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.
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
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.
New Claus catalyst tests accurately reflect process conditions
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.
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.
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).
Hydrodynamics from Landau initial conditions
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
A Self-Instructional Device for Conditioning Accurate Prosody.
ERIC Educational Resources Information Center
Buiten, Roger; Lane, Harlan
1965-01-01
A self-instructional device for conditioning accurate prosody in second-language learning is described in this article. The Speech Auto-Instructional Device (SAID) is electro-mechanical and performs three functions: SAID (1) presents to the student tape-recorded pattern sentences that are considered standards in prosodic performance; (2) processes…
Critical Conditions for Rill Initiation
Technology Transfer Automated Retrieval System (TEKTRAN)
Quantifying critical conditions of rill formation can be useful for a better understanding of soil erosion processes. Current studies lack a consensus and related rationale on how to describe these conditions. This study was based on the concepts that: (1) the flow shear stress available for erosio...
Initial conditions and sampling for multifield inflation
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.
Accurate Orientation Estimation Using AHRS under Conditions of Magnetic Distortion
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
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.
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.
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.
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.
Crack initiation under generalized plane strain conditions
Shum, D.K.M.; Merkle, J.G.
1991-01-01
A method for estimating the decrease in crack-initiation toughness, from a reference plane strain value, due to positive straining along the crack front of a circumferential flaw in a reactor pressure vessel is presented in this study. This method relates crack initiation under generalized plane strain conditions with material failure at points within a distance of a few crack-tip-opening displacements ahead of a crack front, and involves the formulation of a micromechanical crack-initiation model. While this study is intended to address concerns regarding the effects of positive out-of- plane straining on ductile crack initiation, the approach adopted in this work can be extended in a straightforward fashion to examine conditions of macroscopic cleavage crack initiation. Provided single- parameter dominance of near-tip fields exists in the flawed structure, results from this study could be used to examine the appropriateness of applying plane strain fracture toughness to the evaluation of circumferential flaws, in particular to those in ring-forged vessels which have no longitudinal welds. In addition, results from this study could also be applied toward the analysis of the effects of thermal streaming on the fracture resistance of circumferentially oriented flaws in a pressure vessel. 37 refs., 8 figs., 1 tab.
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.
Initial models in conditionals: evidence from priming.
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. PMID:18630646
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.
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.
Initial condition of stochastic self-assembly.
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. PMID:26986290
Accurate initiation by RNA polymerase II in a whole cell extract from Saccharomyces cerevisiae.
Woontner, M; Jaehning, J A
1990-06-01
We have developed a simple procedure for isolating a transcriptional extract from whole yeast cells which obviates the requirement for nuclear isolation. Detection of accurate mRNA initiation by RNA polymerase II in the extract requires the use of a sensitive assay, recently described by Kornberg and co-workers (Lue, N. F., Flanagan, P. M., Sugimoto, K., and Kornberg, R. D. (1989) Science 246, 661-664) that involves activation by a GAL4-VP16 fusion protein and a template lacking guanosine residues in the coding strand. The extract is prepared from fresh or frozen yeast cells by disruption with glass beads and fractionation of proteins by ammonium sulfate precipitation. The alpha-amanitin-sensitive transcripts synthesized in the assay were identical to those produced in a parallel assay using a yeast nuclear extract. The activity of the whole cell extract is lower per mg of protein than a nuclear extract but proportional to the volume of the nucleus relative to the whole cell. The optimal ranges for several reaction components including template, mono- and divalent cations, and nucleotide substrate concentration were determined. Under optimal conditions the whole cell extract produced a maximum of approximately 1 X 10(-2) transcripts/template molecule in 30 min. PMID:2188968
Cosmological attractors and initial conditions for inflation
NASA Astrophysics Data System (ADS)
Carrasco, John Joseph M.; Kallosh, Renata; Linde, Andrei
2015-09-01
Inflationary α -attractor models in supergravity, which provide excellent fits to the latest observational data, are based on the Poincaré disk hyperbolic geometry. We refine these models by constructing Kähler potentials with built-in inflaton shift symmetry and by making a canonical choice of the Goldstino Kähler potential. The refined models are stable with respect to all scalar fields at all α ; no additional stabilization terms are required. The scalar potential V has a nearly Minkowski minimum at small values of the inflaton field φ and an infinitely long de Sitter (dS) valley of constant depth and width at large φ . Because of the infinite length of this shift-symmetric valley, the initial value of the inflaton field at the Planck density is expected to be extremely large. We show that the inflaton field φ does not change much until all fields lose their energy and fall to the bottom of the dS valley at large φ . This provides natural initial conditions for inflation driven by the inflaton field slowly rolling along the dS valley toward the minimum of the potential at small φ . A detailed description of this process is given for α -attractors in supergravity, but we believe that our general conclusions concerning naturalness of initial conditions for inflation are valid for a broad class of inflationary models with sufficiently flat potentials.
Initial conditioning of the TFTR vacuum vessel
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.
Initial conditions of radiative shock experiments
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.
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.
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.
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.
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.
Accurate label-free reaction kinetics determination using initial rate heat measurements
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
The problem of initial conditions in cosmology
NASA Astrophysics Data System (ADS)
Barvinsky, A. O.; Kamenshchik, A. Yu.
2009-05-01
The creation of a quantum Universe is described by a density matrix which yields an ensemble of universes with the cosmological constant limited to a bounded range Λmin<=Λ<=Λmax. The domain Λ<Λmin is ruled out by a cosmological bootstrap requirement (the self-consistent back reaction of hot matter). The upper cutoff results from the quantum effects of vacuum energy and the conformal anomaly mediated by a special ghost-avoidance renormalization. The cutoff Λmax establishes a new quantum scale-the accumulation point of an infinite sequence of garland-type instantons. The Euclidean path integral formalism used for the construction of the fundamental density matrix for a mixed state of the Universe is justified by proving its correspondence to the microcanonical ensemble in quantum cosmology. The cosmological evolution starting with these initial conditions also have some new features: the stage of cosmic acceleration can be followed by a big boost singularity-a rapid growth up to infinity of the scale factor acceleration parameter. From the developed approach it follows that the notion of the density matrix plays a more fundamental role than that was traditionally prescribed to it.
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…
Experiments on initial and boundary conditions
NASA Technical Reports Server (NTRS)
Moretti, G.
1980-01-01
Effects of three different models for the treatment of subsonic boundary conditions, applied to the problem of flow in a channel with a bump, are discussed. A preliminary discussion of the numerical treatment of the corners is presented.
Initial conditions in high-energy collisions
NASA Astrophysics Data System (ADS)
Petreska, Elena
This thesis is focused on the initial stages of high-energy collisions in the saturation regime. We start by extending the McLerran-Venugopalan distribution of color sources in the initial wave-function of nuclei in heavy-ion collisions. We derive a fourth-order operator in the action and discuss its relevance for the description of color charge distributions in protons in high-energy experiments. We calculate the dipole scattering amplitude in proton-proton collisions with the quartic action and find an agreement with experimental data. We also obtain a modification to the fluctuation parameter of the negative binomial distribution of particle multiplicities in proton-proton experiments. The result implies an advancement of the fourth-order action towards Gaussian when the energy is increased. Finally, we calculate perturbatively the expectation value of the magnetic Wilson loop operator in the first moments of heavy-ion collisions. For the magnetic flux we obtain a first non-trivial term that is proportional to the square of the area of the loop. The result is close to numerical calculations for small area loops.
Bi-fluorescence imaging for estimating accurately the nuclear condition of Rhizoctonia spp.
Technology Transfer Automated Retrieval System (TEKTRAN)
Aims: To simplify the determination of the nuclear condition of the pathogenic Rhizoctonia, which currently needs to be performed either using two fluorescent dyes, thus is more costly and time-consuming, or using only one fluorescent dye, and thus less accurate. Methods and Results: A red primary ...
NASA Astrophysics Data System (ADS)
Marquis, G. A.; Roy, A. G.
2012-12-01
set with a bed activity survey. We surveyed the presence/absence of tags inserted every meter into the bed surface layer upstream of the cross sections where the bedload traps were installed. The initial threshold for motion at Béard Creek is strongly dependant on the initial bed conditions such as the bed roughness and the local bed slope but also on the morphological trajectory of the sections, i.e. the mean elevation changes and the area over which the bed sediments were mobilised. For example, if the bed was mobilised over an extensive area, the initial threshold for motion decreases, which is probably due to the low level of organisation of freshly mobilised particles. These results show that the study of the temporal variations of the initial threshold for motion allows us to link bedload processes to morphological changes but also stresses the importance of past and current bed conditions in determining future morphological changes. Using initial conditions and previous changes, it could be possible to estimate more accurate value of the local initial threshold for motion at a specific time for a reach and probably increase the performance of bedload transport predictions.
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.
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.
ATMOSPHERIC CIRCULATION OF HOT JUPITERS: INSENSITIVITY TO INITIAL CONDITIONS
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.
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.
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.
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.
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.
Initial capacity conditioning on electrochemical nickel hydroxide electrodes
NASA Technical Reports Server (NTRS)
Fritts, D. H.
1981-01-01
Conditioning is the initial cycling where cell capacity is usually unstable. The causes of the initial capacity build were examined. Gridless electrodes were fabricated to ensure mechanical homogeneity, so that a strain measured in one direction would be typical of a strain measured in the other directions. Plate hardness was also determined. These two parameters stabilize together.
Impacts of initial conditions on monsoon intraseasonal forecasting
NASA Astrophysics Data System (ADS)
Fu, Xiouhua; Wang, Bin; Bao, Qing; Liu, Ping; Lee, June-Yi
2009-04-01
Sensitivity of monsoon intraseasonal forecasting to different initial conditions is examined with the University of Hawaii Hybrid Coupled Model (UH_HCM). The target period is May to September 2004. We found that in the NCEP reanalysis the amplitudes of the convective activities associated with monsoon intraseasonal oscillation (MISO) are smaller than the observed counterparts by a factor of two to three. Motivated by this fact, we carried out a suite of forecasting experiments to explore the impacts of initial conditions on intraseasonal forecast skills. Our results reveal that with the original NCEP reanalysis as initial conditions the monsoon intraseasonal forecast skills of 850-hPa zonal winds and rainfall are only about a week over the global tropics (30°S-30°N) and Southeast Asia (10°N-30°N, 60°E-120°E). The predictability increases steadily with increased amplitudes of MISO in the initial conditions. When the MISO signals in initial conditions are recovered to a level similar to that in the observations, monsoon intraseasonal forecast skills reach 25 days for 850-hPa zonal winds and 15 days for rainfall over both the global tropics and Southeast Asia. It is also found that high-frequency weather in initial conditions generally extends rainfall predictability by about 5 days.
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
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
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.
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.
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.
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.
Fluctuating Glasma Initial Conditions and Flow in Heavy Ion Collisions
NASA Astrophysics Data System (ADS)
Schenke, Björn; Tribedy, Prithwish; Venugopalan, Raju
2012-06-01
We compute initial conditions in heavy ion collisions within the color glass condensate framework by combining the impact parameter dependent saturation model with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this impact parameter dependent Glasma description includes quantum fluctuations of color charges on the length scale determined by the inverse nuclear saturation scale Qs. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity ɛ3/ɛ2 is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and v2,3,4(pT) of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution.
Fluctuating glasma initial conditions and flow in heavy ion collisions.
