complex. In the "transgenic" complexes, the conformation remains closer to that of the human complex, the protein-ligand interactions are improved, and the affinity for compstatin becomes "human-like." The present work creates new avenues for a compstatin-sensitive animal model. A similar strategy, involving the comparison of a series of complexes by MD simulations, could be used to design "transgenic" sequences in other systems. Copyright © 2011 Wiley-Liss, Inc.

  15. Topology of modified helical gears

    NASA Technical Reports Server (NTRS)

    Litvin, F. L.; Zhang, J.; Handschuh, R. F.; Coy, J. J.

    1989-01-01

    The topology of several types of modified surfaces of helical gears is proposed. The modified surfaces allow absorption of a linear or almost linear function of transmission errors. These errors are caused by gear misalignment and an improvement of the contact of gear tooth surfaces. Principles and corresponding programs for computer aided simulation of meshing and contact of gears have been developed. The results of this investigation are illustrated with numerical examples.

  16. Topology of modified helical gears

    NASA Technical Reports Server (NTRS)

    Litvin, F. L.; Zhang, J.; Handschuh, R. F.; Coy, J. J.

    1989-01-01

    The topology of several types of modified surfaces of helical gears is proposed. The modified surfaces allow absorption of a linear or almost linear function of transmission errors. These errors are caused by gear misalignment and an improvement of the contact of gear tooth surfaces. Principles and corresponding programs for computer aided simulation of meshing and contact of gears have been developed. The results of this investigation are illustrated with numerical examples.

  17. 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.

  18. 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.

  19. 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

  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.

  1. Adhesion of bile-adapted Bifidobacterium strains to the HT29-MTX cell line is modified after sequential gastrointestinal challenge simulated in vitro using human gastric and duodenal juices.

    PubMed

    de los Reyes-Gavilán, Clara G; Suárez, Adolfo; Fernández-García, María; Margolles, Abelardo; Gueimonde, Miguel; Ruas-Madiedo, Patricia

    2011-06-01

    According to the FAO/WHO, in vitro criteria for selection of probiotics for food application consist of testing survival when confronted with gastrointestinal tract (GIT) challenge and the ability to colonize the colon. We used a model that simulated GIT transit using sequential immersion in gastric and duodenal juices of human origin to evaluate survival of bile-adapted Bifidobacterium strains. Bifidobacterium animalis tolerated gastric juice, whereas Bifidobacterium longum showed poor survival under these conditions. In contrast, B. animalis strains were more sensitive to duodenal juice than B. longum. The percentage of survival after GIT transit simulation (GITTS), determined both by plate counts and fluorescent probes, was significantly higher for bile-adapted strains than for corresponding parental ones. This suggests that use of bile-adapted strains is a suitable approach for increasing survival of bifidobacteria under the harsh conditions of the upper GIT. However, the bile resistance phenotype was not related to improvement of adhesion capacity, after GITTS, of the intestinal cell line HT29-MTX which constitutively produces mucus. This work shows that sequential GITTS with human juices modified the in vitro adhesion properties of the strains challenged with colonocyte-like cells.

  2. 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

  3. Reproductive, productivity, and mortality outcomes in late-gestation gilts and their litters following simulation of inadvertent exposure to a modified-live vaccine strain of porcine reproductive and respiratory syndrome (PRRS) virus.

    PubMed

    Schelkopf, Adam; Nerem, Joel; Cowles, Bobby; Amodie, Deb; Swalla, Richard; Dee, Scott

    2014-08-06

    The study evaluated the safety of a modified live-virus (MLV) porcine reproductive and respiratory syndrome (PRRS) vaccine in susceptible, pregnant gilts. To simulate inadvertent exposure secondary to postvaccination shedding of PRRS-MLV, seronegative gilts (n=51) were exposed by IM vaccination at 90 days of gestation. Vaccinated and nonvaccinated, seronegative control gilts (n=25) were maintained in separate facilities. The PRRS-MLV vaccine was given in a 2mL dose on day 0. On day 7 all vaccinated gilts were PRRSV-PCR-positive for PRRSV and had responded serologically as determined by an ELISA. All control gilts remained PRRSV-PCR- and ELISA-negative throughout the study. Abortions did not occur in gilts from either group. The difference between vaccinated and control gilts in average number of piglets per litter (12.43 and 12.16, respectively), number of live births per litter (11.21 and 11.54), and mean piglet birth weight (3.22 and 3.26 lbs) were not significantly different. Piglets in the control group had significantly greater average daily gain versus piglets from vaccinated gilts (0.52 vs. 0.46 lbs, P<0.0001). Preweaning mortality was significantly greater (P=0.0023) in piglets from the vaccinated gilts (19.7% vs. 10.9%). A single gilt accounted for 18.2% of stillbirths in the vaccinated group. Air samples were borderline PRRSV-PCR-positive for PRRSV on days 29 and 32, after more than 98% of gilts had farrowed. Results demonstrated that vaccination of pregnant gilts at the time of peak fetal susceptibility was non-abortigenic and that the PRRS-MLV agent did not significantly affect reproductive outcomes. Lower ADG in piglets from vaccinated gilts may be due to PRRS-MLV viremia following transplacental or post-farrowing exposure. Air sampling results indicated that environmental contamination with PRRS-MLV shed from vaccinated gilts was minimal.

  4. Photo-induced CO2 reduction by CH4/H2O to fuels over Cu-modified g-C3N4 nanorods under simulated solar energy

    NASA Astrophysics Data System (ADS)

    Tahir, Beenish; Tahir, Muhammad; Amin, Nor Aishah Saidina

    2017-10-01

    Copper modified polymeric graphitic carbon nitride (Cu/g-C3N4) nanorods for photo-induced CO2 conversion with methane (CH4) and water (H2O) as reducing system under simulated solar energy has been investigated. The nanocatalysts, synthesized by pyrolysis and sonication, were characterized by XRD, FTIR, Raman analysis, XPS, SEM, N2 adsorption-desorption and PL spectroscopy. The presence of Cu2+ ions over the g-C3N4 structure inhibited charge carriers recombination process. The results indicated that photo-activity and selectivity of Cu/g-C3N4 photo-catalyst for CO2 reduction greatly dependent on the type of CO2-reduction system. CO2 was efficiently converted to CH4 and CH3OH with traces of C2H4 and C2H6 hydrocarbons in the CO2-water system. The yield of the main product, CH4 over 3 wt.% Cu/g-C3N4 was 109 μmole g-cata.-1 h-1 under visible light irradiation, significantly higher than the pure g-C3N4 catalyst (60 μmole/g.cat). In photo-induced CO2-CH4 reaction, CO and H2 were detected as the main products with smaller amount of hydrocarbons. The highest efficiency was detected over 3 wt.%Cu-loading of g-C3N4 and at optimal CH4/CO2 feed ratio of 1.0. The maximum yield of CO and H2 detected were 142 and 76 μmole g-catal.-1 h-1, respectively at selectivity 66.6% and 32.5%, respectively. Significantly enhanced CO2/CH4 reduction over Cu/g-C3N4 was attributed to its polymeric structure with efficient charge transfer property and inhibited charges recombination rate. A proposed photo-induced reaction mechanism, corroborated with the experimental data, was also deliberated.

  5. Stellar oscillations in modified gravity

    NASA Astrophysics Data System (ADS)

    Sakstein, Jeremy

    2013-12-01

    Starting from the equations of modified gravity hydrodynamics, we derive the equations of motion governing linear, adiabatic, radial perturbations of stars in scalar-tensor theories. There are two new features: first, the eigenvalue equation for the period of stellar oscillations is modified such that the eigenfrequencies are always larger than predicted by general relativity. Second, the general relativity condition for stellar instability is altered so that the adiabatic index can fall below 4/3 before unstable modes appear. Stars are more stable in modified gravity theories. Specializing to the case of chameleonlike theories, we investigate these effects numerically using both polytropic Lane-Emden stars and models coming from modified gravity stellar structure simulations. We find that the change in the oscillation period of Cepheid star models can be as large as 30% for order-one matter couplings and the change in the inferred distance using the period-luminosity relation can be up to three times larger than if one had only considered the modified equilibrium structure. We discuss the implications of these results for recent and upcoming astrophysical tests and estimate that previous methods can produce new constraints such that the modifications are screened in regions of Newtonian potential of O(10-8).

  6. Enamel wear of modified porcelains.

    PubMed

    Imai, Y; Suzuki, S; Fukushima, S

    2000-12-01

    To evaluate the wear of three different modified ceramics along with a conventional porcelain and the wear of opposing enamel at initial wear cycle on a two-body and a three-body wear simulation. Modified ceramics used in this study included a low fusing/low crystal porcelain (Finesse), a high fusing/low crystal porcelain (Softspar), and a heat-pressable ceramic (IPS Empress). A conventional porcelain (Ceramco II) was used as the control material. Hemispherical shaped ceramic styli (1/8 inch in diameter) made of respective materials were fabricated according to the manufacturers' directions. Proximal surfaces of non-carious human molars were ground flat within the enamel with a silicon carbide paper to 600 grit with copious irrigation. They were perpendicularly opposed to each other with or without intermediate material as a food bolus and subjected to in vitro wear test by a UAB wear simulator. A 75.6 N load was applied vertically onto the surface at 1.2 Hz. The surface was duplicated after respective wear cycles. Seven specimens were tested for each group of both simulations. The enamel wear loss when opposing the modified ceramics was less than the Ceramco II control which exhibited the greatest values. The IPS Empress material showed the least amount of wear among them. Statistically significant differences were seen between the IPS Empress and the Ceramco II for every cycle interval evaluated (ANOVA, P < 0.05). Although the enamel wear loss when opposing the IPS Empress was significantly less (ANOVA, P < 0.05) than the others until 20,000 wear cycles, no significant differences were found among the modified ceramics at the end of 50,000 wear cycles. The concentric wear patterns were already prominent at 5,000 wear cycles on two-body wear, however, the wear facet of the three-body wear was smaller (the wear depth of 0-5 microm) than the two-body wear test, as it was quite similar to the one of the two-body wear test at 100 wear cycles. On the other hand

  7. Parallel Atomistic Simulations

    SciTech Connect

    HEFFELFINGER,GRANT S.

    2000-01-18

    Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.

  8. Optimization of modified volume Fresnel zone plates.

    PubMed

    Srisungsitthisunti, Pornsak; Ersoy, Okan K; Xu, Xianfan

    2009-10-01

    Modified volume Fresnel zone plates (MVFZPs) fabricated with laser direct writing were optimized for higher diffraction efficiencies. The Fresnel radii in each layer of a volume zone plate were iteratively adjusted by a simulation-based direct search optimization. The results show that optimization is effective but depends strongly on the starting diffraction efficiencies determined by the MVFZP parameters. The simulations indicate that the optimized MVFZP can achieve 93% diffraction efficiency.

  9. Modifying Curriculum. Module.

    ERIC Educational Resources Information Center

    Petch, Beverly

    This module on modifying curriculum is 1 in a series of 10 modules written for vocational education teacher education programs. It is designed to prepare the learner to identify the varying learning styles of learners and to modify curriculum by providing alternative techniques for curriculum modification. Introductory materials include the…

  10. Modifying toxicokinetics with antidotes.

    PubMed

    Baud, F J; Borron, S W; Bismuth, C

    1995-12-01

    Five approaches may be described through which antidotes can modify toxicokinetics: (1) Decreased bioavailability of the toxins; (2) Cellular redistribution of the toxin in the organism; (3) Promotion of elimination in an unchanged form; (4) Slowing of metabolic activation pathways; (5) Acceleration of metabolic deactivation pathways. However, the ability to modify toxicokinetics with a new treatment, while demonstrating an understanding of the mechanism of action, must never be construed to be, in and of itself, the goal of therapy. The ultimate evaluation of an antidote modifying toxicokinetics is strictly clinical.

  11. 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

  12. Modeling void abundance in modified gravity

    NASA Astrophysics Data System (ADS)

    Voivodic, Rodrigo; Lima, Marcos; Llinares, Claudio; Mota, David F.

    2017-01-01

    We use a spherical model and an extended excursion set formalism with drifting diffusive barriers to predict the abundance of cosmic voids in the context of general relativity as well as f (R ) and symmetron models of modified gravity. We detect spherical voids from a suite of N-body simulations of these gravity theories and compare the measured void abundance to theory predictions. We find that our model correctly describes the abundance of both dark matter and galaxy voids, providing a better fit than previous proposals in the literature based on static barriers. We use the simulation abundance results to fit for the abundance model free parameters as a function of modified gravity parameters, and show that counts of dark matter voids can provide interesting constraints on modified gravity. For galaxy voids, more closely related to optical observations, we find that constraining modified gravity from void abundance alone may be significantly more challenging. In the context of current and upcoming galaxy surveys, the combination of void and halo statistics including their abundances, profiles and correlations should be effective in distinguishing modified gravity models that display different screening mechanisms.

  13. Cystic fibrosis modifier genes.

    PubMed Central

    Davies, Jane; Alton, Eric; Griesenbach, Uta

    2005-01-01

    Since the recognition that CFTR genotype was not a good predictor of pulmonary disease severity in CF, several candidate modifier genes have been identified. It is unlikely that a single modifier gene will be found, but more probable that several haplotypes in combination may contribute, which in itself presents a major methodological challenge. The aims of such studies are to increase our understanding of disease pathogenesis, to aid prognosis and ultimately to lead to the development of novel treatments. PMID:16025767

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Modified PRISM theory for confined polymers.

    PubMed

    Xu, Mengjin; Zhang, Chen; Du, Zhongjie; Mi, Jianguo

    2012-11-14

    We propose a modified polymer reference interaction site model (PRISM) to describe the interfacial density profiles of polymers in contact with planar and curved solid surfaces. In the theoretical approach, a bridge function derived from density functional method is included. In description of hard-sphere polymer at planar and curved surfaces with an arbitrary external field, the effect of modification has been validated by the available simulation data, except for low density system. When extended to confined real systems, the modified theoretical model also shows an encouraging prospect in description of the interfacial structure and properties.

  19. 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

  20. Modifying Cookbook Labs.

    ERIC Educational Resources Information Center

    Clark, Robert, L.; Clough, Michael P.; Berg, Craig A.

    2000-01-01

    Modifies an extended lab activity from a cookbook approach for determining the percent mass of water in copper sulfate pentahydrate crystals to one which incorporates students' prior knowledge, engenders active mental struggling with prior knowledge and new experiences, and encourages metacognition. (Contains 12 references.) (ASK)

  1. Modifying Cookbook Labs.

    ERIC Educational Resources Information Center

    Clark, Robert, L.; Clough, Michael P.; Berg, Craig A.

    2000-01-01

    Modifies an extended lab activity from a cookbook approach for determining the percent mass of water in copper sulfate pentahydrate crystals to one which incorporates students' prior knowledge, engenders active mental struggling with prior knowledge and new experiences, and encourages metacognition. (Contains 12 references.) (ASK)

  2. Triple rule-out CT angiography protocol with restricting field of view for detection of pulmonary thromboembolism and aortic dissection in emergency department patients: simulation of modified CT protocol for reducing radiation dose.

