Traveling Weather Disturbances in Mars' Southern Extratropics: Sway of the Great Impact Basins

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.

2016-04-01

As on Earth, between late autumn and early spring on Mars middle and high latitudes within its atmosphere support strong mean thermal contrasts between the equator and poles (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Within a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, such large-scale, extratropical weather disturbances are critical components of the global circulation. These wave-like disturbances act as agents in the transport of heat and momentum, and moreover generalized tracer quantities (e.g., atmospheric dust, water vapor and water-ice clouds) between low and high latitudes of the planet. The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (Mars GCM). This global circulation model imposes interactively lifted (and radiatively active) dust based on a threshold value of the instantaneous surface stress. Compared to observations, the model exhibits a reasonable "dust cycle" (i.e., globally averaged, a more dusty atmosphere during southern spring and summer occurs). In contrast to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense synoptically. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather disturbances are examined. Simulations that adapt Mars' full topography compared to simulations that utilize synthetic topographies emulating essential large-scale features of the southern middle latitudes indicate that Mars' transient barotropic/baroclinic eddies are significantly influenced by the great impact basins of this hemisphere (e.g., Argyre and Hellas). In addition, the occurrence of a southern storm zone in late winter and early spring is keyed particularly to the western hemisphere via orographic influences arising from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate fundamental differences amongst such simulations and these are described.

Dynamic structural disorder in supported nanoscale catalysts

NASA Astrophysics Data System (ADS)

Rehr, J. J.; Vila, F. D.

2014-04-01

We investigate the origin and physical effects of "dynamic structural disorder" (DSD) in supported nano-scale catalysts. DSD refers to the intrinsic fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to bulk materials, nano-scale systems exhibit substantial fluctuations in structure, charge, temperature, and other quantities, as well as large surface effects. The DSD is driven largely by the stochastic librational motion of the center of mass and fluxional bonding at the nanoparticle surface due to thermal coupling with the substrate. Our approach for calculating and understanding DSD is based on a combination of real-time density functional theory/molecular dynamics simulations, transient coupled-oscillator models, and statistical mechanics. This approach treats thermal and dynamic effects over multiple time-scales, and includes bond-stretching and -bending vibrations, and transient tethering to the substrate at longer ps time-scales. Potential effects on the catalytic properties of these clusters are briefly explored. Model calculations of molecule-cluster interactions and molecular dissociation reaction paths are presented in which the reactant molecules are adsorbed on the surface of dynamically sampled clusters. This model suggests that DSD can affect both the prefactors and distribution of energy barriers in reaction rates, and thus can significantly affect catalytic activity at the nano-scale.

Reduction of adenovirus E1A mRNA by RNAi results in enhanced recombinant protein expression in transiently transfected HEK293 cells.

PubMed

Hacker, David L; Bertschinger, Martin; Baldi, Lucia; Wurm, Florian M

2004-10-27

Human embryonic kidney 293 (HEK293) cells, a widely used host for large-scale transient expression of recombinant proteins, are transformed with the adenovirus E1A and E1B genes. Because the E1A proteins function as transcriptional activators or repressors, they may have a positive or negative effect on transient transgene expression in this cell line. Suspension cultures of HEK293 EBNA (HEK293E) cells were co-transfected with a reporter plasmid expressing the GFP gene and a plasmid expressing a short hairpin RNA (shRNA) targeting the E1A mRNAs for degradation by RNA interference (RNAi). The presence of the shRNA in HEK293E cells reduced the steady state level of E1A mRNA up to 75% and increased transient GFP expression from either the elongation factor-1alpha (EF-1alpha) promoter or the human cytomegalovirus (HCMV) immediate early promoter up to twofold. E1A mRNA depletion also resulted in a twofold increase in transient expression of a recombinant IgG in both small- and large-scale suspension cultures when the IgG light and heavy chain genes were controlled by the EF-1alpha promoter. Finally, transient IgG expression was enhanced 2.5-fold when the anti-E1A shRNA was expressed from the same vector as the IgG light chain gene. These results demonstrated that E1A has a negative effect on transient gene expression in HEK293E cells, and they established that RNAi can be used to enhance recombinant protein expression in mammalian cells.

Fault-Tolerant Sequencer Using FPGA-Based Logic Designs for Space Applications

DTIC Science & Technology

2013-12-01

Prototype Board SBU single bit upset SDK software development kit SDRAM synchronous dynamic random-access memory SEB single-event burnout ...current VHDL VHSIC hardware description language VHSIC very-high-speed integrated circuits VLSI very-large- scale integration VQFP very...transient pulse, called a single-event transient (SET), or even cause permanent damage to the device in the form of a burnout or gate rupture. The SEE

Heat Source Characterization In A TREAT Fuel Particle Using Coupled Neutronics Binary Collision Monte-Carlo Calculations

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

Schunert, Sebastian; Schwen, Daniel; Ghassemi, Pedram

This work presents a multi-physics, multi-scale approach to modeling the Transient Test Reactor (TREAT) currently prepared for restart at the Idaho National Laboratory. TREAT fuel is made up of microscopic fuel grains (r ˜ 20µm) dispersed in a graphite matrix. The novelty of this work is in coupling a binary collision Monte-Carlo (BCMC) model to the Finite Element based code Moose for solving a microsopic heat-conduction problem whose driving source is provided by the BCMC model tracking fission fragment energy deposition. This microscopic model is driven by a transient, engineering scale neutronics model coupled to an adiabatic heating model. Themore » macroscopic model provides local power densities and neutron energy spectra to the microscpic model. Currently, no feedback from the microscopic to the macroscopic model is considered. TREAT transient 15 is used to exemplify the capabilities of the multi-physics, multi-scale model, and it is found that the average fuel grain temperature differs from the average graphite temperature by 80 K despite the low-power transient. The large temperature difference has strong implications on the Doppler feedback a potential LEU TREAT core would see, and it underpins the need for multi-physics, multi-scale modeling of a TREAT LEU core.« less

Flow field topology of transient mixing driven by buoyancy

NASA Technical Reports Server (NTRS)

Duval, Walter M B.

2004-01-01

Transient mixing driven by buoyancy occurs through the birth of a symmetric Rayleigh-Taylor morphology (RTM) structure for large length scales. Beyond its critical bifurcation the RTM structure exhibits self-similarity and occurs on smaller and smaller length scales. The dynamics of the RTM structure, its nonlinear growth and internal collision, show that its genesis occurs from an explosive bifurcation which leads to the overlap of resonance regions in phase space. This event shows the coexistence of regular and chaotic regions in phase space which is corroborated with the existence of horseshoe maps. A measure of local chaos given by the topological entropy indicates that as the system evolves there is growth of uncertainty. Breakdown of the dissipative RTM structure occurs during the transition from explosive to catastrophic bifurcation; this event gives rise to annihilation of the separatrices which drives overlap of resonance regions. The global bifurcation of explosive and catastrophic events in phase space for the large length scale of the RTM structure serves as a template for which mixing occurs on smaller and smaller length scales. Copyright 2004 American Institute of Physics.

A rapid, highly efficient and economical method of Agrobacterium-mediated in planta transient transformation in living onion epidermis.

PubMed

Xu, Kedong; Huang, Xiaohui; Wu, Manman; Wang, Yan; Chang, Yunxia; Liu, Kun; Zhang, Ju; Zhang, Yi; Zhang, Fuli; Yi, Liming; Li, Tingting; Wang, Ruiyue; Tan, Guangxuan; Li, Chengwei

2014-01-01

Transient transformation is simpler, more efficient and economical in analyzing protein subcellular localization than stable transformation. Fluorescent fusion proteins were often used in transient transformation to follow the in vivo behavior of proteins. Onion epidermis, which has large, living and transparent cells in a monolayer, is suitable to visualize fluorescent fusion proteins. The often used transient transformation methods included particle bombardment, protoplast transfection and Agrobacterium-mediated transformation. Particle bombardment in onion epidermis was successfully established, however, it was expensive, biolistic equipment dependent and with low transformation efficiency. We developed a highly efficient in planta transient transformation method in onion epidermis by using a special agroinfiltration method, which could be fulfilled within 5 days from the pretreatment of onion bulb to the best time-point for analyzing gene expression. The transformation conditions were optimized to achieve 43.87% transformation efficiency in living onion epidermis. The developed method has advantages in cost, time-consuming, equipment dependency and transformation efficiency in contrast with those methods of particle bombardment in onion epidermal cells, protoplast transfection and Agrobacterium-mediated transient transformation in leaf epidermal cells of other plants. It will facilitate the analysis of protein subcellular localization on a large scale.

Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects

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

Ye, Sheng; Covino, Timothy P.; Sivapalan, Murugesu

In this paper, we use a dynamic network flow model, coupled with a transient storage zone biogeochemical model, to simulate dissolved nutrient removal processes at the channel network scale. We have explored several scenarios in respect of the combination of rainfall variability, and the biological and geomorphic characteristics of the catchment, to understand the dominant controls on removal and delivery of dissolved nutrients (e.g., nitrate). These model-based theoretical analyses suggested that while nutrient removal efficiency is lower during flood events compared to during baseflow periods, flood events contribute significantly to bulk nutrient removal, whereas bulk removal during baseflow periods ismore » less. This is due to the fact that nutrient supply is larger during flood events; this trend is even stronger in large rivers. However, the efficiency of removal during both periods decreases in larger rivers, however, due to (i) increasing flow velocities and thus decreasing residence time, and (ii) increasing flow depth, and thus decreasing nutrient uptake rates. Besides nutrient removal processes can be divided into two parts: in the main channel and in the hyporheic transient storage zone. When assessing their relative contributions the size of the transient storage zone is a dominant control, followed by uptake rates in the main channel and in the transient storage zone. Increasing size of the transient storage zone with downstream distance affects the relative contributions to nutrient removal of the water column and the transient storage zone, which also impacts the way nutrient removal rates scale with increasing size of rivers. Intra-annual hydrologic variability has a significant impact on removal rates at all scales: the more variable the streamflow is, compared to mean discharge, the less nutrient is removed in the channel network. A scale-independent first order uptake coefficient, ke, estimated from model simulations, is highly dependent on the relative size of the transient storage zone and how it changes in the downstream direction, as well as the nature of hydrologic variability.« less

Understanding of Particle Acceleration by Foreshock Transients (invited)

NASA Astrophysics Data System (ADS)

Liu, T. Z.; Angelopoulos, V.; Hietala, H.; Lu, S.; Wilson, L. B., III

2017-12-01

Although plasma shocks are known to be a major particle accelerator at Earth's environment (e.g., the bow shock) and elsewhere in the universe, how particles are accelerated to very large energies compared to the shock potential is still not fully understood. Significant new information on such acceleration in the vicinity of Earth's bow shock has recently emerged due to the availability of multi-point observations, in particular from Cluster and THEMIS. These have revealed numerous types of foreshock transients, formed by shock-reflected ions, which could play a crucial role in particle pre-acceleration, i.e. before the particles reach the shock to be subjected again to even further acceleration. Foreshock bubbles (FBs) and hot flow anomalies (HFAs), are a subset of such foreshock transients that are especially important due to their large spatial scale (1-10 Earth radii), and their ability to have global effects at Earth.s geospace. These transients can accelerate particles that can become a particle source for the parent shock. Here we introduce our latest progress in understanding particle acceleration by foreshock transients including their statistical characteristics and acceleration mechanisms.

Understanding of Particle Acceleration by Foreshock Transients

NASA Astrophysics Data System (ADS)

Liu, T. Z.; Angelopoulos, V.; Hietala, H.; Lu, S.; Wilson, L. B., III

2017-12-01

Although plasma shocks are known to be a major particle accelerator at Earth's environment (e.g., the bow shock) and elsewhere in the universe, how particles are accelerated to very large energies compared to the shock potential is still not fully understood. Significant new information on such acceleration in the vicinity of Earth's bow shock has recently emerged due to the availability of multi-point observations, in particular from Cluster and THEMIS. These have revealed numerous types of foreshock transients, formed by shock-reflected ions, which could play a crucial role in particle pre-acceleration, i.e. before the particles reach the shock to be subjected again to even further acceleration. Foreshock bubbles (FBs) and hot flow anomalies (HFAs), are a subset of such foreshock transients that are especially important due to their large spatial scale (1-10 Earth radii), and their ability to have global effects at Earth's geospace. These transients can accelerate particles that can become a particle source for the parent shock. Here we introduce our latest progress in understanding particle acceleration by foreshock transients including their statistical characteristics and acceleration mechanisms.

Regional climate model sensitivity to domain size

NASA Astrophysics Data System (ADS)

Leduc, Martin; Laprise, René

2009-05-01

Regional climate models are increasingly used to add small-scale features that are not present in their lateral boundary conditions (LBC). It is well known that the limited area over which a model is integrated must be large enough to allow the full development of small-scale features. On the other hand, integrations on very large domains have shown important departures from the driving data, unless large scale nudging is applied. The issue of domain size is studied here by using the “perfect model” approach. This method consists first of generating a high-resolution climatic simulation, nicknamed big brother (BB), over a large domain of integration. The next step is to degrade this dataset with a low-pass filter emulating the usual coarse-resolution LBC. The filtered nesting data (FBB) are hence used to drive a set of four simulations (LBs for Little Brothers), with the same model, but on progressively smaller domain sizes. The LB statistics for a climate sample of four winter months are compared with BB over a common region. The time average (stationary) and transient-eddy standard deviation patterns of the LB atmospheric fields generally improve in terms of spatial correlation with the reference (BB) when domain gets smaller. The extraction of the small-scale features by using a spectral filter allows detecting important underestimations of the transient-eddy variability in the vicinity of the inflow boundary, which can penalize the use of small domains (less than 100 × 100 grid points). The permanent “spatial spin-up” corresponds to the characteristic distance that the large-scale flow needs to travel before developing small-scale features. The spin-up distance tends to grow in size at higher levels in the atmosphere.

Revealing the cluster of slow transients behind a large slow slip event.

PubMed

Frank, William B; Rousset, Baptiste; Lasserre, Cécile; Campillo, Michel

2018-05-01

Capable of reaching similar magnitudes to large megathrust earthquakes [ M w (moment magnitude) > 7], slow slip events play a major role in accommodating tectonic motion on plate boundaries through predominantly aseismic rupture. We demonstrate here that large slow slip events are a cluster of short-duration slow transients. Using a dense catalog of low-frequency earthquakes as a guide, we investigate the M w 7.5 slow slip event that occurred in 2006 along the subduction interface 40 km beneath Guerrero, Mexico. We show that while the long-period surface displacement, as recorded by Global Positioning System, suggests a 6-month duration, the motion in the direction of tectonic release only sporadically occurs over 55 days, and its surface signature is attenuated by rapid relocking of the plate interface. Our proposed description of slow slip as a cluster of slow transients forces us to re-evaluate our understanding of the physics and scaling of slow earthquakes.

Rossby waves and two-dimensional turbulence in a large-scale zonal jet

NASA Technical Reports Server (NTRS)

Shepherd, Theodor G.

1987-01-01

Homogeneous barotropic beta-plane turbulence is investigated, taking into account the effects of spatial inhomogeneity in the form of a zonal shear flows. Attention is given to the case of zonal flows that are barotropically stable and of larger scale than the resulting transient eddy field. Numerical simulations reveal that large-scale zonal flows alter the picture of classical beta-plane turbulence. It is found that the disturbance field penetrates to the largest scales of motion, that the larger disturbance scales show a tendency to meridional rather than zonal anisotropy, and that the initial spectral transfer rate away from an isotropic intermediate-scale source is enhanced by the shear-induced transfer associated with straining by the zonal flow.

Static Analysis of Large-Scale Multibody System Using Joint Coordinates and Spatial Algebra Operator

PubMed Central

Omar, Mohamed A.

2014-01-01

Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations. PMID:25045732

High-efficiency Agrobacterium-mediated transformation of Norway spruce (Picea abies) and loblolly pine (Pinus taeda)

NASA Technical Reports Server (NTRS)

Wenck, A. R.; Quinn, M.; Whetten, R. W.; Pullman, G.; Sederoff, R.; Brown, C. S. (Principal Investigator)

1999-01-01

Agrobacterium-mediated gene transfer is the method of choice for many plant biotechnology laboratories; however, large-scale use of this organism in conifer transformation has been limited by difficult propagation of explant material, selection efficiencies and low transformation frequency. We have analyzed co-cultivation conditions and different disarmed strains of Agrobacterium to improve transformation. Additional copies of virulence genes were added to three common disarmed strains. These extra virulence genes included either a constitutively active virG or extra copies of virG and virB, both from pTiBo542. In experiments with Norway spruce, we increased transformation efficiencies 1000-fold from initial experiments where little or no transient expression was detected. Over 100 transformed lines expressing the marker gene beta-glucuronidase (GUS) were generated from rapidly dividing embryogenic suspension-cultured cells co-cultivated with Agrobacterium. GUS activity was used to monitor transient expression and to further test lines selected on kanamycin-containing medium. In loblolly pine, transient expression increased 10-fold utilizing modified Agrobacterium strains. Agrobacterium-mediated gene transfer is a useful technique for large-scale generation of transgenic Norway spruce and may prove useful for other conifer species.

Static analysis of large-scale multibody system using joint coordinates and spatial algebra operator.

PubMed

Omar, Mohamed A

2014-01-01

Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations.

A note on conservative transport in anisotropic, heterogeneous porous media in the presence of small-amplitude transients

USGS Publications Warehouse

Naff, R.L.

1998-01-01

The late-time macrodispersion coefficients are obtained for the case of flow in the presence of a small-scale deterministic transient in a three-dimensional anisotropic, heterogeneous medium. The transient is assumed to affect only the velocity component transverse to the mean flow direction and to take the form of a periodic function. For the case of a highly stratified medium, these late-time macrodispersion coefficients behave largely as the standard coefficients used in the transport equation. Only in the event that the medium is isotropic is it probable that significant deviations from the standard coefficients would occur.

A Rapid, Highly Efficient and Economical Method of Agrobacterium-Mediated In planta Transient Transformation in Living Onion Epidermis

PubMed Central

Xu, Kedong; Huang, Xiaohui; Wu, Manman; Wang, Yan; Chang, Yunxia; Liu, Kun; Zhang, Ju; Zhang, Yi; Zhang, Fuli; Yi, Liming; Li, Tingting; Wang, Ruiyue; Tan, Guangxuan; Li, Chengwei

2014-01-01

Transient transformation is simpler, more efficient and economical in analyzing protein subcellular localization than stable transformation. Fluorescent fusion proteins were often used in transient transformation to follow the in vivo behavior of proteins. Onion epidermis, which has large, living and transparent cells in a monolayer, is suitable to visualize fluorescent fusion proteins. The often used transient transformation methods included particle bombardment, protoplast transfection and Agrobacterium-mediated transformation. Particle bombardment in onion epidermis was successfully established, however, it was expensive, biolistic equipment dependent and with low transformation efficiency. We developed a highly efficient in planta transient transformation method in onion epidermis by using a special agroinfiltration method, which could be fulfilled within 5 days from the pretreatment of onion bulb to the best time-point for analyzing gene expression. The transformation conditions were optimized to achieve 43.87% transformation efficiency in living onion epidermis. The developed method has advantages in cost, time-consuming, equipment dependency and transformation efficiency in contrast with those methods of particle bombardment in onion epidermal cells, protoplast transfection and Agrobacterium-mediated transient transformation in leaf epidermal cells of other plants. It will facilitate the analysis of protein subcellular localization on a large scale. PMID:24416168

Analysis of passive scalar advection in parallel shear flows: Sorting of modes at intermediate time scales

NASA Astrophysics Data System (ADS)

Camassa, Roberto; McLaughlin, Richard M.; Viotti, Claudio

2010-11-01

The time evolution of a passive scalar advected by parallel shear flows is studied for a class of rapidly varying initial data. Such situations are of practical importance in a wide range of applications from microfluidics to geophysics. In these contexts, it is well-known that the long-time evolution of the tracer concentration is governed by Taylor's asymptotic theory of dispersion. In contrast, we focus here on the evolution of the tracer at intermediate time scales. We show how intermediate regimes can be identified before Taylor's, and in particular, how the Taylor regime can be delayed indefinitely by properly manufactured initial data. A complete characterization of the sorting of these time scales and their associated spatial structures is presented. These analytical predictions are compared with highly resolved numerical simulations. Specifically, this comparison is carried out for the case of periodic variations in the streamwise direction on the short scale with envelope modulations on the long scales, and show how this structure can lead to "anomalously" diffusive transients in the evolution of the scalar onto the ultimate regime governed by Taylor dispersion. Mathematically, the occurrence of these transients can be viewed as a competition in the asymptotic dominance between large Péclet (Pe) numbers and the long/short scale aspect ratios (LVel/LTracer≡k), two independent nondimensional parameters of the problem. We provide analytical predictions of the associated time scales by a modal analysis of the eigenvalue problem arising in the separation of variables of the governing advection-diffusion equation. The anomalous time scale in the asymptotic limit of large k Pe is derived for the short scale periodic structure of the scalar's initial data, for both exactly solvable cases and in general with WKBJ analysis. In particular, the exactly solvable sawtooth flow is especially important in that it provides a short cut to the exact solution to the eigenvalue problem for the physically relevant vanishing Neumann boundary conditions in linear-shear channel flow. We show that the life of the corresponding modes at large Pe for this case is shorter than the ones arising from shear free zones in the fluid's interior. A WKBJ study of the latter modes provides a longer intermediate time evolution. This part of the analysis is technical, as the corresponding spectrum is dominated by asymptotically coalescing turning points in the limit of large Pe numbers. When large scale initial data components are present, the transient regime of the WKBJ (anomalous) modes evolves into one governed by Taylor dispersion. This is studied by a regular perturbation expansion of the spectrum in the small wavenumber regimes.

HIRAX: a probe of dark energy and radio transients

NASA Astrophysics Data System (ADS)

Newburgh, L. B.; Bandura, K.; Bucher, M. A.; Chang, T.-C.; Chiang, H. C.; Cliche, J. F.; Davé, R.; Dobbs, M.; Clarkson, C.; Ganga, K. M.; Gogo, T.; Gumba, A.; Gupta, N.; Hilton, M.; Johnstone, B.; Karastergiou, A.; Kunz, M.; Lokhorst, D.; Maartens, R.; Macpherson, S.; Mdlalose, M.; Moodley, K.; Ngwenya, L.; Parra, J. M.; Peterson, J.; Recnik, O.; Saliwanchik, B.; Santos, M. G.; Sievers, J. L.; Smirnov, O.; Stronkhorst, P.; Taylor, R.; Vanderlinde, K.; Van Vuuren, G.; Weltman, A.; Witzemann, A.

2016-08-01

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new 400{800MHz radio interferometer under development for deployment in South Africa. HIRAX will comprise 1024 six meter parabolic dishes on a compact grid and will map most of the southern sky over the course of four years. HIRAX has two primary science goals: to constrain Dark Energy and measure structure at high redshift, and to study radio transients and pulsars. HIRAX will observe unresolved sources of neutral hydrogen via their redshifted 21-cm emission line (`hydrogen intensity mapping'). The resulting maps of large-scale structure at redshifts 0.8{2.5 will be used to measure Baryon Acoustic Oscillations (BAO). BAO are a preferential length scale in the matter distribution that can be used to characterize the expansion history of the Universe and thus understand the properties of Dark Energy. HIRAX will improve upon current BAO measurements from galaxy surveys by observing a larger cosmological volume (larger in both survey area and redshift range) and by measuring BAO at higher redshift when the expansion of the universe transitioned to Dark Energy domination. HIRAX will complement CHIME, a hydrogen intensity mapping experiment in the Northern Hemisphere, by completing the sky coverage in the same redshift range. HIRAX's location in the Southern Hemisphere also allows a variety of cross-correlation measurements with large-scale structure surveys at many wavelengths. Daily maps of a few thousand square degrees of the Southern Hemisphere, encompassing much of the Milky Way galaxy, will also open new opportunities for discovering and monitoring radio transients. The HIRAX correlator will have the ability to rapidly and efficiently detect transient events. This new data will shed light on the poorly understood nature of fast radio bursts (FRBs), enable pulsar monitoring to enhance long-wavelength gravitational wave searches, and provide a rich data set for new radio transient phenomena searches. This paper discusses the HIRAX instrument, science goals, and current status.

Transient Structures and Possible Limits of Data Recording in Phase-Change Materials.

PubMed

Hu, Jianbo; Vanacore, Giovanni M; Yang, Zhe; Miao, Xiangshui; Zewail, Ahmed H

2015-07-28

Phase-change materials (PCMs) represent the leading candidates for universal data storage devices, which exploit the large difference in the physical properties of their transitional lattice structures. On a nanoscale, it is fundamental to determine their performance, which is ultimately controlled by the speed limit of transformation among the different structures involved. Here, we report observation with atomic-scale resolution of transient structures of nanofilms of crystalline germanium telluride, a prototypical PCM, using ultrafast electron crystallography. A nonthermal transformation from the initial rhombohedral phase to the cubic structure was found to occur in 12 ps. On a much longer time scale, hundreds of picoseconds, equilibrium heating of the nanofilm is reached, driving the system toward amorphization, provided that high excitation energy is invoked. These results elucidate the elementary steps defining the structural pathway in the transformation of crystalline-to-amorphous phase transitions and describe the essential atomic motions involved when driven by an ultrafast excitation. The establishment of the time scales of the different transient structures, as reported here, permits determination of the possible limit of performance, which is crucial for high-speed recording applications of PCMs.

The Zwicky Transient Facility Camera

NASA Astrophysics Data System (ADS)

Dekany, Richard; Smith, Roger M.; Belicki, Justin; Delacroix, Alexandre; Duggan, Gina; Feeney, Michael; Hale, David; Kaye, Stephen; Milburn, Jennifer; Murphy, Patrick; Porter, Michael; Reiley, Daniel J.; Riddle, Reed L.; Rodriguez, Hector; Bellm, Eric C.

2016-08-01

The Zwicky Transient Facility Camera (ZTFC) is a key element of the ZTF Observing System, the integrated system of optoelectromechanical instrumentation tasked to acquire the wide-field, high-cadence time-domain astronomical data at the heart of the Zwicky Transient Facility. The ZTFC consists of a compact cryostat with large vacuum window protecting a mosaic of 16 large, wafer-scale science CCDs and 4 smaller guide/focus CCDs, a sophisticated vacuum interface board which carries data as electrical signals out of the cryostat, an electromechanical window frame for securing externally inserted optical filter selections, and associated cryo-thermal/vacuum system support elements. The ZTFC provides an instantaneous 47 deg2 field of view, limited by primary mirror vignetting in its Schmidt telescope prime focus configuration. We report here on the design and performance of the ZTF CCD camera cryostat and report results from extensive Joule-Thompson cryocooler tests that may be of broad interest to the instrumentation community.

THETRIS: A MICRO-SCALE TEMPERATURE AND GAS RELEASE MODEL FOR TRISO FUEL

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

J. Ortensi; A.M. Ougouag

2011-12-01

The dominating mechanism in the passive safety of gas-cooled, graphite-moderated, high-temperature reactors (HTRs) is the Doppler feedback effect. These reactor designs are fueled with sub-millimeter sized kernels formed into TRISO particles that are imbedded in a graphite matrix. The best spatial and temporal representation of the feedback effect is obtained from an accurate approximation of the fuel temperature. Most accident scenarios in HTRs are characterized by large time constants and slow changes in the fuel and moderator temperature fields. In these situations a meso-scale, pebble and compact scale, solution provides a good approximation of the fuel temperature. Micro-scale models aremore » necessary in order to obtain accurate predictions in faster transients or when parameters internal to the TRISO are needed. Since these coated particles constitute one of the fundamental design barriers for the release of fission products, it becomes important to understand the transient behavior inside this containment system. An explicit TRISO fuel temperature model named THETRIS has been developed and incorporated into the CYNOD-THERMIX-KONVEK suite of coupled codes. The code includes gas release models that provide a simple predictive capability of the internal pressure during transients. The new model yields similar results to those obtained with other micro-scale fuel models, but with the added capability to analyze gas release, internal pressure buildup, and effects of a gap in the TRISO. The analyses show the instances when the micro-scale models improve the predictions of the fuel temperature and Doppler feedback. In addition, a sensitivity study of the potential effects on the transient behavior of high-temperature reactors due to the presence of a gap is included. Although the formation of a gap occurs under special conditions, its consequences on the dynamic behavior of the reactor can cause unexpected responses during fast transients. Nevertheless, the strong Doppler feedback forces the reactor to quickly stabilize.« less

Animal component-free Agrobacterium tumefaciens cultivation media for better GMP-compliance increases biomass yield and pharmaceutical protein expression in Nicotiana benthamiana.

PubMed

Houdelet, Marcel; Galinski, Anna; Holland, Tanja; Wenzel, Kathrin; Schillberg, Stefan; Buyel, Johannes Felix

2017-04-01

Transient expression systems allow the rapid production of recombinant proteins in plants. Such systems can be scaled up to several hundred kilograms of biomass, making them suitable for the production of pharmaceutical proteins required at short notice, such as emergency vaccines. However, large-scale transient expression requires the production of recombinant Agrobacterium tumefaciens strains with the capacity for efficient gene transfer to plant cells. The complex media often used for the cultivation of this species typically include animal-derived ingredients that can contain human pathogens, thus conflicting with the requirements of good manufacturing practice (GMP). We replaced all the animal-derived components in yeast extract broth (YEB) cultivation medium with soybean peptone, and then used a design-of-experiments approach to optimize the medium composition, increasing the biomass yield while maintaining high levels of transient expression in subsequent infiltration experiments. The resulting plant peptone Agrobacterium medium (PAM) achieved a two-fold increase in OD 600 compared to YEB medium during a 4-L batch fermentation lasting 18 h. Furthermore, the yields of the monoclonal antibody 2G12 and the fluorescent protein DsRed were maintained when the cells were cultivated in PAM rather than YEB. We have thus demonstrated a simple, efficient and scalable method for medium optimization that reduces process time and costs. The final optimized medium for the cultivation of A. tumefaciens completely lacks animal-derived components, thus facilitating the GMP-compliant large-scale transient expression of recombinant proteins in plants. © 2017 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Swift-BAT Hard X-ray Transient Monitor

NASA Technical Reports Server (NTRS)

Krimm, Hans; Markwardt, C. B.; Sanwal, D.; Tueller, J.

