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Sample records for accurate initial conditions

  1. Toward accurate modelling of the non-linear matter bispectrum: standard perturbation theory and transients from initial conditions

    NASA Astrophysics Data System (ADS)

    McCullagh, Nuala; Jeong, Donghui; Szalay, Alexander S.

    2016-01-01

    Accurate modelling of non-linearities in the galaxy bispectrum, the Fourier transform of the galaxy three-point correlation function, is essential to fully exploit it as a cosmological probe. In this paper, we present numerical and theoretical challenges in modelling the non-linear bispectrum. First, we test the robustness of the matter bispectrum measured from N-body simulations using different initial conditions generators. We run a suite of N-body simulations using the Zel'dovich approximation and second-order Lagrangian perturbation theory (2LPT) at different starting redshifts, and find that transients from initial decaying modes systematically reduce the non-linearities in the matter bispectrum. To achieve 1 per cent accuracy in the matter bispectrum at z ≤ 3 on scales k < 1 h Mpc-1, 2LPT initial conditions generator with initial redshift z ≳ 100 is required. We then compare various analytical formulas and empirical fitting functions for modelling the non-linear matter bispectrum, and discuss the regimes for which each is valid. We find that the next-to-leading order (one-loop) correction from standard perturbation theory matches with N-body results on quasi-linear scales for z ≥ 1. We find that the fitting formula in Gil-Marín et al. accurately predicts the matter bispectrum for z ≤ 1 on a wide range of scales, but at higher redshifts, the fitting formula given in Scoccimarro & Couchman gives the best agreement with measurements from N-body simulations.

  2. Initial Cladding Condition

    SciTech Connect

    E. Siegmann

    2000-08-22

    The purpose of this analysis is to describe the condition of commercial Zircaloy clad fuel as it is received at the Yucca Mountain Project (YMP) site. Most commercial nuclear fuel is encased in Zircaloy cladding. This analysis is developed to describe cladding degradation from the expected failure modes. This includes reactor operation impacts including incipient failures, potential degradation after reactor operation during spent fuel storage in pool and dry storage and impacts due to transportation. Degradation modes include cladding creep, and delayed hydride cracking during dry storage and transportation. Mechanical stresses from fuel handling and transportation vibrations are also included. This Analysis and Model Report (AMR) does not address any potential damage to assemblies that might occur at the YMP surface facilities. Ranges and uncertainties have been defined. This analysis will be the initial boundary condition for the analysis of cladding degradation inside the repository. In accordance with AP-2.13Q, ''Technical Product Development Planning'', a work plan (CRWMS M&O 2000c) was developed, issued, and utilized in the preparation of this document. There are constraints, caveats and limitations to this analysis. This cladding degradation analysis is based on commercial Pressurized Water Reactor (PWR) fuel with Zircaloy cladding but is applicable to Boiling Water Reactor (BWR) fuel. Reactor operating experience for both PWRs and BWRs is used to establish fuel reliability from reactor operation. It is limited to fuel exposed to normal operation and anticipated operational occurrences (i.e. events which are anticipated to occur within a reactor lifetime), and not to fuel that has been exposed to severe accidents. Fuel burnup projections have been limited to the current commercial reactor licensing environment with restrictions on fuel enrichment, oxide coating thickness and rod plenum pressures. The information provided in this analysis will be used in

  3. Accurate transcription initiation by RNA polymerase II in a soluble extract from isolated mammalian nuclei.

    PubMed Central

    Dignam, J D; Lebovitz, R M; Roeder, R G

    1983-01-01

    We have developed a procedure for preparing extracts from nuclei of human tissue culture cells that directs accurate transcription initiation in vitro from class II promoters. Conditions of extraction and assay have been optimized for maximum activity using the major late promoter of adenovirus 2. The extract also directs accurate transcription initiation from other adenovirus promoters and cellular promoters. The extract also directs accurate transcription initiation from class III promoters (tRNA and Ad 2 VA). Images PMID:6828386

  4. GALIC: Galaxy initial conditions construction

    NASA Astrophysics Data System (ADS)

    Yurin, Denis; Springel, Volker

    2014-08-01

    GalIC (GALaxy Initial Conditions) is an implementation of an iterative method to construct steady state composite halo-disk-bulge galaxy models with prescribed density distribution and velocity anisotropy that can be used as initial conditions for N-body simulations. The code is parallelized for distributed memory based on MPI. While running, GalIC produces "snapshot files" that can be used as initial conditions files. GalIC supports the three file formats ('type1' format, the slightly improved 'type2' format, and an HDF5 format) of the GADGET (ascl:0003.001) code for its output snapshot files.

  5. Initial conditions for bubble universes

    NASA Astrophysics Data System (ADS)

    McInnes, Brett

    2008-06-01

    The “bubble universes” of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for inflation were established. I argue that the simplest nonanthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but (because it violates energy conditions) there is a danger that it could lead to nonperturbative instabilities in string theory. I make a simple proposal for the initial conditions of a bubble universe, and show that my proposal ensures that the system is nonperturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the second law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.

  6. Quantum Measurement and Initial Conditions

    NASA Astrophysics Data System (ADS)

    Stoica, Ovidiu Cristinel

    2016-03-01

    Quantum measurement finds the observed system in a collapsed state, rather than in the state predicted by the Schrödinger equation. Yet there is a relatively spread opinion that the wavefunction collapse can be explained by unitary evolution (for instance in the decoherence approach, if we take into account the environment). In this article it is proven a mathematical result which severely restricts the initial conditions for which measurements have definite outcomes, if pure unitary evolution is assumed. This no-go theorem remains true even if we take the environment into account. The result does not forbid a unitary description of the measurement process, it only shows that such a description is possible only for very restricted initial conditions. The existence of such restrictions of the initial conditions can be understood in the four-dimensional block universe perspective, as a requirement of global self-consistency of the solutions of the Schrödinger equation.

  7. Initial conditions and quantum cosmology

    NASA Technical Reports Server (NTRS)

    Hartle, James B.

    1987-01-01

    A theory of initial conditions is necessary for a complete explanation of the presently observed large scale structural features of the universe, and a quantum theory of cosmology is probably needed for its formulation. The kinematics of quantum cosmology are reviewed, and some candidates for a law of initial conditions are discussed. The proposal that the quantum state of a closed universe is the natural analog of the ground state for closed cosmologies and is specified by a Euclidean sum over histories is sketched. When implemented in simple models, this proposal is consistent with the most important large-scale observations.

  8. New Claus catalyst tests accurately reflect process conditions

    SciTech Connect

    Maglio, A.; Schubert, P.F.

    1988-09-12

    Methods for testing Claus catalysts are developed that more accurately represent the actual operating conditions in commercial sulfur recovery units. For measuring catalyst activity, an aging method has been developed that results in more meaningful activity data after the catalyst has been aged, because all catalysts undergo rapid initial deactivation in commercial units. An activity test method has been developed where catalysts can be compared at less than equilibrium conversion. A test has also been developed to characterize abrasion loss of Claus catalysts, in contrast to the traditional method of determining physical properties by measuring crush strengths. Test results from a wide range of materials correlated well with actual pneumatic conveyance attrition. Substantial differences in Claus catalyst properties were observed as a result of using these tests.

  9. DICE: Disk Initial Conditions Environment

    NASA Astrophysics Data System (ADS)

    Perret, Valentin

    2016-07-01

    DICE models initial conditions of idealized galaxies to study their secular evolution or their more complex interactions such as mergers or compact groups using N-Body/hydro codes. The code can set up a large number of components modeling distinct parts of the galaxy, and creates 3D distributions of particles using a N-try MCMC algorithm which does not require a prior knowledge of the distribution function. The gravitational potential is then computed on a multi-level Cartesian mesh by solving the Poisson equation in the Fourier space. Finally, the dynamical equilibrium of each component is computed by integrating the Jeans equations for each particles. Several galaxies can be generated in a row and be placed on Keplerian orbits to model interactions. DICE writes the initial conditions in the Gadget1 or Gadget2 (ascl:0003.001) format and is fully compatible with Ramses (ascl:1011.007).

  10. Hydrodynamics from Landau initial conditions

    SciTech Connect

    Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read jr, Kenneth F.; Wong, Cheuk-Yin

    2015-01-01

    We investigate ideal hydrodynamic evolution, with Landau initial conditions, both in a semi-analytical 1+1D approach and in a numerical code incorporating event-by-event variation with many events and transverse density inhomogeneities. The object of the calculation is to test how fast would a Landau initial condition transition to a commonly used boost-invariant expansion. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of O (20 - 30%) expected at freezeout for most scenarios. Moreover, the deviation from boost-invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, 2+1 dimensional hydrodynamics is inadequate to extract transport coefficients of the quark-gluon plasma. Based on [1, 2

  11. Initial conditions for vector inflation

    SciTech Connect

    Chiba, Takeshi

    2008-08-15

    Recently, a model of inflation using non-minimally coupled massive vector fields has been proposed. For a particular choice of non-minimal coupling parameter and for a flat Friedmann-Robertson-Walker model, the model is reduced to the model of chaotic inflation with massive scalar field. We study the effect of non-zero curvature of the universe on the onset of vector inflation. We find that in a curved universe the dynamics of vector inflation can be different from the dynamics of chaotic inflation, and the fraction of the initial conditions leading to inflationary solutions is reduced as compared with the chaotic inflation case.

  12. Numerical evolution of multiple black holes with accurate initial data

    SciTech Connect

    Galaviz, Pablo; Bruegmann, Bernd; Cao Zhoujian

    2010-07-15

    We present numerical evolutions of three equal-mass black holes using the moving puncture approach. We calculate puncture initial data for three black holes solving the constraint equations by means of a high-order multigrid elliptic solver. Using these initial data, we show the results for three black hole evolutions with sixth-order waveform convergence. We compare results obtained with the BAM and AMSS-NCKU codes with previous results. The approximate analytic solution to the Hamiltonian constraint used in previous simulations of three black holes leads to different dynamics and waveforms. We present some numerical experiments showing the evolution of four black holes and the resulting gravitational waveform.

  13. Initial conditions and sampling for multifield inflation

    SciTech Connect

    Easther, Richard; Price, Layne C. E-mail: lpri691@aucklanduni.ac.nz

    2013-07-01

    We investigate the initial conditions problem for multifield inflation. In these scenarios the pre-inflationary dynamics can be chaotic, increasing the sensitivity of the onset of inflation to the initial data even in the homogeneous limit. To analyze physically equivalent scenarios we compare initial conditions at fixed energy. This ensures that each trajectory is counted once and only once, since the energy density decreases monotonically. We present a full analysis of hybrid inflation that reveals a greater degree of long range order in the set of ''successful'' initial conditions than was previously apparent. In addition, we explore the effective smoothing scale for the fractal set of successful initial conditions induced by the finite duration of the pre-inflationary phase. The role of the prior information used to specify the initial data is discussed in terms of Bayesian sampling.

  14. Accurate Orientation Estimation Using AHRS under Conditions of Magnetic Distortion

    PubMed Central

    Yadav, Nagesh; Bleakley, Chris

    2014-01-01

    Low cost, compact attitude heading reference systems (AHRS) are now being used to track human body movements in indoor environments by estimation of the 3D orientation of body segments. In many of these systems, heading estimation is achieved by monitoring the strength of the Earth's magnetic field. However, the Earth's magnetic field can be locally distorted due to the proximity of ferrous and/or magnetic objects. Herein, we propose a novel method for accurate 3D orientation estimation using an AHRS, comprised of an accelerometer, gyroscope and magnetometer, under conditions of magnetic field distortion. The system performs online detection and compensation for magnetic disturbances, due to, for example, the presence of ferrous objects. The magnetic distortions are detected by exploiting variations in magnetic dip angle, relative to the gravity vector, and in magnetic strength. We investigate and show the advantages of using both magnetic strength and magnetic dip angle for detecting the presence of magnetic distortions. The correction method is based on a particle filter, which performs the correction using an adaptive cost function and by adapting the variance during particle resampling, so as to place more emphasis on the results of dead reckoning of the gyroscope measurements and less on the magnetometer readings. The proposed method was tested in an indoor environment in the presence of various magnetic distortions and under various accelerations (up to 3 g). In the experiments, the proposed algorithm achieves <2° static peak-to-peak error and <5° dynamic peak-to-peak error, significantly outperforming previous methods. PMID:25347584

  15. Novel quantum initial conditions for inflation

    NASA Astrophysics Data System (ADS)

    Handley, W. J.; Lasenby, A. N.; Hobson, M. P.

    2016-07-01

    We present a novel approach for setting initial conditions on the mode functions of the Mukhanov-Sasaki equation. These conditions are motivated by minimization of the renormalized stress-energy tensor and are valid for setting a vacuum state even in a context where the spacetime is changing rapidly. Moreover, these alternative conditions are potentially observationally distinguishable. We apply this to the kinetically dominated universe and compare with the more traditional approach.

  16. ZInCo: Zoomed Initial Conditions

    NASA Astrophysics Data System (ADS)

    Garaldi, Enrico

    2015-11-01

    ZInCo manipulates existing initial conditions (ICs) compatible with GADGET-2/3 (ascl:0003.001) ICs, allowing different flavors of zoom-in simulations rather then producing new ICs from scratch. The code can manipulate initial conditions with multiple types of particles, unlike the vast majority of zoom-in ICs codes available, preserving their properties and random field. This allows ZInCo to take advantage of other codes that produce ICs featuring a broad range of different cosmologies; it can be used also on existing ICs even in the unlikely case nothing is known about their properties. The code is written in C++ and parallelized using MPI.

  17. Step initiation in Parkinson's disease: influence of initial stance conditions.

    PubMed

    Rocchi, Laura; Chiari, Lorenzo; Mancini, Martina; Carlson-Kuhta, Patricia; Gross, Anne; Horak, Fay B

    2006-10-01

    In this study, we investigated how the size of preparatory postural adjustments prior to step initiation, and step length and velocity depend on initial stance width in patients with Parkinson's disease (PD) both in the ON and OFF levodopa states and in healthy elderly subjects. Twenty-one subjects with idiopathic PD and 24 age-matched healthy control subjects took two steps starting with feet on a two-plate force-platform, from either narrow or wide stance width. We measured how the magnitude of anticipatory postural adjustments (APA) and step characteristics scaled with stance width. Results showed that preparation for step initiation from wide stance was associated with a larger lateral and backward center of pressure (CoP) displacement than from narrow stance. Velocity and length of the first step were also sensitive to initial stance conditions, probably in relation with the differences in the corresponding APA. On the contrary, the duration of APA was not significantly affected by initial stance width, but it was longer in PD compared to healthy subjects, and speeded up by levodopa. Although subjects with PD did scale up the size of their APA with stance width, they had much more difficulty initiating a step from a wide stance than from a narrow stance, as shown by the greater differences from control subjects in the magnitude of the APA. Our results support the hypothesis that PD subjects maintain a narrow stance as a compensation for their inability to sufficiently increase the size of their lateral APA to allow fast step initiation in wide stance.

  18. Accurate boundary conditions for exterior problems in gas dynamics

    NASA Technical Reports Server (NTRS)

    Hagstrom, Thomas; Hariharan, S. I.

    1988-01-01

    The numerical solution of exterior problems is typically accomplished by introducing an artificial, far field boundary and solving the equations on a truncated domain. For hyperbolic systems, boundary conditions at this boundary are often derived by imposing a principle of no reflection. However, waves with spherical symmetry in gas dynamics satisfy equations where incoming and outgoing Riemann variables are coupled. This suggests that natural reflections may be important. A reflecting boundary condition is proposed based on an asymptotic solution of the far field equations. Nonlinear energy estimates are obtained for the truncated problem and numerical experiments presented to validate the theory.

  19. Accurate boundary conditions for exterior problems in gas dynamics

    NASA Technical Reports Server (NTRS)

    Hagstrom, Thomas; Hariharan, S. I.

    1988-01-01

    The numerical solution of exterior problems is typically accomplished by introducing an artificial, far-field boundary and solving the equations on a truncated domain. For hyperbolic systems, boundary conditions at this boundary are often derived by imposing a principle of no reflection. However, waves with spherical symmetry in gas dynamics satisfy equations where incoming and outgoing Riemann variables are coupled. This suggests that natural reflections may be important. A reflecting boundary condition is proposed based on an asymptotic solution of the far-field equations. Nonlinear energy estimates are obtained for the truncated problem and numerical experiments presented to validate the theory.

  20. Evaluation of new reference genes in papaya for accurate transcript normalization under different experimental conditions.

    PubMed

    Zhu, Xiaoyang; Li, Xueping; Chen, Weixin; Chen, Jianye; Lu, Wangjin; Chen, Lei; Fu, Danwen

    2012-01-01

    Real-time reverse transcription PCR (RT-qPCR) is a preferred method for rapid and accurate quantification of gene expression studies. Appropriate application of RT-qPCR requires accurate normalization though the use of reference genes. As no single reference gene is universally suitable for all experiments, thus reference gene(s) validation under different experimental conditions is crucial for RT-qPCR analysis. To date, only a few studies on reference genes have been done in other plants but none in papaya. In the present work, we selected 21 candidate reference genes, and evaluated their expression stability in 246 papaya fruit samples using three algorithms, geNorm, NormFinder and RefFinder. The samples consisted of 13 sets collected under different experimental conditions, including various tissues, different storage temperatures, different cultivars, developmental stages, postharvest ripening, modified atmosphere packaging, 1-methylcyclopropene (1-MCP) treatment, hot water treatment, biotic stress and hormone treatment. Our results demonstrated that expression stability varied greatly between reference genes and that different suitable reference gene(s) or combination of reference genes for normalization should be validated according to the experimental conditions. In general, the internal reference genes EIF (Eukaryotic initiation factor 4A), TBP1 (TATA binding protein 1) and TBP2 (TATA binding protein 2) genes had a good performance under most experimental conditions, whereas the most widely present used reference genes, ACTIN (Actin 2), 18S rRNA (18S ribosomal RNA) and GAPDH (Glyceraldehyde-3-phosphate dehydrogenase) were not suitable in many experimental conditions. In addition, two commonly used programs, geNorm and Normfinder, were proved sufficient for the validation. This work provides the first systematic analysis for the selection of superior reference genes for accurate transcript normalization in papaya under different experimental conditions.

  1. Fluid flow in nanopores: Accurate boundary conditions for carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sokhan, Vladimir P.; Nicholson, David; Quirke, Nicholas

    2002-11-01

    Steady-state Poiseuille flow of a simple fluid in carbon nanopores under a gravitylike force is simulated using a realistic empirical many-body potential model for carbon. Building on our previous study of slit carbon nanopores we show that fluid flow in a nanotube is also characterized by a large slip length. By analyzing temporal profiles of the velocity components of particles colliding with the wall we obtain values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall and, for the first time, propose slip boundary conditions for smooth continuum surfaces such that they are equivalent in adsorption, diffusion, and fluid flow properties to fully dynamic atomistic models.

  2. Initial models in conditionals: evidence from priming.

    PubMed

    Espino, Orlando; Santamaría, Carlos

    2008-05-01

    We examined the comprehension of different types of conditionals. We measured the reading time of sentences primed by different types of conditionals (Experiments 1 and 2). We found that the participants read not-p and not-q faster when it was primed by the conditional form p if q and they were slower to read p and q when it was primed by the conditional form p only if q. This effect disappeared in the second experiment, where the order of the elements was reversed (q and p and not-q and not-p). These results suggest that the conditional form p if q elicits an initial representation "from p to q" with two possibilities, while the conditional form p only if q elicits a reverse representation with only one possibility. The third experiment showed that there were effects of the order only for the conditional if p then q, which confirms the reverse representation hypothesis. We discuss the implications of these results for different theories of conditional comprehension.

  3. On the initial condition of inflationary fluctuations

    NASA Astrophysics Data System (ADS)

    Jiang, Hongliang; Wang, Yi; Zhou, Siyi

    2016-04-01

    It is usually assumed that the inflationary fluctuations start from the Bunch-Davies (BD) vacuum and the iε prescription is used when interactions are calculated. We show that those assumptions can be verified explicitly by calculating the loop corrections to the inflationary two-point and three-point correlation functions. Those loop corrections can be resummed to exponential factors, which suppress non-BD coefficients and behave as the iε factor for the case of the BD initial condition. A new technique of loop chain diagram resummation is developed for this purpose. For the non-BD initial conditions which is setup at finite time and has not fully decayed, explicit correction to the two-point and three-point correlation functions are calculated. Especially, non-Gaussianity in the folded limit is regularized due to the interactions.

  4. Initial condition of stochastic self-assembly.

    PubMed

    Davis, Jason K; Sindi, Suzanne S

    2016-02-01

    The formation of a stable protein aggregate is regarded as the rate limiting step in the establishment of prion diseases. In these systems, once aggregates reach a critical size the growth process accelerates and thus the waiting time until the appearance of the first critically sized aggregate is a key determinant of disease onset. In addition to prion diseases, aggregation and nucleation is a central step of many physical, chemical, and biological process. Previous studies have examined the first-arrival time at a critical nucleus size during homogeneous self-assembly under the assumption that at time t=0 the system was in the all-monomer state. However, in order to compare to in vivo biological experiments where protein constituents inherited by a newly born cell likely contain intermediate aggregates, other possibilities must be considered. We consider one such possibility by conditioning the unique ergodic size distribution on subcritical aggregate sizes; this least-informed distribution is then used as an initial condition. We make the claim that this initial condition carries fewer assumptions than an all-monomer one and verify that it can yield significantly different averaged waiting times relative to the all-monomer condition under various models of assembly.

  5. Initial condition of stochastic self-assembly

    NASA Astrophysics Data System (ADS)

    Davis, Jason K.; Sindi, Suzanne S.

    2016-02-01

    The formation of a stable protein aggregate is regarded as the rate limiting step in the establishment of prion diseases. In these systems, once aggregates reach a critical size the growth process accelerates and thus the waiting time until the appearance of the first critically sized aggregate is a key determinant of disease onset. In addition to prion diseases, aggregation and nucleation is a central step of many physical, chemical, and biological process. Previous studies have examined the first-arrival time at a critical nucleus size during homogeneous self-assembly under the assumption that at time t =0 the system was in the all-monomer state. However, in order to compare to in vivo biological experiments where protein constituents inherited by a newly born cell likely contain intermediate aggregates, other possibilities must be considered. We consider one such possibility by conditioning the unique ergodic size distribution on subcritical aggregate sizes; this least-informed distribution is then used as an initial condition. We make the claim that this initial condition carries fewer assumptions than an all-monomer one and verify that it can yield significantly different averaged waiting times relative to the all-monomer condition under various models of assembly.

  6. Initial conditioning of the TFTR vacuum vessel

    SciTech Connect

    Dylla, H.F.; Blanchard, W.R.; Krawchuk, R.B.; Hawryluk, R.J.; Owens, D.K.

    1984-01-01

    We report on the initial conditioning of the Tokamak Fusion Test Reactor (TFTR) vacuum vessel prior to the initiation of first plasma discharges, and during subsequent operation with high power ohmically-heated plasmas. Following evacuation of the 86 m/sup 3/ vessel with the 10/sup 4/ 1/s high vacuum pumping system, the vessel was conditioned by a 15 A dc glow discharge in H/sub 2/ at a pressure of 5 mTorr. Rapid-pulse discharge cleaning was used subsequently to preferentially condition the graphite plasma limiters. The effectiveness of the discharge cleaning was monitored by measuring the exhaust rates of the primary discharge products (CO/C/sub 2/H/sub 4/, CH/sub 4/, and H/sub 2/O). After 175 hours of glow discharge treatment, the equivalent of 50 monolayers of C and O was removed from the vessel, and the partial pressures of impurity gases were reduced to the range of 10/sup -9/-10/sup -10/ Torr.

  7. Initial conditions of radiative shock experiments

    SciTech Connect

    Kuranz, C. C.; Drake, R. P.; Krauland, C. M.; Marion, D. C.; Grosskopf, M. J.; Rutter, E.; Torralva, B.; Holloway, J. P.; Bingham, D.; Goh, J.; Boehly, T. R.; Sorce, A. T.

    2013-05-15

    We performed experiments at the Omega Laser Facility to characterize the initial, laser-driven state of a radiative shock experiment. These experiments aimed to measure the shock breakout time from a thin, laser-irradiated Be disk. The data are then used to inform a range of valid model parameters, such as electron flux limiter and polytropic γ, used when simulating radiative shock experiments using radiation hydrodynamics codes. The characterization experiment and the radiative shock experiment use a laser irradiance of ∼7 × 10{sup 14} W cm{sup −2} to launch a shock in the Be disk. A velocity interferometer and a streaked optical pyrometer were used to infer the amount of time for the shock to move through the Be disk. The experimental results were compared with simulation results from the Hyades code, which can be used to model the initial conditions of a radiative shock system using the CRASH code.

  8. The initial conditions of massive star evolution

    NASA Astrophysics Data System (ADS)

    Sana, Hugues

    2016-07-01

    Massive stars are some of the most energetic building blocks of galaxies. They are the progenitors of supernovae and of neutrons stars and black holes, the coallescence of which is one of the most likely detectable sources of gravitational waves. Yet their formation remains poorly understood. As a consequence, the mechanisms that set initial parameters such as rotation rates, multiplicity and orbital distributions are also ill constrained. These quantities are however critical as they affect the internal mixing, the rate and nature of the interactions, the stars final fates and their end-of-life products. In this presentation, I will review existing and new observations that allow us to better constraints these parameters, hence the initial conditions for massive star evolution.

  9. Causality, initial conditions, and inflationary magnetogenesis

    NASA Astrophysics Data System (ADS)

    Tsagas, Christos G.

    2016-05-01

    The post-inflationary evolution of inflation-produced magnetic fields, conventional or not, can change dramatically when two fundamental issues are accounted for. The first is causality, which demands that local physical processes can never affect superhorizon perturbations. The second is the nature of the transition from inflation to reheating and then to the radiation era, which determine the initial conditions at the start of these epochs. Causality implies that inflationary magnetic fields do not freeze into the matter until they have re-entered the causal horizon. The nature of the cosmological transitions and the associated initial conditions, on the other hand, determine the large-scale magnetic evolution after inflation. Put together, the two can slow down the adiabatic magnetic decay on superhorizon scales throughout the Universe's post-inflationary evolution and thus lead to considerably stronger residual magnetic fields. This is "good news" for both the conventional and the nonconventional scenarios of cosmic magnetogenesis. Mechanisms operating outside standard electromagnetism, in particular, do not need to enhance their fields too much during inflation in order to produce seeds that can feed the galactic dynamo today. In fact, even conventionally produced inflationary magnetic fields might be able to sustain the dynamo.

  10. Accurate label-free reaction kinetics determination using initial rate heat measurements.

    PubMed

    Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R

    2015-01-01

    Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity.

  11. Accurate label-free reaction kinetics determination using initial rate heat measurements

    PubMed Central

    Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R.

    2015-01-01

    Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity. PMID:26574737

  12. Initial condition from the shadowed Glauber model

    NASA Astrophysics Data System (ADS)

    Chatterjee, Sandeep; Singh, Sushant K.; Ghosh, Snigdha; Hasanujjaman, Md; Alam, Jane; Sarkar, Sourav

    2016-07-01

    The two component Monte-Carlo Glauber model predicts a knee-like structure in the centrality dependence of elliptic flow v2 in Uranium + Uranium collisions at √{sNN} = 193 GeV. It also produces a strong anti-correlation between v2 and dNch / dy in the case of top ZDC events. However, none of these features have been observed in data. We address these discrepancies by including the effect of nucleon shadowing to the two component Monte-Carlo Glauber model. Apart from addressing successfully the above issues, we find that the nucleon shadow suppresses the event by event fluctuation of various quantities, e.g. ε2 which is in accordance with expectation from the dynamical models of initial condition based on gluon saturation physics.

  13. MUSIC: MUlti-Scale Initial Conditions

    NASA Astrophysics Data System (ADS)

    Hahn, Oliver; Abel, Tom

    2013-11-01

    MUSIC generates multi-scale initial conditions with multiple levels of refinements for cosmological ‘zoom-in’ simulations. The code uses an adaptive convolution of Gaussian white noise with a real-space transfer function kernel together with an adaptive multi-grid Poisson solver to generate displacements and velocities following first- (1LPT) or second-order Lagrangian perturbation theory (2LPT). MUSIC achieves rms relative errors of the order of 10-4 for displacements and velocities in the refinement region and thus improves in terms of errors by about two orders of magnitude over previous approaches. In addition, errors are localized at coarse-fine boundaries and do not suffer from Fourier space-induced interference ringing.

  14. Geometric constraints in semiclassical initial value representation calculations in Cartesian coordinates: accurate reduction in zero-point energy.

    PubMed

    Issack, Bilkiss B; Roy, Pierre-Nicholas

    2005-08-22

    An approach for the inclusion of geometric constraints in semiclassical initial value representation calculations is introduced. An important aspect of the approach is that Cartesian coordinates are used throughout. We devised an algorithm for the constrained sampling of initial conditions through the use of multivariate Gaussian distribution based on a projected Hessian. We also propose an approach for the constrained evaluation of the so-called Herman-Kluk prefactor in its exact log-derivative form. Sample calculations are performed for free and constrained rare-gas trimers. The results show that the proposed approach provides an accurate evaluation of the reduction in zero-point energy. Exact basis set calculations are used to assess the accuracy of the semiclassical results. Since Cartesian coordinates are used, the approach is general and applicable to a variety of molecular and atomic systems.

  15. Memory effects induced by initial switching conditions

    NASA Astrophysics Data System (ADS)

    Martorell, J.; Sprung, D. W. L.; van Dijk, W.; Muga, J. G.

    2009-06-01

    Initial switching refers to the way in which the decay of an initially confined state begins, as the barrier isolating it from the exterior is relaxed. We study these effects in the context of Longhi’s version of the Fano-Anderson model. Most authors assume the sudden approximation where the coupling is turned on instantaneously. We consider a finite rise time T both numerically and analytically. When the coupling is ramped up linearly over a switching time T , we show that the asymptotic survival amplitude acquires a phase T and is modulated by a factor (sinT)/T . Several other results relating to the solution of the model are obtained. All site amplitudes have the same decay constant during the exponential decay regime. In the asymptotic regime, the amplitude and phase of decay oscillations depend on the initial-switching profile, but the period does not.

  16. Setting initial motion conditions in ballistic experiments

    NASA Astrophysics Data System (ADS)

    Kovalev, P. I.; Tomson, S. G.

    2007-04-01

    Questions pertaining to the formulation of initial motion conditions—an important task in the course of ballistic experiments—are considered. Effective methods for the excitation and suppression of oscillations in projectiles launched by laboratory gunpowder-charged accelerators are described. Results of tests using the proposed methods are presented.

  17. Initial Conditions in the Averaging Cognitive Model

    ERIC Educational Resources Information Center

    Noventa, S.; Massidda, D.; Vidotto, G.

    2010-01-01

    The initial state parameters s[subscript 0] and w[subscript 0] are intricate issues of the averaging cognitive models in Information Integration Theory. Usually they are defined as a measure of prior information (Anderson, 1981; 1982) but there are no general rules to deal with them. In fact, there is no agreement as to their treatment except in…

  18. Breaking Snake Camouflage: Humans Detect Snakes More Accurately than Other Animals under Less Discernible Visual Conditions

    PubMed Central

    He, Hongshen

    2016-01-01

    Humans and non-human primates are extremely sensitive to snakes as exemplified by their ability to detect pictures of snakes more quickly than those of other animals. These findings are consistent with the Snake Detection Theory, which hypothesizes that as predators, snakes were a major source of evolutionary selection that favored expansion of the visual system of primates for rapid snake detection. Many snakes use camouflage to conceal themselves from both prey and their own predators, making it very challenging to detect them. If snakes have acted as a selective pressure on primate visual systems, they should be more easily detected than other animals under difficult visual conditions. Here we tested whether humans discerned images of snakes more accurately than those of non-threatening animals (e.g., birds, cats, or fish) under conditions of less perceptual information by presenting a series of degraded images with the Random Image Structure Evolution technique (interpolation of random noise). We find that participants recognize mosaic images of snakes, which were regarded as functionally equivalent to camouflage, more accurately than those of other animals under dissolved conditions. The present study supports the Snake Detection Theory by showing that humans have a visual system that accurately recognizes snakes under less discernible visual conditions. PMID:27783686

  19. Tropical cyclone track forecasts using JMA model with ECMWF and JMA initial conditions

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Munehiko; Nakazawa, Tetsuo; Aonashi, Kazumasa

    2012-05-01

    The JMA's Global Spectral Model (JMA/GSM) was run from the initial conditions of ECMWF, which are available in the YOTC data set, to distinguish between TC track prediction errors attributable to the initial conditions and those attributable to the NWP model. The average position error was reduced by about 10% by replacing the initial conditions, and in some cases, the predictions were significantly improved. In these cases, the low wavenumber component of the ECMWF analysis was found to account for most of the improvement. In addition, the observed tracks were captured by the JMA Typhoon Ensemble Prediction System (TEPS), which deals with initial condition uncertainties. In some cases, however, the replacement of the initial conditions did not improve the prediction even when the ECMWF forecast was accurate. In these cases, TEPS could not capture the observed track either, implying the need for dealing with uncertainties associated with the NWP model.

  20. Influence of initial conditions on compressible vorticity dynamics

    NASA Astrophysics Data System (ADS)

    Virk, D.; Hussain, F.

    1993-11-01

    Prompted by the lack of a unique choice of pressure ( P) and density (ρ) fields for a compressible free vortex and by the observed dependence of turbulence dynamics on initial P and ρ in compressible simulations, we address the effects of initial conditions on the evolution of a single vortex, on the prototypical phenomenon of vortex reconnection, and on two-dimensional turbulence. Two previous choices of initial conditions used for numerical simulations of compressible turbulence have been: (i) both P and ρ uniform (constant initial conditions, CIC), and (ii) uniform ρ with P determined from the Poisson equation (constant density initial conditions, CDIC). We find these initial conditions to be inappropriate for compressible vorticity dynamics studies. Specifically, in compressible reconnection, the effects of baroclinic vorticity generation and shocklet formation cancel each other during early evolution for CDIC, thus leading to almost incompressible behavior. Although CIC captures compressibility effects, it incorrectly changes the initial vorticity distribution by introducing strong acoustic transients, thereby significantly altering the evolving dynamics. Here, a new initial condition, called polytropic initial condition (PIC), is proposed, for which the Poisson equation is solved for initially polytropically related P and ρ fields. PIC provides P and ρ distributions within vortices which are consistent with those observed in shock-wedge interaction experiment and also leads to compressible solutions with no acoustic transients. At low Mach number ( M), we show that the effects of all these three initial conditions can be predicted by low- M asymptotic theories of the Navier-Stokes equations. At high M, it is shown here that inappropriate initial conditions may alter the evolutionary dynamics and, hence, lead to wrong conclusions regarding compressibility effects. We argue that PIC is a more appropriate choice.

  1. Improving initial conditions for cosmological N-body simulations

    NASA Astrophysics Data System (ADS)

    Garrison, Lehman H.; Eisenstein, Daniel J.; Ferrer, Douglas; Metchnik, Marc V.; Pinto, Philip A.

    2016-10-01

    In cosmological N-body simulations, the representation of dark matter as discrete `macroparticles' suppresses the growth of structure, such that simulations no longer reproduce linear theory on small scales near kNyquist. Marcos et al. demonstrate that this is due to sparse sampling of modes near kNyquist and that the often-assumed continuum growing modes are not proper growing modes of the particle system. We develop initial conditions (ICs) that respect the particle linear theory growing modes and then rescale the mode amplitudes to account for growth suppression. These ICs also allow us to take advantage of our very accurate N-body code ABACUS to implement second-order Lagrangian perturbation theory (2LPT) in configuration space. The combination of 2LPT and rescaling improves the accuracy of the late-time power spectra, halo mass functions, and halo clustering. In particular, we achieve 1 per cent accuracy in the power spectrum down to kNyquist, versus kNyquist/4 without rescaling or kNyquist/13 without 2LPT, relative to an oversampled reference simulation. We anticipate that our 2LPT will be useful for large simulations where fast Fourier transforms are expensive and that rescaling will be useful for suites of medium-resolution simulations used in cosmic emulators and galaxy survey mock catalogues. Code to generate ICs is available at https://github.com/lgarrison/zeldovich-PLT.

  2. ATMOSPHERIC CIRCULATION OF HOT JUPITERS: INSENSITIVITY TO INITIAL CONDITIONS

    SciTech Connect

    Liu Beibei; Showman, Adam P.

    2013-06-10

    The ongoing characterization of hot Jupiters has motivated a variety of circulation models of their atmospheres. Such models must be integrated starting from an assumed initial state, which is typically taken to be a wind-free, rest state. Here, we investigate the sensitivity of hot-Jupiter atmospheric circulation to initial conditions with shallow-water models and full three-dimensional models. Those models are initialized with zonal jets, and we explore a variety of different initial jet profiles. We demonstrate that, in both classes of models, the final, equilibrated state is independent of initial condition-as long as frictional drag near the bottom of the domain and/or interaction with a specified planetary interior are included so that the atmosphere can adjust angular momentum over time relative to the interior. When such mechanisms are included, otherwise identical models initialized with vastly different initial conditions all converge to the same statistical steady state. In some cases, the models exhibit modest time variability; this variability results in random fluctuations about the statistical steady state, but we emphasize that, even in these cases, the statistical steady state itself does not depend on initial conditions. Although the outcome of hot-Jupiter circulation models depend on details of the radiative forcing and frictional drag, aspects of which remain uncertain, we conclude that the specification of initial conditions is not a source of uncertainty, at least over the parameter range explored in most current models.

  3. Consistent Initial Conditions for the DNS of Compressible Turbulence

    NASA Technical Reports Server (NTRS)

    Ristorcelli, J. R.; Blaisdell, G. A.

    1996-01-01

    Relationships between diverse thermodynamic quantities appropriate to weakly compressible turbulence are derived. It is shown that for turbulence of a finite turbulent Mach number there is a finite element of compressibility. A methodology for generating initial conditions for the fluctuating pressure, density and dilatational velocity is given which is consistent with finite Mach number effects. Use of these initial conditions gives rise to a smooth development of the flow, in contrast to cases in which these fields are specified arbitrarily or set to zero. Comparisons of the effect of different types of initial conditions are made using direct numerical simulation of decaying isotropic turbulence.

  4. Everlasting effect of initial conditions on single-file diffusion.

    PubMed

    Leibovich, N; Barkai, E

    2013-09-01

    We study the dynamics of a tagged particle in an environment of point Brownian particles with hard-core interactions in an infinite one-dimensional channel (a single-file model). In particular, we examine the influence of initial conditions on the dynamics of the tagged particle. We compare two initial conditions: equal distances between particles and uniform density distribution. The effect is shown by the differences of mean-square-displacement and correlation function for the two ensembles of initial conditions. We discuss the violation of Einstein relation, and its dependence on the initial condition, and the difference between time and ensemble averaging. More specifically, using the Jepsen line, we will discuss how transport coefficients, like diffusivity, depend on the initial state. Our work shows that initial conditions determine the long time limit of the dynamics, and in this sense the system never forgets its initial state in complete contrast with thermal systems (i.e., a closed system that attains equilibrium independent of the initial state).

  5. Accurate and robust registration of high-speed railway viaduct point clouds using closing conditions and external geometric constraints

    NASA Astrophysics Data System (ADS)

    Ji, Zheng; Song, Mengxiao; Guan, Haiyan; Yu, Yongtao

    2015-08-01

    This paper proposes an automatic method for registering multiple laser scans without a control network. The proposed registration method first uses artificial targets to pair-wise register adjacent scans for initial transformation estimates; the proposed registration method then employs combined adjustments with closing conditions and external triangle constraints to globally register all scans along a long-range, high-speed railway corridor. The proposed registration method uses (1) closing conditions to eliminate registration errors that gradually accumulate as the length of a corridor (the number of scan stations) increases, and (2) external geometric constraints to ensure the shape correctness of an elongated high-speed railway. A 640-m high-speed railway viaduct with twenty-one piers is used to conduct experiments using our proposed registration method. A group of comparative experiments is undertaken to evaluate the robustness and efficiency of the proposed registration method to accurately register long-range corridors.

  6. Time Accurate Unsteady Pressure Loads Simulated for the Space Launch System at a Wind Tunnel Condition

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, Bil; Streett, Craig L; Glass, Christopher E.; Schuster, David M.

    2015-01-01

    Using the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics code, an unsteady, time-accurate flow field about a Space Launch System configuration was simulated at a transonic wind tunnel condition (Mach = 0.9). Delayed detached eddy simulation combined with Reynolds Averaged Naiver-Stokes and a Spallart-Almaras turbulence model were employed for the simulation. Second order accurate time evolution scheme was used to simulate the flow field, with a minimum of 0.2 seconds of simulated time to as much as 1.4 seconds. Data was collected at 480 pressure taps at locations, 139 of which matched a 3% wind tunnel model, tested in the Transonic Dynamic Tunnel (TDT) facility at NASA Langley Research Center. Comparisons between computation and experiment showed agreement within 5% in terms of location for peak RMS levels, and 20% for frequency and magnitude of power spectral densities. Grid resolution and time step sensitivity studies were performed to identify methods for improved accuracy comparisons to wind tunnel data. With limited computational resources, accurate trends for reduced vibratory loads on the vehicle were observed. Exploratory methods such as determining minimized computed errors based on CFL number and sub-iterations, as well as evaluating frequency content of the unsteady pressures and evaluation of oscillatory shock structures were used in this study to enhance computational efficiency and solution accuracy. These techniques enabled development of a set of best practices, for the evaluation of future flight vehicle designs in terms of vibratory loads.

  7. Sensitivity of a Simulated Derecho Event to Model Initial Conditions

    NASA Astrophysics Data System (ADS)

    Wang, Wei

    2014-05-01

    Since 2003, the MMM division at NCAR has been experimenting cloud-permitting scale weather forecasting using Weather Research and Forecasting (WRF) model. Over the years, we've tested different model physics, and tried different initial and boundary conditions. Not surprisingly, we found that the model's forecasts are more sensitive to the initial conditions than model physics. In 2012 real-time experiment, WRF-DART (Data Assimilation Research Testbed) at 15 km was employed to produce initial conditions for twice-a-day forecast at 3 km. On June 29, this forecast system captured one of the most destructive derecho event on record. In this presentation, we will examine forecast sensitivity to different model initial conditions, and try to understand the important features that may contribute to the success of the forecast.

  8. Can phenological models predict tree phenology accurately under climate change conditions?

    NASA Astrophysics Data System (ADS)

    Chuine, Isabelle; Bonhomme, Marc; Legave, Jean Michel; García de Cortázar-Atauri, Inaki; Charrier, Guillaume; Lacointe, André; Améglio, Thierry

    2014-05-01

    The onset of the growing season of trees has been globally earlier by 2.3 days/decade during the last 50 years because of global warming and this trend is predicted to continue according to climate forecast. The effect of temperature on plant phenology is however not linear because temperature has a dual effect on bud development. On one hand, low temperatures are necessary to break bud dormancy, and on the other hand higher temperatures are necessary to promote bud cells growth afterwards. Increasing phenological changes in temperate woody species have strong impacts on forest trees distribution and productivity, as well as crops cultivation areas. Accurate predictions of trees phenology are therefore a prerequisite to understand and foresee the impacts of climate change on forests and agrosystems. Different process-based models have been developed in the last two decades to predict the date of budburst or flowering of woody species. They are two main families: (1) one-phase models which consider only the ecodormancy phase and make the assumption that endodormancy is always broken before adequate climatic conditions for cell growth occur; and (2) two-phase models which consider both the endodormancy and ecodormancy phases and predict a date of dormancy break which varies from year to year. So far, one-phase models have been able to predict accurately tree bud break and flowering under historical climate. However, because they do not consider what happens prior to ecodormancy, and especially the possible negative effect of winter temperature warming on dormancy break, it seems unlikely that they can provide accurate predictions in future climate conditions. It is indeed well known that a lack of low temperature results in abnormal pattern of bud break and development in temperate fruit trees. An accurate modelling of the dormancy break date has thus become a major issue in phenology modelling. Two-phases phenological models predict that global warming should delay

  9. Possibilistic-clustering-based MR brain image segmentation with accurate initialization

    NASA Astrophysics Data System (ADS)

    Liao, Qingmin; Deng, Yingying; Dou, Weibei; Ruan, Su; Bloyet, Daniel

    2004-01-01

    Magnetic resonance image analysis by computer is useful to aid diagnosis of malady. We present in this paper a automatic segmentation method for principal brain tissues. It is based on the possibilistic clustering approach, which is an improved fuzzy c-means clustering method. In order to improve the efficiency of clustering process, the initial value problem is discussed and solved by combining with a histogram analysis method. Our method can automatically determine number of classes to cluster and the initial values for each class. It has been tested on a set of forty MR brain images with or without the presence of tumor. The experimental results showed that it is simple, rapid and robust to segment the principal brain tissues.

  10. Third-order accurate entropy-stable schemes for initial-boundary-value conservation laws

    NASA Astrophysics Data System (ADS)

    Svärd, Magnus

    2012-08-01

    We consider initial-boundary-value conservation laws with the objective to obtain high-order approximations. We study two different approaches to obtain third-order accuracy, local entropy stability and a global bound on the entropy. The results are applicable to, for example the Euler equations of gas dynamics, for which we present numerical results demonstrating the robustness and accuracy of the scheme.

  11. Analysis of the effect of initial conditions on the initial development of a turbulent jet

    NASA Technical Reports Server (NTRS)

    Kim, Soong KI; Chung, Myung Kyoon; Cho, Ji Ryong

    1992-01-01

    The effect of the initial condition at the jet exit on the downstream evolution, particularly within the potential core length, were numerically investigated as well as with available experimental data. In order to select the most dependable computational model for the present numerical experiment, a comparative study has been performed with different turbulence models at k-epsilon level, and it was found that the k-epsilon-gammma model yields superior prediction accuracy over other conventional models. The calculated results show that the potential core length and the spreading rate the initial mixing layer are dependent on the initial length scale as well as the turbulent kinetic energy at the jet exit. Such effect of the initial length scale increases with higher initial turbulence level. An empirical parameter has been devised to collapse the calculated data of the potential core length and the spreading rate with various initial conditions onto a single curve.

  12. Accurate and Fast Convergent Initial-Value Belief Propagation for Stereo Matching.

    PubMed

    Wang, Xiaofeng; Liu, Yiguang

    2015-01-01

    The belief propagation (BP) algorithm has some limitations, including ambiguous edges and textureless regions, and slow convergence speed. To address these problems, we present a novel algorithm that intrinsically improves both the accuracy and the convergence speed of BP. First, traditional BP generally consumes time due to numerous iterations. To reduce the number of iterations, inspired by the crucial importance of the initial value in nonlinear problems, a novel initial-value belief propagation (IVBP) algorithm is presented, which can greatly improve both convergence speed and accuracy. Second, .the majority of the existing research on BP concentrates on the smoothness term or other energy terms, neglecting the significance of the data term. In this study, a self-adapting dissimilarity data term (SDDT) is presented to improve the accuracy of the data term, which incorporates an additional gradient-based measure into the traditional data term, with the weight determined by the robust measure-based control function. Finally, this study explores the effective combination of local methods and global methods. The experimental results have demonstrated that our method performs well compared with the state-of-the-art BP and simultaneously holds better edge-preserving smoothing effects with fast convergence speed in the Middlebury and new 2014 Middlebury datasets. PMID:26349063

  13. Accurate determination of fiber water-retaining capability at process conditions by headspace gas chromatography.

    PubMed

    Zhang, Shu-Xin; Chai, Xin-Sheng; He, Liang

    2016-09-16

    This work reports on a method for the accurate determination of fiber water-retaining capability at process conditions by headspace gas chromatography (HS-GC) method. The method was based the HS-GC measurement of water vapor on a set closed vials containing in a given amount pulp with different amounts of water addition, from under-saturation to over-saturation. By plotting the equilibrated water vapor signal vs. the amount of water added in pulp, two different trend lines can be observed, in which the transition of the lines corresponds to fiber water-retaining capability. The results showed that the HS-GC method has good measurement precision (much better than the reference method) and good accuracy. The present method can be also used for determining pulp fiber water-retaining capability at the process temperatures in both laboratory research and mill applications. PMID:27554029

  14. Initial conditions and Korteweg-de Vries solitons

    NASA Technical Reports Server (NTRS)

    Weidman, P. D.; Redekopp, L. G.

    1982-01-01

    The effects of rectangular initial data on the evolution of solitons governed by the Korteweg-de Vries equation is studied. Both isolated and separated disturbances are considered, providing some general insight into how the nature of the initial condition influences the appearance of solitons in the asymptotic state. The analytic approach is based on the inverse scattering transform which relates the initial condition to Schroedinger's equation. The results are used to model the initial shallow-water disturbances, and the results can be summarized by stating that the number of evolved solitons depends on the strength of each rectangular disturbance, the relative amplitudes of the rectangular disturbances, and the relative proximity of the disturbances.

  15. Nurse initiated thrombolysis in the accident and emergency department: safe, accurate, and faster than fast track

    PubMed Central

    Heath, S; Bain, R; Andrews, A; Chida, S; Kitchen, S; Walters, M

    2003-01-01

    Objective: To reduce the time between arrival at hospital of a patient with acute myocardial infarction and administration of thrombolytic therapy (door to needle time) by the introduction of nurse initiated thrombolysis in the accident and emergency department. Methods: Two acute chest pain nurse specialists (ACPNS) based in A&E for 62.5 hours of the week were responsible for initiating thrombolysis in the A&E department. The service reverts to a "fast track" system outside of these hours, with the on call medical team prescribing thrombolysis on the coronary care unit. Prospectively gathered data were analysed for a nine month period and a head to head comparison made between the mean and median door to needle times for both systems of thrombolysis delivery. Results: Data from 91 patients were analysed; 43 (47%) were thrombolysed in A&E by the ACPNS and 48 (53%) were thrombolysed in the coronary care unit by the on call medical team. The ACPNS achieved a median door to needle time of 23 minutes (IQR=17 to 32) compared with 56 minutes (IQR=34 to 79.5) for the fast track. The proportion of patients thrombolysed in 30 minutes by the ACPNS and fast track system was 72% (31 of 43) and 21% (10 of 48) respectively (difference=51%, 95% confidence intervals 34% to 69%, p<0.05). Conclusion: Diagnosis of acute myocardial infarction and administration of thrombolysis by experienced cardiology nurses in A&E is a safe and effective strategy for reducing door to needle times, even when compared with a conventional fast track system. PMID:12954678

  16. Successional stage of biological soil crusts: an accurate indicator of ecohydrological condition

    USGS Publications Warehouse

    Belnap, Jayne; Wilcox, Bradford P.; Van Scoyoc, Matthew V.; Phillips, Susan L.

    2013-01-01

    Biological soil crusts are a key component of many dryland ecosystems. Following disturbance, biological soil crusts will recover in stages. Recently, a simple classification of these stages has been developed, largely on the basis of external features of the crusts, which reflects their level of development (LOD). The classification system has six LOD classes, from low (1) to high (6). To determine whether the LOD of a crust is related to its ecohydrological function, we used rainfall simulation to evaluate differences in infiltration, runoff, and erosion among crusts in the various LODs, across a range of soil depths and with different wetting pre-treatments. We found large differences between the lowest and highest LODs, with runoff and erosion being greatest from the lowest LOD. Under dry antecedent conditions, about 50% of the water applied ran off the lowest LOD plots, whereas less than 10% ran off the plots of the two highest LODs. Similarly, sediment loss was 400 g m-2 from the lowest LOD and almost zero from the higher LODs. We scaled up the results from these simulations using the Rangeland Hydrology and Erosion Model. Modelling results indicate that erosion increases dramatically as slope length and gradient increase, especially beyond the threshold values of 10 m for slope length and 10% for slope gradient. Our findings confirm that the LOD classification is a quick, easy, nondestructive, and accurate index of hydrological condition and should be incorporated in field and modelling assessments of ecosystem health.

  17. Effects of initial conditions on the development of curved wakes

    NASA Technical Reports Server (NTRS)

    Weygandt, James H.; Mehta, Rabindra D.

    1993-01-01

    An experimental investigation has been conducted on the three-dimensional structure of curved plane wakes developing from tripped and untripped initial boundary layers. The effects of mild stream-wise curvature on a wake generated at the trailing edge of a slowly tapering splitter plate were investigated at a Reynolds number of about 30,000. With the initial boundary layers turbulent, spatially-stationary streamwise vorticity was not observed. The curvature affected the wake growth and defect-decay rates, but in different ways for each of the two initial conditions. The effects of curvature were also apparent in the Reynolds stress results, especially in the primary shear stress distributions, which showed that the levels on the unstable side were increased significantly compared to those for a straight wake, while those on the stable side were decreased, with the effect stronger in the initially laminar wake.

  18. CMB quadrupole suppression. I. Initial conditions of inflationary perturbations

    SciTech Connect

    Boyanovsky, D.; Vega, H. J. de; Sanchez, N. G.

    2006-12-15

    We investigate the issue of initial conditions of curvature and tensor perturbations at the beginning of slow roll inflation and their effect on the power spectra. Renormalizability and small backreaction constrain the high k behavior of the Bogoliubov coefficients that define these initial conditions. We introduce a transfer function D(k) which encodes the effect of generic initial conditions on the power spectra. The constraint from renormalizability and small backreaction entails that D(k)(less-or-similar sign){mu}{sup 2}/k{sup 2} for large k, implying that observable effects from initial conditions are more prominent in the low multipoles. This behavior affects the CMB quadrupole by the observed amount {approx}10%-20% when {mu} is of the order of the energy scale of inflation. The effects on high l-multipoles are suppressed by a factor {approx}1/l{sup 2} due to the falloff of D(k) for large wave vectors k. We show that the determination of generic initial conditions for the fluctuations is equivalent to the scattering problem by a potential V({eta}) localized just prior to the slow roll stage. Such potential leads to a transfer function D(k) which automatically obeys the renormalizability and small backreaction constraints. We find that an attractive potential V({eta}) yields a suppression of the lower CMB multipoles. Both for curvature and tensor modes, the quadrupole suppression depends only on the energy scale of V({eta}), and on the time interval where V({eta}) is nonzero. A suppression of the quadrupole for curvature perturbations consistent with the data is obtained when the scale of the potential is of the order of k{sub Q}{sup 2} where k{sub Q} is the wave vector whose physical wavelength is the Hubble radius today.

  19. Time-Accurate Unsteady Pressure Loads Simulated for the Space Launch System at Wind Tunnel Conditions

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, William L.; Glass, Christopher E.; Streett, Craig L.; Schuster, David M.

    2015-01-01

    A transonic flow field about a Space Launch System (SLS) configuration was simulated with the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics (CFD) code at wind tunnel conditions. Unsteady, time-accurate computations were performed using second-order Delayed Detached Eddy Simulation (DDES) for up to 1.5 physical seconds. The surface pressure time history was collected at 619 locations, 169 of which matched locations on a 2.5 percent wind tunnel model that was tested in the 11 ft. x 11 ft. test section of the NASA Ames Research Center's Unitary Plan Wind Tunnel. Comparisons between computation and experiment showed that the peak surface pressure RMS level occurs behind the forward attach hardware, and good agreement for frequency and power was obtained in this region. Computational domain, grid resolution, and time step sensitivity studies were performed. These included an investigation of pseudo-time sub-iteration convergence. Using these sensitivity studies and experimental data comparisons, a set of best practices to date have been established for FUN3D simulations for SLS launch vehicle analysis. To the author's knowledge, this is the first time DDES has been used in a systematic approach and establish simulation time needed, to analyze unsteady pressure loads on a space launch vehicle such as the NASA SLS.

  20. Conditional mutual inclusive information enables accurate quantification of associations in gene regulatory networks.

    PubMed

    Zhang, Xiujun; Zhao, Juan; Hao, Jin-Kao; Zhao, Xing-Ming; Chen, Luonan

    2015-03-11

    Mutual information (MI), a quantity describing the nonlinear dependence between two random variables, has been widely used to construct gene regulatory networks (GRNs). Despite its good performance, MI cannot separate the direct regulations from indirect ones among genes. Although the conditional mutual information (CMI) is able to identify the direct regulations, it generally underestimates the regulation strength, i.e. it may result in false negatives when inferring gene regulations. In this work, to overcome the problems, we propose a novel concept, namely conditional mutual inclusive information (CMI2), to describe the regulations between genes. Furthermore, with CMI2, we develop a new approach, namely CMI2NI (CMI2-based network inference), for reverse-engineering GRNs. In CMI2NI, CMI2 is used to quantify the mutual information between two genes given a third one through calculating the Kullback-Leibler divergence between the postulated distributions of including and excluding the edge between the two genes. The benchmark results on the GRNs from DREAM challenge as well as the SOS DNA repair network in Escherichia coli demonstrate the superior performance of CMI2NI. Specifically, even for gene expression data with small sample size, CMI2NI can not only infer the correct topology of the regulation networks but also accurately quantify the regulation strength between genes. As a case study, CMI2NI was also used to reconstruct cancer-specific GRNs using gene expression data from The Cancer Genome Atlas (TCGA). CMI2NI is freely accessible at http://www.comp-sysbio.org/cmi2ni.

  1. Theory of coherent resonance energy transfer for coherent initial condition.

    PubMed

    Jang, Seogjoo

    2009-10-28

    A theory of coherent resonance energy transfer [Jang et al., J. Chem. Phys. 129, 101104 (2008)] is extended for coherent initial condition. For the situation where the initial excitation is an arbitrary linear combination of donor and acceptor excitations, a second order time local quantum master equation combined with polaron transformation is derived. Inhomogeneous terms in the resulting equation have contributions not only from initial donor and acceptor populations but also from their coherence terms. Numerical tests are performed for general super Ohmic spectral density where the bath degrees of freedom coupled to donor and acceptor can be correlated with each other. Calculation results demonstrate sensitivity of early nonstationary population dynamics on the relative sign of initial donor and acceptor excitation states. It is shown that contribution of inhomogeneous terms is more significant for coherent initial condition than for localized one. The overall model calculations provide details of the interplay between quantum coherence and nonequilibrium/non-Markovian effects in the time dependent donor population dynamics.

  2. Initial conditions for reconnection calculations of quantized vortices

    NASA Astrophysics Data System (ADS)

    Rorai, Cecilia; Lathrop, Daniel P.; Fisher, Michael E.; Sreenivasan, Katepalli R.

    2010-11-01

    Vortex reconnection occurs when two vortices intersect and then rejoin with exchanged tails. This process occurs in both classical fluids and superfluids, in superconductors, and in magnetized plasmas. In helium II this phenomenon has been investigated numerically via the Gross-Pitaevskii equation. Although a simplified model, the Gross-Pitaevskii equation is interesting since it naturally embodies vortex reconnection, as first numerically shown by Koplik & Levine [Phys. Rev. Lett. 71, 1375 (1993)]. A crucial issue in such computations is the selection of initial conditions. The question we address is how initial wave functions may effect the outcome of reconnection. Traditionally the initial conditions have been generated by multiplying approximate wave functions for a single vortex and imposing, to some degree, periodic boundary conditions. An alternative approach will be presented. It consists in selecting an initial configuration that minimizes the total energy. The differences between the results obtained with this approach and previous ones will be discussed especially with respect to the dispersion of energy seen in quantum turbulence.

  3. Initial conditions of inhomogeneous universe and the cosmological constant problem

    NASA Astrophysics Data System (ADS)

    Totani, Tomonori

    2016-06-01

    Deriving the Einstein field equations (EFE) with matter fluid from the action principle is not straightforward, because mass conservation must be added as an additional constraint to make rest-frame mass density variable in reaction to metric variation. This can be avoided by introducing a constraint 0δ(√-g) = to metric variations δ gμν, and then the cosmological constant Λ emerges as an integration constant. This is a removal of one of the four constraints on initial conditions forced by EFE at the birth of the universe, and it may imply that EFE are unnecessarily restrictive about initial conditions. I then adopt a principle that the theory of gravity should be able to solve time evolution starting from arbitrary inhomogeneous initial conditions about spacetime and matter. The equations of gravitational fields satisfying this principle are obtained, by setting four auxiliary constraints on δ gμν to extract six degrees of freedom for gravity. The cost of achieving this is a loss of general covariance, but these equations constitute a consistent theory if they hold in the special coordinate systems that can be uniquely specified with respect to the initial space-like hypersurface when the universe was born. This theory predicts that gravity is described by EFE with non-zero Λ in a homogeneous patch of the universe created by inflation, but Λ changes continuously across different patches. Then both the smallness and coincidence problems of the cosmological constant are solved by the anthropic argument. This is just a result of inhomogeneous initial conditions, not requiring any change of the fundamental physical laws in different patches.

  4. Initial conditions of inhomogeneous universe and the cosmological constant problem

    NASA Astrophysics Data System (ADS)

    Totani, Tomonori

    2016-06-01

    Deriving the Einstein field equations (EFE) with matter fluid from the action principle is not straightforward, because mass conservation must be added as an additional constraint to make rest-frame mass density variable in reaction to metric variation. This can be avoided by introducing a constraint 0δ(√‑g) = to metric variations δ gμν, and then the cosmological constant Λ emerges as an integration constant. This is a removal of one of the four constraints on initial conditions forced by EFE at the birth of the universe, and it may imply that EFE are unnecessarily restrictive about initial conditions. I then adopt a principle that the theory of gravity should be able to solve time evolution starting from arbitrary inhomogeneous initial conditions about spacetime and matter. The equations of gravitational fields satisfying this principle are obtained, by setting four auxiliary constraints on δ gμν to extract six degrees of freedom for gravity. The cost of achieving this is a loss of general covariance, but these equations constitute a consistent theory if they hold in the special coordinate systems that can be uniquely specified with respect to the initial space-like hypersurface when the universe was born. This theory predicts that gravity is described by EFE with non-zero Λ in a homogeneous patch of the universe created by inflation, but Λ changes continuously across different patches. Then both the smallness and coincidence problems of the cosmological constant are solved by the anthropic argument. This is just a result of inhomogeneous initial conditions, not requiring any change of the fundamental physical laws in different patches.

  5. Numerical parameter constraints for accurate PIC-DSMC simulation of breakdown from arc initiation to stable arcs

    NASA Astrophysics Data System (ADS)

    Moore, Christopher; Hopkins, Matthew; Moore, Stan; Boerner, Jeremiah; Cartwright, Keith

    2015-09-01

    Simulation of breakdown is important for understanding and designing a variety of applications such as mitigating undesirable discharge events. Such simulations need to be accurate through early time arc initiation to late time stable arc behavior. Here we examine constraints on the timestep and mesh size required for arc simulations using the particle-in-cell (PIC) method with direct simulation Monte Carlo (DMSC) collisions. Accurate simulation of electron avalanche across a fixed voltage drop and constant neutral density (reduced field of 1000 Td) was found to require a timestep ~ 1/100 of the mean time between collisions and a mesh size ~ 1/25 the mean free path. These constraints are much smaller than the typical PIC-DSMC requirements for timestep and mesh size. Both constraints are related to the fact that charged particles are accelerated by the external field. Thus gradients in the electron energy distribution function can exist at scales smaller than the mean free path and these must be resolved by the mesh size for accurate collision rates. Additionally, the timestep must be small enough that the particle energy change due to the fields be small in order to capture gradients in the cross sections versus energy. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  6. Accurate First-Principles Spectra Predictions for Planetological and Astrophysical Applications at Various T-Conditions

    NASA Astrophysics Data System (ADS)

    Rey, M.; Nikitin, A. V.; Tyuterev, V.

    2014-06-01

    Knowledge of near infrared intensities of rovibrational transitions of polyatomic molecules is essential for the modeling of various planetary atmospheres, brown dwarfs and for other astrophysical applications 1,2,3. For example, to analyze exoplanets, atmospheric models have been developed, thus making the need to provide accurate spectroscopic data. Consequently, the spectral characterization of such planetary objects relies on the necessity of having adequate and reliable molecular data in extreme conditions (temperature, optical path length, pressure). On the other hand, in the modeling of astrophysical opacities, millions of lines are generally involved and the line-by-line extraction is clearly not feasible in laboratory measurements. It is thus suggested that this large amount of data could be interpreted only by reliable theoretical predictions. There exists essentially two theoretical approaches for the computation and prediction of spectra. The first one is based on empirically-fitted effective spectroscopic models. Another way for computing energies, line positions and intensities is based on global variational calculations using ab initio surfaces. They do not yet reach the spectroscopic accuracy stricto sensu but implicitly account for all intramolecular interactions including resonance couplings in a wide spectral range. The final aim of this work is to provide reliable predictions which could be quantitatively accurate with respect to the precision of available observations and as complete as possible. All this thus requires extensive first-principles quantum mechanical calculations essentially based on three necessary ingredients which are (i) accurate intramolecular potential energy surface and dipole moment surface components well-defined in a large range of vibrational displacements and (ii) efficient computational methods combined with suitable choices of coordinates to account for molecular symmetry properties and to achieve a good numerical

  7. Lifting the Curtain on the Conditions of Sexual Initiation among Youth in Ethiopia

    PubMed Central

    Lindstrom, David P.; Hattori, Megan Klein; Belachew, Tefera; Tessema, Fasil

    2012-01-01

    Purpose Deriving accurate estimates of the level of sexual coercion is challenging because of the stigma that is attached to the experience. This study examines the effectiveness of a nonverbal response card method to reduce social desirability bias in reports of the conditions of sexual initiation among youth in southwestern Ethiopia. Methods The conditions surrounding sexual initiation are examined using data from a pilot survey and a final survey of youth aged 13 to 24. Half of the respondents in each survey were randomly assigned to a nonverbal response card method for sensitive questions on sexual attitudes and behavior, and the other half of the respondents were assigned to a control group that provided verbal responses. Responses for the two groups to questions regarding the conditions of sexual initiation are compared. Results Respondents who used the nonverbal response card were more likely to report pressure from friends or a partner, having sex for money or another gain, and rape as conditions of sexual initiation than respondents who provided verbal responses. Among sexually experienced youth, 29.3% of respondents who used the card method reported some form of coercion during sexual initiation compared to 19.4% of respondents who gave verbal responses. Conclusions The nonverbal response card provides an effective method for reducing social desirability bias when soliciting responses to sensitive questions in the context of an interviewer-administered survey. The analysis also suggests that coerced sexual initiation is underreported by youth in interviewer-administered surveys that use conventional verbal responses. PMID:22626489

  8. The Initial Physical Conditions of Kepler-36 b and c

    NASA Astrophysics Data System (ADS)

    Owen, James E.; Morton, Timothy. D.

    2016-03-01

    The Kepler-36 planetary system consists of two exoplanets at similar separations (0.115 and 0.128 au), which have dramatically different densities. The inner planet has a density consistent with an Earth-like composition, while the outer planet is extremely low density, such that it must contain a voluminous H/He envelope. Such a density difference would pose a problem for any formation mechanism if their current densities were representative of their composition at formation. However, both planets are at close enough separations to have undergone significant evaporation in the past. We constrain the core mass, core composition, initial envelope mass, and initial cooling time of each planet using evaporation models conditioned on their present-day masses and radii, as inferred from Kepler photometry and transit timing analysis. The inner planet is consistent with being an evaporatively stripped core, while the outer planet has retained some of its initial envelope due to its higher core mass. Therefore, both planets could have had a similar formation pathway, with the inner planet having an initial envelope-mass fraction of ≲10% and core mass of ˜4.4 M⊕, while the outer had an initial envelope-mass fraction of the order of 15%-30% and core mass ˜7.3 M⊕. Finally, our results indicate that the outer planet had a long (≳30 Myr) initial cooling time, much longer than would naively be predicted from simple timescale arguments. The long initial cooling time could be evidence for a dramatic early cooling episode such as the recently proposed “boil-off” process.

  9. Can Impacts of Climate Change and Agricultural Adaptation Strategies Be Accurately Quantified if Crop Models Are Annually Re-Initialized?

    PubMed Central

    Basso, Bruno; Hyndman, David W.; Kendall, Anthony D.; Grace, Peter R.; Robertson, G. Philip

    2015-01-01

    Estimates of climate change impacts on global food production are generally based on statistical or process-based models. Process-based models can provide robust predictions of agricultural yield responses to changing climate and management. However, applications of these models often suffer from bias due to the common practice of re-initializing soil conditions to the same state for each year of the forecast period. If simulations neglect to include year-to-year changes in initial soil conditions and water content related to agronomic management, adaptation and mitigation strategies designed to maintain stable yields under climate change cannot be properly evaluated. We apply a process-based crop system model that avoids re-initialization bias to demonstrate the importance of simulating both year-to-year and cumulative changes in pre-season soil carbon, nutrient, and water availability. Results are contrasted with simulations using annual re-initialization, and differences are striking. We then demonstrate the potential for the most likely adaptation strategy to offset climate change impacts on yields using continuous simulations through the end of the 21st century. Simulations that annually re-initialize pre-season soil carbon and water contents introduce an inappropriate yield bias that obscures the potential for agricultural management to ameliorate the deleterious effects of rising temperatures and greater rainfall variability. PMID:26043188

  10. Can Impacts of Climate Change and Agricultural Adaptation Strategies Be Accurately Quantified if Crop Models Are Annually Re-Initialized?

    PubMed

    Basso, Bruno; Hyndman, David W; Kendall, Anthony D; Grace, Peter R; Robertson, G Philip

    2015-01-01

    Estimates of climate change impacts on global food production are generally based on statistical or process-based models. Process-based models can provide robust predictions of agricultural yield responses to changing climate and management. However, applications of these models often suffer from bias due to the common practice of re-initializing soil conditions to the same state for each year of the forecast period. If simulations neglect to include year-to-year changes in initial soil conditions and water content related to agronomic management, adaptation and mitigation strategies designed to maintain stable yields under climate change cannot be properly evaluated. We apply a process-based crop system model that avoids re-initialization bias to demonstrate the importance of simulating both year-to-year and cumulative changes in pre-season soil carbon, nutrient, and water availability. Results are contrasted with simulations using annual re-initialization, and differences are striking. We then demonstrate the potential for the most likely adaptation strategy to offset climate change impacts on yields using continuous simulations through the end of the 21st century. Simulations that annually re-initialize pre-season soil carbon and water contents introduce an inappropriate yield bias that obscures the potential for agricultural management to ameliorate the deleterious effects of rising temperatures and greater rainfall variability.

  11. Definition of boundary and initial conditions in the analysis of saturated ground-water flow systems - An introduction

    USGS Publications Warehouse

    Franke, O. Lehn; Reilly, Thomas E.; Bennett, Gordon D.