    PubMed

    Kim, Hyun Su; Kim, Sung Mok; Cha, Min Jae; Kim, Yoo Na; Kim, Hae Jin; Choi, Jin-Ho; Choe, Yeon Hyeon

    2017-05-01

    Background Triple rule-out computed tomography (TRO CT) is a CT protocol designed to simultaneously evaluate the coronary, aorta, and pulmonary arteries. Purpose To evaluate potential diagnostic performance of TRO CT with restricted volume coverage for detection of pulmonary thromboembolism (PTE) and aortic dissection (AD). Material and Methods This study included 1224 consecutive patients with acute chest pain who visited the emergency department and underwent TRO CT using a 128-slice dual-source CT. Image data were reconstructed according to the display field of view (DFOV) of coronary CT angiography (CCTA) and TRO CT protocols in each patient. The presence of PTE and AD was evaluated by independent observers in each DFOV. The radiation dose was calculated to evaluate the potential benefits by restricting z-axis coverage to cardiac scan range instead of the whole thorax. Results Among all patients, 22 cases with PTE (1.9%) and nine cases with AD (0.8%) were found. Except for one PTE case, all cases were detected on both DFOV of TRO CT and CCTA. Mean effective dose for evaluation of entire thorax and cardiac scan coverage were 5.9 ± 1.1 mSv and 3.5 ± 0.7 mSv, respectively. Conclusion Isolated PTE and AD outside the CCTA DFOV rarely occur. Therefore, modified TRO CT protocol using cardiac scan coverage can be adopted to detect PTE and AD with reduced radiation dose.

  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. Time domain analog circuit simulation

    NASA Astrophysics Data System (ADS)

    Fijnvandraat, J. G.; Houben, S. H. M. J.; Ter Maten, E. J. W.; Peters, J. M. F.

    2006-01-01

    Recent developments of new methods for simulating electric circuits are described. Emphasis is put on methods that fit existing datastructures for backward differentiation formulae methods. These methods can be modified to apply to hierarchically organized datastructures, which allows for efficient simulation of large designs of circuits in the electronics industry.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Efficiency of monolaurin in mitigating ruminal methanogenesis and modifying C-isotope fractionation when incubating diets composed of either C3 or C4 plants in a rumen simulation technique (Rusitec) system.

    PubMed

    Klevenhusen, Fenja; Bernasconi, Stefano M; Hofstetter, Thomas B; Bolotin, Jakov; Kunz, Carmen; Soliva, Carla R

    2009-11-01

    Mitigation of methanogenesis in ruminants has been an important goal for several decades. Free lauric acid, known to suppress ruminal methanogenesis, has a low palatability; therefore, in the present study the aim was to evaluate the mitigation efficacy of its esterified form (monolaurin). Further, 13C-isotope abundance (delta13C) and 13C-12C fractionation during methanogenesis and fermentation were determined to evaluate possible microbial C-isotope preferences. Using the rumen simulation technique, four basal diets, characterised either by the C3 plants grass (hay) and wheat (straw and grain), or the C4 plant (13C excess compared with C3 plants) maize (straw and grain), and a mixture of the latter two, were incubated with and without monolaurin (50 g/kg dietary DM). Added to hay, monolaurin did not significantly affect methanogenesis. When added to the other diets (P < 0.05 for the wheat-based diet) methane formation was lowered. Monolaurin decreased fibre disappearance (least effect with the hay diet), acetate:propionate ratio, and protozoal counts. Feed residues and SCFA showed the same delta13C as the diets. Methane was depleted in 13C while CO2 was enriched in 13C compared with the diets. Monolaurin addition resulted in 13C depletion of CO2 and enrichment in CH4 (the latter only in the hay diet). In conclusion, monolaurin proved to effectively decrease methanogenesis in the straw-grain diets although this effect might partly be explained by the concomitantly reduced fibre disappearance. The influence on 13C-isotope abundance and fractionation supports the hypothesis that ruminal microbes seem to differentiate to some extent between C-isotopes during methanogenesis and fermentation.

  11. 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.

  12. Histone Modifiers in Cancer

    PubMed Central

    Cohen, Idan; Poręba, Elżbieta; Kamieniarz, Kinga; Schneider, Robert

    2011-01-01

    Covalent modifications of histones can regulate all DNA-dependent processes. In the last few years, it has become more and more evident that histone modifications are key players in the regulation of chromatin states and dynamics as well as in gene expression. Therefore, histone modifications and the enzymatic machineries that set them are crucial regulators that can control cellular proliferation, differentiation, plasticity, and malignancy processes. This review discusses the biology and biochemistry of covalent histone posttranslational modifications (PTMs) and evaluates the dual role of their modifiers in cancer: as oncogenes that can initiate and amplify tumorigenesis or as tumor suppressors. PMID:21941619

  13. Modified harmony search

    NASA Astrophysics Data System (ADS)

    Mohamed, Najihah; Lutfi Amri Ramli, Ahmad; Majid, Ahmad Abd; Piah, Abd Rahni Mt

    2017-09-01

    A metaheuristic algorithm, called Harmony Search is quite highly applied in optimizing parameters in many areas. HS is a derivative-free real parameter optimization algorithm, and draws an inspiration from the musical improvisation process of searching for a perfect state of harmony. Propose in this paper Modified Harmony Search for solving optimization problems, which employs a concept from genetic algorithm method and particle swarm optimization for generating new solution vectors that enhances the performance of HS algorithm. The performances of MHS and HS are investigated on ten benchmark optimization problems in order to make a comparison to reflect the efficiency of the MHS in terms of final accuracy, convergence speed and robustness.

  14. Modified arthroscopic Brostrom procedure.

    PubMed

    Lui, Tun Hing

    2015-09-01

    The open modified Brostrom anatomic repair technique is widely accepted as the reference standard for lateral ankle stabilization. However, there is high incidence of intra-articular pathologies associated with chronic lateral ankle instability which may not be addressed by an isolated open Brostrom procedure. Arthroscopic Brostrom procedure with suture anchor has been described for anatomic repair of chronic lateral ankle instability and management of intra-articular lesions. However, the complication rates seemed to be higher than open Brostrom procedure. Modification of the arthroscopic Brostrom procedure with the use of bone tunnel may reduce the risk of certain complications.

  15. 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.

  16. 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…

  17. Fast route to nonlinear clustering statistics in modified gravity theories

    NASA Astrophysics Data System (ADS)

    Winther, Hans A.; Ferreira, Pedro G.

    2015-06-01

    We propose a simple and computationally fast method for performing N -body simulations for a large class of modified gravity theories with a screening mechanism such as chameleons, symmetrons, and Galileons. By combining the linear Klein-Gordon equation with a screening factor, calculated from analytical solutions of spherical symmetric configurations, we obtain a modified field equation of which the solution is exact in the linear regime while at the same time taking screening into account on nonlinear scales. The resulting modified field equation remains linear and can be solved just as quickly as the Poisson equation without any of the convergence problems that can arise when solving the full equation. We test our method with N -body simulations and find that it compares remarkably well with full simulations well into the nonlinear regime.

  18. Rheological Modifiers and Wetting Agents

    SciTech Connect

    Chun, Jaehun; Hansen, Erich; Berg, John C.

    2009-10-01

    DOE tank waste treatment plants, the Waste Treatment Plant (WTP) at Hanford and Defense Waste Processing Facility (DWPF) at Savannah River, are designed to vitrify radioactive waste slurries for long-term storage. Plant throughput is currently limited by the waste solids loading. To increase waste throughput rates in the plant, an increase in the slurry solids concentration (or conversely, a reduction in the mass fraction of water in the waste) is being considered. However, the present mechanical designs used to mix and transport theses slurries are limited by the rheological properties. This reduction of water results in an increase in rheological properties that challenge plant design and performance. To support this increase in throughput, there is a need to reduce the rheological properties of these waste slurries. The objective of this project is to determine a small set of well-performing and commercially available rheological modifiers that allow control rheological properties of various simulated and actual waste slurries and to understand the physical mechanisms that govern modification of waste rheology. It is estimated that processing at a higher solids concentration will reduce the operating life of these plants by one year for both facilities, representing roughly $1B in lifecycle cost savings. In addition, this research is potentially important to sustainable operations of both WTP and DWPF

  19. 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

  20. Large-scale circuit simulation

    NASA Astrophysics Data System (ADS)

    Wei, Y. P.

    1982-12-01

    The simulation of VLSI (Very Large Scale Integration) circuits falls beyond the capabilities of conventional circuit simulators like SPICE. On the other hand, conventional logic simulators can only give the results of logic levels 1 and 0 with the attendent loss of detail in the waveforms. The aim of developing large-scale circuit simulation is to bridge the gap between conventional circuit simulation and logic simulation. This research is to investigate new approaches for fast and relatively accurate time-domain simulation of MOS (Metal Oxide Semiconductors), LSI (Large Scale Integration) and VLSI circuits. New techniques and new algorithms are studied in the following areas: (1) analysis sequencing (2) nonlinear iteration (3) modified Gauss-Seidel method (4) latency criteria and timestep control scheme. The developed methods have been implemented into a simulation program PREMOS which could be used as a design verification tool for MOS circuits.

  1. Computational mesomechanics of surface-modified titanium

    NASA Astrophysics Data System (ADS)

    Balokhonov, R. R.; Martynov, S. A.; Romanova, V. A.; Panin, A. V.; Kazachenok, M. S.; Batukhtina, E. E.; Shakhijanov, V. S.

    2016-11-01

    A numerical simulation is performed to investigate the mesoscale stress-strain localization in a surface-modified commercial titanium alloy (VT1-0 according to Russian classification). The calculated crystalline microstructure corresponds to that observed experimentally and is explicitly accounted for as initial conditions of a dynamic boundary-value problem. The latter is formulated in terms of plane strain developing in a microstructure subjected to tension and is solved numerically by the finite-difference method. Elastic-plastic constitutive models are built to describe the experimental mechanical responses both of the substrate and of the modified layer. The plastic strain localization is found to depend on the grain yield stress.

  2. Polysaccharide biological response modifiers.

    PubMed

    Leung, M Y K; Liu, C; Koon, J C M; Fung, K P

    2006-06-15

    Biological response modifiers (BRMs) are substances which augment immune response. BRMs can be cytokines which are produced endogenously in our body by immune cells or derivatives of bacteria, fungi, brown algae, Aloe vera and photosynthetic plants. Such exogeneous derivatives (exogeneous BRMs) can be nucleic acid (CpG), lipid (lipotechoic acid), protein or polysaccharide in nature. The receptors for these exogeneous BRMs are pattern recognition receptors. The binding of exogeneous BRMs to pattern recognition receptors triggers immune response. Exogenous BRMs have been reported to have anti-viral, anti-bacterial, anti-fungal, anti-parasitic, and anti-tumor activities. Among different exogeneous BRMs, polysaccharide BRMs have the widest occurrence in nature. Some polysaccharide BRMs have been tested for their therapeutic properties in human clinical trials. An overview of current understandings of polysaccharide BRMs is summarized in this review.

  3. 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.

  4. 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.

  5. 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.

  6. OMV mission simulator

    NASA Technical Reports Server (NTRS)

    Cok, Keith E.

    1989-01-01

    The Orbital Maneuvering Vehicle (OMV) will be remotely piloted during rendezvous, docking, or proximity operations with target spacecraft from a ground control console (GCC). The real-time mission simulator and graphics being used to design a console pilot-machine interface are discussed. A real-time orbital dynamics simulator drives the visual displays. The dynamics simulator includes a J2 oblate earth gravity model and a generalized 1962 rotating atmospheric and drag model. The simulator also provides a variable-length communication delay to represent use of the Tracking and Data Relay Satellite System (TDRSS) and NASA Communications (NASCOM). Input parameter files determine the graphics display. This feature allows rapid prototyping since displays can be easily modified from pilot recommendations. A series of pilot reviews are being held to determine an effective pilot-machine interface. Pilots fly missions with nominal to 3-sigma dispersions in translational or rotational axes. Console dimensions, switch type and layout, hand controllers, and graphic interfaces are evaluated by the pilots and the GCC simulator is modified for subsequent runs. Initial results indicate a pilot preference for analog versus digital displays and for two 3-degree-of-freedom hand controllers.

  7. Attitude Estimation Using Modified Rodrigues Parameters

    NASA Technical Reports Server (NTRS)

    Crassidis, John L.; Markley, F. Landis

    1996-01-01

    In this paper, a Kalman filter formulation for attitude estimation is derived using the Modified Rodrigues Parameters. The extended Kalman filter uses a gyro-based model for attitude propagation. Two solutions are developed for the sensitivity matrix in the Kalman filter. One is based upon an additive error approach, and the other is based upon a multiplicative error approach. It is shown that the two solutions are in fact equivalent. The Kalman filter is then used to estimate the attitude of a simulated spacecraft. Results indicate that then new algorithm produces accurate attitude estimates by determining actual gyro biases.

  8. 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.

  9. 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.

  10. [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.

  11. Simulation of the modified K reactor supplementary safety system

    SciTech Connect

    Paik, I.K.; Canas, L.R. ); Peterson, P.F. )

    1991-01-01

    The supplementary safety system (SSS) of the K reactor provides a second line of defense to shut down the reactor if the safety and control rods fail to scram. The SSS was originally designed to inject a neutron poison solution (ink) into the reactor tank via spargers. Recently, concerns arose that the ink inventory might run out before the ink front returned to the moderator during a loss-of-ac-power transient in which the coolant pumps coast down. Thus, a new system has been added to inject additional ink through the pump suctions so that ink will arrive in the core before depletion of the sparger ink. The MODFLOW code was developed to calculate the moderator flow distribution in Savannah River site (SRS) reactors, including the effects of inertia and stratification from buoyancy forces.

  12. Airwake Simulation of Modified TTCP/SFS Ship

    DTIC Science & Technology

    2003-03-01

    shape of the air burble (airwake) might be misleading in the perspective view. The burble is symmetric when the eyepoint is set at the center plane. Of...course the height, as well as the overall size, of the air burble grows as the flow proceeds downstream. The height can be twice as much as shown here

  13. 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).

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. On a modified electrodynamics

    PubMed Central

    Reiss, H.R.

    2012-01-01

    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. PMID:23105173

  19. Numerical study of underwater shock wave by a modified method of characteristics

    NASA Astrophysics Data System (ADS)

    Li, Xiaojie; Zhang, Chengjiao; Wang, Xiaohong; Hu, Xiaofei

    2014-03-01

    This paper introduces a modified method of characteristics as well as its application to simulation of a 1D spherical underwater explosion. To check the performance of the modified method, corresponding codes for computer calculation are developed to simulate the underwater explosion problem which is a typical isentropic flow problem. In applying the modified method, shock wave is calculated based on the Rankine-Hugoniot conservation relations. Artificial viscosity is not used in the simulation, and thus the corresponding influence of artificial viscosity is not introduced into the simulation. The work is mainly focused on underwater shock wave and secondary shock wave. The results simulated with the modified method are compared with other results from experiment and AUTODYN software, and the comparisons show that the modified method results are coincident with the experimental results in acceptable accuracy. Compared with the AUTODYN results, the modified method results are consistent with the experimental results better in far field. The formation and propagation of the secondary shock and the position of the gas-water interface are well captured, and the variations in flow field can be obtained. On the basis of the comparisons, it can be demonstrated that the modified method of characteristics can be applied to the simulation of 1D isentropic flow problems effectively.

  20. Genetically modified foods and allergy.

    PubMed

    Lee, T H; Ho, H K; Leung, T F

    2017-06-01

    2015 marked the 25th anniversary of the commercial use and availability of genetically modified crops. The area of planted biotech crops cultivated globally occupies a cumulative two billion hectares, equivalent to twice the land size of China or the United States. Foods derived from genetically modified plants are widely consumed in many countries and genetically modified soybean protein is extensively used in processed foods throughout the industrialised countries. Genetically modified food technology offers a possible solution to meet current and future challenges in food and medicine. Yet there is a strong undercurrent of anxiety that genetically modified foods are unsafe for human consumption, sometimes fuelled by criticisms based on little or no firm evidence. This has resulted in some countries turning away food destined for famine relief because of the perceived health risks of genetically modified foods. The major concerns include their possible allergenicity and toxicity despite the vigorous testing of genetically modified foods prior to marketing approval. It is imperative that scientists engage the public in a constructive evidence-based dialogue to address these concerns. At the same time, improved validated ways to test the safety of new foods should be developed. A post-launch strategy should be established routinely to allay concerns. Mandatory labelling of genetically modified ingredients should be adopted for the sake of transparency. Such ingredient listing and information facilitate tracing and recall if required.