Schenke, Björn; Tribedy, Prithwish; Venugopalan, Raju
2012-06-22
We compute initial conditions in heavy ion collisions within the color glass condensate framework by combining the impact parameter dependent saturation model with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this impact parameter dependent Glasma description includes quantum fluctuations of color charges on the length scale determined by the inverse nuclear saturation scale Q(s). The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity ε(3)/ε(2) is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and v(2,3,4)(p(T)) of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution. PMID:23004589
On specification of initial conditions in turbulence models
Rollin, Bertrand; Andrews, Malcolm J
2010-12-01
Recent research has shown that initial conditions have a significant influence on the evolution of a flow towards turbulence. This important finding offers a unique opportunity for turbulence control, but also raises the question of how to properly specify initial conditions in turbulence models. We study this problem in the context of the Rayleigh-Taylor instability. The Rayleigh-Taylor instability is an interfacial fluid instability that leads to turbulence and turbulent mixing. It occurs when a light fluid is accelerated in to a heavy fluid because of misalignment between density and pressure gradients. The Rayleigh-Taylor instability plays a key role in a wide variety of natural and man-made flows ranging from supernovae to the implosion phase of Inertial Confinement Fusion (ICF). Our approach consists of providing the turbulence models with a predicted profile of its key variables at the appropriate time in accordance to the initial conditions of the problem.
Collapses of stellar protogalaxies from aspheric initial conditions
NASA Technical Reports Server (NTRS)
Miller, R. H.; Smith, B. F.
1981-01-01
Numerical experimens are presented which were intended to verify the independence of bar formation in rotating galaxy models from special initial conditions. Three-dimensional n-body programs were run starting from aspherical initial conditions characterized by particle rotational and peculiar velocities and offsets from sphericity for a set of 100,000 particles. All the initial configurations examined are observed to collapse to a thin form, overshoot, collapse again and again overshoot, with diameters and central densities similar to those observed under spheric initial conditions. Every aspheric collapse is also found to result in bar formation within two rotation periods, which is even sooner than in initially spherical conditions. In the intermediate stages of collapse, transient sheet patterns are found to be destroyed at asymmetries of 2-3%, while transient rings survived asymmetries of 6-7% but not 15-18%. It is noted that the results may be applicable to galaxy formation in the early universe, and possible mechanisms for the arresting of protogalactic collapse are indicated.
HBT Effect with Fluctuating Initial Conditions and Continuous Emission
NASA Astrophysics Data System (ADS)
Hama, Y.; Grassi, F.; Socolowski, O., Jr.; Kodama, T.
2005-02-01
We study effects of the event-by-event fluctuation of the initial conditions and the continuous pion emission during the whole development of the hot and dense matter formed in high-energy collisions on the two-pion interferometry. Important deviations occur, from the standard version of hydrodynamics with smooth initial conditions and a sudden freeze-out on a T=Tfo hypersurface. Comparison with data at RHIC shows that this description can give account of the mT dependence of RL and Rs and significantly improves Ro with respect to the usual version.
Accurate and Fast Convergent Initial-Value Belief Propagation for Stereo Matching
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
Successional stage of biological soil crusts: an accurate indicator of ecohydrological condition
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.
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
zeldovich-PLT: Zel'dovich approximation initial conditions generator
NASA Astrophysics Data System (ADS)
Eisenstein, Daniel; Garrison, Lehman
2016-05-01
zeldovich-PLT generates Zel'dovich approximation (ZA) initial conditions (i.e. first-order Lagrangian perturbation theory) for cosmological N-body simulations, optionally applying particle linear theory (PLT) corrections. The code uses double precision internally, but output format can be set to single or double precision.
Franke, O.L.; Reilly, T.E.; Bennett, G.D.
1984-01-01
Accurate definition of boundary and initial conditions is an essential part of conceptualizing and modeling ground-water flow systems. This report explains 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. (USGS)
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.
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. PMID:25539927
Zhang, Xiujun; Zhao, Juan; Hao, Jin-Kao; Zhao, Xing-Ming; Chen, Luonan
2015-01-01
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. PMID:25539927
Generalized CMB initial conditions with pre-equality magnetic fields
Giovannini, Massimo; Kunze, Kerstin E.
2008-06-15
The most general initial conditions of cosmic microwave background anisotropies, compatible with the presence of pre-equality magnetic fields, are derived. When the plasma is composed of photons, baryons, electrons, cold dark matter particles and neutrinos, the initial data of the truncated Einstein-Boltzmann hierarchy contemplate one magnetized adiabatic mode and four (magnetized) nonadiabatic modes. After obtaining the analytical form of the various solutions, the Einstein-Boltzmann hierarchy is numerically integrated for the corresponding sets of initial data. The TT, TE and EE angular power spectra are illustrated and discussed for the magnetized generalization of the cold dark matter-radiation mode, of the baryon-radiation mode and of the nonadiabatic mode of the neutrino sector. Mixtures of initial conditions are examined by requiring that the magnetized adiabatic mode dominates over the remaining nonadiabatic contributions. In the latter case, possible degeneracies between complementary sets of initial data might be avoided through the combined analysis of the TT, TE and EE angular power spectra at high multipoles (i.e. l>1000)
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.
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
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.
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.
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
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.
NASA Astrophysics Data System (ADS)
Fundel, Felix; Zappa, Massimiliano
2011-09-01
Hydrological forecasts can benefit from model climatologies compiled from long, consistent, retrospective forecasts (reforecasts). Typical areas of application include the estimation of return periods for extreme events, the detection of model deficiencies, such as systematic errors or the calibration of current forecasts using the reforecasts, and suitable observations. One difficulty when creating long reforecasts is the availability of good states for the model initialization, as a sufficiently dense network of meteorological observations is rarely available in most catchments for a long period. With this study, the creation of forecast and reforecasts in such catchments is motivated by considering two aspects: first, a comparison where it is shown that hydrological forecasts benefit most from high-quality initial conditions on the basis of local observations, however, less accurate initial conditions using ERA-interim reanalysis are also sufficient to provide skillful hydrological forecasts useful for many users. Second, we demonstrate that hydrological reforecasts compiled without long-term meteorological observations have an additional value, e.g., they allow for more skillful runoff forecasts. Utilizing those reforecasts can compensate for forecast errors induced by less accurate initializations. For this study, hourly hydrological reforecasts, based on the PREcipitation-Runoff-EVApotranspiration HRU Model (PREVAH) were used, with an 18 year long, five-member global ensemble reforecast data set from the European Centre for Medium Range Weather Forecasts (ECMWF) Variable Resolution Ensemble Prediction System (VarEPS) as forcing for lead times up to 10 days. Three mesoscale catchments of different characteristics in the Swiss Alps were analyzed.
The microlocal spectrum condition, initial value formulations, and background independence
NASA Astrophysics Data System (ADS)
Stottmeister, Alexander; Thiemann, Thomas
2016-02-01
We analyze implications of the microlocal spectrum/Hadamard condition for states in a (linear) quantum field theory on a globally hyperbolic spacetime M in the context of a (distributional) initial value formulation. More specifically, we work in 3+1-split M ≅ ℝ × Σ and give a bound, independent of the spacetime metric, on the wave front sets of the initial data for a quasi-free Hadamard state in a quantum field theory defined by a normally hyperbolic differential operator P acting in a vector bundle E → π M . This aims at a possible way to apply the concept of Hadamard states within approaches to quantum field theory/gravity relying on a Hamiltonian formulation, potentially without a (classical) background metric g.
Stochastic bias from non-Gaussian initial conditions
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.
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.
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.
Liquefaction Potential of Unsaturated Nevada Sand at Different Initial Conditions
NASA Astrophysics Data System (ADS)
Xu, Jiting
It has been tacitly assumed that liquefaction does not occur in unsaturated soils during seismic events, because pore air behaves as a cushion and excess pore water pressure is difficult to accumulate. During recent earthquakes, some slopes composed of unsaturated soils experienced large deformation similar to fluid flow. One explanation for this phenomenon is that the unsaturated slopes completely lost their effective stress and reached a state of liquefaction. The field observation shows controversial phenomenon against current understanding on soil liquefaction. This work was motivated to solve this controversy by experimentally studying the following two questions: 1) are unsaturated soils liquefiable? and 2) how do the initial conditions, including relative density, effective confining pressure, and degree of saturation affect the liquefaction potential of unsaturated soils? To answer the above questions, a series of strain-controlled undrained cyclic loading triaxial tests on saturated and unsaturated Nevada sand were conducted. The index properties studied included particle size distribution, maximum and minimum void ratios, and specific gravity. To provide data for future numerical modeling on unsaturated Nevada sand, hysteretic soil water characteristics curves under different relative densities were also measured. For triaxial tests on saturated Nevada sand, the effects of initial relative density (i.e. Dr=30%, 50%, and 70%) and effective confining pressure (i.e. s'c0 =50 kPa, 100 kPa, and 200 kPa) on soil liquefaction were studied. For unsaturated soil tests, besides initial relative density (Dr=50%) and effective confining pressure ( s'c0 =100 kPa), the effects of initial degree of saturation (S r0=90%, 95%) on liquefaction were also investigated. For saturated Nevada sand, the liquefaction potential decreased with an increase of relative density and effective confining pressure. When the other initial conditions were the same, the cycles needed to make
Analyzing the sensitivity of drought recovery forecasts to land surface initial conditions
NASA Astrophysics Data System (ADS)
DeChant, Caleb M.; Moradkhani, Hamid
2015-07-01
Droughts are complex hydro-meteorological phenomena, which are challenging to both quantify and predict. From the perspective of drought quantification, knowledge of the land surface conditions is vital for determining the impacts a drought event is having on both the environment and society. Although such land surface information is essential for quantifying drought in real-time, the precise effect of land surface moisture deficits on future drought conditions is unknown. Forecasting of recovery from drought events is undoubtedly reliant on its intensity, yet the lead time at which a drought can be expected to recover is poorly understood. Due to this gap in knowledge, this study attempts to quantify the expected lead time for drought recovery, and the rate of drought recovery, by examining the loss of sensitivity to initial conditions within a climatological forecast. From this perspective, the expected recovery time from a specific drought event is quantified, based on a case study in the Upper Colorado River Basin in Southwestern USA for two initialization dates in years 2003 through 2008. This study has ramifications for understanding the time of drought recovery, and highlights the importance of accurate land surface state estimation. With respect to recent studies, the experiments presented here suggest that forecasts can be sensitive to initial conditions at greater lead-times, and therefore drought conditions are potentially more persistent than previously thought.
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.
Spectator field dynamics in de Sitter and curvaton initial conditions
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.
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.
Longitudinal hydrodynamics from event-by-event Landau initial conditions
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.
Longitudinal hydrodynamics from event-by-event Landau initial conditions
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
Initial conditions for anisotropic extended-type inflationary universes
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.
Predictability in France : atmospheric forcing or land surface initial conditions?
NASA Astrophysics Data System (ADS)
Singla, S.; Martin, E.; Céron, J.-P.; Regimbeau, F.