2006-01-01

The Burst Alert Telescope (BAT) on the Swift satellite is a large field of view instrument that continually monitors the sky to provide the gamma-ray burst trigger for Swift. An average of more than 70% of the sky is observed on a daily basis. The survey mode data is processed on two sets on time scales: from one minute to one day as part of the transient monitor program, and from one spacecraft pointing (approx.20 minutes) to the full mission duration for the hard X-ray survey program. The transient monitor has recently become public through the web site http:// swift.gsfc.nasa.gov/docs/swift/results/transients/. Sky images are processed to detect astrophysical sources in the 15-50 keV energy band and the detected flux or upper limit is calculated for >100 sources on time scales up to one day. Light curves are updated each time that new BAT data becomes available (approx.10 times daily). In addition, the monitor is sensitive to an outburst from a new or unknown source. Sensitivity as a function of time scale for catalog and unknown sources will be presented. The daily exposure for a typical source is approx.1500-3000 seconds, with a 1-sigma sensitivity of approx.4 mCrab. 90% of the sources are sampled at least every 16 days, but many sources are sampled daily. It is expected that the Swift-BAT transient monitor will become an important resource for the high energy astrophysics community.

Swift-BAT: Transient Source Monitoring

NASA Astrophysics Data System (ADS)

Barbier, L. M.; Barthelmy, S.; Cummings, J.; Gehrels, N.; Krimm, H.; Markwardt, C.; Mushotzky, R.; Parsons, A.; Sakamoto, T.; Tueller, J.; Fenimore, E.; Palmer, D.; Skinner, G.; Swift-BAT Team

2005-12-01

The Burst Alert Telescope (BAT) on the Swift satellite is a large field of view instrument that continually monitors the sky to provide the gamma-ray burst trigger for Swift. An average of more than 70% of the sky is observed on a daily basis. The survey mode data is processed on two sets of time scales: from one minute to one day as part of the transient monitor program, and from one spacecraft pointing ( ˜20 minutes) to the full mission duration for the hard X-ray survey program. In the transient monitor program, sky images are processed to detect astrophysical sources in six energy bands covering 15-350 keV. The detected flux or upper limit in each energy band is calculated for >300 objects on time scales up to one day. In addition, the monitor is sensitive to an outburst from a new or unknown source. Sensitivity as a function of time scale for catalog and unknown sources will be presented. The daily exposure for a typical source is ˜1500 - 3000 seconds, with a 1-sigma sensitivity of ˜4mCrab. 90% of the sources are sampled at least every 16 days, but many sources are sampled daily. The BAT team will soon make the results of the transient monitor public to the astrophysical community through the Swift mission web page. It is expected that the Swift-BAT transient monitor will become an important resource for the high energy astrophysics community.

Simulating spontaneous aseismic and seismic slip events on evolving faults

NASA Astrophysics Data System (ADS)

Herrendörfer, Robert; van Dinther, Ylona; Pranger, Casper; Gerya, Taras

2017-04-01

Plate motion along tectonic boundaries is accommodated by different slip modes: steady creep, seismic slip and slow slip transients. Due to mainly indirect observations and difficulties to scale results from laboratory experiments to nature, it remains enigmatic which fault conditions favour certain slip modes. Therefore, we are developing a numerical modelling approach that is capable of simulating different slip modes together with the long-term fault evolution in a large-scale tectonic setting. We extend the 2D, continuum mechanics-based, visco-elasto-plastic thermo-mechanical model that was designed to simulate slip transients in large-scale geodynamic simulations (van Dinther et al., JGR, 2013). We improve the numerical approach to accurately treat the non-linear problem of plasticity (see also EGU 2017 abstract by Pranger et al.). To resolve a wide slip rate spectrum on evolving faults, we develop an invariant reformulation of the conventional rate-and-state dependent friction (RSF) and adapt the time step (Lapusta et al., JGR, 2000). A crucial part of this development is a conceptual ductile fault zone model that relates slip rates along discrete planes to the effective macroscopic plastic strain rates in the continuum. We test our implementation first in a simple 2D setup with a single fault zone that has a predefined initial thickness. Results show that deformation localizes in case of steady creep and for very slow slip transients to a bell-shaped strain rate profile across the fault zone, which suggests that a length scale across the fault zone may exist. This continuum length scale would overcome the common mesh-dependency in plasticity simulations and question the conventional treatment of aseismic slip on infinitely thin fault zones. We test the introduction of a diffusion term (similar to the damage description in Lyakhovsky et al., JMPS, 2011) into the state evolution equation and its effect on (de-)localization during faster slip events. We compare the slip spectrum in our simulations to conventional RSF simulations (Liu and Rice, JGR, 2007). We further demonstrate the capability of simulating the evolution of a fault zone and simultaneous occurrence of slip transients. From small random initial distributions of the state variable in an otherwise homogeneous medium, deformation localizes and forms curved zones of reduced states. These spontaneously formed fault zones host slip transients, which in turn contribute to the growth of the fault zone.

Plate motions and deformations from geologic and geodetic data

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.

1990-01-01

An analysis of geodetic data in the vicinity of the Crustal Dynamics Program (CDP) site at Vandenberg Air Force Base (VNDN) is presented. The utility of space-geodetic data in the monitoring of transient strains associated with earthquakes in tectonically active areas like California is investigated. Particular interest is in the possibility that space-geodetic methods may be able to provide critical new data on deformations precursory to large seismic events. Although earthquake precursory phenomena are not well understood, the monitoring of small strains in the vicinity of active faults is a promising technique for studying the mechanisms that nucleate large earthquakes and, ultimately, for earthquake prediction. Space-geodetic techniques are now capable of measuring baselines of tens to hundreds of kilometers with a precision of a few parts in 108. Within the next few years, it will be possible to record and analyze large-scale strain variations with this precision continuously in real time. Thus, space-geodetic techniques may become tools for earthquake prediction. In anticipation of this capability, several questions related to the temporal and spatial scales associated with subseismic deformation transients are examined.

Large-scale thermal events in the solar nebula: evidence from Fe,Ni metal grains in primitive meteorites

PubMed

Meibom; Desch; Krot; Cuzzi; Petaev; Wilson; Keil

2000-05-05

Chemical zoning patterns in some iron, nickel metal grains from CH carbonaceous chondrites imply formation at temperatures from 1370 to 1270 kelvin by condensation from a solar nebular gas cooling at a rate of approximately 0.2 kelvin per hour. This cooling rate requires a large-scale thermal event in the nebula, in contrast to the localized, transient heating events inferred for chondrule formation. In our model, mass accretion through the protoplanetary disk caused large-scale evaporation of precursor dust near its midplane inside of a few astronomical units. Gas convectively moved from the midplane to cooler regions above it, and the metal grains condensed in these parcels of rising gas.

Large-Scale Traveling Weather Systems in Mars’ Southern Extratropics

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2017-10-01

Between late fall and early spring, Mars’ middle- and high-latitude atmosphere supports strong mean equator-to-pole temperature contrasts and an accompanying mean westerly polar vortex. Observations from both the MGS Thermal Emission Spectrometer (TES) and the MRO Mars Climate Sounder (MCS) indicate that a mean baroclinicity-barotropicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Such extratropical weather disturbances are critical components of the global circulation as they serve as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of such traveling extratropical synoptic disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively-lifted and radiatively-active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Large-Scale Traveling Weather Systems in Mars Southern Extratropics

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.

2017-01-01

Between late fall and early spring, Mars' middle- and high-latitude atmosphere supports strong mean equator-to-pole temperature contrasts and an accompanying mean westerly polar vortex. Observations from both the MGS Thermal Emission Spectrometer (TES) and the MRO Mars Climate Sounder (MCS) indicate that a mean baroclinicity-barotropicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Such extratropical weather disturbances are critical components of the global circulation as they serve as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of such traveling extratropical synoptic disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively-lifted and radiatively-active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Large-Scale Transient Transfection of Suspension Mammalian Cells for VLP Production.

PubMed

Cervera, Laura; Kamen, Amine A

2018-01-01

Large-scale transient transfection of mammalian cell suspension cultures enables the production of biological products in sufficient quantity and under stringent quality attributes to perform accelerated in vitro evaluations and has the potential to support preclinical or even clinical studies. Here we describe the methodology to produce VLPs in a 3L bioreactor, using suspension HEK 293 cells and PEIPro as a transfection reagent. Cells are grown in the bioreactor to 1 × 10 6 cells/mL and transfected with a plasmid DNA-PEI complex at a ratio of 1:2. Dissolved oxygen and pH are controlled and are online monitored during the production phase and cell growth and viability can be measured off line taking samples from the bioreactor. If the product is labeled with a fluorescent marker, transfection efficiency can be also assessed using flow cytometry analysis. Typically, the production phase lasts between 48 and 96 h until the product is harvested.

Techno-economic analysis of horseradish peroxidase production using a transient expression system in Nicotiana benthamiana.

PubMed

Walwyn, David Richard; Huddy, Suzanne M; Rybicki, Edward P

2015-01-01

Despite the advantages of plant-based transient expression systems relative to microbial or mammalian cell systems, the commercial production of recombinant proteins using plants has not yet been achieved to any significant extent. One of the challenges has been the lack of published data on the costs of manufacture for products other than biopharmaceuticals. In this study, we report on the techno-economic analysis of the production of a standard commercial enzyme, namely, horseradish peroxidase (HRP), using a transient expression system in Nicotiana benthamiana. Based on the proven plant yield of 240 mg HRP/kg biomass, a biomass productivity of 15-kg biomass/m(2)/year and a process yield of 54 % (mg HRP product/mg HRP in biomass), it is apparent that HRP can be manufactured economically via transient expression in plants in a large-scale facility (>5 kg HRP/year). At this level, the process is competitive versus the existing technology (extraction of the enzyme from horseradish), and the product is of comparable or improved activity, containing only the preferred isoenzyme C. Production scale, protein yield and biomass productivity are found to be the most important determinants of overall viability.

Transient jet formation and state transitions from large-scale magnetic reconnection in black hole accretion discs

NASA Astrophysics Data System (ADS)

Dexter, Jason; McKinney, Jonathan C.; Markoff, Sera; Tchekhovskoy, Alexander

2014-05-01

Magnetically arrested accretion discs (MADs), where the magnetic pressure in the inner disc is dynamically important, provide an alternative mechanism for regulating accretion to what is commonly assumed in black hole systems. We show that a global magnetic field inversion in the MAD state can destroy the jet, significantly increase the accretion rate, and move the effective inner disc edge in to the marginally stable orbit. Reconnection of the MAD field in the inner radii launches a new type of transient outflow containing hot plasma generated by magnetic dissipation. This transient outflow can be as powerful as the steady magnetically dominated Blandford-Znajek jet in the MAD state. The field inversion qualitatively describes many of the observational features associated with the high-luminosity hard-to-soft state transition in black hole X-ray binaries: the jet line, the transient ballistic jet, and the drop in rms variability. These results demonstrate that the magnetic field configuration can influence the accretion state directly, and hence the magnetic field structure is an important second parameter in explaining observations of accreting black holes across the mass and luminosity scales.

Millimeter transient point sources in the SPTpol 100 square degree survey

DOE PAGES

Whitehorn, N.; Natoli, T.; Ade, P. A. R.; ...

2016-10-18

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band—particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012–2013 season, the telescope was used to continuously observe a 100 deg 2 patch of sky centered atmore » R.A. 23 h30 m and decl. –55° using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. As a result, one candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low (p = 0.01) to confirm detection.« less

MILLIMETER TRANSIENT POINT SOURCES IN THE SPTpol 100 SQUARE DEGREE SURVEY

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

Whitehorn, N.; Haan, T. de; George, E. M.

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band—particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012–2013 season, the telescope was used to continuously observe a 100 deg{sup 2} patch of sky centered atmore » R.A. 23{sup h}30{sup m} and decl. −55° using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. One candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low ( p = 0.01) to confirm detection.« less

Millimeter transient point sources in the SPTpol 100 square degree survey

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

Whitehorn, N.; Natoli, T.; Ade, P. A. R.

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes, designed for measurement of the cosmic microwave background (CMB), offer the possibility to discover new, unknown transient sources in this band—particularly the afterglows of unobserved gamma-ray bursts (GRBs). Here, we use the 10 m millimeter-wave South Pole Telescope, designed for the primary purpose of observing the CMB at arcminute and larger angular scales, to conduct a search for such objects. During the 2012–2013 season, the telescope was used to continuously observe a 100 deg 2 patch of sky centered atmore » R.A. 23 h30 m and decl. –55° using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hr of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. As a result, one candidate object was observed with properties broadly consistent with a GRB afterglow, but at a statistical significance too low (p = 0.01) to confirm detection.« less

Significance of large vessel intracranial occlusion causing acute ischemic stroke and TIA.

PubMed

Smith, Wade S; Lev, Michael H; English, Joey D; Camargo, Erica C; Chou, Maggie; Johnston, S Claiborne; Gonzalez, Gilberto; Schaefer, Pamela W; Dillon, William P; Koroshetz, Walter J; Furie, Karen L

2009-12-01

Acute ischemic stroke due to large vessel occlusion (LVO)-vertebral, basilar, carotid terminus, middle and anterior cerebral arteries-likely portends a worse prognosis than stroke unassociated with LVO. Because little prospective angiographic data have been reported on a cohort of unselected patients with stroke and with transient ischemic attack, the clinical impact of LVO has been difficult to quantify. The Screening Technology and Outcome Project in Stroke Study is a prospective imaging-based study of stroke outcomes performed at 2 academic medical centers. Patients with suspected acute stroke who presented within 24 hours of symptom onset and who underwent multimodality CT/CT angiography were approached for consent for collection of clinical data and 6-month assessment of outcome. Demographic and clinical variables and 6-month modified Rankin Scale scores were collected and combined with blinded interpretation of the CT angiography data. The OR of each variable, including occlusion of intracranial vascular segment in predicting good outcome and 6-month mortality, was calculated using univariate and multivariate logistic regression. Over a 33-month period, 735 patients with suspected stroke were enrolled. Of these, 578 were adjudicated as stroke and 97 as transient ischemic attack. Among patients with stroke, 267 (46%) had LVO accounting for the stroke and 13 (13%) of patients with transient ischemic attack had LVO accounting for transient ischemic attack symptoms. LVO predicted 6-month mortality (OR, 4.5; 95% CI, 2.7 to 7.3; P<0.001). Six-month good outcome (modified Rankin Scale score

In situ visualization for large-scale combustion simulations.

PubMed

Yu, Hongfeng; Wang, Chaoli; Grout, Ray W; Chen, Jacqueline H; Ma, Kwan-Liu

2010-01-01

As scientific supercomputing moves toward petascale and exascale levels, in situ visualization stands out as a scalable way for scientists to view the data their simulations generate. This full picture is crucial particularly for capturing and understanding highly intermittent transient phenomena, such as ignition and extinction events in turbulent combustion.

Apparent dispersion in transient groundwater flow

USGS Publications Warehouse

Goode, Daniel J.; Konikow, Leonard F.

1990-01-01

This paper investigates the effects of large-scale temporal velocity fluctuations, particularly changes in the direction of flow, on solute spreading in a two-dimensional aquifer. Relations for apparent longitudinal and transverse dispersivity are developed through an analytical solution for dispersion in a fluctuating, quasi-steady uniform flow field, in which storativity is zero. For transient flow, spatial moments are evaluated from numerical solutions. Ignored or unknown transients in the direction of flow primarily act to increase the apparent transverse dispersivity because the longitudinal dispersivity is acting in a direction that is not the assumed flow direction. This increase is a function of the angle between the transient flow vector and the assumed steady state flow direction and the ratio of transverse to longitudinal dispersivity. The maximum effect on transverse dispersivity occurs if storativity is assumed to be zero, such that the flow field responds instantly to boundary condition changes.

Engineering science and mechanics; Proceedings of the International Symposium, Tainan, Republic of China, December 29-31, 1981. Parts 1 & 2

NASA Astrophysics Data System (ADS)

Hsia, H.-M.; Chou, Y.-L.; Longman, R. W.

1983-07-01

The topics considered are related to measurements and controls in physical systems, the control of large scale and distributed parameter systems, chemical engineering systems, aerospace science and technology, thermodynamics and fluid mechanics, and computer applications. Subjects in structural dynamics are discussed, taking into account finite element approximations in transient analysis, buckling finite element analysis of flat plates, dynamic analysis of viscoelastic structures, the transient analysis of large frame structures by simple models, large amplitude vibration of an initially stressed thick plate, nonlinear aeroelasticity, a sensitivity analysis of a combined beam-spring-mass structure, and the optimal design and aeroelastic investigation of segmented windmill rotor blades. Attention is also given to dynamics and control of mechanical and civil engineering systems, composites, and topics in materials. For individual items see A83-44002 to A83-44061

Postseismic deformation following the June 2000 earthquake sequence in the south Iceland seismic zone

USGS Publications Warehouse

Arnadottir, T.; Jonsson, Sigurjon; Pollitz, F.F.; Jiang, W.; Feigl, K.L.

2005-01-01

We observe postseismic deformation on two spatiotemporal scales following Mw = 6.5 earthquakes in the south Iceland seismic zone on 17 and 21 June 2000. We see a rapidly decaying deformation transient lasting no more than 2 months and extending about 5 km away from the two main shock ruptures. This local, month-scale transient is captured by several radar interferograms and is also observed at a few campaign GPS sites located near the faults. A slower transient with a characteristic timescale of about a year is detected only by GPS measurements. The month-scale deformation pattern has been explained by poroelastic rebound due to postearthquake pore pressure changes. In contrast, the year-scale deformation can be explained by either afterslip at 8-14 km depth or viscoelastic relaxation of the lower crust and upper mantle in response to the coseismic stress changes. The optimal viscoelastic models have lower crustal viscosities of 0.5-1 ?? 1019 Pa s and upper mantle viscosity of ???3 ?? 1018 Pa s. Because of the limitations of our GPS campaign data, we consider both afterslip and viscoelastic relaxation as plausible mechanisms explaining the deformation field. Both types of postseismic deformation models suggest that the areas of large coseismic stress increase east of the 17 June and west of the 21 June ruptures continue to be loaded by the postseismic deformation. Copyright 2005 by the American Geophysical Union.

Slow-Down in Diffusion in Crowded Protein Solutions Correlates with Transient Cluster Formation.

PubMed

Nawrocki, Grzegorz; Wang, Po-Hung; Yu, Isseki; Sugita, Yuji; Feig, Michael

2017-12-14

For a long time, the effect of a crowded cellular environment on protein dynamics has been largely ignored. Recent experiments indicate that proteins diffuse more slowly in a living cell than in a diluted solution, and further studies suggest that the diffusion depends on the local surroundings. Here, detailed insight into how diffusion depends on protein-protein contacts is presented based on extensive all-atom molecular dynamics simulations of concentrated villin headpiece solutions. After force field adjustments in the form of increased protein-water interactions to reproduce experimental data, translational and rotational diffusion was analyzed in detail. Although internal protein dynamics remained largely unaltered, rotational diffusion was found to slow down more significantly than translational diffusion as the protein concentration increased. The decrease in diffusion is interpreted in terms of a transient formation of protein clusters. These clusters persist on sub-microsecond time scales and follow distributions that increasingly shift toward larger cluster size with increasing protein concentrations. Weighting diffusion coefficients estimated for different clusters extracted from the simulations with the distribution of clusters largely reproduces the overall observed diffusion rates, suggesting that transient cluster formation is a primary cause for a slow-down in diffusion upon crowding with other proteins.

Transient Volcano Deformation Event Detection over Variable Spatial Scales in Alaska

NASA Astrophysics Data System (ADS)

Li, J. D.; Rude, C. M.; Gowanlock, M.; Herring, T.; Pankratius, V.

2016-12-01

Transient deformation events driven by volcanic activity can be monitored using increasingly dense networks of continuous Global Positioning System (GPS) ground stations. The wide spatial extent of GPS networks, the large number of GPS stations, and the spatially and temporally varying scale of deformation events result in the mixing of signals from multiple sources. Typical analysis then necessitates manual identification of times and regions of volcanic activity for further study and the careful tuning of algorithmic parameters to extract possible transient events. Here we present a computer-aided discovery system that facilitates the discovery of potential transient deformation events at volcanoes by providing a framework for selecting varying spatial regions of interest and for tuning the analysis parameters. This site specification step in the framework reduces the spatial mixing of signals from different volcanic sources before applying filters to remove interfering signals originating from other geophysical processes. We analyze GPS data recorded by the Plate Boundary Observatory network and volcanic activity logs from the Alaska Volcano Observatory to search for and characterize transient inflation events in Alaska. We find 3 transient inflation events between 2008 and 2015 at the Akutan, Westdahl, and Shishaldin volcanoes in the Aleutian Islands. The inflation event detected in the first half of 2008 at Akutan is validated other studies, while the inflation events observed in early 2011 at Westdahl and in early 2013 at Shishaldin are previously unreported. Our analysis framework also incorporates modelling of the transient inflation events and enables a comparison of different magma chamber inversion models. Here, we also estimate the magma sources that best describe the deformation observed by the GPS stations at Akutan, Westdahl, and Shishaldin. We acknowledge support from NASA AIST-NNX15AG84G (PI: V. Pankratius).

Large-scale dynamos in rapidly rotating plane layer convection

NASA Astrophysics Data System (ADS)

Bushby, P. J.; Käpylä, P. J.; Masada, Y.; Brandenburg, A.; Favier, B.; Guervilly, C.; Käpylä, M. J.

2018-05-01

Context. Convectively driven flows play a crucial role in the dynamo processes that are responsible for producing magnetic activity in stars and planets. It is still not fully understood why many astrophysical magnetic fields have a significant large-scale component. Aims: Our aim is to investigate the dynamo properties of compressible convection in a rapidly rotating Cartesian domain, focusing upon a parameter regime in which the underlying hydrodynamic flow is known to be unstable to a large-scale vortex instability. Methods: The governing equations of three-dimensional non-linear magnetohydrodynamics (MHD) are solved numerically. Different numerical schemes are compared and we propose a possible benchmark case for other similar codes. Results: In keeping with previous related studies, we find that convection in this parameter regime can drive a large-scale dynamo. The components of the mean horizontal magnetic field oscillate, leading to a continuous overall rotation of the mean field. Whilst the large-scale vortex instability dominates the early evolution of the system, the large-scale vortex is suppressed by the magnetic field and makes a negligible contribution to the mean electromotive force that is responsible for driving the large-scale dynamo. The cycle period of the dynamo is comparable to the ohmic decay time, with longer cycles for dynamos in convective systems that are closer to onset. In these particular simulations, large-scale dynamo action is found only when vertical magnetic field boundary conditions are adopted at the upper and lower boundaries. Strongly modulated large-scale dynamos are found at higher Rayleigh numbers, with periods of reduced activity (grand minima-like events) occurring during transient phases in which the large-scale vortex temporarily re-establishes itself, before being suppressed again by the magnetic field.

Subcontinental-scale crustal velocity changes along the Pacific-North America plate boundary.

PubMed

Davis, J L; Wernicke, B P; Bisnath, S; Niemi, N A; Elósegui, P

2006-06-29

Transient tectonic deformation has long been noted within approximately 100 km of plate boundary fault zones and within active volcanic regions, but it is unknown whether transient motions also occur at larger scales within plates. Relatively localized transients are known to occur as both seismic and episodic aseismic events, and are generally ascribed to motions of magma bodies, aseismic creep on faults, or elastic or viscoelastic effects associated with earthquakes. However, triggering phenomena and systematic patterns of seismic strain release at subcontinental (approximately 1,000 km) scale along diffuse plate boundaries have long suggested that energy transfer occurs at larger scale. Such transfer appears to occur by the interaction of stresses induced by surface wave propagation and magma or groundwater in the crust, or from large-scale stress diffusion within the oceanic mantle in the decades following clusters of great earthquakes. Here we report geodetic evidence for a coherent, subcontinental-scale change in tectonic velocity along a diffuse approximately 1,000-km-wide deformation zone. Our observations are derived from continuous GPS (Global Positioning System) data collected over the past decade across the Basin and Range province, which absorbs approximately 25 per cent of Pacific-North America relative plate motion. The observed changes in site velocity define a sharp boundary near the centre of the province oriented roughly parallel to the north-northwest relative plate motion vector. We show that sites to the west of this boundary slowed relative to sites east of it by approximately 1 mm yr(-1) starting in late 1999.

Fast transient X-rays and gamma ray bursts - Are they stellar flares?

NASA Astrophysics Data System (ADS)

Rao, A. R.; Vahia, M. N.

Short period transient X-ray emissions (FTX) have been observed from several sources in the sky and the largest single group of objects identified with such sources are active stars: flare stars, and RS CVn binaries. The study of the number, source and flux distribution of the fast transient X-ray sources shows that all the FTX emission can be treated as flares in the interbinary regions of active stars. It is suggested that the FTX emission is a common feature of the gamma ray bursts (GRBs). The evidence for the similarity between the hard X-ray flares and GRBs is discussed, and the possibility that the gamma ray bursts are the impulsive precursors of FTX originating from active stars with large scale magnetic activity is examined.

Pressure Probe Designs for Dynamic Pressure Measurements in a Supersonic Flow Field. [conducted in the Glenn Supersonic Wind Tunnel (SWT)

NASA Technical Reports Server (NTRS)

Porro, A. Robert

2001-01-01

A series of dynamic flow field pressure probes were developed for use in large-scale supersonic wind tunnels at NASA Glenn Research Center. These flow field probes include pitot, static, and five-hole conical pressure probes that are capable of capturing fast acting flow field pressure transients that occur on a millisecond time scale. The pitot and static probes can be used to determine local Mach number time histories during a transient event. The five-hole conical pressure probes are used primarily to determine local flow angularity, but can also determine local Mach number. These probes were designed, developed, and tested at the NASA Glenn Research Center. They were also used in a NASA Glenn 10- by 10-Foot Supersonic Wind Tunnel (SWT) test program where they successfully acquired flow field pressure data in the vicinity of a propulsion system during an engine compressor stall and inlet unstart transient event. Details of the design, development, and subsequent use of these probes are discussed in this report.

Optimal Transient Growth of Submesoscale Baroclinic Instabilities

NASA Astrophysics Data System (ADS)

White, Brian; Zemskova, Varvara; Passaggia, Pierre-Yves

2016-11-01

Submesoscale instabilities are analyzed using a transient growth approach to determine the optimal perturbation for a rotating Boussinesq fluid subject to baroclinic instabilities. We consider a base flow with uniform shear and stratification and consider the non-normal evolution over finite-time horizons of linear perturbations in an ageostrophic, non-hydrostatic regime. Stone (1966, 1971) showed that the stability of the base flow to normal modes depends on the Rossby and Richardson numbers, with instabilities ranging from geostrophic (Ro -> 0) and ageostrophic (finite Ro) baroclinic modes to symmetric (Ri < 1 , Ro > 1) and Kelvin-Helmholtz (Ri < 1 / 4) modes. Non-normal transient growth, initiated by localized optimal wave packets, represents a faster mechanism for the growth of perturbations and may provide an energetic link between large-scale flows in geostrophic balance and dissipation scales via submesoscale instabilities. Here we consider two- and three-dimensional optimal perturbations by means of direct-adjoint iterations of the linearized Boussinesq Navier-Stokes equations to determine the form of the optimal perturbation, the optimal energy gain, and the characteristics of the most unstable perturbation.

Kilauea volcano, hawaii: a search for the volcanomagnetic effect.

PubMed

Davis, P M; Jackson, D B; Field, J; Stacey, F D

1973-04-06

Brief excursions of magnetic field differences between a base station and two satellite station magnetometers show only slight correlation with ground tilt at Kilauea Volcano. This result suggests that only transient, localized stresses occur during prolonged periods of deformation and that the volcano can support no large-scale pattern of shear stresses.

The PANDA tests for SBWR certification

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

Varadi, G.; Dreier, J.; Bandurski, Th.

1996-03-01

The ALPHA project is centered around the experimental and analytical investigation of the long-term decay heat removal from the containments of the next generation of {open_quotes}passive{close_quotes} ALWRs. The project includes integral system tests in the large-scale (1:25 in volume) PANDA facility as well as several other series of tests and supporting analytical work. The first series of experiments to be conducted in PANDA have become a required experimental element in the certification process for the General Electric Simplified Boiling Water Reactor (SBWR). The PANDA general experimental philosophy, facility design, scaling, and instrumentation are described. Steady-state PCCS condenser performance tests andmore » extensive facility characterization tests were already conducted. The transient system behavior tests are underway; preliminary results from the first transient test M3 are reviewed.« less

Observations and Modeling of the Transient General Circulation of the North Pacific Basin

NASA Technical Reports Server (NTRS)

McWilliams, James C.

2000-01-01

Because of recent progress in satellite altimetry and numerical modeling and the accumulation and archiving of long records of hydrographic and meteorological variables, it is becoming feasible to describe and understand the transient general circulation of the ocean (i.e., variations with spatial scales larger than a few hundred kilometers and time scales of seasonal and longer-beyond the mesoscale). We have carried out various studies in investigation of the transient general circulation of the Pacific Ocean from a coordinated analysis of satellite altimeter data, historical hydrographic gauge data, scatterometer wind observations, reanalyzed operational wind fields, and a variety of ocean circulation models. Broadly stated, our goal was to achieve a phenomenological catalogue of different possible types of large-scale, low-frequency variability, as a context for understanding the observational record. The approach is to identify the simplest possible model from which particular observed phenomena can be isolated and understood dynamically and then to determine how well these dynamical processes are represented in more complex Oceanic General Circulation Models (OGCMs). Research results have been obtained on Rossby wave propagation and transformation, oceanic intrinsic low-frequency variability, effects of surface gravity waves, pacific data analyses, OGCM formulation and developments, and OGCM simulations of forced variability.