  1. 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…

  2. Modified Gravity and Coupled Quintessence

    NASA Astrophysics Data System (ADS)

    Wetterich, Christof

    The distinction between modified gravity and quintessence or dynamical dark energy is difficult. Many models of modified gravity are equivalent to models of coupled quintessence by virtue of variable transformations. This makes an observational differentiation between modified gravity and dark energy very hard. For example, the additional scalar degree of freedom in f(R)-gravity or non-local gravity can be interpreted as the cosmon of quintessence. Nevertheless, modified gravity can shed light on questions of interpretation, naturalness and simplicity. We present a simple model where gravity is modified by a field dependent Planck mass. It leads to a universe with a cold and slow beginning. This cosmology can be continued to the infinite past such that no big bang singularity occurs. All observables can be described equivalently in a hot big bang picture with inflation and early dark energy.

  3. Active optics simulation system

    NASA Technical Reports Server (NTRS)

    Chi, C. H.

    1973-01-01

    The active optics simulation system (AOSS) is a set of computer programs and associated software to be used in the development, design, and evaluation of a primary mirror control system for a large space telescope, (e.g., the tentatively proposed 3-meter telescope). The mathematical models of component subsystems and the solution of the physical processes that occur within the mirror surface control system were obtained, and based on these models AOSS simulates the behavior of the entire mirror surface control system as well as the behavior of the component subsystems. The program has a modular structure so that any subsystem module can be replaced or modified with minimum disruption of the rest of the simulation program.

  4. AN-102 Simulant Sr/TRU Precipitation and Ultrafiltration

    SciTech Connect

    Zamecnik, J.R.

    2003-04-28

    The objective of these tests was to gather data on performance of the single-tube crossflow ultrafilter unit to de-water the simulant precipitate derived from a project approved tank 241-AN-102 simulant. Upon completion of the objectives with the approved R1 simulant, the simulant specification was changed and additional work at modified precipitation conditions was requested.

  5. Simulating cut-to-length harvesting operations in Appalachian hardwoods

    Treesearch

    Jingxin Wang; Chris B. LeDoux; Yaoxiang Li

    2005-01-01

    Cut-to-length (CTL) harvesting systems involving small and large harvesters and a forwarder were simulated using a modular computer simulation model. The two harvesters simulated were a modified John Deere 988 tracked excavator with a single grip sawhead and a Timbco T425 based excavator with a single grip sawhead. The forwarder used in the simulations was a Valmet 524...

  6. Removing ammonium from water using modified corncob-biochar.

    PubMed

    Vu, Thi Mai; Trinh, Van Tuyen; Doan, Dinh Phuong; Van, Huu Tap; Nguyen, Tien Vinh; Vigneswaran, Saravanamuthu; Ngo, Huu Hao

    2017-02-01

    Ammonium pollution in groundwater and surface water is of major concern in many parts of the world due to the danger it poses to the environment and people's health. This study focuses on the development of a low cost adsorbent, specifically a modified biochar prepared from corncob. Evaluated here is the efficiency of this new material for removing ammonium from synthetic water (ammonium concentration from 10 to 100mg/L). The characteristics of the modified biochar were determined by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). It was found that ammonium adsorption on modified biochar strongly depended on pH. Adsorption kinetics of NH4(+)-N using modified biochar followed the pseudo-second order kinetic model. Both Langmuir and Sips adsorption isotherm models could simulate well the adsorption behavior of ammonium on modificated biochar. The highest adsorption capacity of 22.6mg NH4(+)-N/g modified biochar was obtained when the biochar was modified by soaking it in HNO3 6M and NaOH 0.3M for 8h and 24h, respectively. The high adsorption capacity of the modified biochar suggested that it is a promising adsorbent for NH4(+)-N remediation from water.

  7. Simulations of vortex generators

    NASA Technical Reports Server (NTRS)

    Koumoutsakos, P.

    1995-01-01

    We are interested in the study, via direct numerical simulations, of active vortex generators. Vortex generators may be used to modify the inner part of the boundary layer or to control separation thus enhancing the performance and maneuverability of aerodynamic configurations. We consider generators that consist of a surface cavity elongated in the stream direction and partially covered with a moving lid that at rest lies flush with the boundary. Streamwise vorticity is generated and ejected due to the oscillatory motion of the lid. The present simulations complement relevant experimental investigations of active vortex generators at NASA Ames and Stanford University (Saddoughi, 1994, and Jacobson and Reynolds, 1993). Jacobson and Reynolds (1993) used a piezoelectric device in water, allowing for small amplitude high frequency oscillations. They placed the lid asymmetrically on the cavity and observed a strong outward velocity at the small gap of the cavity. Saddoughi used a larger mechanically driven device in air to investigate this flow and he observed a jet emerging from the wide gap of the configuration, contrary to the findings of Jacobson and Reynolds. Our task is to simulate the flows generated by these devices and to conduct a parametric study that would help us elucidate the physical mechanisms present in the flow. Conventional computational schemes encounter difficulties when simulating flows around complex configurations undergoing arbitrary motions. Here we present a formulation that achieves this task on a purely Lagrangian frame by extending the formulation presented by Koumoutsakos, Leonard and Pepin (1994). The viscous effects are taken into account by modifying the strength of the particles, whereas fast multipole schemes employing hundreds of thousands of particles allow for high resolution simulations. The results of the present simulations would help us assess some of the effects of three-dimensionality in experiments and investigate the role

  8. 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

  9. Sunlight Simulator for Photovoltaic Testing

    NASA Technical Reports Server (NTRS)

    Mueller, R. L.

    1986-01-01

    Light with normalized spectral irradiance resembling that of airmass 1.5 sunlight striking surface of Earth produced by use of ultraviolet filter to modify output of set of flashlamps used as large-area pulsed solar simulator (LAPSS). Filtered LAPSS light allows more realistic measurements of output of photovoltaic devices when using silicon reference cell having different spectral response characteristic.

  10. 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...

  11. 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...

  12. 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.

  13. 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.

  14. JASMINE simulator

    NASA Astrophysics Data System (ADS)

    Ueda, Seiji; Yamada, Yoshiyuki; Kuwabara, Takashi; Gouda, Naoteru; Tsujimoto, Takuji; Kobayashi, Yukiyasu; Nakajima, Tadashi; Matsuhara, Hideo; Yano, Taihei; Suganuma, Masahiro; Jasmine Working Group

    2005-04-01

    We explain simulation tools in the JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Therefore it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. We find that new software technologies, such as Object Oriented (OO) methodologies, are ideal tools for the simulation system of JASMINE (the JASMINE simulator). In this article, we explain the framework of the JASMINE simulator.

  15. Aftershocks and Omori's law in a modified Carlson-Langer model with nonlinear viscoelasticity

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Hidetsugu; Okamura, Kazuki

    2015-05-01

    A modified Carlson-Langer model for earthquakes is proposed, which includes nonlinear viscoelasticity. Several aftershocks are generated after the main shock owing to the damping of the additional viscoelastic force. Both the Gutenberg-Richter law and Omori's law are reproduced in a numerical simulation of the modified Carlson-Langer model on a critical percolation cluster of a square lattice.

  16. Reduced-Order Biogeochemical Flux Model for High-Resolution Multi-Scale Biophysical Simulations

    NASA Astrophysics Data System (ADS)

    Smith, Katherine; Hamlington, Peter; Pinardi, Nadia; Zavatarelli, Marco

    2017-04-01

    Biogeochemical tracers and their interactions with upper ocean physical processes such as submesoscale circulations and small-scale turbulence are critical for understanding the role of the ocean in the global carbon cycle. These interactions can cause small-scale spatial and temporal heterogeneity in tracer distributions that can, in turn, greatly affect carbon exchange rates between the atmosphere and interior ocean. For this reason, it is important to take into account small-scale biophysical interactions when modeling the global carbon cycle. However, explicitly resolving these interactions in an earth system model (ESM) is currently infeasible due to the enormous associated computational cost. As a result, understanding and subsequently parameterizing how these small-scale heterogeneous distributions develop and how they relate to larger resolved scales is critical for obtaining improved predictions of carbon exchange rates in ESMs. In order to address this need, we have developed the reduced-order, 17 state variable Biogeochemical Flux Model (BFM-17) that follows the chemical functional group approach, which allows for non-Redfield stoichiometric ratios and the exchange of matter through units of carbon, nitrate, and phosphate. This model captures the behavior of open-ocean biogeochemical systems without substantially increasing computational cost, thus allowing the model to be combined with computationally-intensive, fully three-dimensional, non-hydrostatic large eddy simulations (LES). In this talk, we couple BFM-17 with the Princeton Ocean Model and show good agreement between predicted monthly-averaged results and Bermuda testbed area field data (including the Bermuda-Atlantic Time-series Study and Bermuda Testbed Mooring). Through these tests, we demonstrate the capability of BFM-17 to accurately model open-ocean biochemistry. Additionally, we discuss the use of BFM-17 within a multi-scale LES framework and outline how this will further our understanding

  17. 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.

  18. 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)

  19. JASMINE simulator

    NASA Astrophysics Data System (ADS)

    Yamada, Yoshiyuki; Gouda, Naoteru; Yano, Taihei; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Suganuma, Masahiro; Niwa, Yoshito; Sako, Nobutada; Hatsutori, Yoichi; Tanaka, Takashi

    2006-06-01

    We explain simulation tools in JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Then it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations into error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. Of course, component simulations are needed, but total simulations which include all components from observation target to satellite system are also very important. We find that new software technologies, such as Object Oriented(OO) methodologies are ideal tools for the simulation system of JASMINE(the JASMINE simulator). In this article, we explain the framework of the JASMINE simulator.

  20. Bioactive aldehyde-modified phosphatidylethanolamines.

    PubMed

    Guo, Lilu; Davies, Sean S

    2013-01-01

    Lipid peroxidation generates a variety of lipid aldehydes, which have been recognized to modify protein and DNA, causing inflammation and cancer. However, recent studies demonstrate that phosphatidylethanolamine (PE) is a major target for these aldehydes, forming aldehyde-modified PEs (al-PEs) as a novel family of mediators for inflammation. This review summarizes our current understanding of these al-PEs, including formation, detection, structural characterization, physiological relevance and mechanism of action. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  1. 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.

  2. 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.

  3. Arthroscopically Assisted Modified Jones Procedure.

    PubMed

    Lui, Tun Hing

    2016-12-01

    The modified Jones procedure is the classic operative treatment of symptomatic clawed hallux. It is composed of transfer of the extensor hallucis longus tendon to the first metatarsal neck and fusion of the hallux interphalangeal joint. The purpose of this technical note is to report the technique of an arthroscopically assisted modified Jones procedure. This can be combined with other minimally invasive bone and soft-tissue procedures to correct all aspects of the complex cavus foot deformity.

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

    PubMed

    Hwang, Alex D; Peli, Eli

    2013-07-01

    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.

  5. 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.

  6. Uptake of inorganic carbon and nitrate by marine plankton and the Redfield ratio

    SciTech Connect

    Banse, K. )

    1994-03-01

    This paper reexamines the previously studied question of uptake ratios of dissolved inorganic carbon and nitrate in plankton blooms. The author concludes that unless explicit justification is provided, nitrate consumption cannot be converted into community net production of particulate and dissolved organic carbon. 17 refs., 2 figs.

  7. Chemically modified diamondoids as biosensors for DNA

    NASA Astrophysics Data System (ADS)

    Sivaraman, Ganesh; Fyta, Maria

    2014-03-01

    Understanding the interaction of biological molecules with materials is essential in view of the novel potential applications arising when these two are combined. To this end, we investigate the interaction of DNA with diamondoids, a broad family of tiny hydrogen-terminated diamond clusters with high technological potential. We model this interaction through quantum-mechanical computer simulations and focus on the hydrogen bonding possibilities of the different DNA nucleobases to the lower amine-modified diamondoids with respect to their relative distance and orientation. Our aim is to promote the binding between these two units, and probe this through the association energy, the electronic structure of the nucleobase-diamondoid system, and the specific role of their frontier orbitals. We discuss the relevance of our results in view of biosensing applications and specifically nanopore sequencing of DNA.

  8. Modified impulsive synchronization of hyperchaotic systems

    NASA Astrophysics Data System (ADS)

    Haeri, Mohammad; Dehghani, Mahsa

    2010-03-01

    In an original impulsive synchronization only instantaneous errors are used to determine the impulsive inputs. To improve the synchronization performance, addition of an integral term of the errors is proposed here. In comparison with the original form, the proposed modification increases the impulse distances which leads to reduction in the control cost as the most important characteristic of the impulsive synchronization technique. It can also decrease the error magnitude in the presence of noise. Sufficient conditions are presented through four theorems for different situations (nominal, uncertain, noisy, and noisy uncertain cases) under which stability of the error dynamics is guaranteed. Results from computer based simulations are provided to illustrate feasibility and effectiveness of the modified impulsive synchronization method applied on Rossler hyperchaotic systems.

  9. Modified soxhlet extractor for pedologic studies

    SciTech Connect

    Sobek, A.A.; Bambenek, M.A.; Meyer, D.

    1982-11-01

    The soxhlet apparatus has been used in the laboratory to stimulate geochemical weathering; however, the high extraction temperatures required in the soxhlet do not represent a realistic simulation of the weathering environment. A modified design of the original soxhlet did not eliminate the problems of extraction temperature or inaccurate volumes of solvent passing through the sample. These problems were solved by moving the extraction chamber away from the upward path of the refluxing solvent. Extraction temperature differences (approximately 52/sup 0/C) were responsible for higher concentrations of leachate metal in the original soxhlet leachate when a minesoil sample was weathered. This modification permits exact volumes of solvent to be passed through the sample, as well as a reduction in extraction temperature that would allow study of the role of bacteria in the weathering process.

  10. Notes on the Modified Nonlinear Schrodinger Equation

    NASA Astrophysics Data System (ADS)

    Pizzo, N. E.; Melville, W. K.

    2011-12-01

    In this study, we present the derivation of a modified Nonlinear Schrodinger equation (MNLSE) based on variational calculus. Using weakly nonlinear theory we derive an averaged Lagrangian, which in turn yields a slightly modified version of the MNLSE that conserves wave action. We also explore ramifications of the MNLSE with respect to the coupling between mean currents and non-uniform radiation stresses. We present this in the context of breaking waves and the free long waves they generate (Kristian Dysthe, personal communication). It has been noted in laboratory experiments (Meza et al, 1999) that breaking waves transfer some energy to modes far below the peak frequency of the spectrum. The transfer mechanism is widely believed to be the result of nonlinear four wave resonant interactions; however, the coupling between breaking-induced non-uniform radiation stresses and long wave radiation suggests a potential alternative explanation. Through direct numerical simulations, along with the theory, we test the feasibility of this mechanism by comparing it to data from wave tank experiments (Drazen et al., 2008).

  11. 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.