    1987-01-01

    Accurate definition of boundary and initial conditions is an essential part of conceptualizing and modeling ground-water flow systems. This report describes the properties of the seven most common boundary conditions encountered in ground-water systems and discusses major aspects of their application. It also discusses the significance and specification of initial conditions and evaluates some common errors in applying this concept to ground-water-system models. An appendix is included that discusses what the solution of a differential equation represents and how the solution relates to the boundary conditions defining the specific problem. This report considers only boundary conditions that apply to saturated ground-water systems.

  12. Stochastic bias from non-Gaussian initial conditions

    SciTech Connect

    Baumann, Daniel; Ferraro, Simone; Smith, Kendrick M.; Green, Daniel E-mail: sferraro@princeton.edu E-mail: kmsmith@astro.princeton.edu

    2013-05-01

    In this article, we show that a stochastic form of scale-dependent halo bias arises in multi-source inflationary models, where multiple fields determine the initial curvature perturbation. We derive this effect for general non-Gaussian initial conditions and study various examples, such as curvaton models and quasi-single field inflation. We present a general formula for both the stochastic and the non-stochastic parts of the halo bias, in terms of the N-point cumulants of the curvature perturbation at the end of inflation. At lowest order, the stochasticity arises if the collapsed limit of the four-point function is boosted relative to the square of the three-point function in the squeezed limit. We derive all our results in two ways, using the barrier crossing formalism and the peak-background split method. In a companion paper [1], we prove that these two approaches are mathematically equivalent.

  13. Sensitivity of a Wave Structure to Initial Conditions

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.; Duval, Walter M. B. (Technical Monitor)

    2000-01-01

    Microgravity experiments aimed at quantifying effects of gentler via controlled sinusoidal forcing transmitted on the interface between two miscible liquids have shown the evolution of a quasi -stationary four-mode wave structure oriented vertically. The sensitivity of the wave structure to phase angle variation is investigated computationally. We show that a slight variation of the phase angle is sufficient to cause a bifurcation to a two-mode structure. The dependence of phase angle on wave structure is attributed to sensitivity on initial conditions due to the strong nonlinearity of the coupled field equations for the parametric space of interest.

  14. Generating Optimal Initial Conditions for Smoothed Particle Hydrodynamics Simulations

    NASA Astrophysics Data System (ADS)

    Diehl, S.; Rockefeller, G.; Fryer, C. L.; Riethmiller, D.; Statler, T. S.

    2015-12-01

    We review existing smoothed particle hydrodynamics setup methods and outline their advantages, limitations, and drawbacks. We present a new method for constructing initial conditions for smoothed particle hydrodynamics simulations, which may also be of interest for N-body simulations, and demonstrate this method on a number of applications. This new method is inspired by adaptive binning techniques using weighted Voronoi tessellations. Particles are placed and iteratively moved based on their proximity to neighbouring particles and the desired spatial resolution. This new method can satisfy arbitrarily complex spatial resolution requirements.

  15. Generating optimal initial conditions for smooth particle hydrodynamics (SPH) simulations

    SciTech Connect

    Diehl, Steven; Rockefeller, Gabriel M; Fryer, Christopher L

    2008-01-01

    We present a new optimal method to set up initial conditions for Smooth Particle Hydrodynamics Simulations, which may also be of interest for N-body simulations. This new method is based on weighted Voronoi tesselations (WVTs) and can meet arbitrarily complex spatial resolution requirements. We conduct a comprehensive review of existing SPH setup methods, and outline their advantages, limitations and drawbacks. A serial version of our WVT setup method is publicly available and we give detailed instruction on how to easily implement the new method on top of an existing parallel SPH code.

  16. Single-file diffusion with non-thermal initial conditions

    NASA Astrophysics Data System (ADS)

    Lizana, Ludvig; Lomholt, Michael A.; Ambjörnsson, Tobias

    2014-02-01

    Single-file diffusion is a theoretically challenging many-body problem where the calculation of even the simplest observables, e.g. mean square displacement, for a tracer particle requires an elaborate mathematical machinery. There is therefore a need for simple approaches which provide intuitive understandings and predict qualitatively correct behaviours. Here we put forward a scaling-type method which we use to investigate the influence of non-thermal initial conditions on the dynamics of a tracer particle. With our new approach we reproduce, up to scaling, several known long and short time asymptotic results for the tracer particle mean square displacement.

  17. Analysis of translation initiation during stress conditions by polysome profiling.

    PubMed

    Coudert, Laëtitia; Adjibade, Pauline; Mazroui, Rachid

    2014-01-01

    Precise control of mRNA translation is fundamental for eukaryotic cell homeostasis, particularly in response to physiological and pathological stress. Alterations of this program can lead to the growth of damaged cells, a hallmark of cancer development, or to premature cell death such as seen in neurodegenerative diseases. Much of what is known concerning the molecular basis for translational control has been obtained from polysome analysis using a density gradient fractionation system. This technique relies on ultracentrifugation of cytoplasmic extracts on a linear sucrose gradient. Once the spin is completed, the system allows fractionation and quantification of centrifuged zones corresponding to different translating ribosomes populations, thus resulting in a polysome profile. Changes in the polysome profile are indicative of changes or defects in translation initiation that occur in response to various types of stress. This technique also allows to assess the role of specific proteins on translation initiation, and to measure translational activity of specific mRNAs. Here we describe our protocol to perform polysome profiles in order to assess translation initiation of eukaryotic cells and tissues under either normal or stress growth conditions.

  18. Automatic pose initialization for accurate 2D/3D registration applied to abdominal aortic aneurysm endovascular repair

    NASA Astrophysics Data System (ADS)

    Miao, Shun; Lucas, Joseph; Liao, Rui

    2012-02-01

    Minimally invasive abdominal aortic aneurysm (AAA) stenting can be greatly facilitated by overlaying the preoperative 3-D model of the abdominal aorta onto the intra-operative 2-D X-ray images. Accurate 2-D/3-D registration in 3-D space makes the 2-D/3-D overlay robust to the change of C-Arm angulations. By far, the 2-D/3-D registration methods based on simulated X-ray projection images using multiple image planes have been shown to be able to provide satisfactory 3-D registration accuracy. However, one drawback of the intensity-based 2-D/3-D registration methods is that the similarity measure is usually highly non-convex and hence the optimizer can easily be trapped into local minima. User interaction therefore is often needed in the initialization of the position of the 3-D model in order to get a successful 2-D/3-D registration. In this paper, a novel 3-D pose initialization technique is proposed, as an extension of our previously proposed bi-plane 2-D/3-D registration method for AAA intervention [4]. The proposed method detects vessel bifurcation points and spine centerline in both 2-D and 3-D images, and utilizes landmark information to bring the 3-D volume into a 15mm capture range. The proposed landmark detection method was validated on real dataset, and is shown to be able to provide a good initialization for 2-D/3-D registration in [4], thus making the workflow fully automatic.

  19. Spectator field dynamics in de Sitter and curvaton initial conditions

    SciTech Connect

    Enqvist, Kari; Lerner, Rose N.; Taanila, Olli; Tranberg, Anders E-mail: rose.lerner@helsinki.fi E-mail: antranbe@nbi.dk

    2012-10-01

    We investigate the stochastic behaviour of long wavelength modes of light spectator scalar fields during inflation. When starting from a classical field value, the probability distribution for the spectator both spreads out and moves towards an equilibrium distribution. We study the timescales for a mixed quadratic and quartic potential. The timescale of equilibration depends on the parameters of the model, and can be surprisingly large, more than thousands of e-folds for the majority of light spectators. These results imply that the initial conditions for spectator fields are not automatically erased during inflation. These general results can be used to determine the probability of the value of the zero-mode inside a Universe-sized patch, which is relevant for observations. As an example, we apply the results to the curvaton model to calculate the probability distribution of the curvature perturbation and discuss 'typical' Universes.

  20. Initial conditions for anisotropic extended-type inflationary universes

    SciTech Connect

    del Campo, S. )

    1992-05-15

    Recently, extended-type inflationary universe models have been proposed as an appealing approach for solving most of the cosmological puzzles'' that, in contrast with previous models, do not require a fine-tuning'' for the microphysical parameters present in the effective potential. These scenarios rest on a Brans-Dicke-type theory, where a nonminimal coupling of the form {ital f}({ital cphi}){ital R} is assumed, and it may or may not include a potential for the Brans-Dicke field. In its classical description, different extended inflationary universe scenarios are described, where anisotropy is taken into account. By using the Hartle-Hawking and the Vilenkin boundary conditions for the wave function of the Universe, the probability distributions for the initial states of these extended models in the case of a small anisotropy are determined and discussed.

  1. Mean maps for cosmic web structures in cosmological initial conditions

    NASA Astrophysics Data System (ADS)

    Aung, Han; Cohn, J. D.

    2016-02-01

    Haloes, filaments, sheets and voids in the cosmic web can be defined in terms of the eigenvalues of the smoothed shear tensor and a threshold λth. Using analytic methods, we construct mean maps centred on these types of structures for Gaussian random fields corresponding to cosmological initial conditions. Each map also requires a choice of shear at the origin; we consider three possibilities. We find characteristic sizes, shapes and other properties of the central objects in these mean maps and explore how these properties change with varying the threshold and smoothing scale, i.e. varying the separation of the cosmic web into different kinds of components. The mean maps become increasingly complex as the threshold λth decreases to zero. We also describe scatter around these mean maps, subtleties which can arise in their construction, and some comparisons between haloes in the maps and collapsed haloes at final times.

  2. Longitudinal hydrodynamics from event-by-event Landau initial conditions

    SciTech Connect

    Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read, Kenneth; Wong, Cheuk-Yin

    2015-02-02

    Here we investigate three-dimensional ideal hydrodynamic evolution, with Landau initial conditions, incorporating event-by-event variation with many events and transverse density inhomogeneities. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of θ (20%-30%) expected at freeze-out for most scenarios. Moreover, the deviation from boost invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, hydrodynamics where boost invariance holds at midrapidity is inadequate to extract transport coefficients of the quark-gluon plasma. We conclude by arguing that developing experimental probes of boost invariance is necessary, and suggest some promising directions in this regard.

  3. Longitudinal hydrodynamics from event-by-event Landau initial conditions

    DOE PAGES

    Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read, Kenneth; Wong, Cheuk-Yin

    2015-02-02

    Here we investigate three-dimensional ideal hydrodynamic evolution, with Landau initial conditions, incorporating event-by-event variation with many events and transverse density inhomogeneities. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of θ (20%-30%) expected at freeze-out for most scenarios. Moreover, the deviation from boost invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, hydrodynamics where boost invariance holds at midrapidity ismore » inadequate to extract transport coefficients of the quark-gluon plasma. We conclude by arguing that developing experimental probes of boost invariance is necessary, and suggest some promising directions in this regard.« less

  4. Initial conditions of a simple passive-dynamic walker

    NASA Astrophysics Data System (ADS)

    Haueisen, Brooke; Hudas, Greg; Hulbert, Greg; Nebel, Kyle

    2006-05-01

    Walking robots hold great potential for the future of military robotics. Their natural agility in rough, unstructured terrain make them ideal for military applications but their power requirements do not. Passive dynamic walkers offer a potentially low-power solution. This class of legged robots utilize the natural inverted pendular dynamics that humans rely on to locomote. The most basic of these systems uses gravity as its power source and has no control system therefore its stability is heavily reliant on its initial conditions. The VICON Motion Capture System was used to record the motions of Coleman and Ruina's1 TinkertoyWalker. The initial angles and angular velocities of the various trials were extracted from the motion capture data and used as inputs to a multi-body dynamics model of the walker. The model was created to provide insight into passive-dynamic walkers and the interactions between the walker and the ground surface. Several trials were performed to quantify the stability space of the experimental walker and improve the correlation of the dynamics model to the physical robot.

  5. Shock-driven mixing: Experimental design and initial conditions

    NASA Astrophysics Data System (ADS)

    Friedman, Gavin; Prestridge, Katherine; Mejia-Alvarez, Ricardo; Leftwich, Megan

    2012-03-01

    A new Vertical Shock Tube (VST) has been designed to study shock-induced mixing due to the Richtmyer-Meshkov Instability (RMI) developing on a 3-D multi-mode interface between two gases. These studies characterize how interface contours, gas density difference, and Mach No. affect the ensuing mixing by using simultaneous measurements of velocity/density fields. The VST allows for the formation of a single stably-stratified interface, removing complexities of the dual interface used in prior RMI work. The VST also features a new diaphragmless driver, making feasible larger ensembles of data by reducing intra-shot time, and a larger viewing window allowing new observations of late-time mixing. The initial condition (IC) is formed by a co-flow system, chosen to minimize diffusion at the gas interface. To ensure statistically stationary ICs, a contoured nozzle has been manufactured to form repeatable co-flowing jets that are manipulated by a flapping splitter plate to generate perturbations that span the VST. This talk focuses on the design of the IC flow system and shows initial results characterizing the interface.

  6. Shock-Driven Mixing: Experimental Design and Initial Conditions

    NASA Astrophysics Data System (ADS)

    Friedman, Gavin; Prestridge, Kathy; Mejia-Alvarez, Ricardo; Leftwich, Megan

    2011-06-01

    A new Vertical Shock Tube (VST) has been designed to study shock-induced mixing due to the Richtmyer-Meshkov Instability (RMI) developing on a 3-D multi-mode interface between two gases. These studies characterize how interface contours, gas density difference, and Mach No. affect the ensuing mixing by using simultaneous measurements of velocity/density fields. The VST allows for the formation of a single stably-stratified interface, removing complexities of the dual interface used in prior RMI work. The VST also features a new diaphragmless driver, making feasible larger ensembles of data by reducing intra-shot time, and a larger viewing window allowing new observations of late-time mixing. The initial condition (IC) is formed by a co-flow system, chosen to minimize diffusion at the gas interface. To ensure statistically stationary ICs, a contoured nozzle has been manufactured to form repeatable co-flowing jets that are manipulated by a flapping splitter plate to generate perturbations that span the VST. This talk focuses on the design of the IC flow system and shows initial results characterizing the interface.

  7. The Signature of Initial Conditions on Magnetohydrodynamic Turbulence

    NASA Astrophysics Data System (ADS)

    Dallas, V.; Alexakis, A.

    2014-06-01

    We demonstrate that the initial correlation between velocity and current density fluctuations can lead to the formation of enormous current sheets in freely evolving magnetohydrodynamic (MHD) turbulence. These coherent structures are observed at the peak of the energy dissipation rate and are the carriers of long-range correlations despite all of the nonlinear interactions during the formation of turbulence. The size of these structures spans our computational domain, dominating the scaling of the energy spectrum, which follows a Evpropk -2 power law. As the Reynolds number increases, the curling of the current sheets due to Kelvin-Helmholtz-type instabilities and reconnection modifies the scaling of the energy spectrum from k -2 toward k -5/3. This transition occurs due to the decorrelation of the velocity and the current density which is proportional to Re_λ -3/2. Finite Reynolds number behavior is observed without reaching a finite asymptote for the energy dissipation rate even for a simulation of Reλ ~= 440 with 20483 grid points. This behavior demonstrates that even state-of-the-art numerical simulations of the highest Reynolds numbers can be influenced by the choice of initial conditions and consequently they are inadequate to deduce unequivocally the fate of universality in MHD turbulence. Implications for astrophysical observations are discussed.

  8. Identification and Evaluation of Reference Genes for Accurate Transcription Normalization in Safflower under Different Experimental Conditions.

    PubMed

    Li, Dandan; Hu, Bo; Wang, Qing; Liu, Hongchang; Pan, Feng; Wu, Wei

    2015-01-01

    Safflower (Carthamus tinctorius L.) has received a significant amount of attention as a medicinal plant and oilseed crop. Gene expression studies provide a theoretical molecular biology foundation for improving new traits and developing new cultivars. Real-time quantitative PCR (RT-qPCR) has become a crucial approach for gene expression analysis. In addition, appropriate reference genes (RGs) are essential for accurate and rapid relative quantification analysis of gene expression. In this study, fifteen candidate RGs involved in multiple metabolic pathways of plants were finally selected and validated under different experimental treatments, at different seed development stages and in different cultivars and tissues for real-time PCR experiments. These genes were ABCS, 60SRPL10, RANBP1, UBCL, MFC, UBCE2, EIF5A, COA, EF1-β, EF1, GAPDH, ATPS, MBF1, GTPB and GST. The suitability evaluation was executed by the geNorm and NormFinder programs. Overall, EF1, UBCE2, EIF5A, ATPS and 60SRPL10 were the most stable genes, and MBF1, as well as MFC, were the most unstable genes by geNorm and NormFinder software in all experimental samples. To verify the validation of RGs selected by the two programs, the expression analysis of 7 CtFAD2 genes in safflower seeds at different developmental stages under cold stress was executed using different RGs in RT-qPCR experiments for normalization. The results showed similar expression patterns when the most stable RGs selected by geNorm or NormFinder software were used. However, the differences were detected using the most unstable reference genes. The most stable combination of genes selected in this study will help to achieve more accurate and reliable results in a wide variety of samples in safflower.

  9. Identification and Evaluation of Reference Genes for Accurate Transcription Normalization in Safflower under Different Experimental Conditions

    PubMed Central

    Li, Dandan; Hu, Bo; Wang, Qing; Liu, Hongchang; Pan, Feng; Wu, Wei

    2015-01-01

    Safflower (Carthamus tinctorius L.) has received a significant amount of attention as a medicinal plant and oilseed crop. Gene expression studies provide a theoretical molecular biology foundation for improving new traits and developing new cultivars. Real-time quantitative PCR (RT-qPCR) has become a crucial approach for gene expression analysis. In addition, appropriate reference genes (RGs) are essential for accurate and rapid relative quantification analysis of gene expression. In this study, fifteen candidate RGs involved in multiple metabolic pathways of plants were finally selected and validated under different experimental treatments, at different seed development stages and in different cultivars and tissues for real-time PCR experiments. These genes were ABCS, 60SRPL10, RANBP1, UBCL, MFC, UBCE2, EIF5A, COA, EF1-β, EF1, GAPDH, ATPS, MBF1, GTPB and GST. The suitability evaluation was executed by the geNorm and NormFinder programs. Overall, EF1, UBCE2, EIF5A, ATPS and 60SRPL10 were the most stable genes, and MBF1, as well as MFC, were the most unstable genes by geNorm and NormFinder software in all experimental samples. To verify the validation of RGs selected by the two programs, the expression analysis of 7 CtFAD2 genes in safflower seeds at different developmental stages under cold stress was executed using different RGs in RT-qPCR experiments for normalization. The results showed similar expression patterns when the most stable RGs selected by geNorm or NormFinder software were used. However, the differences were detected using the most unstable reference genes. The most stable combination of genes selected in this study will help to achieve more accurate and reliable results in a wide variety of samples in safflower. PMID:26457898

  10. Identification and Evaluation of Reference Genes for Accurate Transcription Normalization in Safflower under Different Experimental Conditions.

    PubMed

    Li, Dandan; Hu, Bo; Wang, Qing; Liu, Hongchang; Pan, Feng; Wu, Wei

    2015-01-01

    Safflower (Carthamus tinctorius L.) has received a significant amount of attention as a medicinal plant and oilseed crop. Gene expression studies provide a theoretical molecular biology foundation for improving new traits and developing new cultivars. Real-time quantitative PCR (RT-qPCR) has become a crucial approach for gene expression analysis. In addition, appropriate reference genes (RGs) are essential for accurate and rapid relative quantification analysis of gene expression. In this study, fifteen candidate RGs involved in multiple metabolic pathways of plants were finally selected and validated under different experimental treatments, at different seed development stages and in different cultivars and tissues for real-time PCR experiments. These genes were ABCS, 60SRPL10, RANBP1, UBCL, MFC, UBCE2, EIF5A, COA, EF1-β, EF1, GAPDH, ATPS, MBF1, GTPB and GST. The suitability evaluation was executed by the geNorm and NormFinder programs. Overall, EF1, UBCE2, EIF5A, ATPS and 60SRPL10 were the most stable genes, and MBF1, as well as MFC, were the most unstable genes by geNorm and NormFinder software in all experimental samples. To verify the validation of RGs selected by the two programs, the expression analysis of 7 CtFAD2 genes in safflower seeds at different developmental stages under cold stress was executed using different RGs in RT-qPCR experiments for normalization. The results showed similar expression patterns when the most stable RGs selected by geNorm or NormFinder software were used. However, the differences were detected using the most unstable reference genes. The most stable combination of genes selected in this study will help to achieve more accurate and reliable results in a wide variety of samples in safflower. PMID:26457898

  11. Finite element model of spinal hemiepiphysiodesis: effect of contact conditions, initial conditions, and growth.

    PubMed

    Kumar, B; Bylski-Austrow, D I; Liu, Y

    2012-01-01

    Growth modification is under investigation to treat pediatric spine deformities. A hemiepiphyseal staple construct has been shown to alter growth and create physeal structural gradients in an in vivo porcine model. A finite element model (FEM) of a motion segment with and without implant was developed based on preliminary experimental results of initial post-operative motion segment compressive properties. The nonlinear tangent stiffness determined from the model correlated well with the experiments for the native segment, whereas after addition of the implant, the model overestimated the stiffness. The current purpose was to determine the effect of implant-bone contact conditions and initial disc displacement conditions, include growth effects, and compare FEM and experimental results at each stage. A 3D FEM was developed from a CT scan of a porcine T7-T8 segment. The annulus was modeled as an incompressible anisotropic hyperelastic material, and the nucleus as an incompressible fluid. A CAD model of the implant was constructed. Load-displacement curves in compression were determined from a nonlinear analysis performed under different initial and bone-implant interface conditions. Contact conditions were a) perfect, b) friction of 0.1-0.3, or c) soft contact. Initial conditions were that implant insertion induced a) no change in stress or strain in the disc, b) a 2˚ angulation with a centrally located neutral axis and no residual stresses, and c) both stress and coronal plane displacement gradients. Growth modulation effects were added using a published linear relationship between compressive stress and growth rate. A 2 month PO time was simulated. Altering bone - implant surface contact conditions from perfect to either friction or soft contact decreased the stiffness, but all models remained stiffer than experimental results. An initial disc angulation without residual stress did not affect stiffness, whereas stiffness increased with an initial angle and

  12. Multi-Scale Initial Conditions For Cosmological Simulations

    SciTech Connect

    Hahn, Oliver; Abel, Tom; /KIPAC, Menlo Park /ZAH, Heidelberg /HITS, Heidelberg

    2011-11-04

    We discuss a new algorithm to generate multi-scale initial conditions with multiple levels of refinements for cosmological 'zoom-in' simulations. The method uses an adaptive convolution of Gaussian white noise with a real-space transfer function kernel together with an adaptive multi-grid Poisson solver to generate displacements and velocities following first- (1LPT) or second-order Lagrangian perturbation theory (2LPT). The new algorithm achieves rms relative errors of the order of 10{sup -4} for displacements and velocities in the refinement region and thus improves in terms of errors by about two orders of magnitude over previous approaches. In addition, errors are localized at coarse-fine boundaries and do not suffer from Fourier-space-induced interference ringing. An optional hybrid multi-grid and Fast Fourier Transform (FFT) based scheme is introduced which has identical Fourier-space behaviour as traditional approaches. Using a suite of re-simulations of a galaxy cluster halo our real-space-based approach is found to reproduce correlation functions, density profiles, key halo properties and subhalo abundances with per cent level accuracy. Finally, we generalize our approach for two-component baryon and dark-matter simulations and demonstrate that the power spectrum evolution is in excellent agreement with linear perturbation theory. For initial baryon density fields, it is suggested to use the local Lagrangian approximation in order to generate a density field for mesh-based codes that is consistent with the Lagrangian perturbation theory instead of the current practice of using the Eulerian linearly scaled densities.

  13. A method of generating initial conditions for cosmological N-body simulations

    SciTech Connect

    Joyce, M.; Levesque, D.; Marcos, B.

    2005-11-15

    We investigate the possibility of generating initial conditions for cosmological N-body simulations by simulating a system whose correlations at thermal equilibrium approximate well those of cosmological density perturbations. The system is an appropriately modified version of the standard 'one component plasma' (OCP). We show first how a well-known semianalytic method can be used to determine the potential required to produce the desired correlations, and then verify our results for some cosmological type spectra with simulations of the full molecular dynamics. The advantage of the method, compared to the standard one, is that it gives by construction an accurate representation of both the real and reciprocal space correlation properties of the theoretical model. Furthermore the distributions are also statistically homogeneous and isotropic. We discuss briefly the modifications needed to implement the method to produce configurations appropriate for large N-body simulations in cosmology, and also the generation of initial velocities in this context.

  14. A novel, integrated PET-guided MRS technique resulting in more accurate initial diagnosis of high-grade glioma.

    PubMed

    Kim, Ellen S; Satter, Martin; Reed, Marilyn; Fadell, Ronald; Kardan, Arash

    2016-06-01

    Glioblastoma multiforme (GBM) is the most common and lethal malignant glioma in adults. Currently, the modality of choice for diagnosing brain tumor is high-resolution magnetic resonance imaging (MRI) with contrast, which provides anatomic detail and localization. Studies have demonstrated, however, that MRI may have limited utility in delineating the full tumor extent precisely. Studies suggest that MR spectroscopy (MRS) can also be used to distinguish high-grade from low-grade gliomas. However, due to operator dependent variables and the heterogeneous nature of gliomas, the potential for error in diagnostic accuracy with MRS is a concern. Positron emission tomography (PET) imaging with (11)C-methionine (MET) and (18)F-fluorodeoxyglucose (FDG) has been shown to add additional information with respect to tumor grade, extent, and prognosis based on the premise of biochemical changes preceding anatomic changes. Combined PET/MRS is a technique that integrates information from PET in guiding the location for the most accurate metabolic characterization of a lesion via MRS. We describe a case of glioblastoma multiforme in which MRS was initially non-diagnostic for malignancy, but when MRS was repeated with PET guidance, demonstrated elevated choline/N-acetylaspartate (Cho/NAA) ratio in the right parietal mass consistent with a high-grade malignancy. Stereotactic biopsy, followed by PET image-guided resection, confirmed the diagnosis of grade IV GBM. To our knowledge, this is the first reported case of an integrated PET/MRS technique for the voxel placement of MRS. Our findings suggest that integrated PET/MRS may potentially improve diagnostic accuracy in high-grade gliomas.

  15. Sensitive dependence on initial conditions in gene networks

    NASA Astrophysics Data System (ADS)

    Machina, A.; Edwards, R.; van den Driessche, P.

    2013-06-01

    Active regulation in gene networks poses mathematical challenges that have led to conflicting approaches to analysis. Competing regulation that keeps concentrations of some transcription factors at or near threshold values leads to so-called singular dynamics when steeply sigmoidal interactions are approximated by step functions. An extension, due to Artstein and coauthors, of the classical singular perturbation approach was suggested as an appropriate way to handle the complex situation where non-trivial dynamics, such as a limit cycle, of fast variables occur in switching domains. This non-trivial behaviour can occur when a gene regulates multiple other genes at the same threshold. Here, it is shown that it is possible for nonuniqueness to arise in such a system in the case of limiting step-function interactions. This nonuniqueness is reminiscent of but not identical to the nonuniqueness of Filippov solutions. More realistic gene network models have sigmoidal interactions, however, and in the example considered here, it is shown numerically that the corresponding phenomenon in smooth systems is a sensitivity to initial conditions that leads in the limit to densely interwoven basins of attraction of different fixed point attractors.

  16. The relationship between initial errorless learning conditions and subsequent performance.

    PubMed

    Poolton, J M; Masters, R S W; Maxwell, J P

    2005-06-01

    This experiment explores a suggestion by [Maxwell, J.P., Masters, R.S.W., Kerr, E., Weedon, E. (2001). The implicit benefit of learning without errors. Quarterly Journal of Experimental Psychology A 54, 1049-1068] that an initial bout of implicit motor learning confers beneficial performance characteristics, such as robustness under secondary task loading, despite subsequent explicit learning. Participants acquired a complex motor skill (golf putting) over 400 trials. The environment was constrained early in learning to minimize performance error. It was predicted that in the absence of explicit instruction, reducing error would prevent hypothesis testing strategies and the concomitant accrual of declarative (explicit) knowledge, thereby reducing dependence on working memory resources. The effect of an additional cognitive task on putting performance was used to assess reliance on working memory. Putting performance of participants in the Implicit-Explicit condition was unaffected by the additional cognitive load, whereas the performance of Explicit participants deteriorated. The relationship between error correction and episodic verbal reports suggested that the explicit group were involved in more hypothesis testing behaviours than the Implicit-Explicit group early in learning. It was concluded that a constrained, uninstructed, environment early in learning, results in procedurally based motor output unencumbered by disadvantages associated with working memory control. PMID:16087262

  17. Star formation in mergers with cosmologically motivated initial conditions

    NASA Astrophysics Data System (ADS)

    Karman, Wouter; Macciò, Andrea V.; Kannan, Rahul; Moster, Benjamin P.; Somerville, Rachel S.

    2015-09-01

    We use semi-analytic models and cosmological merger trees to provide the initial conditions for multimerger numerical hydrodynamic simulations, and exploit these simulations to explore the effect of galaxy interaction and merging on star formation (SF). We compute numerical realizations of 12 merger trees from z = 1.5 to 0. We include the effects of the large hot gaseous halo around all galaxies, following recent observations and predictions of galaxy formation models. We find that including the hot gaseous halo has a number of important effects. First, as expected, the star formation rate on long time-scales is increased due to cooling of the hot halo and refuelling of the cold gas reservoir. Secondly, we find that interactions do not always increase the SF in the long term. This is partially due to the orbiting galaxies transferring gravitational energy to the hot gaseous haloes and raising their temperature. Finally, we find that the relative size of the starburst, when including the hot halo, is much smaller than previous studies showed. Our simulations also show that the order and timing of interactions are important for the evolution of a galaxy. When multiple galaxies interact at the same time, the SF enhancement is less than when galaxies interact in series. All these effects show the importance of including hot gas and cosmologically motivated merger trees in galaxy evolution models.

  18. Building up the Population III initial mass function from cosmological initial conditions

    NASA Astrophysics Data System (ADS)

    Stacy, Athena; Bromm, Volker; Lee, Aaron T.

    2016-10-01

    We simulate the growth of a Population III stellar system, starting from cosmological initial conditions at z = 100. We follow the formation of a minihalo and the subsequent collapse of its central gas to high densities, resolving scales as small as ˜ 1 au. Using sink particles to represent the growing protostars, we model the growth of the photodissociating and ionizing region around the first sink, continuing the simulation for ˜5000 yr after initial protostar formation. Along with the first-forming sink, several tens of secondary sinks form before an ionization front develops around the most massive star. The resulting cluster has high rates of sink formation, ejections from the stellar disc, and sink mergers during the first ˜ 2000 yr, before the onset of radiative feedback. By this time, a warm ˜5000 K phase of neutral gas has expanded to roughly the disc radius of 2000 au, slowing mass flow on to the disc and sinks. By 5000 yr the most massive star grows to 20 M⊙, while the total stellar mass approaches 75 M⊙. Out of the ˜ 40 sinks, approximately 30 are low mass (M* < 1 M⊙), and if the simulation had resolved smaller scales an even greater number of sinks might have formed. Thus, protostellar radiative feedback is insufficient to prevent rapid disc fragmentation and the formation of a high-member Pop III cluster before an ionization front emerges. Throughout the simulation, the majority of stellar mass is contained within the most massive stars, further implying that the Pop III initial mass function is top-heavy.

  19. Effect of initial conditions on turbulent reattachment downstream of a backward-facing step

    NASA Technical Reports Server (NTRS)

    Westphal, R. V.; Johnston, J. P.

    1984-01-01

    The reattachment of a fully turbulent, two-dimentional shear layer downstream of a backward-facing step has been studied experimentally. The work examines the effect of variations in inlet conditions on the process of reattachment. A series of experiments was conducted in a low-speed wind tunnel using specialized instrumentation suited to the highly turbulent reversing flow near reattachment. Accurate characterization of the time-mean features of the reattaching flows was possible. Assuming linear scaling normalized on distance from reattachment, distributions of normalized pressure coefficient and forward flow fraction, and time-averaged skin friction coefficient appear universal for two-dimensional reattachment, independent of initial conditions and step height, for given duct geometry (area ratio) and for high step-height Reyolds numbers with thin separating boundary layers. The results suggest universal flow structure in the reattachment zone.

  20. Conditions for accurate Karl Fischer coulometry using diaphragm-free cells.

    PubMed

    Nordmark, U; Cedergren, A

    2000-01-01

    Factors influencing the extent of formation of oxidizable reduction products in coulometric cells used for Karl Fischer (KF) determination of water were investigated. For methanolic KF reagents buffered with imidazole (Im) or diethanolamine (DEA) (separately or in combination), three parameters were found to be of outmost importance: the cathodic current density, the pH, and the concentration of protonated base (ImH+ or DEAH+). For reagents buffered with only Im, the relative formation of oxidizable reduction products varied in the range 2-40%; i.e., 51-70 micrograms of water was found for a 50 micrograms water sample, depending on the above-mentioned parameters. The lowest values were observed for reagents having a pH around 10 in combination with cathodic current densities in the range 2000-5000 mA cm-2. For all the Imbuffered reagents investigated, the addition of modifiers such as chloroform, hexanol, and carbon tetrachloride was found to decrease the formation of oxidizable reduction products significantly. For example, a reagent buffered at pH 10 containing 1 M hexanol gave less than 0.3% formation in the current density interval from 200 to 4000 mA cm-2. The best reagents based on the above-mentioned modifiers were tested in the continuous coulometric mode with errors typically in the interval 0-0.5% using optimum conditions. One prerequisite for obtaining such small errors with diaphragm-free continuous coulometry is to use a cathode area no larger than 0.002 cm2. For some of the reagents based on both Im and DEA, the formation of oxidizable reduction products was close to zero at certain current densities, although the analytical performance was not as good as for the reagents buffered solely by Im due to longer conditioning and titration times.

  1. Experimental study of infrared filaments under different initial conditions

    NASA Astrophysics Data System (ADS)

    Mirell, Daniel Joseph

    field that gives birth to multiphoton and avalanche ionization), (b) conical emission/supercontinuum generation, and (c) emitted THz radiation. The aim of all of this research is to gain a better understanding of filamentation so that we may learn how to control them for the applications of: (a) laser-induced lightning, (b) laser-induced breakdown spectroscopy, (c) LIDAR, (d) medical imaging and many more. In this dissertation we will focus on an experimental study of filamentation in air produced by 780 nm radiation, pulsewidths of 200 fs, and energies pulse of 9 mJ/pulse. We have used an aerodynamic window + vacuum system to study the difference between focusing filament forming pulses down initially in vacuum conditions to that where it is allowed to focus in atmosphere. Described herein is a new way to use an off-the-shelf, inexpensive and robust 1064 nm mirror to observe the beam profile and its evolution in the filament as well as the filaments spectral properties. In addition, experiments to test for the plasma have been conducted. The results of these experiments indicate filament sizes of 200mum, in contrast to the commonly reported value of 100pm. Filaments of this size exist over a length of approximately a meter which is 8 times longer than the associated Rayleigh range for such a spot size with a clear enhancement in filament persistence with the use of the aerodynamic window. In addition the appearance of newly generated "bluer" frequencies that is present under atmospheric focusing is ail but eliminated through an initial focusing of the beam in vacuum conditions. Plasma densities of 1016 e -/cm3 were measured using plasma interferometry.

  2. On the accurate long-time solution of the wave equation in exterior domains: Asymptotic expansions and corrected boundary conditions

    NASA Technical Reports Server (NTRS)

    Hagstrom, Thomas; Hariharan, S. I.; Maccamy, R. C.

    1993-01-01

    We consider the solution of scattering problems for the wave equation using approximate boundary conditions at artificial boundaries. These conditions are explicitly viewed as approximations to an exact boundary condition satisfied by the solution on the unbounded domain. We study the short and long term behavior of the error. It is provided that, in two space dimensions, no local in time, constant coefficient boundary operator can lead to accurate results uniformly in time for the class of problems we consider. A variable coefficient operator is developed which attains better accuracy (uniformly in time) than is possible with constant coefficient approximations. The theory is illustrated by numerical examples. We also analyze the proposed boundary conditions using energy methods, leading to asymptotically correct error bounds.

  3. On initial conditions for the hot big bang

    SciTech Connect

    Bezrukov, F.; Gorbunov, D.; Shaposhnikov, M. E-mail: gorby@ms2.inr.ac.ru

    2009-06-01

    We analyse the process of reheating the Universe in the electroweak theory where the Higgs field plays a role of the inflaton. We estimate the maximal temperature of the Universe and fix the initial conditions for radiation-dominated phase of the Universe expansion in the framework of the Standard Model (SM) and of the νMSM—the minimal extension of the SM by three right-handed singlet fermions. We show that the inflationary epoch is followed by a matter dominated stage related to the Higgs field oscillations. We investigate the energy transfer from Higgs-inflaton to the SM particles and show that the radiation dominated phase of the Universe expansion starts at temperature T{sub r} ≅ (3−15) × 10{sup 13} GeV, where the upper bound depends on the Higgs boson mass. We estimate the production rate of singlet fermions at preheating and find that their concentrations at T{sub r} are negligibly small. This suggests that the sterile neutrino Dark Matter (DM) production and baryogenesis in the νMSM with Higgs-driven inflation are low energy phenomena, having nothing to do with inflation. We study then a modification of the νMSM, adding to its Lagrangian higher dimensional operators suppressed by the Planck scale. The role of these operators in Higgs-driven inflation is clarified. We find that these operators do not contribute to the production of Warm Dark Matter (WDM) and to baryogenesis. We also demonstrate that the sterile neutrino with mass exceeding 100 keV (a Cold Dark Matter (CDM) candidate) can be created during the reheating stage of the Universe in necessary amounts. We argue that the mass of DM sterile neutrino should not exceed few MeV in order not to overclose the Universe.

  4. Accurately measuring sea level change from space: an ESA climate change initiative for MSL closure budget studies

    NASA Astrophysics Data System (ADS)

    Legeais, JeanFrancois; Benveniste, Jérôme

    2016-07-01

    Sea level is a very sensitive index of climate change and variability. Sea level integrates the ocean warming, mountain glaciers and ice sheet melting. Understanding the sea level variability and changes implies an accurate monitoring of the sea level variable at climate scales, in addition to understanding the ocean variability and the exchanges between ocean, land, cryosphere, and atmosphere. That is why Sea Level is one of the Essential Climate Variables (ECV) selected in the frame of the ESA Climate Change Initiative (CCI) program. It aims at providing long-term monitoring of the sea level ECV with regular updates, as required for climate studies. The program is now in its second phase of 3 year (following phase I during 2011-2013). The objectives are firstly to involve the climate research community, to refine their needs and collect their feedbacks on product quality. And secondly to develop, test and select the best algorithms and standards to generate an updated climate time series and to produce and validate the Sea Level ECV product. This will better answer the climate user needs by improving the quality of the Sea Level products and maintain a sustain service for an up-to-date production. This has led to the production of a first version of the Sea Level ECV which has benefited from yearly extensions and now covers the period 1993-2014. Within phase II, new altimeter standards have been developed and tested in order to reprocess the dataset with the best standards for climate studies. The reprocessed ECV will be released in summer 2016. We will present the main achievements of the ESA CCI Sea Level Project. On the one hand, the major steps required to produce the 22 years climate time series are briefly described: collect and refine the user requirements, development of adapted algorithms for climate applications and specification of the production system. On the other hand, the product characteristics are described as well as the results from product

  5. Mineralogical compositions of aquifer matrix as necessary initial conditions in reactive contaminant transport models.

    PubMed

    Zhu, C; Burden, D S

    2001-10-01

    Mineralogical compositions and their spatial distributions are important initial conditions for reactive transport modeling. However, popular Kd-based "reactive" transport models only require contaminant concentrations in the pore fluids as initial conditions, and minerals implicitly represent infinite sources and sinks in these models. That situation results in a general neglect of mineralogical characterization in site investigations. This study uses a coupled multi-component reactive mass transport model to predict the natural attenuation of a ground water plume at a uranium mill tailings site in western USA. Numerous ground water geochemistry data are available at this site, but mineralogical data are sketchy. Even given the well-defined pore fluid chemistry, variations of secondary mineral species and mineral abundances in the aquifer resulted in significantly different modeling outcomes. Results show that the amount of calcite in the aquifer determines the distances of plume migration. The possible presence of jurbanite, an aluminum sulfate phase, can store acidity temporarily but cause more severe contamination on a later date. The surfaces of iron oxyhydroxides can store significant amounts of sulfate and protons and serve as a second source for prolonged contamination. These simulations under field conditions illustrate that mineralogical compositions are an essential requirement for accurate prediction of contaminant fate and transport. PMID:11588823

  6. Symbolic computation of analytic approximate solutions for nonlinear differential equations with initial conditions

    NASA Astrophysics Data System (ADS)

    Lin, Yezhi; Liu, Yinping; Li, Zhibin

    2012-01-01

    The Adomian decomposition method (ADM) is one of the most effective methods for constructing analytic approximate solutions of nonlinear differential equations. In this paper, based on the new definition of the Adomian polynomials, and the two-step Adomian decomposition method (TSADM) combined with the Padé technique, a new algorithm is proposed to construct accurate analytic approximations of nonlinear differential equations with initial conditions. Furthermore, a MAPLE package is developed, which is user-friendly and efficient. One only needs to input a system, initial conditions and several necessary parameters, then our package will automatically deliver analytic approximate solutions within a few seconds. Several different types of examples are given to illustrate the validity of the package. Our program provides a helpful and easy-to-use tool in science and engineering to deal with initial value problems. Program summaryProgram title: NAPA Catalogue identifier: AEJZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4060 No. of bytes in distributed program, including test data, etc.: 113 498 Distribution format: tar.gz Programming language: MAPLE R13 Computer: PC Operating system: Windows XP/7 RAM: 2 Gbytes Classification: 4.3 Nature of problem: Solve nonlinear differential equations with initial conditions. Solution method: Adomian decomposition method and Padé technique. Running time: Seconds at most in routine uses of the program. Special tasks may take up to some minutes.

  7. Experiments using new initial soil moisture conditions and soil map in the Eta model over La Plata Basin

    NASA Astrophysics Data System (ADS)

    Doyle, Moira E.; Tomasella, Javier; Rodriguez, Daniel A.; Chou, Sin Chan

    2013-08-01

    An effort towards a more accurate representation of soil moisture and its impact on the modeling of weather systems is presented. Sensitivity tests of precipitation to soil type and soil moisture changes are carried out using the atmospheric Eta model for the numerical simulation of the development of a mesoscale convective system over northern Argentina. Modified initial soil moisture conditions were obtained from a hydrological balance model developed and running operationally at INPE. A new soil map was elaborated using the available soil profile information from Brazil, Paraguay, Uruguay, and Argentina and depicts 18 different soil types. Results indicate that more accurate initial soil moisture conditions and incorporating a new soil map with hydraulic parameters, more representative of South American soils, improve daily total precipitation forecasts both in quantitative and spatial representations.

  8. Initial-Condition Influences on CME Expansion and Propagation

    NASA Astrophysics Data System (ADS)

    Siscoe, G. L.; Crooker, N. U.; Elliott, H. A.

    2006-12-01

    A general-purpose melon-seed-overpressure-expansion (MSOE) model is used to examine the dependence of the expansion and propagation of fast CMEs on average initial values of the magnetic field inside the CME, the magnetic field outside the CME, and the CME mass. The MSOE model extracts from the real situation only features that are essential in determining the expansion and propagation processes and idealizes them to obtain an adaptable “minimalist” set of equations that governs these processes yet retains enough relevant physics to give useful results. This minimalist set is used to carry out a systematic comparison of solutions against four sets of observed correlations between CME and ICME parameters in which the input parameters to the MSOE model are varied to achieve simultaneous fits to all four correlations. The fits impose relations between the three independent input variables: initial internal field strength, initial external field strength, and initial density. For example, light CMEs ( e.g., those with no prominences) require the external field strength to nearly equal the internal field strength. However, heavy CMEs ( e.g., those with prominences) require the external field strength to be much weaker than the internal field strength.

  9. Effects of the inlet conditions and blood models on accurate prediction of hemodynamics in the stented coronary arteries

    NASA Astrophysics Data System (ADS)

    Jiang, Yongfei; Zhang, Jun; Zhao, Wanhua

    2015-05-01

    Hemodynamics altered by stent implantation is well-known to be closely related to in-stent restenosis. Computational fluid dynamics (CFD) method has been used to investigate the hemodynamics in stented arteries in detail and help to analyze the performances of stents. In this study, blood models with Newtonian or non-Newtonian properties were numerically investigated for the hemodynamics at steady or pulsatile inlet conditions respectively employing CFD based on the finite volume method. The results showed that the blood model with non-Newtonian property decreased the area of low wall shear stress (WSS) compared with the blood model with Newtonian property and the magnitude of WSS varied with the magnitude and waveform of the inlet velocity. The study indicates that the inlet conditions and blood models are all important for accurately predicting the hemodynamics. This will be beneficial to estimate the performances of stents and also help clinicians to select the proper stents for the patients.

  10. Regimes of chemical reaction waves initiated by nonuniform initial conditions for detailed chemical reaction models.

    PubMed

    Liberman, M A; Kiverin, A D; Ivanov, M F

    2012-05-01

    Regimes of chemical reaction wave propagation initiated by initial temperature nonuniformity in gaseous mixtures, whose chemistry is governed by chain-branching kinetics, are studied using a multispecies transport model and a detailed chemical model. Possible regimes of reaction wave propagation are identified for stoichiometric hydrogen-oxygen and hydrogen-air mixtures in a wide range of initial pressures and temperature levels, depending on the initial non-uniformity steepness. The limits of the regimes of reaction wave propagation depend upon the values of the spontaneous wave speed and the characteristic velocities of the problem. It is shown that one-step kinetics cannot reproduce either quantitative neither qualitative features of the ignition process in real gaseous mixtures because the difference between the induction time and the time when the exothermic reaction begins significantly affects the ignition, evolution, and coupling of the spontaneous reaction wave and the pressure wave, especially at lower temperatures. We show that all the regimes initiated by the temperature gradient occur for much shallower temperature gradients than predicted by a one-step model. The difference is very large for lower initial pressures and for slowly reacting mixtures. In this way the paper provides an answer to questions, important in practice, about the ignition energy, its distribution, and the scale of the initial nonuniformity required for ignition in one or another regime of combustion wave propagation.

  11. Parametric initial conditions for core-collapse supernova simulations

    NASA Astrophysics Data System (ADS)

    Suwa, Yudai; Müller, Ewald

    2016-08-01

    We investigate a method to construct parametrized progenitor models for core-collapse supernova simulations. Different from all modern core-collapse supernova studies, which rely on progenitor models from stellar evolution calculations, we follow the methodology of Baron & Cooperstein to construct initial models. Choosing parametrized spatial distributions of entropy and electron fraction as a function of mass coordinate and solving the equation of hydrostatic equilibrium, we obtain the initial density structures of our progenitor models. First, we calculate structures with parameters fitting broadly the evolutionary model s11.2 of Woosley et al. (2002). We then demonstrate the reliability of our method by performing general relativistic hydrodynamic simulations in spherical symmetry with the isotropic diffusion source approximation to solve the neutrino transport. Our comprehensive parameter study shows that initial models with a small central entropy (≲0.4 kB nucleon-1) can explode even in spherically symmetric simulations. Models with a large entropy (≳6 kB nucleon-1) in the Si/O layer have a rather large explosion energy (˜4 × 1050 erg) at the end of the simulations, which is still rapidly increasing.

  12. An accurately preorganized IRES RNA structure enables eIF4G capture for initiation of viral translation.

    PubMed

    Imai, Shunsuke; Kumar, Parimal; Hellen, Christopher U T; D'Souza, Victoria M; Wagner, Gerhard

    2016-09-01

    Many viruses bypass canonical cap-dependent translation in host cells by using internal ribosomal entry sites (IRESs) in their transcripts; IRESs hijack initiation factors for the assembly of initiation complexes. However, it is currently unknown how IRES RNAs recognize initiation factors that have no endogenous RNA binding partners; in a prominent example, the IRES of encephalomyocarditis virus (EMCV) interacts with the HEAT-1 domain of eukaryotic initiation factor 4G (eIF4G). Here we report the solution structure of the J-K region of this IRES and show that its stems are precisely organized to position protein-recognition bulges. This multisite interaction mechanism operates on an all-or-nothing principle in which all domains are required. This preorganization is accomplished by an 'adjuster module': a pentaloop motif that acts as a dual-sided docking station for base-pair receptors. Because subtle changes in the orientation abrogate protein capture, our study highlights how a viral RNA acquires affinity for a target protein. PMID:27525590

  13. Recovery methods of the dragonfly from irregular initial conditions

    NASA Astrophysics Data System (ADS)

    Melfi, James; Leonardo, Anthony; Wang, Jane

    We release dragonflies from a magnetic tether in a wide range of initial orientations, which results in them utilizing multiple methods to regain their typical flight orientation. Special focus is placed on dropping them while upside down, as the recovery method used is a purely rolling motion. Filming this stereotypical motion with a trio of high speed cameras at 4000 fps, we capture detailed body and wing kinematics data to determine how the dragonfly generates this motion. By replaying the flights within a computer simulation, we can isolate the significant changes to wing kinematics, and find that it is an asymmetry in the wing pitch which generates the roll. Further investigation demonstrates that this choice is highly dependent upon the state of the dragonfly, and as such our results indicate the dragonfly both tracks its current state, and changes its mid-flight control mechanisms accordingly.

  14. A Two-Sinker Densimeter for Accurate Measurements of the Density of Natural Gases at Standard Conditions

    NASA Astrophysics Data System (ADS)

    Richter, Markus; Kleinrahm, Reiner; Glos, Stefan; Wagner, Wolfgang; Span, Roland; Schley, Peter; Uhrig, Martin

    2010-05-01

    A special reference densimeter has been developed for accurate measurements of densities of natural gases and multicomponent gas mixtures at standard conditions of temperature and pressure ( T s = 273.15 K and p s = 0.101325 MPa). The densimeter covers the range from 0.7 kg · m-3 to 1.3 kg · m-3; the total measurement uncertainty in density is 0.020 % (95 % level of confidence). The measurement principle used is the two-sinker method, which is based on the Archimedes buoyancy principle. The certified calibration laboratory of E.ON Ruhrgas AG, Germany, uses this densimeter to verify the standard densities of certified calibration gases (binary and multicomponent gas mixtures). Moreover, the densimeter is used to determine the compositions of commercially available binary gas mixtures with a small uncertainty of (0.01-0.03) mol%.

  15. Do initial conditions matter? A comparison of model climatologies generated from different initial states

    NASA Technical Reports Server (NTRS)

    Spar, J.; Cohen, C.; Wu, P.

    1981-01-01

    A coarse mesh (8 by 10) 7 layer global climate model was used to compute 15 months of meteorological history in two perpetual January experiments on a water planet (without continents) with a zonally symmetric climatological January sea surface temperature field. In the first of the two water planet experiments the initial atmospheric state was a set of zonal mean values of specific humidity, temperature, and wind at each latitude. In the second experiment the model was initialized with globally uniform mean values of specific humidity and temperature on each sigma level surface, constant surface pressure (1010 mb), and zero wind everywhere. A comparison was made of the mean January climatic states generated by the two water planet experiments. The first two months of each 15 January run were discarded, and 13 month averages were computed from months 3 through 15.

  16. Modeling thermal ignition and the initial conditions for internal burning in PBX 9501

    NASA Astrophysics Data System (ADS)

    Henson, Bryan

    2009-06-01

    Work has been ongoing in our group for several years to produce a thermal ignition model for HMX based plastic bonded explosives valid over the entire temperature range of energetic response. We have made considerable progress recently, resulting in both the first broadly accurate model of this type and the possible identification of a crucial component of the chemical mechanism responsible for thermal ignition and decomposition. I will present a new model of thermal ignition for HMX formulations that is based on this recent progress. The model is similar in kind, but very different in detail from previous models produced by us and others. As has been the case for our previous models it is based entirely on known processes in the decomposition of HMX and is highly constrained by independent measurements. We have applied the model in simple calculations of ignition time over the full temperature range of energetic response for HMX, including directly observed ignition induced by fast shear and compression. I will also present new calculations relevant to the initial conditions for internal burning subsequent to ignition in low boundary temperature thermal explosion experiments. Simplified gas phase chemistry relevant to both dark and bright zone burning in HMX has been included and leads to a second, high temperature and pressure ignition zone in this environment. I will discuss experimental support for these calculations and the ramifications for internal pressures at ignition responsible for driving initial subsonic burning subsequent to ignition.

  17. Validation of the criteria for initiating the cleaning of heating, ventilation, and air-conditioning (HVAC) ductwork under real conditions.

    PubMed

    Lavoie, Jacques; Marchand, Geneviève; Cloutier, Yves; Lavoué, Jérôme

    2011-08-01

    Dust accumulation in the components of heating, ventilation, and air-conditioning (HVAC) systems is a potential source of contaminants. To date, very little information is available on recognized methods for assessing dust buildup in these systems. The few existing methods are either objective in nature, involving numerical values, or subjective in nature, based on experts' judgments. An earlier project aimed at assessing different methods of sampling dust in ducts was carried out in the laboratories of the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST). This laboratory study showed that all the sampling methods were practicable, provided that a specific surface-dust cleaning initiation criterion was used for each method. However, these conclusions were reached on the basis of ideal conditions in a laboratory using a reference dust. The objective of this present study was to validate these laboratory results in the field. To this end, the laboratory sampling templates were replicated in real ducts and the three sampling methods (the IRSST method, the method of the U.S. organization National Air Duct Cleaner Association [NADCA] and that of the French organization Association pour la Prévention et l'Étude de la Contamination [ASPEC]) were used simultaneously in a statistically representative number of systems. The air return and supply ducts were also compared. Cleaning initiation criteria under real conditions were found to be 6.0 mg/100 cm(2) using the IRSST method, 2.0 mg/100 cm(2) using the NADCA method, and 23 mg/100 cm(2) using the ASPEC method. In the laboratory study, the criteria using the same methods were 6.0 for the IRSST method, 2.0 for the NADCA method, and 3.0 for the ASPEC method. The laboratory criteria for the IRSST and NADCA methods were therefore validated in the field. The ASPEC criterion was the only one to change. The ASPEC method therefore allows for the most accurate evaluation of dust accumulation in HVAC

  18. Validation of the criteria for initiating the cleaning of heating, ventilation, and air-conditioning (HVAC) ductwork under real conditions.

    PubMed

    Lavoie, Jacques; Marchand, Geneviève; Cloutier, Yves; Lavoué, Jérôme

    2011-08-01

    Dust accumulation in the components of heating, ventilation, and air-conditioning (HVAC) systems is a potential source of contaminants. To date, very little information is available on recognized methods for assessing dust buildup in these systems. The few existing methods are either objective in nature, involving numerical values, or subjective in nature, based on experts' judgments. An earlier project aimed at assessing different methods of sampling dust in ducts was carried out in the laboratories of the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST). This laboratory study showed that all the sampling methods were practicable, provided that a specific surface-dust cleaning initiation criterion was used for each method. However, these conclusions were reached on the basis of ideal conditions in a laboratory using a reference dust. The objective of this present study was to validate these laboratory results in the field. To this end, the laboratory sampling templates were replicated in real ducts and the three sampling methods (the IRSST method, the method of the U.S. organization National Air Duct Cleaner Association [NADCA] and that of the French organization Association pour la Prévention et l'Étude de la Contamination [ASPEC]) were used simultaneously in a statistically representative number of systems. The air return and supply ducts were also compared. Cleaning initiation criteria under real conditions were found to be 6.0 mg/100 cm(2) using the IRSST method, 2.0 mg/100 cm(2) using the NADCA method, and 23 mg/100 cm(2) using the ASPEC method. In the laboratory study, the criteria using the same methods were 6.0 for the IRSST method, 2.0 for the NADCA method, and 3.0 for the ASPEC method. The laboratory criteria for the IRSST and NADCA methods were therefore validated in the field. The ASPEC criterion was the only one to change. The ASPEC method therefore allows for the most accurate evaluation of dust accumulation in HVAC

  19. Initiation of clement surface conditions on the earliest Earth

    PubMed Central

    Sleep, N. H.; Zahnle, K.; Neuhoff, P. S.

    2001-01-01

    In the beginning the surface of the Earth was extremely hot, because the Earth as we know it is the product of a collision between two planets, a collision that also created the Moon. Most of the heat within the very young Earth was lost quickly to space while the surface was still quite hot. As it cooled, the Earth's surface passed monotonically through every temperature regime between silicate vapor to liquid water and perhaps even to ice, eventually reaching an equilibrium with sunlight. Inevitably the surface passed through a time when the temperature was around 100°C at which modern thermophile organisms live. How long this warm epoch lasted depends on how long a thick greenhouse atmosphere can be maintained by heat flow from the Earth's interior, either directly as a supplement to insolation, or indirectly through its influence on the nascent carbonate cycle. In both cases, the duration of the warm epoch would have been controlled by processes within the Earth's interior where buffering by surface conditions played little part. A potentially evolutionarily significant warm period of between 105 and 107 years seems likely, which nonetheless was brief compared to the vast expanse of geological time. PMID:11259665

  20. Initiation of clement surface conditions on the earliest Earth.

    PubMed

    Sleep, N H; Zahnle, K; Neuhoff, P S

    2001-03-27

    In the beginning the surface of the Earth was extremely hot, because the Earth as we know it is the product of a collision between two planets, a collision that also created the Moon. Most of the heat within the very young Earth was lost quickly to space while the surface was still quite hot. As it cooled, the Earth's surface passed monotonically through every temperature regime between silicate vapor to liquid water and perhaps even to ice, eventually reaching an equilibrium with sunlight. Inevitably the surface passed through a time when the temperature was around 100 degrees C at which modern thermophile organisms live. How long this warm epoch lasted depends on how long a thick greenhouse atmosphere can be maintained by heat flow from the Earth's interior, either directly as a supplement to insolation, or indirectly through its influence on the nascent carbonate cycle. In both cases, the duration of the warm epoch would have been controlled by processes within the Earth's interior where buffering by surface conditions played little part. A potentially evolutionarily significant warm period of between 10(5) and 10(7) years seems likely, which nonetheless was brief compared to the vast expanse of geological time.

  1. Cl atom initiated oxidation of 1-alkenes under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Walavalkar, M.; Sharma, A.; Alwe, H. D.; Pushpa, K. K.; Dhanya, S.; Naik, P. D.; Bajaj, P. N.

    2013-03-01

    In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6-C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10-10 cm3 molecule-1 s-1 for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH2 group in alkenes is estimated to be (4.9 ± 0.3) × 10-11 cm3 molecule-1 s-1. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.

  2. Remediation of pollution in a river by unsteady aeration with arbitrary initial and boundary conditions

    NASA Astrophysics Data System (ADS)

    Ibrahim, F. N.; Dimian, M. F.; Wadi, A. S.

    2015-06-01

    The most important parameter controlling the water quality is the dissolved oxygen Y(x, t) because it is very essential for aquatic life. An analytic solution is presented for unsteady equation representing the concentration of the dissolved oxygen Y(x, t) along a river at any time t. The solution is obtained by using Laplace transformation technique. Adjoin solution techniques are used as boundary conditions to solve the equations. The variations of Y(x, t) with time t from t = 0 up to t → ∞ (the steady state case) and with the parameters of the flow are taken into account in our study. It is shown that Y(x, t) increases as t increases, keeping the other parameters constant, but Y(x, t) decreases as the added pollutant rate along the river q increases. The adjoin solution techniques used in this work are effective and accurate for solving the equations representing the concentration of the dissolved oxygen Y(x, t) when arbitrary initial and boundary conditions are given. The details are demonstrated in graphs.

  3. ON THE INITIAL CONDITIONS FOR STAR FORMATION AND THE INITIAL MASS FUNCTION

    SciTech Connect

    Elmegreen, Bruce G.

    2011-04-10

    Density probability distribution functions (PDFs) for turbulent self-gravitating clouds should be convolutions of the local log-normal PDF, which depends on the local average density {rho}{sub ave} and Mach number M, and the PDFs for {rho}{sub ave} and M, which depend on the overall cloud structure. When self-gravity drives a cloud to increased central density, the total PDF develops an extended tail. If there is a critical density or column density for star formation, then the fraction of the local mass exceeding this threshold becomes higher near the cloud center. These elements of cloud structure should be in place before significant star formation begins. Then the efficiency is high so that bound clusters form rapidly, and the stellar initial mass function (IMF) has an imprint in the gas before destructive radiation from young stars can erase it. The IMF could arise from a power-law distribution of mass for cloud structure. These structures should form stars down to the thermal Jeans mass M{sub J} at each density in excess of a threshold. The high-density tail of the PDF, combined with additional fragmentation in each star-forming core, extends the IMF into the brown dwarf regime. The core fragmentation process is distinct from the cloud structuring process and introduces an independent core fragmentation mass function (CFMF). The CFMF would show up primarily below the IMF peak.

  4. Influence of changes in initial conditions for the simulation of dynamic systems

    SciTech Connect

    Kotyrba, Martin

    2015-03-10

    Chaos theory is a field of study in mathematics, with applications in several disciplines including meteorology, sociology, physics, engineering, economics, biology, and philosophy. Chaos theory studies the behavior of dynamical systems that are highly sensitive to initial conditions—a paradigm popularly referred to as the butterfly effect. Small differences in initial conditions field widely diverging outcomes for such dynamical systems, rendering long-term prediction impossible in general. This happens even though these systems are deterministic, meaning that their future behavior is fully determined by their initial conditions, with no random elements involved. In this paperinfluence of changes in initial conditions will be presented for the simulation of Lorenz system.

  5. 42 CFR 410.16 - Initial preventive physical examination: Conditions for and limitations on coverage.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...) BENEFITS Medical and Other Health Services § 410.16 Initial preventive physical examination: Conditions for... 42 Public Health 2 2011-10-01 2011-10-01 false Initial preventive physical examination: Conditions for and limitations on coverage. 410.16 Section 410.16 Public Health CENTERS FOR MEDICARE &...

  6. Hydrological modelling for flood forecasting: Calibrating the post-fire initial conditions

    NASA Astrophysics Data System (ADS)

    Papathanasiou, C.; Makropoulos, C.; Mimikou, M.

    2015-10-01

    Floods and forest fires are two of the most devastating natural hazards with severe socioeconomic, environmental as well as aesthetic impacts on the affected areas. Traditionally, these hazards are examined from different perspectives and are thus investigated through different, independent systems, overlooking the fact that they are tightly interrelated phenomena. In fact, the same flood event is more severe, i.e. associated with increased runoff discharge and peak flow and decreased time to peak, if it occurs over a burnt area than that occurring over a land not affected by fire. Mediterranean periurban areas, where forests covered with flammable vegetation coexist with agricultural land and urban zones, are typical areas particularly prone to the combined impact of floods and forest fires. Hence, the accurate assessment and effective management of post-fire flood risk becomes an issue of priority. The research presented in this paper aims to develop a robust methodological framework, using state of art tools and modern technologies to support the estimation of the change in time of five representative hydrological parameters for post-fire conditions. The proposed methodology considers both longer- and short-term initial conditions in order to assess the dynamic evolution of the selected parameters. The research focuses on typical Mediterranean periurban areas that are subjected to both hazards and concludes with a set of equations that associate post-fire and pre-fire conditions for five Fire Severity (FS) classes and three soil moisture states. The methodology has been tested for several flood events on the Rafina catchment, a periurban catchment in Eastern Attica (Greece). In order to validate the methodology, simulated hydrographs were produced and compared against available observed data. Results indicate a close convergence of observed and simulated flows. The proposed methodology is particularly flexible and thus easily adaptable to catchments with similar

  7. Necessary Conditions for Accurate, Transient Hot-Wire Measurements of the Apparent Thermal Conductivity of Nanofluids are Seldom Satisfied

    NASA Astrophysics Data System (ADS)

    Antoniadis, Konstantinos D.; Tertsinidou, Georgia J.; Assael, Marc J.; Wakeham, William A.

    2016-08-01

    The paper considers the conditions that are necessary to secure accurate measurement of the apparent thermal conductivity of two-phase systems comprising nanoscale particles of one material suspended in a fluid phase of a different material. It is shown that instruments operating according to the transient hot-wire technique can, indeed, produce excellent measurements when a finite element method (FEM) is employed to describe the instrument for the exact geometry of the hot wire. Furthermore, it is shown that an approximate analytic solution can be employed with equal success, over the time range of 0.1 s to 1 s, provided that (a) two wires are employed, so that end effects are canceled, (b) each wire is very thin, less than 30 \\upmu m diameter, so that the line source model and the corresponding corrections are valid, (c) low values of the temperature rise, less than 4 K, are employed in order to minimize the effect of convection on the heat transfer in the time of measurement of 1 s, and (d) insulated wires are employed for measurements in electrically conducting or polar liquids to avoid current leakage or other electrical distortions. According to these criteria, a transient hot-wire instrument has been designed, constructed, and employed for the measurement of the enhancement of the thermal conductivity of water when TiO2 or multi-wall carbon nanotubes (MWCNT) are added. These new results, together with a critical evaluation of other measurements, demonstrate the importance of proper implementation of the technique.

  8. Characterization of condenser microphones under different environmental conditions for accurate speed of sound measurements with acoustic resonators.

    PubMed

    Guianvarc'h, Cécile; Gavioso, Roberto M; Benedetto, Giuliana; Pitre, Laurent; Bruneau, Michel

    2009-07-01

    Condenser microphones are more commonly used and have been extensively modeled and characterized in air at ambient temperature and static pressure. However, several applications of interest for metrology and physical acoustics require to use these transducers in significantly different environmental conditions. Particularly, the extremely accurate determination of the speed of sound in monoatomic gases, which is pursued for a determination of the Boltzmann constant k by an acoustic method, entails the use of condenser microphones mounted within a spherical cavity, over a wide range of static pressures, at the temperature of the triple point of water (273.16 K). To further increase the accuracy achievable in this application, the microphone frequency response and its acoustic input impedance need to be precisely determined over the same static pressure and temperature range. Few previous works examined the influence of static pressure, temperature, and gas composition on the microphone's sensitivity. In this work, the results of relative calibrations of 1/4 in. condenser microphones obtained using an electrostatic actuator technique are presented. The calibrations are performed in pure helium and argon gas at temperatures near 273 K and in the pressure range between 10 and 600 kPa. These experimental results are compared with the predictions of a realistic model available in the literature, finding a remarkable good agreement. The model provides an estimate of the acoustic impedance of 1/4 in. condenser microphones as a function of frequency and static pressure and is used to calculate the corresponding frequency perturbations induced on the normal modes of a spherical cavity when this is filled with helium or argon gas. PMID:19655971

  9. Skewness in large-scale structure and non-Gaussian initial conditions

    NASA Technical Reports Server (NTRS)

    Fry, J. N.; Scherrer, Robert J.

    1994-01-01

    We compute the skewness of the galaxy distribution arising from the nonlinear evolution of arbitrary non-Gaussian intial conditions to second order in perturbation theory including the effects of nonlinear biasing. The result contains a term identical to that for a Gaussian initial distribution plus terms which depend on the skewness and kurtosis of the initial conditions. The results are model dependent; we present calculations for several toy models. At late times, the leading contribution from the initial skewness decays away relative to the other terms and becomes increasingly unimportant, but the contribution from initial kurtosis, previously overlooked, has the same time dependence as the Gaussian terms. Observations of a linear dependence of the normalized skewness on the rms density fluctuation therefore do not necessarily rule out initially non-Gaussian models. We also show that with non-Gaussian initial conditions the first correction to linear theory for the mean square density fluctuation is larger than for Gaussian models.

  10. The non-linear evolution of baryonic overdensities in the early universe: initial conditions of numerical simulations

    NASA Astrophysics Data System (ADS)

    Naoz, Smadar; Yoshida, Naoki; Barkana, Rennan

    2011-09-01

    We run very large cosmological N-body hydrodynamical simulations in order to study statistically the baryon fractions in early dark matter haloes. We critically examine how differences in the initial conditions affect the gas fraction in the redshift range z= 11-21. We test three different linear power spectra for the initial conditions. (1) A complete heating model, which is our fiducial model; this model follows the evolution of overdensities correctly, according to Naoz & Barkana (2005), in particular including the spatial variation of the speed of sound of the gas due to Compton heating from the CMB. (2) An equal-δ model, which assumes that the initial baryon fluctuations are equal to those of the dark matter, while conserving σ8 of the total matter. (3) A mean cs model, which assumes a uniform speed of sound of the gas. The latter two models are often used in the literature. We calculate the baryon fractions for a large sample of haloes in our simulations. Our fiducial model implies that before reionization and significant stellar heating took place, the minimum mass needed for a minihalo to keep most of its baryons throughout its formation was ˜3 × 104 M⊙. However, the alternative models yield a wrong (higher by about 50 per cent) minimum mass, since the system retains a memory of the initial conditions. We also demonstrate this using the 'filtering mass' from linear theory, which accurately describes the evolution of the baryon fraction throughout the simulated redshift range.

  11. Relative Influence of Initial Surface and Atmospheric Conditions on Seasonal Water and Energy Balances

    NASA Technical Reports Server (NTRS)

    Oglesby, Robert J.; Marshall, Susan; Roads, John O.; Robertson, Franklin R.; Goodman, H. Michael (Technical Monitor)

    2001-01-01

    We constructed and analyzed wet and dry soil moisture composites for the mid-latitude GCIP region of the central US using long climate model simulations made with the NCAR CCM3 and reanalysis products from NCEP. Using the diagnostic composites as a guide, we have completed a series of predictability experiments in which we imposed soil water initial conditions in CCM3 for the GCIP region for June 1 from anomalously wet and dry years, with atmospheric initial conditions taken from June 1 of a year with 'near-normal' soil water, and initial soil water from the near-normal year and atmospheric initial conditions from the wet and dry years. Preliminary results indicate that the initial state of the atmosphere is more important than the initial state of soil water determining the subsequent late spring and summer evolution of sod water over the GCIP region. Surprisingly, neither the composites or the predictability experiments yielded a strong influence of soil moisture on the atmosphere. To explore this further, we have made runs with extreme dry soil moisture initial anomalies imposed over the GCIP region (the soil close to being completely dry). These runs did yield a very strong effect on the atmosphere that persisted for at least three months. We conclude that the magnitude of the initial soil moisture anomaly is crucial, at least in CCM3, and are currently investigating whether a threshold exists, below which little impact is seen. In a complementary study, we compared the impact of the initial condition of snow cover versus the initial atmospheric state over the western US (corresponding to the westward extension of the GAPP program follow-on to GCIP). In this case, the initial prescription of snow cover is far more important than the initial atmospheric state in determining the subsequent evolution of snow cover. We are currently working to understand the very different soil water and snow cover results.