High cell density media for Escherichia coli are generally designed for aerobic cultivations – consequences for large-scale bioprocesses and shake flask cultures

PubMed Central

Soini, Jaakko; Ukkonen, Kaisa; Neubauer, Peter

2008-01-01

Background For the cultivation of Escherichia coli in bioreactors trace element solutions are generally designed for optimal growth under aerobic conditions. They do normally not contain selenium and nickel. Molybdenum is only contained in few of them. These elements are part of the formate hydrogen lyase (FHL) complex which is induced under anaerobic conditions. As it is generally known that oxygen limitation appears in shake flask cultures and locally in large-scale bioreactors, function of the FHL complex may influence the process behaviour. Formate has been described to accumulate in large-scale cultures and may have toxic effects on E. coli. Although the anaerobic metabolism of E. coli is well studied, reference data which estimate the impact of the FHL complex on bioprocesses of E. coli with oxygen limitation have so far not been published, but are important for a better process understanding. Results Two sets of fed-batch cultures with conditions triggering oxygen limitation and formate accumulation were performed. Permanent oxygen limitation which is typical for shake flask cultures was caused in a bioreactor by reduction of the agitation rate. Transient oxygen limitation, which has been described to eventually occur in the feed-zone of large-scale bioreactors, was mimicked in a two-compartment scale-down bioreactor consisting of a stirred tank reactor and a plug flow reactor (PFR) with continuous glucose feeding into the PFR. In both models formate accumulated up to about 20 mM in the culture medium without addition of selenium, molybdenum and nickel. By addition of these trace elements the formate accumulation decreased below the level observed in well-mixed laboratory-scale cultures. Interestingly, addition of the extra trace elements caused accumulation of large amounts of lactate and reduced biomass yield in the simulator with permanent oxygen limitation, but not in the scale-down two-compartment bioreactor. Conclusion The accumulation of formate in oxygen limited cultivations of E. coli can be fully prevented by addition of the trace elements selenium, nickel and molybdenum, necessary for the function of FHL complex. For large-scale cultivations, if glucose gradients are likely, the results from the two-compartment scale-down bioreactor indicate that the addition of the extra trace elements is beneficial. No negative effects on the biomass yield or on any other bioprocess parameters could be observed in cultures with the extra trace elements if the cells were repeatedly exposed to transient oxygen limitation. PMID:18687130

Dynamically consistent parameterization of mesoscale eddies. Part III: Deterministic approach

NASA Astrophysics Data System (ADS)

Berloff, Pavel

2018-07-01

This work continues development of dynamically consistent parameterizations for representing mesoscale eddy effects in non-eddy-resolving and eddy-permitting ocean circulation models and focuses on the classical double-gyre problem, in which the main dynamic eddy effects maintain eastward jet extension of the western boundary currents and its adjacent recirculation zones via eddy backscatter mechanism. Despite its fundamental importance, this mechanism remains poorly understood, and in this paper we, first, study it and, then, propose and test its novel parameterization. We start by decomposing the reference eddy-resolving flow solution into the large-scale and eddy components defined by spatial filtering, rather than by the Reynolds decomposition. Next, we find that the eastward jet and its recirculations are robustly present not only in the large-scale flow itself, but also in the rectified time-mean eddies, and in the transient rectified eddy component, which consists of highly anisotropic ribbons of the opposite-sign potential vorticity anomalies straddling the instantaneous eastward jet core and being responsible for its continuous amplification. The transient rectified component is separated from the flow by a novel remapping method. We hypothesize that the above three components of the eastward jet are ultimately driven by the small-scale transient eddy forcing via the eddy backscatter mechanism, rather than by the mean eddy forcing and large-scale nonlinearities. We verify this hypothesis by progressively turning down the backscatter and observing the induced flow anomalies. The backscatter analysis leads us to formulating the key eddy parameterization hypothesis: in an eddy-permitting model at least partially resolved eddy backscatter can be significantly amplified to improve the flow solution. Such amplification is a simple and novel eddy parameterization framework implemented here in terms of local, deterministic flow roughening controlled by single parameter. We test the parameterization skills in an hierarchy of non-eddy-resolving and eddy-permitting modifications of the original model and demonstrate, that indeed it can be highly efficient for restoring the eastward jet extension and its adjacent recirculation zones. The new deterministic parameterization framework not only combines remarkable simplicity with good performance but also is dynamically transparent, therefore, it provides a powerful alternative to the common eddy diffusion and emerging stochastic parameterizations.

Transient behavior of redox flow battery connected to circuit based on global phase structure

NASA Astrophysics Data System (ADS)

Mannari, Toko; Hikihara, Takashi

A Redox Flow Battery (RFB) is one of the promising energy storage systems in power grid. An RFB has many advantages such as a quick response, a large capacity, and a scalability. Due to these advantages, an RFB can operate in mixed time scale. Actually, it has been demonstrated that an RFB can be used for load leveling, compensating sag, and smoothing the output of the renewable sources. An analysis on transient behaviors of an RFB is a key issue for these applications. An RFB is governed by electrical, chemical, and fluid dynamics. The hybrid structure makes the analysis difficult. To analyze transient behaviors of an RFB, the exact model is necessary. In this paper, we focus on a change in a concentration of ions in the electrolyte, and simulate the change with a model which is mainly based on chemical kinetics. The simulation results introduces transient behaviors of an RFB in a response to a load variation. There are found three kinds of typical transient behaviors including oscillations. As results, it is clarified that the complex transient behaviors, due to slow and fast dynamics in the system, arise by the quick response to load.

Killer whale call frequency is similar across the oceans, but varies across sympatric ecotypes.

PubMed

Filatova, Olga A; Miller, Patrick J O; Yurk, Harald; Samarra, Filipa I P; Hoyt, Erich; Ford, John K B; Matkin, Craig O; Barrett-Lennard, Lance G

2015-07-01

Killer whale populations may differ in genetics, morphology, ecology, and behavior. In the North Pacific, two sympatric populations ("resident" and "transient") specialize on different prey (fish and marine mammals) and retain reproductive isolation. In the eastern North Atlantic, whales from the same populations have been observed feeding on both fish and marine mammals. Fish-eating North Pacific "residents" are more genetically related to eastern North Atlantic killer whales than to sympatric mammal-eating "transients." In this paper, a comparison of frequency variables in killer whale calls recorded from four North Pacific resident, two North Pacific transient, and two eastern North Atlantic populations is reported to assess which factors drive the large-scale changes in call structure. Both low-frequency and high-frequency components of North Pacific transient killer whale calls have significantly lower frequencies than those of the North Pacific resident and North Atlantic populations. The difference in frequencies could be related to ecological specialization or to the phylogenetic history of these populations. North Pacific transient killer whales may have genetically inherited predisposition toward lower frequencies that may shape their learned repertoires.

MOSFiT: Modular Open Source Fitter for Transients

NASA Astrophysics Data System (ADS)

Guillochon, James; Nicholl, Matt; Villar, V. Ashley; Mockler, Brenna; Narayan, Gautham; Mandel, Kaisey S.; Berger, Edo; Williams, Peter K. G.

2018-05-01

Much of the progress made in time-domain astronomy is accomplished by relating observational multiwavelength time-series data to models derived from our understanding of physical laws. This goal is typically accomplished by dividing the task in two: collecting data (observing), and constructing models to represent that data (theorizing). Owing to the natural tendency for specialization, a disconnect can develop between the best available theories and the best available data, potentially delaying advances in our understanding new classes of transients. We introduce MOSFiT: the Modular Open Source Fitter for Transients, a Python-based package that downloads transient data sets from open online catalogs (e.g., the Open Supernova Catalog), generates Monte Carlo ensembles of semi-analytical light-curve fits to those data sets and their associated Bayesian parameter posteriors, and optionally delivers the fitting results back to those same catalogs to make them available to the rest of the community. MOSFiT is designed to help bridge the gap between observations and theory in time-domain astronomy; in addition to making the application of existing models and creation of new models as simple as possible, MOSFiT yields statistically robust predictions for transient characteristics, with a standard output format that includes all the setup information necessary to reproduce a given result. As large-scale surveys such as that conducted with the Large Synoptic Survey Telescope (LSST), discover entirely new classes of transients, tools such as MOSFiT will be critical for enabling rapid comparison of models against data in statistically consistent, reproducible, and scientifically beneficial ways.

Transient analysis of 1D inhomogeneous media by dynamic inhomogeneous finite element method

NASA Astrophysics Data System (ADS)

Yang, Zailin; Wang, Yao; Hei, Baoping

2013-12-01

The dynamic inhomogeneous finite element method is studied for use in the transient analysis of onedimensional inhomogeneous media. The general formula of the inhomogeneous consistent mass matrix is established based on the shape function. In order to research the advantages of this method, it is compared with the general finite element method. A linear bar element is chosen for the discretization tests of material parameters with two fictitious distributions. And, a numerical example is solved to observe the differences in the results between these two methods. Some characteristics of the dynamic inhomogeneous finite element method that demonstrate its advantages are obtained through comparison with the general finite element method. It is found that the method can be used to solve elastic wave motion problems with a large element scale and a large number of iteration steps.

Performance of fully-coupled algebraic multigrid preconditioners for large-scale VMS resistive MHD

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

Lin, P. T.; Shadid, J. N.; Hu, J. J.

Here, we explore the current performance and scaling of a fully-implicit stabilized unstructured finite element (FE) variational multiscale (VMS) capability for large-scale simulations of 3D incompressible resistive magnetohydrodynamics (MHD). The large-scale linear systems that are generated by a Newton nonlinear solver approach are iteratively solved by preconditioned Krylov subspace methods. The efficiency of this approach is critically dependent on the scalability and performance of the algebraic multigrid preconditioner. Our study considers the performance of the numerical methods as recently implemented in the second-generation Trilinos implementation that is 64-bit compliant and is not limited by the 32-bit global identifiers of themore » original Epetra-based Trilinos. The study presents representative results for a Poisson problem on 1.6 million cores of an IBM Blue Gene/Q platform to demonstrate very large-scale parallel execution. Additionally, results for a more challenging steady-state MHD generator and a transient solution of a benchmark MHD turbulence calculation for the full resistive MHD system are also presented. These results are obtained on up to 131,000 cores of a Cray XC40 and one million cores of a BG/Q system.« less

Performance of fully-coupled algebraic multigrid preconditioners for large-scale VMS resistive MHD

DOE PAGES

Lin, P. T.; Shadid, J. N.; Hu, J. J.; ...

2017-11-06

Here, we explore the current performance and scaling of a fully-implicit stabilized unstructured finite element (FE) variational multiscale (VMS) capability for large-scale simulations of 3D incompressible resistive magnetohydrodynamics (MHD). The large-scale linear systems that are generated by a Newton nonlinear solver approach are iteratively solved by preconditioned Krylov subspace methods. The efficiency of this approach is critically dependent on the scalability and performance of the algebraic multigrid preconditioner. Our study considers the performance of the numerical methods as recently implemented in the second-generation Trilinos implementation that is 64-bit compliant and is not limited by the 32-bit global identifiers of themore » original Epetra-based Trilinos. The study presents representative results for a Poisson problem on 1.6 million cores of an IBM Blue Gene/Q platform to demonstrate very large-scale parallel execution. Additionally, results for a more challenging steady-state MHD generator and a transient solution of a benchmark MHD turbulence calculation for the full resistive MHD system are also presented. These results are obtained on up to 131,000 cores of a Cray XC40 and one million cores of a BG/Q system.« less

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity

NASA Technical Reports Server (NTRS)

Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

Detonation failure characterization of non-ideal explosives

NASA Astrophysics Data System (ADS)

Janesheski, Robert S.; Groven, Lori J.; Son, Steven

2012-03-01

Non-ideal explosives are currently poorly characterized, hence limiting the modeling of them. Current characterization requires large-scale testing to obtain steady detonation wave characterization for analysis due to the relatively thick reaction zones. Use of a microwave interferometer applied to small-scale confined transient experiments is being implemented to allow for time resolved characterization of a failing detonation. The microwave interferometer measures the position of a failing detonation wave in a tube that is initiated with a booster charge. Experiments have been performed with ammonium nitrate and various fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics are influenced by factors such as chemical composition and confiner thickness. Future work is planned to calibrate models to these small-scale experiments and eventually validate the models with available large scale experiments. This experiment is shown to be repeatable, shows dependence on reactive properties, and can be performed with little required material.

Large Eddy Simulation of Flame-Turbulence Interactions in a LOX-CH4 Shear Coaxial Injector

DTIC Science & Technology

2012-01-01

heat transfer from dense to light fluids.A previous study on LOX/H2 flames39,40 have pointed the limitations of central scheme to predict such large...pp. 151–169. 39Masquelet, M., Simulations of a Sub-scale Liquid Rocket Engine: Transient Heat Transfer in a Real Gas Environment , Master’s thesis...Eddy Simulation of a cryogenic flame issued from a LOX-CH4 shear coaxial injector. The operating pressure is above the critical pressure for both

The Impact of Potassium Iodide on Thyroidectomy for Graves’ disease: Implications for Safety and Operative Difficulty

PubMed Central

Randle, Reese W; Bates, Maria F; Long, Kristin L; Pitt, Susan C; Schneider, David F; Sippel, Rebecca S

2017-01-01

Background Potassium iodide (KI) is often prescribed prior to thyroidectomy for Graves’ disease, but the effect of KI on the ease and safety of thyroidectomy for Graves’ is largely unknown. Methods We conducted a prospective cohort study of patients with Graves’ disease undergoing thyroidectomy. For the first 8-months no patients received KI; for the next 8-months, KI was added to the pre-operative protocol for all patients. Outcomes included operative difficulty (based on the Thyroidectomy Difficulty Scale) and complications. Results A total of 31 patients in the no-KI group and 28 in the KI group were included. According to the Thyroidectomy Difficulty Scale, gland vascularity decreased in the KI group (mean score 2.6 vs. 3.3, p=0.04), but there were no significant differences in thyroid friability, fibrosis, size, or overall difficulty (p=NS for all). Despite similar operative difficulty, patients prescribed KI were less likely to experience transient hypoparathyroidism (7.1% vs. 25.9%, p=0.018) and transient hoarseness (0% vs. 16.1%, p=0.009) compared with the no-KI group. Conclusion KI administration decreases gland vascularity but does not change the overall difficulty of thyroidectomy. However, KI was associated with less transient hypoparathyroidism and transient hoarseness, suggesting that KI improves the safety of thyroidectomy for Graves’ disease. PMID:29108701

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

Orange, N. Brice; Chesny, David L.; Oluseyi, Hakeem M.

Increasing evidence for coronal heating contributions from cooler solar atmospheric layers, notably quiet Sun (QS) conditions, challenges standard solar atmospheric descriptions of bright transition region (TR) emission. As such, questions about the role of dynamic QS transients in contributing to the total coronal energy budget are raised. Using observations from the Atmospheric Imaging Assembly and Heliosemic Magnetic Imager on board the Solar Dynamics Observatory, and numerical model extrapolations of coronal magnetic fields, we investigate a dynamic QS transient that is energetically isolated to the TR and extrudes from a common footpoint shared with two heated loop arcades. A non-causal relationshipmore » is established between episodic heating of the QS transient and widespread magnetic field re-organization events, while evidence is found favoring a magnetic topology that is typical of eruptive processes. Quasi-steady interchange reconnection events are implicated as a source of the transient’s visibly bright radiative signature. We consider the QS transient’s temporally stable (≈35 minutes) radiative nature to occur as a result of the large-scale magnetic field geometries of the QS and/or relatively quiet nature of the magnetic photosphere, which possibly act to inhibit energetic build-up processes that are required to initiate a catastrophic eruption phase. This work provides insight into the QS’s thermodynamic and magnetic relation to eruptive processes that quasi-steadily heat a small-scale dynamic and TR transient. This work explores arguments of non-negligible coronal heating contributions from cool atmospheric layers in QS conditions and contributes evidence to the notion that  solar wind mass feeds off of dynamic transients therein.« less

Investigation of models for large-scale meteorological prediction experiments

NASA Technical Reports Server (NTRS)

Spar, J.

1973-01-01

Studies are reported of the long term responses of the model atmosphere to anomalies in snow cover and sea surface temperature. An abstract of a previously issued report on the computed response to surface anomalies in a global atmospheric model is presented, and the experiments on the effects of transient sea surface temperature on the Mintz-Arakawa atmospheric model are reported.

On the nonlinear forced response of the North Atlantic atmosphere to meridional shifts of the Gulf Stream path

NASA Astrophysics Data System (ADS)

Seo, H.; Kwon, Y. O.; Joyce, T. M.; Ummenhofer, C.

2016-12-01

This study examines the North Atlantic atmospheric circulation response to the meridional shift of Gulf Stream path using a large-ensemble, high-resolution, and hemispheric-scale WRF simulations. The model is forced with wintertime SST anomalies derived from a wide range of Gulf Stream shift scenarios. The key result of the model experiments, supported in part by an independent analysis of a reanalysis data set, is that the large-scale, quasi-steady North Atlantic circulation response is unambiguously nonlinear about the sign and amplitude of chosen SST anomalies. This nonlinear response prevails over the weak linear response and resembles the negative North Atlantic Oscillation, the leading intrinsic mode of variability in the model and the observations. Further analysis of the associated dynamics reveals that the nonlinear responses are accompanied by the anomalous southward shift of the North Atlantic eddy-driven jet stream, which is reinforced nearly equally by the high-frequency transient eddy feedback and the low-frequency high-latitude wave breaking events. The result highlights the importance of the intrinsically nonlinear transient eddy dynamics and eddy-mean flow interactions in generating the nonlinear forced response to the meridional shift in the Gulf Stream.

Global structure transitions in an experimental induction furnace

NASA Astrophysics Data System (ADS)

Tasaka, Yuji; Galindo, Vladimir; Vogt, Tobias; Eckert, Sven

2017-11-01

Flows induced by alternating magnetic field (AMF) in a cylindrical vessel filled with liquid metal, alloy of GaInSn, were examined experimentally using ultrasonic Doppler velocimetry (UDV). Measurement lines of UDV arranged vertically set at different radial and azimuthal positions extracted flow structures and their time variations as spatio-temporal velocity maps in the opaque liquid metal layer. At low frequency of AMF, corresponding to shielding parameter S =μm σωR2 = O(1) (μm and σ are magnetic permeability and electric conductivity of the test fluid, ω angular frequency of AMF, and R the radius of cylindrical vessel), two toroidal vortices exist in the fluid layer as the large scale flow structure and have interactions each other. With increasing of S the structure has transition from toroidal vortex pair to four large scale circulations (S >= 100) via transient state, where strong interactions of two vortices are observed (30 < S < 100). Faster vertical stream is observed near the cylinder wall because of ski effect caused by AMF, and the time-averaged velocity of the stream takes maximum around S = 20 , which is little smaller value of S for the onset of the transient state. JSPS KAKENHI No. 15KK0219.

Comparison of the Single Molecule Dynamics of Linear and Circular DNAs in Planar Extensional Flows

NASA Astrophysics Data System (ADS)

Li, Yanfei; Hsiao, Kai-Wen; Brockman, Christopher; Yates, Daniel; McKenna, Gregory; Schroeder, Charles; San Francisco, Michael; Kornfield, Julie; Anderson, Rae

2015-03-01

Chain topology has a profound impact on the flow behaviors of single macromolecules. The absence of free ends separates circular polymers from other chain architectures, i.e., linear, star, and branched. In the present work, we study the single chain dynamics of large circular and linear DNA molecules by comparing the relaxation dynamics, steady state coil-stretch transition, and transient molecular individualism behaviors for the two types of macromolecules. To this end, large circular DNA molecules were biologically synthesized and studied in a microfluidic device that has a cross-slot geometry to develop a stagnation point extensional flow. Although the relaxation time of rings scales in the same way as for the linear analog, the circular polymers show quantitatively different behaviors in the steady state extension and qualitatively different behaviors during a transient stretch. The existence of some commonality between these two topologies is proposed. Texas Tech University John R. Bradford Endowment.

Forum on unsteady flow - 1985; Proceedings of the Winter Annual Meeting, Miami Beach, FL, November 17-22, 1985

NASA Astrophysics Data System (ADS)

Rothe, P. H.

The conference includes such topics as the reduction of fluid transient pressures by minimax optimization, modeling blockage in unsteady slurry flow in conduits, roles of vacuum breaker and air release devices in reducing waterhammer forces, and an analysis of laminar fluid transients in conduits of unconventional shape. Papers are presented on modulation systems for high speed water jets, water hammer analysis needs in nuclear power plant design, tail profile effects on unsteady large scale flow structure in the wing and plate junction, and a numerical study of pressure transients in a borehole due to pipe movement. Consideration is also given to boundary layer growth near a stagnation point, calculation of unsteady mixing in two-dimensional flows, the trailing edge of a pitching airfoil at high reduced frequencies, and a numerical study of instability-wave control through periodic wall suction/blowing.

Impact of Penetration Wind Turbines on Transient Stability in Sulbagsel Electrical Interconnection System

NASA Astrophysics Data System (ADS)

Nurtrimarini Karim, Andi; Mawar Said, Sri; Chaerah Gunadin, Indar; Darusman B, Mustadir

2018-03-01

This paper presents a rotor angle analysis when transient disturbance occurs when wind turbines enter the southern Sulawesi electrical interconnection system (Sulbagsel) both without and with the addition of a Power Stabilizer (PSS) control device. Time domain simulation (TDS) method is used to analyze the rotor angle deviation (δ) and rotor angle velocity (ω). A total of 44 buses, 47 lines, 6 transformers, 15 generators and 34 loads were modeled for analysis after the inclusion of large-scale wind turbines in the Sidrap and Jeneponto areas. The simulation and computation results show the addition of PSS devices to the system when transient disturbance occurs when the winds turbine entering the Sulbagsel electrical system is able to dampen and improve the rotor angle deviation (δ) and the rotor angle velocity (ω) towards better thus helping the system to continue operation at a new equilibrium point.

Role of Transient Mobility on Submonolayer Island Growth: Extensions and Testing

NASA Astrophysics Data System (ADS)

Morales Cifuentes, Josue; Einstein, Theodore; Pimpinelli, Alberto

In studies of epitaxial growth a major goal is assessing the smallest stable cluster (i + 1 monomers, with i the critical nucleus size), by analyzing the capture zone distribution (CZD) or the scaling of incident flux F to the density of stable islands N (N ~Fα , with α the growth exponent). As noted in the previous talk, the GWD has well described the data in several experiments, including submonolayer para-hexaphenyl (6P) on amorphous mica (i ~ 3). Different scaling (Fα) for 6P at (small) large F is attributed to (DLA) ALA dynamics, i.e. i = (5) 7 +/- 2. Our recent theoretical work considered monomers propagating ballistically before thermalizing or attaching to islands, leading to scaling, non-monotonic crossover, and activation energies that account for the data and reconciling the values of i. We present applications to other experimental systems: 6P on SiO2 and pentacene (5A) on amorphous mica. We describe useful simplifying approximations, and preliminary kinetic Monte Carlo simulations including transient effects on growth. Work at UMD supported by NSF CHE 13-05892.

Transient Cognitive Dynamics, Metastability, and Decision Making

PubMed Central

Rabinovich, Mikhail I.; Huerta, Ramón; Varona, Pablo; Afraimovich, Valentin S.

2008-01-01

The idea that cognitive activity can be understood using nonlinear dynamics has been intensively discussed at length for the last 15 years. One of the popular points of view is that metastable states play a key role in the execution of cognitive functions. Experimental and modeling studies suggest that most of these functions are the result of transient activity of large-scale brain networks in the presence of noise. Such transients may consist of a sequential switching between different metastable cognitive states. The main problem faced when using dynamical theory to describe transient cognitive processes is the fundamental contradiction between reproducibility and flexibility of transient behavior. In this paper, we propose a theoretical description of transient cognitive dynamics based on the interaction of functionally dependent metastable cognitive states. The mathematical image of such transient activity is a stable heteroclinic channel, i.e., a set of trajectories in the vicinity of a heteroclinic skeleton that consists of saddles and unstable separatrices that connect their surroundings. We suggest a basic mathematical model, a strongly dissipative dynamical system, and formulate the conditions for the robustness and reproducibility of cognitive transients that satisfy the competing requirements for stability and flexibility. Based on this approach, we describe here an effective solution for the problem of sequential decision making, represented as a fixed time game: a player takes sequential actions in a changing noisy environment so as to maximize a cumulative reward. As we predict and verify in computer simulations, noise plays an important role in optimizing the gain. PMID:18452000

Transient survey rates for orphan afterglows from compact merger jets

NASA Astrophysics Data System (ADS)

Lamb, Gavin P.; Tanaka, Masaomi; Kobayashi, Shiho

2018-06-01

Orphan afterglows from short γ-ray bursts (GRBs) are potential candidates for electromagnetic (EM) counterpart searches to gravitational wave (GW) detected neutron star or neutron star black hole mergers. Various jet dynamical and structure models have been proposed that can be tested by the detection of a large sample of GW-EM counterparts. We make predictions for the expected rate of optical transients from these jet models for future survey telescopes, without a GW or GRB trigger. A sample of merger jets is generated in the redshift limits 0 ≤ z ≤ 3.0, and the expected peak r-band flux and time-scale above the Large Synoptic Survey Telescope (LSST) or Zwicky Transient Factory (ZTF) detection threshold, mr = 24.5 and 20.4, respectively, is calculated. General all-sky rates are shown for mr ≤ 26.0 and mr ≤ 21.0. The detected orphan and GRB afterglow rate depends on jet model, typically 16≲ R≲ 76 yr-1 for the LSST, and 2≲ R ≲ 8 yr-1 for ZTF. An excess in the rate of orphan afterglows for a survey to a depth of mr ≤ 26 would indicate that merger jets have a dominant low-Lorentz factor population, or the jets exhibit intrinsic jet structure. Careful filtering of transients is required to successfully identify orphan afterglows from either short- or long-GRB progenitors.

Finite element analysis of large transient elastic-plastic deformations of simple structures, with application to the engine rotor fragment containment/deflection problem

NASA Technical Reports Server (NTRS)

Wu, R. W.; Witmer, E. A.

1972-01-01

Assumed-displacement versions of the finite-element method are developed to predict large-deformation elastic-plastic transient deformations of structures. Both the conventional and a new improved finite-element variational formulation are derived. These formulations are then developed in detail for straight-beam and curved-beam elements undergoing (1) Bernoulli-Euler-Kirchhoff or (2) Timoshenko deformation behavior, in one plane. For each of these categories, several types of assumed-displacement finite elements are developed, and transient response predictions are compared with available exact solutions for small-deflection, linear-elastic transient responses. The present finite-element predictions for large-deflection elastic-plastic transient responses are evaluated via several beam and ring examples for which experimental measurements of transient strains and large transient deformations and independent finite-difference predictions are available.

Time scales of supercooled water and implications for reversible polyamorphism

NASA Astrophysics Data System (ADS)

Limmer, David T.; Chandler, David

2015-09-01

Deeply supercooled water exhibits complex dynamics with large density fluctuations, ice coarsening and characteristic time scales extending from picoseconds to milliseconds. Here, we discuss implications of these time scales as they pertain to two-phase coexistence and to molecular simulations of supercooled water. Specifically, we argue that it is possible to discount liquid-liquid criticality because the time scales imply that correlation lengths for such behaviour would be bounded by no more than a few nanometres. Similarly, it is possible to discount two-liquid coexistence because the time scales imply a bounded interfacial free energy that cannot grow in proportion to a macroscopic surface area. From time scales alone, therefore, we see that coexisting domains of differing density in supercooled water can be no more than nanoscale transient fluctuations.

Interannual Variability in the Position and Strength of the East Asian Jet Stream and Its Relation to Large - scale Circulation

NASA Astrophysics Data System (ADS)

Chan, Duo; Zhang, Yang; Wu, Qigang

2013-04-01

East Asian Jet Stream (EASJ) is charactered by obvious interannual variability in strength and position (latitude), with wide impacts on East Asian climate in all seasons. In this study, two indices are established to measure the interannual variability in intensity and position of EAJS. Possible causing factors, including both local signals and non-local large-scale circulation, are examined using NCAP-NCAR reanalysis data to investigate their relations with jet variation. Our analysis shows that the relationship between the interannual variations of EASJ and these factors depends on seasons. In the summer, both the intensity and position of EASJ are closely related to the meridional gradient of local surface temperature, but display no apparent relationship with the larg-scale circulation. In cold seasons (autumn, winter and spring), both the local factor and the large-scale circulation, i.e. the Pacific/North American teleconnection pattern (PNA), play important roles in the interannual variability of the jet intensity. The variability in the jet position, however, is more correlated to the Arctic Oscillation (AO), especially in winter. Diagnostic analysis indicates that transient eddy activity plays an important role in connecting the interannual variability of EASJ position with AO.

Modeling climate change impacts on groundwater resources using transient stochastic climatic scenarios

NASA Astrophysics Data System (ADS)

Goderniaux, Pascal; BrouyèRe, Serge; Blenkinsop, Stephen; Burton, Aidan; Fowler, Hayley J.; Orban, Philippe; Dassargues, Alain

2011-12-01

Several studies have highlighted the potential negative impact of climate change on groundwater reserves, but additional work is required to help water managers plan for future changes. In particular, existing studies provide projections for a stationary climate representative of the end of the century, although information is demanded for the near future. Such time-slice experiments fail to account for the transient nature of climatic changes over the century. Moreover, uncertainty linked to natural climate variability is not explicitly considered in previous studies. In this study we substantially improve upon the state-of-the-art by using a sophisticated transient weather generator in combination with an integrated surface-subsurface hydrological model (Geer basin, Belgium) developed with the finite element modeling software "HydroGeoSphere." This version of the weather generator enables the stochastic generation of large numbers of equiprobable climatic time series, representing transient climate change, and used to assess impacts in a probabilistic way. For the Geer basin, 30 equiprobable climate change scenarios from 2010 to 2085 have been generated for each of six different regional climate models (RCMs). Results show that although the 95% confidence intervals calculated around projected groundwater levels remain large, the climate change signal becomes stronger than that of natural climate variability by 2085. Additionally, the weather generator's ability to simulate transient climate change enabled the assessment of the likely time scale and associated uncertainty of a specific impact, providing managers with additional information when planning further investment. This methodology constitutes a real improvement in the field of groundwater projections under climate change conditions.