2010-09-01
A first study of a hydrological forecasting suite has already been done at seasonal time scales over France (Céron and al., 2010) in a context of adaptation for water resources management. The results showed the feasibility of hydrological seasonal forecasts by forcing the hydrometeorological model Safran-Isba-Modcou (SIM) with seasonal atmospheric forecasts from the DEMETER project. Scores were better for hydrological variables than for atmospheric variables for four river catchments for the spring season. The purpose of the present study is to quantify the sources of predictability of the hydrometeorological system. Two experiences were conducted in order to address this issue. The first experience consisted in testing the impact of the land surface initial conditions. We used realistic land surface initial state produced by the operational SIM model for the specific year and 9 random years of Safran atmospheric analyses (temperature and precipitation) from 1971 to 2001, in a consistent way with the previous study (Céron et al, 2010). The other atmospheric parameters (wind, specific humidity, long wave and short wave radiation and cloudiness) come from the SAFRAN climatology over the same period. The second experience was designed to evaluate the impact of the atmospheric forcing with 9 random years, chosen for the land surface initial state. The atmospheric forcing (temperature and precipitation) comes from the Safran analysis system for the corresponding year. Some results of this study will be presented on soil wetness index (SWI) forecasts and river flows forecasts for all stations in France. We will compare deterministic and probabilistic scores of the two experiences with those of the hydrological forecasting suite built with the seasonal forecasts from the DEMETER project. Perspectives for the downscaling of seasonal forecasts will be discussed in a last part. Céron J-P, Tanguy G, Franchistéguy L, Martin E, Regimbeau F and Vidal J-P, 2010. Hydrological
THE SIGNATURE OF INITIAL CONDITIONS ON MAGNETOHYDRODYNAMIC TURBULENCE
Dallas, V.; Alexakis, A. E-mail: alexakis@lps.ens.fr
2014-06-20
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 E∝k {sup –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 {sup –2} toward k {sup –5/3}. This transition occurs due to the decorrelation of the velocity and the current density which is proportional to Re{sub λ}{sup −3/2}. Finite Reynolds number behavior is observed without reaching a finite asymptote for the energy dissipation rate even for a simulation of Re{sub λ} ≅ 440 with 2048{sup 3} 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.
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
Modeling the initial conditions of interacting galaxy pairs using Identikit
NASA Astrophysics Data System (ADS)
Mortazavi, S. Alireza; Lotz, Jennifer M.; Barnes, Joshua E.; Snyder, Gregory F.
2016-01-01
We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit as a tool for modelling and matching the morphology and kinematics of the interacting pairs of equal-mass galaxies. In order to reduce the effect of subjective human judgement, we automate the selection of phase space regions used to match simulations to data, and we explore how selection of these regions affects the random uncertainties of parameters in the best-fitting model. In this work, we use an independent set of GADGET SPH simulations as input data to determine the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We test both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing H I versus H α as the line-of-sight velocity tracer. We find that we can group the results into tests with good, fair, and poor convergence based on the distribution of parameters of models close to the best-fitting model. For tests with good and fair convergence, we rule out large fractions of parameter space and recover merger stage, eccentricity, pericentric distance, viewing angle, and initial disc orientations within 3σ of the correct value. All of tests on prograde-prograde systems have either good or fair convergence. The results of tests on edge-on discs are less biased than face-on tests. Retrograde and polar systems do not converge and may require constraints from regions other than the tidal tails and bridges.
Multi-Scale Initial Conditions For Cosmological Simulations
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.
Ultrasound Fetal Weight Estimation: How Accurate Are We Now Under Emergency Conditions?
Dimassi, Kaouther; Douik, Fatma; Ajroudi, Mariem; Triki, Amel; Gara, Mohamed Faouzi
2015-10-01
The primary aim of this study was to evaluate the accuracy of sonographic estimation of fetal weight when performed at due date by first-line sonographers. This was a prospective study including 500 singleton pregnancies. Ultrasound examinations were performed by residents on delivery day. Estimated fetal weights (EFWs) were calculated and compared with the corresponding birth weights. The median absolute difference between EFW and birth weight was 200 g (100-330). This difference was within ±10% in 75.2% of the cases. The median absolute percentage error was 5.53% (2.70%-10.03%). Linear regression analysis revealed a good correlation between EFW and birth weight (r = 0.79, p < 0.0001). According to Bland-Altman analysis, bias was -85.06 g (95% limits of agreement: -663.33 to 494.21). In conclusion, EFWs calculated by residents were as accurate as those calculated by experienced sonographers. Nevertheless, predictive performance remains limited, with a low sensitivity in the diagnosis of macrosomia. PMID:26164286
NASA Astrophysics Data System (ADS)
Husain, S. Z.; Floryan, J. M.
2008-04-01
A fully implicit, spectral algorithm for the analysis of moving boundary problem is described. The algorithm is based on the concept of immersed boundary conditions (IBC), i.e., the computational domain is fixed while the time dependent physical domain is submerged inside the computational domain, and is described in the context of the diffusion-type problems. The physical conditions along the edges of the physical domain are treated as internal constraints. The method eliminates the need for adaptive grid generation that follows evolution of the physical domain and provides sharp resolution of the location of the boundary. Various tests confirm the spectral accuracy in space and the first- and second-order accuracy in time. The computational cost advantage of the IBC method as compared with the more traditional algorithm based on the mapping concept is demonstrated.
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.
The relationship between initial errorless learning conditions and subsequent performance.
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
Classical initial conditions for ultrarelativistic heavy ion collisions
NASA Astrophysics Data System (ADS)
Kovchegov, Yuri V.
2001-09-01
We construct an analytical expression for the distribution of gluons in the state immediately following a heavy ion collision in the quasi-classical limit of QCD given by the McLerran-Venugopalan model. The resulting gluon number distribution function includes the effects of all multiple rescatterings of gluons with the nucleons of both colliding nuclei. The typical transverse momentum k ⊥ of the produced gluons is shown to be of the order of the saturation scale of the nuclei Q s, as predicted by Mueller. We analyze the properties of the obtained distribution and demonstrate that due to multiple rescatterings it remains finite (up to logarithms of k ⊥) in the soft transverse momentum limit of k ⊥≪Q s, unlike the usual perturbative initial conditions given by collinear factorization. We calculate the total number of produced gluons and show that it is proportional to the total number of gluons inside the nuclear wave function before the collision with the proportionality coefficient c≈2 ln2 .
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. PMID:27122050
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.
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.
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.
On initial conditions for the hot big bang
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.
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
NASA Astrophysics Data System (ADS)
Legeais, JeanFrancois; Cazenave, Anny; Ablain, Michael; Larnicol, Gilles; Benveniste, Jerome; Johannessen, Johnny; Timms, Gary; Andersen, Ole; Cipollini, Paolo; Roca, Monica; Rudenko, Sergei; Fernandes, Joana; Balmaseda, Magdalena; Quartly, Graham; Fenoglio-Marc, Luciana; Meyssignac, Benoit; Scharffenberg, Martin
2016-04-01
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 the Sea Level ECV which has benefited from yearly extensions and now covers the period 1993-2014. We will firstly 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 validation, performed by several groups of the ocean and climate modeling community. At last, new altimeter standards have been developed and the best one have been recently selected in order to produce a full
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.
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.
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.
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 (1990) 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 ($\\lesssim 0.4\\,k_B$ nucleon$^{-1}$) can explode even in spherically symmetric simulations. Models with a large entropy ($\\gtrsim 6\\,k_B$ nucleon$^{-1}$) in the Si/O layer have a rather large explosion energy ($\\sim 4\\times 10^{50}$ erg) at the end of the simulations, which is still rapidly increasing.
ERIC Educational Resources Information Center
Doe, Nobutaka; Nakajima, Sadahiko; Tamai, Noriko
2004-01-01
In conditioned suppression of water licking behavior by rats, we obtained data indicating general transfer of fear conditioning. A series of experiments resulted in two major findings. First, pairing of a neutral stimulus with a shock in the initial conditioning task facilitated acquisition of subsequent fear conditioning to another neutral…
Classification of Initial conditions required for Substorm prediction.
NASA Astrophysics Data System (ADS)
Patra, S.; Spencer, E. A.
2014-12-01
We investigate different classes of substorms that occur as a result of various drivers such as the conditions in the solar wind and the internal state of the magnetosphere ionosphere system during the geomagnetic activity. In performing our study, we develop and use our low order physics based nonlinear model of the magnetosphere called WINDMI to establish the global energy exchange between the solar wind, magnetosphere and ionosphere by constraining the model results to satellite and ground measurements. On the other hand, we make quantitative and qualitative comparisons between our low order model with available MHD, multi-fluid and ring current simulations in terms of the energy transfer between the geomagnetic tail, plasma sheet, field aligned currents, ionospheric currents and ring current, during isolated substorms, storm time substorms, and sawtooth events. We use high resolution solar wind data from the ACE satellite, measurements from the CLUSTER and THEMIS missions satellites, and ground based magnetometer measurements from SUPERMAG and WDC Kyoto, to further develop our low order physics based model. Finally, we attempt to answer the following questions: 1) What conditions in the solar wind influence the type of substorm event. This includes the IMF strength and orientation, the particle densities, velocities and temperatures, and the timing of changes such as shocks, southward turnings or northward turnings of the IMF. 2) What is the state of the magnetosphere ionosphere system before an event begins. These are the steady state conditions prior to an event, if they exist, which produce the satellite and ground based measurements matched to the WINDMI model. 3) How does the prior state of the magnetosphere influence the transition into a particular mode of behavior under solar wind forcing. 4) Is it possible to classify the states of the magnetosphere into distinct categories depending on pre-conditioning, and solar wind forcing conditions? 5) Can we
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.
Spin-up behavior and effects of initial conditions for an integrated hydrologic model
NASA Astrophysics Data System (ADS)
Seck, Alimatou; Welty, Claire; Maxwell, Reed M.
2015-04-01
Initial conditions have been shown to have a strong effect on outputs of surface water models, but their impact on integrated hydrologic models is not well documented. We investigated the effects of initial conditions on an integrated hydrologic model of a 5632 km2 domain in the northeastern U.S. Simulations were run for the year 1980 using four initial conditions spanning a range of average depth to water table, including 1 m ("wet"), 3m, 5m, and 7 m ("dry") below land surface. Model outputs showed significant effects of initial conditions on basin-averaged variables such as subsurface storage, surface storage, and surface runoff, with the greatest impact observed on surface storage and runoff. Effects of initial conditions were related to meteorological conditions, with precipitation reducing the effects of initial conditions on surface storage and runoff. Additionally, feedbacks between soil moisture and land-energy fluxes affected the impacts of initial conditions: higher temperatures magnified the differences in storage, recharge, and discharge among the four initial-condition scenarios. Ten year recursive runs were conducted for the wet and dry scenarios. Spin-up times varied by model components and were considerably smaller for land-surface states and fluxes. Spin-up for dry initial conditions was slower than for wet initial conditions, indicating longer system memory for dry initial conditions. These variations in persistence of initial conditions should be taken into consideration when designing model initialization approaches. More broadly, this behavior is indicative of increased persistence of the effects of dry years as opposed to wet years in hydrologic systems.
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
Impact of initial and boundary conditions on preferential flow.
Hincapié, Ingrid; Germann, Peter F
2009-02-16
Preferential flow in soil is approached by a water-content wave, WCW, that proceeds downward from the ground surface. WCWs were obtained from sprinkler experiments with infiltration rates varying from 5 to 40 mm h(-1). TDR-probes and tensiometers measured volumetric water contents theta(z,t) at seven depths, and capillary heads, h(z,t) at six depths in a column of an undisturbed soil. The wave is characterized by the velocity of the wetting front, c(W), the amplitude, w(S), and the final water content, theta*. We tested with uni-variate and bi-variate linear regressions the impacts of initial volumetric water contents, theta(ini), and input rates, q(S), on c(W), w(S) and theta*. The test showed that theta(ini) influenced theta* and w(S) and q(S) effected c(W). The expected proportionality of w(S) approximately = qs(1/3) was weak and c(W) approximately = qs(2/3) was strong. PMID:19012995
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
Effects of initial conditions on a single jet in crossflow
NASA Technical Reports Server (NTRS)
Liscinsky, D. S.; True, B.; Holdeman, J. D.