  12. Initial conditions for hydrodynamics from weakly coupled pre-equilibrium evolution

    NASA Astrophysics Data System (ADS)

    Keegan, Liam; Kurkela, Aleksi; Mazeliauskas, Aleksas; Teaney, Derek

    2016-08-01

    We use effective kinetic theory, accurate at weak coupling, to simulate the preequilibrium evolution of transverse energy and flow perturbations in heavy-ion collisions. We provide a Green function which propagates the initial perturbations to the energymomentum tensor at a time when hydrodynamics becomes applicable. With this map, the complete pre-thermal evolution from saturated nuclei to hydrodynamics can be modelled in a perturbatively controlled way.

  13. The Use of Graphs in Specific Situations of the Initial Conditions of Linear Differential Equations

    ERIC Educational Resources Information Center

    Buendía, Gabriela; Cordero, Francisco

    2013-01-01

    In this article, we present a discussion on the role of graphs and its significance in the relation between the number of initial conditions and the order of a linear differential equation, which is known as the initial value problem. We propose to make a functional framework for the use of graphs that intends to broaden the explanations of the…

  14. Initial condition for efficient mapping of level set algorithms on many-core architectures

    NASA Astrophysics Data System (ADS)

    Tornai, Gábor János; Cserey, György

    2014-12-01

    In this paper, we investigated the effect of adding more small curves to the initial condition which determines the required number of iterations of a fast level set (LS) evolution. As a result, we discovered two new theorems and developed a proof on the worst case of the required number of iterations. Furthermore, we found that these kinds of initial conditions fit well to many-core architectures. To show this, we have included two case studies which are presented on different platforms. One runs on a graphical processing unit (GPU) and the other is executed on a cellular nonlinear network universal machine (CNN-UM). With the new initial conditions, the steady-state solutions of the LS are reached in less than eight iterations depending on the granularity of the initial condition. These dense iterations can be calculated very quickly on many-core platforms according to the two case studies. In the case of the proposed dense initial condition on GPU, there is a significant speedup compared to the sparse initial condition in all cases since our dense initial condition together with the algorithm utilizes the properties of the underlying architecture. Therefore, greater performance gain can be achieved (up to 18 times speedup compared to the sparse initial condition on GPU). Additionally, we have validated our concept against numerically approximated LS evolution of standard flows (mean curvature, Chan-Vese, geodesic active regions). The dice indexes between the fast LS evolutions and the evolutions of the numerically approximated partial differential equations are in the range of 0.99±0.003.

  15. The source of elliptic flow and initial conditions for hydrodynamical calculations

    SciTech Connect

    Strottman, D.; Csernai, L.; Magas, V.

    2000-08-01

    A model for energy, pressure and flow velocity distributions at the beginning of relativistic heavy ion collisions is presented, which can be used as initial condition for hydrodynamical calculations. The results show that QGP forms a tilted disk, such that the direction of the largest pressure gradient stays in the reaction plane, but deviates from both the beam and the usual transverse flow directions. Such initial condition may lead to the creation of antiflow or third flow component.

  16. Initial conditioning of polymer eelectrolyte membrane fuel cell by temperature and potential cycling.

    PubMed

    Bezmalinović, Dario; Radošević, Jagoda; Barbir, Frano

    2015-01-01

    Polymer electrolyte membrane fuel cells need initial conditioning, activation or break-in the first time they are operated after being assembled. During this period performance of the fuel cell improves until it reaches its nominal performance. The exact mechanism of this initial conditioning is not completely understood, but it is assumed that during the conditioning process the polymer membrane, as well as the polymer in the catalyst layer, get humidified, and the number of active catalyst sites increases. Activation procedure proposed here consists of temperature and potential cycling. Temperature cycling is a new approach for the conditioning and the idea is to rapidly cool the running cell at some point to allow the membrane to equilibrate with condensed water which should result in higher intake of water within the membrane. The results show that proposed procedure is better or at least comparable to some conventional procedures for the initial conditioning. PMID:25830963

  17. Impact of in-consistency between the climate model and its initial conditions on climate prediction

    NASA Astrophysics Data System (ADS)

    Liu, Xueyuan; Köhl, Armin; Stammer, Detlef; Masuda, Shuhei; Ishikawa, Yoichi; Mochizuki, Takashi

    2016-05-01

    We investigated the influence of dynamical in-consistency of initial conditions on the predictive skill of decadal climate predictions. The investigation builds on the fully coupled global model "Coupled GCM for Earth Simulator" (CFES). In two separate experiments, the ocean component of the coupled model is full-field initialized with two different initial fields from either the same coupled model CFES or the GECCO2 Ocean Synthesis while the atmosphere is initialized from CFES in both cases. Differences between both experiments show that higher SST forecast skill is obtained when initializing with coupled data assimilation initial conditions (CIH) instead of those from GECCO2 (GIH), with the most significant difference in skill obtained over the tropical Pacific at lead year one. High predictive skill of SST over the tropical Pacific seen in CIH reflects the good reproduction of El Niño events at lead year one. In contrast, GIH produces additional erroneous El Niño events. The tropical Pacific skill differences between both runs can be rationalized in terms of the zonal momentum balance between the wind stress and pressure gradient force, which characterizes the upper equatorial Pacific. In GIH, the differences between the oceanic and atmospheric state at initial time leads to imbalance between the zonal wind stress and pressure gradient force over the equatorial Pacific, which leads to the additional pseudo El Niño events and explains reduced predictive skill. The balance can be reestablished if anomaly initialization strategy is applied with GECCO2 initial conditions and improved predictive skill in the tropical Pacific is observed at lead year one. However, initializing the coupled model with self-consistent initial conditions leads to the highest skill of climate prediction in the tropical Pacific by preserving the momentum balance between zonal wind stress and pressure gradient force along the equatorial Pacific.

  18. The Effect of Spray Initial Conditions on Heat Release and Emissions in LDI CFD Calculations

    NASA Technical Reports Server (NTRS)

    Iannetti, Anthony C.; Liu, Nan-Suey; Davoudzadeh, Farhad

    2008-01-01

    The mass and velocity distribution of liquid spray has a primary effect on the combustion heat release process. This heat release process then affects emissions like nitrogen oxides (NOx) and carbon monoxide (CO). Computational Fluid Dynamics gives the engineer insight into these processes, but various setup options exist (number of droplet groups, and initial droplet temperature) for spray initial conditions. This paper studies these spray initial condition options using the National Combustion Code (NCC) on a single swirler lean direct injection (LDI) flame tube. Using laminar finite rate chemistry, comparisons are made against experimental data for velocity measurements, temperature, and emissions (NOx, CO).

  19. A no hair theorem and the problem of initial conditions. [in cosmological model

    NASA Technical Reports Server (NTRS)

    Jensen, Lars Gerhard; Stein-Schabes, Jaime A.

    1987-01-01

    It is shown that under very general conditions, any inhomogeneous cosmological model with a positive cosmological constant that can be described in a synchronous reference system will tend asymptotically in time towards the de Sitter solution. This renders the problem of initial conditions less severe.

  20. Correcting the initialization of models with fractional derivatives via history-dependent conditions

    NASA Astrophysics Data System (ADS)

    Du, Maolin; Wang, Zaihua

    2016-04-01

    Fractional differential equations are more and more used in modeling memory (history-dependent, non-local, or hereditary) phenomena. Conventional initial values of fractional differential equations are defined at a point, while recent works define initial conditions over histories. We prove that the conventional initialization of fractional differential equations with a Riemann-Liouville derivative is wrong with a simple counter-example. The initial values were assumed to be arbitrarily given for a typical fractional differential equation, but we find one of these values can only be zero. We show that fractional differential equations are of infinite dimensions, and the initial conditions, initial histories, are defined as functions over intervals. We obtain the equivalent integral equation for Caputo case. With a simple fractional model of materials, we illustrate that the recovery behavior is correct with the initial creep history, but is wrong with initial values at the starting point of the recovery. We demonstrate the application of initial history by solving a forced fractional Lorenz system numerically.

  1. The influence of initial and surface boundary conditions on a model-generated January climatology

    NASA Technical Reports Server (NTRS)

    Wu, K. F.; Spar, J.

    1981-01-01

    The influence on a model-generated January climate of various surface boundary conditions, as well as initial conditions, was studied by using the GISS coarse-mesh climate model. Four experiments - two with water planets, one with flat continents, and one with mountains - were used to investigate the effects of initial conditions, and the thermal and dynamical effects of the surface on the model generated-climate. However, climatological mean zonal-symmetric sea surface temperature is used in all four runs over the model oceans. Moreover, zero ground wetness and uniform ground albedo except for snow are used in the last experiments.

  2. Investigation into the Role of Initial Conditions on Rayleigh-Taylor Instabilities by Low Atwood Experiments and Simulations

    SciTech Connect

    Mueschke, N; Andrews, M; Schilling, O

    2003-07-14

    The primary goal of the research being conducted this summer is to investigate the role of initial conditions in the development of a two fluid mix driven by Rayleigh-Taylor instability. The effects of initial conditions will be studied through the use of experimental facilities located at the Buoyancy-Driven Mixing Lab at Texas A&M University and through high resolution direct numerical simulations of the experiment by the MIRANDA code developed at Lawrence Livermore National Lab. The Experimental Objectives are: (1) Analyze the early time development of a two fluid Rayleigh-Taylor driven mix between two miscible fluids at low Atwood numbers. (2) Quantify the initial conditions of the unstably stratified fluids by means of statistical mixing parameters and spectral analysis of the centerline density fluctuations. (3) Capture PLIF images of initial development of the flow for use in simulation setup. (Wayne Kraft) (4) Determine exactly what component of the experimental mixing data (position downstream from the splitter plate) most accurately represents the initial conditions of the experiment. The Simulation Objectives are: (1) Perform two dimensional and three dimensional simulations of the experimental setup. Analyze the results of these simulations for comparison to the experimental results. (2) Various methods of implementing the initial conditions in the simulations are to be investigated. Some of those methods are: (a) Various simplified density profile assumptions will also be investigated, such as repeating saw-teeth patterns, etc. There is also a concern to add some degree of randomness to these simplified perturbation profile assumptions. (b) Convert portions of raw PLIF data to a set of parameterized surfaces that can be directly input as both two dimensional and three dimensional surfaces. (c) Determine and implement a method for directly converting the initial density spectral data into a density profile that can be implemented in two and three

  3. Accurate coarse-grained models for mixtures of colloids and linear polymers under good-solvent conditions

    SciTech Connect

    D’Adamo, Giuseppe; Pelissetto, Andrea; Pierleoni, Carlo

    2014-12-28

    A coarse-graining strategy, previously developed for polymer solutions, is extended here to mixtures of linear polymers and hard-sphere colloids. In this approach, groups of monomers are mapped onto a single pseudoatom (a blob) and the effective blob-blob interactions are obtained by requiring the model to reproduce some large-scale structural properties in the zero-density limit. We show that an accurate parametrization of the polymer-colloid interactions is obtained by simply introducing pair potentials between blobs and colloids. For the coarse-grained (CG) model in which polymers are modelled as four-blob chains (tetramers), the pair potentials are determined by means of the iterative Boltzmann inversion scheme, taking full-monomer (FM) pair correlation functions at zero-density as targets. For a larger number n of blobs, pair potentials are determined by using a simple transferability assumption based on the polymer self-similarity. We validate the model by comparing its predictions with full-monomer results for the interfacial properties of polymer solutions in the presence of a single colloid and for thermodynamic and structural properties in the homogeneous phase at finite polymer and colloid density. The tetramer model is quite accurate for q ≲ 1 (q=R{sup ^}{sub g}/R{sub c}, where R{sup ^}{sub g} is the zero-density polymer radius of gyration and R{sub c} is the colloid radius) and reasonably good also for q = 2. For q = 2, an accurate coarse-grained description is obtained by using the n = 10 blob model. We also compare our results with those obtained by using single-blob models with state-dependent potentials.

  4. Sensitivity of soil moisture initialization for decadal predictions under different regional climatic conditions in Europe

    NASA Astrophysics Data System (ADS)

    Khodayar, S.; Sehlinger, A.; Feldmann, H.; Kottmeier, C.

    2015-12-01

    The impact of soil initialization is investigated through perturbation simulations with the regional climate model COSMO-CLM. The focus of the investigation is to assess the sensitivity of simulated extreme periods, dry and wet, to soil moisture initialization in different climatic regions over Europe and to establish the necessary spin up time within the framework of decadal predictions for these regions. Sensitivity experiments consisted of a reference simulation from 1968 to 1999 and 5 simulations from 1972 to 1983. The Effective Drought Index (EDI) is used to select and quantify drought status in the reference run to establish the simulation time period for the sensitivity experiments. Different soil initialization procedures are investigated. The sensitivity of the decadal predictions to soil moisture initial conditions is investigated through the analysis of water cycle components' (WCC) variability. In an episodic time scale the local effects of soil moisture on the boundary-layer and the propagated effects on the large-scale dynamics are analysed. The results show: (a) COSMO-CLM reproduces the observed features of the drought index. (b) Soil moisture initialization exerts a relevant impact on WCC, e.g., precipitation distribution and intensity. (c) Regional characteristics strongly impact the response of the WCC. Precipitation and evapotranspiration deviations are larger for humid regions. (d) The initial soil conditions (wet/dry), the regional characteristics (humid/dry) and the annual period (wet/dry) play a key role in the time that soil needs to restore quasi-equilibrium and the impact on the atmospheric conditions. Humid areas, and for all regions, a humid initialization, exhibit shorter spin up times, also soil reacts more sensitive when initialised during dry periods. (e) The initial soil perturbation may markedly modify atmospheric pressure field, wind circulation systems and atmospheric water vapour distribution affecting atmospheric stability

  5. On the Impact of Uncertainty in Initial Conditions of Hydrologic Models on Prediction

    NASA Astrophysics Data System (ADS)

    Razavi, S.; Sheikholeslami, R.

    2015-12-01

    Determining the initial conditions for predictive models remains a challenge due to the uncertainty in measurement/identification of the state variables at the scale of interest. However, the characterization of uncertainty in initial conditions has arguably attracted less attention compared with other sources of uncertainty in hydrologic modelling (e.g, parameter, data, and structural uncertainty). This is perhaps because it is commonly believed that: (1) hydrologic systems (relatively rapidly) forget their initial conditions over time, and (2) other sources of uncertainty (e.g., in data) are dominant. This presentation revisits the basic principles of the theory of nonlinear dynamical systems in the context of hydrologic systems. Through simple example case studies, we demonstrate how and under what circumstances different hydrologic processes represent a range of attracting limit sets in their evolution trajectory in state space over time, including fixed points, limit cycles (periodic behaviour), torus (quasi-periodic behaviour), and strange attractors (chaotic behaviour). Furthermore, the propagation (or dissipation) of uncertainty in initial conditions of several hydrologic models through time, under any of the possible attracting limit sets, is investigated. This study highlights that there are definite situations in hydrology where uncertainty in initial conditions remains of significance. The results and insights gained have important implications for hydrologic modelling under non-stationarity in climate and environment.

  6. Use of an Accurate DNS Particulate Flow Method to Supply and Validate Boundary Conditions for the MFIX Code

    SciTech Connect

    Zhi-Gang Feng

    2012-05-31

    The simulation of particulate flows for industrial applications often requires the use of two-fluid models, where the solid particles are considered as a separate continuous phase. One of the underlining uncertainties in the use of the two-fluid models in multiphase computations comes from the boundary condition of the solid phase. Typically, the gas or liquid fluid boundary condition at a solid wall is the so called no-slip condition, which has been widely accepted to be valid for single-phase fluid dynamics provided that the Knudsen number is low. However, the boundary condition for the solid phase is not well understood. The no-slip condition at a solid boundary is not a valid assumption for the solid phase. Instead, several researchers advocate a slip condition as a more appropriate boundary condition. However, the question on the selection of an exact slip length or a slip velocity coefficient is still unanswered. Experimental or numerical simulation data are needed in order to determinate the slip boundary condition that is applicable to a two-fluid model. The goal of this project is to improve the performance and accuracy of the boundary conditions used in two-fluid models such as the MFIX code, which is frequently used in multiphase flow simulations. The specific objectives of the project are to use first principles embedded in a validated Direct Numerical Simulation particulate flow numerical program, which uses the Immersed Boundary method (DNS-IB) and the Direct Forcing scheme in order to establish, modify and validate needed energy and momentum boundary conditions for the MFIX code. To achieve these objectives, we have developed a highly efficient DNS code and conducted numerical simulations to investigate the particle-wall and particle-particle interactions in particulate flows. Most of our research findings have been reported in major conferences and archived journals, which are listed in Section 7 of this report. In this report, we will present a

  7. Simple model of laser damage initiation and conditioning in frequency conversion crystals

    SciTech Connect

    Feit, M D; Rubenchik, A M; Trenholme, J B

    2005-10-28

    Laser conditioning, i.e. pre-exposure to less than damaging laser fluence, has been shown to improve the damage resistance of KDP/DKDP frequency conversion crystals. We have extended our damage model, small absorbing precursors with a distribution of sizes, to describe various damage related properties such as damage density and effects of laser conditioning in crystals. The model assumes the rate limiting process for both initiation and conditioning depends on temperature and that separate threshold temperatures exist for either conditioning or damage initiation to occur. This is reasonable in KDP/DKDP since the melting temperature is far below the temperatures associated with plasma formation and damage events. This model is capable of accounting for some recently observed damage-conditioning behaviors.

  8. What are the required conditions to trigger the obduction/subduction initiation?

    NASA Astrophysics Data System (ADS)

    Yamato, Philippe; Duretz, Thibault; Agard, Philippe; Soret, Mathieu

    2016-04-01

    The initial stages allowing for the birth of obduction and/or subduction zones still remain enigmatic and highly debated. Although there is no doubt that initiation occurs on a preexisting lithospheric-scale thermal or mechanical discontinuity (e.g., ridge, supra-subduction zone or transform fault), no consensus has yet been reached on this subject. However, more and more data allowing to address this issue are available (coming from field analyses, metamorphic petrology and geochronology). In particular, metamorphic soles located at the base of ophiolitic nappes, which formed during the very first stages of initiation, yield increasingly precise P-T-t constraints. By confronting such data to thermo-mechanical models, it should be possible to identify which initial configuration allows for metamorphic sole formation and for the emplacement (or not) of an ophiolitic nappe of realistic dimensions. In this study we designed thermo-mechanical models encompassing three initial model configurations, for which P-T-t data from the Semail ophiolite of Oman are then used for the validation of model outputs. The first configuration encompasses an oceanic ridge type initial thermal perturbation (error function). The second configuration mimics the thermal perturbation caused by the arrival of a mantle plume at the base of the lithosphere (gaussian function). The third initial condition corresponds to a case where the obduction/subduction initiates along a transform fault delimitating lithospheres of contrasting thermal ages (step function). Our results show that obduction never initiates in ridge type models, excepted for particular conditions that are not compatible with the Oman case. They also indicate that the initial thermal anomaly has to be sharp but not necessary of large amplitude and that the strength of the lithosphere has to be high enough to ensure the establishment of thin and long ophiolitic nappe without buckling. Our results also highlight the key role of

  9. Controlling Chaos Via Knowledge of Initial Condition for a Curved Structure

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    2000-01-01

    Nonlinear response of a flexible curved panel exhibiting bifurcation to fully developed chaos is demonstrated along with the sensitivity to small perturbation from the initial conditions. The response is determined from the measured time series at two fixed points. The panel is forced by an external nonharmonic multifrequency and monofrequency sound field. Using a low power time-continuous feedback control, carefully tuned at each initial condition, produces large long-term effects on the dynamics toward taming chaos. Without the knowledge of the initial conditions, control may be achieved by destructive interference. In this case, the control power is proportional to the loading power. Calculation of the correlation dimension and the estimation of positive Lyapunov exponents, in practice, are the proof of chaotic response.

  10. An Investigation of the Influence of Initial Conditions on Rayleigh-Taylor Mixing

    SciTech Connect

    Mueschke, Nicholas J.

    2004-12-01

    Experiments and direct numerical simulations (DNS) have been performed to examine the effects of initial conditions on the dynamics of a Rayleigh-Taylor unstable mixing layer. Experiments were performed on a water channel facility to measure the interfacial and velocity perturbations initially present at the two-fluid interface in a small Atwood number mixing layer. The experimental measurements have been parameterized for use in numerical simulations of the experiment. Two- and three-dimensional DNS of the experiment have been performed using the parameterized initial conditions. It is shown that simulations implemented with initial velocity and density perturbations, rather than density perturbations alone, are required to match experimentally-measured statistics and spectra. Data acquired from both the experiment and numerical simulations are used to examine the role of initial conditions on the evolution of integral-scale, turbulence, and mixing statistics. Early-time turbulence and mixing statistics are shown to be strongly-dependent upon the early-time transition of the initial perturbation from a weakly-nonlinear to a strongly-nonlinear flow.

  11. 3-D simulations to investigate initial condition effects on the growth of Rayleigh-Taylor mixing

    SciTech Connect

    Andrews, Malcolm J

    2008-01-01

    The effect of initial conditions on the growth rate of turbulent Rayleigh-Taylor (RT) mixing has been studied using carefully formulated numerical simulations. An integrated large-eddy simulation (ILES) that uses a finite-volume technique was employed to solve the three-dimensional incompressible Euler equations with numerical dissipation. The initial conditions were chosen to test the dependence of the RT growth parameters ({alpha}{sub b}, {alpha}{sub s}) on variations in (a) the spectral bandwidth, (b) the spectral shape, and (c) discrete banded spectra. Our findings support the notion that the overall growth of the RT mixing is strongly dependent on initial conditions. Variation in spectral shapes and bandwidths are found to have a complex effect of the late time development of the RT mixing layer, and raise the question of whether we can design RT transition and turbulence based on our choice of initial conditions. In addition, our results provide a useful database for the initialization and development of closures describing RT transition and turbulence.

  12. Bayesian inference of the initial conditions from large-scale structure surveys

    NASA Astrophysics Data System (ADS)

    Leclercq, Florent

    2016-10-01

    Analysis of three-dimensional cosmological surveys has the potential to answer outstanding questions on the initial conditions from which structure appeared, and therefore on the very high energy physics at play in the early Universe. We report on recently proposed statistical data analysis methods designed to study the primordial large-scale structure via physical inference of the initial conditions in a fully Bayesian framework, and applications to the Sloan Digital Sky Survey data release 7. We illustrate how this approach led to a detailed characterization of the dynamic cosmic web underlying the observed galaxy distribution, based on the tidal environment.

  13. Multi-initial-conditions and Multi-physics Ensembles in the Weather Research and Forecasting Model to Improve Coastal Stratocumulus Forecasts for Solar Power Integration

    NASA Astrophysics Data System (ADS)

    Yang, H.

    2015-12-01

    In coastal Southern California, variation in solar energy production is predominantly due to the presence of stratocumulus clouds (Sc), as they greatly attenuate surface solar irradiance and cover most distributed photovoltaic systems on summer mornings. Correct prediction of the spatial coverage and lifetime of coastal Sc is therefore vital to the accuracy of solar energy forecasts in California. In Weather Research and Forecasting (WRF) model simulations, underprediction of Sc inherent in the initial conditions directly leads to an underprediction of Sc in the resulting forecasts. Hence, preprocessing methods were developed to create initial conditions more consistent with observational data and reduce spin-up time requirements. Mathiesen et al. (2014) previously developed a cloud data assimilation system to force WRF initial conditions to contain cloud liquid water based on CIMSS GOES Sounder cloud cover. The Well-mixed Preprocessor and Cloud Data Assimilation (WEMPPDA) package merges an initial guess of cloud liquid water content obtained from mixed-layer theory with assimilated CIMSS GOES Sounder cloud cover to more accurately represent the spatial coverage of Sc at initialization. The extent of Sc inland penetration is often constrained topographically; therefore, the low inversion base height (IBH) bias in NAM initial conditions decreases Sc inland penetration. The Inversion Base Height (IBH) package perturbs the initial IBH by the difference between model IBH and the 12Z radiosonde measurement. The performance of these multi-initial-condition configurations was evaluated over June, 2013 against SolarAnywhere satellite-derived surface irradiance data. Four configurations were run: 1) NAM initial conditions, 2) RAP initial conditions, 3) WEMPPDA applied to NAM, and 4) IBH applied to NAM. Both preprocessing methods showed significant improvement in the prediction of both spatial coverage and lifetime of coastal Sc. The best performing configuration was then

  14. Effect of initial conditions and Mach number on the Richtmyer-Meshkov instability in ICF like conditions

    NASA Astrophysics Data System (ADS)

    Rao, Pooja; She, Dan; Lim, Hyunkyung; Glimm, James

    2015-11-01

    The qualitative and quantitative effect of initial conditions (linear and non-linear) and high Mach number (1.3 and 1.45) is studied on the turbulent mixing induced by the Richtmyer-Meshkov instability in idealized ICF conditions. The Richtmyer-Meshkov instability seeds Rayleigh-taylor instabilities in ICF experiments and is one of the factors that contributes to reduced performance of ICF experiments. Its also found in collapsing cores of stars and supersonic combustion. We use the Stony Brook University code, FronTier, which is verified via a code comparison study against the AMR multiphysics code FLASH, and validated against vertical shock tube experiments done by the LANL Extreme Fluids Team. These simulations are designed as a step towards simulating more realistic ICF conditions and quantifying the detrimental effects of mixing on the yield.

  15. A new way of setting the phases for cosmological multiscale Gaussian initial conditions

    NASA Astrophysics Data System (ADS)

    Jenkins, Adrian

    2013-09-01

    We describe how to define an extremely large discrete realization of a Gaussian white noise field that has a hierarchical structure and the property that the value of any part of the field can be computed quickly. Tiny subregions of such a field can be used to set the phase information for Gaussian initial conditions for individual cosmological simulations of structure formation. This approach has several attractive features: (i) the hierarchical structure based on an octree is particularly well suited for generating follow-up resimulation or zoom initial conditions; (ii) the phases are defined for all relevant physical scales in advance so that resimulation initial conditions are, by construction, consistent both with their parent simulation and with each other; (iii) the field can easily be made public by releasing a code to compute it - once public, phase information can be shared or published by specifying a spatial location within the realization. In this paper, we describe the principles behind creating such realizations. We define an example called Panphasia and in a companion paper by Jenkins and Booth (2013) make public a code to compute it. With 50 octree levels Panphasia spans a factor of more than 1015 in linear scale - a range that significantly exceeds the ratio of the current Hubble radius to the putative cold dark matter free-streaming scale. We show how to modify a code used for making cosmological and resimulation initial conditions so that it can take the phase information from Panphasia and, using this code, we demonstrate that it is possible to make good quality resimulation initial conditions. We define a convention for publishing phase information from Panphasia and publish the initial phases for several of the Virgo Consortium's most recent cosmological simulations including the 303 billion particle MXXL simulation. Finally, for reference, we give the locations and properties of several dark matter haloes that can be resimulated within these

  16. Initial and sustained brain responses to contextual conditioned anxiety in humans.

    PubMed

    Andreatta, Marta; Glotzbach-Schoon, Evelyn; Mühlberger, Andreas; Schulz, Stefan M; Wiemer, Julian; Pauli, Paul

    2015-02-01

    Contextual fear conditioning takes place if the occurrence of threat cannot be predicted by specific cues. As a consequence the context becomes the best predictor of the threat and later induces anxiety (sustained fear response). Previous studies suggest that both the amygdala and the hippocampus are crucial for contextual fear conditioning. First, we wanted to further elucidate the neuronal correlates of long-lasting contextual threat within a highly ecologically setting created in virtual reality (VR). Second, we wanted to distinguish between initial and sustained components of the anxiety response to a threatening situation. Twenty-four participants were guided through two virtual offices for 30s each. They received unpredictable electric stimuli (unconditioned stimulus, US) in one office (anxiety context, CXT+), but never in the second office (safety context, CXT-). Successful contextual fear conditioning was indexed by higher anxiety and enhanced US-expectancy ratings for CXT+ versus CXT-. Initial neural activity was assessed by modeling the onsets of both contexts, and sustained neural activity by considering the entire context duration (contrasts: CXT+ > CXT-). Amygdala and hippocampus revealed sustained activity. Initial and sustained activities were found in the middle temporal gyrus, and primary motor cortex (M1). Additional initial activity was obvious in orbitofrontal (OFC), dorsomedial (dmPFC), and dorsolateral prefrontal cortex (dlPFC). These results suggest that entering a threatening context initially induces conditioned fear reactions (M1), recall of contingency awareness (dlPFC), and explicit threat appraisal (dmPFC, OFC). While remaining in the threatening context might involve anxiety-like conditioned responses (amygdala, M1) and the generation of a spatial map to predict where and when a threatening event may occur (hippocampus). We conclude that in humans initial versus sustained anxiety responses triggered by a threat associated context

  17. Initial adhesion of Listeria monocytogenes to fine polished stainless steel under flow conditions is determined by prior growth conditions.

    PubMed

    Skovager, Anne; Larsen, Marianne Halberg; Castro-Mejia, Josue Leonardo; Hecker, Michael; Albrecht, Dirk; Gerth, Ulf; Arneborg, Nils; Ingmer, Hanne

    2013-07-01

    Listeria monocytogenes is a food-borne pathogen known to persist in food production environments, where it is able to attach and form biofilms, potentially contaminating food products ready for consumption. In this study the first step in the establishment of L. monocytogenes in a food-processing environment was examined, namely the initial adhesion to stainless steel under specific dynamic flow conditions. It was found that the intrinsic ability of L. monocytogenes to adhere to solid surfaces under flow conditions is dependent on nutrient availability. The addition of L-leucine to the growth medium altered the fatty acid composition of the L. monocytogenes cells and increased adhesion. The growth conditions resulting in the highest adhesion (growth medium with added glucose) had cells with the highest electron donating and lowest electron accepting properties, whereas growth conditions resulting in lowest adhesion (growth medium with added mannose) had cells with the lowest electron donating properties and highest electron accepting properties. The highest and lowest adhesion conditions correlated with differences in expression of cell surface protein of L. monocytogenes and among these the autolysin amidase (Ami). This study implies that food composition influences the adhesion of L. monocytogenes to solid surfaces during dynamic flow conditions.

  18. Appropriate solid-body models as initial conditions for SPH-based numerical collision experiments

    NASA Astrophysics Data System (ADS)

    Burger, C.; Maindl, T. I.; Dvorak, R.; Schäfer, C.; Speith, R.

    2016-02-01

    Providing the simulation algorithm with suitable initial conditions is a crucial first step in almost all numerical computations, except for the most trivial cases. Even the most sophisticated simulation program will not produce meaningful results if not started with an appropriate initial configuration, satisfying demands like isotropy, a low level of noise and physical accuracy. Some of these requirements are unique to Smoothed Particle Hydrodynamics (SPH) - the numerical method considered here - others are of fundamental relevance, independent of the chosen numerical technique. The main focus of this work lies on considerations concerning initial conditions for subsequent SPH simulation runs. The geometrical arrangement of an initial SPH particle setup is discussed, particularly w.r.t. regular lattice configurations and associated symmetry effects. In order to avoid unphysical behavior the initial particle configuration has to be in a relaxed (i.e. equilibrated) state where necessary. This is of particular importance for simulations of giant collisions, where the involved bodies naturally exhibit a hydrostatic internal structure. Beyond the common numerical procedure, a semi-analytical approach for relaxation is introduced and validated, practically eliminating the need for spending significant amounts of valuable computing time solely for the production of a relaxed initial state in a lot of situations. Finally the basic relevance of relaxation itself is studied, focusing on collision simulations in different mass ranges important in the context of planet formation and the transport of water.

  19. The dependence of star formation on initial conditions and molecular cloud structure

    NASA Astrophysics Data System (ADS)

    Bate, Matthew R.

    2009-07-01

    We investigate the dependence of stellar properties on the initial kinematic structure of the gas in star-forming molecular clouds. We compare the results from two large-scale hydrodynamical simulations of star cluster formation that resolve the fragmentation process down to the opacity limit, the first of which was reported by Bate, Bonnell & Bromm. The initial conditions of the two calculations are identical, but in the new simulation the power spectrum of the velocity field imposed on the cloud initially and allowed to decay is biased in favour of large-scale motions. Whereas the calculation of Bate et al. began with a power spectrum P(k) ~ k-4 to match the Larson scaling relations for the turbulent motions observed in molecular clouds, the new calculation begins with a power spectrum P(k) ~ k-6. Despite this change to the initial motions in the cloud and the resulting density structure of the molecular cloud, the stellar properties resulting from the two calculations are indistinguishable. This demonstrates that the results of such hydrodynamical calculations of star cluster formation are relatively insensitive to the initial conditions. It is also consistent with the fact that the statistical properties of stars and brown dwarfs (e.g. the stellar initial mass function) are observed to be relatively invariant within our Galaxy and do not appear to depend on environment.

  20. The Impact of Initial Conditions in N-Body Simulations of Debris Discs

    NASA Astrophysics Data System (ADS)

    Thilliez, E.; Maddison, S. T.

    2015-10-01

    Numerical simulations are a crucial tool to understand the relationship between debris discs and planetary companions. As debris disc observations are now reaching unprecedented levels of precision over a wide range of wavelengths, an appropriate level of accuracy and consistency is required in numerical simulations to confidently interpret this new generation of observations. However, simulations throughout the literature have been conducted with various initial conditions often with little or no justification. In this paper, we aim to study the dependence on the initial conditions of N-body simulations modelling the interaction between a massive and eccentric planet on an exterior debris disc. To achieve this, we first classify three broad approaches used in the literature and provide some physical context for when each category should be used. We then run a series of N-body simulations, that include radiation forces acting on small grains, with varying initial conditions across the three categories. We test the influence of the initial parent body belt width, eccentricity, and alignment with the planet on the resulting debris disc structure and compare the final peak emission location, disc width and offset of synthetic disc images produced with a radiative transfer code. We also track the evolution of the forced eccentricity of the dust grains induced by the planet, as well as resonance dust trapping. We find that an initially broad parent body belt always results in a broader debris disc than an initially narrow parent body belt. While simulations with a parent body belt with low initial eccentricity (e ~ 0) and high initial eccentricity (0 < e < 0.3) resulted in similar broad discs, we find that purely secular forced initial conditions, where the initial disc eccentricity is set to the forced value and the disc is aligned with the planet, always result in a narrower disc. We conclude that broad debris discs can be modelled by using either a dynamically cold

  1. Comments on initial conditions for the Abraham-Lorentz(-Dirac) equation

    NASA Astrophysics Data System (ADS)

    Birnholtz, Ofek

    2015-01-01

    An accelerating electric charge coupled to its own electromagnetic field both emits radiation and experiences the radiation's reaction as a (self-)force. Considering the system from an Effective Field Theory perspective, and using the physical initial conditions of no incoming radiation can help resolve many of the problems associated with the often considered "notorious" Abraham-Lorentz/Abraham-Lorentz-Dirac equations.

  2. Predicting a contact's sensitivity to initial conditions using metrics of frictional coupling

    DOE PAGES

    Flicek, Robert C.; Hills, David A.; Brake, Matthew Robert W.

    2016-09-29

    This paper presents a method for predicting how sensitive a frictional contact’s steady-state behavior is to its initial conditions. Previous research has proven that if a contact is uncoupled, i.e. if slip displacements do not influence the contact pressure distribution, then its steady-state response is independent of initial conditions, but if the contact is coupled, the steady-state response depends on initial conditions. In this paper, two metrics for quantifying coupling in discrete frictional systems are examined. These metrics suggest that coupling is dominated by material dissimilarity due to Dundurs’ composite material parameter β when β ≥ 0.2, but geometric mismatchmore » becomes the dominant source of coupling for smaller values of β. Based on a large set of numerical simulations with different contact geometries, material combinations, and friction coefficients, a contact’s sensitivity to initial conditions is found to be correlated with the product of the coupling metric and the friction coefficient. For cyclic shear loading, this correlation is maintained for simulations with different contact geometries, material combinations, and friction coefficients. Furthermore, for cyclic bulk loading, the correlation is only maintained when the contact edge angle is held constant.« less

  3. Model Forecast Skill and Sensitivity to Initial Conditions in the Seasonal Sea Ice Outlook

    NASA Technical Reports Server (NTRS)

    Blanchard-Wrigglesworth, E.; Cullather, R. I.; Wang, W.; Zhang, J.; Bitz, C. M.

    2015-01-01

    We explore the skill of predictions of September Arctic sea ice extent from dynamical models participating in the Sea Ice Outlook (SIO). Forecasts submitted in August, at roughly 2 month lead times, are skillful. However, skill is lower in forecasts submitted to SIO, which began in 2008, than in hindcasts (retrospective forecasts) of the last few decades. The multimodel mean SIO predictions offer slightly higher skill than the single-model SIO predictions, but neither beats a damped persistence forecast at longer than 2 month lead times. The models are largely unsuccessful at predicting each other, indicating a large difference in model physics and/or initial conditions. Motivated by this, we perform an initial condition sensitivity experiment with four SIO models, applying a fixed -1 m perturbation to the initial sea ice thickness. The significant range of the response among the models suggests that different model physics make a significant contribution to forecast uncertainty.

  4. Relating seasonal streamflow forecast skill to uncertainties in initial conditions, future forcings, and hydrologic modeling

    NASA Astrophysics Data System (ADS)

    Wood, A. W.; Hopson, T. M.; Newman, A. J.; Sampson, K. M.; Brekke, L. D.; Arnold, J.; Raff, D. A.; Clark, M. P.

    2013-12-01

    Skill in model-based hydrologic forecasting depends on the ability to estimate a watershed's initial moisture and energy conditions, to forecast future weather and climate inputs, and on the quality of the hydrologic model's representation of watershed processes. The impact of these factors on prediction skill varies regionally, seasonally, and by model. We investigate these influences in a series of predictability experiments using calibrated hydrologic simulation models for a 630-watershed dataset that spans the continental US (CONUS), and using the current major simulation models of National Weather Service streamflow forecasting operations. Earlier work in this area (Wood and Lettenmaier, GRL 2008) outlined an ensemble-based strategy for attributing streamflow forecast uncertainty between two endpoints representing zero information about future forcings (ie, the NWS ensemble streamflow prediction, or ESP approach) versus zero information about initial conditions (termed ';reverse-ESP'). This study adopts a more comprehensive approach to characterize the effects of varying levels of uncertainty, from zero knowledge to perfect information in the model world, on streamflow prediction uncertainty. Ensemble hindcasts reflecting varying levels of uncertainty are initialized on a monthly basis for the basins' periods of record, creating background sensitivity information that helps to decompose total hydrologic prediction error into the three components identified above. Observed streamflow prediction errors are then coupled with estimates of realistic uncertainties in future forcing and with model simulation error to infer initial condition errors. This presentation reports findings from the predictability experiments, summarizing the relative importance of uncertainties in basin initial conditions and weather and climate forecasts, and their dependence on forecast lead time, initiation date and regional hydroclimate characteristics.

  5. Effects of eddy initial conditions on nonlinear forcing of planetary scale waves by amplifying baroclinic eddies

    NASA Technical Reports Server (NTRS)

    Young, Richard E.

    1986-01-01

    The previous study of Young and Villere concerning growth of planetary scale waves forced by wave-wave interactions of amplifying intermediate scale baroclinic eddies is extended to investigate effects of different eddy initial conditions. A global, spectral, primitive equation model is used for the calculations. For every set of eddy initial conditions considered, growth rates of planetary modes are considerably greater than growth rates computed from linear instability theory for a fixed zonally independent basic state. However, values of growth rates ranged over a factor of 3 depending on the particular set of eddy initial conditions used. Nonlinear forcing of planetary modes via wave-wave coupling becomes more important than baroclinic growth on the basic state at small values of the intermediate-scale modal amplitudes. The relative importance of direct transfer of kinetic energy from intermediate scales of motion to a planetary mode, compared to baroclinic conversion of available potential energy to kinetic energy within that planetary mode, depends on the individual case. In all cases, however, the transfer of either kinetic or available potential energy to the planetary modes was accomplished principally by wave-wave transfer from intermediate scale eddies, rather than from the zonally averaged state. The zonal wavenumber 2 planetary mode was prominent in all solutions, even in those for which eddy initial conditions were such that a different planetary mode was selectively forced at the start. General characteristics of the structural evolution of the planetary wave components of total heat and momentum flux, and modal structures themselves, were relatively insensitive to variations in eddy initial conditions, even though quantitative details varied from case to case.

  6. An accurate treatment of diffuse reflection boundary conditions for a stochastic particle Fokker-Planck algorithm with large time steps

    NASA Astrophysics Data System (ADS)

    Önskog, Thomas; Zhang, Jun

    2015-12-01

    In this paper, we present a stochastic particle algorithm for the simulation of flows of wall-confined gases with diffuse reflection boundary conditions. Based on the theoretical observation that the change in location of the particles consists of a deterministic part and a Wiener process if the time scale is much larger than the relaxation time, a new estimate for the first hitting time at the boundary is obtained. This estimate facilitates the construction of an algorithm with large time steps for wall-confined flows. Numerical simulations verify that the proposed algorithm reproduces the correct boundary behaviour.

  7. Conditions for Circumstellar Disc Formation II: Effects of Initial Cloud Stability and Mass Accretion Rate

    NASA Astrophysics Data System (ADS)

    Machida, Masahiro N.; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    2016-09-01

    Disc formation in strongly magnetized cloud cores is investigated using a three-dimensional magnetohydrodynamic simulation with a focus on the effects of the initial cloud stability and the mass accretion rate. The initial cloud stability greatly alters the disc formation process even for prestellar clouds with the same mass-to-flux ratio. A high mass accretion rate onto the disc-forming region is realized in initially unstable clouds, and a large angular momentum is introduced into the circumstellar region in a short time. The region around the protostar has both a thin infalling envelope and a weak magnetic field, which both weaken the effect of magnetic braking. The growth of the rotation-supported disc is promoted in such unstable clouds. Conversely, clouds in an initially near-equilibrium state show lower accretion rates of mass and angular momentum. The angular momentum is transported to the outer envelope before protostar formation. After protostar formation, the circumstellar region has a thick infalling envelope and a strong magnetic field that effectively brake the disc. As a result, disc formation is suppressed when the initial cloud is in a nearly stable state. The density distribution of the initial cloud also affects the disc formation process. Disc growth strongly depends on the initial conditions when the prestellar cloud has a uniform density, whereas there is no significant difference in the disc formation process in prestellar clouds with nonuniform densities.

  8. A numerical method for computing initial conditions of Lagrangian invariant tori using the frequency map

    NASA Astrophysics Data System (ADS)

    Luque, Alejandro; Villanueva, Jordi

    2016-06-01

    We present a numerical method for computing initial conditions of Lagrangian quasi-periodic invariant tori of Hamiltonian systems and symplectic maps. Such initial conditions are found by solving, using the Newton method, a nonlinear system obtained by imposing suitable conditions on the frequency map. The basic tool is a newly developed methodology to perform the frequency analysis of a discrete quasi-periodic signal, allowing to compute frequencies and their derivatives with respect to parameters. Roughly speaking, this method consists in computing suitable weighted averages of the iterates of the signal and using the Richardson extrapolation method. The proposed approach performs with high accuracy at a moderate computational cost. We illustrate the method by considering a discrete FPU model and the vicinity of the point L4 in a RTBP.

  9. Kovalevskaya exponents and the space of initial conditions of a quasi-homogeneous vector field

    NASA Astrophysics Data System (ADS)

    Chiba, Hayato

    2015-12-01

    Formal series solutions and the Kovalevskaya exponents of a quasi-homogeneous polynomial system of differential equations are studied by means of a weighted projective space and dynamical systems theory. A necessary and sufficient condition for the series solution to be a convergent Laurent series is given, which improves the well-known Painlevé test. In particular, if a given system has the Painlevé property, an algorithm to construct Okamoto's space of initial conditions is given. The space of initial conditions is obtained by weighted blow-ups of the weighted projective space, where the weights for the blow-ups are determined by the Kovalevskaya exponents. The results are applied to the first Painlevé hierarchy (2m-th order first Painlevé equation).

  10. 3-D Time-Accurate CFD Simulations of a Multi-Megawatt Slender Bladed HAWT under Yawed Inflow Conditions

    NASA Astrophysics Data System (ADS)

    Sayed, M.; Lutz, Th.; Krämer, E.

    2016-09-01

    In the present study numerical investigations of a generic Multi-Megawatt slender bladed Horizontal-Axis Wind Turbine (HAWT) under yawed inflow conditions were conducted. A three-dimensional URANS flow solver based on structured overlapping meshes was used. The simulations were conducted at wind speeds of 7m/sec, 11 m/sec and 15 m/sec for different yaw angles ranging from +60° to -60°. It was concluded that, for below rated wind speeds, under small yaw angles (below ±15°) the magnitudes of the blade forces are slightly increased, while under high yaw angles (above ±15°) there is a significant decrease. Moreover, the load fluctuations, for the different yaw angles, have the same frequency but different amplitude and oscillation shape. It was concluded that at the above rated wind speed of 15 m/sec, the blade aerodynamic loads are significantly affected by the yaw inflow conditions and the magnitude values of the loads are decreased with increasing yaw angle. It can be concluded that the angle of attack and the tower interference are the utmost variables affecting the yawed turbines.

  11. Centrifuge model tests of rainfall-induced slope failures for the investigation of the initiation conditions

    NASA Astrophysics Data System (ADS)

    Matziaris, Vasileios; Marshall, Alec; Yu, Hai-Sui

    2015-04-01

    Rainfall-induced landslides are very common natural disasters which cause damage to properties and infrastructure and may result in the loss of human lives. These phenomena often take place in unsaturated soil slopes and are triggered by the saturation of the soil profile, due to rain infiltration, which leads to a loss of shear strength. The aim of this study is to determine rainfall thresholds for the initiation of landslides under different initial conditions. Model tests of rainfall-induced landslides are conducted in the Nottingham Centre for Geomechanics 50g-T geotechnical centrifuge. Initially unsaturated plane-strain slope models made with fine silica sand are prepared at varying densities at 1g and accommodated within a climatic chamber which provides controlled environmental conditions. During the centrifuge flight at 60g, rainfall events of varying intensity and duration are applied to the slope models causing the initiation of slope failure. The impact of soil state properties and rainfall characteristics on the landslide initiation process are discussed. The variation of pore water pressures within the slope before, during and after simulated rainfall events is recorded using miniature pore pressure transducers buried in the soil model. Slope deformation is determined by using a high-speed camera and digital image analysis techniques.

  12. The initial phase of fracture healing is specifically sensitive to mechanical conditions.

    PubMed

    Klein, Petra; Schell, Hanna; Streitparth, Florian; Heller, Markus; Kassi, Jean-Pierre; Kandziora, Frank; Bragulla, Hermann; Haas, Norbert P; Duda, Georg N

    2003-07-01

    Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.

  13. Spatial and Temporal Distribution of Initial 230TH/232TH in Sumatran Corals and its Influence on the Accurate Dating of Young Corals

    NASA Astrophysics Data System (ADS)

    Chiang, H.; Shen, C.; Meltzner, A. J.; Philibosian, B.; WU, C.; Sieh, K. E.; Wang, X.

    2012-12-01

    Accurate and precise determination of initial 230Th/232Th (230Th/232Th0) is important in dating young fossil corals, and it can significantly influence our understanding of paleoclimate, paleoceanographic and paleoseismic histories. A total of 47 unpublished and published isochrons (Shen et al., 2008; Meltzner et al., 2010, 2012; Philibosian et al., 2012), covering most of the Sumatran outer-arc islands, provide a more robust estimate of the 230Th/232Th0 variability in the region. The weighted average of 230Th/232Th0 atomic values is 4.7 (+5.5/-4.7) × 10-6 (2σ), consistent with the previously reported value of 6.5 ± 6.5 × 10-6 obtained from a handful of samples from the southern part of Sumatran outer-arc. Specifically, the calculated 230Th/232Th0 in the north and south are identical. The weighted mean of 3.5 (+7.0/-3.5) × 10-6 for fossil corals of 300-2000-yr old is slightly lower than the value of 5.4 ± 4.5 × 10-6 obtained from corals younger than 300 yrs B.P.. For corals containing less than 2 ppb of thorium, however, the age offset will be less than 10 yr by using different 230Th/232Th0, which is acceptable for most studies. We hereby recommend an updated 230Th/232Th0 value of 4.7 (+5.5/-4.7) × 10-6 for corals throughout the Sumatran outer-arc islands. For very high-precision age determination (<10 yr), coral samples with low Th concentration (< 2 ppb) are preferred.; ;

  14. Sensitivity of the structure of untripped mixing layers to small changes in initial conditions

    NASA Technical Reports Server (NTRS)

    Plesniak, M. W.; Bell, J. H.; Mehta, R. D.

    1992-01-01

    An experimental study was conducted concerning the influence of small changes in initial conditions on the near- and far-field evolution of the three-dimensional structure of a plan mixing layer. A two-stream mixing layer with a velocity ratio of 0.6 was generated with the initial boundary layers on the splitter plate laminar and was nominally two-dimensional. The initial conditions were changed slightly by interchanging the high- and low-speed sides of the wind tunnel, while maintaining the same velocities, and hence velocity ratio. This resulted in small changes in the initial boundary layer properties, and the perturbations present in the boundary layers were interchanged between the high- and low-speed sides for the two cases. The results indicate that, even with this relatively minor change in initial conditions, the near-field regions of the two cases differ significantly. The peak Reynolds stress levels in the near-field differ by up to 100 percent, and this is attributed to a difference in the location of the initial spanwise vortex roll-up. In addition, the positions and shapes of the individual streamwise vortical structures differ for the two cases, although the overall structures differ for the two cases, although the overall qualitative description of these structures is comparable. The subsequent reorganization and decay of the streamwise vortical structures is very similar for the two cases. As a result, in the far field, both mixing layers achieve similar structure, yielding comparable growth rates, Reynolds stress, distribution, and spectral content.

  15. Evaluation of the effects of initial conditions on transients in PUMA

    SciTech Connect

    Parlatan, Y.; Jo, J.; Rohatgi, U.S.

    1996-07-01

    Major differences between the SBWR and the currently operating BWRs include the use of passive gravity-driven systems in the SBWR for emergency cooling of the vessel and containment. In order to investigate the phenomena expected during a Loss of Coolant Accident (LOCA), NRC has sponsored an integral scaled-test facility, called Purdue, University Multidimensional Integral Test Assembly (PUMA). The facility models all the major safety-related components of SBWR. Two PUMA initialization calculations were performed to assist the Purdue University in establishing test initialization procedures. Both calculations were based on the initial conditions obtained from SBWR LOCA simulation. In the base case, a complete separation between vapor and liquid was assumed, with all the water in the lower part of the Reactor Pressure Vessel (RPV) and all the vapor above it. In the sensitivity case, the water inventory was distributed in the vessel in the same way as in the SBWR at 1.034 MPa, which is the initial pressure for PUMA facility. Purdue University plans to initialize the PUMA tests as in the base case. The sensitivity calculation is performed to provide assurance that this mode of initialization is adequate. It also provides information on possible differences in the progress of transients. The conditions outside of the vessel were identical for both cases prior to initiation of the accident. The paper will discuss the differences in the early part of the transient. The conclusion from this study will also apply to many integral facilities which simulate the reactor transients from the middle of the transient.

  16. Influence of initial conditions on the flow patterns of a shock-accelerated thin fluid layer

    SciTech Connect

    Budzinski, J.M.; Benjamin, R.F. ); Jacobs, J.W. )

    1994-11-01

    Previous observations of three flow patterns generated by shock acceleration of a thin perturbed, fluid layer are now correlated with asymmetries in the initial conditions. Using a different diagnostic (planar laser Rayleigh scattering) than the previous experiments, upstream mushrooms, downstream mushrooms, and sinuous patterns are still observed. For each experiment the initial perturbation amplitude on one side of the layer can either be larger, smaller, or the same as the amplitude on the other side, as observed with two images per experiment, and these differences lead to the formation of the different patterns.

  17. Effect of Initial Conditions on Compressible Rayleigh-Taylor Instability and Transition to Turbulence

    SciTech Connect

    Miles, A R; Edwards, M; Greenough, J A

    2004-01-07

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, we present the first results from a computational study of such a system under drive conditions to be attainable on the National Ignition Facility. Using the multiphysics, AMR, higher order Godunov Eulerian hydrocode, Raptor, we consider the late nonlinear instability evolution for multiple amplitude and phase realizations of a variety of multimode spectral types. We show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. The initial conditions are shown to have a strong affect on the time to transition to the quasi-self-similar regime.

  18. LETTER TO THE EDITOR: Accurate Hylleraas-like functions for the He atom with correct cusp conditions

    NASA Astrophysics Data System (ADS)

    Rodriguez, K. V.; Gasaneo, G.

    2005-08-01

    In this letter, a set of ground state wavefunctions for the He atom is given. The functions are constructed in terms of exponential and power series as similar as possible to the Hylleraas functions of Chandrasekhar and Herzberg (1955 Phys. Rev. 98 1050). The accuracy of the calculated energies is found to be about 10-4 au and all the cusp conditions at the Coulomb singularities are satisfied. The nine-parameter functions proposed here are found to have better local energy than those given by the 6 and 14 terms Hylleraas functions of Chandrasekhar. The mean value of various functions evaluated with the different proposals shows their good quality. These properties highly qualify the function to be used as an alternative to the Chandrasekhar functions in collisional problems. The whole set of functions given here can be considered as an alternative to the proposals of Chandrasekhar (1955 Phys. Rev. 98 1050), Bonham and Kohl (1966 J. Chem. Phys. 45 2471) and Le Sech (1997 J. Phys. B: At. Mol. Opt. Phys. 30 L47).

  19. ACCURATE TIME-DEPENDENT WAVE PACKET STUDY OF THE H{sup +}+LiH REACTION AT EARLY UNIVERSE CONDITIONS

    SciTech Connect

    Aslan, E.; Bulut, N.; Castillo, J. F.; Banares, L.; Aoiz, F. J.; Roncero, O.

    2012-11-01

    The dynamics and kinetics of the H{sup +} + LiH reaction have been studied using a quantum reactive time-dependent wave packet (TDWP) coupled-channel quantum mechanical method on an ab initio potential energy surface at conditions of the early universe. The total reaction probabilities for the H{sup +} + LiH(v = 0, j = 0) {yields} H{sup +} {sub 2} + Li process have been calculated from 5 Multiplication-Sign 10{sup -3} eV up to 1 eV for total angular momenta J from 0 to 110. Using a Langevin model, integral cross sections have been calculated in that range of collision energies and extrapolated for energies below 5 Multiplication-Sign 10{sup -3} eV. The calculated rate constants are found to be nearly independent of temperature in the 10-1000 K interval with a value of Almost-Equal-To 10{sup -9} cm{sup 3} s{sup -1}, which is in good agreement with estimates used in evolutionary models of the early universe lithium chemistry.

  20. Initial conditions influence the characteristics of ballistic contractions in the ankle dorsiflexors.

    PubMed

    Richartz, Chris; Lévénez, Morgan; Boucart, Julien; Duchateau, Jacques

    2010-11-01

    This study investigated the influence of different initial conditions on a subsequent fast (ballistic) isometric contraction of the ankle dorsiflexor muscles. Surface electromyograms (EMGs) of dorsiflexor and plantarflexor muscles were recorded during ballistic contractions performed without any pre-activation (BAL) and in ballistic contractions preceded by a sustained submaximal contraction (20% MVC) that was followed either by a rapid voluntary relaxation of the agonist muscle (VRBAL) or by a rapid antagonist (reversal) contraction (ARBAL). In the latter condition, three different antagonist torque levels were compared (25, 50 and 75% MVC). The results showed that the mean average rate of torque development was significantly (P < 0.001) greater for the ARBAL condition (968.5 ± 183.9% MVC/s) compared with the VRBAL (509.3 ± 78.7% MVC/s) and BAL (461.8 ± 79.9% MVC/s) conditions. Furthermore, the mean value recorded for VRBAL was significantly (P < 0.05) greater than for BAL condition. The faster increases in torque during the VRBAL and ARBAL conditions were associated with a greater agonist EMG activity. Compared with VRBAL, performance during the ARBAL condition was improved by a greater level of antagonist coactivation and, in some trials, by the presence of a silent EMG period between the end of the antagonist activation and the onset of the agonist ballistic contraction. Together, these results indicate that the initial conditions can have a substantial influence on the rate of torque development during ballistic contractions performed in isometric conditions.

  1. Dynamical ejections of massive stars from young star clusters under diverse initial conditions

    NASA Astrophysics Data System (ADS)

    Oh, Seungkyung; Kroupa, Pavel

    2016-05-01

    We study the effects that initial conditions of star clusters and their massive star population have on dynamical ejections of massive stars from star clusters up to an age of 3 Myr. We use a large set of direct N-body calculations for moderately massive star clusters (Mecl ≈ 103.5 M⊙). We vary the initial conditions of the calculations, such as the initial half-mass radius of the clusters, initial binary populations for massive stars and initial mass segregation. We find that the initial density is the most influential parameter for the ejection fraction of the massive systems. The clusters with an initial half-mass radius rh(0) of 0.1 (0.3) pc can eject up to 50% (30)% of their O-star systems on average, while initially larger (rh(0) = 0.8 pc) clusters, that is, lower density clusters, eject hardly any OB stars (at most ≈ 4.5%). When the binaries are composed of two stars of similar mass, the ejections are most effective. Most of the models show that the average ejection fraction decreases with decreasing stellar mass. For clusters that are efficient at ejecting O stars, the mass function of the ejected stars is top-heavy compared to the given initial mass function (IMF), while the mass function of stars that remain in the cluster becomes slightly steeper (top-light) than the IMF. The top-light mass functions of stars in 3 Myr old clusters in our N-body models agree well with the mean mass function of young intermediate-mass clusters in M 31, as reported previously. This implies that the IMF of the observed young clusters is the canonical IMF. We show that the multiplicity fraction of the ejected massive stars can be as high as ≈ 60%, that massive high-order multiple systems can be dynamically ejected, and that high-order multiples become common especially in the cluster. We also discuss binary populations of the ejected massive systems. Clusters that are initially not mass-segregated begin ejecting massive stars after a time delay that is caused by mass

  2. How can we best use climate information and hydrologic initial conditions to improve seasonal streamflow forecasts?

    NASA Astrophysics Data System (ADS)

    Mendoza, P. A.; Wood, A. W.; Rothwell, E.; Clark, M. P.; Brekke, L. D.; Arnold, J. R.

    2015-12-01

    Over the last decades, a number of forecasting centers around the world have offered seasonal streamflow predictions, using methodologies that span a wide range of data requirements and complexity. In the western United States, two primary approaches have been adopted for operational purposes: (i) development of regression equations between future streamflow and in situ observations (e.g. rainfall, snow water equivalent), and (ii) ensemble hydrologic model simulations that combine initial watershed moisture states with historically observed weather sequences for the forecast period (e.g., Ensemble Streamflow Prediction, ESP). Nevertheless, none of these methodologies makes use of analyzed or forecast climate information, which might increase the skill of seasonal predictions. Further, there is a need to better understand the marginal benefits of using more complex methods (from statistical to dynamical) and different types of information. In this work, we provide a systematic intercomparison of various seasonal streamflow forecasting techniques, including: (1) a dynamical approach based on conceptual hydrologic modeling and ESP, (2) statistical regression using climate information and/or initial hydrologic conditions, (3) an ESP trace weighting scheme based on analog climatic conditions, and (4) combination of dynamical and statistical forecasts (i.e. hybrid approach). Climate information is taken from the NCEP CFSv2 reanalysis and reforecast datasets. These methods are tested for predicting spring (e.g., May-September) runoff volumes at case study basins located in the US Pacific Northwest, and results obtained for several initialization times are evaluated in terms of accuracy, probabilistic skill and statistical consistency. Preliminary results show that for earlier initialization times (October 1 to December 1), statistical and hybrid techniques that make use of climate information outperform ESP in terms of correlation and probabilistic skill. Although ESP at

  3. Non-Gaussian Initial Conditions in ΛCDM: Newtonian, Relativistic, and Primordial Contributions

    NASA Astrophysics Data System (ADS)

    Bruni, Marco; Hidalgo, Juan Carlos; Meures, Nikolai; Wands, David

    2014-04-01

    The goal of the present paper is to set initial conditions for structure formation at nonlinear order, consistent with general relativity, while also allowing for primordial non-Gaussianity. We use the nonlinear continuity and Raychaudhuri equations, which together with the nonlinear energy constraint, determine the evolution of the matter density fluctuation in general relativity. We solve this equations at first and second order in a perturbative expansion, recovering and extending previous results derived in the matter-dominated limit and in the Newtonian regime. We present a second-order solution for the comoving density contrast in a ΛCDM universe, identifying nonlinear contributions coming from the Newtonian growing mode, primordial non-Gaussianity and intrinsic non-Gaussianity, due to the essential nonlinearity of the relativistic constraint equations. We discuss the application of these results to initial conditions in N-body simulations, showing that relativistic corrections mimic a non-zero nonlinear parameter f NL.

  4. Non-Gaussian initial conditions in ΛCDM: Newtonian, relativistic, and primordial contributions

    SciTech Connect

    Bruni, Marco; Hidalgo, Juan Carlos; Meures, Nikolai; Wands, David

    2014-04-10

    The goal of the present paper is to set initial conditions for structure formation at nonlinear order, consistent with general relativity, while also allowing for primordial non-Gaussianity. We use the nonlinear continuity and Raychaudhuri equations, which together with the nonlinear energy constraint, determine the evolution of the matter density fluctuation in general relativity. We solve this equations at first and second order in a perturbative expansion, recovering and extending previous results derived in the matter-dominated limit and in the Newtonian regime. We present a second-order solution for the comoving density contrast in a ΛCDM universe, identifying nonlinear contributions coming from the Newtonian growing mode, primordial non-Gaussianity and intrinsic non-Gaussianity, due to the essential nonlinearity of the relativistic constraint equations. We discuss the application of these results to initial conditions in N-body simulations, showing that relativistic corrections mimic a non-zero nonlinear parameter f {sub NL}.

  5. Anomalous transport in cellular flows: The role of initial conditions and aging

    NASA Astrophysics Data System (ADS)

    Pöschke, Patrick; Sokolov, Igor M.; Nepomnyashchy, Alexander A.; Zaks, Michael A.

    2016-09-01

    We consider the diffusion-advection problem in two simple cellular flow models (often invoked as examples of subdiffusive tracer motion) and concentrate on the intermediate time range, in which the tracer motion indeed may show subdiffusion. We perform extensive numerical simulations of the systems under different initial conditions and show that the pure intermediate-time subdiffusion regime is only evident when the particles start at the border between different cells, i.e., at the separatrix, and is less pronounced or absent for other initial conditions. The motion moreover shows quite peculiar aging properties, which are also mirrored in the behavior of the time-averaged mean squared displacement for single trajectories. This kind of behavior is due to the complex motion of tracers trapped inside the cell and is absent in classical models based on continuous-time random walks with no dynamics in the trapped state.

  6. Sensitivity to initial conditions in the Bak-Sneppen model of biological evolution

    NASA Astrophysics Data System (ADS)

    Tamarit, F. A.; Cannas, S. A.; Tsallis, C.

    1998-03-01

    We consider biological evolution as described within the Bak and Sneppen 1993 model. We exhibit, at the self-organized critical state, a power-law sensitivity to the initial conditions, calculate the associated exponent, and relate it to the recently introduced nonextensive thermostatistics. The scenario which here emerges without tuning strongly reminds of that of the tuned onset of chaos in say logistic-like one-dimensional maps. We also calculate the dynamical exponent z.

  7. A Comparison of Perturbed Initial Conditions and Multiphysics Ensembles in a Severe Weather Episode in Spain

    NASA Technical Reports Server (NTRS)

    Tapiador, Francisco; Tao, Wei-Kuo; Angelis, Carlos F.; Martinez, Miguel A.; Cecilia Marcos; Antonio Rodriguez; Hou, Arthur; Jong Shi, Jain

    2012-01-01

    Ensembles of numerical model forecasts are of interest to operational early warning forecasters as the spread of the ensemble provides an indication of the uncertainty of the alerts, and the mean value is deemed to outperform the forecasts of the individual models. This paper explores two ensembles on a severe weather episode in Spain, aiming to ascertain the relative usefulness of each one. One ensemble uses sensible choices of physical parameterizations (precipitation microphysics, land surface physics, and cumulus physics) while the other follows a perturbed initial conditions approach. The results show that, depending on the parameterizations, large differences can be expected in terms of storm location, spatial structure of the precipitation field, and rain intensity. It is also found that the spread of the perturbed initial conditions ensemble is smaller than the dispersion due to physical parameterizations. This confirms that in severe weather situations operational forecasts should address moist physics deficiencies to realize the full benefits of the ensemble approach, in addition to optimizing initial conditions. The results also provide insights into differences in simulations arising from ensembles of weather models using several combinations of different physical parameterizations.

  8. The shear-free condition and constant-mean-curvature hyperboloidal initial data

    NASA Astrophysics Data System (ADS)

    Allen, Paul T.; Isenberg, James; Lee, John M.; Stavrov Allen, Iva

    2016-06-01

    We consider the Einstein-Maxwell-fluid constraint equations, and make use of the conformal method to construct and parametrize constant-mean-curvature hyperboloidal initial data sets that satisfy the shear-free condition. This condition is known to be necessary in order that a spacetime development admit a regular conformal boundary at future null infinity; see (Andersson and Chruściel 1994 Commun. Math. Phys. 161 533-68). We work with initial data sets in a variety of regularity classes, primarily considering those data sets whose geometries are weakly asymptotically hyperbolic, as defined in (Allen et al 2015 arXiv:1506.03399). These metrics are C 1,1 conformally compact, but not necessarily C 2 conformally compact. In order to ensure that the data sets we construct are indeed shear-free, we make use of the conformally covariant traceless Hessian introduced in (Allen et al 2015 arXiv:1506.03399). We furthermore construct a class of initial data sets with weakly asymptotically hyerbolic metrics that may be only C 0,1 conformally compact; these data sets are insufficiently regular to make sense of the shear-free condition.

  9. An isotopic-independent highly accurate potential energy surface for CO2 isotopologues and an initial (12)C(16)O2 infrared line list.

    PubMed

    Huang, Xinchuan; Schwenke, David W; Tashkun, Sergey A; Lee, Timothy J

    2012-03-28

    An isotopic-independent, highly accurate potential energy surface (PES) has been determined for CO(2) by refining a purely ab initio PES with selected, purely experimentally determined rovibrational energy levels. The purely ab initio PES is denoted Ames-0, while the refined PES is denoted Ames-1. Detailed tests are performed to demonstrate the spectroscopic accuracy of the Ames-1 PES. It is shown that Ames-1 yields σ(rms) (root-mean-squares error) = 0.0156 cm(-1) for 6873 J = 0-117 (12)C(16)O(2) experimental energy levels, even though less than 500 (12)C(16)O(2) energy levels were included in the refinement procedure. It is also demonstrated that, without any additional refinement, Ames-1 yields very good agreement for isotopologues. Specifically, for the (12)C(16)O(2) and (13)C(16)O(2) isotopologues, spectroscopic constants G(v) computed from Ames-1 are within ±0.01 and 0.02 cm(-1) of reliable experimentally derived values, while for the (16)O(12)C(18)O, (16)O(12)C(17)O, (16)O(13)C(18)O, (16)O(13)C(17)O, (12)C(18)O(2), (17)O(12)C(18)O, (12)C(17)O(2), (13)C(18)O(2), (13)C(17)O(2), (17)O(13)C(18)O, and (14)C(16)O(2) isotopologues, the differences are between ±0.10 and 0.15 cm(-1). To our knowledge, this is the first time a polyatomic PES has been refined using such high J values, and this has led to new challenges in the refinement procedure. An initial high quality, purely ab initio dipole moment surface (DMS) is constructed and used to generate a 296 K line list. For most bands, experimental IR intensities are well reproduced for (12)C(16)O(2) using Ames-1 and the DMS. For more than 80% of the bands, the experimental intensities are reproduced with σ(rms)(ΔI) < 20% or σ(rms)(ΔI∕δ(obs)) < 5. A few exceptions are analyzed and discussed. Directions for future improvements are discussed, though it is concluded that the current Ames-1 and the DMS should be useful in analyzing and assigning high-resolution laboratory or astronomical spectra. PMID:22462861

  10. Parametrisation of initial conditions for seasonal stream flow forecasting in the Swiss Rhine basin

    NASA Astrophysics Data System (ADS)

    Schick, Simon; Rössler, Ole; Weingartner, Rolf

    2016-04-01

    Current climate forecast models show - to the best of our knowledge - low skill in forecasting climate variability in Central Europe at seasonal lead times. When it comes to seasonal stream flow forecasting, initial conditions thus play an important role. Here, initial conditions refer to the catchments moisture at the date of forecast, i.e. snow depth, stream flow and lake level, soil moisture content, and groundwater level. The parametrisation of these initial conditions can take place at various spatial and temporal scales. Examples are the grid size of a distributed model or the time aggregation of predictors in statistical models. Therefore, the present study aims to investigate the extent to which the parametrisation of initial conditions at different spatial scales leads to differences in forecast errors. To do so, we conduct a forecast experiment for the Swiss Rhine at Basel, which covers parts of Germany, Austria, and Switzerland and is southerly bounded by the Alps. Seasonal mean stream flow is defined for the time aggregation of 30, 60, and 90 days and forecasted at 24 dates within the calendar year, i.e. at the 1st and 16th day of each month. A regression model is employed due to the various anthropogenic effects on the basins hydrology, which often are not quantifiable but might be grasped by a simple black box model. Furthermore, the pool of candidate predictors consists of antecedent temperature, precipitation, and stream flow only. This pragmatic approach follows the fact that observations of variables relevant for hydrological storages are either scarce in space or time (soil moisture, groundwater level), restricted to certain seasons (snow depth), or regions (lake levels, snow depth). For a systematic evaluation, we therefore focus on the comprehensive archives of meteorological observations and reanalyses to estimate the initial conditions via climate variability prior to the date of forecast. The experiment itself is based on four different

  11. Terrestrial-type planet formation. Comparing different types of initial conditions

    NASA Astrophysics Data System (ADS)

    Ronco, M. P.; de Elía, G. C.; Guilera, O. M.