On the interplay between neoclassical tearing modes and nonlocal transport in toroidal plasmas

NASA Astrophysics Data System (ADS)

Ji, X. Q.; Xu, Y.; Hidalgo, C.; Diamond, P. H.; Liu, Yi; Pan, O.; Shi, Z. B.; Yu, D. L.

2016-09-01

This Letter presents the first observation on the interplay between nonlocal transport and neoclassical tearing modes (NTMs) during transient nonlocal heat transport events in the HL-2A tokamak. The nonlocality is triggered by edge cooling and large-scale, inward propagating avalanches. These lead to a locally enhanced pressure gradient at the q = 3/2 (or 2/1) rational surface and hence the onset of the NTM in relatively low β plasmas (βN < 1). The NTM, in return, regulates the nonlocal transport by truncation of avalanches by local sheared toroidal flows which develop near the magnetic island. These findings have direct implications for understanding the dynamic interaction between turbulence and large-scale mode structures in fusion plasmas.

Transient storage assessments of dye-tracer injections in rivers of the Willamette Basin, Oregon

USGS Publications Warehouse

Laenen, A.; Bencala, K.E.

2001-01-01

Rhodamine WT dye-tracer injections in rivers of the Willamette Basin yield concentration-time curves with characteristically long recession times suggestive of active transient storage processes. The scale of drainage areas contributing to the stream reaches studied in the Willamette Basin ranges from 10 to 12,000 km2. A transient storage assessment of the tracer studies has been completed using the U.S. Geological Survey's One-dimensional Transport with Inflow and Storage (OTIS) model, which incorporates storage exchange and decay functions along with the traditional dispersion and advection transport equation. The analysis estimates solute transport of the dye. It identifies first-order decay coefficients to be on the order of 10-5/sec for the nonconservative Rhodamine WT. On an individual subreach basis, the first-order decay is slower (typically by an order of magnitude) than the transient storage process, indicating that nonconservative tracers may be used to evaluate transient storage in rivers. In the transient storage analysis, a dimensionless parameter (As/A) expresses the spatial extent of storage zone area relative to stream cross section. In certain reaches of Willamette Basin pool-and-riffle, gravel-bed rivers, this parameter was as large as 0.5. A measure of the storage exchange flux was calculated for each stream subreach in the simulation analysis. This storage exchange is shown subjectively to be higher at higher stream discharges. Hyporheic linkage between streams and subsurface flows is the probable physical mechanism contributing to a significant part of this inferred active transient storage. Hyporheic linkages are further suggested by detailed measurements of river discharge with an Acoustic Doppler Current Profiler system delineating zones in two large rivers where water alternately enters and leaves the surface channels through graveland-cobble riverbeds. Measurements show patterns of hyporheic exchange that are highly variable in time and space.

Large-scale optimization-based non-negative computational framework for diffusion equations: Parallel implementation and performance studies

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

Chang, Justin; Karra, Satish; Nakshatrala, Kalyana B.

It is well-known that the standard Galerkin formulation, which is often the formulation of choice under the finite element method for solving self-adjoint diffusion equations, does not meet maximum principles and the non-negative constraint for anisotropic diffusion equations. Recently, optimization-based methodologies that satisfy maximum principles and the non-negative constraint for steady-state and transient diffusion-type equations have been proposed. To date, these methodologies have been tested only on small-scale academic problems. The purpose of this paper is to systematically study the performance of the non-negative methodology in the context of high performance computing (HPC). PETSc and TAO libraries are, respectively, usedmore » for the parallel environment and optimization solvers. For large-scale problems, it is important for computational scientists to understand the computational performance of current algorithms available in these scientific libraries. The numerical experiments are conducted on the state-of-the-art HPC systems, and a single-core performance model is used to better characterize the efficiency of the solvers. Furthermore, our studies indicate that the proposed non-negative computational framework for diffusion-type equations exhibits excellent strong scaling for real-world large-scale problems.« less

Large-scale optimization-based non-negative computational framework for diffusion equations: Parallel implementation and performance studies

DOE PAGES

Chang, Justin; Karra, Satish; Nakshatrala, Kalyana B.

2016-07-26

It is well-known that the standard Galerkin formulation, which is often the formulation of choice under the finite element method for solving self-adjoint diffusion equations, does not meet maximum principles and the non-negative constraint for anisotropic diffusion equations. Recently, optimization-based methodologies that satisfy maximum principles and the non-negative constraint for steady-state and transient diffusion-type equations have been proposed. To date, these methodologies have been tested only on small-scale academic problems. The purpose of this paper is to systematically study the performance of the non-negative methodology in the context of high performance computing (HPC). PETSc and TAO libraries are, respectively, usedmore » for the parallel environment and optimization solvers. For large-scale problems, it is important for computational scientists to understand the computational performance of current algorithms available in these scientific libraries. The numerical experiments are conducted on the state-of-the-art HPC systems, and a single-core performance model is used to better characterize the efficiency of the solvers. Furthermore, our studies indicate that the proposed non-negative computational framework for diffusion-type equations exhibits excellent strong scaling for real-world large-scale problems.« less

Stochastic downscaling of numerically simulated spatial rain and cloud fields using a transient multifractal approach

NASA Astrophysics Data System (ADS)

Nogueira, M.; Barros, A. P.; Miranda, P. M.

2012-04-01

Atmospheric fields can be extremely variable over wide ranges of spatial scales, with a scale ratio of 109-1010 between largest (planetary) and smallest (viscous dissipation) scale. Furthermore atmospheric fields with strong variability over wide ranges in scale most likely should not be artificially split apart into large and small scales, as in reality there is no scale separation between resolved and unresolved motions. Usually the effects of the unresolved scales are modeled by a deterministic bulk formula representing an ensemble of incoherent subgrid processes on the resolved flow. This is a pragmatic approach to the problem and not the complete solution to it. These models are expected to underrepresent the small-scale spatial variability of both dynamical and scalar fields due to implicit and explicit numerical diffusion as well as physically based subgrid scale turbulent mixing, resulting in smoother and less intermittent fields as compared to observations. Thus, a fundamental change in the way we formulate our models is required. Stochastic approaches equipped with a possible realization of subgrid processes and potentially coupled to the resolved scales over the range of significant scale interactions range provide one alternative to address the problem. Stochastic multifractal models based on the cascade phenomenology of the atmosphere and its governing equations in particular are the focus of this research. Previous results have shown that rain and cloud fields resulting from both idealized and realistic numerical simulations display multifractal behavior in the resolved scales. This result is observed even in the absence of scaling in the initial conditions or terrain forcing, suggesting that multiscaling is a general property of the nonlinear solutions of the Navier-Stokes equations governing atmospheric dynamics. Our results also show that the corresponding multiscaling parameters for rain and cloud fields exhibit complex nonlinear behavior depending on large scale parameters such as terrain forcing and mean atmospheric conditions at each location, particularly mean wind speed and moist stability. A particularly robust behavior found is the transition of the multiscaling parameters between stable and unstable cases, which has a clear physical correspondence to the transition from stratiform to organized (banded) convective regime. Thus multifractal diagnostics of moist processes are fundamentally transient and should provide a physically robust basis for the downscaling and sub-grid scale parameterizations of moist processes. Here, we investigate the possibility of using a simplified computationally efficient multifractal downscaling methodology based on turbulent cascades to produce statistically consistent fields at scales higher than the ones resolved by the model. Specifically, we are interested in producing rainfall and cloud fields at spatial resolutions necessary for effective flash flood and earth flows forecasting. The results are examined by comparing downscaled field against observations, and tendency error budgets are used to diagnose the evolution of transient errors in the numerical model prediction which can be attributed to aliasing.

Sequestering the standard model vacuum energy.

PubMed

Kaloper, Nemanja; Padilla, Antonio

2014-03-07

We propose a very simple reformulation of general relativity, which completely sequesters from gravity all of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically small. The idea is to make the dimensional parameters in the matter sector functionals of the 4-volume element of the Universe. For them to be nonzero, the Universe should be finite in spacetime. If this matter is the standard model of particle physics, our mechanism prevents any of its vacuum energy, classical or quantum, from sourcing the curvature of the Universe. The mechanism is consistent with the large hierarchy between the Planck scale, electroweak scale, and curvature scale, and early Universe cosmology, including inflation. Consequences of our proposal are that the vacuum curvature of an old and large universe is not zero, but very small, that w(DE) ≃ -1 is a transient, and that the Universe will collapse in the future.

Improvement of CFD Methods for Modeling Full Scale Circulating Fluidized Bed Combustion Systems

NASA Astrophysics Data System (ADS)

Shah, Srujal; Klajny, Marcin; Myöhänen, Kari; Hyppänen, Timo

With the currently available methods of computational fluid dynamics (CFD), the task of simulating full scale circulating fluidized bed combustors is very challenging. In order to simulate the complex fluidization process, the size of calculation cells should be small and the calculation should be transient with small time step size. For full scale systems, these requirements lead to very large meshes and very long calculation times, so that the simulation in practice is difficult. This study investigates the requirements of cell size and the time step size for accurate simulations, and the filtering effects caused by coarser mesh and longer time step. A modeling study of a full scale CFB furnace is presented and the model results are compared with experimental data.

Time-variable stress transfer across a megathrust from seismic to Wilson cycle scale

NASA Astrophysics Data System (ADS)

Rosenau, Matthias; Angiboust, Samuel; Moreno, Marcos; Schurr, Bernd; Oncken, Onno

2013-04-01

During the lifetime of a convergent plate margin stress transfer across the plate interface (a megathrust) can be expected to vary at multiple timescales. At short time scales (years to decades), a subduction megathrust interface appears coupled (accumulating shear stress) at shallow depth (seismogenic zone <350°C) in a laterally heterogeneous fashion. Highly coupled areas are prerequisite to areas of large slip (asperities) during future earthquakes but the correlation is rarely unequivocal suggesting that the coupling pattern is transient during the interseismic period. As temperature, structure and material properties are unlike to change at short time scales as well as at short distance along strike, fluid pressure change is invoked as the prime agent of lateral and time-variable stress transfer at short time (seismic cycle) scale and beyond. On longer time scales (up to Wilson cycles), additional agents of time-variable stress change are discussed. Shear tests using velocity weakening rock analogue material suggest that in a conditionally stable regime the effective normal load controls both the geodetic and the seismic coupling (fraction of convergence velocity accommodated by interseismic backslip/seismic slip). Accordingly seismic coupling decreases from 80% to 20% as the pore fluid pressure increases from hydrostatic to near-lithostatic. Moreover, the experiments demonstrate that at sub-seismic cycle scale the geodetic coupling (locking) is not only proportional to effective normal load but also to relative shear stress. For areas of near complete stress drop locking might systematically decrease over the interseismic period from >80-95 % shortly after an earthquake to backslip at significant fractions of plate convergence rate (<5-45 % locking) later in the seismic cycle. If we allow pore fluid pressures to change at sub-seismic cycle scale a single location along a megathrust may thus appear fully locked after an earthquake while fully unlocked before an earthquake. The mechanisms and timescales of fluid pressure changes along a megathrust are yet to be explored but a valid hypothesis seems to be that non-volcanic tremor and slow slip below the seismogenic zone represent short term episodes of metamorphic fluid infiltration into the shallow megathrust. A megathrust fault valve mechanism clocked by the greatest earthquakes then accounts for cyclic fluid pressure build up and drainage at sub-seismic cycle scale. As pore pressure dynamics are controlled primarily by permeability which in turn is controlled by structure and material properties, then more long term coupling transients associated with structural evolution of the plate margin can be implied. Fluid controlled transients might interfere with transients and secular trends resulting from changes in material strength and plate tectonic forces over the Wilson cycle resulting in a multispectral stress-transfer pattern associated with convergent margin evolution. Because of the viscous damping effect of the underlying asthenosphere, however, only longterm transients (periods >1-10 ka) are transmitted into the engaged plates. We therefore speculate that the multispectral nature of stress transfer across a megathrust filtered through the asthenosphere explains transient fault activity in some intraplate settings.

Status Of The Swift Burst Alert Telescope Hard X-ray Transient Monitor

NASA Astrophysics Data System (ADS)

Krimm, Hans A.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J.; Fenimore, E.; Gehrels, N.; Markwardt, C. B.; Palmer, D.; Sakamoto, T.; Skinner, G. K.; Stamatikos, M.; Tueller, J.

2010-01-01

The Swift Burst Alert Telescope hard X-ray transient monitor has been operating since October 1, 2006. More than 700 sources are tracked on a daily basis and light curves are produced and made available to the public on two time scales: a single Swift pointing (approximately 20 minutes) and the weighted average for each day. Of the monitored sources, approximately 33 are detected daily and another 100 have had one or more outburst during the Swift mission. The monitor is also sensitive to the detection of previously undiscovered sources and we have reported the discovery of four galactic sources and one source in the Large Magellanic Cloud. Follow-up target of opportunity observations with Swift and the Rossi X-Ray Timing Explorer have revealed that three of these new sources are pulsars and two are black hole candidates. In addition, the monitor has led to the announcement of significant outbursts from 24 different galactic and extra-galactic sources, many of which have had follow-up Swift XRT, UVOT and ground based multi-wavelength observations. The transient monitor web pages currently receive an average of 21 visits per day. We will report on the most important results from the transient monitor and also on detection and exposure statistics and outline recent and planned improvements to the monitor. The transient monitor web page is http://swift.gsfc.nasa.gov/docs/swift/results/transients/.

Rethinking hyporheic flow and transient storage to advance understanding of stream-catchment connections

USGS Publications Warehouse

Bencala, K.E.; Gooseff, M.N.; Kimball, B.A.

2011-01-01

Although surface water and groundwater are increasingly referred to as one resource, there remain environmental and ecosystem needs to study the 10 m to 1 km reach scale as one hydrologic system. Streams gain and lose water over a range of spatial and temporal scales. Large spatial scales (kilometers) have traditionally been recognized and studied as river-aquifer connections. Over the last 25 years hyporheic exchange flows (1-10 m) have been studied extensively. Often a transient storage model has been used to quantify the physical solute transport setting in which biogeochemical processes occur. At the longer 10 m to 1 km scale of stream reaches it is now clear that streams which gain water overall can coincidentally lose water to the subsurface. At this scale, the amounts of water transferred are not necessarily significant but the exchanges can, however, influence solute transport. The interpretation of seemingly straightforward questions about water, contaminant, and nutrient fluxes into and along a stream can be confounded by flow losses which are too small to be apparent in stream gauging and along flow paths too long to be detected in tracer experiments. We suggest basic hydrologic approaches, e.g., measurement of flow along the channel, surface and subsurface solute sampling, and routine measurements of the water table that, in our opinion, can be used to extend simple exchange concepts from the hyporheic exchange scale to a scale of stream-catchment connection. Copyright 2011 by the American Geophysical Union.

An Optimization Code for Nonlinear Transient Problems of a Large Scale Multidisciplinary Mathematical Model

NASA Astrophysics Data System (ADS)

Takasaki, Koichi

This paper presents a program for the multidisciplinary optimization and identification problem of the nonlinear model of large aerospace vehicle structures. The program constructs the global matrix of the dynamic system in the time direction by the p-version finite element method (pFEM), and the basic matrix for each pFEM node in the time direction is described by a sparse matrix similarly to the static finite element problem. The algorithm used by the program does not require the Hessian matrix of the objective function and so has low memory requirements. It also has a relatively low computational cost, and is suited to parallel computation. The program was integrated as a solver module of the multidisciplinary analysis system CUMuLOUS (Computational Utility for Multidisciplinary Large scale Optimization of Undense System) which is under development by the Aerospace Research and Development Directorate (ARD) of the Japan Aerospace Exploration Agency (JAXA).

40 CFR Appendix II to Part 1048 - Large Spark-ignition (SI) Composite Transient Cycle

Code of Federal Regulations, 2010 CFR

2010-07-01

... Transient Cycle II Appendix II to Part 1048 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY.... 1048, App. II Appendix II to Part 1048—Large Spark-ignition (SI) Composite Transient Cycle The following table shows the transient duty-cycle for engines that are not constant-speed engines, as described...

Interplanetary flow systems associated with cosmic ray modulation in 1977-1980

NASA Technical Reports Server (NTRS)

Burlaga, L. F.; Mcdonald, F. B.; Ness, N. F.; Schwenn, R.; Lazarus, A. J.; Mariani, F.

1984-01-01

The hydromagnetic flow configurations associated with the cosmic ray modulation in 1977-1980 were determined using solar wind plasma and magnetic field data from Voyager 1 and 2 and Helios 1. The modulation was related to two types of large-scale systems of flows: one containing a number of transients such as shocks and postshock flows, the other consisting primarily of a series of quasi-stationary flows following interaction regions containing a stream interface and often bounded by a forward-reverse shock pair. Each of three major episodes of cosmic ray modulation was associated with the passage of a system of transient flows. Plateaus in the cosmic ray intensity-time profile were associated with the passage of systems of corotating streams.

Settlement statistics of a granular layer composed of polyhedral particles

NASA Astrophysics Data System (ADS)

Quezada, Juan Carlos; Saussine, Gilles; Breul, Pierre; Radjai, Farhang

2013-06-01

We use 3D contact dynamics simulations to investigate the mechanical equilibrium and settlement of a granular material composed of irregular polyhedral particles confined between two horizontal frictional planes. We show that, as a consequence of mobilized wall-particle friction force at the top and bottom boundaries, the transient deformation induced by a constant vertical load increment is controlled by the aspect ratio (thickness over width) of the packing as well as the stress ratio. The transient deformation declines considerably for increasingly smaller aspect ratios and grows with the stress ratio. From the simulation data for a large number of independent configurations, we find that sample-to-sample fluctuations of the deformation have a broad distribution and they scale with the average deformation.

Field induced transient current in one-dimensional nanostructure

NASA Astrophysics Data System (ADS)

Sako, Tokuei; Ishida, Hiroshi

2018-07-01

Field-induced transient current in one-dimensional nanostructures has been studied by a model of an electron confined in a 1D attractive Gaussian potential subjected both to electrodes at the terminals and to an ultrashort pulsed oscillatory electric field with the central frequency ω and the FWHM pulse width Γ. The time-propagation of the electron wave packet has been simulated by integrating the time-dependent Schrödinger equation directly relying on the second-order symplectic integrator method. The transient current has been calculated as the flux of the probability density of the escaping wave packet emitted from the downstream side of the confining potential. When a static bias-field E0 is suddenly applied, the resultant transient current shows an oscillatory decay behavior with time followed by a minimum structure before converging to a nearly constant value. The ω-dependence of the integrated transient current induced by the pulsed electric field has shown an asymmetric resonance line-shape for large Γ while it shows a fringe pattern on the spectral line profile for small Γ. These observations have been rationalized on the basis of the energy-level structure and lifetime of the quasibound states in the bias-field modified confining potential obtained by the complex-scaling Fourier grid Hamiltonian method.

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

D'Huys, Otti, E-mail: otti.dhuys@phy.duke.edu; Haynes, Nicholas D.; Lohmann, Johannes

Autonomous Boolean networks are commonly used to model the dynamics of gene regulatory networks and allow for the prediction of stable dynamical attractors. However, most models do not account for time delays along the network links and noise, which are crucial features of real biological systems. Concentrating on two paradigmatic motifs, the toggle switch and the repressilator, we develop an experimental testbed that explicitly includes both inter-node time delays and noise using digital logic elements on field-programmable gate arrays. We observe transients that last millions to billions of characteristic time scales and scale exponentially with the amount of time delaysmore » between nodes, a phenomenon known as super-transient scaling. We develop a hybrid model that includes time delays along network links and allows for stochastic variation in the delays. Using this model, we explain the observed super-transient scaling of both motifs and recreate the experimentally measured transient distributions.« less

Large-Scale Experiments in Microbially Induced Calcite Precipitation (MICP): Reactive Transport Model Development and Prediction

NASA Astrophysics Data System (ADS)

Nassar, Mohamed K.; Gurung, Deviyani; Bastani, Mehrdad; Ginn, Timothy R.; Shafei, Babak; Gomez, Michael G.; Graddy, Charles M. R.; Nelson, Doug C.; DeJong, Jason T.

2018-01-01

Design of in situ microbially induced calcite precipitation (MICP) strategies relies on a predictive capability. To date much of the mathematical modeling of MICP has focused on small-scale experiments and/or one-dimensional flow in porous media, and successful parameterizations of models in these settings may not pertain to larger scales or to nonuniform, transient flows. Our objective in this article is to report on modeling to test our ability to predict behavior of MICP under controlled conditions in a meter-scale tank experiment with transient nonuniform transport in a natural soil, using independently determined parameters. Flow in the tank was controlled by three wells, via a complex cycle of injection/withdrawals followed by no-flow intervals. Different injection solution recipes were used in sequence for transport characterization, biostimulation, cementation, and groundwater rinse phases of the 17 day experiment. Reaction kinetics were calibrated using separate column experiments designed with a similar sequence of phases. This allowed for a parsimonious modeling approach with zero fitting parameters for the tank experiment. These experiments and data were simulated using PHT3-D, involving transient nonuniform flow, alternating low and high Damköhler reactive transport, and combined equilibrium and kinetically controlled biogeochemical reactions. The assumption that microbes mediating the reaction were exclusively sessile, and with constant activity, in conjunction with the foregoing treatment of the reaction network, provided for efficient and accurate modeling of the entire process leading to nonuniform calcite precipitation. This analysis suggests that under the biostimulation conditions applied here the assumption of steady state sessile biocatalyst suffices to describe the microbially mediated calcite precipitation.

Imaging different components of a tectonic tremor sequence in southwestern Japan using an automatic statistical detection and location method

NASA Astrophysics Data System (ADS)

Poiata, Natalia; Vilotte, Jean-Pierre; Bernard, Pascal; Satriano, Claudio; Obara, Kazushige

2018-02-01

In this study, we demonstrate the capability of an automatic network-based detection and location method to extract and analyse different components of tectonic tremor activity by analysing a 9-day energetic tectonic tremor sequence occurring at the down-dip extension of the subducting slab in southwestern Japan. The applied method exploits the coherency of multi-scale, frequency-selective characteristics of non-stationary signals recorded across the seismic network. Use of different characteristic functions, in the signal processing step of the method, allows to extract and locate the sources of short-duration impulsive signal transients associated with low-frequency earthquakes and of longer-duration energy transients during the tectonic tremor sequence. Frequency-dependent characteristic functions, based on higher-order statistics' properties of the seismic signals, are used for the detection and location of low-frequency earthquakes. This allows extracting a more complete (˜6.5 times more events) and time-resolved catalogue of low-frequency earthquakes than the routine catalogue provided by the Japan Meteorological Agency. As such, this catalogue allows resolving the space-time evolution of the low-frequency earthquakes activity in great detail, unravelling spatial and temporal clustering, modulation in response to tide, and different scales of space-time migration patterns. In the second part of the study, the detection and source location of longer-duration signal energy transients within the tectonic tremor sequence is performed using characteristic functions built from smoothed frequency-dependent energy envelopes. This leads to a catalogue of longer-duration energy sources during the tectonic tremor sequence, characterized by their durations and 3-D spatial likelihood maps of the energy-release source regions. The summary 3-D likelihood map for the 9-day tectonic tremor sequence, built from this catalogue, exhibits an along-strike spatial segmentation of the long-duration energy-release regions, matching the large-scale clustering features evidenced from the low-frequency earthquake's activity analysis. Further examination of the two catalogues showed that the extracted short-duration low-frequency earthquakes activity coincides in space, within about 10-15 km distance, with the longer-duration energy sources during the tectonic tremor sequence. This observation provides a potential constraint on the size of the longer-duration energy-radiating source region in relation with the clustering of low-frequency earthquakes activity during the analysed tectonic tremor sequence. We show that advanced statistical network-based methods offer new capabilities for automatic high-resolution detection, location and monitoring of different scale-components of tectonic tremor activity, enriching existing slow earthquakes catalogues. Systematic application of such methods to large continuous data sets will allow imaging the slow transient seismic energy-release activity at higher resolution, and therefore, provide new insights into the underlying multi-scale mechanisms of slow earthquakes generation.

Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

NASA Astrophysics Data System (ADS)

Li, Lee; Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang

2014-01-01

Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

Large-Scale Impact Cratering and Early Earth Evolution

NASA Technical Reports Server (NTRS)

Grieve, R. A. F.; Cintala, M. J.

1997-01-01

The surface of the Moon attests to the importance of large-scale impact in its early crustal evolution. Previous models of the effects of a massive bombardment on terrestrial crustal evolution have relied on analogies with the Moon, with allowances for the presence of water and a thinner lithosphere. It is now apparent that strict lunar-terrestrial analogies are incorrect because of the "differential scaling" of crater dimensions and melt volumes with event size and planetary gravity. Impact melt volumes and "ancient cavity dimensions for specific impacts were modeled according to previous procedures. In the terrestrial case, the melt volume (V(sub m)) exceeds that of the transient cavity (V(sub tc)) at diameters > or = 400 km. This condition is reached on the Moon only with transient cavity diameters > or = 3000 km, equivalent to whole Moon melting. The melt volumes in these large impact events are minimum estimates, since, at these sizes, the higher temperature of the target rocks at depth will increase melt production. Using the modification-scaling relation of Croft, a transient cavity diameter of about 400 km in the terrestrial environment corresponds to an expected final impact "basin" diameter of about 900 km. Such a "basin" would be comparable in dimensions to the lunar basin Orientale. This 900-km "basin" on the early Earth, however, would not have had the appearance of Orientale. It would have been essentially a melt pool, and, morphologically, would have had more in common with the palimpsests structures on Callisto and Ganymede. With the terrestrial equivalents to the large multiring basins of the Moon being manifested as muted palimpsest-like structures filled with impact melt, it is unlikely they played a role in establishing the freeboard on the early Earth. The composition of the massive impact melt sheets (> 10 (exp 7) cu km) produced in "basin-forming" events on the early Earth would have most likely ranged from basaltic to more mafic for the largest impacts, where the melt volume would have reached well into the mantle. Any contribution from adiabatic melting or shock heating of the asthenosphere would have had similar mafic compositions. The depth of the melt sheets is unknown but would have been in the multilkilometer range. Bodies of basaltic melt > or = 300 m thick differentiate in the terrestrial environment, with the degree of differentiation being a function of the thickness of the body. We therefore expect that these thick, closed-system melt pools would have differentiated into an ultramafic-mafic base and felsic top. If only 10% of the impact melt produced in a single event creating a 400-km diameter transient cavity evolved into felsic differentiates, they would be comparable in volume to the Columbia River basalts. It has been estimated that at least 200 impact events of this size or larger occurred on the early Earth during a period of heavy bombardment. We speculate that these massive differentiated melt sheets may have had a role in the formation of the initial felsic component of the Earth's crust. Additional information is contained in the original.

The scaling of complex craters

NASA Technical Reports Server (NTRS)

Croft, S. K.

1985-01-01

The empirical relation between the transient crater diameter (Dg) and final crater diameter (Dr) of complex craters and basins is estimated using cumulative terrace widths, central uplift diameters, continuous ejecta radii, and transient crater reconstructions determined from lunar and terrestrial impact structures. The ratio Dg/Dr is a power law function of Dr, decreasing uniformly from unity at the diameter of the simple-complex crater morphology transition to about 0.5 for large multiring basins like Imbrium on the moon. The empirical constants in the Dg/Dr relation are interpreted physically to mean that the position of the final rim relative to the transient crater, and hence the extent of collapse, is controlled or greatly influenced by the properties of the zone of dissociated material produced by the impact shock. The continuity of the Dg/Dr relation over the entire spectrum of morphologic types from complex craters to multiring basins implies that the rims of all these structures form in the same tectonic environment despite morphologic differences.

Open-source framework for power system transmission and distribution dynamics co-simulation

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

Huang, Renke; Fan, Rui; Daily, Jeff

The promise of the smart grid entails more interactions between the transmission and distribution networks, and there is an immediate need for tools to provide the comprehensive modelling and simulation required to integrate operations at both transmission and distribution levels. Existing electromagnetic transient simulators can perform simulations with integration of transmission and distribution systems, but the computational burden is high for large-scale system analysis. For transient stability analysis, currently there are only separate tools for simulating transient dynamics of the transmission and distribution systems. In this paper, we introduce an open source co-simulation framework “Framework for Network Co-Simulation” (FNCS), togethermore » with the decoupled simulation approach that links existing transmission and distribution dynamic simulators through FNCS. FNCS is a middleware interface and framework that manages the interaction and synchronization of the transmission and distribution simulators. Preliminary testing results show the validity and capability of the proposed open-source co-simulation framework and the decoupled co-simulation methodology.« less

Discrete Event Modeling and Massively Parallel Execution of Epidemic Outbreak Phenomena

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

Perumalla, Kalyan S; Seal, Sudip K

2011-01-01

In complex phenomena such as epidemiological outbreaks, the intensity of inherent feedback effects and the significant role of transients in the dynamics make simulation the only effective method for proactive, reactive or post-facto analysis. The spatial scale, runtime speed, and behavioral detail needed in detailed simulations of epidemic outbreaks make it necessary to use large-scale parallel processing. Here, an optimistic parallel execution of a new discrete event formulation of a reaction-diffusion simulation model of epidemic propagation is presented to facilitate in dramatically increasing the fidelity and speed by which epidemiological simulations can be performed. Rollback support needed during optimistic parallelmore » execution is achieved by combining reverse computation with a small amount of incremental state saving. Parallel speedup of over 5,500 and other runtime performance metrics of the system are observed with weak-scaling execution on a small (8,192-core) Blue Gene / P system, while scalability with a weak-scaling speedup of over 10,000 is demonstrated on 65,536 cores of a large Cray XT5 system. Scenarios representing large population sizes exceeding several hundreds of millions of individuals in the largest cases are successfully exercised to verify model scalability.« less

Transcranial magnetic stimulation-induced global propagation of transient phase resetting associated with directional information flow.