1995-01-01
An experimental investigation of the effects of jet inlet flow conditions has been conducted for the isothermal mixing of a single jet injected into a crossflow. Jet penetration and mixing was studied using planar Mie scattering to measure time-averaged jet mixture fraction distributions. The effects of 'passive' control methods such as jet 'tabs' and jet swirl are reported. Mixing effectiveness, determined using a spatial unmixedness parameter based on the variance of the mean jet concentration distributions, was compared to a baseline case of a round jet injected into a uniform crossflow. All results are compared at a jet-to-mainstream momentum-flux ratio of 8.5. In the near-field, the mixing rates are similar to, or less than, the baseline configuration using this measure of mixedness. None of the tested configurations appear to significantly augment mixing within a downstream distance of 3 diameters of an equivalent-area round orifice.
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.
42 CFR 418.54 - Condition of participation: Initial and comprehensive assessment of the patient.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 3 2012-10-01 2012-10-01 false Condition of participation: Initial and... Conditions of Participation: Patient Care § 418.54 Condition of participation: Initial and comprehensive... needs of the patient's family and other individuals focusing on the social, spiritual, and...
42 CFR 418.54 - Condition of participation: Initial and comprehensive assessment of the patient.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 42 Public Health 3 2014-10-01 2014-10-01 false Condition of participation: Initial and... Conditions of Participation: Patient Care § 418.54 Condition of participation: Initial and comprehensive... needs of the patient's family and other individuals focusing on the social, spiritual, and...
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.
Initiation of clement surface conditions on the earliest Earth
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
Initiation of clement surface conditions on the earliest Earth.
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. PMID:11259665
Woontner, M; Jaehning, J A
1993-12-01
We demonstrate the successful adaptation to other yeast species of a protocol previously described for production of transcriptionally active whole cell extracts from Saccharomyces cerevisiae (Woontner and Jaehning, 1990, J. Biol. Chem. 265, 8979-8982). Extracts prepared from Schizosaccharomyces pombe, Kluyveromyces lactis and Candida glabrata were all capable of initiating transcription from a template containing the S. cerevisiae CYC1 TATA box fused to a G-less cassette. Transcription in all of the extracts was sensitive to inhibition by alpha-amanitin, indicating that it was catalysed by RNA polymerase II, and was dramatically stimulated by the chimeric activator GAL4/VP16. The different extracts used different subsets of a group of three initiation sites. PMID:8154183
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.
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.
NASA Astrophysics Data System (ADS)
Li, Yang
The properties of the quark-gluon plasma are being thoroughly studied by utilizing relativistic heavy ion collisions. After its invention in astronomy in the 1950s, intensity interferometry was found to be a robust method to probe the spatial and temporal information of the nuclear collisions also. Although rescattering effects are negligible in elementary particle collisions, it may be very important for heavy ion collisions at RHIC and in the future LHC. Rescattering after production will modify the measured correlation function and make it harder to extract the dynamical information from data. To better understand the data which are dimmed by this final state process, we derive a general formula for intensity interferometry which can calculate rescattering effects easily. The formula can be used both non-relativistically and relativistically. Numerically, we found that rescattering effects on kaon interferometry for RHIC experiments can modify the measured ratio of the outward radius to the sideward radius, which is a sensitive probe to the equation of state, by as large as 15%. It is a nontrivial contribution which should be included to understand the data more accurately. The second part of this thesis is on the initial conditions in relativistic heavy ion collisions. Although relativistic hydrodynamics is successful in explaining many aspects of the data, it is only valid after some finite time after nuclear contact. The results depend on the choice of initial conditions which, so far, have been very uncertain. I describe a formula based on the McLerran-Venugopalan model to compute the initial energy density. The soft gluon fields produced immediately after the overlap of the nuclei can be expanded as a power series of the proper time t. Solving Yang-Mills equations with color current conservation can give us the analytical formulas for the fields. The local color charges on the transverse plane are stochastic variables and have to be taken care of by random
ON THE INITIAL CONDITIONS FOR STAR FORMATION AND THE INITIAL MASS FUNCTION
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.
42 CFR 433.130 - Waiver of conditions of initial operation and approval.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 42 Public Health 4 2010-10-01 2010-10-01 false Waiver of conditions of initial operation and... HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL ASSISTANCE PROGRAMS STATE FISCAL ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems § 433.130 Waiver of conditions of initial...
Influence of changes in initial conditions for the simulation of dynamic systems
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.
Terrestrial planet formation in low-mass disks: dependence with initial conditions
NASA Astrophysics Data System (ADS)
Ronco, M. P.; de Elía, G. C.; Guilera, O. M.
2014-07-01
In general, most of the studies of terrestrial-type planet formation typically use ad hoc initial conditions. In this work we improved the initial conditions described in Ronco & de Elía (2014) starting with a semi-analytical model wich simulates the evolution of the protoplanetary disk during the gas phase. The results of the semi-analytical model are then used as initial conditions for the N-body simulations. We show that the planetary systems considered are not sensitive to the particular initial distribution of embryos and planetesimals and thus, the results are globally similar to those found in the previous work.
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
NASA Astrophysics Data System (ADS)
Chatterjee, Rupa; Holopainen, Hannu; Renk, Thorsten; Eskola, Kari J.
2013-08-01
Event-by-event fluctuating initial conditions (IC) in the ideal hydrodynamic calculation are known to enhance the production of thermal photons significantly compared to a smooth initial state averaged profile in the range pT > 1GeV / c for 200A GeV Au+Au collisions at RHIC and 2.76A TeV Pb + Pb collisions at LHC. The 'hotspots' or the over-dense regions in the fluctuating IC produce more high pT photons compared to the smooth IC due to the strong temperature dependent emission of the thermal radiation. This enhancement is expected to be more pronounced for peripheral collisions, for lower beam energies, and for larger values of plasma formation time. A suitably normalized ratio of central to peripheral yield of thermal photons (Rcpγ) is a potential probe to study the density fluctuations and their size in the initial conditions.
Initial condition effects on large scale structure in numerical simulations of plane mixing layers
NASA Astrophysics Data System (ADS)
McMullan, W. A.; Garrett, S. J.
2016-01-01
In this paper, Large Eddy Simulations are performed on the spatially developing plane turbulent mixing layer. The simulated mixing layers originate from initially laminar conditions. The focus of this research is on the effect of the nature of the imposed fluctuations on the large-scale spanwise and streamwise structures in the flow. Two simulations are performed; one with low-level three-dimensional inflow fluctuations obtained from pseudo-random numbers, the other with physically correlated fluctuations of the same magnitude obtained from an inflow generation technique. Where white-noise fluctuations provide the inflow disturbances, no spatially stationary streamwise vortex structure is observed, and the large-scale spanwise turbulent vortical structures grow continuously and linearly. These structures are observed to have a three-dimensional internal geometry with branches and dislocations. Where physically correlated provide the inflow disturbances a "streaky" streamwise structure that is spatially stationary is observed, with the large-scale turbulent vortical structures growing with the square-root of time. These large-scale structures are quasi-two-dimensional, on top of which the secondary structure rides. The simulation results are discussed in the context of the varying interpretations of mixing layer growth that have been postulated. Recommendations are made concerning the data required from experiments in order to produce accurate numerical simulation recreations of real flows.
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
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.
Interrogating Commonly Applied Initial Condition Assumptions in Geospeedometry using NanoSIMS
NASA Astrophysics Data System (ADS)
Till, C. B.; Boyce, J. W.
2014-12-01
The geologically short (days to centuries) timescales associated with thermochemical changes in magma chambers during the prelude to eruption are typically beyond the resolution of long-lived radioisotopic geochronometers but can be resolved by "geospeedometry" that quantifies the relatively rapid diffusional relaxation of compositional zoning in igneous phenocrysts. When combined with absolute dating, geospeedometry can reveal long-term chronologies of compositional and thermal oscillations in magma chambers. The ability to accurately constrain timescales via geospeedometry is limited in part by the spatial resolution of commonly used analytical techniques and the derivative chemical profiles, especially in the case of very short timescales or very slow diffusing elements, where the chemical profile is often approximated as a step-function. We present geospeedometry of chemical profiles collected with the NanoSIMS ion microprobe in multi-collection mode with sub-micron resolution (e.g., 0.3 micron spacing). This data facilitates a comparison of how well the timescales calculated with the different experimentally-determined diffusivities and collected along the same profile agree and an interrogation of commonly made model assumptions in geospeedometry. For example, electron probe profiles across internal sanidine zone boundaries from a ca. 250 ka rhyolite lava from Yellowstone Caldera reveal a step function in anorthite content at 10 micron spacing and evidence for earlier dissolution prior to new zone growth, yet we find no observable difference in the width of Ba, Sr and Mg diffusion profiles collected via NanoSIMS for the same profile. These observations support the hypothesis that very little to no diffusive relaxation has affected the initial concentration profile that was produced by crystal growth during magma mixing. Our results highlight the need to quantitatively constrain initial conditions when applying geospeedometry to intermediate to silicic
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.
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.
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.
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…
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
Initial Activation and Operation of the Power Conditioning System for the National Ignition Facility
Newton, M A; Kamm, R E; Fulkerson, E S; Hulsey, S D; Lao, N; Parrish, G L; Pendleton, D L; Petersen, D E; Polk, M; Tuck, J M; Ullery, G T; Moore, W B
2003-08-20
The NIF Power Conditioning System (PCS) resides in four Capacitor Bays, supplying energy to the Master and Power Amplifiers which reside in the two adjacent laser bays. Each capacitor bay will initially house 48 individual power conditioning modules, shown in Figure 2, with space reserved for expansion to 54 modules. The National Ignition Facility (NIF) Power Conditioning System (PCS) is a modular capacitive energy storage system that will be capable of storing nearly 400 MJ of electrical energy and delivering that energy to the nearly 8000 flashlamps in the NIF laser. The first sixteen modules of the power conditioning system have been built, tested and installed. Activation of the first nine power conditioning modules has been completed and commissioning of the first ''bundle'' of laser beamlines has begun. This paper will provide an overview of the power conditioning system design and describe the status and results of initial testing and activation of the first ''bundle'' of power conditioning modules.
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.
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).
Dynamical fine-tuning of initial conditions for small field inflation
NASA Astrophysics Data System (ADS)
Iso, Satoshi; Kohri, Kazunori; Shimada, Kengo
2016-04-01
Small-field inflation (SFI) is widely considered to be unnatural because an extreme fine-tuning of the initial condition is necessary for sufficiently large e -folding. In this paper, we show that the unnaturally looking initial condition can be dynamically realized without any fine-tuning if the SFI occurs after rapid oscillations of the inflaton field and particle creations by preheating. In fact, if the inflaton field ϕ is coupled to another scalar field χ through the interaction g2χ2ϕ2 and the vacuum energy during the small field inflation is given by λ M4, the initial value can be dynamically set at (√{λ }/g )M2/Mpl, which is much smaller than the typical scale of the potential M . This solves the initial condition problem in the new inflation model or some classes of the hilltop inflation models.
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.