  12. Detection and Classification of Power Quality Disturbancewaveform Using MRA Based Modified Wavelet Transfrom and Neural Networks

    NASA Astrophysics Data System (ADS)

    Chandrasekar, Perumal; Kamaraj, Vijayarajan

    2010-07-01

    In this paper, the modified wavelet based artificial neural network (ANN) is implemented and tested for power signal disturbances. The power signal is decomposed by using modified wavelet transform and the classification is carried by using ANN. Discrete modified wavelet transforms based signal decomposition technique is integrated with the back propagation artificial neural network model is proposed. Varieties of power quality events including voltage sag, swell, momentary interruption, harmonics, transient oscillation and voltage fluctuation are used to test the performance of the proposed approach. The simulation is carried out by using MATLAB software. The simulation results show that the proposed scheme offers superior detection and classification compared to the conventional approaches.

  13. Model selection for modified gravity.

    PubMed

    Kitching, T D; Simpson, F; Heavens, A F; Taylor, A N

    2011-12-28

    In this article, we review model selection predictions for modified gravity scenarios as an explanation for the observed acceleration of the expansion history of the Universe. We present analytical procedures for calculating expected Bayesian evidence values in two cases: (i) that modified gravity is a simple parametrized extension of general relativity (GR; two nested models), such that a Bayes' factor can be calculated, and (ii) that we have a class of non-nested models where a rank-ordering of evidence values is required. We show that, in the case of a minimal modified gravity parametrization, we can expect large area photometric and spectroscopic surveys, using three-dimensional cosmic shear and baryonic acoustic oscillations, to 'decisively' distinguish modified gravity models over GR (or vice versa), with odds of ≫1:100. It is apparent that the potential discovery space for modified gravity models is large, even in a simple extension to gravity models, where Newton's constant G is allowed to vary as a function of time and length scale. On the time and length scales where dark energy dominates, it is only through large-scale cosmological experiments that we can hope to understand the nature of gravity.

  14. Modeling covalent-modifier drugs.

    PubMed

    Awoonor-Williams, Ernest; Walsh, Andrew G; Rowley, Christopher N

    2017-05-18

    In this review, we present a summary of how computer modeling has been used in the development of covalent-modifier drugs. Covalent-modifier drugs bind by forming a chemical bond with their target. This covalent binding can improve the selectivity of the drug for a target with complementary reactivity and result in increased binding affinities due to the strength of the covalent bond formed. In some cases, this results in irreversible inhibition of the target, but some targeted covalent inhibitor (TCI) drugs bind covalently but reversibly. Computer modeling is widely used in drug discovery, but different computational methods must be used to model covalent modifiers because of the chemical bonds formed. Structural and bioinformatic analysis has identified sites of modification that could yield selectivity for a chosen target. Docking methods, which are used to rank binding poses of large sets of inhibitors, have been augmented to support the formation of protein-ligand bonds and are now capable of predicting the binding pose of covalent modifiers accurately. The pKa's of amino acids can be calculated in order to assess their reactivity towards electrophiles. QM/MM methods have been used to model the reaction mechanisms of covalent modification. The continued development of these tools will allow computation to aid in the development of new covalent-modifier drugs. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. JASMINE Simulator

    NASA Astrophysics Data System (ADS)

    Yamada, Y.; Gouda, N.; Yano, T.; Kobayashi, Y.; Suganuma, M.; Tsujimoto, T.; Sako, N.; Hatsutori, Y.; Tanaka, T.

    2006-08-01

    We explain simulation tools in JASMINE project (JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Then it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. Of course, component simulations are needed, but total simulations which include all components from observation target to satellite system are also very important. We find that new software technologies, such as Object Oriented (OO) methodologies are ideal tools for the simulation system of JASMINE (the JASMINE simulator). The simulation system should include all objects in JASMINE such as observation techniques, models of instruments and bus design, orbit, data transfer, data analysis etc. in order to resolve all issues which can be expected beforehand and make it easy to cope with some unexpected problems which might occur during the mission of JASMINE. So, the JASMINE Simulator is designed as handling events such as photons from astronomical objects, control signals for devices, disturbances for satellite attitude, by instruments such as mirrors and detectors, successively. The simulator is also applied to the technical demonstration "Nano-JASMINE". The accuracy of ordinary sensor is not enough for initial phase attitude control. Mission instruments may be a good sensor for this purpose. The problem of attitude control in initial phase is a good example of this software because the problem is closely related to both mission instruments and satellite bus systems.

  16. 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.

  17. Modifying the temporal profile of the high-potency sweetener neotame.

    PubMed

    Prakash, I; Bishay, I E; Desai, N; Walters, D E

    2001-02-01

    It is possible, using hydrophobic organic acids (such as cinnamate) or hydroxyamino acids (such as serine and tyrosine), to modify the temporal profile of the high-potency sweetener neotame. On the basis of Monte Carlo simulations, it was concluded that it is unlikely that this effect is due to direct interaction between the neotame molecule and the taste modifier. It is shown, using conformational analysis and molecular modeling, that the taste modifiers can adopt low-energy conformers which mimic the proposed active conformation of neotame, which suggests that the modifiers may compete for binding at the receptor site.

  18. 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

  19. Modifying Knowledge, Emotions, and Attitudes Regarding Genetically Modified Foods

    ERIC Educational Resources Information Center

    Heddy, Benjamin C.; Danielson, Robert W.; Sinatra, Gale M.; Graham, Jesse

    2017-01-01

    The purpose of this study was to explore whether conceptual change predicted emotional and attitudinal change while learning about genetically modified foods (GMFs). Participants were 322 college students; half read a refutation text designed to shift conceptual knowledge, emotions, and attitudes, while the other half served as a control group.…

  20. Hydrodynamic Study of a Submerged Entry Nozzle with Flow Modifiers

    NASA Astrophysics Data System (ADS)

    Real-Ramirez, Cesar Augusto; Miranda-Tello, Raul; Carvajal-Mariscal, Ignacio; Sanchez-Silva, Florencio; Gonzalez-Trejo, Jesus

    2017-04-01

    The fluid flow modifier technology for continuous casting process was evaluated through numerical simulations and physical experiments in this work. In the casting of steel into the mold, the process presents liquid surface instabilities which extend along the primary cooling stage. By the use of trapezoid elements installed on the external walls of the submerged nozzle, it was observed that it is possible to obtain symmetry conditions at the top of the mold and prevent high level fluctuations. The flow modifiers have equidistant holes in the submerged surface to reduce the velocity of the liquid surface by energy and mass transfer between the generated quadrants. A flow modifier drilled with a 25 pct of the submerged surface provides stability in the mold and structural stability of the proposal is guaranteed.

  1. Hydrodynamic Study of a Submerged Entry Nozzle with Flow Modifiers

    NASA Astrophysics Data System (ADS)

    Real-Ramirez, Cesar Augusto; Miranda-Tello, Raul; Carvajal-Mariscal, Ignacio; Sanchez-Silva, Florencio; Gonzalez-Trejo, Jesus

    2016-12-01

    The fluid flow modifier technology for continuous casting process was evaluated through numerical simulations and physical experiments in this work. In the casting of steel into the mold, the process presents liquid surface instabilities which extend along the primary cooling stage. By the use of trapezoid elements installed on the external walls of the submerged nozzle, it was observed that it is possible to obtain symmetry conditions at the top of the mold and prevent high level fluctuations. The flow modifiers have equidistant holes in the submerged surface to reduce the velocity of the liquid surface by energy and mass transfer between the generated quadrants. A flow modifier drilled with a 25 pct of the submerged surface provides stability in the mold and structural stability of the proposal is guaranteed.

  2. 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.

  3. 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.

  4. 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.

  5. Suppression of Spiral Wave in Modified Orengonator Model

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Jin, Wu-Yin; Yi, Ming; Wang, Chun-Ni

    2008-08-01

    In this paper, a spatial perturbation scheme is proposed to suppress the spiral wave in the modified Orengonator model, which is used to describe the chemical reaction in the light-sensitive media. The controllable external illumination Φ is perturbed with a spatial linear function. In our numerical simulation, the scheme is investigated by imposing the external controllable illumination on the space continuously and/or intermittently. The numerical simulation results confirm that the stable rotating spiral wave still can be removed with the scheme proposed in this paper even if the controllable Φ changed vs. time and space synchronously. Then the scheme is also used to control the spiral wave and turbulence in the modified Fitzhugh Nagumo model. It is found that the scheme is effective to remove the sable rotating and meandering spiral wave but it costs long transient period and intensity of the gradient parameter to eliminate the spiral turbulence.

  6. Digital halftoning using a modified pulse-coupled neural network

    NASA Astrophysics Data System (ADS)

    Duan, Huawei; Chen, Guangxue

    2011-06-01

    We report the application of modified pulse-coupled neural network (PCNN) models as an image processing tool to improve the quality of digital halftoning. Four factors including weight matrice, internal activity computation, type of error diffusion and linking coefficient were researched and optimized in terms of the PSNR metric and visual inspection on halftoning simulations. Experimental results show that the optimized PCNN model is able to yield satisfying halftoning outputs, which has better quality than that obtained by using the traditional order dither algorithm. Moreover, because of the utilization of random function in the modified PCNN model, simulated images generated from that PCNN model eliminate the periodic visual defect that the order dither innately has and therefore can potentially get rid of moiré pattern if used for printing color image. This research, on the one hand, provides a new way to do digital halftoning, on the other hand, expands the application field of the PCNN method.

  7. 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.

  8. 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.

  9. SPASIM: A Spacecraft Simulator

    NASA Technical Reports Server (NTRS)

    Liceaga, Carlos A.

    1997-01-01

    The SPAcecraft SIMulator (SPASIM) simulates the functions and resources of a spacecraft to quickly perform conceptual design (Phase A) trade-off and sensitivity analyses and uncover any operational bottlenecks during any part of the mission. Failure modes and operational contingencies can be evaluated allowing operational planning (what-if scenarios) and optimization for a range of mission scenarios. The payloads and subsystems are simulated, using a hierarchy of graphical models, in terms of how their functions affect resources such as propellant, power, and data. Any of the inputs and outputs of the payloads and subsystems can be plotted during the simulation or stored in a file so they can be used by other programs. Most trade-off analyses, including those that compare current versus advanced technology, can be performed by changing values in the parameter menus. However, when a component is replaced by one with a different functional architecture, its graphical model can also be modified or replaced by drawing from a component library. SPASIM has been validated using several spacecraft designs that were at least at the Critical Design Review level. The user and programmer guide, including figures, is available on line as a hypertext document. This is an easy-to-use and expandable tool which is based on MATLAB(R) and SIMULINK(R). It runs on Silicon Graphics Inc. workstations and personal computers with Windows 95(TM) or NT(TM).

  10. Monte Carlo Simulation Of Emission Tomography And Other Medical Imaging Techniques.

    PubMed

    Harrison, Robert L

    2010-01-05

    An introduction to Monte Carlo simulation of emission tomography. This paper reviews the history and principles of Monte Carlo simulation, then applies these principles to emission tomography using the public domain simulation package SimSET (a Simulation System for Emission Tomography) as an example. Finally, the paper discusses how the methods are modified for X-ray computed tomography and radiotherapy simulations.

  11. Adaptive core simulation

    NASA Astrophysics Data System (ADS)

    Abdel-Khalik, Hany Samy

    numerical solutions to demanding computational models, matrix methods are often employed to produce approximately equivalent discretized computational models that may be manipulated further by computers. The discretized models are described by matrix operators that are often rank-deficient, i.e. ill-posed. We introduce a novel set of matrix algorithms, denoted by Efficient Subspace Methods (ESM), intended to approximate the action of very large, dense, and numerically rank-deficient matrix operators. We demonstrate that significant reductions in both computational and storage burdens can be attained for a typical BWR core simulator adaption problem without compromising the quality of the adaption. We demonstrate robust and high fidelity adaption utilizing a virtual core, e.g. core simulator predicted observables with the virtual core either based upon a modified version of the core simulator whose input data are to be adjusted or an entirely different core simulator. Further, one specific application of ESM is demonstrated, that is being the determination of the uncertainties of important core attributes such as core reactivity and core power distribution due to the available ENDF/B cross-sections uncertainties. The use of ESM is however not limited to adaptive core simulation techniques only, but a wide range of engineering applications may easily benefit from the introduced algorithms, e.g. machine learning and information retrieval techniques highly depends on finding low rank approximations to large scale matrices. In the appendix, we present a stand-alone paper that presents a generalized framework for ESM, including the mathematical theory behind the algorithms and several demonstrative applications that are central to many engineering arenas---(a) sensitivity analysis, (b) parameter estimation, and (c) uncertainty analysis. We choose to do so to allow other engineers, applied mathematicians, and scientists from other scientific disciplines to take direct advantage of

  12. CAPS Simulation Environment Development

    NASA Technical Reports Server (NTRS)

    Murphy, Douglas G.; Hoffman, James A.

    2005-01-01

    The final design for an effective Comet/Asteroid Protection System (CAPS) will likely come after a number of competing designs have been simulated and evaluated. Because of the large number of design parameters involved in a system capable of detecting an object, accurately determining its orbit, and diverting the impact threat, a comprehensive simulation environment will be an extremely valuable tool for the CAPS designers. A successful simulation/design tool will aid the user in identifying the critical parameters in the system and eventually allow for automatic optimization of the design once the relationships of the key parameters are understood. A CAPS configuration will consist of space-based detectors whose purpose is to scan the celestial sphere in search of objects likely to make a close approach to Earth and to determine with the greatest possible accuracy the orbits of those objects. Other components of a CAPS configuration may include systems for modifying the orbits of approaching objects, either for the purpose of preventing a collision or for positioning the object into an orbit where it can be studied or used as a mineral resource. The Synergistic Engineering Environment (SEE) is a space-systems design, evaluation, and visualization software tool being leveraged to simulate these aspects of the CAPS study. The long-term goal of the SEE is to provide capabilities to allow the user to build and compare various CAPS designs by running end-to-end simulations that encompass the scanning phase, the orbit determination phase, and the orbit modification phase of a given scenario. Herein, a brief description of the expected simulation phases is provided, the current status and available features of the SEE software system is reported, and examples are shown of how the system is used to build and evaluate a CAPS detection design. Conclusions and the roadmap for future development of the SEE are also presented.

  13. The Plasma Assisted Modified Betatron.

    DTIC Science & Technology

    1984-12-27

    instability. This is a particular concern because it is now established that two other similar devices, HIPAC 16 and SPAC 1117 were disrupted by the ion... HIPAC or SPAC II. In the modified betatron, even if parameters are right for it, there is still a good chance that it will be stabilized by the

  14. 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.

  15. 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.

  16. 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…

  17. Modified Activated Carbon Perchlorate Sorbents

    DTIC Science & Technology

    2007-01-25

    and Accomplishments .................................................................................................. 13 Synthesis of Modified...The most promising technology for perchlorate remediation is bioremediation by perchlorate reducing bacteria to destroy perchlorate under...perchlorate reducing bacteria . This is a “SEED-like” proposal aimed specifically at synthesizing GMACs and determining their suitability as perchlorate

  18. 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.)

  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. Simulated Experiments

    ERIC Educational Resources Information Center

    Snadden, R. B.; Runquist, O.

    1975-01-01

    Presents an experiment in which a programmable calculator is employed as a data generating system for simulated laboratory experiments. The example used as an illustration is a simulated conductimetric titration of an aqueous solution of HC1 with an aqueous solution of NaOH. (Author/EB)

  1. 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,…

  2. 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,…

  3. Conflicting Ideologies: Simulating Significant Historical Human Decision Processes.

    ERIC Educational Resources Information Center

    Gerson, Charles W.