    2015-12-01

    Context. The initial distributions of planetary embryos and planetesimals used in N-body simulations play an important role for studies of the terrestrial-type planet formation during the post oligarchic growth. In general, most of these studies typically use ad hoc initial distributions based primarily on theoretical and numerical studies. Aims: We analyze the formation of planetary systems without gas giants around solar-type stars by focusing on the sensitivity of the results to the particular initial distributions used for planetesimals and planetary embryos at the end of the gas phase of the protoplanetary disk. The formation process of terrestrial planets in the habitable zone (HZ) and their final water contents are also topics of special interest in this work. Methods: We developed two different sets of N-body simulations starting with the same protoplanetary disk. The first set assumes typical ad hoc initial distributions for embryos and planetesimals, and the second set obtains these initial distributions from the results of a semi-analytical model that simulates the evolution of the protoplanetary disk during the gaseous phase. Results: The two sets of simulations form planets within the HZ. Using ad hoc initial conditions, the masses of the planets that remain in the HZ range from 0.66 M⊕ to 2.27 M⊕. Using more realistic initial conditions obtained from a semi-analytical model, we found that the masses of the planets range from 1.18 M⊕ to 2.21 M⊕. Both sets of simulations form planets in the HZ with water contents ranging between 4.5% and 39.48% by mass. The planets that have the highest water contents with respect to those with the lowest water contents present differences regarding the sources of water supply. Conclusions: From comparing the two sets of simulations, we suggest that the number of planets that remain in the HZ is not sensitive to the particular initial distribution of embryos and planetesimals, and therefore the results are

  12. Constraining the initial conditions of globular clusters using their radius distribution

    NASA Astrophysics Data System (ADS)

    Alexander, Poul E. R.; Gieles, Mark

    2013-05-01

    Studies of extragalactic globular clusters (GCs) have shown that the peak size of the GC radius distribution (RD) depends only weakly on galactic environment. We model RDs of GC populations using a simple prescription for a Hubble time of relaxation-driven evolution of cluster mass and radius. We consider a power-law cluster initial mass function (CIMF) with and without an exponential truncation, and focus in particular on a flat and a steep CIMF (power-law indices of 0 and -2, respectively). For the initial half-mass radii at birth, we adopt either Roche volume (RV) filling conditions (`filling', meaning that the ratio of half-mass to Jacobi radius is approximately rh/rJ ≃ 0.15) or strongly RV under-filling conditions (`under-filling', implying that initially rh/rJ ≪ 0.15). Assuming a constant orbital velocity about the galaxy centre, we find for a steep CIMF that the typical half-light radius scales with the galactocentric radius RG as R{^{1/3}_G}. This weak scaling is consistent with observations, but this scenario has the (well-known) problem that too many low-mass clusters survive. A flat CIMF with `filling' initial conditions results in the correct MF at old ages, but with too many large (massive) clusters at large RG. An `under-filling' GC population with a flat CIMF also results in the correct MF, and can also successfully reproduce the shape of the RD, with a peak size that is (almost) independent of RG. In this case, the peak size depends (almost) only on the peak mass of the GC MF. The (near) universality of the GC RD is therefore because of the (near) universality of the CIMF. There are some extended GCs in the outer halo of the Milky Way that cannot be explained by this model.

  13. Can AERONET data be used to accurately model the monochromatic beam and circumsolar irradiances under cloud-free conditions in desert environment?

    NASA Astrophysics Data System (ADS)

    Eissa, Y.; Blanc, P.; Wald, L.; Ghedira, H.

    2015-07-01

    Routine measurements of the beam irradiance at normal incidence (DNI) include the irradiance originating from within the extent of the solar disc only (DNIS) whose angular extent is 0.266° ± 1.7 %, and that from a larger circumsolar region, called the circumsolar normal irradiance (CSNI). This study investigates if the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic DNIS and CSNI under cloud-free conditions in a desert environment. The data from an AERONET station in Abu Dhabi, United Arab Emirates, and a collocated Sun and Aureole Measurement (SAM) instrument which offers reference measurements of the monochromatic profile of solar radiance, were exploited. Using the AERONET data both the radiative transfer models libRadtran and SMARTS offer an accurate estimate of the monochromatic DNIS, with a relative root mean square error (RMSE) of 5 %, a relative bias of +1 % and acoefficient of determination greater than 0.97. After testing two configurations in SMARTS and three in libRadtran for modelling the monochromatic CSNI, libRadtran exhibits the most accurate results when the AERONET aerosol phase function is presented as a Two Term Henyey-Greenstein phase function. In this case libRadtran exhibited a relative RMSE and a bias of respectively 22 and -19 % and a coefficient of determination of 0.89. The results are promising and pave the way towards reporting the contribution of the broadband circumsolar irradiance to standard DNI measurements.

  14. Evaluation of the effects of initial conditions on transients in PUMA

    SciTech Connect

    Parlatan, Y.; Jo, J.; Rohatgi, U.S.

    1996-06-01

    A Simplified Boiling Water Reactor (SBWR) is the latest Boiling Water Reactor (BWR) designed by the General Electric (GE). Major differences between the SBWR and the currently operating BWRs include the use of passive gravity-driven systems in the SBWR for emergency cooling of the vessel and containment. In order to investigate the phenomena expected during a Loss of Coolant Accident (LOCA), Nuclear Regulatory Commission (NRC) has sponsored an integral scaled-test facility, called Purdue University Multidimensional Integral Test Assembly (PUMA). The facility models all the major safety-related components of SBWR. Two PUMA initialization calculations were performed to assist the Purdue University in establishing test initialization procedures. Both calculations were based on the initial conditions obtained from SBWR LOCA simulation. In the base case, a complete separation between vapor and liquid was assumed, with all the water in the lower part of the Reactor Pressure Vessel (RPV) and all the vapor above it. In the sensitivity case, the water inventory was distributed in the vessel in the same way as in the SBWR at 1.034 MPa, which is the initial pressure for PUMA facility. Purdue University plans to initialize the PUMA tests as in the base case. The sensitivity calculation is performed to provide assurance that this mode of initialization is adequate. It also provides information on possible differences in the progress of transients. The paper will discuss the differences in the early part of the transient. The conclusion from this study will also apply to many integral facilities which simulate the reactor transients form the middle of the transient.

  15. Sensitivities of AGCM-Simulated Tropical Cyclones to Varying Initial Conditions

    NASA Astrophysics Data System (ADS)

    He, F.; Posselt, D. J.; Narisetty, N.; Zarzycki, C.; Nair, V.

    2013-12-01

    General Circulation Models (GCMs) have been increasingly used to simulate Tropical Cyclones (TCs) and predict their changes due to the effects of climate warming. As such, the motivation is to examine how the development of Tropical Cyclones (TCs) is represented in Atmospheric General circulation Models (AGCMs) and assesses the impact of changes in initial conditions, which include Radius of Maximum wind speed (RMW), Maximum wind speed (MWS), Sea surface temperature (SST), Environmental lapse rate (Gamma) and mid-level relative humidity (500-hPa RH), on modeled TCs. The National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM) has been used to simulate the development of idealized TCs over 10 days. A Latin Hypercube Sampling (LHS) method is used to generate two 300-member space-filling ensembles of simulations with grid resolution of 1×1 and 0.5 ×0.5 degree respectively. Composite analysis is first used to analyze the ensemble results, then, the Expanded Multivariate Adaptive Regression Splines (EMARS) method is implemented to characterize various TC response functions. Both 0.5 and 1.0 degree simulations produce a wide range of TC intensities ranging from tropical depression to category 4 or 5 on the Saffir-Simpson scale. On average, storms in the higher resolution simulations are stronger than those produced by the coarser-resolution model. Specifically, it is found that (1) the intensity, track, cloud, precipitation and radiative fields of simulated TCs are highly sensitive to changes in the initial vortex characteristics and surrounding environment; (2) nonlinear interaction between the initial conditions is crucial to the distribution of clouds, precipitation, and radiation of simulated TCs; (3) favorable initial conditions are able to produce intense and destructive TCs even in1 ×1 degree resolution global climate models; (4) inter-relationships exist among the cloud radiative forcing, cloud water content, precipitation and intensity

  16. Impact of soil moisture initial conditions on multi model summer predictions over mid-latitudes

    NASA Astrophysics Data System (ADS)

    Ardilouze, Constantin; Prodhomme, Chloé; Batté, Lauriane; Déqué, Michel

    2016-04-01

    Land surface initial conditions have been recognized as a potential source of predictability at seasonal time scales. As an example, results from GLACE-2 (phase 2 of the Global Land-Atmosphere Coupling Experiment) highlighted the impact of spring soil moisture in summer near-surface air temperature prediction over Europe and Northern America with global long-range forecast systems (Koster et al., 2011, van den Hurk et al.,2012). Yet, few studies have explored such an influence over a sufficient hindcast period to produce a robust quantitative assessment. In the framework of the FP7-SPECS project, dedicated experiments have been carried out with June-August hindcasts from 5 distinct Atmosphere Ocean Global Climate Models initialized either by realistic or climatological soil moisture conditions on May 1st. Realistic initialization leads to an improved 2-meter temperature prediction skill over parts of Europe in the multi model, particularly the Balkans peninsula which had been identified as a hot spot of soil moisture-atmosphere coupling (Seneviratne et al. 2006) However no improvement was found over North-American Great Plains in spite of the high potential of this region. Further analyses suggest that this lack of skill stems from a common shortcoming of the models. All of them tend to overestimate the positive feedback between soil moisture, temperature and precipitation with respect to the observations. Hence, tackling model systematic biases over the US Southern Great Plains appears as a necessary prerequisite for summer predictability enhancement.

  17. The problem of the initial conditions in flavoured leptogenesis and the tauon N-dominated scenario

    NASA Astrophysics Data System (ADS)

    Bertuzzo, Enrico; Di Bari, Pasquale; Marzola, Luca

    2011-08-01

    We discuss the conditions to realise a scenario of 'strong thermal leptogenesis,' where the final asymmetry is fully independent of the initial conditions, taking into account both heavy and light neutrino flavour effects. In particular, the contribution to the final asymmetry from an initial pre-existing asymmetry has to be negligible. We show that in the case of a hierarchical right-handed (RH) neutrino mass spectrum, the only possible way is an N-dominated leptogenesis scenario with a lightest RH neutrino mass M≪10 GeV and with a next-to-lightest RH neutrino mass 10 GeV≫M≫10 GeV. This scenario necessarily requires the presence of a heaviest third RH neutrino specie. Moreover, we show that the final asymmetry has to be dominantly produced in the tauon flavour while the electron and the muon asymmetries have to be efficiently washed-out by the lightest RH neutrino inverse processes. Intriguingly, such seemingly special conditions for successful strong thermal leptogenesis are naturally fulfilled within SO(10)-inspired models. Besides the tauon N-dominated scenario, successful strong thermal leptogenesis is also achieved in scenarios with quasi-degenerate RH neutrino masses. We also comment on the supersymmetric case. We also derive an expression for the final asymmetry produced from leptogenesis taking fully into account heavy neutrino flavour effects in the specific case M≫10 GeV (heavy flavoured scenario), a result that can be extended to any other mass pattern.

  18. Reduction of damage initiation density in fused silica optics via UV laser conditioning

    DOEpatents

    Peterson, John E.; Maricle, Stephen M.; Brusasco, Raymond M.; Penetrante, Bernardino M.

    2004-03-16

    The present invention provides a method for reducing the density of sites on the surface of fused silica optics that are prone to the initiation of laser-induced damage, resulting in optics which have far fewer catastrophic defects and are better capable of resisting optical deterioration upon exposure for a long period of time to a high-power laser beam having a wavelength of about 360 nm or less. The initiation of laser-induced damage is reduced by conditioning the optic at low fluences below levels that normally lead to catastrophic growth of damage. When the optic is then irradiated at its high fluence design limit, the concentration of catastrophic damage sites that form on the surface of the optic is greatly reduced.

  19. Heavy ion initial conditions and correlations between higher moments in the spatial anisotropy

    SciTech Connect

    Nagle, J. L.; McCumber, M. P.

    2011-04-15

    Fluctuations in the initial conditions for relativistic heavy ion collisions are proving to be crucial to understanding final state flow and jet quenching observables. The initial geometry has been parametrized in terms of moments in the spatial anisotropy (i.e., {epsilon}{sub 2},{epsilon}{sub 3},{epsilon}{sub 4},{epsilon}{sub 5},...), and it has been stated in multiple published articles that the vector directions of odd moments are uncorrelated with the even moments and the reaction place angle. In this article, we demonstrate that this is incorrect and that a substantial nonzero correlation exists between the even and odd moments in peripheral Au+Au collisions. These correlations persist for all centralities, though at a very small level for the 0-55% most central collisions.

  20. Origins of the rings of Uranus and Neptune. II - Initial conditions and ring moon populations

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.; Esposito, L. W.

    1993-04-01

    Catastrophic fragmentation of the ring moons of Uranus and Neptune occurs in approximately 10 exp 8 years. The fate of the debris following a fragmenting impact is central to understanding the evolution of these satellites and the hypothesized origin of rings from their debris. In this paper the possible effects of the velocity distribution of fragments following a catastrophic fragmentation on satellite diminution via a collisional cascade is examined. Fragment velocities are critical in the evolution of the collisional cascade because of the possibility of reaccretion following disruption. The fragment velocity distribution is used to calculate the initial phase space distribution of the new ring particles. This provides a physically realistic initial condition for simulations of the collisional evolution of planetary rings.

  1. Origins of the rings of Uranus and Neptune. II - Initial conditions and ring moon populations

    NASA Technical Reports Server (NTRS)

    Colwell, Joshua E.; Esposito, Larry W.

    1993-01-01

    Catastrophic fragmentation of the ring moons of Uranus and Neptune occurs in approximately 10 exp 8 years. The fate of the debris following a fragmenting impact is central to understanding the evolution of these satellites and the hypothesized origin of rings from their debris. In this paper the possible effects of the velocity distribution of fragments following a catastrophic fragmentation on satellite diminution via a collisional cascade is examined. Fragment velocities are critical in the evolution of the collisional cascade because of the possibility of reaccretion following disruption. The fragment velocity distribution is used to calculate the initial phase space distribution of the new ring particles. This provides a physically realistic initial condition for simulations of the collisional evolution of planetary rings.

  2. Plans for Conditioning Plasma-Facing Components at Initiation of NSTX-U Operations

    NASA Astrophysics Data System (ADS)

    Kaita, R.; Blanchard, W.; Cai, D.; Gerhardt, S.; Jaworski, M. A.; Lucia, M.; Rossi, S.; Skinner, C. H.; Allain, J.-P.; Bedoya, F.

    2014-10-01

    The conditioning of plasma-facing components (PFCs) has been critical to the achievement of high performance plasmas in fusion devices. The NSTX-U PFCs will initially consist of graphite. Well-established PFC conditioning will be applied, including high temperature bakeout and glow discharge cleaning (GDC). As in NSTX, the center stack (CS) will be electrically-isolated from the outer vacuum vessel in NSTX-U for coaxial helicity injection (CHI), and this also permits high currents to pass through the CS for baking. Other conditioning techniques are required to further reduce the dominant impurities, which are expected to be carbon and oxygen. Boronization will first be performed, where helium glow discharge cleaning (GDC) is followed by GDC with a mixture of 95% helium and 5% deuterated trimethyl boron (TMB), and another period of helium GDC. This is to be compared with lithiumization, where lithium vapor is evaporated directly on PFC surfaces. The effectiveness of both conditioning techniques has been inferred from plasma measurements subsequent to their application, but the link between them and actual PFC conditions has not been made. The new Materials Analysis and Particle Probe (MAPP) is intended to do this with in situ analysis of PFC samples exposed to NSTX-U plasmas. Work supported by DOE Contract No. DE-AC02-09CH11466 and DE-SC0010717.

  3. Rapid Optimal SPH Particle Distributions in Spherical Geometries for Creating Astrophysical Initial Conditions

    NASA Astrophysics Data System (ADS)

    Raskin, Cody; Owen, J. Michael

    2016-04-01

    Creating spherical initial conditions in smoothed particle hydrodynamics simulations that are spherically conformal is a difficult task. Here, we describe two algorithmic methods for evenly distributing points on surfaces that when paired can be used to build three-dimensional spherical objects with optimal equipartition of volume between particles, commensurate with an arbitrary radial density function. We demonstrate the efficacy of our method against stretched lattice arrangements on the metrics of hydrodynamic stability, spherical conformity, and the harmonic power distribution of gravitational settling oscillations. We further demonstrate how our method is highly optimized for simulating multi-material spheres, such as planets with core-mantle boundaries.

  4. Importance of Granular Structure in the Initial Conditions for the Elliptic Flow

    SciTech Connect

    Andrade, R. P. G.; Grassi, F.; Hama, Y.; Qian, W. L.; Kodama, T.

    2008-09-12

    We show the effects of the granular structure of the initial conditions of a hydrodynamic description of high-energy nucleus-nucleus collisions on some observables, especially on the elliptic-flow parameter v{sub 2}. Such a structure enhances production of isotropically distributed high-p{sub T} particles, making v{sub 2} smaller there. Also, it reduces v{sub 2} in the forward and backward regions where the global matter density is smaller and, therefore, where such effects become more efficacious.

  5. The Relative Roles of Lateral Boundaries, Initial Conditions, and Topography in Mesoscale Simulations of Lee Cyclogenesis.

    NASA Astrophysics Data System (ADS)

    Alpert, P.; Krichak, S. O.; Krishnamurti, T. N.; Stein, U.; Tsidulko, M.

    1996-07-01

    The contributions of boundary factors, which may be considered to be independent of the physics or the dynamics of the mesoscale model, are explored in a consistent approach for a widely investigated Alpine Experiment (AL-PEX) lee cyclogenesis case. The roles of the lateral boundaries and the initial fields in conjunction with that of the topography, as well as their possible nonlinear interactions in various model settings, are calculated with the aid of the recently developed factor separation method. Focus is given to the influences of the extent of the model domain and of the running period prior to the climax of the lee cyclone development during 3 6 March 1982. It is shown that the initial conditions are dominant in the first 9 15 h, during which time the topography and lateral boundaries play negative roles because of the adjusting processes. The nonlinear interaction BI between lateral boundaries (B) and the initial conditions (I) was found to be the major contributor to the cyclone deepening during the adjustment period. For longer running periods, some equilibrium is reached in which both the BI interaction and the lateral boundary dominate. The topographic contribution to the lee cyclone deepening in this ALPEX case was indeed limited to about 20% only, as already indicated by earlier studies. Testing several distances of the western lateral boundary suggests the existence of an optimal distance for good results. Both too distant and too close lateral boundaries yield worse results. Testing with frozen boundary conditions shows that the update of the lateral boundaries at a specific time of +36 h was crucial to the development. The results are clearly dependent to some extent on the model type and the particular case under investigation, as well as on the boundary conditions, the initialization procedures, and other model characteristics. The current experiments, however, provide a quantitative approach for estimating the relative roles of the

  6. INITIAL TEST WELL CONDITIONING AT NOPAL I URANIUM DEPOSIT, SIERRA PENA BLANCA, CHIHUAHUA, MEXICO

    SciTech Connect

    R.D. Oliver; J.C. Dinsmoor; S.J. Goldstein; I. Reyes; R. De La Garza

    2005-07-11

    Three test wells, PB-1, PB-2, and PB-3, were drilled at the Nopal I uranium deposit as part of a natural analogue study to evaluate radionuclide transport processes during March-April 2003. The initial pumping to condition the wells was completed during December 2003. The PB-1 well, drilled immediately adjacent to the Nopal I ore body, was continuously cored to a depth of 250 m, terminating 20 m below the top of the measured water level. The PB-2 and PB-3 wells, which were drilled on opposite sides of PB-1 at a radial distance of approximately 40 to 50 m outside of the remaining projected ore body, were also drilled to about 20 m below the top of the measured water level. Each test well was completed with 4-inch (10.2-cm) diameter PVC casing with a slotted liner below the water table. Initial conditioning of all three wells using a submersible pump at low pump rates [less than 1 gallon (3.8 1) per minute] resulted in measurable draw down and recoveries. The greatest drawdown ({approx}15 m) was observed in PB-2, whereas only minor (<1 m) drawdown occurred in PB-3. For PB-1 and PB-2, the water turbidity decreased as the wells were pumped and the pH values decreased, indicating that the contamination from the drilling fluid was reduced as the wells were conditioned. Test wells PB-1 and PB-2 showed increased inflow after several borehole volumes of fluid were removed, but their inflow rates remained less that the pumping rate. Test well PB-3 showed the smallest drawdown and least change in pH and conductivity during initial pumping and quickest recovery with a rise in measured water level after conditioning. The 195 gallons (750 l) of water pumped from PB-3 during conditioning was discharged through a household sponge. That sponge showed measurable gamma radiation, which decayed to background values in less than 12 hours. Preliminary interpretations include filtration of a radioisotope source with a short half-life or of a radioisotope that volatized as the sponge

  7. Assessment of land use impact on hydraulic threshold conditions for gully head cut initiation

    NASA Astrophysics Data System (ADS)

    Nazari Samani, Aliakbar; Chen, Qiuwen; Khalighi, Shahram; Wasson, Robert James; Rahdari, Mohammad Reza

    2016-07-01

    A gully as an accelerated erosion process is responsible for land degradation under various environmental conditions and has been known as a threshold phenomenon. Although the effects of gullying processes have been well documented, few soil erosion models have taken into account the threshold condition necessary for gully development. This research was devoted to determining the effects of land use change on hydraulic threshold condition and stream power of water flow through an in situ experimental flume (15 m × 0.4 m). Results indicated that head cut initiation and detachment rates showed a better correlation to stream power indices than shear stress (τcr). The threshold unit stream power value (ωu) for head cut initiation in rangeland, abandoned land, and dry farming land was 0.0276, 0.0149, and 4.5 × 10-5 m s-1, respectively. Moreover, the micro-relief condition of soil surface and surface vegetation affected the flow regime of discharge and velocity. It is seen that the composite hydraulic criteria of Froude number (Fr) and discharge (Q) can clearly discriminate the land uses' threshold. In fact, the remarkable decrease of τcr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that using the unit steam power index instead of critical shear stress could increase the models' precision for prediction of head cut development. Compared to the Ephemeral Gully Erosion Model (EGEM) equation for critical shear stress, it is important to point out that for modelling of gully erosion, using single soil attributes can lead to an inaccurate estimation for τcr. In addition, based on the findings of this research, the use of threshold values of τcr = 35 dyne cm-2 and ωu = 0.4 cm s-1 in physically based soil erosion models is susceptible to high uncertainty when assessing gully erosion.

  8. Variation in initiation condition of debris flows in the mountain regions surrounding Beijing

    NASA Astrophysics Data System (ADS)

    Ma, Chao; Wang, Yu-jie; Du, Cui; Wang, Yun-qi; Li, Yun-peng

    2016-11-01

    Debris flows in the mountain regions surrounding Beijing have been occurring for a long time and have resulted in great economic losses. In this study, 23 rainstorm events, surficial sediments, and debris flow deposits were analyzed to quantify the area's rainfall threshold and to investigate how such conditions may be used to predict debris flow in this region. Rainfall threshold of intensity-duration (I-D) functions after vegetation recovery was higher than before recovery and also higher than I-D levels in other regions where debris flows are closely associated with runoff. Field investigations revealed that surficial sediments were characterized by coarse-grained sediments and that debris flow deposits lacked fine particles. Local debris flows can be triggered by runoff; however, no single standard equation is used to predict the conditions that lead to runoff-triggered debris flow; and commonly used equations give different values. Here, we propose an empirical function that takes into account peak discharge per width and particle diameter. This model should be verified with further investigations so that it can be used as a reference to analyze the conditions that lead to debris flow in the study area. Finally, debris flows may have been related to occasional storms in the study area, which has been experiencing substantially increased temperatures and decreased annual precipitation. This work provides important information about the conditions that initiated debris flow in the Beijing mountain regions in the last few decades.

  9. Initial conditions for radiation analysis: models of galactic cosmic rays and solar particle events

    NASA Astrophysics Data System (ADS)

    Nymmik, R. A.

    During interplanetary missions the radiation conditions are determined by fluxes of Galactic Cosmic Ray (GCR) particles and Solar Energetic Particles (SEP). The particle fluxes of these two high-energy radiation components differ fundamentally in energy spectra and have the opposite dependence on solar activity level. One of the key issues, associated with estimating flight conditions for missions to the Moon, various asteroids and Mars, is the relative balance between GCR and SCR, depending on the level of solar activity and the distance to the Sun for both open space conditions and conditions inside the spacecraft. This task can be solved with sufficient accuracy only when using such particle flux models (of the above mentioned radiation sources), which are based on unified parameters, describing the current solar activity level. Such models, employing smoothed Wolf numbers as the initial parameter, were developed at SINP MSU. These models are - the semi-empirical model of GCR fluxes, which has currently been approved as an international standard (ISO 15390), and the probabilistic model of SEP particle fluxes, which is currently under discussion as a draft international standard (ISO DRAFT 15391). The report presents a survey of experimental data on GCR and SEP fluxes in interplanetary space at various solar activity levels, and an analysis of the reliability and completeness of data on these fluxes, provided by various calculation models.

  10. Importance of initial conditions in seasonal predictions of Arctic sea ice extent

    NASA Astrophysics Data System (ADS)

    Msadek, R.; Vecchi, G. A.; Winton, M.; Gudgel, R. G.

    2014-07-01

    We present seasonal predictions of Arctic sea ice extent (SIE) over the 1982-2013 period using two suites of retrospective forecasts initialized from a fully coupled ocean-atmosphere-sea ice assimilation system. High skill scores are found in predicting year-to-year fluctuations of Arctic SIE, with significant correlations up to 7 month ahead for September detrended anomalies. Predictions over the recent era, which coincides with an improved observational coverage, outperform the earlier period for most target months. We find, however, a degradation of skill in September during the last decade, a period of sea ice thinning in observations. The two prediction models, Climate Model version 2.1 (CM2.1) and Forecast-oriented Low Ocean Resolution (FLOR), share very similar ocean and ice component and initialization but differ by their atmospheric component. FLOR has improved climatological atmospheric circulation and sea ice mean state, but its skill is overall similar to CM2.1 for most seasons, which suggests a key role for initial conditions in predicting seasonal SIE fluctuations.

  11. Initial subjective reward: single-exposure conditioned place preference to alcohol in mice.

    PubMed

    Grisel, Judith E; Beasley, John B; Bertram, Emma C; Decker, Brooke E; Duan, Chunyu A; Etuma, Mahder; Hand, Annie; Locklear, Mallory N; Whitmire, Matthew P

    2014-01-01

    Most adults consume alcohol with relative impunity, but about 10-20% of users persist (or progress) in their consumption, despite mounting and serious repercussions. Identifying at-risk individuals before neuroadaptative changes associated with chronic use become well ingrained is thus a key step in mitigating and preventing the end stage disease and its devastating impacts. Explaining liability has been impeded, in part, by the absence of animal models for assessing initial sensitivity to the drug's reinforcing properties, an important endophenotype in the trajectory toward excessive drinking. Here we assess the initial rewarding effects of the drug in a novel application of the conditioned place preference paradigm. In contrast to previous studies that have all employed repeated drug administration, we demonstrated a robust preference for a context paired with a single exposure to 1.5 g/kg EtOH in male and female subjects of three strains. This model validates an assay of initial sensitivity to the subjective rewarding effects of alcohol, a widely used drug with multifarious impacts on both brain and society, and provides a new tool for theory-driven endophenotypic pharmacogenetic approaches to understanding and treating addiction. PMID:25408633

  12. What initial condition of inflation would suppress the large-scale CMB spectrum?

    DOE PAGES

    Chen, Pisin; Lin, Yu -Hsiang

    2016-01-08

    There is an apparent power deficit relative to the Λ CDM prediction of the cosmic microwave background spectrum at large scales, which, though not yet statistically significant, persists from WMAP to Planck data. Proposals that invoke some form of initial condition for the inflation have been made to address this apparent power suppression, albeit with conflicting conclusions. By studying the curvature perturbations of a scalar field in the Friedmann-Lemaître-Robertson-Walker universe parameterized by the equation of state parameter w, we find that the large-scale spectrum at the end of inflation reflects the superhorizon spectrum of the initial state. The large-scale spectrummore » is suppressed if the universe begins with the adiabatic vacuum in a superinflation (w < –1) or positive-pressure (w > 0) era. In the latter case, there is however no causal mechanism to establish the initial adiabatic vacuum. On the other hand, as long as the universe begins with the adiabatic vacuum in an era with –1 < w < 0, even if there exists an intermediate positive-pressure era, the large-scale spectrum would be enhanced rather than suppressed. In conclusion, we further calculate the spectrum of a two-stage inflation model with a two-field potential and show that the result agrees with that obtained from the ad hoc single-field analysis.« less

  13. Experiments on Effects of Initial Conditions and Material Strength on Rayleigh-Taylor Instability

    NASA Astrophysics Data System (ADS)

    Roach, Pamela; Banerjee, Arindam

    2013-11-01

    The effects of initial conditions on Rayleigh-Taylor (RT) instability in an accelerated elastic-plastic solid were studied. A novel rotating wheel RT experiment that uses centrifugal forces to accelerate a two-material interface was utilized to study the effect of amplitude and wavelength on RT instability with an elastic-plastic solid. The experiment consists of a container filled with air and mayonnaise, a non-Newtonian emulsion, with an initial perturbation between the two materials. Single mode perturbations of various amplitudes and wavelengths were analyzed and results indicated the acceleration required for instability increased for both decreasing initial amplitude and wavelength. Three-dimensional interfaces were found to be more stable than two-dimensional interfaces. Critical amplitude and growth rates were compared with prior experimental results and analytical growth models. Elastic and plastic peak amplitude responses were observed for stable interfaces using a variable acceleration profile where the test section was first accelerated to slightly below the critical acceleration and then decelerated at the same rate. This exercise allowed for verification of the elastic-plastic (EP) transition process before instability was reached. Authors acknowledge financial support from DOE-LANL subcontract # 173667-1 to Lehigh University and a NSF-Graduate Research Fellowship to Pamela Roach.

  14. Plate tectonics on large exoplanets and the importance of the initial conditions

    NASA Astrophysics Data System (ADS)

    Noack, Lena; Breuer, Doris

    2013-04-01

    Several numerical studies have been published in the past years speculating about the existence of plate tectonics on large exoplanets. These studies focus on various aspects like the mass of a planet [1,2,3,5], the interior heating rate and mantle temperatures [4,5] and the occurrence of water in the upper mantle [6]. Different trends in the propensity for plate tectonics have been observed in particular when varying the planetary mass: with increasing mass the surface mobilization is found to be either more [2,3,5], equally [3,6] or less [1,4] likely than on Earth. These studies and their implications are, however, difficult to compare as they assume different initial conditions and parameter sets, and either neglect the pressure effect on the viscosity or assume a rather small influence of the pressure on the rheology. Furthermore, the thermal evolution of the planets (i.e. cooling of core and decrease in radioactive heat sources with time) is typically neglected. In our study, we us the finite volume code GAIA [7] and apply a pseudo-plastic rheology. We investigate how a strong pressure-dependence of the viscosity [8] influences not only the convective regime in the lower mantle, but also the upper mantle and hence the likelihood to obtain plate tectonics. We investigate how our results change when assuming different initial conditions, focussing on the initial temperature in the lower mantle and at the core-mantle boundary. We find that the initial temperature conditions have a first-order influence on the likelihood of plate tectonics on large exoplanets and (as observed in earlier studies) surface mobilization may either be more, equally or less likely than on Earth. References [1] O'Neill, C. and A. Lenardic (2007), GRL 34, 1-4. [2] Valencia, D., O'Connell, R.J. and Sasselov, D.D. (2007), Astrophys. J. Let., 670(1):45-48. [3] van Heck, H.J. and Tackley, P.J. (2011), EPSL, 310:252-261. [4] Stein, C.; A. Finnenkötter, J. P. Lowman and U. Hansen (2011), GRL

  15. Impact of precipitation forecast uncertainties and initial soil moisture conditions on a probabilistic flood forecasting chain

    NASA Astrophysics Data System (ADS)

    Silvestro, Francesco; Rebora, Nicola

    2014-11-01

    One of the main difficulties that flood forecasters are faced with is evaluating how errors and uncertainties in forecasted precipitation propagate into streamflow forecast. These errors, must be combined with the effects of different initial soil moisture conditions that generally have a significant impact on the final results of a flood forecast. This is further complicated by the fact that a probabilistic approach is needed, especially when small and medium size basins are considered (the variability of the streamflow scenarios is in fact strongly influenced by the aforementioned factors). Moreover, the ensemble size is a degree of freedom when a precipitation downscaling algorithm is part of the forecast chain. In fact, a change of ensemble size could lead to different final results once the other inputs and parameters are fixed. In this work, a series of synthetic experiments have been designed and implemented to test an operational probabilistic flood forecast system in order to augment the knowledge of how streamflow forecasts can be affected by errors and uncertainties associated with the three aforementioned elements: forecasted rainfall, soil moisture initial conditions, and ensemble size.

  16. Large-scale bias and efficient generation of initial conditions for nonlocal primordial non-Gaussianity

    NASA Astrophysics Data System (ADS)

    Scoccimarro, Román; Hui, Lam; Manera, Marc; Chan, Kwan Chuen

    2012-04-01

    We study the scale dependence of halo bias in generic (nonlocal) primordial non-Gaussian (PNG) initial conditions of the type motivated by inflation, parametrized by an arbitrary quadratic kernel. We first show how to generate nonlocal PNG initial conditions with minimal overhead compared to local PNG models for a general class of primordial bispectra that can be written as linear combinations of separable templates. We run cosmological simulations for the local, and nonlocal equilateral and orthogonal models and present results on the scale dependence of halo bias. We also derive a general formula for the Fourier-space bias using the peak-background split in the context of the excursion-set approach to halos and discuss the difference and similarities with the known corresponding result from local bias models. Our peak-background split bias formula generalizes previous results in the literature to include non-Markovian effects and nonuniversality of the mass function and are in better agreement with measurements in numerical simulations than previous results for a variety of halo masses, redshifts and halo definitions. We also derive for the first time quadratic bias results for arbitrary nonlocal PNG, and show that nonlinear bias loops give small corrections at large scales. The resulting well-behaved perturbation theory paves the way to constrain nonlocal PNG from measurements of the power spectrum and bispectrum in galaxy redshift surveys.

  17. N-body simulations with generic non-Gaussian initial conditions II: halo bias

    NASA Astrophysics Data System (ADS)

    Wagner, Christian; Verde, Licia

    2012-03-01

    We present N-body simulations for generic non-Gaussian initial conditions with the aim of exploring and modelling the scale-dependent halo bias. This effect is evident on very large scales requiring large simulation boxes. In addition, the previously available prescription to implement generic non-Gaussian initial conditions has been improved to keep under control higher-order terms which were spoiling the power spectrum on large scales. We pay particular attention to the differences between physical, inflation-motivated primordial bispectra and their factorizable templates, and to the operational definition of the non-Gaussian halo bias (which has both a scale-dependent and an approximately scale-independent contributions). We find that analytic predictions for both the non-Gaussian halo mass function and halo bias work well once a fudge factor (which was introduced before but still lacks convincing physical explanation) is calibrated on simulations. The halo bias remains therefore an extremely promising tool to probe primordial non-Gaussianity and thus to give insights into the physical mechanism that generated the primordial perturbations. The simulation outputs and tables of the analytic predictions will be made publicly available via the non-Gaussian comparison project web site http://icc.ub.edu/~liciaverde/NGSCP.html.

  18. Inverted initial conditions: Exploring the growth of cosmic structure and voids

    NASA Astrophysics Data System (ADS)

    Pontzen, Andrew; Slosar, Anže; Roth, Nina; Peiris, Hiranya V.

    2016-05-01

    We introduce and explore "paired" cosmological simulations. A pair consists of an A and B simulation with initial conditions related by the inversion δA(x ,tinitial)=-δB(x ,tinitial) (underdensities substituted for overdensities and vice versa). We argue that the technique is valuable for improving our understanding of cosmic structure formation. The A and B fields are by definition equally likely draws from Λ CDM initial conditions, and in the linear regime evolve identically up to the overall sign. As nonlinear evolution takes hold, a region that collapses to form a halo in simulation A will tend to expand to create a void in simulation B. Applications include (i) contrasting the growth of A-halos and B-voids to test excursion-set theories of structure formation, (ii) cross-correlating the density field of the A and B universes as a novel test for perturbation theory, and (iii) canceling error terms by averaging power spectra between the two boxes. Generalizations of the method to more elaborate field transformations are suggested.

  19. Inverted initial conditions: Exploring the growth of cosmic structure and voids

    DOE PAGES

    Pontzen, Andrew; Roth, Nina; Peiris, Hiranya V.; Slosar, Anze

    2016-05-18

    We introduce and explore “paired” cosmological simulations. A pair consists of an A and B simulation with initial conditions related by the inversion δA(x,tinitial) = –δB(x,tinitial) (underdensities substituted for overdensities and vice versa). We argue that the technique is valuable for improving our understanding of cosmic structure formation. The A and B fields are by definition equally likely draws from ΛCDM initial conditions, and in the linear regime evolve identically up to the overall sign. As nonlinear evolution takes hold, a region that collapses to form a halo in simulation A will tend to expand to create a void inmore » simulation B. Applications include (i) contrasting the growth of A-halos and B-voids to test excursion-set theories of structure formation, (ii) cross-correlating the density field of the A and B universes as a novel test for perturbation theory, and (iii) canceling error terms by averaging power spectra between the two boxes. Furthermore, generalizations of the method to more elaborate field transformations are suggested.« less

  20. Can AERONET data be used to accurately model the monochromatic beam and circumsolar irradiances under cloud-free conditions in desert environment?

    NASA Astrophysics Data System (ADS)

    Eissa, Y.; Blanc, P.; Wald, L.; Ghedira, H.

    2015-12-01

    Routine measurements of the beam irradiance at normal incidence include the irradiance originating from within the extent of the solar disc only (DNIS), whose angular extent is 0.266° ± 1.7 %, and from a larger circumsolar region, called the circumsolar normal irradiance (CSNI). This study investigates whether the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic DNIS and CSNI under cloud-free conditions in a desert environment. The data from an AERONET station in Abu Dhabi, United Arab Emirates, and the collocated Sun and Aureole Measurement instrument which offers reference measurements of the monochromatic profile of solar radiance were exploited. Using the AERONET data both the radiative transfer models libRadtran and SMARTS offer an accurate estimate of the monochromatic DNIS, with a relative root mean square error (RMSE) of 6 % and a coefficient of determination greater than 0.96. The observed relative bias obtained with libRadtran is +2 %, while that obtained with SMARTS is -1 %. After testing two configurations in SMARTS and three in libRadtran for modelling the monochromatic CSNI, libRadtran exhibits the most accurate results when the AERONET aerosol phase function is presented as a two-term Henyey-Greenstein phase function. In this case libRadtran exhibited a relative RMSE and a bias of respectively 27 and -24 % and a coefficient of determination of 0.882. Therefore, AERONET data may very well be used to model the monochromatic DNIS and the monochromatic CSNI. The results are promising and pave the way towards reporting the contribution of the broadband circumsolar irradiance to standard measurements of the beam irradiance.

  1. Influence of Initial Geometry and Boundary Conditions on Flat Subduction Models and Resulting Topography

    NASA Astrophysics Data System (ADS)

    Nelson, P.; Moucha, R.

    2014-12-01

    Numerical investigations of surface deformation in response to flat slab subduction began with seminal papers by Bird (1988) and Mitrovica et al. (1989). Recently, a number of numerical studies have begun to explore the complexity in the dynamics of flat-slab subduction initiation and continuation, but did not address the corresponding surface deformation (English et al., 2003; Pérez-Campos et al., 2008; Liu et al., 2010; Jones et al., 2011; Arrial and Billen, 2013; Vogt and Gerya, 2014). Herein, we explore the conditions that lead to flat-slab subduction and characterize the resulting surface deformation using a 2D finite-difference marker-in-cell method. We specifically explore how initial model geometry and boundary conditions affect the evolution of the angle at which a slab subducts in the presence/absence of a buoyant oceanic plateau and the resulting surface topography. In our simulations, the surface is tracked through time as an internal erosion/sedimentation surface. The top boundary of the crust is overlaid by a "sticky" (viscous 10^17 Pa.s) water/air layer with correspondingly stratified densities. We apply a coupled surface processes model that solves the sediment transport/diffusion erosion equation at each time step to account for the corresponding crustal mass flux and its effect on crustal deformation. Model results show the initial angle of subduction has a substantial impact on the subduction angle of the slab and hence the evolution of topography. The results also indicate plate velocity and the presence of an oceanic plateau in a forced subduction only have a moderate effect on the angle of subduction.

  2. Tensor to scalar ratio and large scale power suppression from pre-slow roll initial conditions

    SciTech Connect

    Lello, Louis; Boyanovsky, Daniel E-mail: boyan@pitt.edu

    2014-05-01

    We study the corrections to the power spectra of curvature and tensor perturbations and the tensor-to-scalar ratio r in single field slow roll inflation with standard kinetic term due to initial conditions imprinted by a ''fast-roll'' stage prior to slow roll. For a wide range of initial inflaton kinetic energy, this stage lasts only a few e-folds and merges smoothly with slow-roll thereby leading to non-Bunch-Davies initial conditions for modes that exit the Hubble radius during slow roll. We describe a program that yields the dynamics in the fast-roll stage while matching to the slow roll stage in a manner that is independent of the inflationary potentials. Corrections to the power spectra are encoded in a ''transfer function'' for initial conditions T{sub α}(k), P{sub α}(k) = P{sup BD}{sub α}(k)T{sub α}(k), implying a modification of the ''consistency condition'' for the tensor to scalar ratio at a pivot scale k{sub 0}: r(k{sub 0}) = −8n{sub T}(k{sub 0}) [T{sub T}(k{sub 0})/T{sub R}(k{sub 0})]. We obtain T{sub α}(k) to leading order in a Born approximation valid for modes of observational relevance today. A fit yields T{sub α}(k) = 1+A{sub α}k{sup −p}cos [2πωk/H{sub sr}+φ{sub α}], with 1.5∼initial conditions. These corrections lead to both a suppression of the quadrupole and oscillatory features in both P{sub R}(k) and r(k{sub 0}) with a period of the order of the Hubble scale during slow roll inflation. The results are quite general and independent of the specific inflationary potentials, depending solely on the ratio of kinetic to potential energy κ and the slow roll parameters ε{sub V}, η{sub V} to leading order in slow roll. For a wide range of κ and the values of ε{sub V}; η{sub V} corresponding to the upper bounds from Planck, we find that the low quadrupole is consistent

  3. 10 CFR 40.53 - Conditions for licenses issued for initial transfer of certain items containing source material...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Conditions for licenses issued for initial transfer of... Section 40.53 Energy NUCLEAR REGULATORY COMMISSION DOMESTIC LICENSING OF SOURCE MATERIAL Transfer of Source Material § 40.53 Conditions for licenses issued for initial transfer of certain items...

  4. Effects of initial condition spectral content on shock-driven turbulent mixing.

    PubMed

    Nelson, Nicholas J; Grinstein, Fernando F

    2015-07-01

    The mixing of materials due to the Richtmyer-Meshkov instability and the ensuing turbulent behavior is of intense interest in a variety of physical systems including inertial confinement fusion, combustion, and the final stages of stellar evolution. Extensive numerical and laboratory studies of shock-driven mixing have demonstrated the rich behavior associated with the onset of turbulence due to the shocks. Here we report on progress in understanding shock-driven mixing at interfaces between fluids of differing densities through three-dimensional (3D) numerical simulations using the rage code in the implicit large eddy simulation context. We consider a shock-tube configuration with a band of high density gas (SF(6)) embedded in low density gas (air). Shocks with a Mach number of 1.26 are passed through SF(6) bands, resulting in transition to turbulence driven by the Richtmyer-Meshkov instability. The system is followed as a rarefaction wave and a reflected secondary shock from the back wall pass through the SF(6) band. We apply a variety of initial perturbations to the interfaces between the two fluids in which the physical standard deviation, wave number range, and the spectral slope of the perturbations are held constant, but the number of modes initially present is varied. By thus decreasing the density of initial spectral modes of the interface, we find that we can achieve as much as 25% less total mixing at late times. This has potential direct implications for the treatment of initial conditions applied to material interfaces in both 3D and reduced dimensionality simulation models. PMID:26274276

  5. Effects of Initial Condition Spectral Content on Shock Driven-Turbulent Mixing

    DOE PAGES

    Nelson, Nicholas James; Grinstein, Fernando F.

    2015-07-15

    The mixing of materials due to the Richtmyer-Meshkov instability and the ensuing turbulent behavior is of intense interest in a variety of physical systems including inertial confinement fusion, combustion, and the final stages of stellar evolution. Extensive numerical and laboratory studies of shock-driven mixing have demonstrated the rich behavior associated with the onset of turbulence due to the shocks. Here we report on progress in understanding shock-driven mixing at interfaces between fluids of differing densities through three-dimensional (3D) numerical simulations using the RAGE code in the implicit large eddy simulation context. We consider a shock-tube configuration with a band ofmore » high density gas (SF6) embedded in low density gas (air). Shocks with a Mach number of 1.26 are passed through SF6 bands, resulting in transition to turbulence driven by the Richtmyer-Meshkov instability. The system is followed as a rarefaction wave and a reflected secondary shock from the back wall pass through the SF6 band. We apply a variety of initial perturbations to the interfaces between the two fluids in which the physical standard deviation, wave number range, and the spectral slope of the perturbations are held constant, but the number of modes initially present is varied. By thus decreasing the density of initial spectral modes of the interface, we find that we can achieve as much as 25% less total mixing at late times. This has potential direct implications for the treatment of initial conditions applied to material interfaces in both 3D and reduced dimensionality simulation models.« less

  6. Effects of Initial Condition Spectral Content on Shock Driven-Turbulent Mixing

    SciTech Connect

    Nelson, Nicholas James; Grinstein, Fernando F.

    2015-07-15

    The mixing of materials due to the Richtmyer-Meshkov instability and the ensuing turbulent behavior is of intense interest in a variety of physical systems including inertial confinement fusion, combustion, and the final stages of stellar evolution. Extensive numerical and laboratory studies of shock-driven mixing have demonstrated the rich behavior associated with the onset of turbulence due to the shocks. Here we report on progress in understanding shock-driven mixing at interfaces between fluids of differing densities through three-dimensional (3D) numerical simulations using the RAGE code in the implicit large eddy simulation context. We consider a shock-tube configuration with a band of high density gas (SF6) embedded in low density gas (air). Shocks with a Mach number of 1.26 are passed through SF6 bands, resulting in transition to turbulence driven by the Richtmyer-Meshkov instability. The system is followed as a rarefaction wave and a reflected secondary shock from the back wall pass through the SF6 band. We apply a variety of initial perturbations to the interfaces between the two fluids in which the physical standard deviation, wave number range, and the spectral slope of the perturbations are held constant, but the number of modes initially present is varied. By thus decreasing the density of initial spectral modes of the interface, we find that we can achieve as much as 25% less total mixing at late times. This has potential direct implications for the treatment of initial conditions applied to material interfaces in both 3D and reduced dimensionality simulation models.

  7. Effect of Initial Conditions on Compressible Rayleigh-Taylor Instability and Transition to Turbulence

    NASA Astrophysics Data System (ADS)

    Miles, Aaron; Edwards, John; Greenough, Jeffrey

    2003-10-01

    The influence of the state of an initial interface over the subsequent evolutionary phases of the compressible Rayleigh-Taylor (RT) instability through the deep non-linear regime, transition to turbulence, and eventual asymptotic growth, remains a hotly debated topic. Apart from academic curiosity, there is a keen interest in this because RT instability in a form probably near transition can seriously diminish or even quench thermonuclear burn in double-shell ignition capsules being designed for the National Ignition Facility (NIF) (Amendt et al., Phys. Plas. 9(5),2221,(2002)). In addition to this, experimental test beds are being developed on high power laser facilities with a view to studying compressible turbulent mixing of relevance to the dynamics of supernovae explosions (Robey et al., Phys. Plasmas 10, 614 (2003)). In these experiments a high Mach number blast wave accelerates an interface with a specified, pre-machined initial spectrum, driving a brief phase of Richtmyer-Meshkov growth, followed by a sustained period of RT growth as the interface decelerates, much as in a supernova. While current facilities are barely powerful enough to edge the flow through a turbulent transition, the next generation of lasers such as the NIF will force the instability well beyond this making supernova relevant, turbulent experiments in the laboratory a real possibility. However, understanding the effects, if any, of the initial interface structure on the late time mixing in these small scale flows will clearly be an important aspect of this work. This talk will discuss the effect of initial interface conditions on the progress and structure of late time RT instability using results from the multi-physics, AMR, higher order Godunov Eulerian hydrocode, Raptor. Comparison with Omega experiments will be made and prospects for the NIF presented.

  8. Genome-Scale Metabolic Model for the Green Alga Chlorella vulgaris UTEX 395 Accurately Predicts Phenotypes under Autotrophic, Heterotrophic, and Mixotrophic Growth Conditions.

    PubMed

    Zuñiga, Cristal; Li, Chien-Ting; Huelsman, Tyler; Levering, Jennifer; Zielinski, Daniel C; McConnell, Brian O; Long, Christopher P; Knoshaug, Eric P; Guarnieri, Michael T; Antoniewicz, Maciek R; Betenbaugh, Michael J; Zengler, Karsten

    2016-09-01

    The green microalga Chlorella vulgaris has been widely recognized as a promising candidate for biofuel production due to its ability to store high lipid content and its natural metabolic versatility. Compartmentalized genome-scale metabolic models constructed from genome sequences enable quantitative insight into the transport and metabolism of compounds within a target organism. These metabolic models have long been utilized to generate optimized design strategies for an improved production process. Here, we describe the reconstruction, validation, and application of a genome-scale metabolic model for C. vulgaris UTEX 395, iCZ843. The reconstruction represents the most comprehensive model for any eukaryotic photosynthetic organism to date, based on the genome size and number of genes in the reconstruction. The highly curated model accurately predicts phenotypes under photoautotrophic, heterotrophic, and mixotrophic conditions. The model was validated against experimental data and lays the foundation for model-driven strain design and medium alteration to improve yield. Calculated flux distributions under different trophic conditions show that a number of key pathways are affected by nitrogen starvation conditions, including central carbon metabolism and amino acid, nucleotide, and pigment biosynthetic pathways. Furthermore, model prediction of growth rates under various medium compositions and subsequent experimental validation showed an increased growth rate with the addition of tryptophan and methionine. PMID:27372244

  9. Dynamic analysis of offshore structures with non-zero initial conditions in the frequency domain

    NASA Astrophysics Data System (ADS)

    Liu, Fushun; Lu, Hongchao; Li, Huajun

    2016-03-01

    The state of non-zero conditions is typically treated as fact when considering the dynamic analysis of offshore structures. This article extends a newly proposed method [1] to manage the non-zero initial conditions of offshore structures in the frequency domain, including new studies on original environmental loads reconstruction, response comparisons with the commercial software ANSYS, and a demonstration using an experimental cantilever beam. The original environmental loads, such as waves, currents, and winds, that act on a structure are decomposed into multiple complex exponential components are represented by a series of poles and corresponding residues. Counter to the traditional frequency-domain method, the non-zero initial conditions of offshore structures could be solved in the frequency domain. Compared with reference [1], an improvement reported in this article is that practical issues, including the choice of model order and central-processing-unit (CPU) time consumption, are further studied when applying this new method to offshore structures. To investigate the feasibility of the representation of initial environmental loads by their poles and corresponding residues, a measured random wave force collected from a column experiment at the Lab of Ocean University of China is used, decomposed, reconstructed and then compared with the original wave force; then, a numerical offshore platform is used to study the performance of the proposed method in detail. The numerical results of this study indicate that (1) a short duration of environmental loads are required to obtain their constitutive poles and residues, which implies good computational efficiency; and (2) the proposed method has a similar computational efficiency to traditional methods due to the use of the inverse Fourier transform technique. To better understand the performance, of time consumption and accuracy of the proposed method, the commercial software ANSYS is used to determine responses

  10. Nonminimally coupled inflation with initial conditions from a preinflation anamorphic contracting era

    NASA Astrophysics Data System (ADS)

    McDonald, John

    2016-08-01

    Inflation due to a nonminimally coupled scalar field, as first proposed by Salopek, Bardeen and Bond (SBB), is in good agreement with the observed value of the spectral index and constraints on the tensor-to-scalar ratio. Here we explore the possibility that SBB inflation represents the late stage of a Universe which emerges from an early contracting era. We present a model in which the Universe smoothly transitions from an anamorphic contracting era to late-time SBB inflation without encountering a singular bounce. This corresponds to a continuous expansion in the Einstein frame throughout. We show that the anamorphic contracting era is able to provide the smooth superhorizon initial conditions necessary for subsequent SBB inflation to occur. The model predicts corrections to the nonminimal coupling, kinetic term and potential of SBB inflation which can observably increase the spectral index relative to its SBB prediction.

  11. A simple method to calculate first-passage time densities with arbitrary initial conditions

    NASA Astrophysics Data System (ADS)

    Nyberg, Markus; Ambjörnsson, Tobias; Lizana, Ludvig

    2016-06-01

    Numerous applications all the way from biology and physics to economics depend on the density of first crossings over a boundary. Motivated by the lack of general purpose analytical tools for computing first-passage time densities (FPTDs) for complex problems, we propose a new simple method based on the independent interval approximation (IIA). We generalise previous formulations of the IIA to include arbitrary initial conditions as well as to deal with discrete time and non-smooth continuous time processes. We derive a closed form expression for the FPTD in z and Laplace-transform space to a boundary in one dimension. Two classes of problems are analysed in detail: discrete time symmetric random walks (Markovian) and continuous time Gaussian stationary processes (Markovian and non-Markovian). Our results are in good agreement with Langevin dynamics simulations.

  12. Accurate and high-resolution boundary conditions and flow fields in the first-class cabin of an MD-82 commercial airliner

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Wen, Jizhou; Chao, Jiangyue; Yin, Weiyou; Shen, Chen; Lai, Dayi; Lin, Chao-Hsin; Liu, Junjie; Sun, Hejiang; Chen, Qingyan

    2012-09-01

    Flow fields in commercial airliner cabins are crucial for creating a thermally comfortable and healthy cabin environment. Flow fields depend on the thermo-fluid boundary conditions at the diffusers, in addition to the cabin geometry and furnishing. To study the flow fields in cabins, this paper describes a procedure to obtain the cabin geometry, boundary conditions at the diffusers, and flow fields. This investigation used a laser tracking system and reverse engineering to generate a digital model of an MD-82 aircraft cabin. Even though the measuring error by the system was very small, approximations and assumptions were needed to reduce the workload and data size. The geometric model can also be easily used to calculate the space volume. A combination of hot-sphere anemometers (HSA) and ultrasonic anemometers (UA) were applied to obtain the velocity magnitude, velocity direction, and turbulence intensity at the diffusers. The measured results indicate that the flow boundary conditions in a real cabin were rather complex and the velocity magnitude, velocity direction, and turbulence intensity varied significantly from one slot opening to another. UAs were also applied to measure the three-dimensional air velocity at 20 Hz, which could also be used to determine the turbulence intensity. Due to the instability of the flow, it should at least be measured for 4 min to obtain accurate averaged velocity and turbulence information. It was found that the flow fields were of low speed and high turbulence intensity. This study provides high quality data for validating Computational Fluid Dynamics (CFD) models, including cabin geometry, boundary conditions of diffusers, and high-resolution flow field in the first-class cabin of a functional MD-82 commercial airliner.

  13. Still at the choice-point: action selection and initiation in instrumental conditioning.

    PubMed

    Balleine, Bernard W; Ostlund, Sean B

    2007-05-01

    Contrary to classic stimulus-response (S-R) theory, recent evidence suggests that, in instrumental conditioning, rats encode the relationship between their actions and the specific consequences that these actions produce. It has remained unclear, however, how encoding this relationship acts to control instrumental performance. Although S-R theories were able to give a clear account of how learning translates into performance, the argument that instrumental learning constitutes the acquisition of information of the form "response R leads to outcome O" does not directly imply a particular performance rule or policy; this information can be used both to perform R and to avoid performing R. Recognition of this problem has forced the development of accounts that allow the O and stimuli that predict the O (i.e., S-O) to play a role in the initiation of specific Rs. In recent experiments, we have used a variety of behavioral procedures in an attempt to isolate the processes that contribute to instrumental performance, including outcome devaluation, reinstatement, and Pavlovian-instrumental transfer. Our results, particularly from experiments assessing outcome-selective reinstatement, suggest that both "feed-forward" (O-R) and "feed-back" (R-O) associations are critical and that although the former appear to be important to response selection, the latter-together with processes that determine outcome value-mediate response initiation. We discuss a conceptual model that integrates these processes and its neural implementation.

  14. Cytoprotection by pre-emptive conditional phosphorylation of translation initiation factor 2

    PubMed Central

    Lu, Phoebe D; Jousse, Céline; Marciniak, Stefan J; Zhang, Yuhong; Novoa, Isabel; Scheuner, Donalyn; Kaufman, Randal J; Ron, David; Harding, Heather P

    2004-01-01

    Transient phosphorylation of the α-subunit of translation initiation factor 2 (eIF2α) represses translation and activates select gene expression under diverse stressful conditions. Defects in the eIF2α phosphorylation-dependent integrated stress response impair resistance to accumulation of malfolded proteins in the endoplasmic reticulum (ER stress), to oxidative stress and to nutrient deprivations. To study the hypothesized protective role of eIF2α phosphorylation in isolation of parallel stress signaling pathways, we fused the kinase domain of pancreatic endoplasmic reticulum kinase (PERK), an ER stress-inducible eIF2α kinase that is normally activated by dimerization, to a protein module that binds a small dimerizer molecule. The activity of this artificial eIF2α kinase, Fv2E-PERK, is subordinate to the dimerizer and is uncoupled from upstream stress signaling. Fv2E-PERK activation enhanced the expression of numerous stress-induced genes and protected cells from the lethal effects of oxidants, peroxynitrite donors and ER stress. Our findings indicate that eIF2α phosphorylation can initiate signaling in a cytoprotective gene expression pathway independently of other parallel stress-induced signals and that activation of this pathway can single-handedly promote a stress-resistant preconditioned state. PMID:14713949

  15. The one-point PDF of the initial conditions of our local Universe from the IRAS PSC redshift catalogue

    NASA Astrophysics Data System (ADS)

    Monaco, P.; Efstathiou, G.; Maddox, S. J.; Branchini, E.; Frenk, C. S.; McMahon, R. G.; Oliver, S. J.; Rowan-Robinson, M.; Saunders, W.; Sutherland, W. J.; Tadros, H.; White, S. D. M.

    2000-11-01

    The algorithm ztrace of Monaco & Efstathiou is applied to the IRAS PSCz catalogue to reconstruct the initial conditions of our local Universe with a resolution down to ~5h-1Mpc. The one-point probability distribution function (PDF) of the reconstructed initial conditions is consistent with the assumptions that: (i) IRAS galaxies trace mass on scales of ~5h-1Mpc and (ii) the statistics of the primordial density fluctuations are Gaussian. We use simulated PSCz catalogues, constructed from N-body simulations with Gaussian initial conditions, to show that local non-linear bias can cause the recovered initial PDF (assuming no bias) to be non-Gaussian. However, for plausible bias models, the distortions of the recovered PDF would be difficult to detect using the volume finely sampled by the PSCz catalogue. So, for Gaussian initial conditions, a range of bias models remain compatible with our PSCz reconstruction results.

  16. INITIAL CHEMICAL AND RESERVOIR CONDITIONS AT LOS AZUFRES WELLHEAD POWER PLANT STARTUP

    SciTech Connect

    Kruger, P.; Semprini, L.; Verma, S.; Barragan, R.; Molinar, R.; Aragon, A.; Ortiz, J.; Miranda, C.

    1985-01-22

    One of the major concerns of electric utilities in installing geothermal power plants is not only the longevity of the steam supply, but also the potential for changes in thermodynamic properties of the resource that might reduce the conversion efficiency of the design plant equipment. Production was initiated at Los Azufres geothermal field with wellhead generators not only to obtain electric energy at a relatively early date, but also to acquire needed information about the resource so that plans for large central power plants could be finalized. Commercial electric energy production started at Los Azufres during the summer of 1982 with five 5-MWe wellhead turbine-generator units. The wells associated with these units had undergone extensive testing and have since been essentially in constant production. The Los Azufres geothermal reservoir is a complex structural and thermodynamic system, intersected by at least 4 major parallel faults and producing geothermal fluids from almost all water to all steam. The five wellhead generators are associated with wells of about 30%, 60%, and 100% steam fraction. A study to compile existing data on the chemical and reservoir conditions during the first two years of operation has been completed. Data have been compiled on mean values of wellhead and separator pressures, steam and liquid flowrates, steam fraction, enthalpy, and pertinent chemical components. The compilation serves both as a database of conditions during the start-up period and as an initial point to observe changes with continued and increased production. Current plans are to add additional wellhead generators in about two years followed by central power plants when the data have been sufficiently evaluated for optimum plant design. During the next two years, the data acquired at the five 5-MWe wellhead generator units can be compared to this database to observe any significant changes in reservoir behavior at constant production.

  17. Improvement of boundary conditions for non-planar boundaries represented by polygons with an initial particle arrangement technique

    NASA Astrophysics Data System (ADS)

    Zhang, Tiangang; Koshizuka, Seiichi; Murotani, Kohei; Shibata, Kazuya; Ishii, Eiji; Ishikawa, Masanori

    2016-02-01

    The boundary conditions represented by polygons in moving particle semi-implicit (MPS) method (Koshizuka and Oka, Nuclear Science and Engineering, 1996) have been widely used in the industry simulations since it can simply simulate complex geometry with high efficiency. However, the inaccurate particle number density near non-planar wall boundaries dramatically affects the accuracy of simulations. In this paper, we propose an initial boundary particle arrangement technique coupled with the wall weight function method (Zhang et al. Transaction of JSCES, 2015) to improve the particle number density near slopes and curved surfaces with boundary conditions represented by polygons in three dimensions. Two uniform grids are utilized in the proposed technique. The grid points in the first uniform grid are used to construct boundary particles, and the second uniform grid stores the same information as in the work by Zhang et al. The wall weight functions of the grid points in the second uniform grid are calculated by newly constructed boundary particles. The wall weight functions of the fluid particles are interpolated from the values stored on the grid points in the second uniform grid. Because boundary particles are located on the polygons, complex geometries can be accurately represented. The proposed method can dramatically improve the particle number density and maintain the high efficiency. The performance of the previously proposed wall weight function (Zhang et al.) with the boundary particle arrangement technique is verified in comparison with the wall weight function without boundary particle arrangement by investigating two example geometries. The simulations of a water tank with a wedge and a complex geometry show the general applicability of the boundary particle arrangement technique to complex geometries and demonstrate its improvement of the wall weight function near the slopes and curved surfaces.

  18. Modeling large wind farms in conventionally neutral atmospheric boundary layers under varying initial conditions

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2014-05-01

    Atmospheric boundary layers (ABL) are frequently capped by an inversion layer limiting the entrainment rate and boundary layer growth. Commonly used analytical models state that the entrainment rate is inversely proportional to the inversion strength. The height of the inversion turns out to be a second important parameter. Conventionally neutral atmospheric boundary layers (CNBL) are ABLs with zero surface heat flux developing against a stratified free atmosphere. In this regime the inversion-filling process is merely driven by the downward heat flux at the inversion base. As a result, CNBLs are strongly dependent on the heating history of the boundary layer and strong inversions will fail to erode during the course of the day. In case of large wind farms, the power output of the farm inside a CNBL will depend on the height and strength of the inversion above the boundary layer. On the other hand, increased turbulence levels induced by wind farms may partially undermine the rigid lid effect of the capping inversion, enhance vertical entrainment of air into the farm, and increase boundary layer growth. A suite of large eddy simulations (LES) is performed to investigate the effect of the capping inversion on the conventionally neutral atmospheric boundary layer and on the wind farm performance under varying initial conditions. For these simulations our in-house pseudo-spectral LES code SP-Wind is used. The wind turbines are modelled using a non-rotating actuator disk method. In the absence of wind farms, we find that a decrease in inversion strength corresponds to a decrease in the geostrophic angle and an increase in entrainment rate and geostrophic drag. Placing the initial inversion base at higher altitudes further reduces the effect of the capping inversion on the boundary layer. The inversion can be fully neglected once it is situated above the equilibrium height that a truly neutral boundary layer would attain under the same external conditions such as

  19. Transcriptional initiation under conditions of anoxia-induced quiescence in mitochondria from Artemia franciscana embryos.

    PubMed

    Eads, Brian D; Hand, Steven C

    2003-02-01

    In response to anoxia, embryos of the brine shrimp Artemia franciscana are able coordinately to downregulate metabolism to levels low enough to permit survival for several years at room temperature. In addition to dramatic decreases in free ATP levels and heat production, intracellular pH drops from 7.8 to 6.3 overnight. Use of isolated mitochondria to study transcriptional responses to anoxia offers several advantages: (1). the localized nature of transcript initiation, processing and degradation, all of which may be followed in organello; (2). the relatively simple cis- and trans-machinery involved and (3). the ability to provide relevant physiological treatments in vitro. In response to anoxic incubation of embryos in vivo for 4 h followed by anoxic mitochondrial isolation and anoxic transcription assay at pH 6.4, a significant decrease in overall UTP incorporation (77%) was seen after 30 min relative to normoxic, pH 7.9 controls. A less severe inhibition of transcription under anoxia (52%) was observed compared with controls when pH was raised to 7.9. Similarly, under normoxia, the incubation at low pH (6.4) reduced transcription by 59%. Ribonuclease protection assays showed that the contribution of in vitro initiation during the assay fell from 78% at pH 7.9 to approximately 32% at pH 6.4 under either normoxic or anoxic conditions. DNA footprinting of putative transcriptional promoters revealed proteins at regular intervals upstream of the 12S rRNA in the control region, which previously had been indirectly inferred to contain promoters for H-strand transcription. The area between 1230 and 12065 contains a sequence in the tRNA(leu) gene believed to bind the transcription termination factor mTERF or TERM, and we provide the first evidence that this sequence is protein-bound in A. franciscana. However, our hypothesis that initiation is reduced at low pH because of a change in DNA binding by mitochondrial transcription factors was not confirmed. We propose that

  20. Conditions for initiating Lake Victoria haplochromine (Oreochromis esculentus) primary cell cultures from caudal fin biopsies.

    PubMed

    Filice, Melissa; Lee, C; Mastromonaco, Gabriela F

    2014-10-01

    The global decline of freshwater fishes has created a need to cryopreserve biological materials from endangered species in an effort to conserve the biodiversity within this taxon. Since maternal gametes and embryos from fish are difficult to cryopreserve, somatic cells obtained from caudal fins have become an increasingly popular resource as they contain both maternal and paternal DNA ensuring valuable traits are not lost from the population. Somatic cells stored in cryobanks can be used to supplement endangered populations with genetically valuable offspring with the use of assisted reproductive technologies. However, initiating primary cell cultures from caudal fin biopsies of endangered species can be challenging as standardized protocols have not yet been developed. The objective of this study was to identify culture conditions, including antibiotic supplementation, biopsy size, and culture temperature, suitable for establishing primary cell cultures of ngege (Oreochromis esculentus), a critically endangered African cichlid. Six-millimeter caudal fin biopsies provided sufficient material to develop a primary cell culture when incubated at 25°C using standard fish cell culture medium containing 1× Primocin. Further investigation and application of these culture conditions for other endangered freshwater fishes is necessary. PMID:24985486

  1. Blowup phenomena for the compressible euler and euler-poisson equations with initial functional conditions.

    PubMed

    Wong, Sen; Yuen, Manwai

    2014-01-01

    We study, in the radial symmetric case, the finite time life span of the compressible Euler or Euler-Poisson equations in R (N) . For time t ≥ 0, we can define a functional H(t) associated with the solution of the equations and some testing function f. When the pressure function P of the governing equations is of the form P = Kρ (γ) , where ρ is the density function, K is a constant, and γ > 1, we can show that the nontrivial C (1) solutions with nonslip boundary condition will blow up in finite time if H(0) satisfies some initial functional conditions defined by the integrals of f. Examples of the testing functions include r (N-1)ln(r + 1), r (N-1) e (r) , r (N-1)(r (3) - 3r (2) + 3r + ε), r (N-1)sin((π/2)(r/R)), and r (N-1)sinh r. The corresponding blowup result for the 1-dimensional nonradial symmetric case is also given.

  2. Welfare Conditions of Donkeys in Europe: Initial Outcomes from On-Farm Assessment

    PubMed Central

    Dai, Francesca; Dalla Costa, Emanuela; Murray, Leigh Margareth Anne; Canali, Elisabetta; Minero, Michela

    2016-01-01

    Simple Summary This paper aims to present the first outcomes of data collected using the AWIN welfare assessment protocol for donkeys in 20 EU donkey facilities. Three assessors evaluated 278 donkeys. The authors found recurrent issues: tendency to obesity, lack of hoof care and irregular positive interactions with humans. The protocol proved to be applicable in different management conditions and for donkeys of different attitude. Abstract This paper is a baseline study to present the initial outcomes of data collected in a sample of EU donkey farms using the AWIN welfare assessment protocol for donkeys, comprehensive of 22 valid, reliable and feasible animal-based indicators. A total of 20 donkey facilities (N = 12 in Italy and N = 8 in United Kingdom) were visited and 278 donkeys of different breed, aged 2–45 years, were assessed. Three assessors underwent a common training period to learn how to perform and score all the indicators included in the protocol. Data was collected using digitalized systems and downloaded to a database. A descriptive statistic for each welfare indicator was calculated. The authors found recurrent issues: 25% of donkeys were moderately over weight; although most of the assessed animals had good quality hoof care, 15.16% of them presented some signs of neglect, such as overgrowth and/or incorrect trimming; 18.05% of donkeys showed an avoidance reaction to an approaching human in the avoidance distance test. The protocol has proven to be applicable in different management conditions and for donkeys of different attitude. PMID:26761034

  3. Note on starting the Numerov method more accurately by a hybrid formula of order four for an initial--value problem

    NASA Astrophysics Data System (ADS)

    Adee, S. O.; Onumanyi, P.; Sirisena, U. W.; Yahaya, Y. A.