PubMed

Kawasaki, Masahiro; Uno, Yutaka; Mori, Jumpei; Kobata, Kenji; Kitajo, Keiichi

2014-01-01

Electroencephalogram (EEG) phase synchronization analyses can reveal large-scale communication between distant brain areas. However, it is not possible to identify the directional information flow between distant areas using conventional phase synchronization analyses. In the present study, we applied transcranial magnetic stimulation (TMS) to the occipital area in subjects who were resting with their eyes closed, and analyzed the spatial propagation of transient TMS-induced phase resetting by using the transfer entropy (TE), to quantify the causal and directional flow of information. The time-frequency EEG analysis indicated that the theta (5 Hz) phase locking factor (PLF) reached its highest value at the distant area (the motor area in this study), with a time lag that followed the peak of the transient PLF enhancements of the TMS-targeted area at the TMS onset. Phase-preservation index (PPI) analyses demonstrated significant phase resetting at the TMS-targeted area and distant area. Moreover, the TE from the TMS-targeted area to the distant area increased clearly during the delay that followed TMS onset. Interestingly, the time lags were almost coincident between the PLF and TE results (152 vs. 165 ms), which provides strong evidence that the emergence of the delayed PLF reflects the causal information flow. Such tendencies were observed only in the higher-intensity TMS condition, and not in the lower-intensity or sham TMS conditions. Thus, TMS may manipulate large-scale causal relationships between brain areas in an intensity-dependent manner. We demonstrated that single-pulse TMS modulated global phase dynamics and directional information flow among synchronized brain networks. Therefore, our results suggest that single-pulse TMS can manipulate both incoming and outgoing information in the TMS-targeted area associated with functional changes.

Prediction of Indian Summer-Monsoon Onset Variability: A Season in Advance.

PubMed

Pradhan, Maheswar; Rao, A Suryachandra; Srivastava, Ankur; Dakate, Ashish; Salunke, Kiran; Shameera, K S

2017-10-27

Monsoon onset is an inherent transient phenomenon of Indian Summer Monsoon and it was never envisaged that this transience can be predicted at long lead times. Though onset is precipitous, its variability exhibits strong teleconnections with large scale forcing such as ENSO and IOD and hence may be predictable. Despite of the tremendous skill achieved by the state-of-the-art models in predicting such large scale processes, the prediction of monsoon onset variability by the models is still limited to just 2-3 weeks in advance. Using an objective definition of onset in a global coupled ocean-atmosphere model, it is shown that the skillful prediction of onset variability is feasible under seasonal prediction framework. The better representations/simulations of not only the large scale processes but also the synoptic and intraseasonal features during the evolution of monsoon onset are the comprehensions behind skillful simulation of monsoon onset variability. The changes observed in convection, tropospheric circulation and moisture availability prior to and after the onset are evidenced in model simulations, which resulted in high hit rate of early/delay in monsoon onset in the high resolution model.

HFSB-seeding for large-scale tomographic PIV in wind tunnels

NASA Astrophysics Data System (ADS)

Caridi, Giuseppe Carlo Alp; Ragni, Daniele; Sciacchitano, Andrea; Scarano, Fulvio

2016-12-01

A new system for large-scale tomographic particle image velocimetry in low-speed wind tunnels is presented. The system relies upon the use of sub-millimetre helium-filled soap bubbles as flow tracers, which scatter light with intensity several orders of magnitude higher than micron-sized droplets. With respect to a single bubble generator, the system increases the rate of bubbles emission by means of transient accumulation and rapid release. The governing parameters of the system are identified and discussed, namely the bubbles production rate, the accumulation and release times, the size of the bubble injector and its location with respect to the wind tunnel contraction. The relations between the above parameters, the resulting spatial concentration of tracers and measurement of dynamic spatial range are obtained and discussed. Large-scale experiments are carried out in a large low-speed wind tunnel with 2.85 × 2.85 m2 test section, where a vertical axis wind turbine of 1 m diameter is operated. Time-resolved tomographic PIV measurements are taken over a measurement volume of 40 × 20 × 15 cm3, allowing the quantitative analysis of the tip-vortex structure and dynamical evolution.

Fixation, transient landscape, and diffusion dilemma in stochastic evolutionary game dynamics

NASA Astrophysics Data System (ADS)

Zhou, Da; Qian, Hong

2011-09-01

Agent-based stochastic models for finite populations have recently received much attention in the game theory of evolutionary dynamics. Both the ultimate fixation and the pre-fixation transient behavior are important to a full understanding of the dynamics. In this paper, we study the transient dynamics of the well-mixed Moran process through constructing a landscape function. It is shown that the landscape playing a central theoretical “device” that integrates several lines of inquiries: the stable behavior of the replicator dynamics, the long-time fixation, and continuous diffusion approximation associated with asymptotically large population. Several issues relating to the transient dynamics are discussed: (i) multiple time scales phenomenon associated with intra- and inter-attractoral dynamics; (ii) discontinuous transition in stochastically stationary process akin to Maxwell construction in equilibrium statistical physics; and (iii) the dilemma diffusion approximation facing as a continuous approximation of the discrete evolutionary dynamics. It is found that rare events with exponentially small probabilities, corresponding to the uphill movements and barrier crossing in the landscape with multiple wells that are made possible by strong nonlinear dynamics, plays an important role in understanding the origin of the complexity in evolutionary, nonlinear biological systems.

The Solsticial Pause on Mars. Part 1; A Planetary Wave Reanalysis

NASA Technical Reports Server (NTRS)

Lewis, Stephen R.; Mulholland, David P.; Read, Peter L.; Montabone, Luca; Wilson, R. John; Smith, Michael D.

2015-01-01

Large-scale planetary waves are diagnosed from an analysis of profiles retrieved from the Thermal Emission Spectrometer aboard the Mars Global Surveyor spacecraft during its scientific mapping phase. The analysis is conducted by assimilating thermal profiles and total dust opacity retrievals into a Mars global circulation model. Transient waves are largest throughout the northern hemisphere autumn, winter and spring period and almost absent during the summer. The southern hemisphere exhibits generally weaker transient wave behavior. A striking feature of the low-altitude transient waves in the analysis is that they show a broad subsidiary minimum in amplitude centred on the winter solstice, a period when the thermal contrast between the summer hemisphere and the winter pole is strongest and baroclinic wave activity might be expected to be strong. This behavior, here called the 'solsticial pause,' is present in every year of the analysis. This strong pause is under-represented in many independent model experiments, which tend to produce relatively uniform baroclinic wave activity throughout the winter. This paper documents and diagnoses the transient wave solsticial pause found in the analysis; a companion paper investigates the origin of the phenomenon in a series of model experiments.

A new look at ocean ventilation time scales and their uncertainties

NASA Astrophysics Data System (ADS)

Fine, Rana A.; Peacock, Synte; Maltrud, Mathew E.; Bryan, Frank O.

2017-05-01

A suite of eddy-resolving ocean transient tracer model simulations are first compared to observations. Observational and model pCFC-11 ages agree quite well, with the eddy-resolving model adding detail. The CFC ages show that the thermocline is a barrier to interior ocean exchange with the atmosphere on time scales of 45 years, the measureable CFC transient, although there are exceptions. Next, model simulations are used to quantify effects on tracer ages of the spatial dependence of internal ocean tracer variability due to stirring from eddies and biases from nonstationarity of the atmospheric transient when there is mixing. These add to tracer age uncertainties and biases, which are large in frontal boundary regions, and small in subtropical gyre interiors. These uncertainties and biases are used to reinterpret observed temporal trends in tracer-derived ventilation time scales taken from observations more than a decade apart, and to assess whether interpretations of changes in tracer ages being due to changes in ocean ventilation hold water. For the southern hemisphere subtropical gyres, we infer that the rate of ocean ventilation 26-27.2 σθ increased between the mid-1990s and the decade of the 2000s. However, between the mid-1990s and the decade of the 2010s, there is no significant trend—perhaps except for South Atlantic. Observed age/AOU/ventilation changes are linked to a combination of natural cycles and climate change, and there is regional variability. Thus, for the future it is not clear how strong or steady in space and time ocean ventilation changes will be.

A new look at ocean ventilation time scales and their uncertainties

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

Fine, Rana A.; Peacock, Synte; Maltrud, Mathew E.

A suite of eddy-resolving ocean transient tracer model simulations are first compared to observations. Observational and model pCFC-11 ages agree quite well, with the eddy-resolving model adding detail. The CFC ages show that the thermocline is a barrier to interior ocean exchange with the atmosphere on time scales of 45 years, the measureable CFC transient, although there are exceptions. Next, model simulations are used to quantify effects on tracer ages of the spatial dependence of internal ocean tracer variability due to stirring from eddies and biases from nonstationarity of the atmospheric transient when there is mixing. These add to tracermore » age uncertainties and biases, which are large in frontal boundary regions, and small in subtropical gyre interiors. These uncertainties and biases are used to reinterpret observed temporal trends in tracer-derived ventilation time scales taken from observations more than a decade apart, and to assess whether interpretations of changes in tracer ages being due to changes in ocean ventilation hold water. For the southern hemisphere subtropical gyres, we infer that the rate of ocean ventilation 26–27.2 σ θ increased between the mid-1990s and the decade of the 2000s. However, between the mid-1990s and the decade of the 2010s, there is no significant trend—perhaps except for South Atlantic. Observed age/AOU/ventilation changes are linked to a combination of natural cycles and climate change, and there is regional variability. Thus, for the future it is not clear how strong or steady in space and time ocean ventilation changes will be.« less

A new look at ocean ventilation time scales and their uncertainties

DOE PAGES

Fine, Rana A.; Peacock, Synte; Maltrud, Mathew E.; ...

2017-03-17

A suite of eddy-resolving ocean transient tracer model simulations are first compared to observations. Observational and model pCFC-11 ages agree quite well, with the eddy-resolving model adding detail. The CFC ages show that the thermocline is a barrier to interior ocean exchange with the atmosphere on time scales of 45 years, the measureable CFC transient, although there are exceptions. Next, model simulations are used to quantify effects on tracer ages of the spatial dependence of internal ocean tracer variability due to stirring from eddies and biases from nonstationarity of the atmospheric transient when there is mixing. These add to tracermore » age uncertainties and biases, which are large in frontal boundary regions, and small in subtropical gyre interiors. These uncertainties and biases are used to reinterpret observed temporal trends in tracer-derived ventilation time scales taken from observations more than a decade apart, and to assess whether interpretations of changes in tracer ages being due to changes in ocean ventilation hold water. For the southern hemisphere subtropical gyres, we infer that the rate of ocean ventilation 26–27.2 σ θ increased between the mid-1990s and the decade of the 2000s. However, between the mid-1990s and the decade of the 2010s, there is no significant trend—perhaps except for South Atlantic. Observed age/AOU/ventilation changes are linked to a combination of natural cycles and climate change, and there is regional variability. Thus, for the future it is not clear how strong or steady in space and time ocean ventilation changes will be.« less

Population-based case-control study of white matter changes on brain imaging in transient ischemic attack and ischemic stroke.

PubMed

Li, Linxin; Simoni, Michela; Küker, Wilhelm; Schulz, Ursula G; Christie, Sharon; Wilcock, Gordon K; Rothwell, Peter M

2013-11-01

White matter changes (WMC) are a common finding on brain imaging and are associated with an increased risk of ischemic stroke. They are most frequent in small vessel stroke; however, in the absence of comparisons with normal controls, it is uncertain whether WMC are also more frequent than expected in other stroke subtypes. Therefore, we compared WMC in pathogenic subtypes of ischemic stroke versus controls in a population-based study. We evaluated the presence and severity of WMC on computed tomography and on magnetic resonance brain imaging using modified Blennow/Fazekas scale and age-related white matter changes scale, respectively, in a population-based study of patients with incident transient ischemic attack or ischemic stroke (Oxford Vascular Study) and in a study of local controls (Oxford Project to Investigate Memory and Ageing) without history of transient ischemic attack or ischemic stroke, with stratification by stroke pathogenesis (Trial of Org10172 in Acute Stroke Treatment classification). Among 1601 consecutive eligible patients with first-ever ischemic events, 1453 patients had computed tomography brain imaging, 562 had magnetic resonance imaging, and 414 patients had both. Compared with 313 controls (all with computed tomography and 131 with magnetic resonance imaging) and after adjustment for age, sex, diabetes mellitus, and hypertension, moderate/severe WMC (age-related white matter changes scale) were more frequent in patients with small vessel events (odds ratio, 3.51 [95% confidence interval, 2.13-5.76]; P<0.0001) but not in large artery (odds ratio, 1.03 [95% confidence interval, 0.64-1.67]), cardioembolic (odds ratio, 0.87 [95% confidence interval, 0.56-1.34]), or undetermined (odds ratio, 0.90 [95% confidence interval, 0.62-1.30]) subtypes. Results were consistent for ischemic stroke and transient ischemic attack, for other scales, and for magnetic resonance imaging and computed tomography separately. In contrast to small vessel ischemic events, WMC were not independently associated with other pathogenic subtypes, suggesting that WMC are unlikely to be an independent risk factor for nonsmall vessel events.

Respiratory syncytial virus subunit vaccine based on a recombinant fusion protein expressed transiently in mammalian cells.

PubMed

Nallet, Sophie; Amacker, Mario; Westerfeld, Nicole; Baldi, Lucia; König, Iwo; Hacker, David L; Zaborosch, Christiane; Zurbriggen, Rinaldo; Wurm, Florian M

2009-10-30

Although respiratory syncytial virus (RSV) causes severe lower respiratory tract infection in infants and adults at risk, no RSV vaccine is currently available. In this report, efforts toward the generation of an RSV subunit vaccine using recombinant RSV fusion protein (rRSV-F) are described. The recombinant protein was produced by transient gene expression (TGE) in suspension-adapted human embryonic kidney cells (HEK-293E) in 4 L orbitally shaken bioreactors. It was then purified and formulated in immunostimulating reconstituted influenza virosomes (IRIVs). The candidate vaccine induced anti-RSV-F neutralizing antibodies in mice, and challenge studies in cotton rats are ongoing. If successful in preclinical and clinical trials, this will be the first recombinant subunit vaccine produced by large-scale TGE in mammalian cells.

Experimental evidence for a transient Tayler instability in a cylindrical liquid-metal column.

PubMed

Seilmayer, Martin; Stefani, Frank; Gundrum, Thomas; Weier, Tom; Gerbeth, Gunter; Gellert, Marcus; Rüdiger, Günther

2012-06-15

In the current-driven, kink-type Tayler instability (TI) a sufficiently strong azimuthal magnetic field becomes unstable against nonaxisymmetric perturbations. The TI has been discussed as a possible ingredient of the solar dynamo mechanism and a source of the helical structures in cosmic jets. It is also considered as a size-limiting factor for liquid metal batteries. We report on a liquid metal TI experiment using a cylindrical column of the eutectic alloy GaInSn to which electrical currents of up to 8 kA are applied. We present results of external magnetic field measurements that indicate the transient occurrence of the TI in good agreement with numerical predictions. The interference of TI with the competing large-scale convection, resulting from Joule heating, is also discussed.

Hurricane feedback research may improve intensity forecasts

NASA Astrophysics Data System (ADS)

Schultz, Colin

2012-06-01

Forecasts of a hurricane's intensity are generally much less accurate than forecasts of its most likely path. Large-scale atmospheric patterns dictate where a hurricane will go and how quickly it will get there. The storm's intensity, however, depends on small-scale shifts in atmospheric stratification, upwelling rates, and other transient dynamics that are difficult to predict. Properly understanding the risk posed by an impending storm depends on having a firm grasp of all three properties: translational speed, intensity, and path. Drawing on 40 years of hurricane records representing 3090 different storms, Mei et al. propose that a hurricane's translational speed and intensity may be closely linked.

Sensitivity quantification of remote detection NMR and MRI

NASA Astrophysics Data System (ADS)

Granwehr, J.; Seeley, J. A.

2006-04-01

A sensitivity analysis is presented of the remote detection NMR technique, which facilitates the spatial separation of encoding and detection of spin magnetization. Three different cases are considered: remote detection of a transient signal that must be encoded point-by-point like a free induction decay, remote detection of an experiment where the transient dimension is reduced to one data point like phase encoding in an imaging experiment, and time-of-flight (TOF) flow visualization. For all cases, the sensitivity enhancement is proportional to the relative sensitivity between the remote detector and the circuit that is used for encoding. It is shown for the case of an encoded transient signal that the sensitivity does not scale unfavorably with the number of encoded points compared to direct detection. Remote enhancement scales as the square root of the ratio of corresponding relaxation times in the two detection environments. Thus, remote detection especially increases the sensitivity of imaging experiments of porous materials with large susceptibility gradients, which cause a rapid dephasing of transverse spin magnetization. Finally, TOF remote detection, in which the detection volume is smaller than the encoded fluid volume, allows partial images corresponding to different time intervals between encoding and detection to be recorded. These partial images, which contain information about the fluid displacement, can be recorded, in an ideal case, with the same sensitivity as the full image detected in a single step with a larger coil.

Contrasting effects of climatic variability on the demography of a trans-equatorial migratory seabird.

PubMed

Genovart, Meritxell; Sanz-Aguilar, Ana; Fernández-Chacón, Albert; Igual, Jose M; Pradel, Roger; Forero, Manuela G; Oro, Daniel

2013-01-01

Large-scale seasonal climatic indices, such as the North Atlantic Oscillation (NAO) index or the Southern Oscillation Index (SOI), account for major variations in weather and climate around the world and may influence population dynamics in many organisms. However, assessing the extent of climate impacts on species and their life-history traits requires reliable quantitative statistical approaches. We used a new analytical tool in mark-recapture, the multi-event modelling, to simultaneously assess the influence of climatic variation on multiple demographic parameters (i.e. adult survival, transient probability, reproductive skipping and nest dispersal) at two Mediterranean colonies of the Cory's shearwater Calonectris diomedea, a trans-equatorial migratory long-lived seabird. We also analysed the impact of climate in the breeding success at the two colonies. We found a clear temporal variation of survival for Cory's shearwaters, strongly associated to the large-scale SOI especially in one of the colonies (up to 66% of variance explained). Atlantic hurricane season is modulated by the SOI and coincides with shearwater migration to their wintering areas, directly affecting survival probabilities. However, the SOI was a better predictor of survival probabilities than the frequency of hurricanes; thus, we cannot discard an indirect additive effect of SOI via food availability. Accordingly, the proportion of transients was also correlated with SOI values, indicating higher costs of first reproduction (resulting in either mortality or permanent dispersal) when bad environmental conditions occurred during winter before reproduction. Breeding success was also affected by climatic factors, the NAO explaining c. 41% of variance, probably as a result of its effect in the timing of peak abundance of squid and small pelagics, the main prey for shearwaters. No climatic effect was found either on reproductive skipping or on nest dispersal. Contrarily to what we expect for a long-lived organism, large-scale climatic indexes had a more pronounced effect on survival and transient probabilities than on less sensitive fitness parameters such reproductive skipping or nest dispersal probabilities. The potential increase in hurricane frequency because of global warming may interact with other global change agents (such as incidental bycatch and predation by alien species) nowadays impacting shearwaters, affecting future viability of populations. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Modeling Mars Cyclogenesis and Frontal Waves: Seasonal Variations and Implications on Dust Activity

NASA Technical Reports Server (NTRS)

Hollingsworth, J. L.; Kahre, M. A.

2014-01-01

Between late autumn through early spring,middle and high latitudes onMars exhibit strong equator-to-polemean temperature contrasts (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that such strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e., transient synoptic period waves) [1, 2]. For a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, these large-scale, extratropical weather disturbances are critical components of the global circulation. The wave-like disturbances serve as agents in the transport of heat and momentum between low and high latitudes of the planet. Through cyclonic/anticyclonic winds, intense shear deformations, contractions-dilatations in temperature and density, and sharp perturbations amongst atmospheric tracers (i.e., dust, volatiles (e.g., water vapor) and condensates (e.g., water-ice cloud particles)), Mars' extratropical weather systems have significant sub-synoptic scale ramifications by supporting atmospheric frontal waves (Fig. 1).

Extratropical Cyclogenesis and Frontal Waves on Mars: Influences on Dust, Weather and the Planet's climate

NASA Technical Reports Server (NTRS)

Hollingsworth, J. L.; Kahre, Melinda A.

2012-01-01

Between late autumn and early spring, middle and high latitudes on Mars exhibit strong equatortopole mean temperature contrasts (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e., transient synoptic periodwaves) [1,2]. For a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, these large-scale, extratropical weather disturbances are critical components of the global circulation. The wavelike disturbances act as agents in the transport of heat and momentum between low and high latitudes of the planet. Through cyclonic/anticyclonic winds, intense shear deformations, contractions-dilatations in temperature and density, and sharp perturbations amongst atmospheric tracers (i.e., dust, volatiles (e.g., water vapor) and condensates (e.g., water-ice cloud particles)), Mars extratropical weather systems have significant subsynoptic scale ramifications by supporting atmospheric frontal waves (Fig. 1).

Fault Modeling of Extreme Scale Applications Using Machine Learning

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

Vishnu, Abhinav; Dam, Hubertus van; Tallent, Nathan R.

Faults are commonplace in large scale systems. These systems experience a variety of faults such as transient, permanent and intermittent. Multi-bit faults are typically not corrected by the hardware resulting in an error. Here, this paper attempts to answer an important question: Given a multi-bit fault in main memory, will it result in an application error — and hence a recovery algorithm should be invoked — or can it be safely ignored? We propose an application fault modeling methodology to answer this question. Given a fault signature (a set of attributes comprising of system and application state), we use machinemore » learning to create a model which predicts whether a multibit permanent/transient main memory fault will likely result in error. We present the design elements such as the fault injection methodology for covering important data structures, the application and system attributes which should be used for learning the model, the supervised learning algorithms (and potentially ensembles), and important metrics. Lastly, we use three applications — NWChem, LULESH and SVM — as examples for demonstrating the effectiveness of the proposed fault modeling methodology.« less

Fault Modeling of Extreme Scale Applications Using Machine Learning

DOE PAGES

Vishnu, Abhinav; Dam, Hubertus van; Tallent, Nathan R.; ...

2016-05-01

Faults are commonplace in large scale systems. These systems experience a variety of faults such as transient, permanent and intermittent. Multi-bit faults are typically not corrected by the hardware resulting in an error. Here, this paper attempts to answer an important question: Given a multi-bit fault in main memory, will it result in an application error — and hence a recovery algorithm should be invoked — or can it be safely ignored? We propose an application fault modeling methodology to answer this question. Given a fault signature (a set of attributes comprising of system and application state), we use machinemore » learning to create a model which predicts whether a multibit permanent/transient main memory fault will likely result in error. We present the design elements such as the fault injection methodology for covering important data structures, the application and system attributes which should be used for learning the model, the supervised learning algorithms (and potentially ensembles), and important metrics. Lastly, we use three applications — NWChem, LULESH and SVM — as examples for demonstrating the effectiveness of the proposed fault modeling methodology.« less

The nature of micro CMEs within coronal holes

NASA Astrophysics Data System (ADS)

Bothmer, Volker; Nistico, Giuseppe; Zimbardo, Gaetano; Patsourakos, Spiros; Bosman, Eckhard

Whilst investigating the origin and characteristics of coronal jets and large-scale CMEs identi-fied in data from the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) instrument suites on board the two STEREO satellites, we discovered transient events that originated in the low corona with a morphology resembling that of typical three-part struc-tured coronal mass ejections (CMEs). However, the CMEs occurred on considerably smaller spatial scales. In this presentation we show evidence for the existence of small-scale CMEs from inside coronal holes and present quantitative estimates of their speeds and masses. We interprete the origin and evolution of micro CMEs as a natural consequence of the emergence of small-scale magnetic bipoles related to the Sun's ever changing photospheric magnetic flux on various scales and their interactions with the ambient plasma and magnetic field. The analysis of CMEs is performed within the framework of the EU Erasmus and FP7 SOTERIA projects.

Universality from disorder in the random-bond Blume-Capel model

NASA Astrophysics Data System (ADS)

Fytas, N. G.; Zierenberg, J.; Theodorakis, P. E.; Weigel, M.; Janke, W.; Malakis, A.

2018-04-01

Using high-precision Monte Carlo simulations and finite-size scaling we study the effect of quenched disorder in the exchange couplings on the Blume-Capel model on the square lattice. The first-order transition for large crystal-field coupling is softened to become continuous, with a divergent correlation length. An analysis of the scaling of the correlation length as well as the susceptibility and specific heat reveals that it belongs to the universality class of the Ising model with additional logarithmic corrections which is also observed for the Ising model itself if coupled to weak disorder. While the leading scaling behavior of the disordered system is therefore identical between the second-order and first-order segments of the phase diagram of the pure model, the finite-size scaling in the ex-first-order regime is affected by strong transient effects with a crossover length scale L*≈32 for the chosen parameters.

Parallel Visualization Co-Processing of Overnight CFD Propulsion Applications

NASA Technical Reports Server (NTRS)

Edwards, David E.; Haimes, Robert

1999-01-01

An interactive visualization system pV3 is being developed for the investigation of advanced computational methodologies employing visualization and parallel processing for the extraction of information contained in large-scale transient engineering simulations. Visual techniques for extracting information from the data in terms of cutting planes, iso-surfaces, particle tracing and vector fields are included in this system. This paper discusses improvements to the pV3 system developed under NASA's Affordable High Performance Computing project.

Transient and diffusion analysis of HgCdTe

NASA Technical Reports Server (NTRS)

Clayton, J. C.

1982-01-01

Solute redistribution during directional solidification of HgCdTe is addressed. Both one-dimensional and two-dimensional models for solute redistribution are treated and model results compared to experiment. The central problem studied is the cause of radial inhomogeneities found in directionally solidified HgCdTe. A large scale gravity-driven interface instability, termed shape instability, is postulated to be the cause of radial inhomogeneities. Recommendations for future work, along with appropriate computer programs, are included.

Efficient production of human acidic fibroblast growth factor in pea (Pisum sativum L.) plants by agroinfection of germinated seeds

PubMed Central

2011-01-01

Background For efficient and large scale production of recombinant proteins in plants transient expression by agroinfection has a number of advantages over stable transformation. Simple manipulation, rapid analysis and high expression efficiency are possible. In pea, Pisum sativum, a Virus Induced Gene Silencing System using the pea early browning virus has been converted into an efficient agroinfection system by converting the two RNA genomes of the virus into binary expression vectors for Agrobacterium transformation. Results By vacuum infiltration (0.08 Mpa, 1 min) of germinating pea seeds with 2-3 cm roots with Agrobacteria carrying the binary vectors, expression of the gene for Green Fluorescent Protein as marker and the gene for the human acidic fibroblast growth factor (aFGF) was obtained in 80% of the infiltrated developing seedlings. Maximal production of the recombinant proteins was achieved 12-15 days after infiltration. Conclusions Compared to the leaf injection method vacuum infiltration of germinated seeds is highly efficient allowing large scale production of plants transiently expressing recombinant proteins. The production cycle of plants for harvesting the recombinant protein was shortened from 30 days for leaf injection to 15 days by applying vacuum infiltration. The synthesized aFGF was purified by heparin-affinity chromatography and its mitogenic activity on NIH 3T3 cells confirmed to be similar to a commercial product. PMID:21548923

Robust production of virus-like particles and monoclonal antibodies with geminiviral replicon vectors in lettuce

PubMed Central

Lai, Huafang; He, Junyun; Engle, Michael; Diamond, Michael S.; Chen, Qiang

2011-01-01

Summary Pharmaceutical protein production in plants has been greatly promoted by the development of viral-based vectors and transient expression systems. Tobacco and related Nicotiana species are currently the most common host plants for generation of plant-made pharmaceutical proteins (PMPs). Downstream processing of target PMPs from these plants, however, is hindered by potential technical and regulatory difficulties due to the presence of high levels of phenolics and toxic alkaloids. Here, we explored the use of lettuce, which grows quickly yet produces low levels of secondary metabolites, and viral vector-based transient expression systems to develop a robust PMP production platform. Our results showed that a geminiviral replicon system based on the bean yellow dwarf virus permits high-level expression in lettuce of virus-like particles (VLP) derived from the Norwalk virus capsid protein and therapeutic monoclonal antibodies (mAbs) against Ebola and West Nile viruses. These vaccine and therapeutic candidates can be readily purified from lettuce leaves with scalable processing methods while fully retaining functional activity. Furthermore, this study also demonstrated the feasibility of using commercially produced lettuce for high-level PMP production. This allows our production system to have access to unlimited quantities of inexpensive plant material for large-scale production. These results establish a new production platform for biological pharmaceutical agents that is effective, safe, low-cost, and amenable to large-scale manufacturing. PMID:21883868

3D ion-scale dynamics of BBFs and their associated emissions in Earth's magnetotail using 3D hybrid simulations and MMS multi-spacecraft observations

NASA Astrophysics Data System (ADS)

Breuillard, H.; Aunai, N.; Le Contel, O.; Catapano, F.; Alexandrova, A.; Retino, A.; Cozzani, G.; Gershman, D. J.; Giles, B. L.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Strangeway, R. J.; Russell, C. T.; Magnes, W.; Plaschke, F.; Nakamura, R.; Fuselier, S. A.; Turner, D. L.; Schwartz, S. J.; Torbert, R. B.; Burch, J.