    1998-01-01

    A formative small-group (n12) evaluation of a pair of opposed computer simulations modeling the thinking of historical ideologies (communist insurgency and counter-insurgency) suggests simulations had value in stimulating and modifying assessments of roles within real-world settings. Explores basic objective of having the simulation user develop a…

  4. A modified relativistic magnetron with TEM output mode

    NASA Astrophysics Data System (ADS)

    Shi, Di-Fu; Qian, Bao-Liang; Wang, Hong-Gang; Li, Wei; Ju, Jin-Chuan; Du, Guang-Xing

    2017-01-01

    A modified relativistic magnetron (RM) with TEM output mode is proposed. By setting the coupling slots at the bottom of the resonant cavities in the transmission region rather than in the interaction region, besides possessing the original RM's advantages of high power conversion efficiency and radiating the lowest order mode, the modified RM not only improves the compactness and miniaturization of the magnetic field system, which is beneficial to realize the RMs packed by a permanent magnet, but also improves the robustness of operating frequency to structural perturbations of the coupling slots, which contributes to optimize the RM performance by adjusting the coupling slot dimensions with a relatively stable operating frequency. In the three-dimensional particle-in-cell (PIC) simulation, the modified RM with a reduction of 27.2% in the weight of the coils, 35.8% in the occupied space of the coils, and 18.6% in the operating current, can output a relatively pure TEM mode, which has been demonstrated as the dominant output mode by simulation, corresponding to an output power of 495.0 MW and a power conversion efficiency of 56.4%, at the resonant frequency of 4.30 GHz. In addition, an output power of above 2 GW can also be obtained from the RM in simulations.

  5. 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.

  6. JASMINE simulator

    NASA Astrophysics Data System (ADS)

    Yamada, Y.; Gouda, N.; Yano, T.; Sako, N.; Hatsutori, Y.; Tanaka, T.; Yamauchi, M.

    We explain simulation tools in JASMINE project(JASMINE simulator). The JASMINE project stands at the stage where its basic design will be determined in a few years. Then it is very important to simulate the data stream generated by astrometric fields at JASMINE in order to support investigations of error budgets, sampling strategy, data compression, data analysis, scientific performances, etc. Of course, component simulations are needed, but total simulations which include all components from observation target to satellite system are also very important. We find that new software technologies, such as Object Oriented(OO) methodologies are ideal tools for the simulation system of JASMINE(the JASMINE simulator). The simulation system should include all objects in JASMINE such as observation techniques, models of instruments and bus design, orbit, data transfer, data analysis etc. in order to resolve all issues which can be expected beforehand and make it easy to cope with some unexpected problems which might occur during the mission of JASMINE. So, the JASMINE Simulator is designed as handling events such as photons from astronomical objects, control signals for devices, disturbances for satellite attitude, by instruments such as mirrors and detectors, successively. The simulator is also applied to the technical demonstration "Nano-JASMINE". The accuracy of ordinary sensor is not enough for initial phase attitude control. Mission instruments may be a good sensor for this purpose. The problem of attitude control in initial phase is a good example of this software because the problem is closely related to both mission instruments and satellite bus systems.

  7. Direct calculation of (1)H(2)O T(1) NMRD profiles and EPR lineshapes for the electron spin quantum numbers S = 1, 3/2, 2, 5/2, 3, 7/2, based on the stochastic Liouville equation combined with Brownian dynamics simulation.

    PubMed

    Aman, Ken; Westlund, Per-Olof

    2007-02-14

    Direct calculation of electron spin relaxation and EPR lineshapes, based on Brownian dynamics simulation techniques and the stochastic Liouville equation approach (SLE-L) [Mol. Phys., 2004, 102, 1085-1093], is here generalized to high spin systems with spin quantum number S = 3/2, 2, 5/2, 3 and 7/2. A direct calculation method is demonstrated for electron spin-spin and spin-lattice relaxation, S-, X- and Q-band EPR-lineshapes and paramagnetic enhanced water proton T(1)- NMRD profiles. The main relaxation mechanism for the electron spin system is a stochastic second rank zero field splitting (ZFS). Brownian dynamics simulation techniques are used in describing a fluctuating ZFS interaction which comprises two parts namely the "permanent" part which is modulated by isotropic reorientation diffusion, and the transient part which is modulated by fast local distortion, which is also modelled by the isotropic rotation diffusion model. The SLE-L approach present is applicable both in the perturbation (Redfield) regime as well as outside the perturbation regime, in the so called slow motion regime.

  8. Multilane simulations of traffic phases.

    PubMed

    Davis, L C

    2004-01-01

    The optimal velocity model, as modified by the author, is used in simulations of traffic on a dual-lane highway and a single-lane highway with an on-ramp. The equilibrium solutions of the modified model cover a two-dimensional region of flow-density space beneath the fundamental-diagram curve, rather than just lying on the curve as in the original model. Thus it satisfies a requirement of the three-phase model of Kerner [Phys. Rev. Lett. 81, 3797 (2002)]. Synchronization of velocity across dual lanes due to frequent lane changes is observed in free flow. True synchronized flow, as determined by the region of density-flow space it occupies, is obtained in on-ramp simulations with typical driver reaction times. A gradual change to the formation of a jam is observed for increasing delay times.

  9. 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.

  10. Piloted Aircraft Environment Simulation Techniques

    DTIC Science & Technology

    1978-04-01

    safety program has since been modified to provide protection even under manual control which should prevent any further crashes except for those caused by...two functions. It will obviously serve as a road map for achieving the objective, but perhaps more importantly, it will assist in articulating the need...representing the approach and landing task on a ground based simulator, valuable returns in terms of training costs and safety are potentially

  11. Nanoparticles Modified ITO Based Biosensor

    NASA Astrophysics Data System (ADS)

    Khan, M. Z. H.

    2017-04-01

    Incorporation of nanomaterials with controlled molecular architecture shows great promise in improving electronic communication between biomolecules and the electrode substrate. In electrochemical applications metal nanoparticles (NPs) modified electrodes have been widely used and are emerging as candidates to develop highly sensitive electrochemical sensors. There has been a growing technological interest in modified indium tin oxide (ITO) electrodes due to their prominent optoelectronic properties and their wide use as a transducing platform. The introduction of NPs into the transducing platform is commonly achieved by their adsorption onto conventional electrode surfaces in various forms, including that of a composite. The aim of this review is to discuss the role of metallic NPs for surface fabrication of ITO thin films leading to detection of specific biomolecules and applications as a biosensor platform.

  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. Nanoparticles Modified ITO Based Biosensor

    NASA Astrophysics Data System (ADS)

    Khan, M. Z. H.

    2016-12-01

    Incorporation of nanomaterials with controlled molecular architecture shows great promise in improving electronic communication between biomolecules and the electrode substrate. In electrochemical applications metal nanoparticles (NPs) modified electrodes have been widely used and are emerging as candidates to develop highly sensitive electrochemical sensors. There has been a growing technological interest in modified indium tin oxide (ITO) electrodes due to their prominent optoelectronic properties and their wide use as a transducing platform. The introduction of NPs into the transducing platform is commonly achieved by their adsorption onto conventional electrode surfaces in various forms, including that of a composite. The aim of this review is to discuss the role of metallic NPs for surface fabrication of ITO thin films leading to detection of specific biomolecules and applications as a biosensor platform.

  14. The Toolbox for Modified Aptamers.

    PubMed

    Lapa, Sergey A; Chudinov, Alexander V; Timofeev, Edward N

    2016-02-01

    Aptamers are nucleic acid-based scaffolds that can bind with high affinity to a variety of biological targets. Aptamers are identified from large DNA or RNA libraries through a process of directed molecular evolution (SELEX). Chemical modification of nucleic acids considerably increases the functional and structural diversity of aptamer libraries and substantially increases the affinity of the aptamers. Additionally, modified aptamers exhibit much greater resistance to biodegradation. The evolutionary selection of modified aptamers is conditioned by the possibility of the enzymatic synthesis and replication of non-natural nucleic acids. Wild-type or mutant polymerases and their non-natural nucleotide substrates that can support SELEX are highlighted in the present review. A focus is made on the efforts to find the most suitable type of nucleotide modifications and the engineering of new polymerases. Post-SELEX modification as a complementary method will be briefly considered as well.

  15. Generalized gravity from modified DFT

    NASA Astrophysics Data System (ADS)

    Sakatani, Yuho; Uehara, Shozo; Yoshida, Kentaroh

    2017-04-01

    Recently, generalized equations of type IIB supergravity have been derived from the requirement of classical kappa-symmetry of type IIB superstring theory in the Green-Schwarz formulation. These equations are covariant under generalized T -duality transformations and hence one may expect a formulation similar to double field theory (DFT). In this paper, we consider a modification of the DFT equations of motion by relaxing a condition for the generalized covariant derivative with an extra generalized vector. In this modified double field theory (mDFT), we show that the flatness condition of the modified generalized Ricci tensor leads to the NS-NS part of the generalized equations of type IIB supergravity. In particular, the extra vector fields appearing in the generalized equations correspond to the extra generalized vector in mDFT. We also discuss duality symmetries and a modification of the string charge in mDFT.

  16. Evaluation of Asphalt Binder Modifiers

    DTIC Science & Technology

    1990-01-01

    or SBS rubber described as an oil-extended polymer produced in pellet form. This type of rubber is available in other solid forms such as crumb or...is done to improve the performance characteristics of future pavements. Many research programs have been conducted on asphalt modifiers. Most of...tests were conducted during the second year of the study and resultant data were used to choose five materials to meet the test objectives of this

  17. Estimating the Modified Allan Variance

    NASA Technical Reports Server (NTRS)

    Greenhall, Charles

    1995-01-01

    The third-difference approach to modified Allan variance (MVAR) leads to a tractable formula for a measure of MVAR estimator confidence, the equivalent degrees of freedom (edf), in the presence of power-law phase noise. The effect of estimation stride on edf is tabulated. A simple approximation for edf is given, and its errors are tabulated. A theorem allowing conservative estimates of edf in the presence of compound noise processes is given.

  18. Analysis of genetically modified oils.

    PubMed

    Hazebroek, J P

    2000-11-01

    Genetically modified oils with altered functional or nutritional characteristics are being introduced into the marketplace. A wide array of analytical techniques has been utilized to facilitate developing these oils. This article attempts to review the utilization of these analytical procedures for characterizing both the chemistry and some functionality of these oils. Although techniques to assess oxidative stability in frying and food applications are covered, measurement of nutritional characteristics are not.

  19. Comment on Modified Stokes Parameters

    NASA Technical Reports Server (NTRS)

    Le Vine, D.M.; Utku, C.

    2009-01-01

    It is common practice in passive microwave remote sensing (microwave radiometry) to express observables as temperatures and in the case of polarimetric radiometry to use what are called "Modified Stokes Parameters in Brightness Temperature" to describe the scene. However, definitions with slightly different normalization (with and without division by bandwidth) have appeared in the literature. The purpose of this manuscript is to present an analysis to clarify the meaning of terms in the definition and resolve the question of the proper normalization.

  20. Genetic Modifiers of Ovarian Cancer

    DTIC Science & Technology

    2012-06-01

    association study ( GWAS ) for ovarian cancer in BRCA1 mutation carriers was initiated in an effort to identify common genetic variants that modify... GWAS of 1250 BRCA1 mutation carriers diagnosed with breast cancer and 1250 unaffected BRCA1 carriers using Human660W-Quad arrays. The 1250 unaffected...cancer on H uman660W-Quad arrays. In addition we acquired GWAS genotype data for 120 additional BRCA1 mutation carriers affected with ovarian

  1. Genetic Modifiers of Ovarian Cancer

    DTIC Science & Technology

    2013-06-01

    cancer suggesting the presence of genetic modifiers of ovarian cancer in this population. A genome wide association study ( GWAS ) for ovarian cancer...cancer and 1,000 age-matched unaffected BRCA1 carriers. As outlined in detail in our previous annual report, we recently conducted a GWAS of BRCA1...between ovarian cancer risk and SNPs implicated in Aim 1 by genotyping 1,500 BRCA1 ovarian cancer cases and 1,500 unaffected BRCA1 carriers. GWAS

  2. 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.

  3. Wind Simulation

    SciTech Connect

    Walker, Howard Andrew

    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.

  4. Mission Simulators

    NASA Image and Video Library

    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...

  5. Dissipative dynamics at conical intersections: simulations with the hierarchy equations of motion method.

    PubMed

    Chen, Lipeng; Gelin, Maxim F; Chernyak, Vladimir Y; Domcke, Wolfgang; Zhao, Yang

    2016-12-16

    The effect of a dissipative environment on the ultrafast nonadiabatic dynamics at conical intersections is analyzed for a two-state two-mode model chosen to represent the S2(ππ*)-S1(nπ*) conical intersection in pyrazine (the system) which is bilinearly coupled to infinitely many harmonic oscillators in thermal equilibrium (the bath). The system-bath coupling is modeled by the Drude spectral function. The equation of motion for the reduced density matrix of the system is solved numerically exactly with the hierarchy equation of motion method using graphics-processor-unit (GPU) technology. The simulations are valid for arbitrary strength of the system-bath coupling and arbitrary bath memory relaxation time. The present computational studies overcome the limitations of weak system-bath coupling and short memory relaxation time inherent in previous simulations based on multi-level Redfield theory [A. Kühl and W. Domcke, J. Chem. Phys. 2002, 116, 263]. Time evolutions of electronic state populations and time-dependent reduced probability densities of the coupling and tuning modes of the conical intersection have been obtained. It is found that even weak coupling to the bath effectively suppresses the irregular fluctuations of the electronic populations of the isolated two-mode conical intersection. While the population of the upper adiabatic electronic state (S2) is very efficiently quenched by the system-bath coupling, the population of the diabatic ππ* electronic state exhibits long-lived oscillations driven by coherent motion of the tuning mode. Counterintuitively, the coupling to the bath can lead to an enhanced lifetime of the coherence of the tuning mode as a result of effective damping of the highly excited coupling mode, which reduces the strong mode-mode coupling inherent to the conical intersection. The present results extend previous studies of the dissipative dynamics at conical intersections to the nonperturbative regime of system-bath coupling. They

  6. 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.

  7. Dark Energy simulations

    NASA Astrophysics Data System (ADS)

    Baldi, Marco

    2012-11-01

    Cosmology is presently facing the deep mystery of the origin of the observed accelerated expansion of the Universe. Be it a cosmological constant, a homogeneous scalar field, or a more complex inhomogeneous field possibly inducing effective modifications of the laws of gravity, such elusive physical entity is indicated with the general term of “Dark Energy”. The growing role played by numerical N-body simulations in cosmological studies as a fundamental connection between theoretical modeling and direct observations has led to impressive advancements also in the development and application of specific algorithms designed to probe a wide range of Dark Energy scenarios. Over the last decade, a large number of independent and complementary investigations have been carried out in the field of Dark Energy N-body simulations, starting from the simplest case of homogeneous Dark Energy models up to the recent development of highly sophisticated iterative solvers for a variety of Modified Gravity theories. In this review -which is meant to be complementary to the general Review by Kuhlen et al. (2012) [1] published in this Volume - I will discuss the range of scenarios for the cosmic acceleration that have been successfully investigated by means of dedicated N-body simulations, and I will provide a broad summary of the main results that have been obtained in this rather new research field. I will focus the discussion on a few selected studies that have led to particularly significant advancements in the field, and I will provide a comprehensive list of references for a larger number of related works. Due to the vastness of the topic, the discussion will not enter into the finest details of the different implementations and will mainly focus on the outcomes of the various simulations studies. Although quite recent, the field of Dark Energy simulations has witnessed huge developments in the last few years, and presently stands as a reliable approach to the investigation

  8. Multispectral Imaging Simulation

    NASA Astrophysics Data System (ADS)

    Loefer, Gene R.; Lao, Ken Q.