    2005-03-01

    In this note we report a hybrid formula of order four for starting the Numerov method applied to the initial--value problem for y''=f(x,y), over the recently obtained result of order three by two different papers (J. Pure Appl. Sci. 2(2) (2002) 1, Abacus 29(2) (2002) 92), based on two different approaches. We illustrate the accuracy of the methods by two numerical examples.

  4. Initial conditions of formation of starburst clusters: constraints from stellar dynamics

    NASA Astrophysics Data System (ADS)

    Banerjee, Sambaran; Kroupa, Pavel

    2015-08-01

    Recent high resolution observations of dense regions of molecular clouds and massive gaseous clumps with instruments like Herschel and ALMA have revealed intricate and filamentary overdensity structures in them. Such progenitors of massive starburst clusters are in contrast with smooth, centrally-pronounced profiles of the latter. In this work, we intend to constrain massive, substructured stellar distributions that would evolve to cluster-like profiles at very young ages (~Myr), as seen in starburst clusters. Taking the well observed NGC3603 Young Cluster (NYC) as an example, we compute the infall and final merger of filament-like compact (0.1-0.3 pc) subclusters, totalling 10000 M_sun, from a range of spatial scales and modes of sub-clustering, using direct N-body calculations. These calculations infer an allowable span of approx. 2.5 pc from which the subclusters can fall in a gas potential and merge to form a single centrally-dense structure in near dynamical equilibrium, within the young age of NYC (1-2 Myr). However, these merged clusters are too compact and centrally overdense compared to typical young clusters. Our N-body calculations, beginning from such compact initial conditions, show that even stellar wind and supernova mass loss, dynamical heating from retaining black holes, external tidal field and heating due to tight O-star binaries together cannot expand these clusters to their observed sizes, even in 100 Myr. Hence an explosive gas dispersal phase seems essential for forming starburst and other young clusters observed in the Milky Way and in the Local Group which can expand the clusters to their observed sizes and concentrations; including that for NYC with approx. 30% clump star formation efficiency. However, some observed massive but highly extended (>10 pc) , >10 Myr old clusters better fit a slow (several Myr timescale) gas dispersal from parsec-scale initial profiles, which can be the future of embedded systems like W3 Main.

  5. Boreal Winter Predictions with the GEOS-2 GCM: The Role of Boundary Forcing and Initial Conditions

    NASA Technical Reports Server (NTRS)

    Chang, Yehui; Schubert, Siegfried D.; Suarez, Max J.

    1998-01-01

    Ensembles of atmospheric General Circulation Model (GCM) seasonal forecasts and long-term simulations (1980-94) are analyzed to assess the controlling influences of boundary forcing and memory of the initial conditions. Both the forecasts and simulations are carried out with version 2 of the Goddard Earth Observing System (GEOS-2) GCM forced with observed sea surface temperatures (SSTs). While much of the focus is on the seasonal time scale (January- March) and the Pacific North American (PNA) region, we also present results for other regions, shorter time scales, and other known modes of variability in the northern hemisphere extratropics. Forecasts of indices of some of the key large-scale modes of variability show that there is considerable variability in skill between different regions of the Northern Hemisphere. The eastern North Atlantic region has the poorest long lead forecast skill showing no skill beyond about 10 days. Skillful seasonal forecasts are primarily confined to the wave-like ENSO response emanating from the tropical Pacific. In the Northern Hemisphere, this is associated with the well-known Pacific/North American (PNA) pattern. Memory of the initial conditions is the major factor leading to skillful extratropical forecasts of lead time less than one month, while SST forcing is the only factor at the seasonal time scale. SST forcing contributes to skillful forecasts at sub- seasonal time scales only over the PNA region. The GEOS-2 GCM produces average (1980-94) signal to noise ratios which are less than one everywhere in the extratropics, except for the subtropical Pacific where they approach 1.5. When confined to the ENSO years, the maximum signal to noise ratios occur in the PNA region where they exceed three. An assessment of the sampling distribution of the forecasts suggests the model's ENSO response is very likely too weak. These results show some sensitivity to the uncertainties in the estimates of the SST forcing fields. In the North

  6. Hydrologic modification to improve habitat in riverine lakes: Management objectives, experimental approach, and initial conditions

    USGS Publications Warehouse

    Johnson, Barry L.; Barko, John W.; Gerasimov, Yuri; James, William F.; Litvinov, Alexander; Naimo, Teresa J.; Wiener, James G.; Gaugush, Robert F.; Rogala, James T.; Rogers, Sara J.; Schoettger, R.A.

    1996-01-01

    The Finger Lakes habitat-rehabilitation project is intended to improve physical and chemical conditions for fish in six connected back water lakes in Navigation Pool 5 of the upper Missouri River. The primary management objective is to improve water temperature, dissolved oxygen concentration and current velocity during winter for bluegills, Lepomis macrochirus, and black crappies, Pomoxis nigromaculatus, two of the primary sport fishes in the lakes. The lakes will be hydrologically altered by Installing culverts to Introduce controlled flows of oxygenated water into four lakes, and an existing unregulated culvert on a fifth lake will be equipped with a control gate to regulate inflow. These habitat modifications constitute a manipulative field experiment that will compare pre-project (1991 to summer 1993) and post-project (fall 1993 to 1996) conditions in the lakes, including hydrology, chemistry, rooted vegetation, and fish and macroinvertebrate communities. Initial data indicate that the Finger Lakes differ in water chemistry, hydrology, and macrophyte abundance. Macroinvertebrate communities also differed among lakes: species diversity was highest in lakes with dense aquatic macrophytes. The system seems to support a single fish community, although some species concentrated in individual lakes at different times. The introduction of similar flows into five of the lakes will probably reduce the existing physical and chemical differences among lakes. However, our ability to predict the effects of hydrologic modification on fish populations is limited by uncertainties concerning both the interactions of temperature, oxygen and current in winter and the biological responses of primary and secondary producers. Results from this study should provide guidance for similar habitat-rehabilitation projects in large rivers.

  7. The charged inflaton and its gauge fields: preheating and initial conditions for reheating

    NASA Astrophysics Data System (ADS)

    Lozanov, Kaloian D.; Amin, Mustafa A.

    2016-06-01

    We calculate particle production during inflation and in the early stages of reheating after inflation in models with a charged scalar field coupled to Abelian and non-Abelian gauge fields. A detailed analysis of the power spectra of primordial electric fields, magnetic fields and charge fluctuations at the end of inflation and preheating is provided. We carefully account for the Gauss constraints during inflation and preheating, and clarify the role of the longitudinal components of the electric field. We calculate the timescale for the back-reaction of the produced gauge fields on the inflaton condensate, marking the onset of non-linear evolution of the fields. We provide a prescription for initial conditions for lattice simulations necessary to capture the subsequent nonlinear dynamics. On the observational side, we find that the primordial magnetic fields generated are too small to explain the origin of magnetic fields on galactic scales and the charge fluctuations are well within observational bounds for the models considered in this paper.

  8. The CFL condition for spectral approximations to hyperbolic initial-boundary value problems

    NASA Technical Reports Server (NTRS)

    Gottlieb, David; Tadmor, Eitan

    1990-01-01

    The stability of spectral approximations to scalar hyperbolic initial-boundary value problems with variable coefficients are studied. Time is discretized by explicit multi-level or Runge-Kutta methods of order less than or equal to 3 (forward Euler time differencing is included), and spatial discretizations are studied by spectral and pseudospectral approximations associated with the general family of Jacobi polynomials. It is proved that these fully explicit spectral approximations are stable provided their time-step, delta t, is restricted by the CFL-like condition, delta t less than Const. N(exp-2), where N equals the spatial number of degrees of freedom. We give two independent proofs of this result, depending on two different choices of approximate L(exp 2)-weighted norms. In both approaches, the proofs hinge on a certain inverse inequality interesting for its own sake. The result confirms the commonly held belief that the above CFL stability restriction, which is extensively used in practical implementations, guarantees the stability (and hence the convergence) of fully-explicit spectral approximations in the nonperiodic case.

  9. Welfare Conditions of Donkeys in Europe: Initial Outcomes from On-Farm Assessment.

    PubMed

    Dai, Francesca; Dalla Costa, Emanuela; Murray, Leigh Margareth Anne; Canali, Elisabetta; Minero, Michela

    2016-01-01

    This paper is a baseline study to present the initial outcomes of data collected in a sample of EU donkey farms using the AWIN welfare assessment protocol for donkeys, comprehensive of 22 valid, reliable and feasible animal-based indicators. A total of 20 donkey facilities (N = 12 in Italy and N = 8 in United Kingdom) were visited and 278 donkeys of different breed, aged 2-45 years, were assessed. Three assessors underwent a common training period to learn how to perform and score all the indicators included in the protocol. Data was collected using digitalized systems and downloaded to a database. A descriptive statistic for each welfare indicator was calculated. The authors found recurrent issues: 25% of donkeys were moderately over weight; although most of the assessed animals had good quality hoof care, 15.16% of them presented some signs of neglect, such as overgrowth and/or incorrect trimming; 18.05% of donkeys showed an avoidance reaction to an approaching human in the avoidance distance test. The protocol has proven to be applicable in different management conditions and for donkeys of different attitude.

  10. Evidence for the role of environmental agents in the initiation or progression of autoimmune conditions.

    PubMed Central

    Powell, J J; Van de Water, J; Gershwin, M E

    1999-01-01

    The concordance of autoimmune disease among identical twins is virtually always less than 50% and often in the 25-40% range. This observation, as well as epidemic clustering of some autoimmune diseases following xenobiotic exposure, reinforces the thesis that autoimmune disease is secondary to both genetic and environmental factors. Because nonliving agents do not have genomes, disease characteristics involving nonliving xenobiotics are primarily secondary to host phenotype and function. In addition, because of individual genetic susceptibilities based not only on major histocompatibility complex differences but also on differences in toxin metabolism, lifestyles, and exposure rates, individuals will react differently to the same chemicals. With these comments in mind it is important to note that there have been associations of a number of xenobiotics with human autoimmune disease, including mercury, iodine, vinyl chloride, canavanine, organic solvents, silica, l-tryptophan, particulates, ultraviolet radiation, and ozone. In addition, there is discussion in the literature that raises the possibility that xenobiotics may also exacerbate an existing autoimmune disease. In this article we discuss these issues and, in particular, the evidence for the role of environmental agents in the initiation or progression of autoimmune conditions. With the worldwide deterioration of the environment, this is a particularly important subject for human health. PMID:10970167

  11. Does complex absorption behavior leading to conditioning and damage in KDP/DKDP reflect the electronic structure of initiators?

    SciTech Connect

    Feit, M D; DeMange, P P; Negres, R A; Rubenchik, A M; Demos, S G

    2007-10-24

    Currently, most of our thinking about the defects responsible for initiating laser damage considers them as featureless absorbers. However, an increasing body of evidence, particularly involving multi-wavelength irradiation, suggests electronic structure of damage initiators is important in determining both initiation and conditioning behaviors in KDP. The effective absorption coefficient of energy under multi-wavelength irradiation cannot be accounted for by a structureless absorber, but is consistent with an initiator with a multi-level structure. We outline the evidence and assess the ability of such a simple multi-level model to explain these and other experimentally observed behaviors.

  12. Attribution of soil moisture dynamics - Initial conditions vs. atmospheric forcing and the role of climate change

    NASA Astrophysics Data System (ADS)

    Orth, Rene; Seneviratne, Sonia I.

    2014-05-01

    conditions versus the atmospheric forcing for monthly soil moisture variations. We find that initial soil moisture anomalies are overall more important than the forcing, even if less pronounced in summer. Especially in southern Europe we show high drought forecasting potential, whereas the forcing is more important in Central and North-eastern Europe.

  13. Stochastic modeling of crack initiation and short-crack growth under creep and creep-fatigue conditions

    NASA Technical Reports Server (NTRS)

    Kitamura, Takayuki; Ghosn, Louis J.; Ohtani, Ryuichi

    1992-01-01

    A simplified stochastic model is proposed for crack initiation and short-crack growth under creep and creep-fatigue conditions. Material inhomogeneity provides the random nature of crack initiation and early growth. In the model, the influence of microstructure is introduced by the variability of: (1) damage accumulation along grain boundaries, (2) critical damage required for crack initiation or growth, and (3) the grain-boundary length. The probabilities of crack initiation and growth are derived by using convolution integrals. The model is calibrated and used to predict the crack density and crack-growth rate of short cracks of 304 stainless steel under creep and creep-fatigue conditions. The mean-crack initiation lives are predicted to be within an average deviation of about 10 percent from the experimental results. The predicted comulative distributions of crack-growth rate follow the experimental data closely. The applicability of the simplified stochastic model is discussed and the future research direction is outlined.

  14. Stochastic modeling of crack initiation and short-crack growth under creep and creep-fatigue conditions

    NASA Technical Reports Server (NTRS)

    Kitamura, Takayuki; Ghosn, Louis J.; Ohtani, Ryuichi

    1989-01-01

    A simplified stochastic model is proposed for crack initiation and short-crack growth under creep and creep-fatigue conditions. Material inhomogeneity provides the random nature of crack initiation and early growth. In the model, the influence of microstructure is introduced by the variability of: (1) damage accumulation along grain boundaries, (2) critical damage required for crack initiation or growth, and (3) the grain-boundary length. The probabilities of crack initiation and growth are derived by using convolution integrals. The model is calibrated and used to predict the crack density and crack-growth rate of short cracks of 304 stainless steel under creep and creep-fatigue conditions. The mean-crack initiation lives are predicted to be within an average deviation of about 10 percent from the experimental results. The predicted cumulative distributions of crack-growth rate follow the experimental data closely. The applicability of the simplified stochastic model is discussed and the future research direction is outlined.

  15. The Murine Norovirus Core Subgenomic RNA Promoter Consists of a Stable Stem-Loop That Can Direct Accurate Initiation of RNA Synthesis

    PubMed Central

    Yunus, Muhammad Amir; Lin, Xiaoyan; Bailey, Dalan; Karakasiliotis, Ioannis; Chaudhry, Yasmin; Vashist, Surender; Zhang, Guo; Thorne, Lucy; Kao, C. Cheng

    2014-01-01

    ABSTRACT All members of the Caliciviridae family of viruses produce a subgenomic RNA during infection. The subgenomic RNA typically encodes only the major and minor capsid proteins, but in murine norovirus (MNV), the subgenomic RNA also encodes the VF1 protein, which functions to suppress host innate immune responses. To date, the mechanism of norovirus subgenomic RNA synthesis has not been characterized. We have previously described the presence of an evolutionarily conserved RNA stem-loop structure on the negative-sense RNA, the complementary sequence of which codes for the viral RNA-dependent RNA polymerase (NS7). The conserved stem-loop is positioned 6 nucleotides 3′ of the start site of the subgenomic RNA in all caliciviruses. We demonstrate that the conserved stem-loop is essential for MNV viability. Mutant MNV RNAs with substitutions in the stem-loop replicated poorly until they accumulated mutations that revert to restore the stem-loop sequence and/or structure. The stem-loop sequence functions in a noncoding context, as it was possible to restore the replication of an MNV mutant by introducing an additional copy of the stem-loop between the NS7- and VP1-coding regions. Finally, in vitro biochemical data suggest that the stem-loop sequence is sufficient for the initiation of viral RNA synthesis by the recombinant MNV RNA-dependent RNA polymerase, confirming that the stem-loop forms the core of the norovirus subgenomic promoter. IMPORTANCE Noroviruses are a significant cause of viral gastroenteritis, and it is important to understand the mechanism of norovirus RNA synthesis. Here we describe the identification of an RNA stem-loop structure that functions as the core of the norovirus subgenomic RNA promoter in cells and in vitro. This work provides new insights into the molecular mechanisms of norovirus RNA synthesis and the sequences that determine the recognition of viral RNA by the RNA-dependent RNA polymerase. PMID:25392209

  16. Initial Conditions for Optimal Growth in a Coupled Ocean-Atmosphere Model of ENSO*.

    NASA Astrophysics Data System (ADS)

    Thompson, C. J.

    1998-02-01

    Several studies have examined the conditions in the equatorial Pacific basin that lead to the maximum growth over a fixed time period, . These studies have the purpose of finding the characteristic precursor to an ENSO warm event, or more generally to explore error growth and predictability of the coupled ocean-atmosphere system. This paper develops a linearized version of the Battisti model (similar to the Zebiak-Cane model) with a time-invariant background state. The optimal initial conditions for time period (-optimals) were computed for a range of and for a selection of background states.A number of interesting characteristics of the -optimals emerged: 1) The -optimals grow more quickly than even the most unstable mode (the ENSO mode) of the system. 2) The -optimals develop quickly into the ENSO mode-in around 90 days. 3) The ENSO mode produced by a given -optimal does not in general peak at time . For less than 360 days the ENSO modes peak after time , and for greater than 360 days the ENSO mode first peaks before . At 360 days, designated max, the ENSO mode peaks at : this is also the -optimal, which produces the most growth. 4) Optimals were produced that used the SST only (T-optimals) and that used only the ocean dynamics (r-optimals). It is shown that for greater than 60 days, these two optimals both produce ENSO modes (of the same phase). This result makes a comparison of the relative importance of the SST versus the ocean dynamics straightforward: A T-optimal pattern with a 0.1 degree anomaly produces the same size ENSO as an r-optimal pattern with 1.2-m thermocline anomaly. 5) It is shown that the full optimal is the linear combination of these two suboptimals, where their relative sizes are determined by their relative weights (in the norm used).The paper also experiments with a neutral and a damped version of the model

  17. A new large initial condition ensemble to assess avoided impacts in a climate mitigation scenario

    NASA Astrophysics Data System (ADS)

    Sanderson, B. M.; Tebaldi, C.; Knutti, R.; Oleson, K. W.

    2014-12-01

    It has recently been demonstrated that when considering timescales of up to 50 years, natural variability may play an equal role to anthropogenic forcing on subcontinental trends for a variety of climate indicators. Thus, for many questions assessing climate impacts on such time and spatial scales, it has become clear that a significant number of ensemble members may be required to produce robust statistics (and especially so for extreme events). However, large ensemble experiments to date have considered the role of variability in a single scenario, leaving uncertain the relationship between the forced climate trajectory and the variability about that path. To address this issue, we present a new, publicly available, 15 member initial condition ensemble of 21st century climate projections for the RCP 4.5 scenario using the CESM1.1 Earth System Model, which we propose as a companion project to the existing 40 member CESM large ensemble which uses the higher greenhouse gas emission future of RCP8.5. This provides a valuable data set for assessing what societal and ecological impacts might be avoided through a moderate mitigation strategy in contrast to a fossil fuel intensive future. We present some early analyses of these combined ensembles to assess to what degree the climate variability can be considered to combine linearly with the underlying forced response. In regions where there is no detectable relationship between the mean state and the variability about the mean trajectory, then linear assumptions can be trivially exploited to utilize a single ensemble or control simulation to characterize the variability in any scenario of interest. We highlight regions where there is a detectable nonlinearity in extreme event frequency, how far in the future they will be manifested and propose mechanisms to account for these effects.

  18. Cosmic shear statistics in cosmologies with non-Gaussian initial conditions

    NASA Astrophysics Data System (ADS)

    Fedeli, C.; Moscardini, L.

    2010-06-01

    We computed the power spectrum of weak cosmic shear in models with non-Gaussian primordial density fluctuations. Cosmological initial conditions deviating from Gaussianity have recently attracted much attention in the literature, especially with respect to their effect on the formation of non-linear structures and because of the bounds that they can put on the inflationary epoch. The fully non-linear matter power spectrum was evaluated with the use of the physically motivated, semi-analytic halo model, where the mass function and linear halo bias were suitably corrected for non-Gaussian cosmologies. In agreement with previous work, we found that a level of non-Gaussianity compatible with cosmic microwave background bounds and with positive skewness produces an increase in power of the order of a few per cent at intermediate scales. We then used the matter power spectrum, together with observationally motivated background source redshift distributions in order to compute the cosmological weak-lensing power spectrum. We found that the degree of deviation from the power spectrum of the reference Gaussian model is small compared to the statistical error expected from even future weak-lensing surveys. However, summing the signal over a large range of multipoles can beat down the noise, bringing to a significant detection of non-Gaussianity at the level of few tens, when all other cosmological parameters are held fixed. Finally, we have shown that the constraints on the level of non-Gaussianity can be improved by ~ 20 per cent with the use of weak-lensing tomography.

  19. Scuffing initiation in metals sliding against copper under non-lubricated conditions

    SciTech Connect

    Kovalchenko, A M; Blau, Peter Julian; Qu, Jun; Danyluk, S

    2011-01-01

    Metallic components in sliding contact are sometimes subjected to high-loads with little or no lubrication. Such starved conditions can lead to a phenomenon called scuffing. Various definitions exist for this term, but in the present case, three criteria were used to signal its onset: changes in friction, vibrations, and noise, coupled with surface examination. On this basis, scuffing initiation was determined for seven technically pure metals (Al, Mo, Nb, Ta, Ti, W, Cu) and stainless steel, all rubbing against Cu. A flat-ended pin-on-disk test configuration was used with normal loads of 1-3 N, and with step-wise increases in sliding speed from 0.16 to 2.56 m/s. Al was only weakly resistant to scuffing, presumably due to its solubility in Cu, its high ductility and its relatively low elastic modulus. Niobium provided satisfactory sliding behavior at low speeds and loads, presumably due to protective oxides; however, it scuffed at higher loads when the oxide broke through. Stainless steel, Mo, and Ta had higher friction coefficients than Al and Nb, presumably because the relatively high strengths of the former prevented severe wear even when their oxide films failed. Like Al, Ti scuffs on Cu, probably because of its high relative solubility; however, Ti's higher elastic modulus resists the more severe forms of surface damage than does Al. Of all the materials slid against Cu, W displayed the least scuffing, even under maximum speed and load. Tungsten's negligible solubility in Cu may have reduced its adhesion, and W's high elastic modulus resisted shear-deformation, even at high frictional heating. Self-mated Cu couple scuffed when the speed was increased. The oxides on the Cu surface serve as solid lubricant avoiding scuffing at lower speeds.

  20. STAR FORMATION AT VERY LOW METALLICITY. IV. FRAGMENTATION DOES NOT DEPEND ON METALLICITY FOR COLD INITIAL CONDITIONS

    SciTech Connect

    Jappsen, Anne-Katharina; Klessen, Ralf S.; Glover, Simon C. O.; Mac Low, Mordecai-Mark E-mail: rklessen@ita.uni-heidelberg.de

    2009-05-10

    Primordial star formation appears to result in stars at least an order of magnitude more massive than modern star formation. It has been proposed that the transition from primordial to modern initial mass functions occurs due to the onset of effective metal-line cooling at a metallicity Z/Z {sub sun} = 10{sup -3.5}. However, these simulations neglected molecular hydrogen cooling. We perform simulations using the same initial conditions, but including molecular cooling, using a complex network that follows molecular hydrogen formation and also directly follows carbon monoxide and water. We find that molecular hydrogen cooling allows roughly equivalent fragmentation to proceed even at zero metallicity for these initial conditions. The apparent transition just represents the point where metal-line cooling becomes more important than molecular cooling. In all cases, the fragments are massive enough to be consistent with models of primordial stellar masses, suggesting that the transition to the modern initial mass function may be determined by other physics such as dust formation. We conclude that such additional cooling mechanisms, combined with the exact initial conditions produced by cosmological collapse are likely more important than metal-line cooling in determining the initial mass function, and thus that there is unlikely to be a sharp transition in the initial mass function at Z/Z {sub sun} = 10{sup -3.5}.

  1. Sensitivity of CFC-11 uptake to physical initial conditions and interannually varying surface forcing in a global ocean model

    NASA Astrophysics Data System (ADS)

    Danabasoglu, Gokhan; Peacock, Synte; Lindsay, Keith; Tsumune, Daisuke

    Sensitivity of the oceanic chlorofluorocarbon CFC-11 uptake to physical initial conditions and surface dynamical forcing (heat and salt fluxes and wind stress) is investigated in a global ocean model used in climate studies. Two different initial conditions are used: a solution following a short integration starting with observed temperature and salinity and zero velocities, and the quasi-equilibrium solution of an independent integration. For surface dynamical forcing, recently developed normal-year and interannually varying (1958-2000) data sets are used. The model CFC-11 global and basin inventories, particularly in the normal-year forcing case, are below the observed mean estimates, but they remain within the observational error bars. Column inventory spatial distributions indicate nontrivial differences due to both initial condition and forcing changes, particularly in the northern North Atlantic and Southern Ocean. These differences are larger between forcing sensitivity experiments than between the initial condition cases. The comparisons along the A16N and SR3 WOCE sections also show differences between cases. However, comparisons with observations do not clearly favor a particular case, and model-observation differences remain much larger than model-model differences for all simulations. The choice of initial condition does not significantly change the CFC-11 distributions. Both because of locally large differences between normal-year and interannually varying simulations and because the dynamical and CFC-11 forcing calendars are synchronized, we favor using the more realistic interannually varying forcing in future simulations, given the availability of the forcing data sets.

  2. A CLUSTER IN THE MAKING: ALMA REVEALS THE INITIAL CONDITIONS FOR HIGH-MASS CLUSTER FORMATION

    SciTech Connect

    Rathborne, J. M.; Contreras, Y.; Longmore, S. N.; Bastian, N.; Jackson, J. M.; Alves, J. F.; Bally, J.; Foster, J. B.; Garay, G.; Kruijssen, J. M. D.; Testi, L.; Walsh, A. J.

    2015-04-01

    G0.253+0.016 is a molecular clump that appears to be on the verge of forming a high-mass cluster: its extremely low dust temperature, high mass, and high density, combined with its lack of prevalent star formation, make it an excellent candidate for an Arches-like cluster in a very early stage of formation. Here we present new Atacama Large Millimeter/Sub-millimeter Array observations of its small-scale (∼0.07 pc) 3 mm dust continuum and molecular line emission from 17 different species that probe a range of distinct physical and chemical conditions. The data reveal a complex network of emission features with a complicated velocity structure: there is emission on all spatial scales, the morphology of which ranges from small, compact regions to extended, filamentary structures that are seen in both emission and absorption. The dust column density is well traced by molecules with higher excitation energies and critical densities, consistent with a clump that has a denser interior. A statistical analysis supports the idea that turbulence shapes the observed gas structure within G0.253+0.016. We find a clear break in the turbulent power spectrum derived from the optically thin dust continuum emission at a spatial scale of ∼0.1 pc, which may correspond to the spatial scale at which gravity has overcome the thermal pressure. We suggest that G0.253+0.016 is on the verge of forming a cluster from hierarchical, filamentary structures that arise from a highly turbulent medium. Although the stellar distribution within high-mass Arches-like clusters is compact, centrally condensed, and smooth, the observed gas distribution within G0.253+0.016 is extended, with no high-mass central concentration, and has a complex, hierarchical structure. If this clump gives rise to a high-mass cluster and its stars are formed from this initially hierarchical gas structure, then the resulting cluster must evolve into a centrally condensed structure via a dynamical process.

  3. Initial Accuracy of HIV Rapid Test Kits Stored in Suboptimal Conditions and Validity of Delayed Reading of Oral Fluid Tests

    PubMed Central

    Choko, Augustine T.; Taegtmeyer, Miriam; MacPherson, Peter; Cocker, Derek; Khundi, McEwen; Thindwa, Deus; Sambakunsi, Rodrick S.; Kumwenda, Moses K.; Chiumya, Kondwani; Malema, Owen; Makombe, Simon D.; Webb, Emily L.; Corbett, Elizabeth L.

    2016-01-01

    Objectives To evaluate the effect of storing commonly used rapid diagnostic tests above manufacturer-recommended temperature (at 37°C), and the accuracy of delayed reading of oral fluid kits with relevance to HIV self-testing programmes. Design A quality assurance study of OraQuick (OraSure), Determine HIV 1/2™ (Alere) and Uni-Gold™ (Recombigen®). Methods Consecutive adults (≥18y) attending Ndirande Health Centre in urban Blantyre, Malawi in January to April 2012 underwent HIV testing with two of each of the three rapid diagnostic test kits stored for 28 days at either 18°C (optimally-stored) or at 37°C (pre-incubated). Used OraQuick test kits were stored in a laboratory for delayed day 1 and subsequent monthly re-reading was undertaken for one year. Results Of 378 individuals who underwent parallel testing, 5 (1.3%) were dropped from the final analysis due to discordant or missing reference standard results (optimally-stored Determine and Uni-Gold). Compared to the diagnostic reference standard, OraQuick had a sensitivity of 97.2% (95% CI: 93.6–99.6). There were 7 false negative results among all test kits stored at 37°C and three false negatives among optimally stored kits. Excellent agreement between pre-incubated tests and optimally-stored tests with Kappa values of 1.00 for Determine and Uni-Gold; and 0.97 (95% CI: 0.95; 1.00) for OraQuick were observed. There was high visual stability on re-reading of OraQuick, with only 1/375 pre-incubated and 1/371 optimally-stored OraQuick kits changing from the initial result over 12 months. Conclusion Erroneous results observed during HIV testing in low income settings are likely to be due to factors other than suboptimal storage conditions. Re-reading returned OraQuick kits may offer a convenient and accurate quality assurance approach, including in HIV self-testing programmes. PMID:27336161

  4. Prazosin differentially affects extinction of cocaine conditioned place preference on the basis of dose and initial preference.

    PubMed

    Bernardi, Rick E; Lattal, K Matthew

    2012-12-19

    Recent work has shown that α1-adrenergic receptor blockade impairs extinction in fear conditioning paradigms in rodents. However, studies of the role of α1-adrenergic receptors in extinction using other conditioning paradigms, such as those examining the conditioned effects of drug of abuse, have yielded inconsistent results. In this article, we reanalyze and extend previously reported findings of the effect of prazosin, an α1-adrenergic receptor antagonist, on the extinction of a cocaine-induced conditioned place preference in rats, using a median split of performance during the initial test for preference. This new reanalysis, which includes further extinction testing, indicated a paradoxical dose effect. A single post-test administration of a lower dose of prazosin, 0.3 mg/kg intraperitoneally, impaired extinction in rats that showed a below-median preference during initial testing, but had no effect on extinction in rats that showed an above-median preference during initial testing. In contrast, a single post-test administration of a higher dose of prazosin, 1.0 mg/kg intraperitoneally, enhanced extinction in rats that showed an above-median preference during initial testing, but had no effect on extinction in rats that showed a below-median preference during initial testing. Consistent with other studies of fear and drug conditioning, these results suggest the involvement of the α1-adrenergic receptor in the formation of extinction memories, but also indicate a potentially important differential effect on extinction on the basis of the dose of prazosin and the strength of the initial learning.

  5. Corona initiated from grounded objects under thunderstorm conditions and its influence on lightning attachment

    NASA Astrophysics Data System (ADS)

    Bazelyan, E. M.; Raizer, Yu P.; Aleksandrov, N. L.

    2008-05-01

    Lightning attachment to grounded structures due to the initiation of an upward connecting leader from them is considered taking into account the effect of corona space charge near the structures. It is shown that the corona space charge strongly affects the initiation and development of the connecting leader. Specific features of a non-stationary corona are analysed analytically and numerically for one-dimensional electrode geometries and for a grounded rod coronating in a slowly varying thundercloud electric field that can be enhanced by the charge of an approaching downward lightning leader. Initiation and development of an upward connecting leader or upward lightning from high ground objects are investigated. Prospects of using the effect of coronae to control downward lightning discharges are discussed.

  6. 49 CFR 236.502 - Automatic brake application, initiation by restrictive block conditions stopping distance in...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... restrictive block conditions stopping distance in advance. 236.502 Section 236.502 Transportation Other... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and... conditions stopping distance in advance. An automatic train-stop or train-control system shall operate...

  7. 49 CFR 236.502 - Automatic brake application, initiation by restrictive block conditions stopping distance in...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... restrictive block conditions stopping distance in advance. 236.502 Section 236.502 Transportation Other... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and... conditions stopping distance in advance. An automatic train-stop or train-control system shall operate...

  8. 49 CFR 236.502 - Automatic brake application, initiation by restrictive block conditions stopping distance in...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... restrictive block conditions stopping distance in advance. 236.502 Section 236.502 Transportation Other... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and... conditions stopping distance in advance. An automatic train-stop or train-control system shall operate...

  9. 49 CFR 236.502 - Automatic brake application, initiation by restrictive block conditions stopping distance in...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... restrictive block conditions stopping distance in advance. 236.502 Section 236.502 Transportation Other... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and... conditions stopping distance in advance. An automatic train-stop or train-control system shall operate...

  10. 49 CFR 236.502 - Automatic brake application, initiation by restrictive block conditions stopping distance in...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... restrictive block conditions stopping distance in advance. 236.502 Section 236.502 Transportation Other... OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and... conditions stopping distance in advance. An automatic train-stop or train-control system shall operate...

  11. The effect of coronae on leader initiation and development under thunderstorm conditions and in long air gaps

    NASA Astrophysics Data System (ADS)

    Aleksandrov, N. L.; Bazelyan, E. M.; Carpenter, R. B., Jr.; Drabkin, M. M.; Raizer, Yu P.

    2001-11-01

    The initiation and development of a leader is theoretically studied by considering an electrode which is embedded in a cloud of space charge injected by a corona discharge. The focus is on the initiation of upward lightning from a stationary grounded object in a thundercloud electric field. The main results are also applicable to the leader process in long laboratory air gaps at direct voltage. Simple physical models of non-stationary coronae developing in free space near a solitary stressed sphere and of a leader propagating in the space charge cloud of coronae are suggested. It is shown that the electric field redistribution due to the space charge released by the long corona discharge near the top of a high object hinders the initiation and development of an upward leader from the object in a thundercloud electric field. The conditions for the formation of corona streamers that are required to initiate a leader are derived. The criteria are obtained for a leader to be initiated and propagate in the space charge cloud. A hypothesis is proposed that the streamers are never initiated near the top of a high object under thunderstorm conditions if at ground level there is only a slowly-varying electric field of the thundercloud. The streamers may be induced by the fast-rising electric field of distant downward leaders or intracloud discharges.

  12. A Knoevenagel Initiated Annulation Reaction Using Room Temperature or Microwave Conditions

    ERIC Educational Resources Information Center

    Cook, A. Gilbert

    2007-01-01

    An experiment is presented that has the student execute a Knoevenagel initiated annulation reaction. The reaction can be carried out either through use of a microwave reactor or by allowing the mixture to stand at room temperature for two days. The student is then challenged to identify the reaction product through a guided prelab exercise of the…

  13. What Variables Condition Syntactic Transfer? A Look at the L3 Initial State

    ERIC Educational Resources Information Center

    Rothman, Jason; Cabrelli Amaro, Jennifer

    2010-01-01

    This study investigates transfer at the third-language (L3) initial state, testing between the following possibilities: (1) the first language (L1) transfer hypothesis (an L1 effect for all adult acquisition), (2) the second language (L2) transfer hypothesis, where the L2 blocks L1 transfer (often referred to in the recent literature as the "L2…

  14. SCIENTIFIC UNCERTAINTIES IN ATMOSPHERIC MERCURY MODELS III: BOUNDARY AND INITIAL CONDITIONS, MODEL GRID RESOLUTION, AND HG(II) REDUCTION MECHANISMS

    EPA Science Inventory

    In this study we investigate the CMAQ model response in terms of simulated mercury concentration and deposition to boundary/initial conditions (BC/IC), model grid resolution (12- versus 36-km), and two alternative Hg(II) reduction mechanisms. The model response to the change of g...

  15. Visible-light initiated oxidative cyclization of phenyl propiolates with sulfinic acids to coumarin derivatives under metal-free conditions.

    PubMed

    Yang, Wenchao; Yang, Shuai; Li, Pinhua; Wang, Lei

    2015-05-01

    A visible-light initiated oxidative cyclization of phenyl propiolates with sulfinic acids has been developed. The arylsulfonylation of alkynes was performed at room temperature under metal-free conditions to generate coumarin derivatives with wide functional group tolerance, good yields and high regioselectivity.

  16. Critical behavior for random initial conditions in the one-dimensional fixed-energy Manna sandpile model

    NASA Astrophysics Data System (ADS)

    Kwon, Sungchul; Kim, Jin Min

    2016-07-01

    A fixed-energy Manna sandpile model undergoes an absorbing phase transition at a critical ρc, where an order parameter ϕ (t ) decays as t-α in time t . As the prototype of the Manna class, the model has been extensively studied in one dimension. However, the previous estimates of ρc and some critical exponents are different, depending on the types of initial conditions; random, natural, and regular conditions. The estimates of ρc for the random and the regular conditions are the lower and the upper bound among currently known estimates, respectively. In this work, for the random conditions, ρc and α are measured by taking into account finite-size (FS) effects. At the previous estimate of ρc, simulation results show that the temporal decay of ϕ (t ) is strongly affected by the FS effects up to much larger system size (˜106 ). For the sizes for which ϕ (t ) is independent up to t =2 ×107 , we estimate ρc=0.8925 (1 ) and α =0.110 (5 ) , which clearly differ from the previous results for the random conditions, ρc=0.89199 (5 ) and α =0.141 (24 ) . Instead, the present ρc agrees with ρc=0.89255 (2 ) of the regular conditions. In addition, the present α is substantially distinguishable from the results of the other types of initial conditions, α =0.159 (3 ) and 0.146 (2 ) for the natural and the regular conditions, respectively, which supports the claim of the initial condition dependence of dynamical exponents in the Manna class.

  17. Adaptation and Diversification of an RNA Replication System under Initiation- or Termination-Impaired Translational Conditions.

    PubMed

    Mizuuchi, Ryo; Ichihashi, Norikazu; Yomo, Tetsuya

    2016-07-01

    Adaptation to various environments is a remarkable characteristic of life. Is this limited to extant complex living organisms, or is it also possible for a simpler self-replication system to adapt? In this study, we addressed this question by using a translation-coupled RNA replication system that comprised a reconstituted translation system and an RNA "genome" that encoded a replicase gene. We performed RNA replication reactions under four conditions, under which different components of translation were partly inhibited. We found that replication efficiency increased with the number of rounds of replication under all the tested conditions. The types of dominant mutations differed depending on the condition, thus indicating that this simple system adapted to different environments in different ways. This suggests that even a primitive self-replication system composed of a small number of genes on the early earth could have had the ability to adapt to various environments.

  18. Preparation of porous microcrystalline cellulose pellets by freeze-drying: effects of wetting liquid and initial freezing conditions.

    PubMed

    Balaxi, Maria; Nikolakakis, Ioannis; Malamataris, Stavros

    2010-04-01

    The effects of wetting liquid and initial freezing conditions on the pore volume and pore size distribution of freeze-dried microcrystalline cellulose (MCC) pellets were studied with mercury porosimetry. Freeze-drying was applied after extrusion/spheronization using two wetting liquids (water and water-isopropanol) and three initial freezing conditions (-30, 80, and -197 degrees C). Also, the effects of initial freezing were compared to those on pellets prepared with extraction of NaCl from Avicel(R)/NaCl pellets. Pellet porosity was found to increase with decreasing initial freezing temperature and the increase is greater for pellets made with water as wetting liquid. The mean pore diameter is greater for the extracted pellets, followed by nonextracted MCC pellets made with water and water-isopropanol. Also, the pore diameter is greater for freezing at -80 degrees C comparatively to that at -30 degrees C, while it is smaller for freezing at -197 degrees C. Narrower and more symmetrical pore size distributions were obtained with water-isopropanol at -197 degrees C. The higher porosity obtained with water alone and the smallest mean pore diameter and narrower distribution obtained with water-isopropanol may be due to the effects of H-bonding between isopropanol and water molecules on the nucleation and growth of ice crystals during the initial freezing. PMID:19894272

  19. 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.

  20. Importance of the initial conditions for star formation - III. Statistical properties of embedded protostellar clusters

    NASA Astrophysics Data System (ADS)

    Girichidis, Philipp; Federrath, Christoph; Allison, Richard; Banerjee, Robi; Klessen, Ralf S.

    2012-03-01

    We investigate the formation of protostellar clusters during the collapse of dense molecular cloud cores with a focus on the evolution of potential and kinetic energy, the degree of substructure and the early phase of mass segregation. Our study is based on a series of hydrodynamic simulations of dense cores, where we vary the initial density profile and the initial turbulent velocity. In the three-dimensional adaptive mesh refinement simulations, we follow the dynamical formation of filaments and protostars until a star formation efficiency of 20 per cent. Despite the different initial configurations, the global ensemble of all protostars in a setup shows a similar energy evolution and forms sub-virial clusters with an energy ratio Ekin/|Epot|˜ 0.2. Concentrating on the innermost central region, the clusters show a roughly virialized energy balance. However, the region of virial balance only covers the innermost ˜10-30 per cent of all the protostars. In all simulations with multiple protostars, the total kinetic energy of the protostars is higher than the kinetic energy of the gas cloud, although the protostars only contain 20 per cent of the total mass. The clusters vary significantly in size, mass and number of protostars, and show different degrees of substructure and mass segregation. Flat density profiles and compressive turbulent modes produce more subclusters than centrally concentrated profiles and solenoidal turbulence. We find that dynamical relaxation and hence dynamical mass segregation is very efficient in all cases from the very beginning of the nascent cluster, i.e. during a phase when protostars constantly form and accrete.

  1. The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts

    SciTech Connect

    Schmitz, H.; Tsiklauri, D.

    2013-06-15

    Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [D. Tsiklauri, Phys. Plasmas, 18, 052903 (2011)]. The numerical simulations were carried out using different density profiles and fast electron distribution functions. It is shown that electromagnetic L and R modes are excited by the transverse current, initially imposed on the system. In the course of the simulations, no further interaction of the electron beam with the background plasma could be observed.

  2. Mechanistic studies of two-dimensional covalent organic frameworks rapidly polymerized from initially homogenous conditions.

    PubMed

    Smith, Brian J; Dichtel, William R

    2014-06-18

    Covalent organic frameworks (COFs) are periodic two- and three-dimensional (2D and 3D) polymer networks with high surface areas, low densities, and designed structures. Despite intense interest in framework materials, the nucleation and growth processes of COFs, and even of more established metal-organic frameworks (MOFs), are poorly understood. The kinetics of COF growth under varied reaction conditions provides mechanistic insight needed to improve their crystallinity and rationally synthesize new materials. Such kinetic measurements are unprecedented and difficult to perform on typical heterogeneous COF reaction mixtures. Here we synthesize 2D boronate ester-linked COF-5 under conditions in which the monomers are fully soluble. These homogeneous growth conditions provide equal or better material quality compared to any previous report and enable the first rigorous studies of the early stages of COF growth. COF-5 forms within minutes, and the precipitation rate is readily quantified from optical turbidity measurements. COF-5 formation follows an Arrhenius temperature dependence between 60-90 °C with an activation energy of 22-27 kcal/mol. The measured rate law includes a second order in both boronic acid and catechol moieties, and inverse second order in MeOH concentration. A competitive monofunctional catechol slows COF-5 formation but does not redissolve already precipitated COF, indicating both dynamic covalent bond formation and irreversible precipitation. Finally, stoichiometric H2O provides a 4-fold increase in crystallite domain areas, representing the first rational link between reaction conditions and material quality. PMID:24892961

  3. Initial conditions or emergence; what determines dissolution patterns in heterogeneous porous rocks?

    NASA Astrophysics Data System (ADS)

    Szymczak, Piotr; Upadhyay, Virat; Ladd, Anthony

    2016-04-01

    Dissolution of fractured or porous rocks is often accompanied by the formation of highly localized flow paths. Dissolution, in general, does not proceed uniformly, as it is influenced both by the heterogeneities in the rock matrix and by the instabilities associated with the positive feedback loops between the flow, dispersion, and chemical reactions. As a result, distinct channels or "wormholes" develop within the rocks in which both the flow and dissolution focus. In this communication, we aim to investigate how these emerging flow paths are influenced by the initial local inhomogeneities of the porosity field. Our results indicate a surprising insensitivity of the evolving dissolution patterns and flow rates to the amplitude and correlation length characterizing the inhomogeneities. At long times wormhole competition overwhelms the initial variations in aperture distribution, resulting in a universal relation between the separation of the wormholes and their length. This hierarchy of scales even persists in the presence of relatively large inhomogeneities (vugs), which focus the flow at the beginning of the dissolution process, but - if the sample is large enough - with time tend to be overwhelmed by the spontaneous growth of instabilities. A natural consequence of wormhole competition is that the separation between growing wormholes corresponds roughly to their length, something that is borne out by field observations.

  4. Sensitivity of Single-Column Model Solutions to Convective Parameterizations and Initial Conditions.

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoqing; Moncrieff, Mitchell W.

    2001-06-01

    Two sets of single-column model (SCM) simulations are performed to determine whether the SCM solutions are more sensitive to model parameterization schemes than to initial perturbations in temperature and moisture profiles. The first set of simulations (S3) used the Zhang and McFarlane scheme for the deep convection and the Hack scheme for the shallow convection, while the second set (S2) used the Hack scheme for all types of convection. The same random perturbation used by Hack and Pedretti is applied in S2 and S3. The observed total (horizontal and vertical) advections of temperature and moisture during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment are used to force all simulations. A major difference in temperature and moisture biases occurs between the ensemble means of the two sets of simulations, and is much larger than the standard deviation of each set. Differences are also evident in cloud and radiative properties. This demonstrates that SCM solutions can be more sensitive to the model physics than to the initial perturbations. In other words, the deterministic aspects of SCM solutions dominate the nondeterministic aspects, which is important for their continued use in developing parameterization schemes of convection and clouds in large-scale models. This point is also supported by the SCM simulations using several available longer observational datasets over different regions.

  5. Measurement of Initial Conditions at Nozzle Exit of High Speed Jets

    NASA Technical Reports Server (NTRS)

    Panda, J.; Zaman, K. B. M. Q.; Seasholtz, R. G.

    2004-01-01

    The time averaged and unsteady density fields close to the nozzle exit (0.1 less than or = x/D less than or = 2, x: downstream distance, D: jet diameter) of unheated free jets at Mach numbers of 0.95, 1.4, and 1.8 were measured using a molecular Rayleigh scattering based technique. The initial thickness of shear layer and its linear growth rate were determined from time-averaged density survey and a modeling process, which utilized the Crocco-Busemann equation to relate density profiles to velocity profiles. The model also corrected for the smearing effect caused by a relatively long probe length in the measured density data. The calculated shear layer thickness was further verified from a limited hot-wire measurement. Density fluctuations spectra, measured using a two-Photomultiplier-tube technique, were used to determine evolution of turbulent fluctuations in various Strouhal frequency bands. For this purpose spectra were obtained from a large number of points inside the flow; and at every axial station spectral data from all radial positions were integrated. The radially-integrated fluctuation data show an exponential growth with downstream distance and an eventual saturation in all Strouhal frequency bands. The initial level of density fluctuations was calculated by extrapolation to nozzle exit.

  6. Entropy Growth in the Early Universe and Confirmation of Initial Big Bang Conditions

    NASA Astrophysics Data System (ADS)

    Beckwith, Andrew

    2009-09-01

    This paper shows how increased entropy values from an initially low big bang level can be measured experimentally by counting relic gravitons. Furthermore the physical mechanism of this entropy increase is explained via analogies with early-universe phase transitions. The role of Jack Ng's (2007, 2008a, 2008b) revised infinite quantum statistics in the physics of gravitational wave detection is acknowledged. Ng's infinite quantum statistics can be used to show that ΔS~ΔNgravitons is a startmg point to the increasing net universe cosmological entropy. Finally, in a nod to similarities AS ZPE analysis, it is important to note that the resulting ΔS~ΔNgravitons ≠ 1088, that in fact it is much lower, allowing for evaluating initial graviton production as an emergent field phenomena, which may be similar to how ZPE states can be used to extract energy from a vacuum if entropy is not maximized. The rapid increase in entropy so alluded to without near sudden increases to 1088 may be enough to allow successful modeling of relic graviton production for entropy in a manner similar to ZPE energy extraction from a vacuum state.

  7. INITIATORS AND TRIGGERING CONDITIONS FOR ADAPTIVE AUTOMATION IN ADVANCED SMALL MODULAR REACTORS

    SciTech Connect

    Katya L Le Blanc; Johanna h Oxstrand

    2014-04-01

    It is anticipated that Advanced Small Modular Reactors (AdvSMRs) will employ high degrees of automation. High levels of automation can enhance system performance, but often at the cost of reduced human performance. Automation can lead to human out-of the loop issues, unbalanced workload, complacency, and other problems if it is not designed properly. Researchers have proposed adaptive automation (defined as dynamic or flexible allocation of functions) as a way to get the benefits of higher levels of automation without the human performance costs. Adaptive automation has the potential to balance operator workload and enhance operator situation awareness by allocating functions to the operators in a way that is sensitive to overall workload and capabilities at the time of operation. However, there still a number of questions regarding how to effectively design adaptive automation to achieve that potential. One of those questions is related to how to initiate (or trigger) a shift in automation in order to provide maximal sensitivity to operator needs without introducing undesirable consequences (such as unpredictable mode changes). Several triggering mechanisms for shifts in adaptive automation have been proposed including: operator initiated, critical events, performance-based, physiological measurement, model-based, and hybrid methods. As part of a larger project to develop design guidance for human-automation collaboration in AdvSMRs, researchers at Idaho National Laboratory have investigated the effectiveness and applicability of each of these triggering mechanisms in the context of AdvSMR. Researchers reviewed the empirical literature on adaptive automation and assessed each triggering mechanism based on the human-system performance consequences of employing that mechanism. Researchers also assessed the practicality and feasibility of using the mechanism in the context of an AdvSMR control room. Results indicate that there are tradeoffs associated with each

  8. Infrared Extinction and the Initial Conditions For Star and Planet Formation

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.

    2003-01-01

    This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program are to: 1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds, 2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds, 3) prepare results, where appropriate, for publication.

  9. Influence of the initial state of carbon nanotubes on their colloidal stability under natural conditions.

    PubMed

    Schwyzer, Irène; Kaegi, Ralf; Sigg, Laura; Magrez, Arnaud; Nowack, Bernd

    2011-06-01

    The colloidal stability of dry and suspended carbon nanotubes (CNTs) in the presence of amphiphilic compounds (i.e. natural organic matter or surfactants) at environmentally realistic concentrations was investigated over several days. The suspensions were analyzed for CNT concentration (UV-vis spectroscopy), particle size (nanoparticle tracking analysis), and CNT length and dispersion quality (TEM). When added in dry form, around 1% of the added CNTs remained suspended. Pre-dispersion in organic solvent or anionic detergent stabilized up to 65% of the added CNTs after 20 days of mild shaking and 5 days of settling. The initial state of the CNTs (dry vs. suspended) and the medium composition hence are critical determinants for the partitioning of CNTs between sediment and the water column. TEM analysis revealed that single suspended CNTs were present in all suspensions and that shaking and settling resulted in a fractionation of the CNTs with shorter CNTs remaining predominantly in suspension. PMID:21435759

  10. One at a time: counting single-nanoparticle/electrode collisions for accurate particle sizing by overcoming the instability of gold nanoparticles under electrolytic conditions.

    PubMed

    Qiu, Danfeng; Wang, Song; Zheng, Yuanqin; Deng, Zhaoxiang

    2013-12-20

    In response to an increasing demand for understanding electrochemical processes on the nanometer scale, it now becomes possible to monitor electron transfer reactions at the single-nanoparticle level, namely particle collision electrochemistry. This technique has great potential in the development of research tools towards single-particle electrocatalysis and selective and multiplexed particle sizing. However, one existing problem that may discourage these applications is the relatively weak colloidal stability of nanoparticles in an electrolytic solution. Here we report on a facile but efficient way to achieve a good stability of gold nanoparticles in an acidic media so that 'zero-aggregation' collisions can be achieved at a carbon ultramicroelectrode. This allows us to obtain anodic dissolution currents from individual nanoparticles in a 'one particle at a time' manner, based on which accurate particle sizing with a resolution of 1-2 nm can be achieved. Our work strongly suggests that to maintain a well dispersed nanoparticle solution during a particle impact electrochemical experiment is critically important for accurate particle sizing, as well as other applications that require information to be extracted from individual nanoparticles (not their aggregates).

  11. Rock thermal conductivity at the cap rock and initial conditions in two-phase volcanic hydrothermal systems

    SciTech Connect

    Mario Cesar Suarez Arriaga

    1993-01-28

    Numerical experiments are performed to investigate the rock thermal conductivity influence in the formation of the thermodynamic initial conditions of two-phase systems located in volcanic rocks. These systems exhibit pressure and temperature profiles characterized by a sudden change or discontinuity in their vertical gradients. Vapor dominated, two-phase fluids are found at the upper reservoir's levels. Liquid is the dominated phase within the layers below some critical point. Numerical results presented in this paper, suggest that the vertical location of this point of discontinuity be controlled by the thermal conductivity existing between the limit of the reservoir and the caprock. Too high values could originate liquid dominated reservoirs. Small values would be at the origin of vapor dominated reservoirs. A characteristic middle value could be responsible for the formation of a counter flow mechanism originating the initial conditions observed at some locations of the Los Azufres, Mexico, geothermal field.

  12. Initial conditions implied by t exp 1/2 solidification of a sphere with capillarity and interfacial kinetics

    NASA Technical Reports Server (NTRS)

    Sekerka, R. F.; Voorhees, P. W.; Coriel, S. R.; Mcfadden, G. B.

    1988-01-01

    The paper explores the initial conditions implied by t exp 1/2 growth of a spherical crystal solidifying from a pure, undercooled melt, including the effects of both capillarity and interface kinetics, and relates the findings to initial conditions that would be expected on the basis of classical nucleation theory. For crystal sizes near the nucleation radius, the calculated temperature profiles show a cold region ahead of the advancing interface that is even more undercooled than the undercooled bath. This cold region acts as a local heat sink that compensates for the reduced growth speed that would otherwise result from capillarity and kinetics, leading to precisely the same t exp 1/2 growth law that would have been obtained had both capillarity and kinetics been neglected.

  13. Assessment on Integrity of BWR Internals Against Impact Load by Water Hammer Under Conditions of Reactivity Initiated Accidents

    SciTech Connect

    Azuma, Mie; Taniguchi, Atsushi; Hotta, Akitoshi; Ohta, Takeshi

    2005-03-15

    The integrity of the reactor pressure vessel (RPV) head and reactor internals was assessed by means of fluid and fluid-structural coupled analyses to evaluate the water hammer phenomenon arising from postulated high burnup fuel failure under reactivity initiated accident (RIA) conditions. The fluid viscosity effect on the water column burst as well as the complex three-dimensional flow paths caused by a core shroud and standpipes were considered in this study. It is shown that fluid viscosity becomes an influential factor to dissipate impacting kinetic energy. Integrity of the RPV head and the shroud head was ensured with a sufficient level of margin even under these excessively conservative RIA conditions.

  14. Osmotic conditioning and shading on the germination and on the initial growth of Myracrodruon urundeuva Allemão seedlings.

    PubMed

    Scalon, Silvana P Q; Mota, Leandro H S; Mussury, Rosilda M

    2013-01-01

    The present work aimed to evaluate the osmotic conditioning and shading on the germination and on the initial growth of aroeira seedlings. The seeds were pre-imbibed in solutions with different concentrations of PEG (polyethylene glycol) and KNO3 and incubated at 10°C and 20°C temperatures, during 0 (control), 12 and 24 hours. After these periods, the seeds were dried until they reached the initial levels of humidity. After that, they were put for germinating in BOD (Biochemical Oxygen Demand) chambers, at alternated 20-30°C. The control treatment and the pre-conditionings that presented the best results in BOD germination were selected, PEG (-1.0 MPa) + KNO3 (-1.0 MPa) and KNO3 (-1.0 MPa), with pre-imbibition for 12 h and incubated in BOD at 20°C. The seeds were sowed on trays and then they were transplanted, keeping under a net covered with 50% and 70% of shading and at sunlight. The osmotic conditioning did not change the seeds germination in BOD, but the highest aerial part size was observed in PEG -1.0 MPa + KNO3-1.0 MPa treatment. The shading levels at 50% and 70% and the osmotic conditioning with PEG -1.0 MPa + KNO3-1.0 MPa offered a higher emergence in a greenhouse condition; however, at sunlight the seeds presented a better index of quality on the 145th day. PMID:23828353

  15. MERGER RATES OF DOUBLE NEUTRON STARS AND STELLAR ORIGIN BLACK HOLES: THE IMPACT OF INITIAL CONDITIONS ON BINARY EVOLUTION PREDICTIONS

    SciTech Connect

    Mink, S. E. de; Belczynski, K. E-mail: kbelczyn@astrouw.edu.pl

    2015-11-20

    The initial mass function (IMF), binary fraction, and distributions of binary parameters (mass ratios, separations, and eccentricities) are indispensable inputs for simulations of stellar populations. It is often claimed that these are poorly constrained, significantly affecting evolutionary predictions. Recently, dedicated observing campaigns have provided new constraints on the initial conditions for massive stars. Findings include a larger close binary fraction and a stronger preference for very tight systems. We investigate the impact on the predicted merger rates of neutron stars and black holes. Despite the changes with previous assumptions, we only find an increase of less than a factor of 2 (insignificant compared with evolutionary uncertainties of typically a factor of 10–100). We further show that the uncertainties in the new initial binary properties do not significantly affect (within a factor of 2) our predictions of double compact object merger rates. An exception is the uncertainty in IMF (variations by a factor of 6 up and down). No significant changes in the distributions of final component masses, mass ratios, chirp masses, and delay times are found. We conclude that the predictions are, for practical purposes, robust against uncertainties in the initial conditions concerning binary parameters, with the exception of the IMF. This eliminates an important layer of the many uncertain assumptions affecting the predictions of merger detection rates with the gravitational wave detectors aLIGO/aVirgo.

  16. Merger Rates of Double Neutron Stars and Stellar Origin Black Holes: The Impact of Initial Conditions on Binary Evolution Predictions

    NASA Astrophysics Data System (ADS)

    de Mink, S. E.; Belczynski, K.

    2015-11-01

    The initial mass function (IMF), binary fraction, and distributions of binary parameters (mass ratios, separations, and eccentricities) are indispensable inputs for simulations of stellar populations. It is often claimed that these are poorly constrained, significantly affecting evolutionary predictions. Recently, dedicated observing campaigns have provided new constraints on the initial conditions for massive stars. Findings include a larger close binary fraction and a stronger preference for very tight systems. We investigate the impact on the predicted merger rates of neutron stars and black holes. Despite the changes with previous assumptions, we only find an increase of less than a factor of 2 (insignificant compared with evolutionary uncertainties of typically a factor of 10–100). We further show that the uncertainties in the new initial binary properties do not significantly affect (within a factor of 2) our predictions of double compact object merger rates. An exception is the uncertainty in IMF (variations by a factor of 6 up and down). No significant changes in the distributions of final component masses, mass ratios, chirp masses, and delay times are found. We conclude that the predictions are, for practical purposes, robust against uncertainties in the initial conditions concerning binary parameters, with the exception of the IMF. This eliminates an important layer of the many uncertain assumptions affecting the predictions of merger detection rates with the gravitational wave detectors aLIGO/aVirgo.

  17. Visible Light Initiated Hantzsch Synthesis of 2,5-Diaryl-Substituted Pyrroles at Ambient Conditions.

    PubMed

    Lei, Tao; Liu, Wen-Qiang; Li, Jian; Huang, Mao-Yong; Yang, Bing; Meng, Qing-Yuan; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

    2016-05-20

    Irradiation of a mixture of enamines and α-bromo ketones, with a catalytic amount of Ir(ppy)3 by visible light (λ = 450 nm), enables the production of various 2,5-diaryl-substituted pyrroles in good to excellent yields. The key intermediates in this reaction have been identified as alkyl radicals, generated from single-electron transfer from the photoexcited Ir(ppy)3* to α-bromo ketones, which subsequently react with a broad range of enamines to undergo the Hantzsch reaction rapidly at ambient conditions. PMID:27199225

  18. Infrared Extinction and the Initial Conditions for Star and Planet Formation

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.

    2004-01-01

    This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program are to: 1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds, 2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds, 3) prepare results, where appropriate, for publication. A description of how these goals were met are included.

  19. Infrared Extinction and the Initial Conditions for Star and Planet Formation

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.

    2002-01-01

    This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program are to: (1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds; (2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds; and (3) prepare results, where appropriate, for publication.

  20. Sloan Digital Sky Survey III photometric quasar clustering: probing the initial conditions of the Universe

    NASA Astrophysics Data System (ADS)

    Ho, Shirley; Agarwal, Nishant; Myers, Adam D.; Lyons, Richard; Disbrow, Ashley; Seo, Hee-Jong; Ross, Ashley; Hirata, Christopher; Padmanabhan, Nikhil; O'Connell, Ross; Huff, Eric; Schlegel, David; Slosar, Anže; Weinberg, David; Strauss, Michael; Ross, Nicholas P.; Schneider, Donald P.; Bahcall, Neta; Brinkmann, J.; Palanque-Delabrouille, Nathalie; Yèche, Christophe

    2015-05-01

    parameters. In this paper, if the bias and shot noise parameters are fixed to their known values (which we model by fixing them to their best-fit Gaussian values), we find that the error bar reduces to 1σ simeq 65. We expect this error bar to reduce further by at least another factor of five if the data is free of any observational systematics. We therefore emphasize that in order to make best use of large scale structure data we need an accurate modeling of known systematics, a method to mitigate unknown systematics, and additionally independent theoretical models or observations to probe the bias of dark matter halos.

  1. The effect of initial and dynamic liver conditions on RF ablation size: a study in perfused and non-perfused animal models

    NASA Astrophysics Data System (ADS)

    Belous, Anna; Podhajsky, Ronald J.

    2009-02-01

    Investigators reporting RF ablation (RFA) studies often use different initial and dynamic conditions, often in porcine or bovine liver models. This study examines the effects of initial temperature, prior freezing, and perfusion in these models. Understanding how these variables affect RFA size provides some basis for comparing data from different studies. We obtained porcine and bovine livers from a slaughterhouse and divided them into experimental groups each with discrete initial temperatures set in the range of 12 to 37°C. The livers were used either the day of harvest or frozen within 1-3 days prior to RFA treatment. A perfused liver model was developed to simulate human blood flow rates and allowed accurate control of the temperature and flow rate. Saline (0.9%) was substituted for blood. The non-perfused liver model group included bovine and porcine tissue; whereas the perfused liver model group included only porcine tissue. One experiment included porcine livers that were perfused at different flow rates and with different saline concentrations. Harvested tissue from this group was examined under a light microscope and the level of edema was assessed using image processing software. The results demonstrate no significant difference in RF lesion sizes between porcine and bovine livers. Freezing the tissue prior to treatment has no significant effect but the initial temperature does significantly affect the size of ablation. The ablation size in perfused liver is similar to in vivo results (earlier study) but is significantly smaller then non-perfused liver. Morphological analysis indicates that perfusion, freezing, and saline concentration cause significant tissue edema.

  2. Phytoplankton succession in an isolated upwelled Benguela water body in relation to different initial nutrient conditions

    NASA Astrophysics Data System (ADS)

    Wasmund, Norbert; Nausch, Günther; Hansen, Anja

    2014-11-01

    Freshly upwelled water is poor in phytoplankton biomass but rich in nutrients. With its ageing, phytoplankton biomass increases whereas the nutrients are consumed. The overall aim of our investigation was to check the succession in the phytoplankton composition as a consequence of changing nutrient conditions. The experiments were carried out in mesocosms filled with surface water in the northern Benguela region and installed on board of R/V "Maria S. Merian". In the freshly upwelled water, phytoplankton took up nitrogen at a higher rate than phosphorus if compared with the Redfield ratio. Therefore, nitrogen was exhausted already by day 6. Nitrogen limitation after day 6 was indicated by decreasing chlorophyll a (chla) concentrations, primary production rates and productivity indices and increasing C/N ratios in particulate matter. Despite nitrogen limitation, phosphorus addition stimulated further growth, mainly of diatoms, pointing to luxury uptake. Cyanobacteria did not develop and nitrogen fixation was zero even with phosphorus and iron addition. Diatoms stay the most important group in the freshly upwelled water, but autotrophic and heterotrophic dinoflagellates increase strongly in the matured upwelled water. Mesocosms excluded disturbances by advective water transports, which influence the study of succssions under field conditions.

  3. Conditioning film and initial biofilm formation on ceramics tiles in the marine environment.

    PubMed

    Siboni, Nachshon; Lidor, Michal; Kramarsky-Winter, Esti; Kushmaro, Ariel

    2007-09-01

    The formation of biofilm on surfaces in the marine environment is believed to be an important factor driving colonization and recruitment of some sessile invertebrate communities. The present study follows the process of biofilm buildup on unglazed ceramic tiles deployed into the marine environment in the northern Gulf of Eilat. PCR-DGGE of film eluted from the tile surface indicated the presence of bacteria as early as 2 h after deployment. The makeup of the biofilm bacterial community was dynamic. Bacterial presence was apparent microscopically 6 h after deployment, though a developed biofilm was not observed until 24 h following deployment. Total organic carbon (TOC) data suggest that a conditioning film was built within the first four hours following deployment. During this time period TOC reached the highest level possibly due to adhesion of organics (e.g., sugars, proteins and humic substances) from the water column. We suggest that the primary adhering bacteria, whilst still in the reversible stage of adhesion, utilize the conditioning film as food causing the decrease in TOC. Understanding the dynamics between these primary bacterial settlers is of importance, since they may play a role on the succession of invertebrate species settlement onto artificial surfaces.

  4. Predicting uncertainty in sediment transport and landscape evolution - the influence of initial surface conditions

    NASA Astrophysics Data System (ADS)

    Hancock, G. R.; Coulthard, T. J.; Lowry, J. B. C.

    2016-05-01

    Numerical landscape evolution models were initially developed to examine natural catchment hydrology and geomorphology and have become a common tool to examine geomorphic behaviour over a range of time and space scales. These models all use a digital elevation model (DEM) as a representation of the landscape surface and a significant issue is the quality and resolution of this surface. Here we focus on how subtle perturbations or roughness on the DEM surface can produce alternative model results. This study is carried out by randomly varying the elevations of the DEM surface and examining the effect on sediment transport rates and geomorphology for a proposed rehabilitation design for a post-mining landscape using multiple landscape realisations with increasing magnitudes of random changes. We show that an increasing magnitude of random surface variability does not appear to have any significant effect on sediment transport over millennial time scales. However, the random surface variability greatly changes the temporal pattern or delivery of sediment output. A significant finding is that all simulations at the end of the 10,000 year modelled period are geomorphologically similar and present a geomorphological equifinality. However, the individual patterns of erosion and deposition were different for repeat simulations with a different sequence of random perturbations. The alternative positions of random perturbations strongly influence local patterns of hillslope erosion and evolution together with the pattern and behaviour of deposition. The findings demonstrate the complex feedbacks that occur even within a simple modelled system.

  5. Constraining the initial conditions of the Universe using large scale structure

    SciTech Connect

    Agarwal, Nishant; Ho, Shirley; Shandera, Sarah E-mail: shirleyh@andrew.cmu.edu

    2014-02-01

    Primordial non-Gaussianity induces a scale-dependent bias in large scale structure (LSS) data, proportional to f{sub NL}/k{sup 2} for the exact local ansatz. Recent work has shown that models of inflation that predict a large squeezed limit bispectrum, such as multi-field models and single field inflation with a modified initial state, typically give rise to a generalized local ansatz, with the scale-dependent bias now proportional to A{sub NL}/k{sup α}. We use photometric measurements of the angular power spectrum of luminous red galaxies and quasars in the Sloan Digital Sky Survey Data Release Eight (SDSS DR8) with the above parameterization to constrain the amplitude A{sub NL} and scale-dependence α. We find that the marginalized upper limit on α is 2.0 at the 95% confidence level, consistent with the local ansatz. We also present Fisher forecasts for a survey of the same size as DR8 to assess the role of systematics in current photometric LSS data. Moreover, we present analytic results on the expected mass dependence of A{sub NL} for different inflationary models, which can be an important observable for future surveys, if primordial non-Gaussianity is non-zero.

  6. Methane hydrate destabilization sensitivity to physical complexity and initial conditions in a numerical model

    NASA Astrophysics Data System (ADS)

    Darnell, K.; Flemings, P. B.; Bryant, S. L.

    2013-12-01

    We modify an existing dynamic, multiphase fluid flow model after Liu and Flemings (2007) to form methane hydrate and subsequently melt the hydrate in a marine, sedimentary environment. We then investigate the timing and evolution of hydrate melting when we include varying degrees of thermodynamic and chemical complexity. Our findings indicate that the incorporation of the latent heat of hydrate melting coupled with fresh water release retards the melting process. If the latent heat is neglected, the time required for the warming signal propagation to melt the hydrate completely is shorter by as much as a factor of two. Our basic model considers a one dimensional sedimentary column where the sediment is initially water saturated and supplied with a constant gas flux from below the hydrate stability zone, with the assumption that solid/gas/liquid phases are in equilibrium at the local pressure, temperature and salinity. We consider transport of water, methane, and salt over a 30 kyr interval to generate a modern hydrate deposit and corresponding salinity profile. Then, an instantaneous temperature increase is applied at the seafloor and held constant. This work suggests an alternative timing on the Gulf Stream shift that has been deduced from anomalous hydrate deposits by Phrampus and Hornbach (2012). Furthermore, we are able to show that current warming and relict warming from several hundreds years may be simultaneously convoluted in any current hydrate destabilization.

  7. Experimental characterization of initial conditions and spatio-temporal evolution of a small Atwood number Rayleigh-Taylor mixing layer

    SciTech Connect

    Mueschke, N J; Andrews, M J; Schilling, O

    2006-03-24

    The initial multi-mode interfacial velocity and density perturbations present at the onset of a small Atwood number, incompressible, miscible, Rayleigh-Taylor instability-driven mixing layer have been quantified using a combination of experimental techniques. The streamwise interfacial and spanwise interfacial perturbations were measured using high-resolution thermocouples and planar laser-induced fluorescence (PLIF), respectively. The initial multi-mode streamwise velocity perturbations at the two-fluid density interface were measured using particle-image velocimetry (PIV). It was found that the measured initial conditions describe an initially anisotropic state, in which the perturbations in the streamwise and spanwise directions are independent of one another. The evolution of various fluctuating velocity and density statistics, together with velocity and density variance spectra, were measured using PIV and high-resolution thermocouple data. The evolution of the velocity and density statistics is used to investigate the early-time evolution and the onset of strongly-nonlinear, transitional dynamics within the mixing layer. The early-time evolution of the density and vertical velocity variance spectra indicate that velocity fluctuations are the dominant mechanism driving the instability development. The implications of the present experimental measurements on the initialization of Reynolds-averaged turbulent transport and mixing models and of direct and large-eddy simulations of Rayleigh-Taylor instability-induced turbulence are discussed.