2017-12-01

Transient and localized jets of hot plasma, also known as Bursty Bulk Flows (BBFs), play a crucial role in Earth's magnetotail dynamics because the energy input from the solar wind is partly dissipated in their vicinity, notably in their embedded dipolarization front (DF). This dissipation is in the form of strong low-frequency waves that can heat and accelerate energetic particles up to the high-latitude plasma sheet. The ion-scale dynamics of BBFs have been revealed by the Cluster and THEMIS multi-spacecraft missions. However, the dynamics of BBF propagation in the magnetotail are still under debate due to instrumental limitations and spacecraft separation distances, as well as simulation limitations. The NASA/MMS fleet, which features unprecedented high time resolution instruments and four spacecraft separated by kinetic-scale distances, has also shown recently that the DF normal dynamics and its associated emissions are below the ion gyroradius scale in this region. Large variations in the dawn-dusk direction were also observed. However, most of large-scale simulations are using the MHD approach and are assumed 2D in the XZ plane. Thus, in this study we take advantage of both multi-spacecraft observations by MMS and large-scale 3D hybrid simulations to investigate the 3D dynamics of BBFs and their associated emissions at ion-scale in Earth's magnetotail, and their impact on particle heating and acceleration.

The advantages and disadvantages of using the TREAT reactor for nuclear laser experiments

NASA Astrophysics Data System (ADS)

Dickson, P. W.; Snyder, A. M.; Imel, G. R.; McConnell, R. J.

The Transient Reactor Test Facility (TREAT) is a large air-cooled test facility located at the Idaho National Engineering Laboratory. Two of the major design features of TREAT, its large size and its being an air-cooled reactor, provide clues to both its advantages and disadvantages for supporting nuclear laser experiments. Its large size, which is dictated by the dilute uranium/graphite fuel, permits accommodation of geometrically large experiments. However, TREAT's large size also results in relatively long transients so that the energy deposited in an experiment is large relative to the peak power available from the reactor. TREAT's air-cooling mode of operation allows its configuration to be changed fairly readily. Due to air cooling, the reactor cools down slowly, permitting only one full power transient a day, which can be a disadvantage in some experimental programs. The reactor is capable of both steady-state or transient operation.

Dynamics of Large-scale Coronal Structures as Imaged during the 2012 and 2013 Total Solar Eclipses

NASA Astrophysics Data System (ADS)

Alzate, Nathalia; Habbal, Shadia R.; Druckmüller, Miloslav; Emmanouilidis, Constantinos; Morgan, Huw

2017-10-01

White light images acquired at the peak of solar activity cycle 24, during the total solar eclipses of 2012 November 13 and 2013 November 3, serendipitously captured erupting prominences accompanied by CMEs. Application of state-of-the-art image processing techniques revealed the intricate details of two “atypical” large-scale structures, with strikingly sharp boundaries. By complementing the processed white light eclipse images with processed images from co-temporal Solar Dynamics Observatory/AIA and SOHO/LASCO observations, we show how the shape of these atypical structures matches the shape of faint CME shock fronts, which traversed the inner corona a few hours prior to the eclipse observations. The two events were not associated with any prominence eruption but were triggered by sudden brightening events on the solar surface accompanied by sprays and jets. The discovery of the indelible impact that frequent and innocuous transient events in the low corona can have on large-scale coronal structures was enabled by the radial span of the high-resolution white light eclipse images, starting from the solar surface out to several solar radii, currently unmatched by any coronagraphic instrumentation. These findings raise the interesting question as to whether large-scale coronal structures can ever be considered stationary. They also point to the existence of a much larger number of CMEs that goes undetected from the suite of instrumentation currently observing the Sun.

Oscillatory mechanisms of process binding in memory.

PubMed

Klimesch, Wolfgang; Freunberger, Roman; Sauseng, Paul

2010-06-01

A central topic in cognitive neuroscience is the question, which processes underlie large scale communication within and between different neural networks. The basic assumption is that oscillatory phase synchronization plays an important role for process binding--the transient linking of different cognitive processes--which may be considered a special type of large scale communication. We investigate this question for memory processes on the basis of different types of oscillatory synchronization mechanisms. The reviewed findings suggest that theta and alpha phase coupling (and phase reorganization) reflect control processes in two large memory systems, a working memory and a complex knowledge system that comprises semantic long-term memory. It is suggested that alpha phase synchronization may be interpreted in terms of processes that coordinate top-down control (a process guided by expectancy to focus on relevant search areas) and access to memory traces (a process leading to the activation of a memory trace). An analogous interpretation is suggested for theta oscillations and the controlled access to episodic memories. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Potential for large-scale solar collector system to offset carbon-based heating in the Ontario greenhouse sector

NASA Astrophysics Data System (ADS)

Semple, Lucas M.; Carriveau, Rupp; Ting, David S.-K.

2018-04-01

In the Ontario greenhouse sector the misalignment of available solar radiation during the summer months and large heating demand during the winter months makes solar thermal collector systems an unviable option without some form of seasonal energy storage. Information obtained from Ontario greenhouse operators has shown that over 20% of annual natural gas usage occurs during the summer months for greenhouse pre-heating prior to sunrise. A transient model of the greenhouse microclimate and indoor conditioning systems is carried out using TRNSYS software and validated with actual natural gas usage data. A large-scale solar thermal collector system is then incorporated and found to reduce the annual heating energy demand by approximately 35%. The inclusion of the collector system correlates to a reduction of about 120 tonnes of CO2 equivalent emissions per acre of greenhouse per year. System payback period is discussed considering the benefits of a future Ontario carbon tax.

A large-scale circuit mechanism for hierarchical dynamical processing in the primate cortex

PubMed Central

Chaudhuri, Rishidev; Knoblauch, Kenneth; Gariel, Marie-Alice; Kennedy, Henry; Wang, Xiao-Jing

2015-01-01

We developed a large-scale dynamical model of the macaque neocortex, which is based on recently acquired directed- and weighted-connectivity data from tract-tracing experiments, and which incorporates heterogeneity across areas. A hierarchy of timescales naturally emerges from this system: sensory areas show brief, transient responses to input (appropriate for sensory processing), whereas association areas integrate inputs over time and exhibit persistent activity (suitable for decision-making and working memory). The model displays multiple temporal hierarchies, as evidenced by contrasting responses to visual versus somatosensory stimulation. Moreover, slower prefrontal and temporal areas have a disproportionate impact on global brain dynamics. These findings establish a circuit mechanism for “temporal receptive windows” that are progressively enlarged along the cortical hierarchy, suggest an extension of time integration in decision-making from local to large circuits, and should prompt a re-evaluation of the analysis of functional connectivity (measured by fMRI or EEG/MEG) by taking into account inter-areal heterogeneity. PMID:26439530

An Eulerian time filtering technique to study large-scale transient flow phenomena

NASA Astrophysics Data System (ADS)

Vanierschot, Maarten; Persoons, Tim; van den Bulck, Eric

2009-10-01

Unsteady fluctuating velocity fields can contain large-scale periodic motions with frequencies well separated from those of turbulence. Examples are the wake behind a cylinder or the processing vortex core in a swirling jet. These turbulent flow fields contain large-scale, low-frequency oscillations, which are obscured by turbulence, making it impossible to identify them. In this paper, we present an Eulerian time filtering (ETF) technique to extract the large-scale motions from unsteady statistical non-stationary velocity fields or flow fields with multiple phenomena that have sufficiently separated spectral content. The ETF method is based on non-causal time filtering of the velocity records in each point of the flow field. It is shown that the ETF technique gives good results, similar to the ones obtained by the phase-averaging method. In this paper, not only the influence of the temporal filter is checked, but also parameters such as the cut-off frequency and sampling frequency of the data are investigated. The technique is validated on a selected set of time-resolved stereoscopic particle image velocimetry measurements such as the initial region of an annular jet and the transition between flow patterns in an annular jet. The major advantage of the ETF method in the extraction of large scales is that it is computationally less expensive and it requires less measurement time compared to other extraction methods. Therefore, the technique is suitable in the startup phase of an experiment or in a measurement campaign where several experiments are needed such as parametric studies.

Transient Analysis Generator /TAG/ simulates behavior of large class of electrical networks

NASA Technical Reports Server (NTRS)

Thomas, W. J.

1967-01-01

Transient Analysis Generator program simulates both transient and dc steady-state behavior of a large class of electrical networks. It generates a special analysis program for each circuit described in an easily understood and manipulated programming language. A generator or preprocessor and a simulation system make up the TAG system.

Experimental techniques and computational methods toward the estimation of the effective two-phase flow coefficients and multi-scale heterogeneities of soils

NASA Astrophysics Data System (ADS)

Tsakiroglou, C. D.; Aggelopoulos, C. A.; Sygouni, V.

2009-04-01

A hierarchical, network-type, dynamic simulator of the immiscible displacement of water by oil in heterogeneous porous media is developed to simulate the rate-controlled displacement of two fluids at the soil column scale. A cubic network is constructed, where each node is assigned a permeability which is chosen randomly from a distribution function. The intensity of heterogeneities is quantified by the width of the permeability distribution function. The capillary pressure at each node is calculated by combining a generalized Leverett J-function with a Corey type model. Information about the heterogeneity of soils at the pore network scale is obtained by combining mercury intrusion porosimetry (MIP) data with back-scattered scanning electron microscope (BSEM) images [1]. In order to estimate the two-phase flow properties of nodes (relative permeability and capillary pressure functions, permeability distribution function) immiscible and miscible displacement experiments are performed on undisturbed soil columns. The transient responses of measured variables (pressure drop, fluid saturation averaged over five successive segments, solute concentration averaged over three cross-sections) are fitted with models accounting for the preferential flow paths at the micro- (multi-region model) and macro-scale (multi flowpath model) because of multi-scale heterogeneities [2,3]. Simulating the immiscible displacement of water by oil (drainage) in a large netork, at each time step, the fluid saturation and pressure of each node are calculated formulating mass balances at each node, accounting for capillary, viscous and gravity forces, and solving the system of coupled equations. At each iteration of the algorithm, the pressure drop is so selected that the total flow rate of the injected fluid is kept constant. The dynamic large-scale network simulator is used (1) to examine the sensitivity of the transient responses of the axial distribution of fluid saturation and total pressure drop across the network to the permeability distribution function, spatial correlations of permeability, and capillary number, and (2) to estimate the effective (up-scaled) relative permeability functions at the soil column scale. In an attempt to clarify potential effects of the permeability distribution and spatial permeability correlations on the transient responses of the pressure drop across a soil column, signal analysis with wavelets is performed [4] on experimental and simulated results. The transient variation of signal energy and frequency of pressure drop fluctuations at the wavelet domain are correlated with macroscopic properties such as the effective water and oil relative permeabilities of the porous medium, and microscopic properties such as the variation of the permeability distribution of oil-occupied nodes. Toward the solution of the inverse problem, a general procedure is suggested to identify macro-heterogeneities from the fast analysis of pressure drop signals. References 1. Tsakiroglou, C.D. and M.A. Ioannidis, "Dual porosity modeling of the pore structure and transport properties of a contaminated soil", Eur. J. Soil Sci., 59, 744-761 (2008). 2. Aggelopoulos, C.A., and C.D. Tsakiroglou, "Quantifying the Soil Heterogeneity from Solute Dispersion Experiments", Geoderma, 146, 412-424 (2008). 3. Aggelopoulos, C.A., and C.D. Tsakiroglou, "A multi-flow path approach to model immiscible displacement in undisturbed heterogeneous soil columns", J. Contam. Hydrol., in press (2009). 4. Sygouni, V., C.D. Tsakiroglou, and A.C. Payatakes, "Using wavelets to characterize the wettability of porous materials", Phys. Rev. E, 76, 056304 (2007).

Effects of geoduck (Panopea generosa) aquaculture on resident and transient macrofauna communities of Puget Sound, Washington, USA

USGS Publications Warehouse

Mcdonald, P. Sean; Galloway, Aaron W.E.; McPeek, Kathleen C.; VanBlaricom, Glenn R.

2015-01-01

In Washington state, commercial culture of geoducks (Panopea generosa) involves large-scale out-planting of juveniles to intertidal habitats, and installation of PVC tubes and netting to exclude predators and increase early survival. Structures associated with this nascent aquaculture method are examined to determine whether they affect patterns of use by resident and transient macrofauna. Results are summarized from regular surveys of aquaculture operations and reference beaches in 2009 to 2011 at three sites during three phases of culture: (1) pregear (-geoducks, -structure), (2) gear present (+geoducks, +structures), and (3) postgear (+geoducks, -structures). Resident macroinvertebrates (infauna and epifauna) were sampled monthly (in most cases) using coring methods at low tide during all three phases. Differences in community composition between culture plots and reference areas were examined with permutational analysis of variance and homogeneity of multivariate dispersion tests. Scuba and shoreline transect surveys were used to examine habitat use by transient fish and macroinvertebrates. Analysis of similarity and complementary nonmetric multidimensional scaling were used to compare differences between species functional groups and habitat type during different aquaculture phases. Results suggest that resident and transient macrofauna respond differently to structures associated with geoduck aquaculture. No consistent differences in the community of resident macrofauna were observed at culture plots or reference areas at the three sites during any year. Conversely, total abundance of transient fish and macroinvertebrates were more than two times greater at culture plots than reference areas when aquaculture structures were in place. Community composition differed (analysis of similarity) between culture and reference plots during the gear-present phase, but did not persist to the next farming stage (postgear). Habitat complexity associated with shellfish aquaculture may attract some structure-associated transient species observed infrequently on reference beaches, and may displace other species that typically occur in areas lacking epibenthic structure. This study provides a first look at the effects of multiple phases of geoduck farming on macrofauna, and has important implications for the management of a rapidly expanding sector of the aquaculture industry.

Transient flows of the solar wind associated with small-scale solar activity in solar minimum

NASA Astrophysics Data System (ADS)

Slemzin, Vladimir; Veselovsky, Igor; Kuzin, Sergey; Gburek, Szymon; Ulyanov, Artyom; Kirichenko, Alexey; Shugay, Yulia; Goryaev, Farid

The data obtained by the modern high sensitive EUV-XUV telescopes and photometers such as CORONAS-Photon/TESIS and SPHINX, STEREO/EUVI, PROBA2/SWAP, SDO/AIA provide good possibilities for studying small-scale solar activity (SSA), which is supposed to play an important role in heating of the corona and producing transient flows of the solar wind. During the recent unusually weak solar minimum, a large number of SSA events, such as week solar flares, small CMEs and CME-like flows were observed and recorded in the databases of flares (STEREO, SWAP, SPHINX) and CMEs (LASCO, CACTUS). On the other hand, the solar wind data obtained in this period by ACE, Wind, STEREO contain signatures of transient ICME-like structures which have shorter duration (<10h), weaker magnetic field strength (<10 nT) and lower proton temperature than usual ICMEs. To verify the assumption that ICME-like transients may be associated with the SSA events we investigated the number of weak flares of C-class and lower detected by SPHINX in 2009 and STEREO/EUVI in 2010. The flares were classified on temperature and emission measure using the diagnostic means of SPHINX and Hinode/EIS and were confronted with the parameters of the solar wind (velocity, density, ion composition and temperature, magnetic field, pitch angle distribution of the suprathermal electrons). The outflows of plasma associated with the flares were identified by their coronal signatures - CMEs (only in few cases) and dimmings. It was found that the mean parameters of the solar wind projected to the source surface for the times of the studied flares were typical for the ICME-like transients. The results support the suggestion that weak flares can be indicators of sources of transient plasma flows contributing to the slow solar wind at solar minimum, although these flows may be too weak to be considered as separate CMEs and ICMEs. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project n° 284461, www.eheroes.eu).

Quantitative controls on submarine slope failure morphology

USGS Publications Warehouse

Lee, H.J.; Schwab, W.C.; Edwards, B.D.; Kayen, R.E.

1991-01-01

The concept of the steady-state of deformation can be applied to predicting the ultimate form a landslide will take. The steady-state condition, defined by a line in void ratio-effective stress space, exists at large levels of strain and remolding. Conceptually, if sediment initially exists with void ratio-effective stress conditions above the steady-state line, the sediment shear strength will decrease during a transient loading event, such as an earthquake or storm. If the reduced shear strength existing at the steady state is less than the downslope shear stress induced by gravity, then large-scale internal deformation, disintegration, and flow will occur. -from Authors

Predictive modeling of transient storage and nutrient uptake: Implications for stream restoration

USGS Publications Warehouse

O'Connor, Ben L.; Hondzo, Miki; Harvey, Judson W.

2010-01-01

This study examined two key aspects of reactive transport modeling for stream restoration purposes: the accuracy of the nutrient spiraling and transient storage models for quantifying reach-scale nutrient uptake, and the ability to quantify transport parameters using measurements and scaling techniques in order to improve upon traditional conservative tracer fitting methods. Nitrate (NO3–) uptake rates inferred using the nutrient spiraling model underestimated the total NO3– mass loss by 82%, which was attributed to the exclusion of dispersion and transient storage. The transient storage model was more accurate with respect to the NO3– mass loss (±20%) and also demonstrated that uptake in the main channel was more significant than in storage zones. Conservative tracer fitting was unable to produce transport parameter estimates for a riffle-pool transition of the study reach, while forward modeling of solute transport using measured/scaled transport parameters matched conservative tracer breakthrough curves for all reaches. Additionally, solute exchange between the main channel and embayment surface storage zones was quantified using first-order theory. These results demonstrate that it is vital to account for transient storage in quantifying nutrient uptake, and the continued development of measurement/scaling techniques is needed for reactive transport modeling of streams with complex hydraulic and geomorphic conditions.

Machine Learning for Zwicky Transient Facility

NASA Astrophysics Data System (ADS)

Mahabal, Ashish; Zwicky Transient Facility, Catalina Real-Time Transient Survey

2018-01-01

The Zwicky Transient Facility (ZTF) will operate from 2018 to 2020 covering the accessible sky with its large 47 square degree camera. The transient detection rate is expected to be about a million per night. ZTF is thus a perfect LSST prototype. The big difference is that all of the ZTF transients can be followed up by 4- to 8-m class telescopes. Given the large numbers, using human scanners for separating the genuine transients from artifacts is out of question. For that first step as well as for classifying the transients with minimal follow-up requires machine learning. We describe the tools and plans to take on this task using follow-up facilities, and knowledge gained from archival datasets.

The Computing and Data Grid Approach: Infrastructure for Distributed Science Applications

NASA Technical Reports Server (NTRS)

Johnston, William E.

2002-01-01

With the advent of Grids - infrastructure for using and managing widely distributed computing and data resources in the science environment - there is now an opportunity to provide a standard, large-scale, computing, data, instrument, and collaboration environment for science that spans many different projects and provides the required infrastructure and services in a relatively uniform and supportable way. Grid technology has evolved over the past several years to provide the services and infrastructure needed for building 'virtual' systems and organizations. We argue that Grid technology provides an excellent basis for the creation of the integrated environments that can combine the resources needed to support the large- scale science projects located at multiple laboratories and universities. We present some science case studies that indicate that a paradigm shift in the process of science will come about as a result of Grids providing transparent and secure access to advanced and integrated information and technologies infrastructure: powerful computing systems, large-scale data archives, scientific instruments, and collaboration tools. These changes will be in the form of services that can be integrated with the user's work environment, and that enable uniform and highly capable access to these computers, data, and instruments, regardless of the location or exact nature of these resources. These services will integrate transient-use resources like computing systems, scientific instruments, and data caches (e.g., as they are needed to perform a simulation or analyze data from a single experiment); persistent-use resources. such as databases, data catalogues, and archives, and; collaborators, whose involvement will continue for the lifetime of a project or longer. While we largely address large-scale science in this paper, Grids, particularly when combined with Web Services, will address a broad spectrum of science scenarios. both large and small scale.

Simulation of photoreactive transients and of photochemical transformation of organic pollutants in sunlit boreal lakes across 14 degrees of latitude: A photochemical mapping of Sweden.

PubMed

Koehler, Birgit; Barsotti, Francesco; Minella, Marco; Landelius, Tomas; Minero, Claudio; Tranvik, Lars J; Vione, Davide

2018-02-01

Lake water constituents, such as chromophoric dissolved organic matter (CDOM) and nitrate, absorb sunlight which induces an array of photochemical reactions. Although these reactions are a substantial driver of pollutant degradation in lakes they are insufficiently understood, in particular on large scales. Here, we provide for the first time comprehensive photochemical maps covering a large geographic region. Using photochemical kinetics modeling for 1048 lakes across Sweden we simulated the steady-state concentrations of four photoreactive transient species, which are continuously produced and consumed in sunlit lake waters. We then simulated the transient-induced photochemical transformation of organic pollutants, to gain insight into the relevance of the different photoreaction pathways. We found that boreal lakes were often unfavorable environments for photoreactions mediated by hydroxyl radicals (OH) and carbonate radical anions (CO 3 - ), while photoreactions mediated by CDOM triplet states ( 3 CDOM*) and, to a lesser extent, singlet oxygen ( 1 O 2 ) were the most prevalent. These conditions promote the photodegradation of phenols, which are used as plastic, medical drug and herbicide precursors. When CDOM concentrations increase, as is currently commonly the case in boreal areas such as Sweden, 3 CDOM* will also increase, promoting its importance in photochemical pathways even more. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microfilament-Eruption Mechanism for Solar Spicules

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, Ronald L.

2017-01-01

Recent studies indicate that solar coronal jets result from eruption of small-scale filaments, or "minifilaments" (Sterling et al. 2015, Nature, 523, 437; Panesar et al. ApJL, 832L, 7). In many aspects, these coronal jets appear to be small-scale versions of long-recognized large-scale solar eruptions that are often accompanied by eruption of a large-scale filament and that produce solar flares and coronal mass ejections (CMEs). In coronal jets, a jet-base bright point (JBP) that is often observed to accompany the jet and that sits on the magnetic neutral line from which the minifilament erupts, corresponds to the solar flare of larger-scale eruptions that occurs at the neutral line from which the large-scale filament erupts. Large-scale eruptions are relatively uncommon (approximately 1 per day) and occur with relatively large-scale erupting filaments (approximately 10 (sup 5) kilometers long). Coronal jets are more common (approximately 100s per day), but occur from erupting minifilaments of smaller size (approximately 10 (sup 4) kilometers long). It is known that solar spicules are much more frequent (many millions per day) than coronal jets. Just as coronal jets are small-scale versions of large-scale eruptions, here we suggest that solar spicules might in turn be small-scale versions of coronal jets; we postulate that the spicules are produced by eruptions of "microfilaments" of length comparable to the width of observed spicules (approximately 300 kilometers). A plot of the estimated number of the three respective phenomena (flares/CMEs, coronal jets, and spicules) occurring on the Sun at a given time, against the average sizes of erupting filaments, minifilaments, and the putative microfilaments, results in a size distribution that can be fitted with a power-law within the estimated uncertainties. The counterparts of the flares of large-scale eruptions and the JBPs of jets might be weak, pervasive, transient brightenings observed in Hinode/CaII images, and the production of spicules by microfilament eruptions might explain why spicules spin, as do coronal jets. The expected small-scale neutral lines from which the microfilaments would be expected to erupt would be difficult to detect reliably with current instrumentation, but might be apparent with instrumentation of the near future. A full report on this work appears in Sterling and Moore 2016, ApJL, 829, L9.

Control methods for aiding a pilot during STOL engine failure transients

NASA Technical Reports Server (NTRS)

Nelson, E. R.; Debra, D. B.

1976-01-01

Candidate autopilot control laws that control the engine failure transient sink rates by demonstrating the engineering application of modern state variable control theory were defined. The results of approximate modal analysis were compared to those derived from full state analyses provided from computer design solutions. The aircraft was described, and a state variable model of its longitudinal dynamic motion due to engine and control variations was defined. The classical fast and slow modes were assumed to be sufficiently different to define reduced order approximations of the aircraft motion amendable to hand analysis control definition methods. The original state equations of motion were also applied to a large scale state variable control design program, in particular OPTSYS. The resulting control laws were compared with respect to their relative responses, ease of application, and meeting the desired performance objectives.

Agricultural Recharge Practices for Managing Nitrate in Regional Groundwater: Time-Resolution Assessment of Numerical Modeling Approach

NASA Astrophysics Data System (ADS)

Bastani, M.; Harter, T.

2017-12-01

Intentional recharge practices in irrigated landscapes are promising options to control and remediate groundwater quality degradation with respect to nitrate. To better understand the effect of these practices, a fully 3D transient heterogeneous transport model simulation is developed using MODFLOW and MT3D. The model is developed for a long-term study of nitrate improvements in an alluvial groundwater basin in Eastern San Joaquin Valley, CA. Different scenarios of agricultural recharge strategies including crop type change and winter flood flows are investigated. Transient simulations with high spatio-temporal resolutions are performed. We then consider upscaling strategies that would allow us to simplify the modeling process such that it can be applied at a very large basin-scale (1000s of square kilometers) for scenario analysis. We specifically consider upscaling of time-variant boundary conditions (both internal and external) that have significant influence on calculation cost of the model. We compare monthly transient stresses to upscaled annual and further upscaled average steady-state stresses on nitrate transport in groundwater under recharge scenarios.

Transient elevation of cytoplasmic calcium ion concentration at a single cell level precedes morphological changes of epidermal keratinocytes during cornification.

PubMed

Murata, Teruasa; Honda, Tetsuya; Egawa, Gyohei; Yamamoto, Yasuo; Ichijo, Ryo; Toyoshima, Fumiko; Dainichi, Teruki; Kabashima, Kenji

2018-04-26

Epidermal keratinocytes achieve sequential differentiation from basal to granular layers, and undergo a specific programmed cell death, cornification, to form an indispensable barrier of the body. Although elevation of the cytoplasmic calcium ion concentration ([Ca 2+ ] i ) is one of the factors predicted to regulate cornification, the dynamics of [Ca 2+ ] i in epidermal keratinocytes is largely unknown. Here using intravital imaging, we captured the dynamics of [Ca 2+ ] i in mouse skin. [Ca 2+ ] i was elevated in basal cells on the second time scale in three spatiotemporally distinct patterns. The transient elevation of [Ca 2+ ] i also occurred at the most apical granular layer at a single cell level, and lasted for approximately 40 min. The transient elevation of [Ca 2+ ] i at the granular layer was followed by cornification, which was completed within 10 min. This study demonstrates the tightly regulated elevation of [Ca 2+ ] i preceding the cornification of epidermal keratinocytes, providing possible clues to the mechanisms of cornification.

Dynamic Pressure Probes Developed for Supersonic Flow-Field Measurements

NASA Technical Reports Server (NTRS)

Porro, A. Robert

2001-01-01

A series of dynamic flow-field pressure probes were developed for use in large-scale supersonic wind tunnels at the NASA Glenn Research Center. These flow-field probes include pitot and static pressure probes that can capture fast-acting flow-field pressure transients occurring on a millisecond timescale. The pitot and static probes can be used to determine local Mach number time histories during a transient event. The flow-field pressure probe contains four major components: 1) Static pressure aerodynamic tip; 2) Pressure-sensing cartridge assembly; 3) Pitot pressure aerodynamic tip; 4) Mounting stem. This modular design allows for a variety of probe tips to be used for a specific application. Here, the focus is on flow-field pressure measurements in supersonic flows, so we developed a cone-cylinder static pressure tip and a pitot pressure tip. Alternatively, probe tips optimized for subsonic and transonic flows could be used with this design. The pressure-sensing cartridge assembly allows the simultaneous measurement of steady-state and transient pressure which allows continuous calibration of the dynamic pressure transducer.

Experimental study of geysers through a vent pipe connected to flowing sewers.

PubMed

Huang, Biao; Wu, Shiqiang; Zhu, David Z; Schulz, Harry E

2017-04-01

Geysers of air-water mixtures in urban drainage systems is receiving considerable attention due to public safety concerns. However, the geyser formation process and its relation with air release from pressurized pipes are still relatively little known. A large-scale physical model, that consisted of a main tunnel with a diameter of 270 mm and a length of 25 m connecting two reservoirs and a vertical vent pipe, was established to investigate geyser evolution and pressure transients. Experimental results including dynamic pressure data and high speed videos were analysed in order to characterize geysering flow through the vent pipe. Pressure transients were observed during geysering events. Their amplitudes were found to be about three times the driving pressure head and their periods were close to the classic surge tank predictions. The influence of flow rate and vent pipe size were examined: geyser heights and pressure peaks decreased for small flow rate and large diameter vent pipe. It is suggested that geyser heights are related with the pressure head and the density of the air-water mixture.

Startup of electrophoresis in a suspension of colloidal spheres.

PubMed

Chiang, Chia C; Keh, Huan J

2015-12-01

The transient electrophoretic response of a homogeneous suspension of spherical particles to the step application of an electric field is analyzed. The electric double layer encompassing each particle is assumed to be thin but finite, and the effect of dynamic electroosmosis within it is incorporated. The momentum equation for the fluid outside the double layers is solved through the use of a unit cell model. Closed-form formulas for the time-evolving electrophoretic and settling velocities of the particles in the Laplace transform are obtained in terms of the electrokinetic radius, relative mass density, and volume fraction of the particles. The time scale for the development of electrophoresis and sedimentation is significantly smaller for a suspension with a higher particle volume fraction or a smaller particle-to-fluid density ratio, and the electrophoretic mobility at any instant increases with an increase in the electrokinetic particle radius. The transient electrophoretic mobility is a decreasing function of the particle volume fraction if the particle-to-fluid density ratio is relatively small, but it may increase with an increase in the particle volume fraction if this density ratio is relatively large. The particle interaction effect in a suspension on the transient electrophoresis is much weaker than that on the transient sedimentation of the particles. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measurement and Analysis of Multiple Output Transient Propagation in BJT Analog Circuits

NASA Astrophysics Data System (ADS)

Roche, Nicolas J.-H.; Khachatrian, A.; Warner, J. H.; Buchner, S. P.; McMorrow, D.; Clymer, D. A.

2016-08-01

The propagation of Analog Single Event Transients (ASETs) to multiple outputs of Bipolar Junction Transistor (BJTs) Integrated Circuits (ICs) is reported for the first time. The results demonstrate that ASETs can appear at several outputs of a BJT amplifier or comparator as a result of a single ion or single laser pulse strike at a single physical location on the chip of a large-scale integrated BJT analog circuit. This is independent of interconnect cross-talk or charge-sharing effects. Laser experiments, together with SPICE simulations and analysis of the ASET's propagation in the s-domain are used to explain how multiple-output transients (MOTs) are generated and propagate in the device. This study demonstrates that both the charge collection associated with an ASET and the ASET's shape, commonly used to characterize the propagation of SETs in devices and systems, are unable to explain quantitatively how MOTs propagate through an integrated analog circuit. The analysis methodology adopted here involves combining the Fourier transform of the propagating signal and the current-source transfer function in the s-domain. This approach reveals the mechanisms involved in the transient signal propagation from its point of generation to one or more outputs without the signal following a continuous interconnect path.