    1987-09-01

    Current aircraft have a requirement to operate at night and in adverse weather where optical imaging systems are inoperable. Imaging sensors operating at other wavelengths have the potential to provide vision through severe weather, but these systems need to be simulated before assuming the technological and financial risks involved in hardware development. Sensor and atmospheric models have been developed which simulate images at a variety of wavelengths. These models have been incorporated into a modified version of the IVEX Corporation Behold software which is used for the creation of three dimensional views of terrain data bases and includes fractal texturing and anti-aliasing. This new version, called Behold-ms, adds phenomenological models of material properties, such as surface roughness, emissivity, and temperature, and structured atmospheric weather models that consider path emission, backscatter, and specular/diffuse reflections of the sky. To date, images have been simulated in the visible (color), infrared (8-14pm), passive millimeter wave (35 GHz and 95 GHz), and active MMW (35 GHz and 95 GHz). These algorithms can be used for other windows over this spectral range. In order to accommodate the widely varying types of sensed energy while maintaining a practical amount of internal storage, a scheme for scaling each spectral band has been developed. Spatial resolution degradation due to diffraction, which is especially important at millimeter wavelengths, spatial sampling effects, and system noise models are also included. These sensor models and simulations have been used to examine adverse weather landing systems. Simulated images have also been used in image understanding research and spatial superresolution studies.

  9. Simulation Methodology

    DTIC Science & Technology

    1991-05-01

    to estimate the original probability of the rare event one needs to compensate for the change of measure and this involves using likelihood rations...Glynn Ward Whitt 48 12/89 A New View of the Heavy-Traffic Limit Theorem Peter W. Glynn for Many-Server Queues Ward Whitt 49 12/89 The Covariance...Validity of Sequential Stopping Rules Peter W. Glynn for Stochastic Simulations Ward Whitt 56 02/90 Analysis of Parallel, Replicated Simulations

  10. Combustor Simulation

    NASA Technical Reports Server (NTRS)

    Norris, Andrew

    2003-01-01

    The goal was to perform 3D simulation of GE90 combustor, as part of full turbofan engine simulation. Requirements of high fidelity as well as fast turn-around time require massively parallel code. National Combustion Code (NCC) was chosen for this task as supports up to 999 processors and includes state-of-the-art combustion models. Also required is ability to take inlet conditions from compressor code and give exit conditions to turbine code.

  11. 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.

  12. Identifying modifier loci in existing genome scan data.

    PubMed

    Daw, E W; Lu, Y; Marian, A J; Shete, S

    2008-09-01

    In many genetic disorders in which a primary disease-causing locus has been identified, evidence exists for additional trait variation due to genetic factors. These findings have led to studies seeking secondary 'modifier' loci. Identification of modifier loci provides insight into disease mechanisms and may provide additional screening and treatment targets. We believe that modifier loci can be identified by re-analysis of genome screen data while controlling for primary locus effects. To test this hypothesis, we simulated multiple replicates of typical genome screening data on to two real family structures from a study of hypertrophic cardiomyopathy. With this marker data, we simulated two trait models with characteristics similar to one measure of hypertrophic cardiomyopathy. Both trait models included 3 genes. In the first, the trait was influenced by a primary gene, a secondary 'modifier' gene, and a third very small effect gene. In the second, we modeled an interaction between the first two genes. We examined power and false positive rates to map the secondary locus while controlling for the effect of the primary locus with two types of analyses. First, we examined Monte Carlo Markov chain (MCMC) simultaneous segregation and linkage analysis as implemented in Loki, for which we calculated two scoring statistics. Second, we calculated LOD scores using an individual-specific liability class based on the quantitative trait value. We found that both methods produced scores that are significant on a genome-wide level in some replicates. We conclude that mapping of modifier loci in existing samples is possible with these methods.

  13. Computer simulations of learning in neural systems.

    PubMed

    Salu, Y

    1983-04-01

    Recent experiments have shown that, in some cases, strengths of synaptic ties are being modified in learning. However, it is not known what the rules that control those modifications are, especially what determines which synapses will be modified and which will remain unchanged during a learning episode. Two postulated rules that may solve that problem are introduced. To check their effectiveness, the rules are tested in many computer models that simulate learning in neural systems. The simulations demonstrate that, theoretically, the two postulated rules are effective in organizing the synaptic changes. If they are found to also exist in biological systems, these postulated rules may be an important element in the learning process.

  14. A study of a proposed modified torsional agility metric

    NASA Technical Reports Server (NTRS)

    Valasek, John; Eggold, David P.; Downing, David R.

    1991-01-01

    A new candidate lateral agility metric, the modified torsional agility parameter, is proposed and tested through generic, nonlinear, non-real-time flight simulation programs of the F-18 and F-5A. The metric is aimed at quantifying high subsonic loaded roll capabilities which might be useful in modern air combat. The metric is considered to be straightforward for testing and measuring based on nonreal-time unmanned flight simulation. The metric is found to be sensitive to pilot input errors of less than full lateral stick to capture bank angle, when tested using unmanned flight simulations. It is suggested that, for redesigned configurations of both aircraft with improved lateral agility, the major benefit would be provided by fast and highly effective rudders, and a high level of pitch, roll, and yaw damping at moderate to high normal load factor levels.

  15. 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.…

  16. 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.…

  17. Reversible simulation of irreversible computation

    NASA Astrophysics Data System (ADS)

    Li, Ming; Tromp, John; Vitányi, Paul

    1998-09-01

    Computer computations are generally irreversible while the laws of physics are reversible. This mismatch is penalized by among other things generating excess thermic entropy in the computation. Computing performance has improved to the extent that efficiency degrades unless all algorithms are executed reversibly, for example by a universal reversible simulation of irreversible computations. All known reversible simulations are either space hungry or time hungry. The leanest method was proposed by Bennett and can be analyzed using a simple ‘reversible’ pebble game. The reachable reversible simulation instantaneous descriptions (pebble configurations) of such pebble games are characterized completely. As a corollary we obtain the reversible simulation by Bennett and, moreover, show that it is a space-optimal pebble game. We also introduce irreversible steps and give a theorem on the tradeoff between the number of allowed irreversible steps and the memory gain in the pebble game. In this resource-bounded setting the limited erasing needs to be performed at precise instants during the simulation. The reversible simulation can be modified so that it is applicable also when the simulated computation time is unknown.

  18. Simulating Voids

    NASA Astrophysics Data System (ADS)

    Goldberg, David M.; Vogeley, Michael S.

    2004-04-01

    We present a novel method for the simulation of the interior of large cosmic voids, suitable for the study of the formation and evolution of objects lying within such regions. Following Birkhoff's theorem, void regions dynamically evolve as universes with cosmological parameters that depend on the underdensity of the void. We derive the values of ΩM, ΩΛ, and H0 that describe this evolution. We examine how the growth rate of structure and scale factor in a void differ from the background universe. Together with a prescription for the power spectrum of fluctuations, these equations provide the initial conditions for running specialized void simulations. The increased efficiency of such simulations, in comparison to general-purpose simulations, allows an improvement of upward of 20 in the mass resolution. As a sanity check, we run a moderate-resolution simulation (N=1283 particles) and confirm that the resulting mass function of void halos is consistent with other theoretical and numerical models.

  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. 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

  1. 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.

  2. 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.

  3. 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.

  4. Dark matter in modified gravity?

    NASA Astrophysics Data System (ADS)

    Katsuragawa, Taishi; Matsuzaki, Shinya

    2017-02-01

    We explore a new horizon of modified gravity from the viewpoint of particle physics. As a concrete example, we take the F (R ) gravity to raise a question: can a scalar particle ("scalaron") derived from the F (R ) gravity be a dark matter candidate? We place the limit on the parameter in a class of F (R ) gravity model from the constraint on the scalaron as a dark matter. The role of the screening mechanism and compatibility with the dark energy problem are addressed.

  5. 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.

  6. 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.

  7. 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

  8. Estimating the Modified Allan Variance

    NASA Technical Reports Server (NTRS)

    Greenhall, Charles

    1995-01-01

    A paper at the 1992 FCS showed how to express the modified Allan variance (mvar) in terms of the third difference of the cumulative sum of time residuals. Although this reformulated definition was presented merely as a computational trick for simplifying the calculation of mvar estimates, it has since turned out to be a powerful theoretical tool for deriving the statistical quality of those estimates in terms of their equivalent degrees of freedom (edf), defined for an estimator V by edf V = 2(EV)2/(var V). Confidence intervals for mvar can then be constructed from levels of the appropriate 2 distribution.

  9. 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.

  10. 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).

  11. 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.

  12. 77 FR 58592 - Modified Norway Post Agreement

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-21

    ... Modified Norway Post Agreement AGENCY: Postal Regulatory Commission. ACTION: Notice. SUMMARY: The Commission is noticing a recently-filed Postal Service request to include a modified Norway Post Agreement... existing bilateral agreement for inbound competitive services with Posten Norge AS (Modified Norway...

  13. 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…

  14. 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.

  15. Fabrication and characterization of modified-hydroxyapatite/polyetheretherketone coating materials

    NASA Astrophysics Data System (ADS)

    Ma, Rui; Fang, Lin; Luo, Zhongkuan; Zheng, Ruisheng; Song, Shenhua; Weng, Luqian; Lei, JinPing

    2014-09-01

    45 wt%-Hydroxyaptite/polyetheretherketone (HA/PEEK) coating materials modified by silane coupling agent (KH560) on PEEK substrate were successfully fabricated by solution casting method and characterized by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), scanning electron microscopy (SEM), and tensile testing. The modified HA fillers were obtained to be uniformly distributed in the HA/PEEK coating, which has better properties of tensile strength and fracture toughness than those of the unmodified specimen. A good bonding between the composite coating and the PEEK substrate was achieved by solution casting method, resulting in integral-fracture without falling apart or delaminating during tensile loading. The modified specimens dipped into simulated body fluid (SBF) were characterized by SEM, XRD and FTIR, indicating that the bioactivity of the dipped materials was demonstrated more apparent with extending the dipping time. Therefore, the coating materials may become the substitutes for the hard tissues of the human body in the future, which could realize the balance between the mechanical properties and the bioactivity by modifying the structural design of the coating.

  16. 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.

  17. Modified fractal model and rheological properties of colloidal networks.

    PubMed

    Tang, Dongming; Marangoni, Alejandro G

    2008-02-15

    The scaling relationship between the storage modulus (G(')) and the volume fraction of solids (Phi) in fat crystal networks has been explained by the fractal model developed by our group. However, many experimental results and simulation studies suggest that the stress distribution within a colloidal network is dramatically heterogeneous, which means that a small part of the network carries most of the stress, while the other part of the network does not contribute much to the elastic properties of the system. This concept was introduced into a modified fractal model. The volume fraction of solids term (Phi) in the original fractal model was replaced by Phi(e), the effective volume fraction of solids, in the modified fractal model, which represents the volume fraction of stress-carrying solids. A proposed expression for Phi(e) is given and a modified expression for the scaling relationship between G(') and Phi is obtained. The modified fractal model fits the experiment data well and successfully explains the sometimes observed nonlinear log-log behavior between the storage modulus of colloidal networks and their volume fraction of solids.

  18. Wind tunnel simulations of aerolian processes

    NASA Technical Reports Server (NTRS)

    Greeley, R.

    1984-01-01

    The characteristics of aerolian (wind) activity as a surface modifying process on Earth, Mars, Venus, and appropriate satellites was determined. A combination of spacecraft data analysis, wind tunnel simulations, and terrestrial field analog studies were used to determine these characteristics. Wind tunnel experiments simulating Venusian surface conditions demonstrate that rolling of particles may be an important mode of transport by winds on Venus and that aerolian processes in the dense atmosphere may share attributes of both aerolian and aqueous environments on Earth.

  19. Model Validation for Simulations of Vehicle Systems

    DTIC Science & Technology

    2012-08-01

    a large number of replicate samples via Monte- Carlo simulation. The test data, on the other hand, is usually provided as a collection of point...can be determined by Monte Carlo simulation. Classical hypothesis testing techniques depend on a normality assumption except for the modified...criteria”, Computer Methods in Applied Mechanics and Engineering, 197:2517-2539, 2008. [14] S. Ferson, W. L. Oberkampf and L. Ginzburg , “Model

  20. Modified Beamformers for Coherent Source Region Suppression

    PubMed Central

    Sekihara, Kensuke; Nagarajan, Srikantan S.

    2011-01-01

    Many tomographic source localization algorithms used in biomagnetic imaging assume, explicitly or sometimes implicitly, that the source activity at different brain locations are either independent or that the correlation structure between sources is known. Among these algorithms is a class of adaptive spatial filters known as beamformers, which have superior spatiotemporal resolution abilities. The performance of beamformers is robust to weakly coherent sources. However, these algorithms are extremely sensitive to the presence of strongly coherent sources. A frequent mode of failure in beamformers occurs with reconstruction of auditory evoked fields (AEFs), in which bilateral auditory cortices are highly coherent in their activation. Here, we present a novel beamformer that suppresses activation from regions with interfering coherent sources. First, a volume containing the interfering sources is defined. The lead field matrix for this volume is computed and reduced into a few significant columns using singular value decomposition (SVD). A vector beamformer is then constructed by rejecting the contribution of sources in the suppression region while allowing for source reconstruction at other specified regions. Performance of this algorithm was first validated with simulated data. Subsequent tests of this modified beamformer were performed on bilateral AEF data. An unmodified vector beamformer using whole head coverage misplaces the source medially. After defining a suppression region containing the temporal cortex on one side, the described method consistently results in clear focal activations at expected regions of the contralateral superior temporal plane. PMID:16830939

  1. Modified sparse regularization for electrical impedance tomography

    SciTech Connect

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

    2016-03-15

    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 L{sub 1} 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.

  2. 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.

  3. Implications of Simulation Conceptual Model Development for Simulation Management and Uncertainty Assessment

    NASA Technical Reports Server (NTRS)

    Pace, Dale K.

    2000-01-01

    A simulation conceptual model is a simulation developers way of translating modeling requirements (i. e., what is to be represented by the simulation or its modification) into a detailed design framework (i. e., how it is to be done), from which the software, hardware, networks (in the case of distributed simulation), and systems/equipment that will make up the simulation can be built or modified. A conceptual model is the collection of information which describes a simulation developers concept about the simulation and its pieces. That information consists of assumptions, algorithms, characteristics, relationships, and data. Taken together, these describe how the simulation developer understands what is to be represented by the simulation (entities, actions, tasks, processes, interactions, etc.) and how that representation will satisfy the requirements to which the simulation responds. Thus the conceptual model is the basis for judgment about simulation fidelity and validity for any condition that is not specifically tested. The more perspicuous and precise the conceptual model, the more likely it is that the simulation development will both fully satisfy requirements and allow demonstration that the requirements are satisfied (i. e., validation). Methods used in simulation conceptual model development have significant implications for simulation management and for assessment of simulation uncertainty. This paper suggests how to develop and document a simulation conceptual model so that the simulation fidelity and validity can be most effectively determined. These ideas for conceptual model development apply to all simulation varieties. The paper relates these ideas to uncertainty assessments as they relate to simulation fidelity and validity. The paper also explores implications for simulation management from conceptual model development methods, especially relative to reuse of simulation components.

  4. Implications of Simulation Conceptual Model Development for Simulation Management and Uncertainty Assessment

    NASA Technical Reports Server (NTRS)

    Pace, Dale K.