  8. Experimental characterization of initial conditions and spatio-temporal evolution of a small Atwood number Rayleigh-Taylor mixing layer

    SciTech Connect

    Mueschke, N J; Andrews, M J; Schilling, O

    2005-09-26

    The initial multi-mode interfacial velocity and density perturbations present at the onset of a small Atwood number, incompressible, miscible, Rayleigh-Taylor instability-driven mixing layer have been quantified using a combination of experimental techniques. The streamwise interfacial and spanwise interfacial perturbations were measured using high-resolution thermocouples and planar laser-induced fluorescence (PLIF), respectively. The initial multi-mode streamwise velocity perturbations at the two-fluid density interface were measured using particle-image velocimetry (PIV). It was found that the measured initial conditions describe an initially anisotropic state, in which the perturbations in the streamwise and spanwise directions are independent of one another. The evolution of various fluctuating velocity and density statistics, together with velocity and density variance spectra, were measured using PIV and high-resolution thermocouple data. The evolution of the velocity and density statistics is used to investigate the early-time evolution and the onset of strongly-nonlinear, transitional dynamics within the mixing layer. The early-time evolution of the density and vertical velocity variance spectra indicate that velocity fluctuations are the dominant mechanism driving the instability development. The implications of the present experimental measurements on the initialization of Reynolds-averaged turbulent transport and mixing models and of direct and large-eddy simulations of Rayleigh-Taylor instability-induced turbulence are discussed.

  9. Sudden pore pressure rise and rapid landslide initiation induced under extreme rainfall conditions - a case study

    NASA Astrophysics Data System (ADS)

    Fukuoka, Hiroshi; Wang, Fawu; Wang, Gonghui

    2010-05-01

    Since July 19 to 26, 2009, western Japan had a severe rainstorms and caused floods and landslides. Most of the landslides are debris slide - debris flows. Most devastated case took place in Hofu city, Japan. On July 21, extremely intense rainstorm caused numerous debris flows and mud flows in the hillslopes Some of the debris flows destroyed residential houses and home for elderly people, and finally killed 14 residents. Debris flow distribution map was prepared soon based on airphoto interpretation. Japanese Meteorological Agency runs nation-wide ground-based rain gauge network as well as radar rain gauges, which provide hourly to 10 minutes precipitation distribution real-time with spatial resolution of about 5 km. Distribution of daily (cumulative) precipitation of July 21 shows (1) The cumulative precipitation from 6 am -- 12 am of the day was evaluated that their return period could be 200 - 600 years statistically. In 2009, another extraordinary rainfall, of which intensity was evaluated as less than 100 years more more, caused floods in another city claiming many residents lives on the way to evacuation area. Those frequent extraordinary extreme rainfall is not concluded as the consequence of global warming nor climate change, however, those frequency of extreme rainfall events affecting societies are obviously increasing in Japan, too. As for the Hofu city case, it was proved that debris flows took place in the high precipitation area and covered by covered by weathered granite sands and silts which is called "masa". This sands has been proved susceptible against landslides under extreme rainfall conditions. However, the transition from slide - debris flow process is not well revealed, except authors past experiment on the similar masa samples in June 1999 Hiroshima debris flow case. Authors have embedded pore pressure control system for the undrained ring shear apparatus. Strongly weathered sandy soils were sampled just on the smooth and flat granitic

  10. Assessment of Initial Test Conditions for Experiments to Assess Irradiation Assisted Stress Corrosion Cracking Mechanisms

    SciTech Connect

    Busby, Jeremy T; Gussev, Maxim N

    2011-04-01

    Irradiation-assisted stress corrosion cracking is a key materials degradation issue in today s nuclear power reactor fleet and affects critical structural components within the reactor core. The effects of increased exposure to irradiation, stress, and/or coolant can substantially increase susceptibility to stress-corrosion cracking of austenitic steels in high-temperature water environments. . Despite 30 years of experience, the underlying mechanisms of IASCC are unknown. Extended service conditions will increase the exposure to irradiation, stress, and corrosive environment for all core internal components. The objective of this effort within the Light Water Reactor Sustainability program is to evaluate the response and mechanisms of IASCC in austenitic stainless steels with single variable experiments. A series of high-value irradiated specimens has been acquired from the past international research programs, providing a valuable opportunity to examine the mechanisms of IASCC. This batch of irradiated specimens has been received and inventoried. In addition, visual examination and sample cleaning has been completed. Microhardness testing has been performed on these specimens. All samples show evidence of hardening, as expected, although the degree of hardening has saturated and no trend with dose is observed. Further, the change in hardening can be converted to changes in mechanical properties. The calculated yield stress is consistent with previous data from light water reactor conditions. In addition, some evidence of changes in deformation mode was identified via examination of the microhardness indents. This analysis may provide further insights into the deformation mode under larger scale tests. Finally, swelling analysis was performed using immersion density methods. Most alloys showed some evidence of swelling, consistent with the expected trends for this class of alloy. The Hf-doped alloy showed densification rather than swelling. This observation may be

  11. ENSO response to high-latitude volcanic eruptions: the role of the initial conditions

    NASA Astrophysics Data System (ADS)

    Pausata, Francesco S. R.; Caballero, Rodrigo; Battisti, David S.

    2016-04-01

    Large volcanic eruptions can have major impacts on global climate affecting both atmospheric and ocean circulation through changes in atmospheric chemical composition and optical properties. The residence time of volcanic aerosol from strong eruptions is around 2-3 years and attention has consequently focused on their short-term impacts, and in particular on tropical eruptions. The long-term, ocean-mediated response has been less studied and large uncertainties remain. Moreover, studies have largely focused on tropical eruptions; high-latitude eruptions have drawn less attention because their impacts have been thought to be merely hemispheric rather than global and no study has hitherto investigated the long-term effects of such eruptions. Here we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere could cause an El Niño-like anomaly in the equatorial Pacific during the first 8-9 months after the start of the eruption owing to a strong hemispheric cooling. The hemispherically asymmetric cooling shifts the Inter-Tropical Convergence Zone southwards, triggering a weakening of the trade winds over the western and central equatorial Pacific that leads to an El Niño-like anomaly. However, the El Niño-like anomaly strongly depends on the initial ENSO state: a 3-time larger response is shown when the climate system is going towards a La Niña compared to when is going towards an El Niño. Finally, the eruption also leads to a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in the first twenty-five years after the eruption, followed by a weakening lasting at least 35 years. The long-lived changes in the AMOC strength also alter the variability of El Niño-Southern Oscillation.

  12. Fluctuating initial conditions in heavy ion collisions from the Glauber approach

    SciTech Connect

    Broniowski, Wojciech; Bozek, Piotr; Rybczynski, Maciej

    2007-11-15

    In the framework of the Glauber approach applied to the initial stage of ultra-relativistic heavy-ion collisions we analyze the shape parameters of the early-formed system (fireball) and their event-by-event fluctuations. We test a variety of models: the conventional wounded-nucleon model, a model admixing binary collisions to the wounded nucleons, a model with hot spots, and the hot-spot model where the deposition of energy occurs with a superimposed probability distribution. We look in detail at the so-called participant harmonic moments, {epsilon}*, obtained by an averaging procedure where in each event the system is translated to its center of mass and aligned with the major principal axis of the ellipse of inertia. Quantitative comparisons indicate substantial relative effects for {epsilon}* in variants of Glauber models. However, the dependence of the scaled standard deviation {delta}{epsilon}*/, {epsilon}* on the chosen model is weak. For all models the values range from about 0.5 for the central collisions to about 0.3-0.4 for peripheral collisions, for both gold-gold and copper-copper collisions. They are dominated by statistics and change only by 10-15% from model to model. We provide an approximate analytic expansion for the harmonic moments and their fluctuations given in terms of the fixed-axes moments. For central collisions and in the absence of correlations the expansion gives the simple formula {delta}{epsilon}*/{epsilon}*{approx_equal}{radical}(4/{pi}-1)=0.52. Similarly, we obtain expansions for the radial profiles of the higher harmonics. We investigate the relevance of the shape-fluctuation effects for jet quenching and find them important only for very central events. Finally, we make some comments of relevance for hydrodynamics, the elliptic flow, and its fluctuations. We argue how smooth hydrodynamics leads to the known result v{sub 4}{approx}v{sub 2}{sup 2} and, further, to the prediction {delta}v{sub 4}/v{sub 4}=2{delta}v{sub 2}/v{sub 2}.

  13. Solution of the quantum initial value problem with transparent boundary conditions

    NASA Astrophysics Data System (ADS)

    Puga, A.; Miller, B. N.

    2013-01-01

    Many systems of interest at the forefront of technological development, for example, in quantum computation, consist of weakly interacting elements that obey quantum mechanics. A challenge for modern theoretical physics is to develop a systematic methodology for approaching these "open" quantum systems. In particular, applied mathematicians have formulated the method of transparent boundary conditions (TBCs) to model interacting quantum systems of infinite extent. Here, we consider a particular application of TBCs to the escape of a particle from a one-dimensional infinite well when one of the bounding barriers is extinguished. We analytically obtain the exact time-dependent wave function by a Green's function method and then show that a numerical solution based on the TBC method is in excellent agreement. This work was motivated by an experiment carried out at the University of Texas on escape from a gravitational wedge billiard. Physicists have used billiards to understand and explore both classical and quantum chaos. Although the original experiment was carried out in the classical regime, current work is probing lower temperatures, where a quantum mechanical formulation is required.

  14. The Impact of Sea-Surface Winds on Meteorological Conditions in Israel: An Initial Study

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Saaroni, H.; Atlas, R.; Ardizzone, J.; Ben-Dor, E.; Druyan, L.; Jusem, C. J.; Karnieli, A.; Terry, J.

    2000-01-01

    The SSM/I (Spectral Sensor Microwave Imager) dataset is used to monitor surface wind speed and direction at four locations over the Eastern Mediterranean during December 1998 - January 1999. Time series of these data are compared to concurrent series of precipitation, surface temperature, humidity and winds at selected Israeli stations: Sde Dov (coastal), Bet Dagan (5 km. inland), Jerusalem (Judean Hills), Hafetz Haim (3 km. inland) and Sde Boker (central Negev). December 1998 and the beginning of January 1999 were dry in Israel, but significant precipitation was recorded at many stations during the second half of January (1999). SSM/I data show a surge in westerly surface winds west of Israel (32 N, 32.5 E) on 15 January, coinciding with the renewal of precipitation. We discuss the relevant circulation and pressure patterns during this transition in the context of the evolving meteorological conditions at the selected Israeli locations. The SSM/I dataset of near ocean surface winds, available for the last 12 years, is described. We analyze lagged correlation between these data and the Israeli station data and investigate possibility of predictive skill. Application of such relationships to short-term weather prediction would require real-time access to the SSM/I observations.

  15. Effect of Initial Condition on Subsonic Jet Noise from Two Rectangular Nozzles

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    2012-01-01

    Differences in jet noise data from two small 8:1 aspect ratio nozzles are investigated experimentally. The interiors of the two nozzles are identical but one has a thin-lip at the exit while the has a perpendicular face at the exit (thick-lip). It is found that the thin-lip nozzle is substantially noisier throughout the subsonic Mach number range. As much as 5dB difference in OASPL is noticed around Mj =0.96. Hot-wire measurements are carried out for the characteristics of the exit boundary layer and, overall, the noise difference can be ascribed to differences in the boundary layer state. The boundary layer of the quieter (thick-lip) nozzle goes through transition around M(sub j) =0.25 and at higher M(sub j) it remains "nominally turbulent". In comparison, the boundary layer of the thin-lip nozzle is found to remain "nominally laminar". at high subsonic conditions. The nominally laminar state involves significantly larger turbulence intensities commensurate with the higher radiated noise.

  16. Wheel-running mitigates psychomotor sensitization initiation but not post-sensitization conditioned activity and conditioned place preference induced by cocaine in mice.

    PubMed

    Geuzaine, Annabelle; Tirelli, Ezio

    2014-04-01

    Previous literature suggests that physical exercise allowed by an unlimited access to a running wheel for several weeks can mitigate chronic neurobehavioral responsiveness to several addictive drugs in rodents. Here, the potential preventive effects of unlimited wheel-running on the initiation of psychomotor sensitization and the acquisition and extinction of conditioned place preference (CPP) induced by 10 mg/kg cocaine in C56BL/6J mice were assessed in two independent experiments. To this end, half of the mice were singly housed with a running wheel at 28 days of age for 10 weeks prior to psychopharmacological tests, during which housing conditions did not change, and the other half of mice were housed without running wheel. In Experiment 1, prior to initiating sensitization, psychomotor activity on the two first drug-free once-daily sessions was not affected by wheel-running. This was also found for the acute psychomotor-activating effect of cocaine on the first sensitization session. Psychomotor sensitization readily developed over the 9 following once-daily sessions in mice housed without wheel, whereas it was inhibited in mice housed with a wheel. However, that difference did not transfer to post-sensitization conditioned activity. In contrast with the sensitization results, mice housed with a wheel still expressed a clear-cut CPP which did not extinguish differently from that of the other group, a result in disaccord with previous studies reporting either an attenuating or an increasing effect of wheel-running on cocaine-induced conditioned reward. The available results together indicate that interactions between wheel-running and cocaine effects are far from being satisfactorily characterized.

  17. Infrared Extinction and the Initial Conditions for Star and Planet Formation

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.

    2005-01-01

    This grant funded a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program were to: 1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds, 2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds, 3) use the results to measure and quantitatively describe the physical conditions of the dense gas and dust that produce stars and their accompanying planetary systems in molecular clouds. The goals of this project were met and exceeded as described below. 1) The infrared data for the project were obtained in a number of observing runs using the 3.5-meter NTT and 8-meter VLT telescopes of the European Southern Observatory in Chile and the 1.2-meter telescope of the Smithsonian Astrophysical Observatory in Arizona, the 1 0-meter Keck telescope in Hawaii, the 6.5-meter MMT of the Smithsonian Astrophysical Observatory in Arizona, and the NASA Hubble Space Telescope. The molecular-line data was obtained in three runs using the IRAM 30-meter telescope in Spain and one run with the ESO-15 meter millimeter-wave telescope in Chile. Millimeter-wave continuum measurements were obtained with the 15-meter JCMT in Hawaii. 2) Considerable effort was expended to reduce the infrared imaging observations including the development of custom software to produce high quality photometry and source astrometry. All the millimeter-line data was reduced using standard reduction routines. The highlights of the infrared analysis were the production of detailed extinction maps and the construction of profiles of the density structure of the B68, Coalsack, B335 and Lupus clouds. 3) The principal scientific accomplishments of this research program include the following: We were able to use our infrared observations to determine the

  18. Effect of initial conditions and of intra-event rainfall intensity variability on shallow landslide triggering return period

    NASA Astrophysics Data System (ADS)

    Peres, David Johnny; Cancelliere, Antonino

    2016-04-01

    Assessment of shallow landslide hazard is important for appropriate planning of mitigation measures. Generally, return period of slope instability is assumed as a quantitative metric to map landslide triggering hazard on a catchment. The most commonly applied approach to estimate such return period consists in coupling a physically-based landslide triggering model (hydrological and slope stability) with rainfall intensity-duration-frequency (IDF) curves. Among the drawbacks of such an approach, the following assumptions may be mentioned: (1) prefixed initial conditions, with no regard to their probability of occurrence, and (2) constant intensity-hyetographs. In our work we propose the use of a Monte Carlo simulation approach in order to investigate the effects of the two above mentioned assumptions. The approach is based on coupling a physically based hydrological and slope stability model with a stochastic rainfall time series generator. By this methodology a long series of synthetic rainfall data can be generated and given as input to a landslide triggering physically based model, in order to compute the return period of landslide triggering as the mean inter-arrival time of a factor of safety less than one. In particular, we couple the Neyman-Scott rectangular pulses model for hourly rainfall generation and the TRIGRS v.2 unsaturated model for the computation of transient response to individual rainfall events. Initial conditions are computed by a water table recession model that links initial conditions at a given event to the final response at the preceding event, thus taking into account variable inter-arrival time between storms. One-thousand years of synthetic hourly rainfall are generated to estimate return periods up to 100 years. Applications are first carried out to map landslide triggering hazard in the Loco catchment, located in highly landslide-prone area of the Peloritani Mountains, Sicily, Italy. Then a set of additional simulations are performed

  19. Modelling decisions to undergo genetic testing for susceptibility to common health conditions: an ancillary study of the Multiplex Initiative.

    PubMed

    Wade, Christopher H; Shiloh, Shoshana; Woolford, Samuel W; Roberts, J Scott; Alford, Sharon Hensley; Marteau, Theresa M; Biesecker, Barbara B

    2012-01-01

    New genetic tests reveal risks for multiple conditions simultaneously, although little is understood about the psychological factors that affect testing uptake. We assessed a conceptual model called the multiplex genetic testing model (MGTM) using structural equation modelling. The MGTM delineates worry, perceived severity, perceived risk, response efficacy and attitudes towards testing as predictors of intentions and behaviour. Participants were 270 healthy insured adults aged 25-40 from the Multiplex Initiative conducted within a health care system in Detroit, MI, USA. Participants were offered a genetic test that assessed risk for eight common health conditions. Confirmatory factor analysis revealed that worry, perceived risk and severity clustered into two disease domains: cancer or metabolic conditions. Only perceived severity of metabolic conditions was correlated with general response efficacy (β = 0.13, p<0.05), which predicted general attitudes towards testing (β = 0.24, p<0.01). Consistent with our hypothesised model, attitudes towards testing were the strongest predictors of intentions to undergo testing (β = 0.49, p<0.01), which in turn predicted testing uptake (OR 17.7, β = 0.97, p<0.01). The MGTM explained a striking 48% of the variance in intentions and 94% of the variation in uptake. These findings support use of the MGTM to explain psychological predictors of testing for multiple health conditions. PMID:21660870

  20. Dynamical analysis of R 1/□2 R cosmology: Impact of initial conditions and constraints from supernovae

    NASA Astrophysics Data System (ADS)

    Nersisyan, Henrik; Akrami, Yashar; Amendola, Luca; Koivisto, Tomi S.; Rubio, Javier

    2016-08-01

    We discuss the cosmological implications of the R □-2R nonlocal modification to standard gravity. We relax the assumption of special initial conditions in the local formulation of the theory, perform a full phase-space analysis of the system, and show that the late-time cosmology of the model exhibits two distinct evolution paths, on which a large range of values for the present equation of state can be reached. We then compare the general solutions to supernovae data and place constraints on the parameters of the model. In particular, we find that the mass parameter of the theory should be smaller than 1.2 in Hubble units.

  1. Solving modal equations of motion with initial conditions using MSC/NASTRAN DMAP. Part 1: Implementing exact mode superposition

    NASA Technical Reports Server (NTRS)

    Abdallah, Ayman A.; Barnett, Alan R.; Ibrahim, Omar M.; Manella, Richard T.

    1993-01-01

    Within the MSC/NASTRAN DMAP (Direct Matrix Abstraction Program) module TRD1, solving physical (coupled) or modal (uncoupled) transient equations of motion is performed using the Newmark-Beta or mode superposition algorithms, respectively. For equations of motion with initial conditions, only the Newmark-Beta integration routine has been available in MSC/NASTRAN solution sequences for solving physical systems and in custom DMAP sequences or alters for solving modal systems. In some cases, one difficulty with using the Newmark-Beta method is that the process of selecting suitable integration time steps for obtaining acceptable results is lengthy. In addition, when very small step sizes are required, a large amount of time can be spent integrating the equations of motion. For certain aerospace applications, a significant time savings can be realized when the equations of motion are solved using an exact integration routine instead of the Newmark-Beta numerical algorithm. In order to solve modal equations of motion with initial conditions and take advantage of efficiencies gained when using uncoupled solution algorithms (like that within TRD1), an exact mode superposition method using MSC/NASTRAN DMAP has been developed and successfully implemented as an enhancement to an existing coupled loads methodology at the NASA Lewis Research Center.

  2. CD8 T Cell-Initiated Vascular Endothelial Growth Factor Expression Promotes Central Nervous System Vascular Permeability under Neuroinflammatory Conditions

    PubMed Central

    Suidan, Georgette L.; Dickerson, Jonathan W.; Chen, Yi; McDole, Jeremiah R.; Tripathi, Pulak; Pirko, Istvan; Seroogy, Kim B.; Johnson, Aaron J.

    2010-01-01

    Dysregulation of the blood-brain barrier (BBB) is a hallmark feature of numerous neurologic disorders as diverse as multiple sclerosis, stroke, epilepsy, viral hemorrhagic fevers, cerebral malaria, and acute hemorrhagic leukoencephalitis. CD8 T cells are one immune cell type that have been implicated in promoting vascular permeability in these conditions. Our laboratory has created a murine model of CD8 T cell-mediated CNS vascular permeability using a variation of the Theiler’s murine encephalomyelitis virus system traditionally used to study multiple sclerosis. Previously, we demonstrated that CD8 T cells have the capacity to initiate astrocyte activation, cerebral endothelial cell tight junction protein alterations and CNS vascular permeability through a perforin-dependent process. To address the downstream mechanism by which CD8 T cells promote BBB dysregulation, in this study, we assess the role of vascular endothelial growth factor (VEGF) expression in this model. We demonstrate that neuronal expression of VEGF is significantly upregulated prior to, and coinciding with, CNS vascular permeability. Phosphorylation of fetal liver kinase-1 is significantly increased early in this process indicating activation of this receptor. Specific inhibition of neuropilin-1 significantly reduced CNS vascular permeability and fetal liver kinase-1 activation, and preserved levels of the cerebral endothelial cell tight junction protein occludin. Our data demonstrate that CD8 T cells initiate neuronal expression of VEGF in the CNS under neuroinflammatory conditions, and that VEGF may be a viable therapeutic target in neurologic disease characterized by inflammation-induced BBB disruption. PMID:20008293

  3. The Role of Model and Initial Condition Error in Numerical Weather Forecasting Investigated with an Observing System Simulation Experiment

    NASA Technical Reports Server (NTRS)

    Prive, Nikki C.; Errico, Ronald M.

    2013-01-01

    A series of experiments that explore the roles of model and initial condition error in numerical weather prediction are performed using an observing system simulation experiment (OSSE) framework developed at the National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO). The use of an OSSE allows the analysis and forecast errors to be explicitly calculated, and different hypothetical observing networks can be tested with ease. In these experiments, both a full global OSSE framework and an 'identical twin' OSSE setup are utilized to compare the behavior of the data assimilation system and evolution of forecast skill with and without model error. The initial condition error is manipulated by varying the distribution and quality of the observing network and the magnitude of observation errors. The results show that model error has a strong impact on both the quality of the analysis field and the evolution of forecast skill, including both systematic and unsystematic model error components. With a realistic observing network, the analysis state retains a significant quantity of error due to systematic model error. If errors of the analysis state are minimized, model error acts to rapidly degrade forecast skill during the first 24-48 hours of forward integration. In the presence of model error, the impact of observation errors on forecast skill is small, but in the absence of model error, observation errors cause a substantial degradation of the skill of medium range forecasts.

  4. Evaluation of reference genes for accurate normalization of gene expression for real time-quantitative PCR in Pyrus pyrifolia using different tissue samples and seasonal conditions.

    PubMed

    Imai, Tsuyoshi; Ubi, Benjamin E; Saito, Takanori; Moriguchi, Takaya

    2014-01-01

    We have evaluated suitable reference genes for real time (RT)-quantitative PCR (qPCR) analysis in Japanese pear (Pyrus pyrifolia). We tested most frequently used genes in the literature such as β-Tubulin, Histone H3, Actin, Elongation factor-1α, Glyceraldehyde-3-phosphate dehydrogenase, together with newly added genes Annexin, SAND and TIP41. A total of 17 primer combinations for these eight genes were evaluated using cDNAs synthesized from 16 tissue samples from four groups, namely: flower bud, flower organ, fruit flesh and fruit skin. Gene expression stabilities were analyzed using geNorm and NormFinder software packages or by ΔCt method. geNorm analysis indicated three best performing genes as being sufficient for reliable normalization of RT-qPCR data. Suitable reference genes were different among sample groups, suggesting the importance of validation of gene expression stability of reference genes in the samples of interest. Ranking of stability was basically similar between geNorm and NormFinder, suggesting usefulness of these programs based on different algorithms. ΔCt method suggested somewhat different results in some groups such as flower organ or fruit skin; though the overall results were in good correlation with geNorm or NormFinder. Gene expression of two cold-inducible genes PpCBF2 and PpCBF4 were quantified using the three most and the three least stable reference genes suggested by geNorm. Although normalized quantities were different between them, the relative quantities within a group of samples were similar even when the least stable reference genes were used. Our data suggested that using the geometric mean value of three reference genes for normalization is quite a reliable approach to evaluating gene expression by RT-qPCR. We propose that the initial evaluation of gene expression stability by ΔCt method, and subsequent evaluation by geNorm or NormFinder for limited number of superior gene candidates will be a practical way of finding out

  5. Transients from initial conditions based on Lagrangian perturbation theory in N-body simulations II: the effect of the transverse mode

    SciTech Connect

    Tatekawa, Takayuki

    2014-04-01

    We study the initial conditions for cosmological N-body simulations for precision cosmology. In general, Zel'dovich approximation has been applied for the initial conditions of N-body simulations for a long time. These initial conditions provide incorrect higher-order growth. These error caused by setting up the initial conditions by perturbation theory is called transients. We investigated the impact of transient on non-Gaussianity of density field by performing cosmological N-body simulations with initial conditions based on first-, second-, and third-order Lagrangian perturbation theory in previous paper. In this paper, we evaluates the effect of the transverse mode in the third-order Lagrangian perturbation theory for several statistical quantities such as power spectrum and non-Gaussianty. Then we clarified that the effect of the transverse mode in the third-order Lagrangian perturbation theory is quite small.

  6. Examining the influence of meteorological simulations forced by different initial and boundary conditions in volcanic ash dispersion modelling

    NASA Astrophysics Data System (ADS)

    Mulena, Gabriela C.; Allende, David G.; Puliafito, Salvador E.; Lakkis, Susan G.; Cremades, Pablo G.; Ulke, Ana G.

    2016-07-01

    The performance of the combination of the FALL3D ash dispersion model with the Weather Research and Forecast (WRF) meteorological model in the southern cone of South America under two initial and boundary conditions was evaluated. ERA-Interim and NCEP-GFS datasets were used as dynamic conditions by WRF to simulate meteorological fields for FALL3D. As a study case, we used the eruption of the Puyehue-Cordón Caulle Volcanic Complex occurred in Chile in June 2011. The simulated meteorological results were compared with the horizontal wind direction, meridional and zonal wind components, air and dew point temperatures of 7 radio sounding stations using a set of error indicators. In addition, the ash mass load simulated by FALL3D for a day of maximum dispersion of volcanic ash was evaluated using the Moderate Resolution Imaging Spectroradiometer (MODIS) data, on which the Prata algorithm was applied. As well as this, the WRF-dominant physical processes with both dynamic conditions were analyzed for that same date. Meteorological results indicated that the simulation performed with WRF and NCEP-GFS shows the lowest errors at levels between 925 and 300 hPa. Ash dispersion simulated with FALL3D and WRF in both dynamic conditions shows a different perfomance, which from the synoptic and dynamic viewpoint can be explained for the result of wind intensity and geopotential height. Moreover, WRF intiliazed with NCEP-GFS and FALL3D has a higher degree of concordance with the MODIS image. Based on the analysis and results, it was concluded that for the southern cone of South America, 1) it was not trivial for the simulation of volcanic ash dispersion to use one dynamic condition or another in WRF; 2) in that sense, meteorological variables that influenced the differences in volcanic ash dispersion were horizontal wind intensity and direction and geopotential heights; 3) the system generated from the combination of the WRF model initialized with NCEP-GFS and the FALL3D dispersion

  7. The Effect of Initial Conditions on the Nonlinear Evolution of Perturbed Interfaces Driven by Strong Blast Waves

    SciTech Connect

    Miles, Aaron R.

    2004-01-01

    In core-collapse supernovae, strong blast waves drive interfaces susceptible to Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities. In addition, perturbation growth can result from material expansion in large-scale velocity gradients behind the shock front. Laser-driven experiments are designed to produce a strongly shocked interface whose evolution is a scaled version of the unstable hydrogen-helium interface in core-collapse supernovae such as SN 1987A. The ultimate goal of this research is to develop an understanding of the effect of hydrodynamic instabilities and the resulting transition to turbulence on supernovae observables that remain as yet unexplained. In this dissertation, we present a computational study of unstable systems driven by high Mach number shock and blast waves. Using multi-physics radiation hydrodynamics codes and theoretical models, we consider the late nonlinear instability evolution of single mode, few mode, and multimode interfaces. We rely primarily on 2D calculations but present recent 3D results as well. For planar multimode systems, we show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions (IC's) by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Aspects of the IC's are shown to have a strong effect on the time to transition to the quasi-self-similar regime. With higher-dimensional blast waves, divergence restores the properties necessary for establishment of the self-similar state, but achieving it requires very high initial characteristic mode number and high Mach number for the incident blast wave. We point to recent stellar calculations that predict IC's we find incompatible with self-similarity, and emphasize the

  8. High throughput nanostructure-initiator mass spectrometry screening of microbial growth conditions for maximal β-glucosidase production

    PubMed Central

    Cheng, Xiaoliang; Hiras, Jennifer; Deng, Kai; Bowen, Benjamin; Simmons, Blake A.; Adams, Paul D.; Singer, Steven W.; Northen, Trent R.

    2013-01-01

    Production of biofuels via enzymatic hydrolysis of complex plant polysaccharides is a subject of intense global interest. Microbial communities are known to express a wide range of enzymes necessary for the saccharification of lignocellulosic feedstocks and serve as a powerful reservoir for enzyme discovery. However, the growth temperature and conditions that yield high cellulase activity vary widely, and the throughput to identify optimal conditions has been limited by the slow handling and conventional analysis. A rapid method that uses small volumes of isolate culture to resolve specific enzyme activity is needed. In this work, a high throughput nanostructure-initiator mass spectrometry (NIMS)-based approach was developed for screening a thermophilic cellulolytic actinomycete, Thermobispora bispora, for β-glucosidase production under various growth conditions. Media that produced high β-glucosidase activity were found to be I/S + glucose or microcrystalline cellulose (MCC), Medium 84 + rolled oats, and M9TE + MCC at 45°C. Supernatants of cell cultures grown in M9TE + 1% MCC cleaved 2.5 times more substrate at 45°C than at all other temperatures. While T. bispora is reported to grow optimally at 60°C in Medium 84 + rolled oats and M9TE + 1% MCC, approximately 40% more conversion was observed at 45°C. This high throughput NIMS approach may provide an important tool in discovery and characterization of enzymes from environmental microbes for industrial and biofuel applications. PMID:24367356

  9. Potential effect of matrix stiffness on the enrichment of tumor initiating cells under three-dimensional culture conditions.

    PubMed

    Liu, Chang; Liu, Yang; Xu, Xiao-xi; Wu, Hao; Xie, Hong-guo; Chen, Li; Lu, Ting; Yang, Li; Guo, Xin; Sun, Guang-wei; Wang, Wei; Ma, Xiao-jun; He, Xin

    2015-01-01

    Cancer stem cell (CSC) or tumor initiating cell (TIC) plays an important role in tumor progression and metastasis. Biophysical forces in tumor microenvironment have an important effect on tumor formation and development. In this study, the potential effect of matrix stiffness on the biological characteristics of human head and neck squamous cell carcinoma (HNSCC) TICs, especially the enrichment of HNSCC TICs, was investigated under three-dimensional (3D) culture conditions by means of alginate gel (ALG) beads with different matrix stiffnesses. ALG beads with soft (21 kPa), moderate (70 kPa) and hard (105 kPa) stiffness were generated by changing alginate concentration. It was found that significant HNSCC TIC enrichment was achieved in the ALG beads with moderate matrix stiffness (70 kPa). The gene expression of stemness markers Oct3/4 and Nanog, TIC markers CD44 and ABCG2 was enhanced in cells under this moderate (70 kPa) stiffness. HNSCC TIC proportion was also highly enriched under moderate matrix stiffness, accompanying with higher tumorigenicity, metastatic ability and drug resistance. And it was also found that the possible molecular mechanism underlying the regulated TIC properties by matrix stiffness under 3D culture conditions was significantly different from 2D culture condition. Therefore, the results achieved in this study indicated that 3D biophysical microenvironment had an important effect on TIC characteristics and alginate-based biomimetic scaffolds could be utilized as a proper platform to investigate the interaction between tumor cells and 3D microenvironment.

  10. Solving Modal Equations of Motion with Initial Conditions Using MSC/NASTRAN DMAP. Part 2; Coupled Versus Uncoupled Integration

    NASA Technical Reports Server (NTRS)

    Barnett, Alan R.; Ibrahim, Omar M.; Abdallah, Ayman A.; Sullivan, Timothy L.

    1993-01-01

    By utilizing MSC/NASTRAN DMAP (Direct Matrix Abstraction Program) in an existing NASA Lewis Research Center coupled loads methodology, solving modal equations of motion with initial conditions is possible using either coupled (Newmark-Beta) or uncoupled (exact mode superposition) integration available within module TRD1. Both the coupled and newly developed exact mode superposition methods have been used to perform transient analyses of various space systems. However, experience has shown that in most cases, significant time savings are realized when the equations of motion are integrated using the uncoupled solver instead of the coupled solver. Through the results of a real-world engineering analysis, advantages of using the exact mode superposition methodology are illustrated.

  11. Comparison of two- and three-dimensional simulations of miscible Richtmyer-Meshkov instability with multimode initial conditions

    NASA Astrophysics Data System (ADS)

    Olson, Britton J.; Greenough, Jeffrey A.

    2014-10-01

    A comparison between two- and three-dimensional large-eddy simulations of the planar Richtmyer-Meshkov instability with multimode initial conditions is made. The three-dimensional calculation achieves a turbulent state where an inertial range of length scales is present after the second shock wave impacts the interface. Grid independence of the mixing width up until the time of reshock is demonstrated through mesh refinement in both two and three dimensions. Quantitative measures of mixing are compared including the mixing width, mixedness, mixed mass, and spectra of velocity and density. A proposed approximate relation for the mixed mass is evaluated in one, two, and three dimensions and is proportional to the product of the mixing width and the mass fraction variance in the layer. The variance of the velocity field and the scalar mass fraction are compared in two and three dimensions and demonstrate large differences in behavior.

  12. Rayleigh-Taylor instability-induced mixing: initial conditions modeling, three-dimensional simulations and comparisons with experiment

    SciTech Connect

    Mueschke, N; Schilling, O; Andrews, M

    2007-01-09

    A spectral/compact finite-difference method with a third-order Adams-Bashforth-Moulton time-evolution scheme is used to perform a direct numerical simulation (DNS) of Rayleigh-Taylor flow. The initial conditions are modeled by parameterizing the multi-mode velocity and density perturbations measured just off of the splitter plate in water channel experiments. Parameters in the DNS are chosen to match the experiment as closely as possible. The early-time transition from a weakly-nonlinear to a strongly-nonlinear state, as well as the onset of turbulence, is examined by comparing the DNS and experimental results. The mixing layer width, molecular mixing parameter, vertical velocity variance, and density variance spectrum obtained from the DNS are shown to be in good agreement with the corresponding experimental values.

  13. Dynamics of the early universe and the initial conditions for inflation in a model with radiation and a Chaplygin gas

    NASA Astrophysics Data System (ADS)

    Monerat, G. A.; Oliveira-Neto, G.; Silva, E. V. Corrêa; Filho, L. G. Ferreira; Romildo, P., Jr.; Fabris, J. C.; Fracalossi, R.; Gonçalves, S. V. B.; Alvarenga, F. G.

    2007-07-01

    The early universe is modeled through the quantization of a Friedmann-Robertson-Walker (FRW) model with positive curvature. In this model, the universe is filled by two fluids: radiation and Chaplygin gas. The quantization of these models is made by following the Wheeler-DeWitt prescriptions. Using the Schutz formalism, the time notion is recovered and the Wheeler-DeWitt equation transforms into a time dependent Schrödinger equation, which rules the dynamics of the early universe, under the action of an effective potential Veff. Using a finite differences method and the Crank-Nicholson scheme, in a code implemented in the program OCTAVE, we solve the corresponding time dependent Schrödinger equation and obtain the time evolution of an initial wave packet. This wave packet satisfies appropriate boundary conditions. The calculation of the tunneling probabilities shows that the universe may emerge from the Planck era in an inflationary phase. It also shows that the tunneling probability is a function of the mean energy of the initial wave packet and of the two parameters of the Chaplygin gas. We also show a comparison between these results and those obtained by the WKB approximation.

  14. Seeding the Galactic Centre gas stream: gravitational instabilities set the initial conditions for the formation of protocluster clouds

    NASA Astrophysics Data System (ADS)

    Henshaw, J. D.; Longmore, S. N.; Kruijssen, J. M. D.

    2016-11-01

    Star formation within the Central Molecular Zone (CMZ) may be intimately linked to the orbital dynamics of the gas. Recent models suggest that star formation within the dust ridge molecular clouds (from G0.253+0.016 to Sgr B2) follows an evolutionary time sequence, triggered by tidal compression during their preceding pericentre passage. Given that these clouds are the most likely precursors to a generation of massive stars and extreme star clusters, this scenario would have profound implications for constraining the time-evolution of star formation. In this Letter, we search for the initial conditions of the protocluster clouds, focusing on the kinematics of gas situated upstream from pericentre. We observe a highly-regular corrugated velocity field in $\\{l,\\,v_{\\rm LSR}\\}$ space, with amplitude and wavelength $A=3.7\\,\\pm\\,0.1$ kms$^{-1}$ and $\\lambda_{\\rm vel, i}=22.5\\,\\pm\\,0.1$ pc, respectively. The extremes in velocity correlate with a series of massive ($\\sim10^{4}$M$_{\\odot}$) and compact ($R_{\\rm eq}\\sim2$ pc), quasi-regularly spaced ($\\sim8$ pc), molecular clouds. The corrugation wavelength and cloud separation closely agree with the predicted Toomre ($\\sim17$ pc) and Jeans ($\\sim6$ pc) lengths, respectively. We conclude that gravitational instabilities are driving the condensation of molecular clouds within the Galactic Centre gas stream. Furthermore, we speculate these seeds are the historical analogue of the dust-ridge molecular clouds, representing the initial conditions of star and cluster formation in the CMZ.

  15. Breakdown of coral colonial form under reduced pH conditions is initiated in polyps and mediated through apoptosis

    PubMed Central

    Kvitt, Hagit; Kramarsky-Winter, Esti; Maor-Landaw, Keren; Zandbank, Keren; Kushmaro, Ariel; Rosenfeld, Hanna; Fine, Maoz; Tchernov, Dan

    2015-01-01

    Certain stony corals can alternate between a calcifying colonial form and noncalcifying solitary polyps, supporting the hypothesis that corals have survived through geologic timescale periods of unfavorable calcification conditions. However, the mechanisms enabling this biological plasticity are yet to be identified. Here we show that incubation of two coral species (Pocillopora damicornis and Oculina patagonica) under reduced pH conditions (pH 7.2) simulating past ocean acidification induce tissue-specific apoptosis that leads to the dissociation of polyps from coenosarcs. This in turn leads to the breakdown of the coenosarc and, as a consequence, to loss of coloniality. Our data show that apoptosis is initiated in the polyps and that once dissociation between polyp and coenosarc terminates, apoptosis subsides. After reexposure of the resulting solitary polyps to normal pH (pH 8.2), both coral species regenerated coenosarc tissues and resumed calcification. These results indicate that regulation of coloniality is under the control of the polyp, the basic modular unit of the colony. A mechanistic explanation for several key evolutionarily important phenomena that occurred throughout coral evolution is proposed, including mechanisms that permitted species to survive the third tier of mass extinctions. PMID:25646434

  16. Effects of solution conditions on the steady-state kinetics of initiation of transcription by T7 RNA polymerase.

    PubMed

    Maslak, M; Martin, C T

    1994-06-01

    The T7 family of DNA-dependent RNA polymerases presents an ideal model system for the study of fundamental aspects of transcription. The small size of the promoter allows a variety of studies based on simple steady-state kinetics in the synthesis of a five-base runoff transcript. This assay can be used to characterize the effects on the initiation of transcription of simple modifications to potential protein or DNA specificity contacts. In the current work, in vitro conditions for this assay have been identified which optimize the apparent Km for the interaction between the enzyme and the promoter DNA. The addition to the reaction mixture of 0.05% Tween-20 and the substitution of 10 mM NaCl by 100 mM potassium glutamate not only improves the quality of the kinetic assays but also decreases Km by about an order of magnitude (strengthening the interaction between polymerase and its promoter). As observed for DNA binding in other systems, the parameter Km increases substantially with increasing [NaCl], but the salt dependence is shifted to higher concentrations as a function of [KGlu]. Thermal denaturation of the protein, monitored by circular dichroism spectroscopy, confirms the effects of salt and supports a model in which Cl- and other anions compete for phosphate binding sites on the protein. Finally, while Km is highly dependent on [NaCl], the measured kcat is relatively insensitive to salt. These data indicate that the parameters Km and kcat reflect changes respectively in promoter binding and in a rate-limiting step or steps leading to the initiation of transcription.

  17. Effect of austenitizing conditions on the impact properties of an alloyed austempered ductile iron of initially ferritic matrix structure

    NASA Astrophysics Data System (ADS)

    Delia, M.; Alaalam, M.; Grech, M.

    1998-04-01

    The effect of austenitizing conditions on the microstructure and impact properties of an austempered ductile iron (ADI) containing 1.6% Cu and 1.6% Ni as the main alloying elements was investigated. Impact tests were carried out on samples of initially ferritic matrix structure and which had been first austenitized at 850,900, 950, and 1000°C for 15 to 360 min and austempered at 360°C for 180 min. Results showed that the austenitizing temperature, Tγ, and time, tγ, have a significant effect on the impact properties of the alloy. This has been attributed to the influence of these variables on the carbon kinetics. The impact energy is generally high after short tγ, and it falls with further soaking. In samples austenitized at 850 and 900°C, these trends correspond to the gradual disappearance of the pro-eutectoid ferrite and the attainment of fully developed ausferritic structures. In initially ferritic structures, the carbon diffusion distances involved during austenitization are large compared to those in pearlitic structures. This explains the relatively long soaking periods required to attain fully ausferritic structures, which in spite of the lower impact energy values, have a better combination of mechanical properties. Microstructures of samples austenitized at 950 and 1000°C contain no pro-eutectoid ferrite. The impact properties of the former structures are independent of tγ, while those solution treated at 1000°C are generally low and show wide variation over the range of soaking time investigated. For fully ausferritic structures, impact properties fall with an increase in Tγ. This is particularly evident at 1000°C. As the Tγ increases, the amount of carbon dissolved in the original austenite increases. This slows down the rate of austenite transformation and results in coarser structures with lower mechanical properties. Optimum impact properties are obtained following austenitizing between 900 and 950°C for 120 to 180 min.

  18. Singular initial data and uniform global bounds for the hyper-viscous Navier-Stokes equation with periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Avrin, Joel

    In the hyper-viscous Navier-Stokes equations of incompressible flow, the operator A=- Δ is replaced by Aα, a, b≡ aAα+ bA for real numbers α, a, b with α⩾1 and b⩾0. We treat here the case a>0 and equip A (and hence Aα, a, b) with periodic boundary conditions over a rectangular solid Ω⊂R n. For initial data in L p(Ω) with α⩾ n/(2 p)+1/2 we establish local existence and uniqueness of strong solutions, generalizing a result of Giga/Miyakawa for α=1 and b=0. Specializing to the case p=2, which holds a particular physical relevance in terms of the total energy of the system, it is somewhat interesting to note that the condition α⩾ n/4+1/2 is sufficient also to establish global existence of these unique regular solutions and uniform higher-order bounds. For the borderline case α= n/4+1/2 we generalize standard existing (for n=3) "folklore" results and use energy techniques and Gronwall's inequality to obtain first a time-dependent Hα-bound, and then convert to a time-independent global exponential Hα-bound. This is to be expected, given that uniform bounds already exist for n=2, α=1 ([6, pp. 78-79]), and the folklore bounds already suggest that the α⩾ n/4+1/2 cases for n⩾3 should behave as well as the n=2 case. What is slightly less expected is that the n⩾3 cases are easier to prove and give better bounds, e.g. the uniform bound for n⩾3 depends on the square of the data in the exponential rather than the fourth power for n=2. More significantly, for α> n/4+1/2 we use our own entirely semigroup techniques to obtain uniform global bounds which bootstrap directly from the uniform L2-estimate and are algebraic in terms of the uniform L2-bounds on the initial and forcing data. The integer powers on the square of the data increase without bound as α↓ n/4+1/2, thus "anticipating" the exponential bound in the borderline case α= n/4+1/2. We prove our results for the case a=1 and b=0; the general case with a>0 and b⩾0 can be recovered by

  19. Impacts of alien invasive plants on soil nutrients are correlated with initial site conditions in NW Europe.

    PubMed

    Dassonville, Nicolas; Vanderhoeven, Sonia; Vanparys, Valérie; Hayez, Mathieu; Gruber, Wolf; Meerts, Pierre

    2008-08-01

    Alien invasive plants are capable of modifying ecosystem function. However, it is difficult to make generalisations because impacts often appear to be species- and site-specific. In this study, we examined the impacts of seven highly invasive plant species in NW Europe (Fallopia japonica, Heracleum mantegazzianum, Impatiens glandulifera, Prunus serotina, Rosa rugosa, Senecio inaequidens, Solidago gigantea) on nutrient pools in the topsoil and the standing biomass. We tested if the impacts follow predictable patterns, across species and sites or, alternatively, if they are entirely idiosyncratic. To that end, we compared invaded and adjacent uninvaded plots in a total of 36 sites with widely divergent soil chemistry and vegetation composition. For all species, invaded plots had increased aboveground biomass and nutrient stocks in standing biomass compared to uninvaded vegetation. This suggests that enhanced nutrient uptake may be a key trait of highly invasive plant species. The magnitude and direction of the impact on topsoil chemical properties were strongly site-specific. A striking finding is that the direction of change in soil properties followed a predictable pattern. Thus, strong positive impacts (higher topsoil nutrient concentrations in invaded plots compared to uninvaded ones) were most often found in sites with initially low nutrient concentrations in the topsoil, while negative impacts were generally found under the opposite conditions. This pattern was significant for potassium, magnesium, phosphorus, manganese and nitrogen. The particular site-specific pattern in the impacts that we observed provides the first evidence that alien invasive species may contribute to a homogenisation of soil conditions in invaded landscapes. PMID:18491146

  20. Sensitivity to initial conditions of a d -dimensional long-range-interacting quartic Fermi-Pasta-Ulam model: Universal scaling

    NASA Astrophysics Data System (ADS)

    Bagchi, Debarshee; Tsallis, Constantino

    2016-06-01

    We introduce a generalized d -dimensional Fermi-Pasta-Ulam model in the presence of long-range interactions, and perform a first-principle study of its chaos for d =1 ,2 ,3 through large-scale numerical simulations. The nonlinear interaction is assumed to decay algebraically as dij -α (α ≥0 ) , {di j} being the distances between N oscillator sites. Starting from random initial conditions we compute the maximal Lyapunov exponent λmax as a function of N . Our N ≫1 results strongly indicate that λmax remains constant and positive for α /d >1 (implying strong chaos, mixing, and ergodicity), and that it vanishes like N-κ for 0 ≤α /d <1 (thus approaching weak chaos and opening the possibility of breakdown of ergodicity). The suitably rescaled exponent κ exhibits universal scaling, namely that (d +2 )κ depends only on α /d and, when α /d increases from zero to unity, it monotonically decreases from unity to zero, remaining so for all α /d >1 . The value α /d =1 can therefore be seen as a critical point separating the ergodic regime from the anomalous one, κ playing a role analogous to that of an order parameter. This scaling law is consistent with Boltzmann-Gibbs statistics for α /d >1 , and possibly with q statistics for 0 ≤α /d <1 .

  1. Curli fimbriae are conditionally required in Escherichia coli O157:H7 for initial attachment and biofilm formation.

    PubMed

    Carter, Michelle Qiu; Louie, Jacqueline W; Feng, Doris; Zhong, Wayne; Brandl, Maria T

    2016-08-01

    Several species of enteric pathogens produce curli fimbriae, which may affect their interaction with surfaces and other microbes in nonhost environments. Here we used two Escherichia coli O157:H7 outbreak strains with distinct genotypes to understand the role of curli in surface attachment and biofilm formation in several systems relevant to fresh produce production and processing. Curli significantly enhanced the initial attachment of E. coli O157:H7 to spinach leaves and stainless steel surfaces by 5-fold. Curli was also required for E. coli O157:H7 biofilm formation on stainless steel and enhanced biofilm production on glass by 19-27 fold in LB no-salt broth. However, this contribution was not observed when cells were grown in sterile spinach lysates. Furthermore, both strains of E. coli O157:H7 produced minimal biofilms on polypropylene in LB no-salt broth but considerable amounts in spinach lysates. Under the latter conditions, curli appeared to slightly increase biofilm production. Importantly, curli played an essential role in the formation of mixed biofilm by E. coli O157:H7 and plant-associated microorganisms in spinach leaf washes, as revealed by confocal microscopy. Little or no E. coli O157:H7 biofilms were detected at 4 °C, supporting the importance of temperature control in postharvest and produce processing environments.

  2. An ensemble study of HyMeX IOP6 and IOP7a: sensitivity to physical and initial and boundary condition uncertainties

    NASA Astrophysics Data System (ADS)

    Hally, A.; Richard, E.; Ducrocq, V.

    2014-05-01

    The first Special Observation Period of the HyMeX campaign took place in the Mediterranean between September and November 2012 with the aim of better understanding the mechanisms which lead to heavy precipitation events (HPEs) in the region during the autumn months. Two such events, referred to as Intensive Observation Period 6 (IOP6) and Intensive Observation Period 7a (IOP7a), occurred respectively on 24 and 26 September over south-eastern France. IOP6 was characterised by moderate to weak low-level flow which led to heavy and concentrated convective rainfall over the plains near the coast, while IOP7a had strong low-level flow and consisted of a convective line over the mountainous regions further north and a band of stratiform rainfall further east. Firstly, an ensemble was constructed for each IOP using analyses from the AROME, AROME-WMED, ARPEGE and ECMWF operational models as initial (IC) and boundary (BC) conditions for the research model Meso-NH at a resolution of 2.5 km. A high level of model skill was seen for IOP7a, with a lower level of agreement with the observations for IOP6. Using the most accurate member of this ensemble as a CTRL simulation, three further ensembles were constructed in order to study uncertainties related to cloud physics and surface turbulence parameterisations. Perturbations were introduced by perturbing the time tendencies of the warm and cold microphysical and turbulence processes. An ensemble where all three sources of uncertainty were perturbed gave the greatest degree of dispersion in the surface rainfall for both IOPs. Comparing the level of dispersion to that of the ICBC ensemble demonstrated that when model skill is low (high) and low-level flow is weak to moderate (strong), the level of dispersion of the ICBC and physical perturbation ensembles is (is not) comparable. The level of sensitivity to these perturbations is thus concluded to be case dependent.

  3. An ensemble study of HyMeX IOP6 and IOP7a: sensitivity to physical and initial and boundary condition uncertainties

    NASA Astrophysics Data System (ADS)

    Hally, A.; Richard, E.; Ducrocq, V.

    2013-12-01

    The first Special Observation Period of the HyMeX campaign took place in the Mediterranean between September and November 2012 with the aim of better understanding the mechanisms which lead to heavy precipitation events (HPEs) in the region during the autumn months. Two such events, referred to as Intensive Observation Period 6 (IOP6) and Intensive Observation Period 7a (IOP7a), occurred respectively on 24 and 26 September over south-eastern France. IOP6 was characterised by moderate to weak low-level flow which led to heavy and concentrated convective rainfall over the plains near the coast, while IOP7a had strong low-level flow and consisted of a convective line over the mountainous regions further north and a band of stratiform rainfall further east. Firstly, an ensemble was constructed for each IOP using analyses from the AROME, AROME-WMED, ARPEGE and ECMWF operational models as initial (IC) and boundary (BC) conditions for the research model Meso-NH at a resolution of 2.5 km. A high level of model skill was seen for IOP7a, with a lower level of agreement with the observations for IOP6. Using the most accurate member of this ensemble as a CTRL simulation, three further ensembles were constructed in order to study uncertainties related to cloud physic and surface turbulence parameterisations. Perturbations were introduced by perturbing the time tendencies of the warm and cold microphysical and turbulence processes. An ensemble where all three sources of uncertainty were perturbed gave the greatest degree of dispersion in the surface rainfall for both IOPs. Comparing the level of dispersion to that of the ICBC ensemble demonstrated that when model skill is low (high) and low-level flow is weak to moderate (strong), the level of dispersion of the ICBC and physical perturbation ensembles is (is not) comparable. The level of sensitivity to these perturbations is thus concluded to be case dependent.

  4. An experimental seasonal hydrological forecasting system over the Yellow River basin - Part 1: Understanding the role of initial hydrological conditions

    NASA Astrophysics Data System (ADS)

    Yuan, Xing; Ma, Feng; Wang, Linying; Zheng, Ziyan; Ma, Zhuguo; Ye, Aizhong; Peng, Shaoming

    2016-06-01

    The hydrological cycle over the Yellow River has been altered by the climate change and human interventions greatly during past decades, with a decadal drying trend mixed with a large variation of seasonal hydrological extremes. To provide support for the adaptation to a changing environment, an experimental seasonal hydrological forecasting system is established over the Yellow River basin. The system draws from a legacy of a global hydrological forecasting system that is able to make use of real-time seasonal climate predictions from North American Multimodel Ensemble (NMME) climate models through a statistical downscaling approach but with a higher resolution and a spatially disaggregated calibration procedure that is based on a newly compiled hydrological observation dataset with 5 decades of naturalized streamflow at 12 mainstream gauges and a newly released meteorological observation dataset including 324 meteorological stations over the Yellow River basin. While the evaluation of the NMME-based seasonal hydrological forecasting will be presented in a companion paper to explore the added values from climate forecast models, this paper investigates the role of initial hydrological conditions (ICs) by carrying out 6-month Ensemble Streamflow Prediction (ESP) and reverse ESP-type simulations for each calendar month during 1982-2010 with the hydrological models in the forecasting system, i.e., a large-scale land surface hydrological model and a global routing model that is regionalized over the Yellow River. In terms of streamflow predictability, the ICs outweigh the meteorological forcings up to 2-5 months during the cold and dry seasons, but the latter prevails over the former in the predictability after the first month during the warm and wet seasons. For the streamflow forecasts initialized at the end of the rainy season, the influence of ICs for lower reaches of the Yellow River can be 5 months longer than that for the upper reaches, while such a difference

  5. Mean Flow Boundary Conditions for Computational Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Hixon, R.; Nallasamy, M.; Sawyer, S.; Dyson, R.

    2003-01-01

    In this work, a new type of boundary condition for time-accurate Computational Aeroacoustics solvers is described. This boundary condition is designed to complement the existing nonreflective boundary conditions while ensuring that the correct mean flow conditions are maintained throughout the flow calculation. Results are shown for a loaded 2D cascade, started with various initial conditions.

  6. A COSMIC-RAY-DOMINATED INTERSTELLAR MEDIUM IN ULTRA LUMINOUS INFRARED GALAXIES: NEW INITIAL CONDITIONS FOR STAR FORMATION

    SciTech Connect

    Papadopoulos, Padelis P.

    2010-09-01

    The high-density star formation typical of the merger/starburst events that power the large IR luminosities of ultraluminous infrared galaxies (ULIRGs) (L{sub IR}(8-1000 {mu}m) {approx}>10{sup 12} L{sub sun}) throughout the universe results in extraordinarily high cosmic-ray (CR) energy densities of U{sub CR} {approx} few x(10{sup 3}-10{sup 4}) U{sub CR,Gal} permeating their interstellar medium, a direct consequence of the large supernova remnant number densities in such systems. Unlike far-UV photons emanating from numerous star-forming (SF) sites, these large CR energy densities in ULIRGs will volumetrically heat and raise the ionization fraction of dense (n > 10{sup 4} cm{sup -3}) UV-shielded gas cores throughout their compact SF volumes. Such conditions can turn most of the large molecular gas masses found in such systems and their high redshift counterparts ({approx}10{sup 9}-10{sup 10} M {sub sun}) into giant CR-dominated regions (CRDRs) rather than ensembles of photon-dominated regions (PDRs) which dominate in less IR-luminous systems where star formation and molecular gas distributions are much more extended. The molecular gas in CRDRs will have a minimum temperature of T{sub kin} {approx} (80-160) K, and very high ionization fractions of x(e) > 10{sup -6} throughout its UV-shielded dense core, which in turn will fundamentally alter the initial conditions for star formation in such systems. Observational tests of CRDRs can be provided by high-J CO and {sup 13}CO lines or multi-J transitions of any heavy rotor molecules (e.g., HCN) and their isotopologs. Chemical signatures of very high ionization fractions in dense UV-shielded gas such as low [DCO{sup +}]/[HCO{sup +}] and high [HCO{sup +}]/[CO] abundance ratios would be good probes of CRDRs in extreme starbursts. These tests, along with direct measurements of the high CO line brightness temperatures expected over the areas of compact dense gas disks found in ULIRGs, will soon be feasible as sub

  7. Thrombin generation and fibrin clot formation under hypothermic conditions: an in vitro evaluation of tissue factor initiated whole blood coagulation

    PubMed Central

    Whelihan, Matthew F.; Kiankhooy, Armin; Brummel-Ziedins, Kathleen

    2015-01-01

    Background Despite trauma-induced hypothermic coagulopathy being familiar in the clinical setting, empirical experimentation concerning this phenomenon is lacking. In this study we investigated the effects of hypothermia on thrombin generation, clot formation and global hemostatic functions in an in vitro environment using a whole blood model and thromboelastography (TEG) which can recapitulate hypothermia. Methods Blood was collected from healthy individuals through venipuncture and treated with corn trypsin inhibitor, to block the contact pathway. Coagulation was initiated with 5pM tissue factor at temperatures 37°C, 32°C, and 27°C. Reactions were quenched over time with soluble and insoluble components of each time point analyzed for thrombin generation, fibrinogen consumption, factor (f)XIII activation and fibrin deposition. Global coagulation potential was evaluated through TEG. Results Data showed that thrombin generation in samples at 37°C and 32°C had comparable rates while 27°C had a much lower rate (39.2 ± 1.1 and 43 ± 2.4 nM/min vs 28.6 ± 4.4 nM/min, respectively). Fibrinogen consumption and fXIII activation were highest at 37°C followed by 32°C and 27°C (13.8 ± 2.9 percent/min vs 7.8 ± 1.8 percent/min, respectively). Fibrin formation as seen through clot weights also followed this trend. TEG data showed clot formation was fastest in samples at 37°C and lowest at 27°C. Maximum clot strength was similar for each temperature. Also, percent lysis of clots was highest at 37°C followed by 32°C and then 27°C. Conclusions Induced hypothermic conditions directly affect the rate of thrombin generation and clot formation while global clot stability remains intact. PMID:24331944

  8. Impact of initial and boundary conditions on regional winter climate over the Western Himalayas: A fixed domain size experiment

    NASA Astrophysics Data System (ADS)

    Maharana, P.; Dimri, A. P.

    2014-03-01

    The Western Himalayas during winter receives precipitation due to the eastward moving low pressure synoptic weather systems, called Western Disturbances (WDs) in Indian meteorological parlance. The complex Himalayan topography, sparse observational data, less understanding of physical processes, etc. form many interesting research questions over this region. One of the important research goals is to study the change in the winter (Dec., Jan. and Feb. - DJF) climate over the Himalayas. In the presented study with modelling efforts having varying initial and boundary conditions (ICBC) with same model physics option is attempted to provide a comment on important physical processes pertaining to precipitation and temperature fields. A 22 year (1980-2001) simulation with Regional Climate Model version 3 (RegCM3) forced with National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis 1 (NNRP1), NCEP/NCAR reanalysis 2 (NNRP2) and European Centre for Medium Range Weather Forecast 40 Year reanalysis (ERA40) as three different ICBC is carried out. The present study focuses on the winter climatology of the main meteorological parameters viz., temperature, precipitation and snow depth and interannual variability of winter seasonal precipitation. The model shows overestimation of seasonal average precipitation and underestimation of seasonal average temperature fields over the Western Himalayas in all the three model simulations. The interannual variability of precipitation and temperature over this region is nicely captured by the model. The model simulation with NNRP2 as the ICBC shows more realistic results. In addition the ensemble mean of the three simulations has shown improved results and is closer to the abovementioned simulation. Precipitation bias explained in terms of the higher vertical integrated moisture flux and transport shows strong convergence zone over and along the southern rim of the Indian Himalayas. The

  9. Random initial condition in small Barabasi-Albert networks and deviations from the scale-free behavior

    NASA Astrophysics Data System (ADS)

    Guimarães, Paulo R., Jr.; de Aguiar, Marcus A. M.; Bascompte, Jordi; Jordano, Pedro; Dos Reis, Sérgio Furtado

    2005-03-01

    Barabasi-Albert networks are constructed by adding nodes via preferential attachment to an initial core of nodes. We study the topology of small scale-free networks as a function of the size and average connectivity of their initial random core. We show that these two parameters may strongly affect the tail of the degree distribution, by consistently leading to broad-scale or single-scale networks. In particular, we argue that the size of the initial network core and its density of connections may be the main responsible for the exponential truncation of the power-law behavior observed in some small scale-free networks.

  10. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: A Novel Method for the Initial-Condition Estimation of a Tent Map

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Gao, Yong; Yang, Yuan

    2009-07-01

    Based on the connection between the tent map and the saw tooth map or Bernoulli map, a novel method for the initial-condition estimation of the tent map is presented. In the method, firstly the symbolic sequence generated from the tent map is converted to the forms obtained from the saw tooth map and Bernoulli map, and then the relationship between the symbolic sequence and the initial condition of the tent map can be obtained from the initial-condition estimation equations, which can be easily obtained, hence the estimation of the tent map can be achieved finally. The method is computationally simple and the error of the estimator is less than 1/2N. The method is verified by software simulation.

  11. Studies on flower initiation of Super-Dwarf wheat under stress conditions simulating those on the Space Station, Mir

    NASA Technical Reports Server (NTRS)

    Jiang, L.; Salisbury, F. B.; Campbell, W. F.; Carman, J. G.; Nan, R.

    1998-01-01

    Super-Dwarf wheat plants were grown in growth chambers under 12 treatments with three photoperiods (18 h, 21 h, 24 h) and four carbon dioxide (CO2) levels (360, 1,200, 3,000 and 7,000 micromoles mol-1). Carbon dioxide concentrations affected flower initiation rates of Super-Dwarf wheat. The optimum CO2 level for flower initiation and development was 1,200 micromoles mol-1. Super-optimum CO2 levels delayed flower initiation, but did not decrease final flower bud number per head. Longer photoperiods not only accelerated flower initiation rates, but also decreased deleterious effects of super-optimum CO2. Flower bud size and head length at the same developmental stage were larger under longer photoperiods, but final flower bud number was not affected by photoperiod.

  12. Real-time Monitoring of Surface-Initiated Atom Transfer Radical Polymerization Using Silicon Photonic Microring Resonators: Implications for Combinatorial Screening of Polymer Brush Growth Conditions

    PubMed Central

    Limpoco, F. Ted; Bailey, Ryan C.

    2011-01-01

    We directly monitor in parallel and in real-time the temporal profiles of polymer brushes simultaneously grown via multiple ATRP reaction conditions on a single substrate using arrays of silicon photonic microring resonators. In addition to probing relative polymerization rates, we also show the ability to evaluate the dynamic properties of the in situ grown polymers. Taken together, this presents a powerful new platform for studying modified interfaces that may allow for the combinatorial optimization of surface initiated polymerization conditions. PMID:21899288

  13. Comparisons of Stuttering Frequency during and after Speech Initiation in Unaltered Feedback, Altered Auditory Feedback and Choral Speech Conditions

    ERIC Educational Resources Information Center

    Saltuklaroglu, Tim; Kalinowski, Joseph; Robbins, Mary; Crawcour, Stephen; Bowers, Andrew

    2009-01-01

    Background: Stuttering is prone to strike during speech initiation more so than at any other point in an utterance. The use of auditory feedback (AAF) has been found to produce robust decreases in the stuttering frequency by creating an electronic rendition of choral speech (i.e., speaking in unison). However, AAF requires users to self-initiate…

  14. Accurate monotone cubic interpolation

    NASA Technical Reports Server (NTRS)

    Huynh, Hung T.

    1991-01-01

    Monotone piecewise cubic interpolants are simple and effective. They are generally third-order accurate, except near strict local extrema where accuracy degenerates to second-order due to the monotonicity constraint. Algorithms for piecewise cubic interpolants, which preserve monotonicity as well as uniform third and fourth-order accuracy are presented. The gain of accuracy is obtained by relaxing the monotonicity constraint in a geometric framework in which the median function plays a crucial role.

  15. Accurate Finite Difference Algorithms

    NASA Technical Reports Server (NTRS)

    Goodrich, John W.

    1996-01-01

    Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.

  16. The elasticity of hydrological forecast skill with respect to initial conditions and meteorological forcing for two major flood events in Germany

    NASA Astrophysics Data System (ADS)

    Thober, Stephan; Wood, Andy; Samaniego, Luis; Clark, Martyn; Kumar, Rohini; Zink, Matthias

    2014-05-01

    Major flood events are causing severe socio-economic damages. In Germany alone, the havoc wreaked by the 2002 and 2013 floods along the Elbe and Danube river amounted to more than 11 bn EUR. Highly skilled hydrological forecasts can help to mitigate such damages. Among several factors, these hydrological forecasts are strongly dependent on the initial conditions of the land surface at the beginning of the forecast period and the forecast skill of the meteorological forcing. Prior research has investigated how uncertainties of the initial conditions and meteorological forcing impact hydrological forecasts. In these studies, uncertainty is investigated by coupling an ensemble of basin initial conditions (e.g., snow, soil moisture) with an ensemble of meteorological forecasts (e.g., precipitation). However, most previous hydrological predictability studies focus on seasonal forecasts (e.g., forecasts of June-July-August flow volume, initialized on April 1st), and neglect the errors in meteorological forecasts at lead times from 1-14 days. In this study, an error growth model is proposed to investigate hydrological predictability at lead times of 1-14 days. This error growth model calculates a time-dependent weighted average between the perfect forecast and a stochastic perturbation of this. The time-dependent weights are derived from a logistic function. This error growth model thus attributes high weights to the perfect forecast for short lead times (e.g., less than five days) and low weights for longer lead times (e.g., more than five days). For longer lead times, more weight is given to the stochastic perturbation of the forecast and, hence, the ensemble spread is larger for these lead times resembling a higher uncertainty. Analogous to the error growth model, the initial conditions are calculated as a weighted average between the perfect condition and a historic condition of the land surface. The proposed framework is tested in Germany for the 2002 and 2013 flood

  17. The Roles of Radiative Forcing, Sea Surface Temperatures, and Atmospheric and Land Initial Conditions in U.S. Summer Warming Episodes

    NASA Astrophysics Data System (ADS)

    Jia, L.; Vecchi, G. A.; Yang, X.; Gudgel, R.; Delworth, T. L.; Stern, B.; Paffendorf, K.; Underwood, S.; Zeng, F. J.

    2015-12-01

    This study investigates the roles of radiative forcing, sea surface temperatures (SSTs), and atmospheric and land initial conditions in the summer warming episodes of the United States. The summer warming episodes are defined as the above normal (1983-2012) June-August 2-m temperature anomalies, and are referred to as heat waves in this study. Two contrasting cases, the summers of 2006 and 2012, are explored in detail to illustrate the distinct roles of SSTs, and atmospheric and land initial conditions in driving U.S. summer heat waves. For 2012, simulations with the GFDL atmospheric general circulation model reveal that SSTs play a critical role. Further sensitivity experiments reveal the contributions of global SST warming and SSTs in individual ocean basins to the geographic distribution and magnitudes of warm temperature anomalies. In contrast to 2012, for 2006, the atmospheric and land initial conditions are key drivers. The atmospheric (land) initial conditions play a key (minor) role in the central and northwestern (north and east) of U.S.. Due to changes in radiative forcing, the probability of areal averaged U.S. summer temperature anomalies exceeding the observed 2012 temperature anomaly increases with time over the early 21st century. La Nina (El Nino) events tend to increase (reduce) the occurrence of heat waves. The temperatures over the great central U.S. are mostly influenced by El Nino/La Nina. And, the central/western tropical Pacific plays a more important role than the eastern tropical Pacific. Thus, atmospheric and land initial conditions, SSTs and radiative forcing are all important drivers of, and sources of predictability for U.S. summer heat waves.

  18. Fear of falling is associated with prolonged anticipatory postural adjustment during gait initiation under dual-task conditions in older adults.

    PubMed

    Uemura, Kazuki; Yamada, Minoru; Nagai, Koutatsu; Tanaka, Buichi; Mori, Shuhei; Ichihashi, Noriaki

    2012-02-01

    Little is known about dynamic balance control under dual-task conditions in older adults with fear of falling (FoF). The purpose of this study was to examine the effect of FoF on anticipatory postural adjustment (APA) during gait initiation under dual-task conditions in older adults. Fifty-seven elderly volunteers (age, 79.2 [6.8] years) from the community participated in this study. Each participant was categorised into either the Fear (n=24) or No-fear (n=33) group on the basis of the presence or absence of FoF. Under single- and dual-task conditions, centre of pressure (COP) data were collected while the participants performed gait initiation trials from a starting position on a force platform. We also performed a 10-m walking test (WT), a timed up & go test (TUG), and a functional reach test (FR). The reaction and APA phases were measured from the COP data. The results showed that under the dual-task condition, the Fear group had significantly longer APA phases than the No-fear group, although no significant differences were observed between the 2 groups in the reaction and APA phases under the single-task condition and in any clinical measurements (WT, TUG, and FR). Our findings suggest that specific deficits in balance control occur in subjects with FoF during gait initiation while dual tasking, even if their physical functions are comparable to subjects without FoF.

  19. The growth of prognostic differences between GLAS model forecasts from SAT and NOSAT initial conditions. [for synoptic meteorology

    NASA Technical Reports Server (NTRS)

    Atlas, R.