Visualization of nanocrystal breathing modes at extreme strains

NASA Astrophysics Data System (ADS)

Szilagyi, Erzsi; Wittenberg, Joshua S.; Miller, Timothy A.; Lutker, Katie; Quirin, Florian; Lemke, Henrik; Zhu, Diling; Chollet, Matthieu; Robinson, Joseph; Wen, Haidan; Sokolowski-Tinten, Klaus; Lindenberg, Aaron M.

2015-03-01

Nanoscale dimensions in materials lead to unique electronic and structural properties with applications ranging from site-specific drug delivery to anodes for lithium-ion batteries. These functional properties often involve large-amplitude strains and structural modifications, and thus require an understanding of the dynamics of these processes. Here we use femtosecond X-ray scattering techniques to visualize, in real time and with atomic-scale resolution, light-induced anisotropic strains in nanocrystal spheres and rods. Strains at the percent level are observed in CdS and CdSe samples, associated with a rapid expansion followed by contraction along the nanosphere or nanorod radial direction driven by a transient carrier-induced stress. These morphological changes occur simultaneously with the first steps in the melting transition on hundreds of femtosecond timescales. This work represents the first direct real-time probe of the dynamics of these large-amplitude strains and shape changes in few-nanometre-scale particles.

Distant storms as drivers of environmental change at Pacific atolls.

PubMed

Gardner, Jonathan P A; Garton, David W; Collen, John D; Zwartz, Daniel

2014-01-01

The central Pacific Ocean with its many low lying islands and atolls is under threat from sea level rise and increased storm activity. Here, we illustrate how increasing frequency and severity of large scale storm events associated with global climate change may be particularly profound at the local scale for human populations that rely on lagoon systems for provision of a variety of goods and services. In August 2011 a storm originating in the Southern Ocean caused a large amplitude ocean swell to move northward through the Pacific Ocean. Its arrival at Palmyra Atoll coincided with transient elevated sea surface height and triggered turnover of the lagoon water column. This storm-induced change to the lagoon reflects long distance connectivity with propagated wave energy from the Southern Ocean and illustrates the increasing threats generated by climate change that are faced by human populations on most low-lying Pacific islands and atolls.

Circuit engineering principles for construction of bipolar large-scale integrated circuit storage devices and very large-scale main memory

NASA Astrophysics Data System (ADS)

Neklyudov, A. A.; Savenkov, V. N.; Sergeyez, A. G.

1984-06-01

Memories are improved by increasing speed or the memory volume on a single chip. The most effective means for increasing speeds in bipolar memories are current control circuits with the lowest extraction times for a specific power consumption (1/4 pJ/bit). The control current circuitry involves multistage current switches and circuits accelerating transient processes in storage elements and links. Circuit principles for the design of bipolar memories with maximum speeds for an assigned minimum of circuit topology are analyzed. Two main classes of storage with current control are considered: the ECL type and super-integrated injection type storage with data capacities of N = 1/4 and N 4/16, respectively. The circuits reduce logic voltage differentials and the volumes of lexical and discharge buses and control circuit buses. The limiting speed is determined by the antiinterference requirements of the memory in storage and extraction modes.

Ionospheric chemical releases

NASA Technical Reports Server (NTRS)

Bernhardt, Paul A.; Scales, W. A.

1990-01-01

Ionospheric plasma density irregularities can be produced by chemical releases into the upper atmosphere. F-region plasma modification occurs by: (1) chemically enhancing the electron number density; (2) chemically reducing the electron population; or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) determine the effectiveness of ionospheric chemical releases in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density. Subsequent processes, however, can lead to enhanced transport in chemically modified regions. Ionospheric modifications by chemical releases excites artificial enhancements in airglow intensities by exothermic chemical reactions between the newly created plasma species. Numerical models were developed to describe the creation and evolution of large scale density irregularities and airglow clouds generated by artificial means. Experimental data compares favorably with theses models. It was found that chemical releases produce transient, large amplitude perturbations in electron density which can evolve into fine scale irregularities via nonlinear transport properties.

Distant Storms as Drivers of Environmental Change at Pacific Atolls

PubMed Central

Gardner, Jonathan P. A.; Garton, David W.; Collen, John D.; Zwartz, Daniel

2014-01-01

The central Pacific Ocean with its many low lying islands and atolls is under threat from sea level rise and increased storm activity. Here, we illustrate how increasing frequency and severity of large scale storm events associated with global climate change may be particularly profound at the local scale for human populations that rely on lagoon systems for provision of a variety of goods and services. In August 2011 a storm originating in the Southern Ocean caused a large amplitude ocean swell to move northward through the Pacific Ocean. Its arrival at Palmyra Atoll coincided with transient elevated sea surface height and triggered turnover of the lagoon water column. This storm-induced change to the lagoon reflects long distance connectivity with propagated wave energy from the Southern Ocean and illustrates the increasing threats generated by climate change that are faced by human populations on most low-lying Pacific islands and atolls. PMID:24498232

Shear-banding and superdiffusivity in entangled polymer solutions

NASA Astrophysics Data System (ADS)

Shin, Seunghwan; Dorfman, Kevin D.; Cheng, Xiang

2017-12-01

Using high-resolution confocal rheometry, we study the shear profiles of well-entangled DNA solutions under large-amplitude oscillatory shear in a rectilinear planar shear cell. With increasing Weissenberg number (Wi), we observe successive transitions from normal Newtonian linear shear profiles to wall-slip dominant shear profiles and, finally, to shear-banding profiles at high Wi. To investigate the microscopic origin of the observed shear banding, we study the dynamics of micron-sized tracers embedded in DNA solutions. Surprisingly, tracer particles in the shear frame exhibit transient superdiffusivity and strong dynamic heterogeneity. The probability distribution functions of particle displacements follow a power-law scaling at large displacements, indicating a Lévy-walk-type motion, reminiscent of tracer dynamics in entangled wormlike micelle solutions and sheared colloidal glasses. We further characterize the length and time scales associated with the abnormal dynamics of tracer particles. We hypothesize that the unusual particle dynamics arise from localized shear-induced chain disentanglement.

Acoustic nonreciprocity in a lattice incorporating nonlinearity, asymmetry, and internal scale hierarchy: Experimental study

NASA Astrophysics Data System (ADS)

Bunyan, Jonathan; Moore, Keegan J.; Mojahed, Alireza; Fronk, Matthew D.; Leamy, Michael; Tawfick, Sameh; Vakakis, Alexander F.

2018-05-01

In linear time-invariant systems acoustic reciprocity holds by the Onsager-Casimir principle of microscopic reversibility, and it can be broken only by odd external biases, nonlinearities, or time-dependent properties. Recently it was shown that one-dimensional lattices composed of a finite number of identical nonlinear cells with internal scale hierarchy and asymmetry exhibit nonreciprocity both locally and globally. Considering a single cell composed of a large scale nonlinearly coupled to a small scale, local dynamic nonreciprocity corresponds to vibration energy transfer from the large to the small scale, but absence of energy transfer (and localization) from the small to the large scale. This has been recently proven both theoretically and experimentally. Then, considering the entire lattice, global acoustic nonreciprocity has been recently proven theoretically, corresponding to preferential energy transfer within the lattice under transient excitation applied at one of its boundaries, and absence of similar energy transfer (and localization) when the excitation is applied at its other boundary. This work provides experimental validation of the global acoustic nonreciprocity with a one-dimensional asymmetric lattice composed of three cells, with each cell incorporating nonlinearly coupled large and small scales. Due to the intentional asymmetry of the lattice, low impulsive excitations applied to one of its boundaries result in wave transmission through the lattice, whereas when the same excitations are applied to the other end, they lead in energy localization at the boundary and absence of wave transmission. This global nonreciprocity depends critically on energy (i.e., the intensity of the applied impulses), and reduced-order models recover the nonreciprocal acoustics and clarify the nonlinear mechanism generating nonreciprocity in this system.

Model of the Radio Frequency (RF) Excitation Response from Monopole and Dipole Antennas in a Large Scale Tank

NASA Technical Reports Server (NTRS)

Wilson, Jeffrey D.; Zimmerli, Gregory A.

2012-01-01

Good antenna-mode coupling is needed for determining the amount of propellant in a tank through the method of radio frequency mass gauging (RFMG). The antenna configuration and position in a tank are important factors in coupling the antenna to the natural electromagnetic modes. In this study, different monopole and dipole antenna mounting configurations and positions were modeled and responses simulated in a full-scale tank model with the transient solver of CST Microwave Studio (CST Computer Simulation Technology of America, Inc.). The study was undertaken to qualitatively understand the effect of antenna design and placement within a tank on the resulting radio frequency (RF) tank spectrum.

Numerical simulation of small-scale thermal convection in the atmosphere

NASA Technical Reports Server (NTRS)

Somerville, R. C. J.

1973-01-01

A Boussinesq system is integrated numerically in three dimensions and time in a study of nonhydrostatic convection in the atmosphere. Simulation of cloud convection is achieved by the inclusion of parametrized effects of latent heat and small-scale turbulence. The results are compared with the cell structure observed in Rayleigh-Benard laboratory conversion experiments in air. At a Rayleigh number of 4000, the numerical model adequately simulates the experimentally observed evolution, including some prominent transients of a flow from a randomly perturbed initial conductive state into the final state of steady large-amplitude two-dimensional rolls. At Rayleigh number 9000, the model reproduces the experimentally observed unsteady equilibrium of vertically coherent oscillatory waves superimposed on rolls.

Use of ruthenium dyes for subnanosecond detector fidelity testing in real time transient absorption

NASA Astrophysics Data System (ADS)

Byrdin, Martin; Thiagarajan, Viruthachalam; Villette, Sandrine; Espagne, Agathe; Brettel, Klaus

2009-04-01

Transient absorption spectroscopy is a powerful tool for the study of photoreactions on time scales from femtoseconds to seconds. Typically, reactions slower than ˜1 ns are recorded by the "classical" technique; the reaction is triggered by an excitation flash, and absorption changes accompanying the reaction are recorded in real time using a continuous monitoring light beam and a detection system with sufficiently fast response. The pico- and femtosecond region can be accessed by the more recent "pump-probe" technique, which circumvents the difficulties of real time detection on a subnanosecond time scale. This is paid for by accumulation of an excessively large number of shots to sample the reaction kinetics. Hence, it is of interest to extend the classical real time technique as far as possible to the subnanosecond range. In order to identify and minimize detection artifacts common on a subnanosecond scale, like overshoot, ringing, and signal reflections, rigorous testing is required of how the detection system responds to fast changes of the monitoring light intensity. Here, we introduce a novel method to create standard signals for detector fidelity testing on a time scale from a few picoseconds to tens of nanoseconds. The signals result from polarized measurements of absorption changes upon excitation of ruthenium complexes {[Ru(bpy)3]2+ and a less symmetric derivative} by a short laser flash. Two types of signals can be created depending on the polarization of the monitoring light with respect to that of the excitation flash: a fast steplike bleaching at magic angle and a monoexponentially decaying bleaching for parallel polarizations. The lifetime of the decay can be easily varied via temperature and viscosity of the solvent. The method is applied to test the performance of a newly developed real time transient absorption setup with 300 ps time resolution and high sensitivity.

Asymmetric Impact of Tropical SST Anomalies on Atmospheric Internal Variability over the North Pacific.

NASA Astrophysics Data System (ADS)

Chen, Wilbur Y.; van den Dool, Huug M.

1997-03-01

A substantial asymmetric impact of tropical Pacific SST anomalies on the internal variability of the extratropical atmosphere is found. A variety of diagnoses is performed to help reveal the dynamical processes leading to the large impact. Thirty-five years of geopotential heights and 29 years of wind fields analyzed operationally at the National Centers for Environmental Prediction (NCEP), formerly the National Meteorological Center, and three sets of 10-yr-long perpetual January integrations run with a low-resolution NCEP global spectral model are investigated in detail for the impact of the SST anomalies on the blocking flows over the North Pacific. The impact on large-scale deep trough flows is also examined.Both the blocking and deep trough flows develop twice as much over the North Pacific during La Niña as during El Niño winters. Consequently, the internal dynamics associated low-frequency variability (LFV), with timescales between 7 and 61 days examined in this study, display distinct characteristics: much larger magnitude for the La Niña than the El Niño winters over the eastern North Pacific, where the LFV is highest in general.The diagnosis of the localized Eliassen-Palm fluxes and their divergence reveals that the high-frequency transient eddies (1-7 days) at high latitudes are effective in forming and maintaining the large-scale blocking flows, while the midlatitude transients are less effective. The mean deformation field over the North Pacific is much more diffluent for the La Niña than the El Niño winters, resulting in more blocking flows being developed and maintained during La Niña by the high-frequency transients over the central North Pacific.In addition to the above dynamical process operating on the high-frequency end of the spectrum, the local barotropic energy conversion between the LFV components and the time-mean flows is also operating and playing a crucial role. The kinetic energy conversion represented by the scalar product between the E vector of the low-frequency components and the deformation D vector of the time-mean flow reveals that, on average, the low-frequency components extract energy from the time-mean flow during La Niña winters while they lose energy to the time-mean flow during El Niño winters. This local barotropic energy conversion on the low-frequency end of the spectrum, together with the forcing of the high-frequency transients on blocking flows on the high-frequency end, explain why there is a large difference in the magnitude of low-frequency variability between the La Niña and the El Niño winters.

The seasonal use of small-scale space by benthic species in a transiently hypoxic area

NASA Astrophysics Data System (ADS)

Doya, Carolina; Aguzzi, Jacopo; Chatzievangelou, Damianos; Costa, Corrado; Company, Joan Baptista; Tunnicliffe, Verena

2016-02-01

The use of small-scale space by benthos and its variation over the seasons in transiently hypoxic zones is poorly known. In this study, we examined the reciprocal spatial dispersion of the squat lobster (Munida quadrispina) and the slender sole (Lyopsetta exilis) according to oxygen concentrations at a VENUS platform of Ocean Networks Canada (ONC). This platform is located in a seasonally hypoxic zone at 96 m depth in the fjord of Saanich Inlet (British Columbia, Canada). We counted and located small as well as large squat lobsters and slender soles in digital still images during 1 year (2012-2013) also concomitantly obtained oxygen data. Images were subdivided in a squared grid to obtain relative density maps as a proxy for surface occupation and spatial autocorrelation. Pearson's chi-squared tests at a yearly scale, along with Dixon's spatial segregation index (S) for each possible pair among the studied groups, showed a significant absence of overlap. The same analyses by month and cross-correlation between oxygen and S showed that while the dispersion patterns of the large squat lobsters seemed to be driven mainly by the morphology of the seafloor, an effect of hypoxia was found in the small squat lobsters and the slender soles levels of aggregation. Small squat lobster sought seabed protrusions, such as sponges, to reach more oxygenated water. The slender sole's space occupation decreased significantly, being forced to retreat when the squat lobsters' abundance peaked as a result of what appeared to be a seasonal reproduction event in early summer. Our results contribute to the understanding of the ways in which oxygen levels modulate substrate use by benthic species in the framework of a global expansion of hypoxia in coastal and ocean areas.

A transient FETI methodology for large-scale parallel implicit computations in structural mechanics

NASA Technical Reports Server (NTRS)

Farhat, Charbel; Crivelli, Luis; Roux, Francois-Xavier

1992-01-01

Explicit codes are often used to simulate the nonlinear dynamics of large-scale structural systems, even for low frequency response, because the storage and CPU requirements entailed by the repeated factorizations traditionally found in implicit codes rapidly overwhelm the available computing resources. With the advent of parallel processing, this trend is accelerating because explicit schemes are also easier to parallelize than implicit ones. However, the time step restriction imposed by the Courant stability condition on all explicit schemes cannot yet -- and perhaps will never -- be offset by the speed of parallel hardware. Therefore, it is essential to develop efficient and robust alternatives to direct methods that are also amenable to massively parallel processing because implicit codes using unconditionally stable time-integration algorithms are computationally more efficient when simulating low-frequency dynamics. Here we present a domain decomposition method for implicit schemes that requires significantly less storage than factorization algorithms, that is several times faster than other popular direct and iterative methods, that can be easily implemented on both shared and local memory parallel processors, and that is both computationally and communication-wise efficient. The proposed transient domain decomposition method is an extension of the method of Finite Element Tearing and Interconnecting (FETI) developed by Farhat and Roux for the solution of static problems. Serial and parallel performance results on the CRAY Y-MP/8 and the iPSC-860/128 systems are reported and analyzed for realistic structural dynamics problems. These results establish the superiority of the FETI method over both the serial/parallel conjugate gradient algorithm with diagonal scaling and the serial/parallel direct method, and contrast the computational power of the iPSC-860/128 parallel processor with that of the CRAY Y-MP/8 system.

RD2-MolPack-Chim3, a packaging cell line for stable production of lentiviral vectors for anti-HIV gene therapy.

PubMed

Stornaiuolo, Anna; Piovani, Bianca Maria; Bossi, Sergio; Zucchelli, Eleonora; Corna, Stefano; Salvatori, Francesca; Mavilio, Fulvio; Bordignon, Claudio; Rizzardi, Gian Paolo; Bovolenta, Chiara

2013-08-01

Over the last two decades, several attempts to generate packaging cells for lentiviral vectors (LV) have been made. Despite different technologies, no packaging clone is currently employed in clinical trials. We developed a new strategy for LV stable production based on the HEK-293T progenitor cells; the sequential insertion of the viral genes by integrating vectors; the constitutive expression of the viral components; and the RD114-TR envelope pseudotyping. We generated the intermediate clone PK-7 expressing constitutively gag/pol and rev genes and, by adding tat and rd114-tr genes, the stable packaging cell line RD2-MolPack, which can produce LV carrying any transfer vector (TV). Finally, we obtained the RD2-MolPack-Chim3 producer clone by transducing RD2-MolPack cells with the TV expressing the anti-HIV transgene Chim3. Remarkably, RD114-TR pseudovirions have much higher potency when produced by stable compared with transient technology. Most importantly, comparable transduction efficiency in hematopoietic stem cells (HSC) is obtained with 2-logs less physical particles respect to VSV-G pseudovirions produced by transient transfection. Altogether, RD2-MolPack technology should be considered a valid option for large-scale production of LV to be used in gene therapy protocols employing HSC, resulting in the possibility of downsizing the manufacturing scale by about 10-fold in respect to transient technology.

Catalytic ignition model in a monolithic reactor with in-depth reaction

NASA Technical Reports Server (NTRS)

Tien, Ta-Ching; Tien, James S.

1990-01-01

Two transient models have been developed to study the catalytic ignition in a monolithic catalytic reactor. The special feature in these models is the inclusion of thermal and species structures in the porous catalytic layer. There are many time scales involved in the catalytic ignition problem, and these two models are developed with different time scales. In the full transient model, the equations are non-dimensionalized by the shortest time scale (mass diffusion across the catalytic layer). It is therefore accurate but is computationally costly. In the energy-integral model, only the slowest process (solid heat-up) is taken as nonsteady. It is approximate but computationally efficient. In the computations performed, the catalyst is platinum and the reactants are rich mixtures of hydrogen and oxygen. One-step global chemical reaction rates are used for both gas-phase homogeneous reaction and catalytic heterogeneous reaction. The computed results reveal the transient ignition processes in detail, including the structure variation with time in the reactive catalytic layer. An ignition map using reactor length and catalyst loading is constructed. The comparison of computed results between the two transient models verifies the applicability of the energy-integral model when the time is greater than the second largest time scale of the system. It also suggests that a proper combined use of the two models can catch all the transient phenomena while minimizing the computational cost.

Progress in extrapolating divertor heat fluxes towards large fusion devices

NASA Astrophysics Data System (ADS)

Sieglin, B.; Faitsch, M.; Eich, T.; Herrmann, A.; Suttrop, W.; Collaborators, JET; the MST1 Team; the ASDEX Upgrade Team

2017-12-01

Heat load to the plasma facing components is one of the major challenges for the development and design of large fusion devices such as ITER. Nowadays fusion experiments can operate with heat load mitigation techniques, e.g. sweeping, impurity seeding, but do not generally require it. For large fusion devices however, heat load mitigation will be essential. This paper presents the current progress of the extrapolation of steady state and transient heat loads towards large fusion devices. For transient heat loads, so-called edge localized modes are considered a serious issue for the lifetime of divertor components. In this paper, the ITER operation at half field (2.65 T) and half current (7.5 MA) will be discussed considering the current material limit for the divertor peak energy fluence of 0.5 {MJ}/{{{m}}}2. Recent studies were successful in describing the observed energy fluence in the JET, MAST and ASDEX Upgrade using the pedestal pressure prior to the ELM crash. Extrapolating this towards ITER results in a more benign heat load compared to previous scalings. In the presence of magnetic perturbation, the axisymmetry is broken and a 2D heat flux pattern is induced on the divertor target, leading to local increase of the heat flux which is a concern for ITER. It is shown that for a moderate divertor broadening S/{λ }{{q}}> 0.5 the toroidal peaking of the heat flux disappears.

Solving the puzzle of discrepant quasar variability on monthly time-scales implied by SDSS and CRTS data sets

NASA Astrophysics Data System (ADS)

Suberlak, Krzysztof; Ivezić, Željko; MacLeod, Chelsea L.; Graham, Matthew; Sesar, Branimir

2017-12-01

We present an improved photometric error analysis for the 7 100 CRTS (Catalina Real-Time Transient Survey) optical light curves for quasars from the SDSS (Sloan Digital Sky Survey) Stripe 82 catalogue. The SDSS imaging survey has provided a time-resolved photometric data set, which greatly improved our understanding of the quasar optical continuum variability: Data for monthly and longer time-scales are consistent with a damped random walk (DRW). Recently, newer data obtained by CRTS provided puzzling evidence for enhanced variability, compared to SDSS results, on monthly time-scales. Quantitatively, SDSS results predict about 0.06 mag root-mean-square (rms) variability for monthly time-scales, while CRTS data show about a factor of 2 larger rms, for spectroscopically confirmed SDSS quasars. Our analysis has successfully resolved this discrepancy as due to slightly underestimated photometric uncertainties from the CRTS image processing pipelines. As a result, the correction for observational noise is too small and the implied quasar variability is too large. The CRTS photometric error correction factors, derived from detailed analysis of non-variable SDSS standard stars that were re-observed by CRTS, are about 20-30 per cent, and result in reconciling quasar variability behaviour implied by the CRTS data with earlier SDSS results. An additional analysis based on independent light curve data for the same objects obtained by the Palomar Transient Factory provides further support for this conclusion. In summary, the quasar variability constraints on weekly and monthly time-scales from SDSS, CRTS and PTF surveys are mutually compatible, as well as consistent with DRW model.

Shock-induced thermal wave propagation and response analysis of a viscoelastic thin plate under transient heating loads

NASA Astrophysics Data System (ADS)

Li, Chenlin; Guo, Huili; Tian, Xiaogeng

2018-04-01

This paper is devoted to the thermal shock analysis for viscoelastic materials under transient heating loads. The governing coupled equations with time-delay parameter and nonlocal scale parameter are derived based on the generalized thermo-viscoelasticity theory. The problem of a thin plate composed of viscoelastic material, subjected to a sudden temperature rise at the boundary plane, is solved by employing Laplace transformation techniques. The transient responses, i.e. temperature, displacement, stresses, heat flux as well as strain, are obtained and discussed. The effects of time-delay and nonlocal scale parameter on the transient responses are analyzed and discussed. It can be observed that: the propagation of thermal wave is dynamically smoothed and changed with the variation of time-delay; while the displacement, strain, and stress can be rapidly reduced by nonlocal scale parameter, which can be viewed as an important indicator for predicting the stiffness softening behavior for viscoelastic materials.

The plume head-continental lithosphere interaction using a tectonically realistic formulation for the lithosphere

NASA Astrophysics Data System (ADS)

Burov, E.; Guillou-Frottier, L.

2005-05-01

Current debates on the existence of mantle plumes largely originate from interpretations of supposed signatures of plume-induced surface topography that are compared with predictions of geodynamic models of plume-lithosphere interactions. These models often inaccurately predict surface evolution: in general, they assume a fixed upper surface and consider the lithosphere as a single viscous layer. In nature, the surface evolution is affected by the elastic-brittle-ductile deformation, by a free upper surface and by the layered structure of the lithosphere. We make a step towards reconciling mantle- and tectonic-scale studies by introducing a tectonically realistic continental plate model in large-scale plume-lithosphere interaction. This model includes (i) a natural free surface boundary condition, (ii) an explicit elastic-viscous(ductile)-plastic(brittle) rheology and (iii) a stratified structure of continental lithosphere. The numerical experiments demonstrate a number of important differences from predictions of conventional models. In particular, this relates to plate bending, mechanical decoupling of crustal and mantle layers and tension-compression instabilities, which produce transient topographic signatures such as uplift and subsidence at large (>500 km) and small scale (300-400, 200-300 and 50-100 km). The mantle plumes do not necessarily produce detectable large-scale topographic highs but often generate only alternating small-scale surface features that could otherwise be attributed to regional tectonics. A single large-wavelength deformation, predicted by conventional models, develops only for a very cold and thick lithosphere. Distinct topographic wavelengths or temporarily spaced events observed in the East African rift system, as well as over French Massif Central, can be explained by a single plume impinging at the base of the continental lithosphere, without evoking complex asthenospheric upwelling.

Insights on surface-water/groundwater exchange in the upper Floridan aquifer, north-central Florida (USA), from streamflow data and numerical modeling

NASA Astrophysics Data System (ADS)

Sutton, James E.; Screaton, Elizabeth J.; Martin, Jonathan B.

2015-03-01

Surface-water/groundwater exchange impacts water quality and budgets. In karst aquifers, these exchanges also play an important role in dissolution. Five years of river discharge data were analyzed and a transient groundwater flow model was developed to evaluate large-scale temporal and spatial variations of exchange between an 80-km stretch of the Suwannee River in north-central Florida (USA) and the karstic upper Floridan aquifer. The one-layer transient groundwater flow model was calibrated using groundwater levels from 59 monitoring wells, and fluxes were compared to the exchange calculated from discharge data. Both the numerical modeling and the discharge analysis suggest that the Suwannee River loses water under both low- and high-stage conditions. River losses appear greatest at the inside of a large meander, and the former river water may continue across the meander within the aquifer rather than return to the river. In addition, the numerical model calibration reveals that aquifer transmissivity is elevated within this large meander, which is consistent with enhanced dissolution due to river losses. The results show the importance of temporal and spatial variations in head gradients to exchange between streams and karst aquifers and dissolution of the aquifers.

An analytical study on nested flow systems in a Tóthian basin with a periodically changing water table

NASA Astrophysics Data System (ADS)

Zhao, Ke-Yu; Jiang, Xiao-Wei; Wang, Xu-Sheng; Wan, Li; Wang, Jun-Zhi; Wang, Heng; Li, Hailong

2018-01-01

Classical understanding on basin-scale groundwater flow patterns is based on Tóth's findings of a single flow system in a unit basin (Tóth, 1962) and nested flow systems in a complex basin (Tóth, 1963), both of which were based on steady state models. Vandenberg (1980) extended Tóth (1962) by deriving a transient solution under a periodically changing water table in a unit basin and examined the flow field distortion under different dimensionless response time, τ∗. Following Vandenberg's (1980) approach, we extended Tóth (1963) by deriving the transient solution under a periodically changing water table in a complex basin and examined the transient behavior of nested flow systems. Due to the effect of specific storage, the flow field is asymmetric with respect to the midline, and the trajectory of internal stagnation points constitutes a non-enclosed loop, whose width decreases when τ∗ decreases. The distribution of the relative magnitude of hydraulic head fluctuation, Δh∗ , is dependent on the horizontal distance away from a divide and the depth below the land surface. In the shallow part, Δh∗ decreases from 1 at the divide to 0 at its neighboring valley under all τ∗, while in the deep part, Δh∗ reaches a threshold, whose value decreases when τ∗ increases. The zones with flowing wells are also found to change periodically. As water table falls, there is a general trend of shrinkage in the area of zones with flowing wells, which has a lag to the declining water table under a large τ∗. Although fluxes have not been assigned in our model, the recharge/discharge flux across the top boundary can be obtained. This study is critical to understand a series of periodically changing hydrogeological phenomena in large-scale basins.

New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR.

PubMed

Carbone, D; van der Horst, A J; Wijers, R A M J; Swinbank, J D; Rowlinson, A; Broderick, J W; Cendes, Y N; Stewart, A J; Bell, M E; Breton, R P; Corbel, S; Eislöffel, J; Fender, R P; Grießmeier, J-M; Hessels, J W T; Jonker, P; Kramer, M; Law, C J; Miller-Jones, J C A; Pietka, M; Scheers, L H A; Stappers, B W; van Leeuwen, J; Wijnands, R; Wise, M; Zarka, P

2016-07-01

We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg 2 . We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 × 10 -3  deg -2 for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates.

Production of recombinant antigens and antibodies in Nicotiana benthamiana using 'magnifection' technology: GMP-compliant facilities for small- and large-scale manufacturing.

PubMed

Klimyuk, Victor; Pogue, Gregory; Herz, Stefan; Butler, John; Haydon, Hugh

2014-01-01

This review describes the adaptation of the plant virus-based transient expression system, magnICON(®) for the at-scale manufacturing of pharmaceutical proteins. The system utilizes so-called "deconstructed" viral vectors that rely on Agrobacterium-mediated systemic delivery into the plant cells for recombinant protein production. The system is also suitable for production of hetero-oligomeric proteins like immunoglobulins. By taking advantage of well established R&D tools for optimizing the expression of protein of interest using this system, product concepts can reach the manufacturing stage in highly competitive time periods. At the manufacturing stage, the system offers many remarkable features including rapid production cycles, high product yield, virtually unlimited scale-up potential, and flexibility for different manufacturing schemes. The magnICON system has been successfully adaptated to very different logistical manufacturing formats: (1) speedy production of multiple small batches of individualized pharmaceuticals proteins (e.g. antigens comprising individualized vaccines to treat NonHodgkin's Lymphoma patients) and (2) large-scale production of other pharmaceutical proteins such as therapeutic antibodies. General descriptions of the prototype GMP-compliant manufacturing processes and facilities for the product formats that are in preclinical and clinical testing are provided.