    2000-01-01

    A simulation conceptual model is a simulation developers way of translating modeling requirements (i. e., what is to be represented by the simulation or its modification) into a detailed design framework (i. e., how it is to be done), from which the software, hardware, networks (in the case of distributed simulation), and systems/equipment that will make up the simulation can be built or modified. A conceptual model is the collection of information which describes a simulation developers concept about the simulation and its pieces. That information consists of assumptions, algorithms, characteristics, relationships, and data. Taken together, these describe how the simulation developer understands what is to be represented by the simulation (entities, actions, tasks, processes, interactions, etc.) and how that representation will satisfy the requirements to which the simulation responds. Thus the conceptual model is the basis for judgment about simulation fidelity and validity for any condition that is not specifically tested. The more perspicuous and precise the conceptual model, the more likely it is that the simulation development will both fully satisfy requirements and allow demonstration that the requirements are satisfied (i. e., validation). Methods used in simulation conceptual model development have significant implications for simulation management and for assessment of simulation uncertainty. This paper suggests how to develop and document a simulation conceptual model so that the simulation fidelity and validity can be most effectively determined. These ideas for conceptual model development apply to all simulation varieties. The paper relates these ideas to uncertainty assessments as they relate to simulation fidelity and validity. The paper also explores implications for simulation management from conceptual model development methods, especially relative to reuse of simulation components.

  5. Modified Synthesis of Erlotinib Hydrochloride

    PubMed Central

    Barghi, Leila; Aghanejad, Ayuob; Valizadeh, Hadi; Barar, Jaleh; Asgari, Davoud

    2012-01-01

    Purpose: An improved and economical method has been described for the synthesis of erlotinib hydrochloride, as a useful drug in treatment of non-small-cell lung cancer. Method: Erlotinib hydrochloride was synthesized in seven steps starting from 3, 4-dihydroxy benzoic acid. In this study, we were able to modify one of the key steps which involved the reduction of the 6-nitrobenzoic acid derivative to 6-aminobenzoic acid derivative. An inexpensive reagent such as ammonium formate was used as an in situ hydrogen donor in the presence of palladium/charcoal (Pd/C) instead of hydrogen gas at high pressure. Result: This proposed method proceeded with 92% yield at room temperature. Synthesis of erlotinib was completed in 7 steps with overall yield of 44%. Conclusion: From the results obtained it can be concluded that the modified method eliminated the potential danger associated with the use of hydrogen gas in the presence of flammable catalysts. It should be mentioned that the catalyst was recovered after the reaction and could be used again. PMID:24312780

  6. 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.

  7. A modified fluid percussion device.

    PubMed

    Yamaki, T; Murakami, N; Iwamoto, Y; Yoshino, E; Nakagawa, Y; Ueda, S; Horikawa, J; Tsujii, T

    1994-10-01

    This report examines a modified fluid percussion device with specific improvements made to address deficiencies found in previously reported devices. These improvements include the use of a cylindrical saline reservoir made of stainless steel, placement of the reservoir in a 15-degree head-up position for the easy release of air bubbles, placement of the fluid flushing outlet and the pressure transducer close to the piston on the same plane, with both perpendicular to the direction of the piston, and adjustable reservoir volume to vary the waveform of the pressure pulse, and a metallic central injury screw secured to the animal's skull over the exposed dura. Using this device, midline fluid percussion (MFP) and lateral fluid percussion (LFP) injuries were performed in 70 rats. Histopathologic findings included diffuse axonal injury in the MFP model and cortical contusion in the LFP model. Survival rate was 41.4% in MFP animals and 100% in LFM animals when the device settings were 178 mm3 of the cylindrical reservoir and 50 degrees-60 degrees in height of the pendulum. Our results suggest that this modified fluid percussion device may offer significant improvements over previously reported fluid percussion models for use in experimental head injury.

  8. 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.

  9. PIC simulations of asymmetric reconnection

    NASA Astrophysics Data System (ADS)

    Malakit, K.; Shay, M. A.; Cassak, P.

    2009-12-01

    Conventional studies of magnetic reconnection have almost exclusively focussed on symmetric systems, i.e., where both upstream regions have the same magnetic field magnitude and particle density. However, in many physics systems such as the dayside magnetosphere, reconnection is often asymmetric with different upstream conditions on either side. In this study we perform full particle simulations of anti-parallel asymmetric reconnection with a range of different upstream values. The results are consistent with previous Sweet-Parker scaling results and fluid simulations (e.g. Cassak and Shay, 2007,2008), suggesting that kinetic physics does not fundamentally modify the gross properties of the diffusion region. Contrary to fluid simulation studies which did not allow parallel diffusion along magnetic field lines, the downstream density is consistent with previous scaling predictions that assume complete mixing along field lines within the diffusion region.

  10. A new cardiac auscultation simulator.

    PubMed

    Takashina, T; Masuzawa, T; Fukui, Y

    1990-12-01

    We have successfully developed a new cardiac auscultation simulator by applying recently developed digital and computer technology, which digitally records, stores, modifies, and plays back heart sounds and murmurs characteristic of various heart diseases. The simulator is capable of playing back different heart sounds or murmurs at each auscultatory site (aortic, pulmonic, tricuspid, and mitral) of a human chest-sized mannequin (made of urethane foam), through four built-in speakers. We were able to listen to accurate reproductions of heart sounds and murmurs at the same timing as in real patients by any type of stethoscope used in routine medical practice. This compact and portable educational apparatus, which simulates realistic auscultatory sounds, will impact greatly on the medical training of cardiac auscultation for physicians, medical students, nurses, and paramedicals.

  11. Molecular dynamics simulation of benzene

    NASA Astrophysics Data System (ADS)

    Trumpakaj, Zygmunt; Linde, Bogumił B. J.

    2016-03-01

    Intermolecular potentials and a few models of intermolecular interaction in liquid benzene are tested by Molecular Dynamics (MD) simulations. The repulsive part of the Lennard-Jones 12-6 (LJ 12-6) potential is too hard, which yields incorrect results. The exp-6 potential with a too hard repulsive term is also often used. Therefore, we took an expa-6 potential with a small Gaussian correction plus electrostatic interactions. This allows to modify the curvature of the potential. The MD simulations are carried out in the temperature range 280-352 K under normal pressure and at experimental density. The Rayleigh scattering of depolarized light is used for comparison. The results of MD simulations are comparable with the experimental values.

  12. Simulated Agribusiness.

    ERIC Educational Resources Information Center

    Salisbury, Howard G., III

    "Simulated Agribusiness" is designed to provide the student with a role playing situation dealing with the complexities and problems of modern agriculture. It is a competitive game played on a hypothetical mid-latitude diversified farm in a capitalistic system. The player is faced with a series of decisions which will determine his success or…

  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 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)

  15. ERA Simulation.

    ERIC Educational Resources Information Center

    Shelly, Ann C.; Wilen, William W.

    1982-01-01

    Presents a simulation which can be used in any secondary social studies course to teach about the Equal Rights Amendment. It can be played with as few as ten and as many as 40 students. Playing time varies from three to seven class periods. (RM)

  16. 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…

  17. 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…

  18. 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)

  19. Preliminary Results of Altitude-Wind-Tunnel Investigation of X24C-4B Turbojet Engine. V - Performance of Modified Engine. V; Performance of Modified Engine

    NASA Technical Reports Server (NTRS)

    Prince, William R.; Bloomer, Harry E.

    1947-01-01

    An investigation has been conducted in the NACA Cleveland altitude wind tunnel to evaluate the performance characteristics of a modified X24C-4B turbojet engine over a range of simulated altitudes from 5000 to 45,000 feet, simulated flight Mach numbers from 0.25 to 1.07, and engine speeds from 4000 to 12,500 rpm. The engine was modified by the manufacturer to improve the velocity and temperature profiles within the engine. Performance data are graphically presented to show the effect of altitude at a flight Mach number of 0.25 and the effect of flight Mach number at an altitude of 25,000 feet. Original and modified engine performances for several specific operating conditions are compared. A complete tabulation of average pressures and temperatures throughout the engine, performance data, and lubrication and fuel-system data is presented.

  20. Enhancement of the electrical characteristics for vertical NAND flash memory devices using a modified array structure

    NASA Astrophysics Data System (ADS)

    An, Sung Woo; Kim, Tae Whan

    2017-04-01

    The electrical characteristics of vertical NAND flash memory devices with a modified structure were investigated by using a technology computer-aided design simulation tool in order to reduce the cell-to-cell interference. The threshold voltage shift of memory devices with a modified cell with a protruding distance of 3 nm was reduced by 88% compared to that of conventional cell. When the programming operation of the target cell with a modified array structure is performed, the cell-to-cell interference decreases due to the programmed charges of adjacent cells.

  1. Modified Savart polariscope with wide field of view and achromatic lateral displacement

    NASA Astrophysics Data System (ADS)

    Quan, Naicheng; Zhang, Chunmin; Mu, Tingkui

    2017-01-01

    A modified Savart polariscope with wide field of view and achromatic lateral displacement is presented. The modified Savart polariscope can be made from two different birefringent crystal materials. The principle of the element is described and the impacts of systematic errors are analyzed. The achievement and performance of the modified Savart polariscope is demonstrated with numerical simulations. The maximum acceptable angle of incidence can be increased by an order of magnitude and the chromatic variations in lateral displacement are inhibited obviously across the specified spectral range 0.4 μm to 0.9 μm.

  2. Deformability Calculation for Estimation of the Relative Stability of Chemically Modified RNA Duplexes.

    PubMed

    Masaki, Yoshiaki; Sekine, Mitsuo; Seio, Kohji

    2017-03-02

    Chemical modification of RNA duplexes alters their stability. We have attempted to develop a computational approach to estimate the thermal stability of chemically modified duplexes. These studies revealed that the deformability of chemically modified RNA duplexes, calculated from molecular dynamics simulations, could be used as a good indicator for estimating the effect of chemical modification on duplex thermal stability. This unit describes how deformability calculation can be applied to estimate the relative stability of chemically modified RNA duplexes. © 2017 by John Wiley & Sons, Inc.

  3. 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.

  4. Modified function projective combination synchronization of hyperchaotic systems

    NASA Astrophysics Data System (ADS)

    Sudheer, K. Sebastian; Sabir, M.

    2017-03-01

    In this work, a novel combination synchronization scheme in which synchronization of a new combination hyperchaotic drive system formed by combining state variables of the original drive system with appropriate scaling factors with a response hyperchaotic system is considered. A self-combination system is constructed from hyperchaotic Lorenz system by combining state variables of the Lorenz system with appropriate scaling factors. Modified function projective synchronization between the newly constructed combination hyperchaotic Lorenz system and hyperchaotic Lu system is investigated using adaptive method. By Lyapunov stability theory, the adaptive control law and the parameter update law are derived to make the state of two systems as modified function projective synchronized. Numerical simulations are done to show the validity and effectiveness of the proposed synchronization scheme.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. Simulations of Active Vortex Generators

    NASA Technical Reports Server (NTRS)

    Mansour, N. N.; Koumoutsakos, P.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    We are interested in the study, via numerical simulations, of active vortex generators. Vortex generators may be used to modify the inner part of the boundary layer or to control separation thus enhancing the performance and maneuverability of aerodynamic configurations. we consider generators that consist of a surface cavity elongated in the streamwise direction and partially covered with a moving lid that at rest lies flush with the boundary. Streamwise vorticity is generated and ejected due to the oscillatory motion of the lid. The present simulations complement relevant experimental investigations of active vortex generators that have been conducted at NASA Ames Research Center and Stanford University used a piezoelectric device in water, allowing for small amplitude high frequency oscillations. They placed the lid asymmetrically on the cavity and observed a strong outward velocity at the small gap of the cavity. Saddoughi used a larger mechanically driven device in air to investigate this flow and observed a jet emerging from the wide gap of the configuration, contrary to the findings of Jacobson and Reynolds We are simulating the flows generated by these devices and we are conducting a parametric study that would help us elucidate the physical mechanisms present in the flow. Conventional computational schemes encounter difficulties when simulating flows around complex configurations undergoing arbitrary motions. Here we present a formulation that achieves this task on a purely Lagrangian frame by extending the formulation presented by Koumoutsakos, Leonard and Pepin (1994). The viscous effects are taken into account by modifying the strength Of the particles, whereas fast multipole schemes employing hundreds of thousands of particles allow for high resolution simulations. We shall present simulation results of an oscillating plate at various Reynolds numbers and Strouhal frequencies.

  10. Simulations of Active Vortex Generators

    NASA Technical Reports Server (NTRS)

    Mansour, N. N.; Koumoutsakos, P.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    We are interested in the study, via numerical simulations, of active vortex generators. Vortex generators may be used to modify the inner part of the boundary layer or to control separation thus enhancing the performance and maneuverability of aerodynamic configurations. We consider generators that consist of a surface cavity elongated in the streamwise direction and partially covered with a moving lid that at rest lies flush with the boundary. Streamwise voracity is generated and ejected due to the oscillatory motion of the lid. The present simulations c Implement relevant experimental investigations of active vortex generators that have been conducted at NASA Ames Research Center and Stanford University. Jacobson and Reynolds used a piezoelectric device in water, allowing for small amplitude high frequency oscillations. They placed the lid asymmetrically on the cavity and observed a strong outward velocity at the small gap of the cavity. Saddoughi used a larger mechanically driven device in air to investigate this flow and observed a jet emerging from the wide gap of the configuration, contrary to the findings of Jacobson and Reynolds. More recently, Lachowiez and Wlezien are investigating the flow generated by an electro-mechanically driven lid to be used for assertion control in aerodynamic applications. We are simulating the flows generated by these devices and we are conducting a parametric study that would help us elucidate the physical mechanisms present in the flow. Conventional computational schemes encounter difficulties when simulating flows around complex configurations undergoing arbitrary motions. Here we present a formulation that achieves this task on a purely Lagrangian frame by extending the formulation presented by Koumoutsakos, Leonard and Pepin. The viscous effects are taken into account by modifying the strength of the particles, whereas fast multipole schemes employing hundreds of thousands ol'particle's allow for high resolution simulations

  11. Simulations of Active Vortex Generators

    NASA Technical Reports Server (NTRS)

    Mansour, N. N.; Koumoutsakos, P.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    We are interested in the study, via numerical simulations, of active vortex generators. Vortex generators may be used to modify the inner part of the boundary layer or to control separation thus enhancing the performance and maneuverability of aerodynamic configurations. We consider generators that consist of a surface cavity elongated in the streamwise direction and partially covered with a moving lid that at rest lies flush with the boundary. Streamwise voracity is generated and ejected due to the oscillatory motion of the lid. The present simulations c Implement relevant experimental investigations of active vortex generators that have been conducted at NASA Ames Research Center and Stanford University. Jacobson and Reynolds used a piezoelectric device in water, allowing for small amplitude high frequency oscillations. They placed the lid asymmetrically on the cavity and observed a strong outward velocity at the small gap of the cavity. Saddoughi used a larger mechanically driven device in air to investigate this flow and observed a jet emerging from the wide gap of the configuration, contrary to the findings of Jacobson and Reynolds. More recently, Lachowiez and Wlezien are investigating the flow generated by an electro-mechanically driven lid to be used for assertion control in aerodynamic applications. We are simulating the flows generated by these devices and we are conducting a parametric study that would help us elucidate the physical mechanisms present in the flow. Conventional computational schemes encounter difficulties when simulating flows around complex configurations undergoing arbitrary motions. Here we present a formulation that achieves this task on a purely Lagrangian frame by extending the formulation presented by Koumoutsakos, Leonard and Pepin. The viscous effects are taken into account by modifying the strength of the particles, whereas fast multipole schemes employing hundreds of thousands ol'particle's allow for high resolution simulations

  12. 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.