    1982-01-01

    A study has been conducted to determine the cause of a major synoptic difference in the 72 h GLAS model forecasts from 0000 GMT 19 February 1976 that resulted from the inclusion of satellite data. The prognostic differences that resulted in diverging cyclone paths between the forecast that included satellite temperature soundings (SAT) and the forecast that excluded satellite sounding data (NOSAT) have been traced to initial state differences in the upper level wind and temperature patterns. These modifications enhanced the variation of thermal vorticity and thermal advection across the cyclone center and in the SAT case, gave a greater initial rate of movement of the upper-level vorticity maximum associated with the surface cyclone.

  20. PLI cancellation in ECG signal based on adaptive filter by using Wiener-Hopf equation for providing initial condition.

    PubMed

    Manosueb, Anchalee; Koseeyaporn, Jeerasuda; Wardkein, Paramote

    2014-01-01

    This paper presents a technique for finding the optimal initial weight for adaptive filter by using difference equation. The obtained analytical response of the system identifies the appropriate weights for the system and shows that the MSE depends on the initial weight. The proposed technique is applied to eliminate the known frequency power line interference (PLI) signal in the electrocardiogram (ECG) signal. The PLI signal is considered as a combination of cosine and sine signals. The adaptive filter, therefore, attempts to adjust the amplitude of cosine and sine signals to synthesize a reference signal very similar to the contaminated PLI signal. To compare the potential of the proposed technique to other techniques, the system is simulated by using the Matlab program and the TMS320C6713 digital board. The simulation results demonstrate that the proposed technique enables the system to eliminate the PLI signal with the fastest time and gains the superior results of the recovered ECG signal.

  1. Direct Numerical Simulation of a Temporally Evolving Incompressible Plane Wake: Effect of Initial Conditions on Evolution and Topology

    NASA Technical Reports Server (NTRS)

    Sondergaard, R.; Cantwell, B.; Mansour, N.

    1997-01-01

    Direct numerical simulations have been used to examine the effect of the initial disturbance field on the development of three-dimensionality and the transition to turbulence in the incompressible plane wake. The simulations were performed using a new numerical method for solving the time-dependent, three-dimensional, incompressible Navier-Stokes equations in flows with one infinite and two periodic directions. The method uses standard Fast Fourier Transforms and is applicable to cases where the vorticity field is compact in the infinite direction. Initial disturbances fields examined were combinations of two-dimensional waves and symmetric pairs of 60 deg oblique waves at the fundamental, subharmonic, and sub-subharmonic wavelengths. The results of these simulations indicate that the presence of 60 deg disturbances at the subharmonic streamwise wavelength results in the development of strong coherent three-dimensional structures. The resulting strong three-dimensional rate-of-strain triggers the growth of intense fine scale motions. Wakes initiated with 60 deg disturbances at the fundamental streamwise wavelength develop weak coherent streamwise structures, and do not develop significant fine scale motions, even at high Reynolds numbers. The wakes which develop strong three-dimensional structures exhibit growth rates on par with experimentally observed turbulent plane wakes. Wakes which develop only weak three-dimensional structures exhibit significantly lower late time growth rates. Preliminary studies of wakes initiated with an oblique fundamental and a two-dimensional subharmonic, which develop asymmetric coherent oblique structures at the subharmonic wavelength, indicate that significant fine scale motions only develop if the resulting oblique structures are above an angle of approximately 45 deg.

  2. Body condition and wind support initiate the shift of migratory direction and timing of nocturnal departure in a songbird.

    PubMed

    Schmaljohann, Heiko; Naef-Daenzer, Beat

    2011-11-01

    1. An innate migration strategy guides birds through space and time. Environmental variation further modulates individual behaviour within a genetically determined frame. In particular, ecological barriers could influence departure direction and its timing. A shift in the migratory direction in response to an ecological barrier could reveal how birds adjust their individual trajectories to environmental cues and body condition. 2. Northern wheatears of the Greenland/Iceland subspecies Oenanthe oenanthe leucorhoa arrive in Western Europe en route from their West African winter range. They then undergo an endogenously controlled shift in migratory direction from north to north-west to cross a large ecological barrier, the North Atlantic. We radiotracked these songbirds departing from Helgoland, a small island in the North Sea, over an unprecedented range of their journey. 3. Here, we show that both birds' body condition and the wind conditions that they encountered influenced the departure direction significantly. Jointly high fuel loads and favourable wind conditions enabled migrants to cross large stretches of sea. Birds in good condition departed early in the night heading to the sea towards their breeding areas, while birds with low fuel loads and/or flying in poor weather conditions departed in directions leading towards nearby mainland areas during the entire night. These areas could be reached even after setting off late at night. 4. Behavioural adjustment of migratory patterns is a critical adaptation for crossing ecological barriers. The observed variation in departure direction and time in relation to fuel load and wind revealed that these birds have an innate ability to respond by jointly incorporating internal information (body condition) and external information (wind support).

  3. Effects of random initial conditions on the dynamical scaling behaviors of a fixed-energy Manna sandpile model in one dimension.

    PubMed

    Kwon, Sungchul; Kim, Jin Min

    2015-01-01

    For a fixed-energy (FE) Manna sandpile model in one dimension, we investigate the effects of random initial conditions on the dynamical scaling behavior of an order parameter. In the FE Manna model, the density ρ of total particles is conserved, and an absorbing phase transition occurs at ρ(c) as ρ varies. In this work, we show that, for a given ρ, random initial distributions of particles lead to the domain structure in which domains with particle densities higher and lower than ρ(c) alternate with each other. In the domain structure, the dominant length scale is the average domain length, which increases via the coalescence of adjacent domains. At ρ(c), the domain structure slows down the decay of an order parameter and also causes anomalous finite-size effects, i.e., power-law decay followed by an exponential one before the quasisteady state. As a result, the interplay of particle conservation and random initial conditions causes the domain structure, which is the origin of the anomalous dynamical scaling behaviors for random initial conditions.

  4. Crack initiation testing of thimble tube material under PWR conditions to determine a stress threshold for IASCC

    NASA Astrophysics Data System (ADS)

    Bosch, R. W.; Vankeerberghen, M.; Gérard, R.; Somville, F.

    2015-06-01

    IASCC (Irradiation Assisted Stress Corrosion Cracking) crack initiation tests have been carried out on thimble tube material retrieved from a Belgian PWR. The crack initiation tests were carried out by constant load testing of thimble tube specimens at different stress levels. The time-to-failure was determined as a function of the applied stress to find a stress threshold under which no stress corrosion cracking will take place. The thimble tube was made of 316L cold-worked stainless steel and the dose profile along the thimble tube ranges from 45 to 80 dpa. This allows adding crack initiation data for dose values that have not been significantly reported, i.e. in the range of 45-55 dpa and at 80 dpa. The results can be used to determine whether the stress under which no IASCC occurs saturates for a dose larger than 30 dpa or whether a small further threshold decrease with dose can be observed. Over a period of four years, more than 40 specimens have been tested with doses ranging from 45 to 80 dpa at stress levels between 40% and 70% of the irradiated yield stress. Fracture occurred at all stress levels (but not all specimens) although the time-to-failure increased with decreasing stress. The results show that intergranular cracking was the main fracture mode in all failed O-rings. Three of six 80 dpa O-rings subjected to 40% and 45% of the yield stress did not fail after six months of testing. Based on these results and a comparison with literature data, an apparent stress limit for IASCC could be estimated at 40% of the irradiated yield stress.

  5. ON BOUNDARY AND INITIAL CONDITIONS IN \\mathscr{L}_p, p>1, OF SOLUTIONS OF PARABOLIC EQUATIONS

    NASA Astrophysics Data System (ADS)

    Petrushko, I. M.

    1986-02-01

    Necessary and sufficient conditions on the solutions of parabolic equations in a cylinder are established for the existence of limits in \\mathscr{L}_p on the lateral surface of the cylinder and in \\mathscr{L}_p with a weight on its lower base.Bibliography: 9 titles.

  6. Effect of Initial Conditions on 2D Rayleigh-Taylor Instability and Transition to Turbulence in Planar Blast-wave-driven Systems

    SciTech Connect

    Miles, A R; Edwards, M J; Greenough, J A

    2004-03-26

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, we present the first results from a computational study of such a system under drive conditions to be attainable on the National Ignition Facility. Using the multiphysics, AMR, higher order Godunov Eulerian hydrocode, Raptor, we consider the late nonlinear instability evolution for multiple amplitude and phase realizations of a variety of multimode spectral types. We show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions by allowing for memory of the initial conditions to be retained in the mix width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Certain aspects of the initial conditions, including the rms amplitude, are shown to have a strong effect on the time to transition to the quasi-self-similar regime.

  7. Effect of initial conditions on two-dimensional Rayleigh-Taylor instability and transition to turbulence in planar blast-wave-driven systems

    NASA Astrophysics Data System (ADS)

    Miles, A. R.; Edwards, M. J.; Greenough, J. A.

    2004-11-01

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, the results from a computational study of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] are presented. Using the multiphysics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J. A. Greenough, J. Comput. Phys. 184, 53 (2003)], the late nonlinear instability evolution for multiple amplitude and phase realizations of a variety of multimode spectral types is considered. Compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Certain aspects of the initial conditions, including the rms amplitude, are shown to have a strong effect on the time to transition to the quasi-self-similar regime.

  8. Cumulative Coulomb Stress Triggering as an Explanation for the Canterbury (New Zealand) Aftershock Sequence: Initial Conditions Are Everything?

    NASA Astrophysics Data System (ADS)

    Bebbington, Mark; Harte, David; Williams, Charles

    2016-01-01

    Using 2 years of aftershock data and three fault-plane solutions for each of the initial M7.1 Darfield earthquake and the larger (M >6) aftershocks, we conduct a detailed examination of Coulomb stress transfer in the Canterbury 2010-2011 earthquake sequence. Moment tensor solutions exist for 283 of the events with M ≥ 3.6, while 713 other events of M ≥ 3.6 have only hypocentre and magnitude information available. We look at various methods for deciding between the two possible mechanisms for the 283 events with moment tensor solutions, including conformation to observed surface faulting, and maximum ΔCFF transfer from the Darfield main shock. For the remaining events, imputation methods for the mechanism including nearest-neighbour, kernel smoothing, and optimal plane methods are considered. Fault length, width, and depth are arrived at via a suite of scaling relations. A large (50-70 %) proportion of the faults considered were calculated to have initial loading in excess of the final stress drop. The majority of faults that accumulated positive ΔCFF during the sequence were `encouraged' by the main shock failure, but, on the other hand, of the faults that failed during the sequence, more than 50 % of faults appeared to have accumulated a negative ΔCFF from all preceding failures during the sequence. These results were qualitatively insensitive to any of the factors considered. We conclude that there is much unknown about how Coulomb stress triggering works in practice.

  9. Magma Storage Conditions, Eruption Initiation and Magma Evolution Over Time: Investigating the Eruptions of Organ Caldera, Southern NM

    NASA Astrophysics Data System (ADS)

    Lente, J. L.; Johnson, E. R.

    2015-12-01

    The Organ caldera in southern New Mexico formed ~36 Ma from a series of three explosive, voluminous eruptions. The volcanic deposits are now exposed in the Organ Mountains and have a combined thickness of nearly 3 km and an estimated volume between 500 and1000 km3 (Seager & McCurry, 1988). This research uses analyses of quartz-hosted melt inclusions from the first- and last-erupted units to study the storage and differentiation of the magma body prior-to and during the initial eruption, as well as changes in the magma chamber over time as the eruptions progressed and ultimately ceased. Previous work suggests the Organ magma chamber was compositionally stratified (Seager, 1981) erupting top-down and tapping less-evolved magmas over time. However, preliminary results suggest a more complex system; possibly a convecting, homogenized magma chamber or a series of dykes and sills. Results obtained using FTIR analyses of H2O and CO2 in melt inclusions have shown variable volatile contents from the first erupted unit (~2.3 to 6.8 weight percent H2O, 0-118 ppm CO2). Using these values, saturation pressures of 45 to 266 MPa were calculated, indicating a minimum pressure at which the melt inclusion was trapped. These pressures suggest magma storage depths for the first erupted magmas of ~2 to 9 km (with most inclusions trapped between 4 and 8 km) which is inconsistent with the initial eruption coming from the top of a normally stratified chamber. The large variation in volatile contents and storage depths can have many explanations, such as degassing and shallow crystallization during ascent, or perhaps a more complex, elongate magma storage system. These possibilities, and whether or not magma mixing/rejuvenation triggered the initial eruption, will be explored with the acquisition of major and trace element compositions of melt inclusions. Additionally, analyses of melt inclusions from the last erupted ignimbrite, which erupted ~0.5 Ma after the first eruption, will enable

  10. Development of ultrafine-grained 1100 aluminum alloy by cryorolling with the optimized initial heat treatment conditions

    NASA Astrophysics Data System (ADS)

    Zakaria, Siti Aminah; Hussain, Zuhailawati; Seman, Anasyida Abu

    2016-07-01

    The aims of this study to determine the suitable initial heat treatment for 1100 aluminum alloy prior to cryorolling process and the properties of annealed and cryorolled annealed sample. The samples were annealed at different annealing temperature of 200˚C, 250˚C, 300˚C, 350˚C and 400˚C for 2 hours soaking time before cryorolling. The annealing samples then were cryorolled up to 50% thickness reduction after dipping in liquid nitrogen for 30 minutes. The effect of annealing temperature on cryorolled sample was investigated by employing hardness measurements and tensile test. The highest hardness and tensile properties achieved for sample annealed at 250 °C. The entire cryorolled sample showed severely deformed grain which are elongated along and following the rolling direction.

  11. Phasic excitation of ventral tegmental dopamine neurons potentiates the initiation of conditioned approach behavior: parametric and reinforcement-schedule analyses.

    PubMed

    Ilango, Anton; Kesner, Andrew J; Broker, Carl J; Wang, Dong V; Ikemoto, Satoshi

    2014-01-01

    Midbrain dopamine neurons are implicated in motivation and learning. However, it is unclear how phasic excitation of dopamine neurons, which is implicated in learning, is involved in motivation. Here we used a self-stimulation procedure to examine how mice seek for optogenetically-induced phasic excitation of dopamine neurons, with an emphasis on the temporal dimension. TH-Cre transgenic mice received adeno-associated viral vectors encoding channelrhodopsin-2 into the ventral tegmental area, resulting in selective expression of the opsin in dopamine neurons. These mice were trained to press on a lever for photo-pulse trains that phasically excited dopamine neurons. They learned to self-stimulate in a fast, constant manner, and rapidly reduced pressing during extinction. We first determined effective parameters of photo-pulse trains in self-stimulation. Lever-press rates changed as a function of the manipulation of pulse number, duration, intensity, and frequency. We then examined effects of interval and ratio schedules of reinforcement on photo-pulse train reinforcement, which was contrasted with food reinforcement. Reinforcement with food inhibited lever pressing for a few seconds, after which pressing was robustly regulated in a goal-directed manner. In contrast, phasic excitation of dopamine neurons robustly potentiated the initiation of lever pressing; however, this effect did not last more than 1 s and quickly diminished. Indeed, response rates markedly decreased when lever pressing was reinforced with inter-reinforcement interval schedules of 3 or 10 s or ratio schedules requiring multiple responses per reinforcement. Thus, phasic excitation of dopamine neurons briefly potentiates the initiation of approach behavior with apparent lack of long-term motivational regulation.

  12. Investigation of Rayleigh-Taylor turbulence and mixing using direct numerical simulation with experimentally-measured initial conditions. I. Comparison to experimental data

    SciTech Connect

    Mueschke, N; Schilling, O

    2008-07-23

    A 1152 x 760 x 1280 direct numerical simulation (DNS) using initial conditions, geometry, and physical parameters chosen to approximate those of a transitional, small Atwood number Rayleigh-Taylor mixing experiment [Mueschke, Andrews and Schilling, J. Fluid Mech. 567, 27 (2006)] is presented. The density and velocity fluctuations measured just off of the splitter plate in this buoyantly unstable water channel experiment were parameterized to provide physically-realistic, anisotropic initial conditions for the DNS. The methodology for parameterizing the measured data and numerically implementing the resulting perturbation spectra in the simulation is discussed in detail. The DNS model of the experiment is then validated by comparing quantities from the simulation to experimental measurements. In particular, large-scale quantities (such as the bubble front penetration hb and the mixing layer growth parameter {alpha}{sub b}), higher-order statistics (such as velocity variances and the molecular mixing parameter {theta}), and vertical velocity and density variance spectra from the DNS are shown to be in favorable agreement with the experimental data. Differences between the quantities obtained from the DNS and from experimental measurements are related to limitations in the dynamic range of scales resolved in the simulation and other idealizations of the simulation model. This work demonstrates that a parameterization of experimentally-measured initial conditions can yield simulation data that quantitatively agrees well with experimentally-measured low- and higher-order statistics in a Rayleigh-Taylor mixing layer. This study also provides resolution and initial conditions implementation requirements needed to simulate a physical Rayleigh-Taylor mixing experiment. In Part II [Mueschke and Schilling, Phys. Fluids (2008)], other quantities not measured in the experiment are obtained from the DNS and discussed, such as the integral- and Taylor-scale Reynolds numbers

  13. Accurate quantum chemical calculations

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

    1989-01-01

    An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.

  14. Determination of Marginal Conditions for Thermoacoustic Oscillations in a Looped Tube by Evolution of an Initial Disturbance Based on the Boundary-Layer Theory

    NASA Astrophysics Data System (ADS)

    Shimizu, Dai; Sugimoto, Nobumasa

    2014-03-01

    Marginal conditions are determined for the onset of thermoacoustic oscillations of a gas in a looped tube with a so-called stack sandwiched by hot and cold heat exchangers on the basis of the boundary-layer theory so far developed. Given a couple of impulses applied initially to a quiescent gas, the evolution of an infinitesimally small disturbance is studied by solving an initial-value problem to the linearized equations. Marginal states correspond to those in which the initial disturbance neither decays nor grows with time. In the case studied by Ueda and Kato [J. Acoust. Soc. Am. 124, 851 (2008)], the marginal conditions are obtained in two cases of the temperature distribution in the thermal buffer tube and compared with their results. To identify the marginal curves, the porosity of the stack or one of the subsidiary parameters such as the wall thickness of the stack is required in addition to the squared ratio of the hydraulic radius to the typical thickness of the thermal diffusion layer in a flow passage of gas. It is found that the marginal conditions are in qualitative agreement with the experimental results and that the right branch of the marginal curve is obtainable down to such a considerably low temperature ratio that the theory may become invalid.

  15. The polypyrimidine tract binding protein (PTB) requirement for internal initiation of translation of cardiovirus RNAs is conditional rather than absolute.

    PubMed Central

    Kaminski, A; Jackson, R J

    1998-01-01

    Picornavirus RNAs are translated by an unusual mechanism of internal ribosome entry that requires a substantial segment of the viral 5'-untranslated region, generally known as the internal ribosome entry segment (IRES), and in some circumstances may require cellular trans-acting proteins, particularly polypyrimidine tract binding protein (PTB). It is shown here that for encephalomyocarditis virus (EMCV), the PTB dependence of IRES function in vitro is determined partly by the nature of the reporter cistron, and more especially by the size of an A-rich bulge in the IRES. With a wild-type EMCV IRES (which has a bulge of 6 As), translation is effectively independent of PTB provided the IRES is driving the synthesis of EMCV viral polyprotein. With an enlarged (7A) bulge and heterologous reporters, translation is highly dependent on PTB. Intermediate levels of PTB dependence are seen with a 7A bulge IRES driving viral polyprotein synthesis or a wild-type (6A) bulge IRES linked to a heterologous reporter. None of these parameters influenced the binding of PTB to the high-affinity site in the IRES. These results argue that PTB is not an essential and universal internal initiation factor, but, rather, that when it is required, its binding to the IRES helps to maintain the appropriate higher-order structure and to reverse distortions caused, for example, by an enlarged A-rich bulge. PMID:9622122

  16. Pyrite Oxidation under initially neutral pH conditions and in the presence of Acidithiobacillus ferrooxidans and micromolar hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Lin, C.

    2012-01-01

    Hydrogen peroxide (H2O2) at a micromolar level played a role in the microbial surface oxidation of pyrite crystals under initially neutral pH. When the mineral-bacteria system was cyclically exposed to 50 μM H2O2, the colonization of Acidithiobacillus ferrooxidans onto the mineral surface was markedly enhanced, as compared to the control (no added H2O2). This can be attributed to the effects of H2O2 on increasing the roughness of the mineral surfaces, as well as the acidity and Fe2+ concentration at the mineral-solution interfaces. All of these effects tended to create more favourable nano- to micro-scale environments in the mineral surfaces for the cell adsorption. However, higher H2O2 levels inhibited the attachment of cells onto the mineral surfaces, possibly due to the oxidative stress in the bacteria when they approached the mineral surfaces where high levels of free radicals are present as a result of Fenton-like reactions. The more aggressive nature of H2O2 as an oxidant caused marked surface flaking of the mineral surface. The XPS results suggest that H2O2 accelerated the oxidation of pyrite-S and consequently facilitated the overall corrosion cycle of pyrite surfaces. This was accompanied by pH drop in the solution in contact with the pyrite cubes.

  17. ENSO response to high-latitude volcanic eruptions in the Northern Hemisphere: The role of the initial conditions

    NASA Astrophysics Data System (ADS)

    Pausata, Francesco S. R.; Karamperidou, Christina; Caballero, Rodrigo; Battisti, David S.

    2016-08-01

    A large ensemble of Earth System Model simulations is analyzed to show that high-latitude Northern Hemisphere eruptions give rise to El Niño-like anomalies in the winter following the eruption, the amplitude of which depends on the state of the tropical Pacific at the time of the eruption. The El Niño-like anomalies are almost three times larger when the eruption occurs during an incipient La Niña or during a neutral state compared to an incipient El Niño. The differential response results from stronger atmosphere-ocean coupling and extra-tropical feedbacks during an incipient La Niña compared to El Niño. Differences in the response continue through the second and third years following the eruption. When the eruption happens in a year of an incipient El Niño, a large cold (La Niña-like) anomaly develops in year 2; if the eruption occurs in a year of an incipient La Niña, no anomalies are simulated in year 2 and a La Niña-like response appears in year 3. After the El Niño-like anomaly in the first winter, the overall tendency of ENSO in the following 2 years is toward a La Niña state. Our results highlight the high sensitivity of tropical Pacific dynamics under volcanic forcing to the ENSO initial state and lay the groundwork for improved predictions of the global climatic response to high-latitude volcanic eruptions.

  18. Changes in bacterial community structure correlate with initial operating conditions of a field-scale denitrifying fluidized bed reactor.

    PubMed

    Hwang, C; Wu, W-M; Gentry, T J; Carley, J; Carroll, S L; Schadt, C; Watson, D; Jardine, P M; Zhou, J; Hickey, R F; Criddle, C S; Fields, M W

    2006-08-01

    High levels of nitrate are present in groundwater migrating from the former waste disposal ponds at the Y-12 National Security Complex in Oak Ridge, TN. A field-scale denitrifying fluidized bed reactor (FBR) was designed, constructed, and operated with ethanol as an electron donor for the removal of nitrate. After inoculation, biofilms developed on the granular activated carbon particles. Changes in the bacterial community of the FBR were evaluated with clone libraries (n = 500 partial sequences) of the small-subunit rRNA gene for samples taken over a 4-month start-up period. Early phases of start-up operation were characterized by a period of selection, followed by low diversity and predominance by Azoarcus-like sequences. Possible explanations were high pH and nutrient limitations. After amelioration of these conditions, diversification increased rapidly, with the appearance of Dechloromonas, Pseudomonas, and Hydrogenophaga sequences. Changes in NO3, SO4, and pH also likely contributed to shifts in community composition. The detection of sulfate-reducing-bacteria-like sequences closely related to Desulfovibrio and Desulfuromonas in the FBR have important implications for downstream applications at the field site.

  19. Changes in bacterial community structure correlate with initial operating conditions of a field-scale denitrifying fluidized bed reactor

    SciTech Connect

    Carley, Jack M; Carroll, Sue L; Schadt, Christopher Warren; Watson, David B; Jardine, Philip M; Zhou, Jizhong; Hickey, Robert; Criddle, Craig; Fields, Matthew Wayne

    2006-05-01

    High levels of nitrate are present in groundwater migrating from the former waste disposal ponds at the Y-12 National Security Complex in Oak Ridge, TN. A field-scale denitrifying fluidized bed reactor (FBR) was designed, constructed, and operated with ethanol as an electron donor for the removal of nitrate. After inoculation, biofilms developed on the granular activated carbon particles. Changes in the bacterial community of the FBR were evaluated with clone libraries (n=500 partial sequences) of the small-subunit rRNA gene for samples taken over a 4-month start-up period. Early phases of start-up operation were characterized by a period of selection, followed by low diversity and predominance by Azoarcus-like sequences. Possible explanations were high pH and nutrient limitations. After amelioration of these conditions, diversification increased rapidly, with the appearance of Dechloromonas, Pseudomonas, and Hydrogenophaga sequences. Changes in NO{sub 3}, SO{sub 4}, and pH also likely contributed to shifts in community composition. The detection of sulfate-reducing-bacteria-like sequences closely related to Desulfovibrio and Desulfuromonas in the FBR have important implications for downstream applications at the field site.

  20. Transition to Turbulence and Effect of Initial Conditions on 3D Compressible Mixing in Planar Blast-wave-driven Systems

    SciTech Connect

    Miles, A R; Edwards, M J; Greenough, J A

    2004-11-08

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams, 9(2), 209 (1991)] are presented. Using the multi-physics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J.A. Greenough, J. Comp. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pre-transition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernova are discussed.

  1. Incompressible limit of all-time solutions to 3-D full Navier-Stokes equations for perfect gas with well-prepared initial condition

    NASA Astrophysics Data System (ADS)

    Ren, Dandan; Ou, Yaobin

    2016-08-01

    In this paper, we prove the incompressible limit of all-time strong solutions to the three-dimensional full compressible Navier-Stokes equations. Here the velocity field and temperature satisfy the Dirichlet boundary condition and convective boundary condition, respectively. The uniform estimates in both the Mach number {ɛin(0,overline{ɛ}]} and time {tin[0,∞)} are established by deriving a differential inequality with decay property, where {overline{ɛ} in(0,1]} is a constant. Based on these uniform estimates, the global solution of full compressible Navier-Stokes equations with "well-prepared" initial conditions converges to the one of isentropic incompressible Navier-Stokes equations as the Mach number goes to zero.

  2. The Initial Conditions of Clustered Star Formation. III. The Deuterium Fractionation of the Ophiuchus B2 Core

    NASA Astrophysics Data System (ADS)

    Friesen, R. K.; Di Francesco, J.; Myers, P. C.; Belloche, A.; Shirley, Y. L.; Bourke, T. L.; André, P.

    2010-08-01

    We present N2D+ 3-2 (IRAM), and H2D+ 111-110 and N2H+ 4-3 (JCMT) maps of the small cluster-forming Ophiuchus B2 core in the nearby Ophiuchus molecular cloud. In conjunction with previously published N2H+ 1-0 observations, the N2D+ data reveal the deuterium fractionation in the high-density gas across Oph B2. The average deuterium fractionation RD = N(N2D+)/N(N2H+) ~ 0.03 over Oph B2, with several small scale RD peaks and a maximum RD = 0.1. The mean RD is consistent with previous results in isolated starless and protostellar cores. The column density distributions of both H2D+ and N2D+ show no correlation with total H2 column density. We find, however, an anticorrelation in deuterium fractionation with proximity to the embedded protostars in Oph B2 to distances gsim0.04 pc. Destruction mechanisms for deuterated molecules require gas temperatures greater than those previously determined through NH3 observations of Oph B2 to proceed. We present temperatures calculated for the dense core gas through the equating of non-thermal line widths for molecules (i.e., N2D+ and H2D+) expected to trace the same core regions, but the observed complex line structures in B2 preclude finding a reasonable result in many locations. This method may, however, work well in isolated cores with less complicated velocity structures. Finally, we use RD and the H2D+ column density across Oph B2 to set a lower limit on the ionization fraction across the core, finding a mean x e,lim >~ few × 10-8. Our results show that care must be taken when using deuterated species as a probe of the physical conditions of dense gas in star-forming regions.

  3. Non-Markovian reduced propagator, multiple-time correlation functions, and master equations with general initial conditions in the weak-coupling limit

    SciTech Connect

    Vega, Ines de; Alonso, Daniel

    2006-02-15

    In this paper we derive the evolution equation for the reduced propagator, an object that evolves vectors of the Hilbert space of a system S interacting with an environment B in a non-Markovian way. This evolution is conditioned to certain initial and final states of the environment. Once an average over these environmental states is made, reduced propagators permit the evaluation of multiple-time correlation functions of system observables. When this average is done stochastically the reduced propagator evolves according to a stochastic Schroedinger equation. In addition, it is possible to obtain the evolution equations of the multiple-time correlation functions which generalize the well-known quantum regression theorem to the non-Markovian case. Here, both methods, stochastic and evolution equations, are described by assuming a weak coupling between system and environment. Finally, we show that reduced propagators can be used to obtain a master equation with general initial conditions, and not necessarily an initial vacuum state for the environment. We illustrate the theory with several examples.

  4. Accurate Optical Reference Catalogs

    NASA Astrophysics Data System (ADS)

    Zacharias, N.

    2006-08-01

    Current and near future all-sky astrometric catalogs on the ICRF are reviewed with the emphasis on reference star data at optical wavelengths for user applications. The standard error of a Hipparcos Catalogue star position is now about 15 mas per coordinate. For the Tycho-2 data it is typically 20 to 100 mas, depending on magnitude. The USNO CCD Astrograph Catalog (UCAC) observing program was completed in 2004 and reductions toward the final UCAC3 release are in progress. This all-sky reference catalogue will have positional errors of 15 to 70 mas for stars in the 10 to 16 mag range, with a high degree of completeness. Proper motions for the about 60 million UCAC stars will be derived by combining UCAC astrometry with available early epoch data, including yet unpublished scans of the complete set of AGK2, Hamburg Zone astrograph and USNO Black Birch programs. Accurate positional and proper motion data are combined in the Naval Observatory Merged Astrometric Dataset (NOMAD) which includes Hipparcos, Tycho-2, UCAC2, USNO-B1, NPM+SPM plate scan data for astrometry, and is supplemented by multi-band optical photometry as well as 2MASS near infrared photometry. The Milli-Arcsecond Pathfinder Survey (MAPS) mission is currently being planned at USNO. This is a micro-satellite to obtain 1 mas positions, parallaxes, and 1 mas/yr proper motions for all bright stars down to about 15th magnitude. This program will be supplemented by a ground-based program to reach 18th magnitude on the 5 mas level.

  5. Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA

    SciTech Connect

    Merritt, E. C. Doss, F. W.; Loomis, E. N.; Flippo, K. A.; Kline, J. L.

    2015-06-15

    Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k-ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varying two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. We also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.

  6. Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA

    SciTech Connect

    Merritt, E. C.; Doss, F. W.; Loomis, E. N.; Flippo, K. A.; Kline, J. L.

    2015-06-24

    Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k-ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varying two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. In addition, we also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.

  7. Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA

    DOE PAGES

    Merritt, E. C.; Doss, F. W.; Loomis, E. N.; Flippo, K. A.; Kline, J. L.

    2015-06-24

    Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k-ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varyingmore » two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. In addition, we also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.« less

  8. Effects of Pressure on the Properties of Coal Char Under Gasification Conditions at High Initial Heating Rates

    NASA Astrophysics Data System (ADS)

    Shurtz, Randy Clark

    The effects of elevated pressure and high heating rates on coal pyrolysis and gasification were investigated. A high-pressure flat-flame burner (HPFFB) was designed and built to conduct these studies. The HPFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of ˜105 K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Pyrolysis experiments were conducted at particle heating rates of ˜10 5 K/s and maximum gas temperatures of ˜1700 K at pressures of 1 to 15 atm. A new coal swelling correlation was developed that predicts the effects of heating rate, pressure, and coal rank on the swelling ratio at heating rates above ˜104 K/s. A coal swelling rank index system based on 13C-NMR chemical structural parameters was devised. The empirical swelling model requires user inputs of the coal ultimate and proximate analyses and the use of a transient particle energy balance to predict the maximum particle heating rate. The swelling model was used to explain differences in previously reported bituminous coal swelling ratios that were measured in facilities with different heating rates. Char gasification studies by CO2 were conducted on a subbituminous coal and 4 bituminous coals in the HPFFB. Pressures of 5, 10, and 15 atmospheres were used with gas compositions of 20, 40, and 90 mole % CO2. Gas conditions with peak temperatures of 1700 K to 2000 K were used, which resulted in char particle temperatures of 1000 K to 1800 K. Three gasification models were developed to fit and analyze the gasification data. A simple 1 st--order model was used to show that the measured gasification rates were far below the film-diffusion limit. The other two models, designated CCK and CCKN, were based on three versions of the CBK models. CCKN used an nth--order kinetic mechanism and CCK used a semi-global Langmuir-Hinshelwood kinetic mechanism. The two CCK

  9. Coincidence detection in a neural correlate of classical conditioning is initiated by bidirectional 3-phosphoinositide-dependent kinase-1 signalling and modulated by adenosine receptors

    PubMed Central

    Keifer, Joyce; Zheng, Zhaoqing

    2015-01-01

    Key points Signalling mechanisms for coincidence detection of paired stimuli during classical conditioning are fundamental for understanding the mechanisms of associative learning. Bidirectional 3-phosphoinositide-dependent kinase-1 (PDK1) activity is signalled by TrkB neurotrophin receptors for paired stimuli and p75NTR for unpaired stimuli. Adenosine 2A receptors modulate PDK1 responses directly as G proteins and by transactivation of TrkB. Convergence of protein kinase A and PDK1 activity initiates signalling of paired stimuli during classical conditioning. Abstract How the neural substrates for detection of paired stimuli are distinct from unpaired stimuli is poorly understood and a fundamental question for understanding the signalling mechanisms for coincidence detection during associative learning. To address this question, we used a neural correlate of eyeblink classical conditioning in an isolated brainstem from the turtle, in which the cranial nerves are directly stimulated in place of using a tone or airpuff. A bidirectional response is activated in <5 min of training, in which phosphorylated 3-phosphoinositide-dependent kinase-1 (p-PDK1) is increased in response to paired and decreased in response to unpaired nerve stimulation and is mediated by the opposing actions of neurotrophin receptors TrkB and p75NTR. Surprisingly, blockade of adenosine 2A (A2A) receptors inhibits both of these responses. Pairing also induces substantially increased surface expression of TrkB that is inhibited by Src family tyrosine kinase and A2A receptor antagonists. Finally, the acquisition of conditioning is blocked by a PDK1 inhibitor. The unique action of A2A receptors to function directly as G proteins and in receptor transactivation to control distinct TrkB and p75NTR signalling pathways allows for convergent activation of PDK1 and protein kinase A during paired stimulation to initiate classical conditioning. PMID:25639253

  10. Continuum-scale investigation of evaporation from bare soil under different boundary and initial conditions: An evaluation of nonequilibrium phase change

    NASA Astrophysics Data System (ADS)

    Trautz, Andrew C.; Smits, Kathleen M.; Cihan, Abdullah

    2015-09-01

    Evaporation and condensation in bare soils govern water and energy fluxes between the land and atmosphere. Phase change between liquid water and water vapor is commonly evaluated in soil hydrology using an assumption of instantaneous phase change (i.e., chemical equilibrium). Past experimental studies have shown that finite volatilization and condensation times can be observed under certain environmental conditions, thereby questioning the validity of this assumption. A comparison between equilibrium and nonequilibrium phase change modeling approaches showed that the latter is able to provide better estimates of evaporation, justifying the need for more research on this topic. Several formulations based on irreversible thermodynamics, first-order reaction kinetics, or the kinetic theory of gases have been employed to describe nonequilibrium phase change at the continuum scale. In this study, results from a fully coupled nonisothermal heat and mass transfer model applying four different nonequilibrium phase change formulations were compared with experimental data generated under different initial and boundary conditions. Results from a modified Hertz-Knudsen formulation based on kinetic theory of gases, proposed herein, were consistently in best agreement in terms of preserving both magnitude and trends of experimental data under all environmental conditions analyzed. Simulation results showed that temperature-dependent formulations generally better predict evaporation than formulations independent of temperature. Analysis of vapor concentrations within the porous media showed that conditions were not at equilibrium under the experimental conditions tested.

  11. Quantum slow-roll and quantum fast-roll inflationary initial conditions: CMB quadrupole suppression and further effects on the low CMB multipoles

    SciTech Connect

    Cao, F. J.; Vega, H. J. de; Sanchez, N. G.

    2008-10-15

    Quantum fast-roll initial conditions for the inflaton which are different from the classical fast-roll conditions and from the quantum slow-roll conditions can lead to inflation that lasts long enough. These quantum fast-roll initial conditions for the inflaton allow for kinetic energies of the same order of the potential energies and nonperturbative inflaton modes with nonzero wave numbers. Their evolution starts with a transitory epoch where the redshift due to the expansion succeeds to assemble the quantum excited modes of the inflaton in a homogeneous (zero mode) condensate, and the large value of the Hubble parameter succeeds to overdamp the fast roll of the redshifted inflaton modes. After this transitory stage the effective classical slow-roll epoch is reached. Most of the e-folds are produced during the slow-roll epoch, and we recover the classical slow-roll results for the scalar and tensor metric perturbations plus corrections. These corrections are important if scales which are horizon size today exited the horizon by the end of the transitory stage and, as a consequence, the lower cosmic microwave background (CMB) multipoles get suppressed or enhanced. Both for scalar and tensor metric perturbations, fast roll leads to a suppression of the amplitude of the perturbations (and of the low CMB multipoles), while the quantum precondensate epoch gives an enhancement of the amplitude of the perturbations (and of the low CMB multipoles). These two types of corrections can compete and combine in a scale dependent manner. They turn out to be smaller in new inflation than in chaotic inflation. These corrections arise as natural consequences of the quantum nonperturbative inflaton dynamics, and can allow a further improvement of the fitting of inflation plus the {lambda}CMB model to the observed CMB spectra. In addition, the corrections to the tensor metric perturbations will provide an independent test of this model. Thus, the effects of quantum inflaton fast

  12. Variable and Extreme Irradiation Conditions in the Early Solar System Inferred from the Initial Abundance of 10Be in Isheyevo CAIs

    NASA Astrophysics Data System (ADS)

    Gounelle, Matthieu; Chaussidon, Marc; Rollion-Bard, Claire

    2013-02-01

    A search for short-lived 10Be in 21 calcium-aluminum-rich inclusions (CAIs) from Isheyevo, a rare CB/CH chondrite, showed that only 5 CAIs had 10B/11B ratios higher than chondritic correlating with the elemental ratio 9Be/11B, suggestive of in situ decay of this key short-lived radionuclide. The initial (10Be/9Be)0 ratios vary between ~10-3 and ~10-2 for CAI 411. The initial ratio of CAI 411 is one order of magnitude higher than the highest ratio found in CV3 CAIs, suggesting that the more likely origin of CAI 411 10Be is early solar system irradiation. The low (26Al/27Al)0 [<= 8.9 × 10-7] with which CAI 411 formed indicates that it was exposed to gradual flares with a proton fluence of a few 1019 protons cm-2, during the earliest phases of the solar system, possibly the infrared class 0. The irradiation conditions for other CAIs are less well constrained, with calculated fluences ranging between a few 1019 and 1020 protons cm-2. The variable and extreme value of the initial 10Be/9Be ratios in carbonaceous chondrite CAIs is the reflection of the variable and extreme magnetic activity in young stars observed in the X-ray domain.

  13. Semiclassical modelling of finite-pulse effects on non-adiabatic photodynamics via initial condition filtering: The predissociation of NaI as a test case

    SciTech Connect

    Martínez-Mesa, Aliezer; Saalfrank, Peter

    2015-05-21

    Femtosecond-laser pulse driven non-adiabatic spectroscopy and dynamics in molecular and condensed phase systems continue to be a challenge for theoretical modelling. One of the main obstacles is the “curse of dimensionality” encountered in non-adiabatic, exact wavepacket propagation. A possible route towards treating complex molecular systems is via semiclassical surface-hopping schemes, in particular if they account not only for non-adiabatic post-excitation dynamics but also for the initial optical excitation. One such approach, based on initial condition filtering, will be put forward in what follows. As a simple test case which can be compared with exact wavepacket dynamics, we investigate the influence of the different parameters determining the shape of a laser pulse (e.g., its finite width and a possible chirp) on the predissociation dynamics of a NaI molecule, upon photoexcitation of the A(0{sup +}) state. The finite-pulse effects are mapped into the initial conditions for semiclassical surface-hopping simulations. The simulated surface-hopping diabatic populations are in qualitative agreement with the quantum mechanical results, especially concerning the subpicosend photoinduced dynamics, the main deviations being the relative delay of the non-adiabatic transitions in the semiclassical picture. Likewise, these differences in the time-dependent electronic populations calculated via the semiclassical and the quantum methods are found to have a mild influence on the overall probability density distribution. As a result, the branching ratios between the bound and the dissociative reaction channels and the time-evolution of the molecular wavepacket predicted by the semiclassical method agree with those computed using quantum wavepacket propagation. Implications for more challenging molecular systems are given.

  14. Innovation of Ozone Initial Concentration and Boundary Condition for Models-3 Community Multi-scale Air Quality (CMAQ) Modeling System Using Ozone Climatology and Its Impacts

    NASA Astrophysics Data System (ADS)

    He, S.; Vukovich, F. M.; Ching, J.; Gilliland, A.

    2002-05-01

    Models-3/CMAQ system is designed to provide a comprehensive and flexible modeling tool for states and other government agencies, and for scientific studies. The current setting of initial concentrations and boundary condition (ICBC) of air species for CMAQ system represents clean ambient condition in the eastern-half of the US, and as such. The ozone ICBC differed from observational values, significantly at upper troposphere. Because of the stratosphere-troposphere exchange, the upper troposphere may contain high concentrations of ozone (hundreds of ppbv). However the current ICBC artificially set ozone level as 70ppbv in upper troposphere throughout model domain. The large difference of standard ozone ICBC from realistic situation becomes considerable uncertainty source of CMAQ system. The purpose of this research is to improve ICBC setting for Models-3/CMAQ modeling system, and to assess the influence of introducing stratospheric ozone into troposphere on regional and urban air quality and on the tropospheric ozone budget. The approach taken is to perform a series of sensitivity studies on ICBC with CMAQ. The simulation covers the entire US with 108km grid resolution from July 2 to 12 of 1988. The domain divide in 34 layers vertically up to 40mbar. In addition to the base case with standard ICBC, ozone initial concentration and boundary condition are generated based on ozone climatology (Logan, 1999), which was derived from surface, satellite, and ozonesonde data across the globe. This new ICBC enables CMAQ model to study ozone cross-tropopause flux transporting to lower troposphere, and to analyze the impact of intercontinental ozone transport. The tropospheric ozone residue (TOR) data is used to compare with modeling tropospheric ozone budget for evaluation of CMAQ performance. Since ozone climatology was based on observation, the derived ozone ICBC are in better agreement with the ``real'' atmosphere than standard ICBC. CMAQ simulations with ozone climatology

  15. Conditions in rural Nepal for which depot-medroxyprogesterone acetate initiation is not recommended: implications for community-based service delivery.

    PubMed

    Rai, C; Thapa, S; Day, J; Bhattarai, L; McMullen, S; Jha, R; Shrestha, S; Bastola, S; Rivera, R

    1999-07-01

    The presence of medical conditions that might affect the use of depot-medroxyprogesterone acetate (DMPA) as a contraceptive method was assessed in a rural district in Nepal. A general health survey was conducted in nonpregnant and noncontracepting women aged 15-44 years to determine the presence of any health problems. The survey included a general assessment interview by nonphysicians, followed by formal medical histories and physical exams by female gynecologists. Possible pregnancy (nine cases) and abnormal uterine bleeding (one case) were the only conditions identified in which DMPA should not be used, based on the World Health Organization (WHO) Medical Eligibility Criteria for Contraceptive Use. Five additional cases of cardiovascular problems, in which DMPA initiation is not usually recommended, were also detected. Recently developed checklists based on the WHO criteria for DMPA use would have identified all of these health conditions. This checklist would allow the safe delivery of DMPA at the community health worker level, and increase the availability and accessibility of DMPA in rural Nepal.

  16. The impact of the uncertainty in the initial soil moisture condition of irrigated areas on the spatiotemporal characteristics of convective activity in Central Greece

    NASA Astrophysics Data System (ADS)

    Kotsopoulos, Stylianos; Ioannis, Tegoulias; Ioannis, Pytharoulis; Stergios, Kartsios; Dimitrios, Bampzelis; Theodore, Karacostas

    2015-04-01

    The region of Thessaly is the second largest plain in Greece and has a vital role in the financial life of the country, because of its significant agricultural production. The intensive and extensive cultivation of irrigated crops, in combination with the population increase and the alteration of precipitation patterns due to climate change, often leading the region to experience severe drought conditions, especially during the warm period of the year. The aim of the DAPHNE project is to tackle the problem of drought in this area by means of Weather Modification.In the framework of the project DAPHNE, the numerical weather prediction model WRF-ARW 3.5.1 is used to provide operational forecasts and hindcasts for the region of Thessaly. The goal of this study is to investigate the impact of the uncertainty in the initial soil moisture condition of irrigated areas, on the spatiotemporal characteristics of convective activity in the region of interest. To this end, six cases under the six most frequent synoptic conditions, which are associated with convective activity in the region of interest, are utilized, considering six different soil moisture initialization scenarios. In the first scenario (Control Run), the model is initialized with the surface soil moisture of the ECMWF analysis data, that usually does not take into account the modification of soil moisture due to agricultural activity in the area of interest. In the other five scenarios (Experiment 1,2,3,4,5) the soil moisture in the upper soil layers of the study area are modified from -50% to 50% of field capacity (-50%FC, -25%FC, FC, 25%FC, 50%FC),for the irrigated cropland.Three model domains, covering Europe, the Mediterranean Sea and northern Africa (d01), the wider area of Greece (d02) and central Greece - Thessaly region (d03) are used at horizontal grid-spacings of 15km, 5km and 1km respectively. ECMWF operational analyses at 6-hourly intervals (0.25ox0.25o lat.-long.) are imported as initial and

  17. The effects of initial acetate concentration on CO2-brine-anorthite interactions under geologic CO2 sequestration conditions

    SciTech Connect

    Yang, Yi; Ronzio, Christian; Jun, Young-Shin

    2011-12-09

    Acetate is one of the most abundant organic compounds in many formation waters and is likely to be present in deep saline aquifers suitable for geologic CO2 sequestration (GCS). This work studied the effect of initially present acetate on the dissolution of anorthite (CaAl2Si2O8) and on subsequent secondary mineral precipitation under GCS conditions (35 °C and 74.8 atm). Anorthite was chosen as a model mineral because of the abundance of feldspar in clayey sandstones and the possibility of metal carbonation. In this study, acetate was found to decrease the cumulative aqueous concentrations of Al, Si, and Ca upon CO2 injection by inhibiting anorthite dissolution and increasing the amount of secondary mineral precipitates. The extent of the effect of acetate on metal concentration changes was element-specific (Al > Si > Ca), and the effect was found to be more significant in systems with lower salinity and lower pH. For anorthite dissolution, acetic acid inhibited the proton-mediated decomposition of the Al/Si-containing feldspar framework, while acetate anions may have facilitated the ion-exchange between interstitial Ca and aqueous cations. For secondary mineral precipitation, stoichiometry analysis of aqueous metal concentrations suggested the formation of Al-containing mineral(s). The presence of kaolinite as a secondary mineral was confirmed using high resolution transmission electron microscopy's electron diffraction data. An increase in the relative amount of precipitation due to the initial presence of acetate was suggested by mass balancing and verified on the cleaved anorthite surfaces by atomic force microscopy analysis. These results provide new insights for understanding and predicting GCS system evolution upon scCO2 injection in the initial presence of acetate.

  18. Feedback about more accurate versus less accurate trials: differential effects on self-confidence and activation.

    PubMed

    Badami, Rokhsareh; VaezMousavi, Mohammad; Wulf, Gabriele; Namazizadeh, Mahdi

    2012-06-01

    One purpose of the present study was to examine whether self-confidence or anxiety would be differentially affected byfeedback from more accurate rather than less accurate trials. The second purpose was to determine whether arousal variations (activation) would predict performance. On day 1, participants performed a golf putting task under one of two conditions: one group received feedback on the most accurate trials, whereas another group received feedback on the least accurate trials. On day 2, participants completed an anxiety questionnaire and performed a retention test. Shin conductance level, as a measure of arousal, was determined. The results indicated that feedback about more accurate trials resulted in more effective learning as well as increased self-confidence. Also, activation was a predictor of performance. PMID:22808705

  19. Residues required for phosphorylation of translation initiation factor eIF2α under diverse stress conditions are divergent between yeast and human

    PubMed Central

    Majumder, Mithu; Mitchell, Daniel; Merkulov, Sergei; Wu, Jing; Guan, Bo-Jhih; Snider, Martin D.; Krokowski, Dawid; Yee, Vivien C.; Hatzoglou, Maria

    2015-01-01

    PERK, PKR, HRI and GCN2 are the four mammalian kinases that phosphorylate the α subunit of the eukaryotic translation initiation factor 2 (eIF2α) on Ser51. This phosphorylation event is conserved among many species and attenuates protein synthesis in response to diverse stress conditions. In contrast, Saccharmyces cerevisiae expresses only the GCN2 kinase. It was demonstrated previously in S. cerevisiae that single point mutations in eIF2α’s N-terminus severely impaired phosphorylation at Ser51. To assess whether similar recognition patterns are present in mammalian eIF2α, we expressed human eIF2α’s with these mutations in mouse embryonic fibroblasts and assessed their phosphorylation under diverse stress conditions. Some of the mutations prevented the stress-induced phosphorylation of eIF2α by all mammalian kinases, thus defining amino acid residues in eIF2α (Gly 30, Leu 50, and Asp 83) that are required for substrate recognition. We also identified residues that were less critical or not required for recognition by the mammalian kinases (Ala 31, Met 44, Lys 79, and Tyr 81), even though they were essential for recognition of the yeast eIF2α by GCN2. We propose that mammalian eIF2α kinases evolved to maximize their interactions with the evolutionarily conserved Ser51 residue of eIF2α in response to diverse stress conditions, thus adding to the complex signaling pathways that mammalian cells have over simpler organisms. PMID:25541374

  20. NNLOPS accurate associated HW production

    NASA Astrophysics Data System (ADS)

    Astill, William; Bizon, Wojciech; Re, Emanuele; Zanderighi, Giulia

    2016-06-01

    We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross section Working Group.

  1. Simulation of blast-furnace raceway conditions in a wire-mesh reactor: interference by the reactions of molybdenum mesh and initial results

    SciTech Connect

    Long Wu; N. Paterson; D.R. Dugwell; R. Kandiyoti

    2006-12-15

    A novel trapped air injection system has been built for a wire-mesh reactor to enable tests with short exposure times to air that are intended to simulate typical residence times in blast-furnace raceways. Initial tests have shown that the molybdenum wire-mesh sample-holder reacts with O{sub 2} under conditions intended for this work. By varying the proportions of solid MoO{sub 2} (weight gain), vapor phase oxides (weight loss) may form, depending on reaction conditions. Oxide formation pathways thus become relevant to coal weight loss determinations during experiments. If, in addition to solid MoO{sub 2} formation, significant formation of vapor phase oxides occurs, then the weight change is more complicated to understand and the impact on the O{sub 2} concentration cannot be unravelled. Furthermore, it turns out that O{sub 2}-scavenging by the mesh affects the amount of O{sub 2} that is available to react with the coal sample. It was concluded that it is only possible to conduct reliable tests under conditions which the favor the formation of solid MoO{sub 2} only, as this leads to a quantifiable weight gain. Its impact can then be accounted for in the evaluation of the experimental weight change. In the case of MoO{sub 2} formation, the impact of the mesh oxidation on the amount of O{sub 2} available to react with the sample can also be estimated. It has been found that the wire-mesh reactor, equipped with the trapped air injection system, can be used to obtain valid data at up to 1600{sup o} C and 0.5 MPa. This pressure is similar to that of the blast-furnace raceway, but the temperature is several hundred degrees lower. However, preliminary tests have shown that useful kinetic data on the extents of reaction can be obtained with the equipment, provided it is operated under conditions that minimize the formation of vapor phase Mo oxides. 18 refs., 13 figs., 3 tabs.

  2. Sensitivity to initial conditions of a d-dimensional long-range-interacting quartic Fermi-Pasta-Ulam model: Universal scaling.

    PubMed

    Bagchi, Debarshee; Tsallis, Constantino

    2016-06-01

    We introduce a generalized d-dimensional Fermi-Pasta-Ulam model in the presence of long-range interactions, and perform a first-principle study of its chaos for d=1,2,3 through large-scale numerical simulations. The nonlinear interaction is assumed to decay algebraically as d_{ij}^{-α} (α≥0), {d_{ij}} being the distances between N oscillator sites. Starting from random initial conditions we compute the maximal Lyapunov exponent λ_{max} as a function of N. Our N≫1 results strongly indicate that λ_{max} remains constant and positive for α/d>1 (implying strong chaos, mixing, and ergodicity), and that it vanishes like N^{-κ} for 0≤α/d<1 (thus approaching weak chaos and opening the possibility of breakdown of ergodicity). The suitably rescaled exponent κ exhibits universal scaling, namely that (d+2)κ depends only on α/d and, when α/d increases from zero to unity, it monotonically decreases from unity to zero, remaining so for all α/d>1. The value α/d=1 can therefore be seen as a critical point separating the ergodic regime from the anomalous one, κ playing a role analogous to that of an order parameter. This scaling law is consistent with Boltzmann-Gibbs statistics for α/d>1, and possibly with q statistics for 0≤α/d<1. PMID:27415261

  3. A preliminary study of the application of HCMM satellite data to define initial and boundary conditions for numerical models: A case study in St. Louis, Missouri

    NASA Technical Reports Server (NTRS)

    Vukovich, F. M. (Principal Investigator)

    1982-01-01

    Infrared and visible HCMM data were used to examine the potential application of these data to define initial and boundary conditions for mesoscale numerical models. Various boundary layer models were used to calculate the distribution of the surface heat flux, specific humidity depression (the difference between the specific humidity in the air at approxmately the 10 m level and the specific humidity at the ground), and the eddy vicosity in a 72 km by 72 km area centered about St. Louis, Missouri. Various aspects of the implications of the results on the meteorology of St. Louis are discussed. Overall, the results indicated that a reasonable estimate of the surface heat flux, urban albedo, ground temperature, and specific humidity depression can be obtained using HCMM satellite data. Values of the ground-specific humidity can be obtained if the distribution of the air-specific humidity is available. More research is required in estimating the absolute magnitude of the specific humidity depression because calculations may be sensitive to model parameters.

  4. Initial fluconazole prophylaxis may not be required in adults with acute leukemia or myelodysplastic/myeloproliferative disorders after reduced intensity conditioning peripheral blood stem cell allogeneic transplantation.

    PubMed

    Brissot, Eolia; Cahu, Xavier; Guillaume, Thierry; Delaunay, Jacques; Ayari, Sameh; Peterlin, Pierre; Le Bourgeois, Amandine; Harousseau, Jean-Luc; Milpied, Noel; Bene, Marie-Christine; Moreau, Philippe; Mohty, Mohamad; Chevallier, Patrice

    2015-04-01

    In the myeloablative transplant setting, the early use of fluconazole prophylaxis provides a benefit in overall survival. Recent changes in transplantation practices, including the use of peripheral blood stem cells (PBSC) and/or reduced intensity conditioning (RIC) regimen may have favorably impacted the epidemiology of invasive fungal infections (IFI) after allogeneic stem cell transplantation (allo-SCT). Yet, the impact of removing fluconazole prophylaxis after RIC PBSC allotransplant is ill known. Here, a retrospective analysis was performed comparing patients who received fluconazole as antifungal prophylaxis (n = 53) or not (n = 56) after allo-SCT for acute leukemia or myelodysplastic/myeloproliferative syndrome. Sixteen IFI were documented (14 %) at a median time of 103 days after transplantation, including eight before day +100, at a similar rate, whether the patients received fluconazole prophylaxis (13 %) or not (16 %). IFI were due mainly to Aspergillus species (87 %), and only two Candida-related IFI (13 %) were documented in the non-fluconazole group before day +100. The incidences of IFI (overall, before or after day +100) as well as 3-year overall and disease-free survival, non-relapse mortality, or acute and chronic graft-versus-host disease (GVHD) were similar between both groups. In conclusion, this study suggests that fluconazole may not be required at the initial phase of RIC allo-SCT using PBSC. This result has to be confirmed prospectively while Aspergillus prophylaxis should be discussed in this particular setting.

  5. Initial Piloted Simulation Evaluation of the Reference-H High-Speed Civil Transport Design During Takeoff and Recovery From Limit Flight Conditions

    NASA Technical Reports Server (NTRS)

    Glaab, Louis J.

    1999-01-01

    An initial assessment of a proposed High-Speed Civil Transport (HSCT) was conducted in the fall of 1995 at the NASA Langley Research Center. This configuration, known as the Industry Reference-H (Ref.-H), was designed by the Boeing Aircraft Company as part of their work in the High Speed Research program. It included a conventional tail, a cranked-arrow wing, four mixed-flow turbofan engines, and capacity for transporting approximately 300 passengers. The purpose of this assessment was to evaluate and quantify operational aspects of the Reference-H configuration from a pilot's perspective with the additional goal of identifying design strengths as well as any potential configuration deficiencies. This study was aimed at evaluating the Ref.-H configuration at many points of the aircraft's envelope to determine the suitability of the vehicle to accomplish typical mission profiles as well as emergency or envelope-limit conditions. Pilot-provided Cooper-Harper ratings and comments constituted the primary vehicle evaluation metric. The analysis included simulated real-time piloted evaluations, performed in a 6 degree of freedom motion base NASA Langley Visual-Motion Simulator, combined with extensive bath analysis. The assessment was performed using the third major release of the simulation data base (known as Ref.-H cycle 2B).

  6. Use of fog water to the initial establishment of tree species under conditions of barren Lomas in the Quebrada Topará, Chincha-Perú

    NASA Astrophysics Data System (ADS)

    Vargas, A.; Cabrera, R.; Bederski, K.; Orellana, A.

    2010-07-01

    The Quebrada Topara is located in the Peruvian coastal desert (13012'L.S, 76009'L.W.) and is influenced by the fog during the winter months, these conditions of high humidity allows its use to achieve the establishment of a permanent vegetation cover Huaquina hill, which is representative at the place of study. Uncounted fog water can be captured and used for irrigation of plants. Also due to the absence of any tree species coverage in this region is not known which or which could have a better performance under these environmental conditions, We used to native species Caesalpinia spinosa "tara" and Schinus molle "molle" also introduced species Casuarina equisetifolia "Casuarina", as these could have a better adaptation. Soil analysis determined a high salinity and nitrogen poverty, preventing water infiltration into the soil and is not used by the plant so that the saline soil difficult to establish plants. This research can be considered an exploratory phase, the objectives were: to determine the potential for fog water harvesting to capture in the study area, to assess for 20 months the initial performance of the species tara, molle and casuarina, and profit incorporation in the final sowing of organic matter and soil amendments to facilitate a better development of plants. 3 standard fog collector (SFC) proposed by Schemenauer and Cereceda (1993) were installed and we evaluated the capture water during 31 months, from June 2007 to December 2009, finding much water collected in the winter months, the average annual in the 3 SFC was similar (1.1, 1.2 and 1.1 L m -2 day-1) which allows us to plan according to necessary the best way to harness and store water to supply the plants. It was found that native species, tara and molle were more adaptable to extreme conditions of the place that introduced casuarina species. The tara does grow faster in height and stem diameter, also achieves a good coverage to intercept fog water itself making it more viable and capable

  7. Approaching system equilibrium with accurate or not accurate feedback information in a two-route system

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-mei; Xie, Dong-fan; Li, Qi

    2015-02-01

    With the development of intelligent transport system, advanced information feedback strategies have been developed to reduce traffic congestion and enhance the capacity. However, previous strategies provide accurate information to travelers and our simulation results show that accurate information brings negative effects, especially in delay case. Because travelers prefer to the best condition route with accurate information, and delayed information cannot reflect current traffic condition but past. Then travelers make wrong routing decisions, causing the decrease of the capacity and the increase of oscillations and the system deviating from the equilibrium. To avoid the negative effect, bounded rationality is taken into account by introducing a boundedly rational threshold BR. When difference between two routes is less than the BR, routes have equal probability to be chosen. The bounded rationality is helpful to improve the efficiency in terms of capacity, oscillation and the gap deviating from the system equilibrium.

  8. Temperature dependence of the yields of methacrolein and methyl vinyl ketone from the OH-initiated oxidation of isoprene under NOx free conditions

    NASA Astrophysics Data System (ADS)

    Navarro, M. A.; Dusanter, S.; Stevens, P. S.; Hites, R. A.

    2010-12-01

    Isoprene, the dominant biogenic hydrocarbon emitted into the atmosphere by deciduous trees, can contribute significantly to the production of tropospheric ozone and secondary organic aerosols due to its high reactivity with oxidants. It is therefore important to correctly describe its oxidation chemistry in models of atmospheric chemistry. However, recent measurements of HOx (OH + HO2) radicals in forest environments show serious discrepancies with modeled concentrations, bringing into question our understanding of the atmospheric chemistry of isoprene and other reactive biogenic compounds. A previous study conducted in our group on the OH-initiated oxidation of isoprene under NOx free conditions indicated that the yields of methacrolein (MAC) and methyl vinyl ketone (MVK) are dependent on the ratio of HO2-to-isoprene-based peroxy radicals (ISORO2). It is likely due to a competition between ISORO2 self- and cross-reactions that leads to the formation of the primary products, with reactions between these peroxy radicals and HO2 which can lead to the formation of peroxides. This presentation will expand the scope of the abovementioned study by investigating the temperature dependence of the yields of MAC and MVK in the range 30-70°C. We will present results from experiments conducted using a small UV-irradiated reaction chamber coupled to an on-line mass spectrometer. In addition, we will compare the measured yields to that predicted by the Master Chemical Mechanism (MCM), including recently proposed radical recycling reactions, to determine whether current models of atmospheric chemistry provide a complete description for the formation of these primary products as a function of temperature.

  9. Effects of Initial Cooling Conditions and Measurement Heights on the Levitation Performance of Bulk MgB Superconductor at Different Measurement Temperatures

    NASA Astrophysics Data System (ADS)

    Erdem, O.; Ozturk, K.; Guner, S. B.; Celik, S.; Yanmaz, E.

    2014-10-01

    The levitation properties of MgB prepared by hot press at 200 C and then pellet/closed tube method has been investigated. The vertical and lateral levitation forces ( and on a cylindrical NdFeB permanent magnet (PM) below a disk-shaped bulk MgB were measured during the vertical and lateral traverses of the PM in different cooling heights (CHs) and measurement heights (MHs) at temperatures of 20, 25 and 30 K to investigate the effect of the initial CH and MH on the levitation performance of MgB. For temperatures below 30 K, it was observed that increases with increasing CH. However, a minute variation in and a big hysteresis loop are observed at 30 K. From the lateral traverses, it was obtained that the with attractive character increases with decreasing MH and the hysteresis effect increases for small MHs due to the increment of the magnetic field intensity which the sample feels with decreasing MH. In addition, it was seen that the character of varies depending on both MH and measurement temperature. The higher hysteresis obtained in than in during lateral traverses implies that the motion of the flux lines in MgB is especially in lateral rather than vertical direction. Finally in this study, it was shown that the levitation performance of MgB depends not only on the measurement temperature but also on the CH and MH conditions. These results can be useful for optimizing the levitation performance of MgB superconductors for potential applications.

  10. Accurate guitar tuning by cochlear implant musicians.

    PubMed

    Lu, Thomas; Huang, Juan; Zeng, Fan-Gang

    2014-01-01

    Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task. PMID:24651081

  11. Accurate Guitar Tuning by Cochlear Implant Musicians

    PubMed Central

    Lu, Thomas; Huang, Juan; Zeng, Fan-Gang

    2014-01-01

    Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task. PMID:24651081

  12. Accurate guitar tuning by cochlear implant musicians.

    PubMed

    Lu, Thomas; Huang, Juan; Zeng, Fan-Gang

    2014-01-01

    Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task.

  13. Precipitation monitoring to accurately depict drought conditions on your allotment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Great Basin Rangelands Research Unit of the U.S. Department of Agriculture, Agricultural Research Service has been reading numerous precipitation gauges throughout the Great Basin for more than three decades. State climatologists, land owners and researchers have obtained data from this long-ter...

  14. Profitable capitation requires accurate costing.

    PubMed

    West, D A; Hicks, L L; Balas, E A; West, T D

    1996-01-01

    In the name of costing accuracy, nurses are asked to track inventory use on per treatment basis when more significant costs, such as general overhead and nursing salaries, are usually allocated to patients or treatments on an average cost basis. Accurate treatment costing and financial viability require analysis of all resources actually consumed in treatment delivery, including nursing services and inventory. More precise costing information enables more profitable decisions as is demonstrated by comparing the ratio-of-cost-to-treatment method (aggregate costing) with alternative activity-based costing methods (ABC). Nurses must participate in this costing process to assure that capitation bids are based upon accurate costs rather than simple averages. PMID:8788799

  15. Accurate documentation and wound measurement.

    PubMed

    Hampton, Sylvie

    This article, part 4 in a series on wound management, addresses the sometimes routine yet crucial task of documentation. Clear and accurate records of a wound enable its progress to be determined so the appropriate treatment can be applied. Thorough records mean any practitioner picking up a patient's notes will know when the wound was last checked, how it looked and what dressing and/or treatment was applied, ensuring continuity of care. Documenting every assessment also has legal implications, demonstrating due consideration and care of the patient and the rationale for any treatment carried out. Part 5 in the series discusses wound dressing characteristics and selection.

  16. Memory conformity affects inaccurate memories more than accurate memories.

    PubMed

    Wright, Daniel B; Villalba, Daniella K

    2012-01-01

    After controlling for initial confidence, inaccurate memories were shown to be more easily distorted than accurate memories. In two experiments groups of participants viewed 50 stimuli and were then presented with these stimuli plus 50 fillers. During this test phase participants reported their confidence that each stimulus was originally shown. This was followed by computer-generated responses from a bogus participant. After being exposed to this response participants again rated the confidence of their memory. The computer-generated responses systematically distorted participants' responses. Memory distortion depended on initial memory confidence, with uncertain memories being more malleable than confident memories. This effect was moderated by whether the participant's memory was initially accurate or inaccurate. Inaccurate memories were more malleable than accurate memories. The data were consistent with a model describing two types of memory (i.e., recollective and non-recollective memories), which differ in how susceptible these memories are to memory distortion.

  17. Adolescents with co-occurring substance use and mental conditions in a private managed care health plan: prevalence, patient characteristics, and treatment initiation and engagement.

    PubMed

    Chi, Felicia W; Sterling, Stacy; Weisner, Constance

    2006-01-01

    This study examined the prevalence, patient characteristics, and treatment initiation and engagement of adolescents with co-occurring substance use (SU) and serious mental health (MH) diagnoses in a private, managed care health plan. We identified 2,005 adolescents aged 12-17, who received both SU and MH diagnoses within a 1-year window between 1/1/2000 and 12/31/2002; 57% were girls. Gender variations were found in diagnoses received and point of identification. Being dually diagnosed in specialty departments (rather than Primary Care and Emergency) and receiving both diagnoses within a shorter time period were associated with treatment initiation and engagement. PMID:17182422

  18. Different target-discrimination times can be followed by the same saccade-initiation timing in different stimulus conditions during visual searches.

    PubMed

    Tanaka, Tomohiro; Nishida, Satoshi; Ogawa, Tadashi

    2015-07-01

    The neuronal processes that underlie visual searches can be divided into two stages: target discrimination and saccade preparation/generation. This predicts that the length of time of the prediscrimination stage varies according to the search difficulty across different stimulus conditions, whereas the length of the latter postdiscrimination stage is stimulus invariant. However, recent studies have suggested that the length of the postdiscrimination interval changes with different stimulus conditions. To address whether and how the visual stimulus affects determination of the postdiscrimination interval, we recorded single-neuron activity in the lateral intraparietal area (LIP) when monkeys (Macaca fuscata) performed a color-singleton search involving four stimulus conditions that differed regarding luminance (Bright vs. Dim) and target-distractor color similarity (Easy vs. Difficult). We specifically focused on comparing activities between the Bright-Difficult and Dim-Easy conditions, in which the visual stimuli were considerably different, but the mean reaction times were indistinguishable. This allowed us to examine the neuronal activity when the difference in the degree of search speed between different stimulus conditions was minimal. We found that not only prediscrimination but also postdiscrimination intervals varied across stimulus conditions: the postdiscrimination interval was longer in the Dim-Easy condition than in the Bright-Difficult condition. Further analysis revealed that the postdiscrimination interval might vary with stimulus luminance. A computer simulation using an accumulation-to-threshold model suggested that the luminance-related difference in visual response strength at discrimination time could be the cause of different postdiscrimination intervals.

  19. The influence of loading conditions on fracture initiation, propagation, and interaction in rocks with veins: Results from a comparative Discrete Element Method study

    NASA Astrophysics Data System (ADS)

    Virgo, Simon; Abe, Steffen; Urai, Janos L.

    2016-03-01

    We present the results of a comparative study of loading conditions on the interactions between extension fractures and veins. We model the fracture behavior of brittle discrete element materials each containing a tabular vein body of variable orientation and strength in two different loading conditions. The first is uniaxial tension, applied with servo-controlled sidewalls. The second is a boudinage boundary condition in which a tensile triaxial stress state is induced in the brittle model volume by quasi-viscous extensional deformation in the adjacent layers. Most of the fracture- vein interactions observed in uniaxial tension also exists in boudinage boundary conditions. However, the importance of each interaction mechanism for a given configuration of relative strength and misorientation of the vein may differ according to the loading mechanism. Nucleation and internal deflection is under both boundary conditions the dominating fracture-vein interaction style in weak veins. In uniaxial tension models, strong veins tend to alter the fracture path by external deflection, while under boudinage loading these veins are more likely overcome by the fracture step over mechanism. Dynamic bifurcation of fractures was observed in uniaxial tension models but never for boudinage boundary conditions. This is because the acceleration of fracture tips in these conditions is suppressed by interaction with distributed fractures as well as viscous damping by the neighboring layers.