42 CFR 418.54 - Condition of participation: Initial and comprehensive assessment of the patient.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 42 Public Health 3 2010-10-01 2010-10-01 false Condition of participation: Initial and comprehensive assessment of the patient. 418.54 Section 418.54 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM HOSPICE CARE Conditions of Participation: Patient Care § 418.54...
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.
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.
Correcting the initialization of models with fractional derivatives via history-dependent conditions
NASA Astrophysics Data System (ADS)
Du, Maolin; Wang, Zaihua
2015-08-01
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.
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.
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
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
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.
An Investigation of the Influence of Initial Conditions on Rayleigh-Taylor Mixing
Mueschke, N J; Schilling, O
2004-10-04
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.
Effect of initial conditions on Rayleigh-Taylor mixing: modal interaction
NASA Astrophysics Data System (ADS)
Kuchibhatla, S.; Ranjan, D.
2013-07-01
Experimental investigation of the interaction of different modes of the initial conditions on Rayleigh-Taylor mixing was performed using the Water Channel facility at Texas A&M University. Hot and cold water (with a temperature difference of ˜7-8 °C) selected as working fluids were unstably stratified using a splitter plate resulting in a low Atwood number of the order of 10-3. Interaction of multiple (up to 3) modes of the initial condition was studied by varying the wavelengths and phase angles that were generated at the interface of these fluids. Using a servo controlled flapper system, wavelengths were varied between 2 and 8 cm and phase angles within 0-180°, and the dependence of ensemble averaged mixing width in the early stages of growth on initial conditions is studied. High-resolution images of the flowfield indicate that changing the phase angle results in the leaning phenomenon, i.e. the leaning of bubbles and spikes with respect to gravitational acceleration and relative to each other. For the experiments with the binary-mode initial condition with a fixed wavelength ratio, λ1/λ2, of 4.0, variation of the phase angle does not significantly affect the ensemble-averaged mixing width. Mixing rate data from ensemble averaging indicates greater dissipation rates at the initial times that taper off logarithmically to the order of mean kinematic viscosity at later times.
3-D simulations to investigate initial condition effects on the growth of Rayleigh-Taylor mixing
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.
ICBC Version 3. 1: TMI-2 (Three Mile Island) Initial and Boundary Conditions data base
Brower, R W; Fackrell, L J; Golden, D W; Harris, M L; Olaveson, C L
1988-01-01
The TMI-2 initial and boundary conditions data base is a micro computer data base which provides the required initial and boundary conditions to simulate the TMI-2 accident. Additionally, other time series plant measurements related to the accident are included in the data base. Major features of the data base are the ability to plot, manipulate and list data as well as to enter user supplied data (e.g. results of simulations). The user guide provides the instructions for installation and operation of the data base. 10 refs., 21 figs.
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
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.
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.
Voutsinas, Evangelos; Boviatsis, John
2007-12-26
We study Rabi oscillations between two subbands of a symmetric double quantum well that is coupled by a strong electromagnetic field. We use the effective nonlinear Bloch equations for the description of the system dynamics and present numerical results for different initial conditions of the system.
40 CFR 300.130 - Determinations to initiate response and special conditions.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 27 2010-07-01 2010-07-01 false Determinations to initiate response and special conditions. 300.130 Section 300.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND COMMUNITY RIGHT-TO-KNOW PROGRAMS NATIONAL OIL AND HAZARDOUS SUBSTANCES POLLUTION CONTINGENCY...
40 CFR 300.130 - Determinations to initiate response and special conditions.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 28 2014-07-01 2014-07-01 false Determinations to initiate response and special conditions. 300.130 Section 300.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND COMMUNITY RIGHT-TO-KNOW PROGRAMS NATIONAL OIL AND HAZARDOUS SUBSTANCES POLLUTION CONTINGENCY...
42 CFR 418.54 - Condition of participation: Initial and comprehensive assessment of the patient.
Code of Federal Regulations, 2011 CFR
2011-10-01
... palliation and management of the terminal illness and related conditions. (a) Standard: Initial assessment... calendar days after the election of hospice care in accordance with § 418.24. (c) Standard: Content of the... need for referrals and further evaluation by appropriate health professionals. (d) Standard: Update...
Experimental study of initial condition dependence on mixing in Richtmyer-Meshkov instabilities
Balasubramanian, Sridhar; Prestridge, Katherine P; Orlicz, Gregory C; Balasubramaniam, Balakumar J
2010-11-18
Recent work has shown that buoyancy-driven turbulence can be affected at late time by initial conditions, thus presenting an opportunity to predict and design late-time turbulent mixing, with transformative impact on our understanding and prediction of Inertial Confinement Fusion and general fluid mixing processes. In this communication, we report results on the initial condition parameters, amplitude ({delta}) and wavelength ({lambda}) of perturbation, that impact the material mixing and transition to turbulence in shock-driven Richtmyer-Meshkov instability. Experiments were conducted using a stable, membrane-free, heavy gas varicose curtain (air-SF{sub 6}-air) at shock Mach number, Ma = 1.2. The velocity and density field of our initial conditions was quantified using Particle Image Velocimetry (PIV) and Planar-Laser Induced Fluorescence (PLIF) respectively. Quantitative measurements on the temporal and spatial evolution of developing structures after first shock and subsequent re-shock at different times obtained using PLlF aid us in understating the importance of the initial conditions on transition to turbulence and mixing.
Model forecast skill and sensitivity to initial conditions in the seasonal Sea Ice Outlook
NASA Astrophysics Data System (ADS)
Blanchard-Wrigglesworth, E.; Cullather, R. I.; Wang, W.; Zhang, J.; Bitz, C. M.
2015-10-01
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.
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.
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.
Dark energy with non-adiabatic sound speed: initial conditions and detectability
Ballesteros, Guillermo; Lesgourgues, Julien E-mail: julien.lesgourgues@cern.ch
2010-10-01
Assuming that the universe contains a dark energy fluid with a constant linear equation of state and a constant sound speed, we study the prospects of detecting dark energy perturbations using CMB data from Planck, cross-correlated with galaxy distribution maps from a survey like LSST. We update previous estimates by carrying a full exploration of the mock data likelihood for key fiducial models. We find that it will only be possible to exclude values of the sound speed very close to zero, while Planck data alone is not powerful enough for achieving any detection, even with lensing extraction. We also discuss the issue of initial conditions for dark energy perturbations in the radiation and matter epochs, generalizing the usual adiabatic conditions to include the sound speed effect. However, for most purposes, the existence of attractor solutions renders the perturbation evolution nearly independent of these initial conditions.
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.
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).
Effects of Initial Conditions on Compressible Mixing in Supernova-Relevant Laboratory Experiments
Miles, A R; Edwards, M; Greenough, J
2004-04-30
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 paper, we summarize recent results from our computational study of unstable systems driven by high Mach number shock and blast waves. For planar multimode systems, 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. 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. Initial conditions predicted by some recent stellar calculations are incompatible with self-similarity.
EARLY DYNAMICAL EVOLUTION OF THE SOLAR SYSTEM: PINNING DOWN THE INITIAL CONDITIONS OF THE NICE MODEL
Batygin, Konstantin; Brown, Michael E.
2010-06-20
In the recent years, the 'Nice' model of solar system formation has attained an unprecedented level of success in reproducing much of the observed orbital architecture of the solar system by evolving the planets to their current locations from a more compact configuration. Within the context of this model, the formation of the classical Kuiper Belt requires a phase during which the ice giants have a high eccentricity. An outstanding question of this model is the initial configuration from which the solar system started out. Recent work has shown that multi-resonant initial conditions can serve as good candidates, as they naturally prevent vigorous type-II migration. In this paper, we use analytical arguments, as well as self-consistent numerical N-body simulations to identify fully resonant initial conditions, whose dynamical evolution is characterized by an eccentric phase of the ice giants, as well as planetary scattering. We find a total of eight such initial conditions. Four of these primordial states are compatible with the canonical 'Nice' model, while the others imply slightly different evolutions. The results presented here should prove useful in further development of a comprehensive model for solar system formation.
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.
NASA Astrophysics Data System (ADS)
Balasubramanian, S.; Orlicz, G. C.; Prestridge, K. P.; Balakumar, B. J.
2012-03-01
We present an experimental study on the dependence of initial condition parameters, namely, the amplitude δ and wavenumber κ (κ = 2π/λ, where λ is the wavelength) of perturbations, on turbulence and mixing in shock-accelerated Richtmyer-Meshkov (R-M) unstable fluid layers. A single mode, membrane-free varicose heavy gas curtain (air-SF6-air) at a shock Mach number M = 1.2 was used in our experiments. The density (concentration) and velocity fields for this initial configuration were measured using planar laser -induced fluorescence (PLIF) and particle image velocimetry (PIV). In order to understand the effects of multi-mode initial conditions on shock-accelerated mixing, the evolving fluid interface formed during the incident shock (M = 1.2) was shocked again by a reflected shock wave at various times using a movable wall, thus enabling us to change both δ and κ simultaneously. A dimensionless length-scale defined as η = κδ is proposed to parametrically link the initial condition dependence to late-time mixing. It was observed experimentally that high wavenumber (short wavelength) modes enhance the mixing and transition to turbulence in these flows. Statistics such as power spectral density, density self-correlation, turbulent kinetic energy, and the rms of velocity fluctuations were measured using simultaneous PLIF-PIV to quantify the amount of mixing for varying values of η. The results indicate a dependence of initial condition parameters on mixing at late times. The results of this study present an opportunity to predict and "design" late-time turbulent mixing that has applications in inertial confinement fusion and general fluid mixing processes.
ACCURATE TIME-DEPENDENT WAVE PACKET STUDY OF THE H{sup +}+LiH REACTION AT EARLY UNIVERSE CONDITIONS
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.
Initial Conditions with Flow from a McLerran Venugopalan model with Transverse Dynamics
NASA Astrophysics Data System (ADS)
Chen, Guangyao; Fries, Rainer J.
2013-09-01
Using a recursive solution of the Yang-Mills equation, we calculate analytic expressions for the gluon fields created in ultra-relativistic heavy ion collisions at small times τ. We have worked out explicit solutions for the fields and the energy momentum tensor up to 4th order in an expansion in τ. We generalize the McLerran-Venugopalan model to allow for a systematic treatment of averaged charge densities μ2 that vary as a function of transverse coordinates. This allows us to calculate radial, elliptic and directed flow of gluon fields. Our results can serve as initial conditions for hydrodynamic simulations of nuclear collisions that include initial flow.
Evaluation of the effects of initial conditions on transients in PUMA
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.
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.