  13. 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.

  14. 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

  15. Drive-train simulator for a fuel cell hybrid vehicle

    NASA Astrophysics Data System (ADS)

    Brown, Darren; Alexander, Marcus; Brunner, Doug; Advani, Suresh G.; Prasad, Ajay K.

    The model formulation, development process, and experimental validation of a new vehicle powertrain simulator called LFM (Light, Fast, and Modifiable) are presented. The existing powertrain simulators were reviewed and it was concluded that there is a need for a new, easily modifiable simulation platform that will be flexible and sufficiently robust to address a variety of hybrid vehicle platforms. First, the structure and operating principle of the LFM simulator are presented, followed by a discussion of the subsystems and input/output parameters. Finally, a validation exercise is presented in which the simulator's inputs were specified to represent the University of Delaware's fuel cell hybrid transit vehicle and "driven" using an actual drive cycle acquired from it. Good agreement between the output of the simulator and the physical data acquired by the vehicle's on-board sensors indicates that the simulator constitutes a powerful and reliable design tool.

  16. 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.

  17. 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.

  18. Modeling Particle Rolling Behavior by the Modified Eccentric Circle Model of DEM

    NASA Astrophysics Data System (ADS)

    Chang, Yi-Long; Chen, Tsung-Hsien; Weng, Meng-Chia

    2012-09-01

    This study proposes a modified eccentric circle model to simulate the rolling resistance of circle particles through the distinct element method (DEM) simulation. The proposed model contains two major concepts: eccentric circle and local rotational damping. The mass center of a circular particle is first adjusted slightly for eccentricity to provide rotational stiffness. Local rotational damping is adopted to dissipate energy in the rotational direction. These associated material parameters can be obtained easily from the rolling behavior of one rod. This study verifies the proposed model with the repose angle tests of chalk rod assemblies, and the simulated results were satisfactory. Simulations using other existing models were also conducted for comparison, showing that the proposed model achieved better results. A landslide model test was further simulated, and this simulation agreed with both the failure pattern and the sliding process. In conclusion, particle rolling simulation using the proposed model appears to approach the actual particle trajectory, making it useful for various applications.

  19. Multidimensional computer simulation of Stirling cycle engines

    NASA Astrophysics Data System (ADS)

    Hall, Charles A.; Porsching, Thomas A.

    1992-07-01

    This report summarizes the activities performed under NASA-Grant NAG3-1097 during 1991. During that period, work centered on the following tasks: (1) to investigate more effective solvers for ALGAE; (2) to modify the plotting package for ALGAE; and (3) to validate ALGAE by simulating oscillating flow problems similar to those studied by Kurzweg and Ibrahim.

  20. Simulation studies on sputtering in rough surface

    NASA Astrophysics Data System (ADS)

    Kenmotsu, T.; Yamamura, Y.; Muramoto, T.; Hirotani, N.

    2005-01-01

    The influence of a surface roughness on sputtering is studied using a Monte Carlo simulation code ACAT. In order to estimate this influence in ACAT calculation, the ACAT code is modified. The two-dimensional fractal surface model is applied to the ACAT code and a surface binding energy of a target material is estimated by a many-body tight-binding potential. Simulation results calculated with the modified ACAT are compared with experimental data and the standard planar ACAT on sputtering yields of a Mo surface irradiated with 2 keV D+ ions. The modified ACAT code predicts well experimental data from rough surfaces compared with the standard planar ACAT code.

  1. Multiplexed DNA-modified electrodes.

    PubMed

    Slinker, Jason D; Muren, Natalie B; Gorodetsky, Alon A; Barton, Jacqueline K

    2010-03-03

    We report the use of silicon chips with 16 DNA-modified electrodes (DME chips) utilizing DNA-mediated charge transport for multiplexed detection of DNA and DNA-binding protein targets. Four DNA sequences were simultaneously distinguished on a single DME chip with 4-fold redundancy, including one incorporating a single base mismatch. These chips also enabled investigation of the sequence-specific activity of the restriction enzyme Alu1. DME chips supported dense DNA monolayer formation with high reproducibility, as confirmed by statistical comparison to commercially available rod electrodes. The working electrode areas on the chips were reduced to 10 microm in diameter, revealing microelectrode behavior that is beneficial for high sensitivity and rapid kinetic analysis. These results illustrate how DME chips facilitate sensitive and selective detection of DNA and DNA-binding protein targets in a robust and internally standardized multiplexed format.

  2. Multiplexed DNA-Modified Electrodes

    PubMed Central

    Slinker, Jason D.; Muren, Natalie B.; Gorodetsky, Alon A.; Barton, Jacqueline K.

    2011-01-01

    We report the use of silicon chips with 16 DNA-modified electrodes (DME chips) utilizing DNA-mediated charge transport for multiplexed detection of DNA and DNA-binding protein targets. Four DNA sequences were simultaneously distinguished on a single DME chip with fourfold redundancy, including one incorporating a single base mismatch. These chips also enabled investigation of the sequence-specific activity of the restriction enzyme Alu1. DME chips supported dense DNA monolayer formation with high reproducibility, as confirmed by statistical comparison to commercially available rod electrodes. The working electrode areas on the chips were reduced to 10 µm in diameter, revealing microelectrode behavior that is beneficial for high sensitivity and rapid kinetic analysis. These results illustrate how DME chips facilitate sensitive and selective detection of DNA and DNA-binding protein targets in a robust and internally standardized multiplexed format. PMID:20131780

  3. Dark energy versus modified gravity.

    PubMed

    Kunz, Martin; Sapone, Domenico

    2007-03-23

    There is now strong observational evidence that the expansion of the Universe is accelerating. The standard explanation invokes an unknown "dark energy" component. But such scenarios are faced with serious theoretical problems, which has led to increased interest in models where instead general relativity is modified in a way that leads to the observed accelerated expansion. The question then arises whether the two scenarios can be distinguished. Here we show that this may not be so easy, demonstrating explicitly that a generalized dark energy model can match the growth rate of the Dvali-Gabadadze-Porrati model and reproduce the 3+1 dimensional metric perturbations. Cosmological observations are then unable to distinguish the two cases.

  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. Time reversal for modified oscillators

    NASA Astrophysics Data System (ADS)

    Cordero-Soto, R.; Suslov, S. K.

    2010-03-01

    We consider a new completely integrable case of the time-dependent Schrödinger equation in ®n with variable coefficients for a modified oscillator that is dual (with respect to time reversal) to a model of the quantum oscillator. We find a second pair of dual Hamiltonians in the momentum representation. The examples considered show that in mathematical physics and quantum mechanics, a change in the time direction may require a total change of the system dynamics to return the system to its original quantum state. We obtain particular solutions of the corresponding nonlinear Schrödinger equations. We also consider a Hamiltonian structure of the classical integrable problem and its quantization.

  6. 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.

  7. 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.

  8. The Modified Embedded Atom Method

    SciTech Connect

    Baskes, M.I.

    1994-08-01

    Recent modifications have been made to generalize the Embedded Atom Method (EAM) to describe bonding in diverse materials. By including angular dependence of the electron density in an empirical way, the Modified Embedded Atom Method (MEAM) has been able to reproduce the basic energetic and structural properties of 45 elements. This method is ideally suited for examining the interfacial behavior of dissimilar materials. This paper explains in detail the derivation of the method, shows how the parameters of the MEAM are determined directly from experiment or first principles calculations, and examines the quality of the reproduction of the database. Materials with fcc, bcc, hcp, and diamond cubic crystal structure are discussed. A few simple examples of the application of the MEAM to surfaces and interfaces are presented. Calculations of pullout of a SiC fiber in a diamond matrix as a function of applied stress show non-uniform deformation of the fiber.

  9. Simulation - ASTP

    NASA Image and Video Library

    1974-09-01

    S74-28972 (20 Sept. 1974) --- Astronaut Vance D. Brand (foreground) and cosmonaut Aleksandr S. Ivanchenko are seated in the Docking Module trainer in Building 35 during Apollo-Soyuz Test Project simulation training at the Johnson Space Center. Brand is the command module pilot of the American ASTP prime crew. Ivanchenko is the engineer on the Soviet ASTP fourth crew (backup). During the exercise the American ASTP crew and the Soviet ASTP crew simulated docking the Apollo and Soyuz in Earth orbit and transferring to each other?s spacecraft. The Docking Module is designed to link the Apollo and Soyuz spacecraft. The ASTP crewmen are training in both the U.S. and USSR for the joint mission scheduled for the summer of 1975. This view is looking from inside the Command Module into the Docking Module. The hatchway loading into the Soyuz spacecraft orbital module mock-up is in the background.

  10. 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.

  11. RCS Simulation

    DTIC Science & Technology

    2005-05-01

    store config.) to be considered, Moving parts to be considered · Hybridisation of methods · Fast algorithms, new Aproaches · Geometry representations...Page 2 Military Aircraft Overview • Introduction • Methods ,Tools for mm-wave applications • Examples • Further requirements / developments Page 3...Flexible handling of Geometry · Parametrisation of Geometry Page 4 Military Aircraft Methods for RCS simulations •Fundamental subdivision between full

  12. DSN Simulator

    NASA Technical Reports Server (NTRS)

    Fijany, Amir; Vatan, Farrokh; Barrett, Anthony; James, Mark; Mackey, Ryan; Williams, Colin

    2009-01-01

    The DSN Simulator (wherein DSN signifies NASA's Deep Space Network) is an updated version of the software described in DSN Array Simulator (NPO-44506), Software Tech Briefs (Special supplement to NASA Tech Briefs), Vol. 32, No. 9 (September 2008), page 26. To recapitulate: This software is used for computational modeling of proposed DSN facilities comprising arrays of antennas and transmitting and receiving equipment for microwave communication with spacecraft on interplanetary missions. Such modeling is performed to estimate facility performance, evaluate requirements that govern facility design, and evaluate proposed improvements in hardware and/or software. The software includes a Monte Carlo simulation component that enables rapid generation of key mission-set metrics (e.g., numbers of links, data rates, and data volumes), and statistical distributions thereof as functions of time. The prior version of the software could model only one DSN facility at a time and included hard-coded, unconfigurable metrics. The present updated version is capable of modeling the entire DSN and provides for configurable metrics, making it possible to perform loading analyses for alternative future DSN architectures and mission-set scenarios. The present version also features an improved user interface and interfaces for exchange of data with other DSN software and with a DSN mission model database.

  13. Accurate Critical Parameters for the Modified Lennard-Jones Model

    NASA Astrophysics Data System (ADS)

    Okamoto, Kazuma; Fuchizaki, Kazuhiro

    2017-03-01

    The critical parameters of the modified Lennard-Jones system were examined. The isothermal-isochoric ensemble was generated by conducting a molecular dynamics simulation for the system consisting of 6912, 8788, 10976, and 13500 particles. The equilibrium between the liquid and vapor phases was judged from the chemical potential of both phases upon establishing the coexistence envelope, from which the critical temperature and density were obtained invoking the renormalization group theory. The finite-size scaling enabled us to finally determine the critical temperature, pressure, and density as Tc = 1.0762(2), pc = 0.09394(17), and ρc = 0.331(3), respectively.

  14. Performance Evaluation Of Modified V-Blast In Mimo System

    NASA Astrophysics Data System (ADS)

    Suneetha, Ch.; Harathi, N.; Sudha, K.

    2012-03-01

    The MIMO system (multiple Antennas at the transmitter and receiver)is a capable of very high theoretical capacities, the most popular architecture is so called vertical VBLAST. VBLAST is an effective detection method for MIMO communication system, but has large computational complexity due its successive iteration . In this paper we used modified VBLAST to lessen its computational complexity reducing the number of successive iterations. As a result of this simplification, the computational complexity of the detection is lowered significantly. Simulation results show that the proposed V-BLAST reduces calculation complexity by about 30% while achieving a very close BER performance s the original one.

  15. GENERAL: A modified weighted probabilistic cellular automaton traffic flow model

    NASA Astrophysics Data System (ADS)

    Zhuang, Qian; Jia, Bin; Li, Xin-Gang

    2009-08-01

    This paper modifies the weighted probabilistic cellular automaton model (Li X L, Kuang H, Song T, et al 2008 Chin. Phys. B 17 2366) which considered a diversity of traffic behaviors under real traffic situations induced by various driving characters and habits. In the new model, the effects of the velocity at the last time step and drivers' desire for acceleration are taken into account. The fundamental diagram, spatial-temporal diagram, and the time series of one-minute data are analyzed. The results show that this model reproduces synchronized flow. Finally, it simulates the on-ramp system with the proposed model. Some characteristics including the phase diagram are studied.

  16. Hydrodynamic modeling of granular flows in a modified Couette cell.

    PubMed

    Jop, Pierre

    2008-03-01

    We present simulations of granular flows in a modified Couette cell, using a continuum model recently proposed for dense granular flows. Based on a friction coefficient, which depends on an inertial number, the model captures the positions of the wide shear bands. We show that a smooth transition in velocity-profile shape occurs when the height of the granular material is increased, leading to a differential rotation of the central part close to the surface. The numerical predictions are in qualitative agreement with previous experimental results. The model provides predictions for the increase of the shear band width when the rotation rate is increased.

  17. Edge plane pyrolytic graphite electrode covalently modified with 2-anthraquinonyl groups: theory and experiment.

    PubMed

    Kozub, Barbara R; Henstridge, Martin C; Batchelor-McAuley, Christopher; Compton, Richard G

    2011-10-24

    An edge plane pyrolitic graphite (EPPG) electrode was modified by electrochemical reduction of anthraquinone-2-diazonium tetrafluoroborate (AQ2-N(2)(+)BF(4)(-)), giving an EPPG-AQ2-modified electrode of a surface coverage below a monolayer. Cyclic voltammograms simulated using Marcus-Hush theory for 2e(-) process assuming a uniform surface gave unrealistically low values of reorganisation energies, λ, for both electron transfer steps. Subsequently, two models of surface inhomogeneity based on Marcus-Hush theory were investigated: a distribution of formal potentials, E', and a distribution of electron tunneling distances, r(0). The simulation of cyclic voltammograms involving the distribution of formal potentials showed a better fit than the simulation with the distribution of tunneling distances. Importantly the reorganization energies used for the simulation of E' distribution were similar to the literature values for adsorbed species.

  18. Modified-PCNL without modified instruments: a description of technique.

    PubMed

    Lipsky, Michael J; Shapiro, Edan Y; Cha, Doh Yoon; Gupta, Mantu

    2013-06-01

    Mini-PCNL was developed to reduce the morbidity of PCNL by using smaller tract sizes. Most mini-techniques, however, require specialized instruments and use ureteroscopes as surrogates for nephroscopes, resulting in decreased visualization, poor irrigation, and difficult fragment extraction. We describe our modified technique (mPCNL) that allows for the use of standard PCNL equipment through a tract that is smaller than standard PCNL (sPCNL) but larger than previously reported for mini-PCNL. After ureteral access with a coaxial anti-retropulsion device, the patient is placed in the prone position. After percutaneous access under fluoroscopic guidance, a 24F balloon dilating catheter is used to place a 24F Amplatz sheath. A standard 26F rigid nephroscope is used to complete the entire procedure, with the modification of selectively removing the outer sheath to allow the scope to fit in the smaller tract. Standard lithotripters and graspers are used, as necessary. ROLE IN PRACTICE: We have performed this technique on 52 patients with a mean stone burden of 19.4 mm. Overall stone-free rate was 100%, even for stones >2 cm. This technique allows for improved visualization and irrigation compared with other mini-PCNL procedures and obviates the need to purchase specialized equipment.

  19. 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

  20. 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.