  20. The importance of accurate atmospheric modeling

    NASA Astrophysics Data System (ADS)

    Payne, Dylan; Schroeder, John; Liang, Pang

    2014-11-01

    This paper will focus on the effect of atmospheric conditions on EO sensor performance using computer models. We have shown the importance of accurately modeling atmospheric effects for predicting the performance of an EO sensor. A simple example will demonstrated how real conditions for several sites in China will significantly impact on image correction, hyperspectral imaging, and remote sensing. The current state-of-the-art model for computing atmospheric transmission and radiance is, MODTRAN® 5, developed by the US Air Force Research Laboratory and Spectral Science, Inc. Research by the US Air Force, Navy and Army resulted in the public release of LOWTRAN 2 in the early 1970's. Subsequent releases of LOWTRAN and MODTRAN® have continued until the present. Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact author_help@spie.org with any questions or concerns. The paper will demonstrate the importance of using validated models and local measured meteorological, atmospheric and aerosol conditions to accurately simulate the atmospheric transmission and radiance. Frequently default conditions are used which can produce errors of as much as 75% in these values. This can have significant impact on remote sensing applications.

  1. Accurate Stellar Parameters for Exoplanet Host Stars

    NASA Astrophysics Data System (ADS)

    Brewer, John Michael; Fischer, Debra; Basu, Sarbani; Valenti, Jeff A.

    2015-01-01

    A large impedement to our understanding of planet formation is obtaining a clear picture of planet radii and densities. Although determining precise ratios between planet and stellar host are relatively easy, determining accurate stellar parameters is still a difficult and costly undertaking. High resolution spectral analysis has traditionally yielded precise values for some stellar parameters but stars in common between catalogs from different authors or analyzed using different techniques often show offsets far in excess of their uncertainties. Most analyses now use some external constraint, when available, to break observed degeneracies between surface gravity, effective temperature, and metallicity which can otherwise lead to correlated errors in results. However, these external constraints are impossible to obtain for all stars and can require more costly observations than the initial high resolution spectra. We demonstrate that these discrepencies can be mitigated by use of a larger line list that has carefully tuned atomic line data. We use an iterative modeling technique that does not require external constraints. We compare the surface gravity obtained with our spectral synthesis modeling to asteroseismically determined values for 42 Kepler stars. Our analysis agrees well with only a 0.048 dex offset and an rms scatter of 0.05 dex. Such accurate stellar gravities can reduce the primary source of uncertainty in radii by almost an order of magnitude over unconstrained spectral analysis.

  2. SPLASH: Accurate OH maser positions

    NASA Astrophysics Data System (ADS)

    Walsh, Andrew; Gomez, Jose F.; Jones, Paul; Cunningham, Maria; Green, James; Dawson, Joanne; Ellingsen, Simon; Breen, Shari; Imai, Hiroshi; Lowe, Vicki; Jones, Courtney

    2013-10-01

    The hydroxyl (OH) 18 cm lines are powerful and versatile probes of diffuse molecular gas, that may trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. In this proposal, we request ATCA time to follow up OH maser candidates. This will give us accurate (~10") positions of the masers, which can be compared to other maser positions from HOPS, MMB and MALT-45 and will provide full polarisation measurements towards a sample of OH masers that have not been observed in MAGMO.

  3. Accurate thickness measurement of graphene

    NASA Astrophysics Data System (ADS)

    Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.

    2016-03-01

    Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.

  4. Accurate thickness measurement of graphene.

    PubMed

    Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T

    2016-03-29

    Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.

  5. Accurate Weather Forecasting for Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Maddalena, Ronald J.

    2010-01-01

    The NRAO Green Bank Telescope routinely observes at wavelengths from 3 mm to 1 m. As with all mm-wave telescopes, observing conditions depend upon the variable atmospheric water content. The site provides over 100 days/yr when opacities are low enough for good observing at 3 mm, but winds on the open-air structure reduce the time suitable for 3-mm observing where pointing is critical. Thus, to maximum productivity the observing wavelength needs to match weather conditions. For 6 years the telescope has used a dynamic scheduling system (recently upgraded; www.gb.nrao.edu/DSS) that requires accurate multi-day forecasts for winds and opacities. Since opacity forecasts are not provided by the National Weather Services (NWS), I have developed an automated system that takes available forecasts, derives forecasted opacities, and deploys the results on the web in user-friendly graphical overviews (www.gb.nrao.edu/ rmaddale/Weather). The system relies on the "North American Mesoscale" models, which are updated by the NWS every 6 hrs, have a 12 km horizontal resolution, 1 hr temporal resolution, run to 84 hrs, and have 60 vertical layers that extend to 20 km. Each forecast consists of a time series of ground conditions, cloud coverage, etc, and, most importantly, temperature, pressure, humidity as a function of height. I use the Liebe's MWP model (Radio Science, 20, 1069, 1985) to determine the absorption in each layer for each hour for 30 observing wavelengths. Radiative transfer provides, for each hour and wavelength, the total opacity and the radio brightness of the atmosphere, which contributes substantially at some wavelengths to Tsys and the observational noise. Comparisons of measured and forecasted Tsys at 22.2 and 44 GHz imply that the forecasted opacities are good to about 0.01 Nepers, which is sufficient for forecasting and accurate calibration. Reliability is high out to 2 days and degrades slowly for longer-range forecasts.

  6. Accurate free energy calculation along optimized paths.

    PubMed

    Chen, Changjun; Xiao, Yi

    2010-05-01

    The path-based methods of free energy calculation, such as thermodynamic integration and free energy perturbation, are simple in theory, but difficult in practice because in most cases smooth paths do not exist, especially for large molecules. In this article, we present a novel method to build the transition path of a peptide. We use harmonic potentials to restrain its nonhydrogen atom dihedrals in the initial state and set the equilibrium angles of the potentials as those in the final state. Through a series of steps of geometrical optimization, we can construct a smooth and short path from the initial state to the final state. This path can be used to calculate free energy difference. To validate this method, we apply it to a small 10-ALA peptide and find that the calculated free energy changes in helix-helix and helix-hairpin transitions are both self-convergent and cross-convergent. We also calculate the free energy differences between different stable states of beta-hairpin trpzip2, and the results show that this method is more efficient than the conventional molecular dynamics method in accurate free energy calculation.

  7. Biological and Environmental Initial Conditions Shape the Trajectories of Cognitive and Social-Emotional Development across the First Years of Life

    ERIC Educational Resources Information Center

    Feldman, Ruth; Eidelman, Arthur I.

    2009-01-01

    Human development is thought to evolve from the dynamic interchange of biological dispositions and environmental provisions; yet the effects of specific biological and environmental birth conditions on the trajectories of cognitive and social-emotional growth have rarely been studied. We observed 126 children at six time-points from birth to 5…

  8. Motor equivalence during multi-finger accurate force production

    PubMed Central

    Mattos, Daniela; Schöner, Gregor; Zatsiorsky, Vladimir M.; Latash, Mark L.

    2014-01-01

    We explored stability of multi-finger cyclical accurate force production action by analysis of responses to small perturbations applied to one of the fingers and inter-cycle analysis of variance. Healthy subjects performed two versions of the cyclical task, with and without an explicit target. The “inverse piano” apparatus was used to lift/lower a finger by 1 cm over 0.5 s; the subjects were always instructed to perform the task as accurate as they could at all times. Deviations in the spaces of finger forces and modes (hypothetical commands to individual fingers) were quantified in directions that did not change total force (motor equivalent) and in directions that changed the total force (non-motor equivalent). Motor equivalent deviations started immediately with the perturbation and increased progressively with time. After a sequence of lifting-lowering perturbations leading to the initial conditions, motor equivalent deviations were dominating. These phenomena were less pronounced for analysis performed with respect to the total moment of force with respect to an axis parallel to the forearm/hand. Analysis of inter-cycle variance showed consistently higher variance in a subspace that did not change the total force as compared to the variance that affected total force. We interpret the results as reflections of task-specific stability of the redundant multi-finger system. Large motor equivalent deviations suggest that reactions of the neuromotor system to a perturbation involve large changes of neural commands that do not affect salient performance variables, even during actions with the purpose to correct those salient variables. Consistency of the analyses of motor equivalence and variance analysis provides additional support for the idea of task-specific stability ensured at a neural level. PMID:25344311

  9. Motor equivalence during multi-finger accurate force production.

    PubMed

    Mattos, Daniela; Schöner, Gregor; Zatsiorsky, Vladimir M; Latash, Mark L

    2015-02-01

    We explored stability of multi-finger cyclical accurate force production action by analysis of responses to small perturbations applied to one of the fingers and inter-cycle analysis of variance. Healthy subjects performed two versions of the cyclical task, with and without an explicit target. The "inverse piano" apparatus was used to lift/lower a finger by 1 cm over 0.5 s; the subjects were always instructed to perform the task as accurate as they could at all times. Deviations in the spaces of finger forces and modes (hypothetical commands to individual fingers) were quantified in directions that did not change total force (motor equivalent) and in directions that changed the total force (non-motor equivalent). Motor equivalent deviations started immediately with the perturbation and increased progressively with time. After a sequence of lifting-lowering perturbations leading to the initial conditions, motor equivalent deviations were dominating. These phenomena were less pronounced for analysis performed with respect to the total moment of force with respect to an axis parallel to the forearm/hand. Analysis of inter-cycle variance showed consistently higher variance in a subspace that did not change the total force as compared to the variance that affected total force. We interpret the results as reflections of task-specific stability of the redundant multi-finger system. Large motor equivalent deviations suggest that reactions of the neuromotor system to a perturbation involve large changes in neural commands that do not affect salient performance variables, even during actions with the purpose to correct those salient variables. Consistency of the analyses of motor equivalence and variance analysis provides additional support for the idea of task-specific stability ensured at a neural level. PMID:25344311

  10. Accurate upwind methods for the Euler equations

    NASA Technical Reports Server (NTRS)

    Huynh, Hung T.

    1993-01-01

    A new class of piecewise linear methods for the numerical solution of the one-dimensional Euler equations of gas dynamics is presented. These methods are uniformly second-order accurate, and can be considered as extensions of Godunov's scheme. With an appropriate definition of monotonicity preservation for the case of linear convection, it can be shown that they preserve monotonicity. Similar to Van Leer's MUSCL scheme, they consist of two key steps: a reconstruction step followed by an upwind step. For the reconstruction step, a monotonicity constraint that preserves uniform second-order accuracy is introduced. Computational efficiency is enhanced by devising a criterion that detects the 'smooth' part of the data where the constraint is redundant. The concept and coding of the constraint are simplified by the use of the median function. A slope steepening technique, which has no effect at smooth regions and can resolve a contact discontinuity in four cells, is described. As for the upwind step, existing and new methods are applied in a manner slightly different from those in the literature. These methods are derived by approximating the Euler equations via linearization and diagonalization. At a 'smooth' interface, Harten, Lax, and Van Leer's one intermediate state model is employed. A modification for this model that can resolve contact discontinuities is presented. Near a discontinuity, either this modified model or a more accurate one, namely, Roe's flux-difference splitting. is used. The current presentation of Roe's method, via the conceptually simple flux-vector splitting, not only establishes a connection between the two splittings, but also leads to an admissibility correction with no conditional statement, and an efficient approximation to Osher's approximate Riemann solver. These reconstruction and upwind steps result in schemes that are uniformly second-order accurate and economical at smooth regions, and yield high resolution at discontinuities.

  11. Initial inhomogeneity-induced crazy-clock behavior in the iodate-arsenous acid reaction in a buffered medium under stirred batch conditions.

    PubMed

    Valkai, László; Csekő, György; Horváth, Attila K

    2015-09-14

    It is unambiguously demonstrated that in the case of an autocatalytic reaction, initial inhomogeneities induced by the imperfectly mixed part of the overall volume may result in a serious irreproducibility of the individual kinetic runs. A statistically meaningful number of repetitions, however, gives rise to a reproducible cumulative probability distribution curve often referred to as a support of the stochastic feature. The iodate-arsenous acid reaction being autocatalytic with respect to both iodide and hydrogen ions displays clock behavior. However, the time lag necessary for the appearance of iodine, even in buffered solution, varies in an apparently random manner. Careful analysis of the variation of the different parameters like stirring rate, overall volume, geometry of the reactor and the way of mixing the reactants led us to conclude that the fate of the individual samples is determined at the initial stage when the reacting system is per se inhomogeneous. The place, the size of the so-called ignition volume, where the reacting system is imperfectly stirred, as well as the residence time spent there by the imperfectly mixed reactants all seem to depend on external factors. PMID:26239390

  12. Connecting the dots: Semi-analytical and random walk numerical solutions of the diffusion–reaction equation with stochastic initial conditions

    SciTech Connect

    Paster, Amir; Bolster, Diogo; Benson, David A.

    2014-04-15

    We study a system with bimolecular irreversible kinetic reaction A+B→∅ where the underlying transport of reactants is governed by diffusion, and the local reaction term is given by the law of mass action. We consider the case where the initial concentrations are given in terms of an average and a white noise perturbation. Our goal is to solve the diffusion–reaction equation which governs the system, and we tackle it with both analytical and numerical approaches. To obtain an analytical solution, we develop the equations of moments and solve them approximately. To obtain a numerical solution, we develop a grid-less Monte Carlo particle tracking approach, where diffusion is modeled by a random walk of the particles, and reaction is modeled by annihilation of particles. The probability of annihilation is derived analytically from the particles' co-location probability. We rigorously derive the relationship between the initial number of particles in the system and the amplitude of white noise represented by that number. This enables us to compare the particle simulations and the approximate analytical solution and offer an explanation of the late time discrepancies. - Graphical abstract:.

  13. Connecting the dots: Semi-analytical and random walk numerical solutions of the diffusion-reaction equation with stochastic initial conditions

    NASA Astrophysics Data System (ADS)

    Paster, Amir; Bolster, Diogo; Benson, David A.

    2014-04-01

    We study a system with bimolecular irreversible kinetic reaction A+B→∅ where the underlying transport of reactants is governed by diffusion, and the local reaction term is given by the law of mass action. We consider the case where the initial concentrations are given in terms of an average and a white noise perturbation. Our goal is to solve the diffusion-reaction equation which governs the system, and we tackle it with both analytical and numerical approaches. To obtain an analytical solution, we develop the equations of moments and solve them approximately. To obtain a numerical solution, we develop a grid-less Monte Carlo particle tracking approach, where diffusion is modeled by a random walk of the particles, and reaction is modeled by annihilation of particles. The probability of annihilation is derived analytically from the particles' co-location probability. We rigorously derive the relationship between the initial number of particles in the system and the amplitude of white noise represented by that number. This enables us to compare the particle simulations and the approximate analytical solution and offer an explanation of the late time discrepancies.

  14. A practical method based on stress evaluation ({sigma}{sub d} criterion) to predict initiation of crack under creep and creep-fatigue conditions

    SciTech Connect

    Moulin, D.; Drubay, B.; Acker, D.; Laiarinandrasana, L.

    1995-11-01

    In some parts of primary circuit of fast breeder reactor, where the temperature is higher than 427 C, preservice inspection has revealed indications that were conservatively assumed to be sharp cracks. These pipes are made of 316 SPH material, an austenitic material close to 316L. This material is subjected to creep behavior at this temperature. Here, the behavior of defects like cracks in nuclear components operating at high temperature, where creep is significant, must be under control. There exists the need to have a practical method of analysis, which can be used by engineers, to calculate the time of initiation for defects existing at the start of life of nuclear components. This study presents the background, the development, the application, and results concerning validation work made for a simplified method named {sigma}{sub d} of prediction of initiation for nuclear structures made of 316L austenitic steel and operating at temperature where creep is significant. This method relies on the evaluation of real stress-strain history on a small distance d (d = 0.05 mm) close to the crack front and material characteristics (limiting stresses) that are available in nuclear codes like ASME Code cases or RCC-MR.

  15. Entropy growth in the early universe and confirmation of initial big bang conditions (Why the quark-gluon model is not the best analogy)

    NASA Astrophysics Data System (ADS)

    Beckwith, Andrew

    2009-10-01

    This paper shows how increased entropy values from an initially low big bang level can be measured experimentally by counting relic gravitons. Furthermore the physical mechanism of this entropy increase is explained via analogies with early-universe phase transitions. The role of Jack Ng's revised infinite quantum statistics in the physics of gravitational wave detection is acknowledged. Ng's infinite quantum statistics can be used to show that δS δNgravitons is a starting point to the increasing net universe cosmological entropy. Furthermore, we compare the increase in relic gravitons with ``chilled neutrinos'' generated as of at the start of the pre CMBR era, before CMBR ``turned on'' roughly 400 thousand years after the big bang.

  16. Model simulation studies to clarify the effect on saccadic eye movements of initial condition velocities set by the Vestibular Ocular Reflex (VOR)

    NASA Technical Reports Server (NTRS)

    Nam, M. H.; Winters, J. M.; Stark, L.

    1981-01-01

    Voluntary active head rotations produced vestibulo-ocular reflex eye movements (VOR) with the subject viewing a fixation target. When this target jumped, the size of the refixation saccades were a function of the ongoing initial velocity of the eye. Saccades made against the VOR were larger in magnitude. Simulation of a reciprocally innervated model eye movement provided results comparable to the experimental data. Most of the experimental effect appeared to be due to linear summation for saccades of 5 and 10 degree magnitude. For small saccades of 2.5 degrees, peripheral nonlinear interaction of state variables in the neuromuscular plant also played a role as proven by comparable behavior in the simulated model with known controller signals.

  17. Towards Accurate Molecular Modeling of Plastic Bonded Explosives

    NASA Astrophysics Data System (ADS)

    Chantawansri, T. L.; Andzelm, J.; Taylor, D.; Byrd, E.; Rice, B.

    2010-03-01

    There is substantial interest in identifying the controlling factors that influence the susceptibility of polymer bonded explosives (PBXs) to accidental initiation. Numerous Molecular Dynamics (MD) simulations of PBXs using the COMPASS force field have been reported in recent years, where the validity of the force field in modeling the solid EM fill has been judged solely on its ability to reproduce lattice parameters, which is an insufficient metric. Performance of the COMPASS force field in modeling EMs and the polymeric binder has been assessed by calculating structural, thermal, and mechanical properties, where only fair agreement with experimental data is obtained. We performed MD simulations using the COMPASS force field for the polymer binder hydroxyl-terminated polybutadiene and five EMs: cyclotrimethylenetrinitramine, 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclo-octane, 2,4,6,8,10,12-hexantirohexaazazisowurzitane, 2,4,6-trinitro-1,3,5-benzenetriamine, and pentaerythritol tetranitate. Predicted EM crystallographic and molecular structural parameters, as well as calculated properties for the binder will be compared with experimental results for different simulation conditions. We also present novel simulation protocols, which improve agreement between experimental and computation results thus leading to the accurate modeling of PBXs.

  18. A Laboratory Test Setup for in Situ Measurements of the Dielectric Properties of Catalyst Powder Samples under Reaction Conditions by Microwave Cavity Perturbation: Set up and Initial Tests

    PubMed Central

    Dietrich, Markus; Rauch, Dieter; Porch, Adrian; Moos, Ralf

    2014-01-01

    The catalytic behavior of zeolite catalysts for the ammonia-based selective catalytic reduction (SCR) of nitrogen oxides (NOX) depends strongly on the type of zeolite material. An essential precondition for SCR is a previous ammonia gas adsorption that occurs on acidic sites of the zeolite. In order to understand and develop SCR active materials, it is crucial to know the amount of sorbed ammonia under reaction conditions. To support classical temperature-programmed desorption (TPD) experiments, a correlation of the dielectric properties with the catalytic properties and the ammonia sorption under reaction conditions appears promising. In this work, a laboratory test setup, which enables direct measurements of the dielectric properties of catalytic powder samples under a defined gas atmosphere and temperature by microwave cavity perturbation, has been developed. Based on previous investigations and computational simulations, a resonator cavity and a heating system were designed, installed and characterized. The resonator cavity is designed to operate in its TM010 mode at 1.2 GHz. The first measurement of the ammonia loading of an H-ZSM-5 zeolite confirmed the operating performance of the test setup at constant temperatures of up to 300 °C. It showed how both real and imaginary parts of the relative complex permittivity are strongly correlated with the mass of stored ammonia. PMID:25211199

  19. Effecting change in primary care management of respiratory conditions: a global scoping exercise and literature review of educational interventions to inform the IPCRG's E-Quality initiative.

    PubMed

    McDonnell, Juliet; Williams, Siân; Chavannes, Niels H; Correia de Sousa, Jaime; Fardy, H John; Fletcher, Monica; Stout, James; Tomlins, Ron; Yusuf, Osman M; Pinnock, Hilary

    2012-12-01

    This discussion paper describes a scoping exercise and literature review commissioned by the International Primary Care Respiratory Group (IPCRG) to inform their E-Quality programme which seeks to support small-scale educational projects to improve respiratory management in primary care. Our narrative review synthesises information from three sources: publications concerning the global context and health systems development; a literature search of Medline, CINAHL and Cochrane databases; and a series of eight interviews conducted with members of the IPCRG faculty. Educational interventions sit within complex healthcare, economic, and policy contexts. It is essential that any development project considers the local circumstances in terms of economic resources, political circumstances, organisation and administrative capacities, as well as the specific quality issue to be addressed. There is limited evidence (in terms of changed clinician behaviour and/or improved health outcomes) regarding the merits of different educational and quality improvement approaches. Features of educational interventions that were most likely to show some evidence of effectiveness included being carefully designed, multifaceted, engaged health professionals in their learning, provided ongoing support, were sensitive to local circumstances, and delivered in combination with other quality improvement strategies. To be effective, educational interventions must consider the complex healthcare systems within which they operate. The criteria for the IPCRG E-Quality awards thus require applicants not only to describe their proposed educational initiative but also to consider the practical and local barriers to successful implementation, and to propose a robust evaluation in terms of changed clinician behaviour or improved health outcomes. PMID:22875141

  20. Small dispersion limit of the Korteweg-de Vries equation with periodic initial conditions and analytical description of the Zabusky-Kruskal experiment

    NASA Astrophysics Data System (ADS)

    Deng, Guo; Biondini, Gino; Trillo, Stefano

    2016-10-01

    We study the small dispersion limit of the Korteweg-de Vries (KdV) equation with periodic boundary conditions and we apply the results to the Zabusky-Kruskal experiment. In particular, we employ a WKB approximation for the solution of the scattering problem for the KdV equation [i.e., the time-independent Schrödinger equation] to obtain an asymptotic expression for the trace of the monodromy matrix and thereby of the spectrum of the problem. We then perform a detailed analysis of the structure of said spectrum (i.e., band widths, gap widths and relative band widths) as a function of the dispersion smallness parameter ɛ. We then formulate explicit approximations for the number of solitons and corresponding soliton amplitudes as a function of ɛ. Finally, by performing an appropriate rescaling, we compare our results to those in the famous Zabusky and Kruskal's paper, showing very good agreement with the numerical results.

  1. Developing a public health-tracking system for follow-up of newborn screening metabolic conditions: a four-state pilot project structure and initial findings

    PubMed Central

    Hinton, Cynthia F.; Mai, Cara T.; Nabukera, Sarah K.; Botto, Lorenzo D.; Feuchtbaum, Lisa; Romitti, Paul A.; Wang, Ying; Piper, Kimberly Noble; Olney, Richard S.

    2016-01-01

    Purpose The aim of this study was to describe the methods, cases, and initial results of a pilot project using existing public health data collection programs (birth defect surveillance or newborn screening) to conduct long-term follow-up of children with metabolic disorders. Methods California, Iowa, New York, and Utah expanded birth defect surveillance or newborn screening programs to collect long-term follow-up data on 19 metabolic disorders. Data elements to monitor health status and services delivered were identified, and record abstraction and data linkages were conducted. Children were followed up through to the age of 3 years. Results A total of 261 metabolic cases were diagnosed in 1,343,696 live births (19.4 cases/100,000; 95% confidence interval = 17.1–21.8). Four deaths were identified. Children with fatty acid oxidation disorders had a higher percentage of health service encounters compared with children with other disorders of at least one health service encounter (hospitalization, emergency room, metabolic clinic, genetic service provider, or social worker) except for hospitalizations; children with organic acid disorders had a higher percentage of at least one hospitalization during their third year of life than children with other disorders. Conclusion Existing public health data programs can be leveraged to conduct population-based newborn screening long-term follow-up. This approach is flexible according to state needs and resources. These data will enable the states in assessing health burden, assuring access to services, and supporting policy development. PMID:24310309

  2. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  3. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  4. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  5. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  6. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  7. Pre-eruptive storage conditions of the Huckleberry Ridge Tuff from quartz-hosted melt inclusions in the initial fall deposits

    NASA Astrophysics Data System (ADS)

    Myers, M.; Wallace, P. J.; Wilson, C. J.

    2013-12-01

    boundaries, and (c) crystals that lack any zoning. Analyses of reentrants provide information on conditions during late-stage assembly that can be compared with fully sealed inclusions trapped during earlier crystallization stages. The reentrants have higher F concentrations than the majority of inclusions (~0.5-0.7 wt.%) and CO2 below detection, documenting changing conditions in the system either during or shortly before the eruption.

  8. Accurate, reliable prototype earth horizon sensor head

    NASA Technical Reports Server (NTRS)

    Schwarz, F.; Cohen, H.

    1973-01-01

    The design and performance is described of an accurate and reliable prototype earth sensor head (ARPESH). The ARPESH employs a detection logic 'locator' concept and horizon sensor mechanization which should lead to high accuracy horizon sensing that is minimally degraded by spatial or temporal variations in sensing attitude from a satellite in orbit around the earth at altitudes in the 500 km environ 1,2. An accuracy of horizon location to within 0.7 km has been predicted, independent of meteorological conditions. This corresponds to an error of 0.015 deg-at 500 km altitude. Laboratory evaluation of the sensor indicates that this accuracy is achieved. First, the basic operating principles of ARPESH are described; next, detailed design and construction data is presented and then performance of the sensor under laboratory conditions in which the sensor is installed in a simulator that permits it to scan over a blackbody source against background representing the earth space interface for various equivalent plant temperatures.

  9. Transition to turbulence and effect of initial conditions on three-dimensional compressible mixing in planar blast-wave-driven systems

    SciTech Connect

    Miles, A.R.; Blue, B.; Edwards, M.J.; Greenough, J.A.; Hansen, J.F.; Robey, H.F.; Drake, R.P.; Kuranz, C.; Leibrandt, D.R.

    2005-05-15

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional (3D) numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] are presented. Using the multiphysics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J. A. Greenough, J. Comput. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pretransition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernovae are discussed.

  10. Transition to turbulence and effect of initial conditions on three-dimensional compressible mixing in planar blast-wave-driven systemsa)

    NASA Astrophysics Data System (ADS)

    Miles, A. R.; Blue, B.; Edwards, M. J.; Greenough, J. A.; Hansen, J. F.; Robey, H. F.; Drake, R. P.; Kuranz, C.; Leibrandt, D. R.

    2005-05-01

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional (3D) numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] are presented. Using the multiphysics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J. A. Greenough, J. Comput. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pretransition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernovae are discussed.

  11. Accurate Mass Measurements in Proteomics

    SciTech Connect

    Liu, Tao; Belov, Mikhail E.; Jaitly, Navdeep; Qian, Weijun; Smith, Richard D.

    2007-08-01

    To understand different aspects of life at the molecular level, one would think that ideally all components of specific processes should be individually isolated and studied in details. Reductionist approaches, i.e., studying one biological event at a one-gene or one-protein-at-a-time basis, indeed have made significant contributions to our understanding of many basic facts of biology. However, these individual “building blocks” can not be visualized as a comprehensive “model” of the life of cells, tissues, and organisms, without using more integrative approaches.1,2 For example, the emerging field of “systems biology” aims to quantify all of the components of a biological system to assess their interactions and to integrate diverse types of information obtainable from this system into models that could explain and predict behaviors.3-6 Recent breakthroughs in genomics, proteomics, and bioinformatics are making this daunting task a reality.7-14 Proteomics, the systematic study of the entire complement of proteins expressed by an organism, tissue, or cell under a specific set of conditions at a specific time (i.e., the proteome), has become an essential enabling component of systems biology. While the genome of an organism may be considered static over short timescales, the expression of that genome as the actual gene products (i.e., mRNAs and proteins) is a dynamic event that is constantly changing due to the influence of environmental and physiological conditions. Exclusive monitoring of the transcriptomes can be carried out using high-throughput cDNA microarray analysis,15-17 however the measured mRNA levels do not necessarily correlate strongly with the corresponding abundances of proteins,18-20 The actual amount of functional proteins can be altered significantly and become independent of mRNA levels as a result of post-translational modifications (PTMs),21 alternative splicing,22,23 and protein turnover.24,25 Moreover, the functions of expressed

  12. Increased belowground C release during initial plant development of Populus deltoides x nigra grown under light and C reserve limited conditions

    NASA Astrophysics Data System (ADS)

    Studer, Mirjam S.; Siegwolf, Rolf T. W.; Schmidt, Michael W. I.; Abiven, Samuel

    2014-05-01

    Plants might be a key factor for the long-term stabilisation of carbon (C) in the soil, e.g. through enhanced physical protection of root-derived C against microbial decomposition in soil aggregates. On the other hand C released by the plants into the soil might promote the decomposition of native soil organic matter (SOM) through the stimulation of microbial activity. We measured the C budget of developing plant-soil systems (Populus deltoides x nigra, Cambisol soil) in the laboratory under controlled environmental conditions. In order to distinguish plant-derived from native C in the SOM and the soil CO2 efflux, we labelled the poplar shoots continuously with 13C-CO2 from first emergence of leaves (sprouting from stem cuttings). Throughout the experiment the CO2 fluxes (photosynthetic assimilation, dark respiratory loss, soil CO2 efflux) were measured frequently (every 30 min) and the 13C was traced in the soil CO2 efflux (1-2 times a week). After 10 weeks the plant-soil systems were destructively harvested and the distribution of the 13C distribution was analysed. The plants developed slowly (compared to previous experiments), most likely due to limitation in C reserves (long term cutting storage) and C supply (low light intensities). The amount of 13C recovered in the roots, microbial biomass and soil CO2 efflux was directly correlated with the leaf area of the different plant individuals. After 3-4 weeks of plant development we observed a high peak in the total soil CO2 efflux. During this time the relative belowground C release was increased massively over the basal rate of 17 % of net C assimilated, whereby the variability between the plant individuals was large. The smallest plants, i.e. the plants that were most resource limited, obtained the highest belowground C release accounting at the peak time for up to 57 % of net assimilated C. We hypothesize that the plants released specific compounds, which either directly (enzymatically) or indirectly (priming

  13. Research Initiatives

    Cancer.gov

    This page provides detailed information about currently funded RFA initiatives both led by DCCPS, and those led by other NIH Institutes and Centers (I/Cs) that include DCCPS as a partner. Each initiative includes a table of funded grants and a map that shows the location of funded institutions.

  14. A fourth order accurate adaptive mesh refinement method forpoisson's equation

    SciTech Connect

    Barad, Michael; Colella, Phillip

    2004-08-20

    We present a block-structured adaptive mesh refinement (AMR) method for computing solutions to Poisson's equation in two and three dimensions. It is based on a conservative, finite-volume formulation of the classical Mehrstellen methods. This is combined with finite volume AMR discretizations to obtain a method that is fourth-order accurate in solution error, and with easily verifiable solvability conditions for Neumann and periodic boundary conditions.

  15. EUROANDRILL Initiative

    NASA Astrophysics Data System (ADS)

    Florindo, Fabio; Steering Committee, Euroandrill

    2010-05-01

    EuroANDRILL is a new initiative to create a European network with the goal to increase future involvement of European countries in the ANDRILL [ANtarctic geological DRILLing] Programme. Antarctica has been heavily glaciated for approximately 34 million years, but its ice sheets have fluctuated considerably and are one of the major driving forces for changes in climate throughout the Cenozoic Era. The spatial scale and temporal pattern of these fluctuations is subject to considerable debate. Understanding the response of large ice masses to climatic forcing is of vital importance because ice volume variations drive global sea level changes and also alter the capacity of ice sheets and sea-ice to act as major heat sinks/insulators. It is particularly important to assess the stability of the cryosphere in the face of rising CO2 levels, as modelling of the climate shift from a warm, vegetated Antarctica to a cold, ice-covered state 34 million years ago suggests a powerful greenhouse gas influence. As Antarctica is the major driver of Earth's climate and sea level, much effort has been expended in deriving models of its behaviour. Some of these models have been successfully validated against modern conditions. EuroANDRILL will provide a coherent, integrated platform for European leadership and involvement in the international ANDRILL programme. The coordination and networking provided by EuroANDRILL will seek to expand participation by European nations, institutions, and individual scientists in the study of the geologic history of the polar regions and their paleoclimatic significance. During the IPY, ANDRILL has been a highly visible and successful programme. This programme seeks to expand on this legacy beyond the IPY and make these contributions sustainable in the European Research Area through networking of research projects and future planning efforts, which establish Europe as a key player in future polar sediment and rock drilling. EuroANDRILL is set up under

  16. Learning fast accurate movements requires intact frontostriatal circuits

    PubMed Central

    Shabbott, Britne; Ravindran, Roshni; Schumacher, Joseph W.; Wasserman, Paula B.; Marder, Karen S.; Mazzoni, Pietro

    2013-01-01

    The basal ganglia are known to play a crucial role in movement execution, but their importance for motor skill learning remains unclear. Obstacles to our understanding include the lack of a universally accepted definition of motor skill learning (definition confound), and difficulties in distinguishing learning deficits from execution impairments (performance confound). We studied how healthy subjects and subjects with a basal ganglia disorder learn fast accurate reaching movements. We addressed the definition and performance confounds by: (1) focusing on an operationally defined core element of motor skill learning (speed-accuracy learning), and (2) using normal variation in initial performance to separate movement execution impairment from motor learning abnormalities. We measured motor skill learning as performance improvement in a reaching task with a speed-accuracy trade-off. We compared the performance of subjects with Huntington's disease (HD), a neurodegenerative basal ganglia disorder, to that of premanifest carriers of the HD mutation and of control subjects. The initial movements of HD subjects were less skilled (slower and/or less accurate) than those of control subjects. To factor out these differences in initial execution, we modeled the relationship between learning and baseline performance in control subjects. Subjects with HD exhibited a clear learning impairment that was not explained by differences in initial performance. These results support a role for the basal ganglia in both movement execution and motor skill learning. PMID:24312037

  17. Accurate Thermal Conductivities from First Principles

    NASA Astrophysics Data System (ADS)

    Carbogno, Christian

    2015-03-01

    In spite of significant research efforts, a first-principles determination of the thermal conductivity at high temperatures has remained elusive. On the one hand, Boltzmann transport techniques that include anharmonic effects in the nuclear dynamics only perturbatively become inaccurate or inapplicable under such conditions. On the other hand, non-equilibrium molecular dynamics (MD) methods suffer from enormous finite-size artifacts in the computationally feasible supercells, which prevent an accurate extrapolation to the bulk limit of the thermal conductivity. In this work, we overcome this limitation by performing ab initio MD simulations in thermodynamic equilibrium that account for all orders of anharmonicity. The thermal conductivity is then assessed from the auto-correlation function of the heat flux using the Green-Kubo formalism. Foremost, we discuss the fundamental theory underlying a first-principles definition of the heat flux using the virial theorem. We validate our approach and in particular the techniques developed to overcome finite time and size effects, e.g., by inspecting silicon, the thermal conductivity of which is particularly challenging to converge. Furthermore, we use this framework to investigate the thermal conductivity of ZrO2, which is known for its high degree of anharmonicity. Our calculations shed light on the heat resistance mechanism active in this material, which eventually allows us to discuss how the thermal conductivity can be controlled by doping and co-doping. This work has been performed in collaboration with R. Ramprasad (University of Connecticut), C. G. Levi and C. G. Van de Walle (University of California Santa Barbara).

  18. Accurately measuring dynamic coefficient of friction in ultraform finishing

    NASA Astrophysics Data System (ADS)

    Briggs, Dennis; Echaves, Samantha; Pidgeon, Brendan; Travis, Nathan; Ellis, Jonathan D.

    2013-09-01

    UltraForm Finishing (UFF) is a deterministic sub-aperture computer numerically controlled grinding and polishing platform designed by OptiPro Systems. UFF is used to grind and polish a variety of optics from simple spherical to fully freeform, and numerous materials from glasses to optical ceramics. The UFF system consists of an abrasive belt around a compliant wheel that rotates and contacts the part to remove material. This work aims to accurately measure the dynamic coefficient of friction (μ), how it changes as a function of belt wear, and how this ultimately affects material removal rates. The coefficient of friction has been examined in terms of contact mechanics and Preston's equation to determine accurate material removal rates. By accurately predicting changes in μ, polishing iterations can be more accurately predicted, reducing the total number of iterations required to meet specifications. We have established an experimental apparatus that can accurately measure μ by measuring triaxial forces during translating loading conditions or while manufacturing the removal spots used to calculate material removal rates. Using this system, we will demonstrate μ measurements for UFF belts during different states of their lifecycle and assess the material removal function from spot diagrams as a function of wear. Ultimately, we will use this system for qualifying belt-wheel-material combinations to develop a spot-morphing model to better predict instantaneous material removal functions.

  19. On the importance of having accurate data for astrophysical modelling

    NASA Astrophysics Data System (ADS)

    Lique, Francois

    2016-06-01

    The Herschel telescope and the ALMA and NOEMA interferometers have opened new windows of observation for wavelengths ranging from far infrared to sub-millimeter with spatial and spectral resolutions previously unmatched. To make the most of these observations, an accurate knowledge of the physical and chemical processes occurring in the interstellar and circumstellar media is essential.In this presentation, I will discuss what are the current needs of astrophysics in terms of molecular data and I will show that accurate molecular data are crucial for the proper determination of the physical conditions in molecular clouds.First, I will focus on collisional excitation studies that are needed for molecular lines modelling beyond the Local Thermodynamic Equilibrium (LTE) approach. In particular, I will show how new collisional data for the HCN and HNC isomers, two tracers of star forming conditions, have allowed solving the problem of their respective abundance in cold molecular clouds. I will also present the last collisional data that have been computed in order to analyse new highly resolved observations provided by the ALMA interferometer.Then, I will present the calculation of accurate rate constants for the F+H2 → HF+H and Cl+H2 ↔ HCl+H reactions, which have allowed a more accurate determination of the physical conditions in diffuse molecular clouds. I will also present the recent work on the ortho-para-H2 conversion due to hydrogen exchange that allow more accurate determination of the ortho-to-para-H2 ratio in the universe and that imply a significant revision of the cooling mechanism in astrophysical media.

  20. Mill profiler machines soft materials accurately

    NASA Technical Reports Server (NTRS)

    Rauschl, J. A.

    1966-01-01

    Mill profiler machines bevels, slots, and grooves in soft materials, such as styrofoam phenolic-filled cores, to any desired thickness. A single operator can accurately control cutting depths in contour or straight line work.

  1. SCB initiator

    DOEpatents

    Bickes, Jr., Robert W.; Renlund, Anita M.; Stanton, Philip L.

    1994-01-01

    A detonator for high explosives initiated by mechanical impact includes a cylindrical barrel, a layer of flyer material mechanically covering the barrel at one end, and a semiconductor bridge ignitor including a pair of electrically conductive pads connected by a semiconductor bridge. The bridge is in operational contact with the layer, whereby ignition of said bridge forces a portion of the layer through the barrel to detonate the explosive. Input means are provided for igniting the semiconductor bridge ignitor.

  2. SCB initiator

    DOEpatents

    Bickes Jr., Robert W.; Renlund, Anita M.; Stanton, Philip L.

    1994-11-01

    A detonator for high explosives initiated by mechanical impact includes a cylindrical barrel, a layer of flyer material mechanically covering the barrel at one end, and a semiconductor bridge ignitor including a pair of electrically conductive pads connected by a semiconductor bridge. The bridge is in operational contact with the layer, whereby ignition of said bridge forces a portion of the layer through the barrel to detonate the explosive. Input means are provided for igniting the semiconductor bridge ignitor.

  3. GlnR negatively regulates the transcription of the alanine dehydrogenase encoding gene ald in Amycolatopsis mediterranei U32 under nitrogen limited conditions via specific binding to its major transcription initiation site.

    PubMed

    Wang, Ying; Li, Chen; Duan, Na; Li, Bin; Ding, Xiao-Ming; Yao, Yu-Feng; Hu, Jun; Zhao, Guo-Ping; Wang, Jin

    2014-01-01

    Ammonium assimilation is catalyzed by two enzymatic pathways, i.e., glutamine synthetase/glutamate synthase (GS/GOGAT) and alanine dehydrogenase (AlaDH) in Amycolatopsis mediterranei U32. Under nitrogen-rich conditions, the AlaDH pathway is the major route for ammonium assimilation, while the GS/GOGAT pathway takes over when the extracellular nitrogen supply is limited. The global nitrogen regulator GlnR was previously characterized to activate the transcription of the GS encoding gene glnA in response to nitrogen limitation and is demonstrated in this study as a repressor for the transcription of the AlaDH encoding gene ald, whose regulation is consistent with the switch of the ammonium assimilation pathways from AlaDH to GS/GOGAT responding to nitrogen limitation. Three transcription initiation sites (TISs) of ald were determined with primer extension assay, among which transcription from aldP2 contributed the major transcripts under nitrogen-rich conditions but was repressed to an undetectable level in response to nitrogen limitation. Through DNase I footprinting assay, two separate regions were found to be protected by GlnR within ald promoter, within which three GlnR binding sites (a1, b1 sites in region I and a2 site in region II) were defined. Interestingly, the major TIS aldP2 is located in the middle of a2 site within region II. Therefore, one may easily conclude that GlnR represses the transcription of ald via specific binding to the GlnR binding sites, which obviously blocks the transcription initiation from aldP2 and therefore reduces ald transcripts.

  4. GlnR Negatively Regulates the Transcription of the Alanine Dehydrogenase Encoding Gene ald in Amycolatopsis mediterranei U32 under Nitrogen Limited Conditions via Specific Binding to Its Major Transcription Initiation Site

    PubMed Central

    Li, Bin; Ding, Xiao-Ming; Yao, Yu-Feng; Hu, Jun; Zhao, Guo-Ping; Wang, Jin

    2014-01-01

    Ammonium assimilation is catalyzed by two enzymatic pathways, i.e., glutamine synthetase/glutamate synthase (GS/GOGAT) and alanine dehydrogenase (AlaDH) in Amycolatopsis mediterranei U32. Under nitrogen-rich conditions, the AlaDH pathway is the major route for ammonium assimilation, while the GS/GOGAT pathway takes over when the extracellular nitrogen supply is limited. The global nitrogen regulator GlnR was previously characterized to activate the transcription of the GS encoding gene glnA in response to nitrogen limitation and is demonstrated in this study as a repressor for the transcription of the AlaDH encoding gene ald, whose regulation is consistent with the switch of the ammonium assimilation pathways from AlaDH to GS/GOGAT responding to nitrogen limitation. Three transcription initiation sites (TISs) of ald were determined with primer extension assay, among which transcription from aldP2 contributed the major transcripts under nitrogen-rich conditions but was repressed to an undetectable level in response to nitrogen limitation. Through DNase I footprinting assay, two separate regions were found to be protected by GlnR within ald promoter, within which three GlnR binding sites (a1, b1 sites in region I and a2 site in region II) were defined. Interestingly, the major TIS aldP2 is located in the middle of a2 site within region II. Therefore, one may easily conclude that GlnR represses the transcription of ald via specific binding to the GlnR binding sites, which obviously blocks the transcription initiation from aldP2 and therefore reduces ald transcripts. PMID:25144373

  5. An articulated statistical shape model for accurate hip joint segmentation.

    PubMed

    Kainmueller, Dagmar; Lamecker, Hans; Zachow, Stefan; Hege, Hans-Christian

    2009-01-01

    In this paper we propose a framework for fully automatic, robust and accurate segmentation of the human pelvis and proximal femur in CT data. We propose a composite statistical shape model of femur and pelvis with a flexible hip joint, for which we extend the common definition of statistical shape models as well as the common strategy for their adaptation. We do not analyze the joint flexibility statistically, but model it explicitly by rotational parameters describing the bent in a ball-and-socket joint. A leave-one-out evaluation on 50 CT volumes shows that image driven adaptation of our composite shape model robustly produces accurate segmentations of both proximal femur and pelvis. As a second contribution, we evaluate a fine grain multi-object segmentation method based on graph optimization. It relies on accurate initializations of femur and pelvis, which our composite shape model can generate. Simultaneous optimization of both femur and pelvis yields more accurate results than separate optimizations of each structure. Shape model adaptation and graph based optimization are embedded in a fully automatic framework. PMID:19964159

  6. Environmental initiatives

    SciTech Connect

    James, R.C. Jr.

    1991-11-01

    J I Case, a leading worldwide maker of agricultural and construction equipment based in Racine, Wisconsin, is taking an aggressive and responsible approach to environmental issues. From integrated solid waste handling plans and Freon recovery initiatives, to special employee training programs and voluntary participation in the EPA's Industrial Toxics Program, Case is addressing environmental issues at its facilities and in its products. One of the key environmental initiatives at Case is the company's voluntary participation in the US EPA's Industrial Toxics Program, also known as the 33/50 Program. This program is an EPA pollution prevention initiative started in 1990 that is designed to reduce industrial toxics generation quickly through voluntary actions by industry. The program derives its name from the EPA's national reduction goals for 17 high priority toxic pollutants - 33 percent reduction by 1992 and 50 percent by 1995. As a result, the Pryor Foundry has slashed its emissions of industrial toxic pollutants by 98 percent, from over 350,000 pounds (159 metric tons) in 1988 to around 5,000 pounds (2.27 metric tons) in 1991, with a projected reduction to only 750 pounds (340 kilograms) by 1995.

  7. Accurate modeling of switched reluctance machine based on hybrid trained WNN

    SciTech Connect

    Song, Shoujun Ge, Lefei; Ma, Shaojie; Zhang, Man

    2014-04-15

    According to the strong nonlinear electromagnetic characteristics of switched reluctance machine (SRM), a novel accurate modeling method is proposed based on hybrid trained wavelet neural network (WNN) which combines improved genetic algorithm (GA) with gradient descent (GD) method to train the network. In the novel method, WNN is trained by GD method based on the initial weights obtained per improved GA optimization, and the global parallel searching capability of stochastic algorithm and local convergence speed of deterministic algorithm are combined to enhance the training accuracy, stability and speed. Based on the measured electromagnetic characteristics of a 3-phase 12/8-pole SRM, the nonlinear simulation model is built by hybrid trained WNN in Matlab. The phase current and mechanical characteristics from simulation under different working conditions meet well with those from experiments, which indicates the accuracy of the model for dynamic and static performance evaluation of SRM and verifies the effectiveness of the proposed modeling method.

  8. Accurate modeling of switched reluctance machine based on hybrid trained WNN

    NASA Astrophysics Data System (ADS)

    Song, Shoujun; Ge, Lefei; Ma, Shaojie; Zhang, Man

    2014-04-01

    According to the strong nonlinear electromagnetic characteristics of switched reluctance machine (SRM), a novel accurate modeling method is proposed based on hybrid trained wavelet neural network (WNN) which combines improved genetic algorithm (GA) with gradient descent (GD) method to train the network. In the novel method, WNN is trained by GD method based on the initial weights obtained per improved GA optimization, and the global parallel searching capability of stochastic algorithm and local convergence speed of deterministic algorithm are combined to enhance the training accuracy, stability and speed. Based on the measured electromagnetic characteristics of a 3-phase 12/8-pole SRM, the nonlinear simulation model is built by hybrid trained WNN in Matlab. The phase current and mechanical characteristics from simulation under different working conditions meet well with those from experiments, which indicates the accuracy of the model for dynamic and static performance evaluation of SRM and verifies the effectiveness of the proposed modeling method.

  9. Library preparation for highly accurate population sequencing of RNA viruses

    PubMed Central

    Acevedo, Ashley; Andino, Raul

    2015-01-01

    Circular resequencing (CirSeq) is a novel technique for efficient and highly accurate next-generation sequencing (NGS) of RNA virus populations. The foundation of this approach is the circularization of fragmented viral RNAs, which are then redundantly encoded into tandem repeats by ‘rolling-circle’ reverse transcription. When sequenced, the redundant copies within each read are aligned to derive a consensus sequence of their initial RNA template. This process yields sequencing data with error rates far below the variant frequencies observed for RNA viruses, facilitating ultra-rare variant detection and accurate measurement of low-frequency variants. Although library preparation takes ~5 d, the high-quality data generated by CirSeq simplifies downstream data analysis, making this approach substantially more tractable for experimentalists. PMID:24967624

  10. Uniformly high order accurate essentially non-oscillatory schemes 3

    NASA Technical Reports Server (NTRS)

    Harten, A.; Engquist, B.; Osher, S.; Chakravarthy, S. R.

    1986-01-01

    In this paper (a third in a series) the construction and the analysis of essentially non-oscillatory shock capturing methods for the approximation of hyperbolic conservation laws are presented. Also presented is a hierarchy of high order accurate schemes which generalizes Godunov's scheme and its second order accurate MUSCL extension to arbitrary order of accuracy. The design involves an essentially non-oscillatory piecewise polynomial reconstruction of the solution from its cell averages, time evolution through an approximate solution of the resulting initial value problem, and averaging of this approximate solution over each cell. The reconstruction algorithm is derived from a new interpolation technique that when applied to piecewise smooth data gives high-order accuracy whenever the function is smooth but avoids a Gibbs phenomenon at discontinuities. Unlike standard finite difference methods this procedure uses an adaptive stencil of grid points and consequently the resulting schemes are highly nonlinear.

  11. Solution of the surface Euler equations for accurate three-dimensional boundary-layer analysis of aerodynamic configurations

    NASA Technical Reports Server (NTRS)

    Iyer, V.; Harris, J. E.

    1987-01-01

    The three-dimensional boundary-layer equations in the limit as the normal coordinate tends to infinity are called the surface Euler equations. The present paper describes an accurate method for generating edge conditions for three-dimensional boundary-layer codes using these equations. The inviscid pressure distribution is first interpolated to the boundary-layer grid. The surface Euler equations are then solved with this pressure field and a prescribed set of initial and boundary conditions to yield the velocities along the two surface coordinate directions. Results for typical wing and fuselage geometries are presented. The smoothness and accuracy of the edge conditions obtained are found to be superior to the conventional interpolation procedures.

  12. Accurate thermoelastic tensor and acoustic velocities of NaCl

    NASA Astrophysics Data System (ADS)

    Marcondes, Michel L.; Shukla, Gaurav; da Silveira, Pedro; Wentzcovitch, Renata M.

    2015-12-01

    Despite the importance of thermoelastic properties of minerals in geology and geophysics, their measurement at high pressures and temperatures are still challenging. Thus, ab initio calculations are an essential tool for predicting these properties at extreme conditions. Owing to the approximate description of the exchange-correlation energy, approximations used in calculations of vibrational effects, and numerical/methodological approximations, these methods produce systematic deviations. Hybrid schemes combining experimental data and theoretical results have emerged as a way to reconcile available information and offer more reliable predictions at experimentally inaccessible thermodynamics conditions. Here we introduce a method to improve the calculated thermoelastic tensor by using highly accurate thermal equation of state (EoS). The corrective scheme is general, applicable to crystalline solids with any symmetry, and can produce accurate results at conditions where experimental data may not exist. We apply it to rock-salt-type NaCl, a material whose structural properties have been challenging to describe accurately by standard ab initio methods and whose acoustic/seismic properties are important for the gas and oil industry.

  13. Accurate thermoelastic tensor and acoustic velocities of NaCl

    SciTech Connect

    Marcondes, Michel L.; Shukla, Gaurav; Silveira, Pedro da; Wentzcovitch, Renata M.

    2015-12-15

    Despite the importance of thermoelastic properties of minerals in geology and geophysics, their measurement at high pressures and temperatures are still challenging. Thus, ab initio calculations are an essential tool for predicting these properties at extreme conditions. Owing to the approximate description of the exchange-correlation energy, approximations used in calculations of vibrational effects, and numerical/methodological approximations, these methods produce systematic deviations. Hybrid schemes combining experimental data and theoretical results have emerged as a way to reconcile available information and offer more reliable predictions at experimentally inaccessible thermodynamics conditions. Here we introduce a method to improve the calculated thermoelastic tensor by using highly accurate thermal equation of state (EoS). The corrective scheme is general, applicable to crystalline solids with any symmetry, and can produce accurate results at conditions where experimental data may not exist. We apply it to rock-salt-type NaCl, a material whose structural properties have been challenging to describe accurately by standard ab initio methods and whose acoustic/seismic properties are important for the gas and oil industry.

  14. Accurate evaluation of homogenous and nonhomogeneous gas emissivities

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.; Lee, K. P.

    1984-01-01

    Spectral transmittance and total band adsorptance of selected infrared bands of carbon dioxide and water vapor are calculated by using the line-by-line and quasi-random band models and these are compared with available experimental results to establish the validity of the quasi-random band model. Various wide-band model correlations are employed to calculate the total band absorptance and total emissivity of these two gases under homogeneous and nonhomogeneous conditions. These results are compared with available experimental results under identical conditions. From these comparisons, it is found that the quasi-random band model can provide quite accurate results and is quite suitable for most atmospheric applications.

  15. Modified chemiluminescent NO analyzer accurately measures NOX

    NASA Technical Reports Server (NTRS)

    Summers, R. L.

    1978-01-01

    Installation of molybdenum nitric oxide (NO)-to-higher oxides of nitrogen (NOx) converter in chemiluminescent gas analyzer and use of air purge allow accurate measurements of NOx in exhaust gases containing as much as thirty percent carbon monoxide (CO). Measurements using conventional analyzer are highly inaccurate for NOx if as little as five percent CO is present. In modified analyzer, molybdenum has high tolerance to CO, and air purge substantially quenches NOx destruction. In test, modified chemiluminescent analyzer accurately measured NO and NOx concentrations for over 4 months with no denegration in performance.

  16. Can Appraisers Rate Work Performance Accurately?

    ERIC Educational Resources Information Center

    Hedge, Jerry W.; Laue, Frances J.

    The ability of individuals to make accurate judgments about others is examined and literature on this subject is reviewed. A wide variety of situational factors affects the appraisal of performance. It is generally accepted that the purpose of the appraisal influences the accuracy of the appraiser. The instrumentation, or tools, available to the…

  17. Accurate pointing of tungsten welding electrodes

    NASA Technical Reports Server (NTRS)

    Ziegelmeier, P.

    1971-01-01

    Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.

  18. Openness initiative

    SciTech Connect

    Duncan, S.S.

    1995-12-31

    Although antinuclear campaigns seem to be effective, public communication and education efforts on low-level radioactive waste have mixed results. Attempts at public information programs on low-level radioactive waste still focus on influencing public opinion. A question then is: {open_quotes}Is it preferable to have a program focus on public education that will empower individuals to make informed decisions rather than trying to influence them in their decisions?{close_quotes} To address this question, a case study with both quantitative and qualitative data will be used. The Ohio Low-Level Radioactive Waste Education Program has a goal to provide people with information they want/need to make their own decisions. The program initiated its efforts by conducting a statewide survey to determine information needed by people and where they turned for that information. This presentation reports data from the survey and then explores the program development process in which programs were designed and presented using the information. Pre and post data from the programs reveal attitude and knowledge shifts.

  19. Accurate and occlusion-robust multi-view stereo

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaokun; Stamatopoulos, Christos; Fraser, Clive S.

    2015-11-01

    This paper proposes an accurate multi-view stereo method for image-based 3D reconstruction that features robustness in the presence of occlusions. The new method offers improvements in dealing with two fundamental image matching problems. The first concerns the selection of the support window model, while the second centers upon accurate visibility estimation for each pixel. The support window model is based on an approximate 3D support plane described by a depth and two per-pixel depth offsets. For the visibility estimation, the multi-view constraint is initially relaxed by generating separate support plane maps for each support image using a modified PatchMatch algorithm. Then the most likely visible support image, which represents the minimum visibility of each pixel, is extracted via a discrete Markov Random Field model and it is further augmented by parameter clustering. Once the visibility is estimated, multi-view optimization taking into account all redundant observations is conducted to achieve optimal accuracy in the 3D surface generation for both depth and surface normal estimates. Finally, multi-view consistency is utilized to eliminate any remaining observational outliers. The proposed method is experimentally evaluated using well-known Middlebury datasets, and results obtained demonstrate that it is amongst the most accurate of the methods thus far reported via the Middlebury MVS website. Moreover, the new method exhibits a high completeness rate.

  20. Feedback about More Accurate versus Less Accurate Trials: Differential Effects on Self-Confidence and Activation

    ERIC Educational Resources Information Center

    Badami, Rokhsareh; VaezMousavi, Mohammad; Wulf, Gabriele; Namazizadeh, Mahdi

    2012-01-01

    One purpose of the present study was to examine whether self-confidence or anxiety would be differentially affected by feedback from more accurate rather than less accurate trials. The second purpose was to determine whether arousal variations (activation) would predict performance. On Day 1, participants performed a golf putting task under one of…

  1. Two highly accurate methods for pitch calibration

    NASA Astrophysics Data System (ADS)

    Kniel, K.; Härtig, F.; Osawa, S.; Sato, O.

    2009-11-01

    Among profiles, helix and tooth thickness pitch is one of the most important parameters of an involute gear measurement evaluation. In principle, coordinate measuring machines (CMM) and CNC-controlled gear measuring machines as a variant of a CMM are suited for these kinds of gear measurements. Now the Japan National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) and the German national metrology institute the Physikalisch-Technische Bundesanstalt (PTB) have each developed independently highly accurate pitch calibration methods applicable to CMM or gear measuring machines. Both calibration methods are based on the so-called closure technique which allows the separation of the systematic errors of the measurement device and the errors of the gear. For the verification of both calibration methods, NMIJ/AIST and PTB performed measurements on a specially designed pitch artifact. The comparison of the results shows that both methods can be used for highly accurate calibrations of pitch standards.

  2. Preparation and accurate measurement of pure ozone.

    PubMed

    Janssen, Christof; Simone, Daniela; Guinet, Mickaël

    2011-03-01

    Preparation of high purity ozone as well as precise and accurate measurement of its pressure are metrological requirements that are difficult to meet due to ozone decomposition occurring in pressure sensors. The most stable and precise transducer heads are heated and, therefore, prone to accelerated ozone decomposition, limiting measurement accuracy and compromising purity. Here, we describe a vacuum system and a method for ozone production, suitable to accurately determine the pressure of pure ozone by avoiding the problem of decomposition. We use an inert gas in a particularly designed buffer volume and can thus achieve high measurement accuracy and negligible degradation of ozone with purities of 99.8% or better. The high degree of purity is ensured by comprehensive compositional analyses of ozone samples. The method may also be applied to other reactive gases. PMID:21456766

  3. Accurate modeling of parallel scientific computations

    NASA Technical Reports Server (NTRS)

    Nicol, David M.; Townsend, James C.

    1988-01-01

    Scientific codes are usually parallelized by partitioning a grid among processors. To achieve top performance it is necessary to partition the grid so as to balance workload and minimize communication/synchronization costs. This problem is particularly acute when the grid is irregular, changes over the course of the computation, and is not known until load time. Critical mapping and remapping decisions rest on the ability to accurately predict performance, given a description of a grid and its partition. This paper discusses one approach to this problem, and illustrates its use on a one-dimensional fluids code. The models constructed are shown to be accurate, and are used to find optimal remapping schedules.

  4. Line gas sampling system ensures accurate analysis

    SciTech Connect

    Not Available

    1992-06-01

    Tremendous changes in the natural gas business have resulted in new approaches to the way natural gas is measured. Electronic flow measurement has altered the business forever, with developments in instrumentation and a new sensitivity to the importance of proper natural gas sampling techniques. This paper reports that YZ Industries Inc., Snyder, Texas, combined its 40 years of sampling experience with the latest in microprocessor-based technology to develop the KynaPak 2000 series, the first on-line natural gas sampling system that is both compact and extremely accurate. This means the composition of the sampled gas must be representative of the whole and related to flow. If so, relative measurement and sampling techniques are married, gas volumes are accurately accounted for and adjustments to composition can be made.

  5. Accurate mask model for advanced nodes

    NASA Astrophysics Data System (ADS)

    Zine El Abidine, Nacer; Sundermann, Frank; Yesilada, Emek; Ndiaye, El Hadji Omar; Mishra, Kushlendra; Paninjath, Sankaranarayanan; Bork, Ingo; Buck, Peter; Toublan, Olivier; Schanen, Isabelle

    2014-07-01

    Standard OPC models consist of a physical optical model and an empirical resist model. The resist model compensates the optical model imprecision on top of modeling resist development. The optical model imprecision may result from mask topography effects and real mask information including mask ebeam writing and mask process contributions. For advanced technology nodes, significant progress has been made to model mask topography to improve optical model accuracy. However, mask information is difficult to decorrelate from standard OPC model. Our goal is to establish an accurate mask model through a dedicated calibration exercise. In this paper, we present a flow to calibrate an accurate mask enabling its implementation. The study covers the different effects that should be embedded in the mask model as well as the experiment required to model them.

  6. Microdrill Initiative - Initial Market Evaluation

    SciTech Connect

    Spears & Associates, Inc

    2003-07-01

    The U.S. Department of Energy (DOE) is launching a major research and development initiative to create a small, fast, inexpensive and environmentally friendly rig for drilling 5000 feet boreholes to investigate potential oil and gas reservoirs. DOE wishes to get input from petroleum industry operators, service companies and equipment suppliers on the operation and application of this coiled-tubing-based drilling unit. To that end, DOE has asked Spears & Associates, Inc. (SAI) to prepare a special state-of-the-market report and assist during a DOE-sponsored project-scoping workshop in Albuquerque near the end of April 2003. The scope of the project is four-fold: (1) Evaluate the history, status and future of demand for very small bore-hole drilling; (2) Measure the market for coiled tubing drilling and describe the state-of-the-art; (3) Identify companies and individuals who should have an interest in micro drilling and invite them to the DOE workshop; and (4) Participate in 3 concurrent workshop sessions, record and evaluate participant comments and report workshop conclusions.

  7. Accurate maser positions for MALT-45

    NASA Astrophysics Data System (ADS)

    Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven

    2013-10-01

    MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.

  8. Accurate maser positions for MALT-45

    NASA Astrophysics Data System (ADS)

    Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven

    2013-04-01

    MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.

  9. Accurate Molecular Polarizabilities Based on Continuum Electrostatics

    PubMed Central

    Truchon, Jean-François; Nicholls, Anthony; Iftimie, Radu I.; Roux, Benoît; Bayly, Christopher I.

    2013-01-01

    A novel approach for representing the intramolecular polarizability as a continuum dielectric is introduced to account for molecular electronic polarization. It is shown, using a finite-difference solution to the Poisson equation, that the Electronic Polarization from Internal Continuum (EPIC) model yields accurate gas-phase molecular polarizability tensors for a test set of 98 challenging molecules composed of heteroaromatics, alkanes and diatomics. The electronic polarization originates from a high intramolecular dielectric that produces polarizabilities consistent with B3LYP/aug-cc-pVTZ and experimental values when surrounded by vacuum dielectric. In contrast to other approaches to model electronic polarization, this simple model avoids the polarizability catastrophe and accurately calculates molecular anisotropy with the use of very few fitted parameters and without resorting to auxiliary sites or anisotropic atomic centers. On average, the unsigned error in the average polarizability and anisotropy compared to B3LYP are 2% and 5%, respectively. The correlation between the polarizability components from B3LYP and this approach lead to a R2 of 0.990 and a slope of 0.999. Even the F2 anisotropy, shown to be a difficult case for existing polarizability models, can be reproduced within 2% error. In addition to providing new parameters for a rapid method directly applicable to the calculation of polarizabilities, this work extends the widely used Poisson equation to areas where accurate molecular polarizabilities matter. PMID:23646034

  10. Accurate phase-shift velocimetry in rock.

    PubMed

    Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M

    2016-06-01

    Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models. PMID:27111139

  11. Accurate phase-shift velocimetry in rock

    NASA Astrophysics Data System (ADS)

    Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R.; Holmes, William M.

    2016-06-01

    Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.

  12. Accurate phase-shift velocimetry in rock.

    PubMed

    Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M

    2016-06-01

    Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.

  13. High Frequency QRS ECG Accurately Detects Cardiomyopathy

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds

    2005-01-01

    High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing

  14. Accurate fluorescence quantum yield determination by fluorescence correlation spectroscopy.

    PubMed

    Kempe, Daryan; Schöne, Antonie; Fitter, Jörg; Gabba, Matteo

    2015-04-01

    Here, we present a comparative method for the accurate determination of fluorescence quantum yields (QYs) by fluorescence correlation spectroscopy. By exploiting the high sensitivity of single-molecule spectroscopy, we obtain the QYs of samples in the microliter range and at (sub)nanomolar concentrations. Additionally, in combination with fluorescence lifetime measurements, our method allows the quantification of both static and collisional quenching constants. Thus, besides being simple and fast, our method opens up the possibility to photophysically characterize labeled biomolecules under application-relevant conditions and with low sample consumption, which is often important in single-molecule studies.

  15. Accurately Mapping M31's Microlensing Population

    NASA Astrophysics Data System (ADS)

    Crotts, Arlin

    2004-07-01

    We propose to augment an existing microlensing survey of M31 with source identifications provided by a modest amount of ACS {and WFPC2 parallel} observations to yield an accurate measurement of the masses responsible for microlensing in M31, and presumably much of its dark matter. The main benefit of these data is the determination of the physical {or "einstein"} timescale of each microlensing event, rather than an effective {"FWHM"} timescale, allowing masses to be determined more than twice as accurately as without HST data. The einstein timescale is the ratio of the lensing cross-sectional radius and relative velocities. Velocities are known from kinematics, and the cross-section is directly proportional to the {unknown} lensing mass. We cannot easily measure these quantities without knowing the amplification, hence the baseline magnitude, which requires the resolution of HST to find the source star. This makes a crucial difference because M31 lens m ass determinations can be more accurate than those towards the Magellanic Clouds through our Galaxy's halo {for the same number of microlensing events} due to the better constrained geometry in the M31 microlensing situation. Furthermore, our larger survey, just completed, should yield at least 100 M31 microlensing events, more than any Magellanic survey. A small amount of ACS+WFPC2 imaging will deliver the potential of this large database {about 350 nights}. For the whole survey {and a delta-function mass distribution} the mass error should approach only about 15%, or about 6% error in slope for a power-law distribution. These results will better allow us to pinpoint the lens halo fraction, and the shape of the halo lens spatial distribution, and allow generalization/comparison of the nature of halo dark matter in spiral galaxies. In addition, we will be able to establish the baseline magnitude for about 50, 000 variable stars, as well as measure an unprecedentedly deta iled color-magnitude diagram and luminosity

  16. Accurate measurement of unsteady state fluid temperature

    NASA Astrophysics Data System (ADS)

    Jaremkiewicz, Magdalena

    2016-07-01

    In this paper, two accurate methods for determining the transient fluid temperature were presented. Measurements were conducted for boiling water since its temperature is known. At the beginning the thermometers are at the ambient temperature and next they are immediately immersed into saturated water. The measurements were carried out with two thermometers of different construction but with the same housing outer diameter equal to 15 mm. One of them is a K-type industrial thermometer widely available commercially. The temperature indicated by the thermometer was corrected considering the thermometers as the first or second order inertia devices. The new design of a thermometer was proposed and also used to measure the temperature of boiling water. Its characteristic feature is a cylinder-shaped housing with the sheath thermocouple located in its center. The temperature of the fluid was determined based on measurements taken in the axis of the solid cylindrical element (housing) using the inverse space marching method. Measurements of the transient temperature of the air flowing through the wind tunnel using the same thermometers were also carried out. The proposed measurement technique provides more accurate results compared with measurements using industrial thermometers in conjunction with simple temperature correction using the inertial thermometer model of the first or second order. By comparing the results, it was demonstrated that the new thermometer allows obtaining the fluid temperature much faster and with higher accuracy in comparison to the industrial thermometer. Accurate measurements of the fast changing fluid temperature are possible due to the low inertia thermometer and fast space marching method applied for solving the inverse heat conduction problem.

  17. The first accurate description of an aurora

    NASA Astrophysics Data System (ADS)

    Schröder, Wilfried

    2006-12-01

    As technology has advanced, the scientific study of auroral phenomena has increased by leaps and bounds. A look back at the earliest descriptions of aurorae offers an interesting look into how medieval scholars viewed the subjects that we study.Although there are earlier fragmentary references in the literature, the first accurate description of the aurora borealis appears to be that published by the German Catholic scholar Konrad von Megenberg (1309-1374) in his book Das Buch der Natur (The Book of Nature). The book was written between 1349 and 1350.

  18. New law requires 'medically accurate' lesson plans.

    PubMed

    1999-09-17

    The California Legislature has passed a bill requiring all textbooks and materials used to teach about AIDS be medically accurate and objective. Statements made within the curriculum must be supported by research conducted in compliance with scientific methods, and published in peer-reviewed journals. Some of the current lesson plans were found to contain scientifically unsupported and biased information. In addition, the bill requires material to be "free of racial, ethnic, or gender biases." The legislation is supported by a wide range of interests, but opposed by the California Right to Life Education Fund, because they believe it discredits abstinence-only material.

  19. Accurate density functional thermochemistry for larger molecules.

    SciTech Connect

    Raghavachari, K.; Stefanov, B. B.; Curtiss, L. A.; Lucent Tech.

    1997-06-20

    Density functional methods are combined with isodesmic bond separation reaction energies to yield accurate thermochemistry for larger molecules. Seven different density functionals are assessed for the evaluation of heats of formation, Delta H 0 (298 K), for a test set of 40 molecules composed of H, C, O and N. The use of bond separation energies results in a dramatic improvement in the accuracy of all the density functionals. The B3-LYP functional has the smallest mean absolute deviation from experiment (1.5 kcal mol/f).

  20. New law requires 'medically accurate' lesson plans.

    PubMed

    1999-09-17

    The California Legislature has passed a bill requiring all textbooks and materials used to teach about AIDS be medically accurate and objective. Statements made within the curriculum must be supported by research conducted in compliance with scientific methods, and published in peer-reviewed journals. Some of the current lesson plans were found to contain scientifically unsupported and biased information. In addition, the bill requires material to be "free of racial, ethnic, or gender biases." The legislation is supported by a wide range of interests, but opposed by the California Right to Life Education Fund, because they believe it discredits abstinence-only material. PMID:11366835