Li, Wei; Qian, Yong-Qiang; Han, Lei; Liu, Jun-Xiang; Sun, Zhen-Yuan
2014-08-15
Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) is a sensitive technique for normalization of the gene expression level of target genes. Buffalograss (Buchloe dactyloides), a warm-season turfgrass with strong abiotic stress resistance, is widely used in North China. Up to now, no work was performed to evaluate the reference genes in buffalograss. In this study, the expression profiles of ten potential reference genes were examined by qRT-PCR in 24 buffalograss samples, which were subjected to a different treatment (salt, osmotic, cold and heat). Three qRT-PCR analysis methods (GeNorm, NormFinder, and Bestkeeper) were used to evaluate the stability of gene expression. The results indicated that DNAJ and β-ACTIN were the optimal reference genes for salt-treated leaves, and the combination of PP2A and GAPDH was better reference genes for PEG-treated leaves. Under cold stress, DNAJ and β-ACTIN showed less variety of expression level in leaves. DNAJ and GAPDH exhibited the most stable expression in heat-treated samples. To sum up, glyceral-dehyde-3-phosphate dehydrogenase (GAPDH), β-ACTIN, DNAJ-like protein (DNAJ) and protein phosphatase 2A (PP2A) were selected as the most stable reference gene among all tested samples. To further validate the suitability of these reference genes, the expression levels of DREB2 (homologs of AtDREB2) were analyzed in parallel. Our results show that the best reference genes differed across different experimental conditions, and these results should enable better normalization and quantification of transcript levels in buffalograss in the future. PMID:24914494
Gilmour, R S; Allan, M; Paul, J
1984-01-01
The human epsilon-globin gene was transcribed in vitro in isolated K562 cell nuclei by using exogenous Escherichia coli RNA polymerase (EC 2.7.7.6). Newly formed RNA transcripts were distinguished from nuclear RNA molecules by (i) incorporating mercurated UTP into RNA under conditions in which the endogenous polymerase II is inactive and (ii) subsequently isolating the mercurated RNA by affinity chromatography on thiolated Sepharose. A specific 5'-end-labeled probe spanning the epsilon-globin gene cap site was used in nuclease S1 mapping studies to examine the in vitro initiation site of the isolated transcripts. It was found that transcription occurred from the coding strand only and originated almost entirely from a point that was identical to that of the major cap site for epsilon-globin mRNA in vivo. Images PMID:6330734
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
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.; ;
Purcell, I; Newall, N; Farrer, M
1997-01-01
Objective—To compare prospectively the prognostic accuracy of a 50% decrease in ST segment elevation on standard 12-lead electrocardiograms (ECGs) recorded at 60, 90, and 180 minutes after thrombolysis initiation in acute myocardial infarction. Design—Consecutive sample prospective cohort study. Setting—A single coronary care unit in the north of England. Patients—190 consecutive patients receiving thrombolysis for first acute myocardial infarction. Interventions—Thrombolysis at baseline. Main outcome measures—Cardiac mortality and left ventricular size and function assessed 36 days later. Results—Failure of ST segment elevation to resolve by 50% in the single lead of maximum ST elevation or the sum ST elevation of all infarct related ECG leads at each of the times studied was associated with a significantly higher mortality, larger left ventricular volume, and lower ejection fraction. There was some variation according to infarct site with only the 60 minute ECG predicting mortality after inferior myocardial infarction and only in anterior myocardial infarction was persistent ST elevation associated with worse left ventricular function. The analysis of the lead of maximum ST elevation at 60 minutes from thrombolysis performed as well as later ECGs in receiver operating characteristic curves for predicting clinical outcome. Conclusion—The standard 12-lead ECG at 60 minutes predicts clinical outcome as accurately as later ECGs after thrombolysis for first acute myocardial infarction. Keywords: myocardial infarction; thrombolysis; ST segment elevation PMID:9415005
Using Data to Determine the Initial Conditions in Heavy Ion Collisions
NASA Astrophysics Data System (ADS)
Soltz, Ron; Garishvili, Irakli; Abelev, Betty
2012-10-01
We have developed a framework, the Comprehensive Heavy Ion Model Evaluation Reporting Algorithm (CHIMERA) to determine the optimal model and initial conditions of heavy ion collisions by comparing to data from a variety of observables. We have used this framework to study simple participant and binary collisions scaling in the presence of pre-equilibrium flow in the context of the VH2 2D+1 viscous hydrodynamic model with UrQMD afterburner for data from RHIC. We have also used this framework to explore the significance of variations in the equation of state. We have recently begun to apply this framework to a new hydro-solver tools known as CHOMBO, which incorporates adaptive mesh refinement techniques that are well suited to the study of initial state fluctuations. We will review results from using CHIMERA with VH2, and discuss future plans for using CHOMBO to study initial state fluctuations.
Micro-mechanical study of stress path and initial conditions in granular materials using DEM
NASA Astrophysics Data System (ADS)
Dorostkar, Omid; Mirghasemi, Ali Asghar
2016-03-01
The macroscale response of granular materials under different loading conditions stems from the alteration of micromechanical properties during loading. Previous studies have used either physical experiments or discrete element method simulations to explore the effect of initial conditions and stress path on granular materials. However, microscale studies are not sufficient, especially for various loading paths. We study micromechanics of granular materials using the stress-force-fabric (SFF) relationship for a better understanding of the behavior of granular materials. Triaxial compression and extension tests are conducted on samples containing 1000 spherical particles, with periodic boundaries, and the effect of initial porosity is studied. In the next step, using the SFF relationship, we study the effect of anisotropic consolidation ratio. In addition to providing an appropriate explanation for shear strength out of evolution of anisotropy coefficients, our results show that anisotropic consolidation does not affect the micromechanical properties of granular materials in a way to change mobilized friction angle of sample at failure point.
Non-Gaussian initial conditions in ΛCDM: Newtonian, relativistic, and primordial contributions
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}.
Quantification of discreteness effects in cosmological N-body simulations: Initial conditions
Joyce, M.; Marcos, B.
2007-03-15
The relation between the results of cosmological N-body simulations, and the continuum theoretical models they simulate, is currently not understood in a way which allows a quantification of N dependent effects. In this first of a series of papers on this issue, we consider the quantification of such effects in the initial conditions of such simulations. A general formalism developed in [A. Gabrielli, Phys. Rev. E 70, 066131 (2004).] allows us to write down an exact expression for the power spectrum of the point distributions generated by the standard algorithm for generating such initial conditions. Expanded perturbatively in the amplitude of the input (i.e. theoretical, continuum) power spectrum, we obtain at linear order the input power spectrum, plus two terms which arise from discreteness and contribute at large wave numbers. For cosmological type power spectra, one obtains as expected, the input spectrum for wave numbers k smaller than that characteristic of the discreteness. The comparison of real space correlation properties is more subtle because the discreteness corrections are not as strongly localized in real space. For cosmological type spectra the theoretical mass variance in spheres and two-point correlation function are well approximated above a finite distance. For typical initial amplitudes this distance is a few times the interparticle distance, but it diverges as this amplitude (or, equivalently, the initial redshift of the cosmological simulation) goes to zero, at fixed particle density. We discuss briefly the physical significance of these discreteness terms in the initial conditions, in particular, with respect to the definition of the continuum limit of N-body simulations.
Precipitation-climate sensitivity to initial conditions in an atmospheric general circulation model
Covey, C., LLNL
1997-03-01
Atmospheric climate, in contrast to weather, is traditionally considered to be determined by boundary conditions such as sea surface temperature (SST). To test this hypothesis, we examined annual mean precipitation from an ensemble of 20 general circulation model (GCM) simulations. Ensemble members were forced with identical 10-year series of SST and sea ice, but they began with slightly differing initial conditions. A surprisingly small proportion of the variance in the output is attributable to the effects of boundary forcing. This result-and similar evidence from smaller ensembles of other GCM simulations-implies that long-term precipitation variations are mostly unpredictable, even if SST forecasts are `perfect.`
Massive Infrared-Quiet Dense Cores: Unveiling the Initial Conditions of High-Mass Star Formation
NASA Astrophysics Data System (ADS)
Motte, F.; Bontemps, S.; Schneider, N.; Schilke, P.; Menten, K. M.
2008-05-01
As Th. Henning said at the conference, cold precursors of high-mass stars are now ``hot topics''. We here propose some observational criteria to identify massive infrared-quiet dense cores which can host the high-mass analogs of Class~0 protostars and pre-stellar condensations. We also show how far-infrared to millimeter imaging surveys of entire complexes forming OB stars are starting to unveil the initial conditions of high-mass star formation.
Optimal Initial Conditions and Stochastic Forcing for Central and East Pacific ENSO Events
NASA Astrophysics Data System (ADS)
Vimont, D.; Newman, M.; Alexander, M. A.
2014-12-01
Research on the structure and evolution of individual El Niño / Southern Oscillation (ENSO) events has identified two categories of ENSO event characteristics that can be defined by maximum equatorial SST anomalies centered in the Central Pacific (around the dateline to 150°W; CP events) or in the Eastern Pacific (west of about 150°W; EP events). The distinction between these two events is not just academic: both types of event evolve differently, implying different predictability; the events tend to have different maximum amplitude; and the global teleconnection differs between each type of event. The identification of initial conditions that tend to grow into each type of event will lead to better predictability and better dynamical understanding of individual ENSO event evolution. In this study, we use a linear inverse model framework to (i) calculate optimal initial conditions that lead to CP or EP ENSO events, (ii) identify patterns of stochastic forcing that are responsible for exciting each type of event, and (iii) investigate the relative roles of stochastic forcing and internal dynamics in generating long term variations in CP and EP ENSO event statistics. We target our analysis toward CP or EP ENSO events by constructing a CP or EP norm under which optimal initial conditions are calculated. Results highlight a fundamentally different role for the Pacific Meridional Mode in the initial condition and subsequent evolution of CP vs. EP ENSO events. Analysis of stochastic forcing shows that CP ENSO events evolve via the Seasonal Footprinting Mechanism, in which mid-latitude atmospheric variability associated with the atmospheric North Pacific Oscillation lead to ENSO events through the Pacific Meridional Mode. Finally, variations in ENSO event statistics are investigated using a linear inverse model derived from a long simulation of the National Center for Atmospheric Research Community Earth System Model. Variations in stochastic forcing vs. dynamics of
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.
NASA Astrophysics Data System (ADS)
Doumler, Timur; Hoffman, Yehuda; Courtois, Hélène; Gottlöber, Stefan
2013-04-01
We propose a new method to recover the cosmological initial conditions of the presently observed galaxy distribution, which can serve to run constrained simulations of the Local Universe. Our method, the Reverse Zeldovich Approximation (RZA), can be applied to radial galaxy peculiar velocity data and extends the previously used constrained realizations (CR) method by adding a Lagrangian reconstruction step. The RZA method consists of applying the Zeldovich approximation in reverse to galaxy peculiar velocities to estimate the cosmic displacement field and the initial linear matter distribution from which the present-day Local Universe evolved. We test our method with a mock survey taken from a cosmological simulation. We show that the halo peculiar velocities at z = 0 are close to the linear prediction of the Zeldovich approximation, if a grouping is applied to the data to remove virial motions. We find that the addition of RZA to the CR method significantly improves the reconstruction of the initial conditions. The RZA is able to recover the correct initial positions of the velocity tracers with a median error of only 1.36 Mpc h-1 in our test simulation. For realistic sparse and noisy data, this median increases to 5 Mpc h-1. This is a significant improvement over the previous approach of neglecting the displacement field, which introduces errors on a scale of 10 Mpc h-1 or even higher. Applying the RZA method to the upcoming high-quality observational peculiar velocity catalogues will generate much more precise constrained simulations of the Local Universe.
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.
Effect of initial conditions on mixing within a turbulent channel flow
NASA Astrophysics Data System (ADS)
Germaine, Emmanuel; Mydlarski, Laurent; Cortelezzi, Luca
2011-11-01
We analyze the mixing of a passive scalar (temperature) in a turbulent channel flow for different initial conditions by means of numerical simulations. The numerical domain is a channel delimited by two parallel and infinite flat walls, simulated using periodic boundary conditions in the streamwise and spanwise directions. We consider three initial distributions of temperature, where hot and cold fluids are separated by a sharp but continuous interface that subdivides the computational domain into two identical halves. The interface is taken parallel to the walls or perpendicular to them, oriented in the streamwise or spanwise directions. We perform a direct numerical simulation of the temperature field at Reτ = 190 when the flow is fully turbulent. The numerical scheme combines an advection diffusion solver, i.e, a third-order flux integral method based on UTOPIA (Leonard et al., Appl. Math. Modeling, 1995), with a Navier-Stokes solver, i.e, spectral code released by Prof. John Gibson, http://www.channelflow.org). We quantify the time-evolution of the mixing performance of the turbulent flow using different measures of the mixing, including a negative Sobolev norm - a diagnostic currently used to asses the mixing performance of laminar flows. Finally, we discuss the influence of the initial conditions on the turbulent mixing. Funding was provided by NSERC (grants RGPIN217169 and RGPIN217184).
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.
Improvement of Initial Conditions of Sea Fog Modeling with Cycling 3DVAR-WRF
NASA Astrophysics Data System (ADS)
Gao, S.; Fu, G.; Wu, W.; Xu, X.
2010-07-01
Among the seas of China, the Yellow Sea (YS) experiences sea fog most frequently, especially during the spring and summer seasons. Recent studies of sea fog modeling over YS have suggested that data assimilation is a key important issue for sea fog modeling, because simulation result is significantly sensitive to initial conditions. In this talk, a heavy sea fog over YS occurred from 6 to 7 March 2006 is carefully studied by using Weather Research and Forecasting (WRF) model. The evolution of sea fog area is demonstrated by the Multi-functional Transport Satellite (MTSAT)-1R visible imagery and infrared data using dual channel difference method. A cycling 3DVAR scheme with 12-h assimilation window is designed and employed to generate the initial conditions for this sea fog simulation. The result shows that the simulated sea fog area is greatly improved compared to the result without cycling 3DVAR. Additionally, the initial conditions with cycling 3DVAR-WRF are also used to force the Regional Atmospheric Modeling System (RAMS) model to simulate this sea fog case. We find that the simulated sea fog coverage is much better than the result with RAMS original isentropic analysis.
The initial representation in reasoning towards an interpretation of conditional sentences.
Schroyens, Walter; Braem, Senne
2011-02-01
All accounts of human reasoning (whether presented at the symbolic or subsymbolic level) have to reckon with the temporal organization of the human processing systems and the ephemeral nature of the representations it uses. We present three new empirical tests for the hypothesis that people commence the interpretational process by constructing a minimal initial representation. In the case of if A then C the initial representation captures the occurrence of the consequent, C, within the context of the antecedent, A. Conditional inference problems are created by a categorical premise that affirms or denies A or C. The initial representation allows an inference when the explicitly represented information matches (e.g., the categorical premise A affirms the antecedent "A") but not when it mismatches (e.g., "not-A" denies A). Experiments 1 and 2 confirmed that people tend to accept the conclusion that "nothing follows" for the denial problems, as indeed they do not have a determinate initial-model conclusion. Experiment 3 demonstrated the other way round that the effect of problem type (affirmation versus denial) is reduced when we impede the possibility of inferring a determinate conclusion on the basis of the initial representation of both the affirmation and the denial problems. PMID:21104563
NASA Astrophysics Data System (ADS)
Saliba, H. T.
1995-06-01
The practical engineering problem of right angled triangular plates with combinations of clamped and simply supported boundary conditions is dealt with in this paper. A highly accurate, economical and practical solution is used for the transverse free vibration analysis of these plates. The solution is based on a modified superposition method. The accuracy of the solution is discussed. Numerical results are compared with previously published reliable data. The advantages of the solution used in the paper over previously published solutions are discussed. Eigenvalues, mode shapes and contour plots are provided for a large number of plates.
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
Tensor to scalar ratio and large scale power suppression from pre-slow roll initial conditions
NASA Astrophysics Data System (ADS)
Lello, Louis; Boyanovsky, Daniel
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 Script Tα(k), Script Pα(k) = PBDα(k)Script Tα(k), implying a modification of the ``consistency condition'' for the tensor to scalar ratio at a pivot scale k0: r(k0) = -8nT(k0) [Script TT(k0)/Script TScript R(k0)]. We obtain Script Tα(k) to leading order in a Born approximation valid for modes of observational relevance today. A fit yields Script Tα(k) = 1+Aαk-pcos [2πωk/Hsr+varphiα], with 1.5lesssimplesssim2, ω simeq 1 and Hsr the Hubble scale during slow roll inflation, where curvature and tensor perturbations feature the same p,ω for a wide range of initial conditions. These corrections lead to both a suppression of the quadrupole and oscillatory features in both PR(k) and r(k0) 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 epsilonV, ηV to leading order in slow roll. For a wide range of κ and the values of epsilonV ηV corresponding to the upper bounds from Planck, we find that the low quadrupole is consistent with the results from Planck, and the oscillations in r(k0) as a function of k0 could
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
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.
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.
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
NASA Astrophysics Data System (ADS)
Jomaa, S.; Barry, D. A.; Brovelli, A.; Heng, B. C. P.; Sander, G. C.; Parlange, J.-Y.
2012-04-01
It is well known that the presence of rock fragments on the soil surface and the soil's initial characteristics (moisture content, surface roughness, bulk density, etc.) are key factors influencing soil erosion dynamics and sediment delivery. In addition, the interaction of these factors increases the complexity of soil erosion patterns and makes predictions more difficult. The aim of this study was (i) to investigate the effect of soil initial conditions and rock fragment coverage on soil erosion yields and effluent particle size distribution and (ii) to evaluate to what extent the rock fragment coverage controls this relationship. Three laboratory flume experiments with constant precipitation rate of 74 mm/h on a loamy soil parcel with a 2% slope were performed. Experiments with duration of 2 h were conducted using the 6-m × 2-m EPFL erosion flume. During each experiment two conditions were considered, a bare soil and a rock fragment-protected (with 40% coverage) soil. The initial soil surface state was varied between the three experiments, from a freshly re-ploughed and almost dry condition to a compacted soil with a well-developed shield layer and high moisture content. Experiments were designed so that rain splash was the primary driver of soil erosion. Results showed that the amount of eroded mass was highly controlled by the initial soil conditions and whether the steady-state equilibrium was un-, partially- or fully- developed during the previous event. Additionally, results revealed that sediment yields and particle size composition in the initial part of an erosion event are more sensitive to the erosion history than the long-time behaviour. This latter appears to be mainly controlled by rainfall intensity. If steady-state was achieved for a previous event, then the next event consistently produced concentrations for each size class that peaked rapidly, and then declined gradually to steady-state equilibrium. If steady state was not obtained, then
Evaluation of the effects of initial conditions on transients in PUMA
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.
Medicare's Bundled Payment initiative: most hospitals are focused on a few high-volume conditions.
Tsai, Thomas C; Joynt, Karen E; Wild, Robert C; Orav, E John; Jha, Ashish K
2015-03-01
The Bundled Payments for Care Improvement initiative is a federally funded innovation model mandated by the Affordable Care Act. It is designed to help transition Medicare away from fee-for-service payments and toward bundling a single payment for an episode of acute care in a hospital and related postacute care in an appropriate setting. While results from the initiative will not be available for several years, current data can help provide critical early insights. However, little is known about the participating organizations and how they are focusing their efforts. We identified participating hospitals and used national Medicare claims data to assess their characteristics and previous spending patterns. These hospitals are mostly large, nonprofit, teaching hospitals in the Northeast, and they have selectively enrolled in the bundled payment initiative covering patient conditions with high clinical volumes. We found no significant differences in episode-based spending between participating and nonparticipating hospitals. Postacute care explains the largest variation in overall episode-based spending, signaling an opportunity to align incentives across providers. However, the focus on a few selected clinical conditions and the high degree of integration that already exists between enrolled hospitals and postacute care providers may limit the generalizability of bundled payment across the Medicare system. PMID:25732486
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.
Lai, Yin-Hung; Wang, Chia-Chen; Chen, Chiu Wen; Liu, Bo-Hong; Lin, Sheng Hsien; Lee, Yuan Tseh; Wang, Yi-Sheng
2012-08-16
This investigation concerns the initial chemical reactions that affect the ionization of matrixes in matrix-assisted laser desorption/ionization (MALDI). The study focuses on the relaxations of photon energy that occur on a comparable time scale to that of ionization, in which the available laser energy is shared and the ionization condition is changed. The relaxations include fluorescence, fragmentation, and nonradiative relaxation from the excited state to the ground state. With high absorption cross section and long excited-state lifetime, photoionization of matrix plays an important role if sufficient laser energy is used. Under other conditions, thermal ionization of the molecule in the ground state is predicted to be one of the important reactions. Evidence of change in the branching ratio of initial reactions with the matrix and the excitation wavelength was obtained with α-cyano-4-hydroxycinnamic acid, sinapinic acid, 2,5-dihydroxybenzoic acid, and 2,4,6-trihydroxyacetophenone. These matrixes are studied by obtaining their mixed crystal absorption spectra, fluorescence properties, laser-induced infrared emission, and product ions. The exact ionization pathway depends on the chemical properties of matrixes and the excitation conditions. This concept may explain the diversity of experimental results observed in MALDI experiments, which provides an insight into the ensemble of chemical reactions that govern the generation of ions. PMID:22799495
Reduction of damage initiation density in fused silica optics via UV laser conditioning
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.
NASA Astrophysics Data System (ADS)
Choi, Dahan; Zhou, Chengzhe; Troian, Sandra
Molten nanofilms whose free surface is exposed to a flat cooled substrate held in close proximity are known to develop spontaneous arrays of nanopillars which undergo runaway growth. Comparison between experiment and predictions of linear stability analysis (LSA) in the long wavelength approximation suggests the instability is caused by runaway thermocapillary forces. In previous work, we have examined the influence of experimental parameters on the value of the wavelength characterizing the most unstable mode. In this talk, we explore the sensitivity of the interface equation to initial conditions comprising extended and compact, spatially inhomogeneous perturbations in film thickness. While early time formations always migrate toward the most unstable mode from LSA, late time patterns exhibit interesting mode-mixing behavior even for initial disturbances characterized by a small wavenumber, single mode pulse. DC gratefully acknowledges support from a Caltech Summer Research Undergraduate fellowship.
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.
2013-01-01
Background Although prokaryotic gene transcription has been studied over decades, many aspects of the process remain poorly understood. Particularly, recent studies have revealed that transcriptomes in many prokaryotes are far more complex than previously thought. Genes in an operon are often alternatively and dynamically transcribed under different conditions, and a large portion of genes and intergenic regions have antisense RNA (asRNA) and non-coding RNA (ncRNA) transcripts, respectively. Ironically, similar studies have not been conducted in the model bacterium E coli K12, thus it is unknown whether or not the bacterium possesses similar complex transcriptomes. Furthermore, although RNA-seq becomes the major method for analyzing the complexity of prokaryotic transcriptome, it is still a challenging task to accurately assemble full length transcripts using short RNA-seq reads. Results To fill these gaps, we have profiled the transcriptomes of E. coli K12 under different culture conditions and growth phases using a highly specific directional RNA-seq technique that can capture various types of transcripts in the bacterial cells, combined with a highly accurate and robust algorithm and tool TruHMM (http://bioinfolab.uncc.edu/TruHmm_package/) for assembling full length transcripts. We found that 46.9 ~ 63.4% of expressed operons were utilized in their putative alternative forms, 72.23 ~ 89.54% genes had putative asRNA transcripts and 51.37 ~ 72.74% intergenic regions had putative ncRNA transcripts under different culture conditions and growth phases. Conclusions As has been demonstrated in many other prokaryotes, E. coli K12 also has a highly complex and dynamic transcriptomes under different culture conditions and growth phases. Such complex and dynamic transcriptomes might play important roles in the physiology of the bacterium. TruHMM is a highly accurate and robust algorithm for assembling full-length transcripts in prokaryotes using directional RNA
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.
Importance of Granular Structure in the Initial Conditions for the Elliptic Flow
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.
How to impose initial conditions for QCD evolution of double parton distributions?
NASA Astrophysics Data System (ADS)
Golec-Biernat, Krzysztof; Lewandowska, Emilia
2014-07-01
Double parton distribution functions are used in the QCD description of double parton scattering. The double parton distributions evolve with hard scales through QCD evolution equations which obey nontrivial momentum and valence quark number sum rules. We describe an attempt to construct initial conditions for the evolution equations which exactly fulfill these sum rules and discuss its shortcomings. We also discuss the factorization of the double parton distributions into a product of two single parton distribution functions at small values of the parton momentum fractions.
Exact solution for four-order acousto-optic Bragg diffraction with arbitrary initial conditions.
Pieper, Ron; Koslover, Deborah; Poon, Ting-Chung
2009-03-01
An exact solution to the four-order acousto-optic (AO) Bragg diffraction problem with arbitrary initial conditions compatible with exact Bragg angle incident light is developed. The solution, obtained by solving a 4th-order differential equation, is formalized into a transition matrix operator predicting diffracted light orders at the exit of the AO cell in terms of the same diffracted light orders at the entrance. It is shown that the transition matrix is unitary and that this unitary matrix condition is sufficient to guarantee energy conservation. A comparison of analytical solutions with numerical predictions validates the formalism. Although not directly related to the approach used to obtain the solution, it was discovered that all four generated eigenvalues from the four-order AO differential matrix operator are expressed simply in terms of Euclid's Divine Proportion. PMID:19252607
INITIAL TEST WELL CONDITIONING AT NOPAL I URANIUM DEPOSIT, SIERRA PENA BLANCA, CHIHUAHUA, MEXICO
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
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.
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.
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.
Initial subjective reward: single-exposure conditioned place preference to alcohol in mice.
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
Initial subjective reward: single-exposure conditioned place preference to alcohol in mice
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
What initial condition of inflation would suppress the large-scale CMB spectrum?
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
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.
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.
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.
Reconstruction of Initial Beam Conditions at the Exit of the DARHT II Accelerator
NASA Astrophysics Data System (ADS)
Paul, Arthur
We consider a technique to determine the initial beam conditions of the DARHT II Accelerator by measuring the beam size under three different magnetic transport settings. This may be time gated to resolve the parameters as a function of time within the 2000 nsec pulse. This technique leads to three equations in three unknowns with solution giving the accelerator exit beam radius, tilt and emittance. We find that systematic errors cancel and so are not a problem in unfolding the initial beam conditions. Random uncorrelated shot to shot errors can be managed by one of three strategies: 1) make the transport system optically de-magnifying; 2) average over many individual shots; or 3) make the random uncorrelated shot to shot errors sufficiently small. The high power of the DARHT II beam requires that the beam transport system leading to a radius measuring apparatus be optically magnifying. This means that the shot to shot random errors must either be made small (less than about 1%) or that we average each of the three beam radius determinations over many individual shots.
Reconstruction of Initial Beam Conditions at the Exit of the DARHT II Accelerator
Paul, A.C.
2000-02-18
We consider a technique of determining the initial beam conditions of the DARHT II accelerator by measuring the beam size under three different magnetic transport settings. This may be time gated to resolve the parameters as a function of time within the 2000 nsec pulse. This technique leads to three equations in three unknowns with solution giving the accelerator exit beam radius, tilt, and emittance. We find that systematic errors cancel and so are not a problem in the initial beam condition unfolding. Random uncorrelated shot to shot errors can be managed by one of three strategies: (1) make the transport system optically de-magnifying; (2) average over many individual shots; or (3) make the random uncorrelated shot to shot errors sufficiently small. The high power of the DARHT II beam requires that the beam transport system leading to a radius measuring apparatus be optically magnifying. This means that the shot to shot random errors must either be made small (less than about 1%) or that we average each of the three beam radius determinations over many individual shots. We find that for the anticipated DARHT II beam parameters that 60 to 120 shots should be sufficient to determine the accelerator beam parameters.
Inverted initial conditions: Exploring the growth of cosmic structure and voids
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
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
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...
Tensor to scalar ratio and large scale power suppression from pre-slow roll initial conditions
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
Effects of initial condition spectral content on shock-driven turbulent mixing.
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
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.
Kwon, Sungchul; Kim, Jin Min
2015-12-01
For a fixed-energy (FE) Manna sandpile model in one dimension, we investigate the critical behavior for regular initial conditions in which activities are distributed at regular intervals on average. The FE Manna model conserves the density ρ of total particles and undergoes an absorbing phase transition at a critical ρ(c). For the regular initial conditions, we show via extensive simulations that the dynamical scaling behaviors differ from those of the random and the natural initial conditions. Off-critical scaling exponents β and ν(⊥) are also measured and shown to agree well with the values of the directed percolation (DP) class as reported by Basu et al. [Phys. Rev. Lett. 109, 015702 (2012)]. Our results suggest that the dynamical scaling behaviors depend on the characteristics of initial conditions, but the off-critical scaling behaviors in the steady state are independent of initial conditions and belong to the DP class. PMID:26764674
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
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
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.
Fang, Ruihua; Elias, Dwayne A.; Monroe, Matthew E.; Shen, Yufeng; McIntosh, Martin; Wang, Pei; Goddard, Carrie D.; Callister, Stephen J.; Moore, Ronald J.; Gorby, Yuri A.; Adkins, Joshua N.; Fredrickson, Jim K.; Lipton, Mary S.; Smith, Richard D.
2006-04-01
We describe the application of liquid chromatography coupled to mass spectrometry (LC/MS) without the use of stable isotope labeling for differential quantitative proteomics analysis of whole cell lysates of Shewanella oneidensis MR-1 cultured under aerobic and sub-oxic conditions. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to initially identify peptide sequences, and LC coupled to Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR) was used to confirm these identifications, as well as measure relative peptide abundances. 2343 peptides, covering 668 proteins were identified with high confidence and quantified. Among these proteins, a subset of 56 changed significantly using statistical approaches such as SAM, while another subset of 56 that were annotated as performing housekeeping functions remained essentially unchanged in relative abundance. Numerous proteins involved in anaerobic energy metabolism exhibited up to a 10-fold increase in relative abundance when S. oneidensis is transitioned from aerobic to sub-oxic conditions.
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.
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.
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.
INITIAL CHEMICAL AND RESERVOIR CONDITIONS AT LOS AZUFRES WELLHEAD POWER PLANT STARTUP
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.
Sensitivity of Initial Conditions on Diurnal Variability of Indian Summer Monsoon
NASA Astrophysics Data System (ADS)
Das, Sukanta Kumar; Deb, Sanjib Kumar; Kishtawal, C. M.; Pal, Pradip Kumar
2015-10-01
The diurnal cycle of different surface parameters, viz. surface air temperature, surface pressure, and rain intensities, simulated by the Community Atmosphere Model (CAM) in the operational seasonal forecast of ISM-2012 using initial conditions (ICs) taken at synoptic hours of the day has been examined and compared with observations. Four members were simulated with ICs at 0000, 0600, 1200, and 1800 UTC on 1 August 2012. The impact of the initial conditions at the synoptic hours of the day was more visible over the landmass compared with the oceanic regions. The diurnal variation of the surface temperature in the model simulation showed the major features when compared with the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis except for the warm pool of northwest India and the Tibetan region. The surface pressure in the ECMWF reanalysis showed the semidiurnal cycle with two peaks at 0600 UTC and 1800 UTC; however, the range of the cycle was underestimated by the model simulation, showing only one peak at 0600 UTC. Significant variations in the diurnal cycle of rain intensities were seen among the different members. The model captured the diurnal cycle as the positive and negative peaks at 1200 and 0000 UTC with intensities at the peaks ~0.5 mm high and low, respectively, in the model simulation when compared with the observations. Presently, the seasonal forecast of ISM is generated through ensemble CAM experiments using different ICs taken from different dates but all at 0000 UTC. Consideration of ICs at different times of the day will add different ranges of diurnal variations in all the surface parameters within the family of ensemble members and also increase the number of members in the family. Indeed, these improve the ensemble processes in generating the seasonal forecast of ISM.
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.
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
Guo, Hengkai; Wang, Guijin; Huang, Lingyun; Hu, Yuxin; Yuan, Chun; Li, Rui; Zhao, Xihai
2016-01-01
Atherosclerosis is among the leading causes of death and disability. Combining information from multi-modal vascular images is an effective and efficient way to diagnose and monitor atherosclerosis, in which image registration is a key technique. In this paper a feature-based registration algorithm, Two-step Auto-labeling Conditional Iterative Closed Points (TACICP) algorithm, is proposed to align three-dimensional carotid image datasets from ultrasound (US) and magnetic resonance (MR). Based on 2D segmented contours, a coarse-to-fine strategy is employed with two steps: rigid initialization step and non-rigid refinement step. Conditional Iterative Closest Points (CICP) algorithm is given in rigid initialization step to obtain the robust rigid transformation and label configurations. Then the labels and CICP algorithm with non-rigid thin-plate-spline (TPS) transformation model is introduced to solve non-rigid carotid deformation between different body positions. The results demonstrate that proposed TACICP algorithm has achieved an average registration error of less than 0.2mm with no failure case, which is superior to the state-of-the-art feature-based methods. PMID:26881433
Development of the BWR Dry Core Initial and Boundary Conditions for the SNL XR2 Experiments
Ott, L.J.
1994-01-01
The objectives of the Boiling Water Reactor Experimental Analysis and Model Development for Severe Accidents (BEAMD) Program at the Oak Ridge National Laboratory (ORNL) are: (1) the development of a sound quantitative understanding of boiling water reactor (BWR) core melt progression; this includes control blade and channel box effects, metallic melt relocation and possible blockage formation under severe accident conditions, and (2) provision of BWR melt progression modeling capabilities in SCDAP/RELAP5 (consistent with the BWR experimental data base). This requires the assessment of current modeling of BWR core melt progression against the expanding BWR data base. Emphasis is placed upon data from the BWR tests in the German CORA test facility and from the ex-reactor experiments [Sandia National Laboratories (SNL)] on metallic melt relocation and blockage formation in BWRs, as well as upon in-reactor data from the Annular Core Research Reactor (ACRR) DF-4 BWR test (conducted in 1986 at SNL). The BEAMD Program is a derivative of the BWR Severe Accident Technology Programs at ORNL. The ORNL BWR programs have studied postulated severe accidents in BWRs and have developed a set of models specific to boiling water reactor response under severe accident conditions. These models, in an experiment-specific format, have been successfully applied to both pretest and posttest analyses of the DF-4 experiment, and the BWR severe fuel damage (SFD) experiments performed in the CORA facility at the Kernforschungszentrum Karlsruhe (KfK) in Germany, resulting in excellent agreement between model prediction and experiment. The ORNL BWR models have provided for more precise predictions of the conditions in the BWR experiments than were previously available. This has provided a basis for more accurate interpretation of the phenomena for which the experiments are performed. The experiment-specific models, as used in the ORNL DF-4 and CORA BWR experimental analyses, also provide a
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
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