Scaling laws for perturbations in the ocean-atmosphere system following large CO2 emissions

NASA Astrophysics Data System (ADS)

Towles, N.; Olson, P.; Gnanadesikan, A.

2015-07-01

Scaling relationships are found for perturbations to atmosphere and ocean variables from large transient CO2 emissions. Using the Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir (LOSCAR) model (Zeebe et al., 2009; Zeebe, 2012b), we calculate perturbations to atmosphere temperature, total carbon, ocean temperature, total ocean carbon, pH, alkalinity, marine-sediment carbon, and carbon-13 isotope anomalies in the ocean and atmosphere resulting from idealized CO2 emission events. The peak perturbations in the atmosphere and ocean variables are then fit to power law functions of the form of γ DαEβ, where D is the event duration, E is its total carbon emission, and γ is a coefficient. Good power law fits are obtained for most system variables for E up to 50 000 PgC and D up to 100 kyr. Although all of the peak perturbations increase with emission rate E/D, we find no evidence of emission-rate-only scaling, α + β = 0. Instead, our scaling yields α + β ≃ 1 for total ocean and atmosphere carbon and 0 < α + β < 1 for most of the other system variables.

Extreme value statistics and finite-size scaling at the ecological extinction/laminar-turbulence transition

NASA Astrophysics Data System (ADS)

Shih, Hong-Yan; Goldenfeld, Nigel

Experiments on transitional turbulence in pipe flow seem to show that turbulence is a transient metastable state since the measured mean lifetime of turbulence puffs does not diverge asymptotically at a critical Reynolds number. Yet measurements reveal that the lifetime scales with Reynolds number in a super-exponential way reminiscent of extreme value statistics, and simulations and experiments in Couette and channel flow exhibit directed percolation type scaling phenomena near a well-defined transition. This universality class arises from the interplay between small-scale turbulence and a large-scale collective zonal flow, which exhibit predator-prey behavior. Why is asymptotically divergent behavior not observed? Using directed percolation and a stochastic individual level model of predator-prey dynamics related to transitional turbulence, we investigate the relation between extreme value statistics and power law critical behavior, and show that the paradox is resolved by carefully defining what is measured in the experiments. We theoretically derive the super-exponential scaling law, and using finite-size scaling, show how the same data can give both super-exponential behavior and power-law critical scaling.

Large-scale protein-protein interaction analysis in Arabidopsis mesophyll protoplasts by split firefly luciferase complementation.

PubMed

Li, Jian-Feng; Bush, Jenifer; Xiong, Yan; Li, Lei; McCormack, Matthew

2011-01-01

Protein-protein interactions (PPIs) constitute the regulatory network that coordinates diverse cellular functions. There are growing needs in plant research for creating protein interaction maps behind complex cellular processes and at a systems biology level. However, only a few approaches have been successfully used for large-scale surveys of PPIs in plants, each having advantages and disadvantages. Here we present split firefly luciferase complementation (SFLC) as a highly sensitive and noninvasive technique for in planta PPI investigation. In this assay, the separate halves of a firefly luciferase can come into close proximity and transiently restore its catalytic activity only when their fusion partners, namely the two proteins of interest, interact with each other. This assay was conferred with quantitativeness and high throughput potential when the Arabidopsis mesophyll protoplast system and a microplate luminometer were employed for protein expression and luciferase measurement, respectively. Using the SFLC assay, we could monitor the dynamics of rapamycin-induced and ascomycin-disrupted interaction between Arabidopsis FRB and human FKBP proteins in a near real-time manner. As a proof of concept for large-scale PPI survey, we further applied the SFLC assay to testing 132 binary PPIs among 8 auxin response factors (ARFs) and 12 Aux/IAA proteins from Arabidopsis. Our results demonstrated that the SFLC assay is ideal for in vivo quantitative PPI analysis in plant cells and is particularly powerful for large-scale binary PPI screens.

Ant groups optimally amplify the effect of transiently informed individuals

NASA Astrophysics Data System (ADS)

Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Ghosh, Abhijit; Gov, Nir; Feinerman, Ofer

2015-07-01

To cooperatively transport a large load, it is important that carriers conform in their efforts and align their forces. A downside of behavioural conformism is that it may decrease the group's responsiveness to external information. Combining experiment and theory, we show how ants optimize collective transport. On the single-ant scale, optimization stems from decision rules that balance individuality and compliance. Macroscopically, these rules poise the system at the transition between random walk and ballistic motion where the collective response to the steering of a single informed ant is maximized. We relate this peak in response to the divergence of susceptibility at a phase transition. Our theoretical models predict that the ant-load system can be transitioned through the critical point of this mesoscopic system by varying its size; we present experiments supporting these predictions. Our findings show that efficient group-level processes can arise from transient amplification of individual-based knowledge.

Transient thermal analysis for radioactive liquid mixing operations in a large-scaled tank

DOE PAGES

Lee, S. Y.; Smith, III, F. G.

2014-07-25

A transient heat balance model was developed to assess the impact of a Submersible Mixer Pump (SMP) on radioactive liquid temperature during the process of waste mixing and removal for the high-level radioactive materials stored in Savannah River Site (SRS) tanks. The model results will be mainly used to determine the SMP design impacts on the waste tank temperature during operations and to develop a specification for a new SMP design to replace existing longshaft mixer pumps used during waste removal. The present model was benchmarked against the test data obtained by the tank measurement to examine the quantitative thermalmore » response of the tank and to establish the reference conditions of the operating variables under no SMP operation. The results showed that the model predictions agreed with the test data of the waste temperatures within about 10%.« less

Dynamically induced cascading failures in power grids.

PubMed

Schäfer, Benjamin; Witthaut, Dirk; Timme, Marc; Latora, Vito

2018-05-17

Reliable functioning of infrastructure networks is essential for our modern society. Cascading failures are the cause of most large-scale network outages. Although cascading failures often exhibit dynamical transients, the modeling of cascades has so far mainly focused on the analysis of sequences of steady states. In this article, we focus on electrical transmission networks and introduce a framework that takes into account both the event-based nature of cascades and the essentials of the network dynamics. We find that transients of the order of seconds in the flows of a power grid play a crucial role in the emergence of collective behaviors. We finally propose a forecasting method to identify critical lines and components in advance or during operation. Overall, our work highlights the relevance of dynamically induced failures on the synchronization dynamics of national power grids of different European countries and provides methods to predict and model cascading failures.

Inverting dynamic force microscopy: From signals to time-resolved interaction forces

PubMed Central

Stark, Martin; Stark, Robert W.; Heckl, Wolfgang M.; Guckenberger, Reinhard

2002-01-01

Transient forces between nanoscale objects on surfaces govern friction, viscous flow, and plastic deformation, occur during manipulation of matter, or mediate the local wetting behavior of thin films. To resolve transient forces on the (sub) microsecond time and nanometer length scale, dynamic atomic force microscopy (AFM) offers largely unexploited potential. Full spectral analysis of the AFM signal completes dynamic AFM. Inverting the signal formation process, we measure the time course of the force effective at the sensing tip. This approach yields rich insight into processes at the tip and dispenses with a priori assumptions about the interaction, as it relies solely on measured data. Force measurements on silicon under ambient conditions demonstrate the distinct signature of the interaction and reveal that peak forces exceeding 200 nN are applied to the sample in a typical imaging situation. These forces are 2 orders of magnitude higher than those in covalent bonds. PMID:12070341

Ant groups optimally amplify the effect of transiently informed individuals

PubMed Central

Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Ghosh, Abhijit; Gov, Nir; Feinerman, Ofer

2015-01-01

To cooperatively transport a large load, it is important that carriers conform in their efforts and align their forces. A downside of behavioural conformism is that it may decrease the group's responsiveness to external information. Combining experiment and theory, we show how ants optimize collective transport. On the single-ant scale, optimization stems from decision rules that balance individuality and compliance. Macroscopically, these rules poise the system at the transition between random walk and ballistic motion where the collective response to the steering of a single informed ant is maximized. We relate this peak in response to the divergence of susceptibility at a phase transition. Our theoretical models predict that the ant-load system can be transitioned through the critical point of this mesoscopic system by varying its size; we present experiments supporting these predictions. Our findings show that efficient group-level processes can arise from transient amplification of individual-based knowledge. PMID:26218613

Response to a small external force and fluctuations of a passive particle in a one-dimensional diffusive environment

NASA Astrophysics Data System (ADS)

Huveneers, François

2018-04-01

We investigate the long-time behavior of a passive particle evolving in a one-dimensional diffusive random environment, with diffusion constant D . We consider two cases: (a) The particle is pulled forward by a small external constant force and (b) there is no systematic bias. Theoretical arguments and numerical simulations provide evidence that the particle is eventually trapped by the environment. This is diagnosed in two ways: The asymptotic speed of the particle scales quadratically with the external force as it goes to zero, and the fluctuations scale diffusively in the unbiased environment, up to possible logarithmic corrections in both cases. Moreover, in the large D limit (homogenized regime), we find an important transient region giving rise to other, finite-size scalings, and we describe the crossover to the true asymptotic behavior.

High-Resolution Numerical Simulation and Analysis of Mach Reflection Structures in Detonation Waves in Low-Pressure H 2 –O 2 –Ar Mixtures: A Summary of Results Obtained with the Adaptive Mesh Refinement Framework AMROC

DOE PAGES

Deiterding, Ralf

2011-01-01

Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described techniquesmore » in practice. In particular, computations of regular cellular structures in two and three space dimensions and their development under transient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns are classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is constructed.« less

Globalized Newton-Krylov-Schwarz Algorithms and Software for Parallel Implicit CFD

NASA Technical Reports Server (NTRS)

Gropp, W. D.; Keyes, D. E.; McInnes, L. C.; Tidriri, M. D.

1998-01-01

Implicit solution methods are important in applications modeled by PDEs with disparate temporal and spatial scales. Because such applications require high resolution with reasonable turnaround, "routine" parallelization is essential. The pseudo-transient matrix-free Newton-Krylov-Schwarz (Psi-NKS) algorithmic framework is presented as an answer. We show that, for the classical problem of three-dimensional transonic Euler flow about an M6 wing, Psi-NKS can simultaneously deliver: globalized, asymptotically rapid convergence through adaptive pseudo- transient continuation and Newton's method-, reasonable parallelizability for an implicit method through deferred synchronization and favorable communication-to-computation scaling in the Krylov linear solver; and high per- processor performance through attention to distributed memory and cache locality, especially through the Schwarz preconditioner. Two discouraging features of Psi-NKS methods are their sensitivity to the coding of the underlying PDE discretization and the large number of parameters that must be selected to govern convergence. We therefore distill several recommendations from our experience and from our reading of the literature on various algorithmic components of Psi-NKS, and we describe a freely available, MPI-based portable parallel software implementation of the solver employed here.

Role of transients in the sustainability of solar coronal plumes

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

Raouafi, N.-E.; Stenborg, G., E-mail: NourEddine.Raouafi@jhuapl.edu

2014-06-01

We report on the role of small-scale, transient magnetic activity in the formation and evolution of solar coronal plumes. Three plumes within equatorial coronal holes are analyzed over the span of several days based on the Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly 171 Å and 193 Å images and SDO/Helioseismic and Magnetic Imager line-of-sight magnetograms. The focus is on the role of transient structures at the footpoints in sustaining coronal plumes for relatively long periods of time (i.e., several days). The appearance of plumes is a gradual and lengthy process. In some cases, the initial stages of plume formation aremore » marked by the appearance of pillar-like structures whose footpoints are the sources of transient brightenings. In addition to nominal jets occurring prior to and during the development of plumes, the data show that a large number of small jets (i.e., {sup j}etlets{sup )} and plume transient bright points (PTBPs) occur on timescales of tens of seconds to a few minutes. These features are the result of quasi-random cancellations of fragmented and diffuse minority magnetic polarity with the dominant unipolar magnetic field concentration over an extended period of time. They unambiguously reflect a highly dynamical evolution at the footpoints and are seemingly the main energy source for plumes. This suggests a tendency for plumes to be dependent on the occurrence of transients (i.e., jetlets, and PTBPs) resulting from low-rate magnetic reconnection. The decay phase of plumes is characterized by gradual fainting and multiple rejuvenations as a result of the dispersal of the unipolar magnetic concentration and its precipitation into multiple magnetic centers.« less

Solar Wind Plasma Flows and Space Weather Aspects Recent Solar Cycle

NASA Astrophysics Data System (ADS)

Kaushik, Sonia; Kaushik, Subhash Chandra

2016-07-01

Solar transients are responsible for initiating short - term and long - term variations in earth's magnetosphere. These variations are termed as geomagnetic disturbances, and driven by the interaction of solar wind features with the geo-magnetosphere. The strength of this modulation process depends upon the magnitude and orientation of the Interplanetary Magnetic Field and solar wind parameters. These interplanetary transients are large scale structures containing plasma and magnetic field expelled from the transient active regions of solar atmosphere. As they come to interplanetary medium the interplanetary magnetic field drape around them. This field line draping was thought as possible cause of the characteristic eastward deflection and giving rise to geomagnetic activities as well as a prime factor in producing the modulation effects in the near Earth environment. The Solar cycle 23 has exhibited the unique extended minima and peculiar effects in the geomagnetosphere. Selecting such transients, occurred during this interval, an attempt has been made to determine quantitative relationships of these transients with solar/ interplanetary and Geophysical Parameters. In this work we used hourly values of IMF data obtained from the NSSD Center. The analysis mainly based on looking into the effects of these transients on earth's magnetic field. The high-resolution data IMF Bz and solar wind data obtained from WDC-A, through its omniweb, available during the selected period. Dst and Ap obtained from WDC-Kyoto are taken as indicator of geomagnetic activities. It is found that Dst index, solar wind velocity, proton temperature and the Bz component of magnetic field have higher values and increase just before the occurrence of these events. Larger and varying magnetic field mainly responsible for producing the short-term changes in geomagnetic intensity are observed during these events associated with coronal holes.

Whole-Brain Source-Reconstructed MEG-Data Reveal Reduced Long-Range Synchronization in Chronic Schizophrenia.

PubMed

Hirvonen, Jonni; Wibral, Michael; Palva, J Matias; Singer, Wolf; Uhlhaas, Peter; Palva, Satu

2017-01-01

Current theories of schizophrenia (ScZ) posit that the symptoms and cognitive dysfunctions arise from a dysconnection syndrome. However, studies that have examined this hypothesis with physiological data at realistic time scales are so far scarce. The current study employed a state-of-the-art approach using Magnetoencephalography (MEG) to test alterations in large-scale phase synchronization in a sample of n = 16 chronic ScZ patients, 10 males and n = 19 healthy participants, 10 males, during a perceptual closure task. We identified large-scale networks from source reconstructed MEG data using data-driven analyses of neuronal synchronization. Oscillation amplitudes and interareal phase-synchronization in the 3-120 Hz frequency range were estimated for 400 cortical parcels and correlated with clinical symptoms and neuropsychological scores. ScZ patients were characterized by a reduction in γ-band (30-120 Hz) oscillation amplitudes that was accompanied by a pronounced deficit in large-scale synchronization at γ-band frequencies. Synchronization was reduced within visual regions as well as between visual and frontal cortex and the reduction of synchronization correlated with elevated clinical disorganization. Accordingly, these data highlight that ScZ is associated with a profound disruption of transient synchronization, providing critical support for the notion that core aspect of the pathophysiology arises from an impairment in coordination of distributed neural activity.

Whole-Brain Source-Reconstructed MEG-Data Reveal Reduced Long-Range Synchronization in Chronic Schizophrenia

PubMed Central

Hirvonen, Jonni; Palva, J. Matias; Singer, Wolf; Uhlhaas, Peter

2017-01-01

Abstract Current theories of schizophrenia (ScZ) posit that the symptoms and cognitive dysfunctions arise from a dysconnection syndrome. However, studies that have examined this hypothesis with physiological data at realistic time scales are so far scarce. The current study employed a state-of-the-art approach using Magnetoencephalography (MEG) to test alterations in large-scale phase synchronization in a sample of n = 16 chronic ScZ patients, 10 males and n = 19 healthy participants, 10 males, during a perceptual closure task. We identified large-scale networks from source reconstructed MEG data using data-driven analyses of neuronal synchronization. Oscillation amplitudes and interareal phase-synchronization in the 3–120 Hz frequency range were estimated for 400 cortical parcels and correlated with clinical symptoms and neuropsychological scores. ScZ patients were characterized by a reduction in γ-band (30–120 Hz) oscillation amplitudes that was accompanied by a pronounced deficit in large-scale synchronization at γ-band frequencies. Synchronization was reduced within visual regions as well as between visual and frontal cortex and the reduction of synchronization correlated with elevated clinical disorganization. Accordingly, these data highlight that ScZ is associated with a profound disruption of transient synchronization, providing critical support for the notion that core aspect of the pathophysiology arises from an impairment in coordination of distributed neural activity. PMID:29085902

The large-scale ionospheric transient current system response to upstream solar wind IMF Bz north-south and south-north turnings as seen by the WIND satellite and the full SuperMAG network of ground based magnetometers

NASA Astrophysics Data System (ADS)

Dods, Joe; Chapman, Sandra; Gjerloev, Jesper

2017-04-01

We characterise the response of the quiet-time (no substorms or storms) large scale ionospheric convection system to north-south and south-north IMF turnings by using a dynamical network of ground-based magnetometers. Canonical correlation between all pairs of SuperMAG magnetometer stations in the northern hemisphere (MLat 50-82°) is used to establish the extent of near-simultaneous magnetic response between regions of MLT-MLat. Parameters and maps that describe spatial-temporal correlation are used to characterise the system and its response to the turnings aggregated over several hundred events. We find that regions that experience large increases in correlation post-turning coincide with typical locations of a two cell convection system and are influenced by the IMF By. The time between the turnings reaching the magnetopause and a network response is found to be ˜8-10 minutes and correlation in the dayside occurs 2-8 mins before that in the nightside.

Research on large-scale wind farm modeling

NASA Astrophysics Data System (ADS)

Ma, Longfei; Zhang, Baoqun; Gong, Cheng; Jiao, Ran; Shi, Rui; Chi, Zhongjun; Ding, Yifeng

2017-01-01

Due to intermittent and adulatory properties of wind energy, when large-scale wind farm connected to the grid, it will have much impact on the power system, which is different from traditional power plants. Therefore it is necessary to establish an effective wind farm model to simulate and analyze the influence wind farms have on the grid as well as the transient characteristics of the wind turbines when the grid is at fault. However we must first establish an effective WTGs model. As the doubly-fed VSCF wind turbine has become the mainstream wind turbine model currently, this article first investigates the research progress of doubly-fed VSCF wind turbine, and then describes the detailed building process of the model. After that investigating the common wind farm modeling methods and pointing out the problems encountered. As WAMS is widely used in the power system, which makes online parameter identification of the wind farm model based on off-output characteristics of wind farm be possible, with a focus on interpretation of the new idea of identification-based modeling of large wind farms, which can be realized by two concrete methods.

Comparative study of transient hydraulic tomography with varying parameterizations and zonations: Laboratory sandbox investigation

NASA Astrophysics Data System (ADS)

Luo, Ning; Zhao, Zhanfeng; Illman, Walter A.; Berg, Steven J.

2017-11-01

Transient hydraulic tomography (THT) is a robust method of aquifer characterization to estimate the spatial distributions (or tomograms) of both hydraulic conductivity (K) and specific storage (Ss). However, the highly-parameterized nature of the geostatistical inversion approach renders it computationally intensive for large-scale investigations. In addition, geostatistics-based THT may produce overly smooth tomograms when head data used to constrain the inversion is limited. Therefore, alternative model conceptualizations for THT need to be examined. To investigate this, we simultaneously calibrated different groundwater models with varying parameterizations and zonations using two cases of different pumping and monitoring data densities from a laboratory sandbox. Specifically, one effective parameter model, four geology-based zonation models with varying accuracy and resolution, and five geostatistical models with different prior information are calibrated. Model performance is quantitatively assessed by examining the calibration and validation results. Our study reveals that highly parameterized geostatistical models perform the best among the models compared, while the zonation model with excellent knowledge of stratigraphy also yields comparable results. When few pumping tests with sparse monitoring intervals are available, the incorporation of accurate or simplified geological information into geostatistical models reveals more details in heterogeneity and yields more robust validation results. However, results deteriorate when inaccurate geological information are incorporated. Finally, our study reveals that transient inversions are necessary to obtain reliable K and Ss estimates for making accurate predictions of transient drawdown events.

Parameter Uncertainty Analysis Using Monte Carlo Simulations for a Regional-Scale Groundwater Model

NASA Astrophysics Data System (ADS)

Zhang, Y.; Pohlmann, K.

2016-12-01

Regional-scale grid-based groundwater models for flow and transport often contain multiple types of parameters that can intensify the challenge of parameter uncertainty analysis. We propose a Monte Carlo approach to systematically quantify the influence of various types of model parameters on groundwater flux and contaminant travel times. The Monte Carlo simulations were conducted based on the steady-state conversion of the original transient model, which was then combined with the PEST sensitivity analysis tool SENSAN and particle tracking software MODPATH. Results identified hydrogeologic units whose hydraulic conductivity can significantly affect groundwater flux, and thirteen out of 173 model parameters that can cause large variation in travel times for contaminant particles originating from given source zones.

Time-resolved orbital angular momentum spectroscopy

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

Noyan, Mehmet A.; Kikkawa, James M.

We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.

Impacts into porous asteroids

NASA Astrophysics Data System (ADS)

Housen, Kevin R.; Sweet, William J.; Holsapple, Keith A.

2018-01-01

Many small bodies in the solar system have bulk density well below the solid density of the constituent mineral grains in their meteorite counterparts. Those low-density bodies undoubtedly have significant porosity, which is a key factor that affects the formation of impact craters. This paper summarizes the results of lab experiments in which materials with porosity ranging from 43% to 96% were impacted at ∼1800 m/s. The experiments were performed on a geotechnical centrifuge, in order to reproduce the lithostatic overburden stress and ejecta ballistics that occur in large-scale cratering events on asteroids or planetary satellites. Experiments performed at various accelerations, up to 514G, simulate the outcomes of impacts at size scales up to several tens of km in diameter. Our experiments show that an impact into a highly porous cohesionless material generates a large ovoid-shaped cavity, due to crushing by the outgoing shock. The cavity opens up to form a transient crater that grows until the material flow is arrested by gravity. The cavity then collapses to form the final crater. During collapse, finely crushed material that lines the cavity wall is carried down and collected in a localized region below the final crater floor. At large simulated sizes (high accelerations), most of the crater volume is formed by compaction, because growth of the transient crater is quickly arrested. Nearly all ejected material falls back into the crater, leaving the crater without an ejecta blanket. We find that such compaction cratering and suppression of the ejecta blankets occur for large craters on porous bodies when the ratio of the lithostatic stress at one crater depth to the crush strength of the target exceeds ∼0.005. The results are used to identify small solar system bodies on which compaction cratering likely occurs. A model is developed that gives the crater size and ejecta mass that would result for a specified impact into a porous object.

Role of the ocean's AMOC in setting the uptake efficiency of transient tracers

NASA Astrophysics Data System (ADS)

Romanou, A.; Marshall, J.; Kelley, M.; Scott, J. R.

2017-12-01

The central role played by the ocean's Atlantic Meridional Overturning Circulation (AMOC) in the uptake and sequestration of transient tracers is studied in a series of experiments with the Goddard Institute for Space Studies and Massachusetts Institute of Technology ocean circulation models. Forced by observed atmospheric time series of CFC-11, both models exhibit realistic distributions in the ocean, with similar surface biases but different response over time. To better understand what controls uptake, we ran idealized forcing experiments in which the AMOC strength varied over a wide range, bracketing the observations. We found that differences in the strength and vertical scale of the AMOC largely accounted for the different rates of CFC-11 uptake and vertical distribution thereof. A two-box model enables us to quantify and relate uptake efficiency of passive tracers to AMOC strength and how uptake efficiency decreases in time. We also discuss the relationship between passive tracer and heat uptake efficiency, of which the latter controls the transient climate response to anthropogenic forcing in the North Atlantic. We find that heat uptake efficiency is substantially less (by about a factor of 5) than that for a passive tracer.

Prediction of rarefied micro-nozzle flows using the SPARTA library

NASA Astrophysics Data System (ADS)

Deschenes, Timothy R.; Grot, Jonathan

2016-11-01

The accurate numerical prediction of gas flows within micro-nozzles can help evaluate the performance and enable the design of optimal configurations for micro-propulsion systems. Viscous effects within the large boundary layers can have a strong impact on the nozzle performance. Furthermore, the variation in collision length scales from continuum to rarefied preclude the use of continuum-based computational fluid dynamics. In this paper, we describe the application of a massively parallel direct simulation Monte Carlo (DSMC) library to predict the steady-state and transient flow through a micro-nozzle. The nozzle's geometric configuration is described in a highly flexible manner to allow for the modification of the geometry in a systematic fashion. The transient simulation highlights a strong shock structure that forms within the converging portion of the nozzle when the expanded gas interacts with the nozzle walls. This structure has a strong impact on the buildup of the gas in the nozzle and affects the boundary layer thickness beyond the throat in the diverging section of the nozzle. Future work will look to examine the transient thrust and integrate this simulation capability into a web-based rarefied gas dynamics prediction software, which is currently under development.

Transient lateral photovoltaic effect in synthetic single crystal diamond

NASA Astrophysics Data System (ADS)

Prestopino, G.; Marinelli, M.; Milani, E.; Verona, C.; Verona-Rinati, G.

2017-10-01

A transient lateral photovoltaic effect (LPE) is reported for a metal-semiconductor structure of synthetic single crystal diamond (SCD). A SCD Schottky photodiode was specifically designed to measure a LPE under collimated irradiation from a tunable pulsed laser. A transient lateral photovoltage parallel to the Schottky junction was indeed detected. LPE on the p-type doped SCD side showed a non-linearity of 2% and a fast response time, with a rise time of 2 μs and a decay time of 12 μs. The position sensitivity (up to 30 mV/mm at a laser wavelength of 220 nm and a pulse energy density of 2.9 μJ/mm2) was measured as a function of laser wavelength, and an ultraviolet (UV)-to-visible contrast ratio of about four orders of magnitude with a sharp cutoff at 225 nm was observed. Our results demonstrate that a large LPE at UV wavelengths is achievable in synthetic single crystal diamond, potentially opening opportunities for the study and application of LPE in diamond and for the fabrication of high performance visible blind UV position sensitive detectors with high sensitivity and microsecond scale response time.

The bomb 14C transient in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Rodgers, Keith B.; Schrag, Daniel P.; Cane, Mark A.; Naik, Naomi H.

2000-04-01

A modeling study of the bomb 14C transient is presented for the Pacific Ocean. A primitive equation ocean circulation model has been configured for a high-resolution domain that accounts for the Indonesian Throughflow (ITF). Four separate runs were performed: (1) seasonal forcing with 20 Sv of ITF transport, (2) seasonal forcing with 10 Sv of ITF transport, (3) seasonal forcing with no ITF transport, and (4) interannual forcing with 15 Sv of ITF transport. This study has two main objectives. First, it is intended to describe the time evolution of the bomb 14C transient. This serves as a tool with which one can identify the physical processes controlling the evolving bomb 14C distribution in the Pacific thermocline and thus provides an interpretive framework for the database of Δ14C measurements in the Pacific. Second, transient tracers are applied to the physical oceanographic problem of intergyre exchange. This is of importance in furthering our understanding of the potential role of the upper Pacific Ocean in climate variability. We use bomb 14C as a dye tracer of intergyre exchange between the subtropical gyres and the equatorial upwelling regions of the equatorial Pacific. Observations show that while the atmospheric Δ14C signal peaked in the early to mid-1960s, the Δ14C levels in the surface water waters of the subtropical gyres peaked near 1970, and the Δ14C of surface waters in the equatorial Pacific continued to rise through the 1980s. It is shown that the model exhibits skill in representing the large-scale observed features observed for the bomb 14C transient in the Pacific Ocean. The model successfully captures the basin-scale inventories of bomb 14C in the tropics as well as in the extratropics of the North Pacific. For the equatorial Pacific this is attributed to the model's high meridional resolution. The discrepancies in the three-dimensional distribution of bomb 14C between the model and data are discussed within the context of the dynamical controls on the Δ14C distribution of bomb 14C in the Pacific.

Coronal mass ejections and their sheath regions in interplanetary space

NASA Astrophysics Data System (ADS)

Kilpua, Emilia; Koskinen, Hannu E. J.; Pulkkinen, Tuija I.

2017-11-01

Interplanetary coronal mass ejections (ICMEs) are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs.

Iterative learning-based decentralized adaptive tracker for large-scale systems: a digital redesign approach.

PubMed

Tsai, Jason Sheng-Hong; Du, Yan-Yi; Huang, Pei-Hsiang; Guo, Shu-Mei; Shieh, Leang-San; Chen, Yuhua

2011-07-01

In this paper, a digital redesign methodology of the iterative learning-based decentralized adaptive tracker is proposed to improve the dynamic performance of sampled-data linear large-scale control systems consisting of N interconnected multi-input multi-output subsystems, so that the system output will follow any trajectory which may not be presented by the analytic reference model initially. To overcome the interference of each sub-system and simplify the controller design, the proposed model reference decentralized adaptive control scheme constructs a decoupled well-designed reference model first. Then, according to the well-designed model, this paper develops a digital decentralized adaptive tracker based on the optimal analog control and prediction-based digital redesign technique for the sampled-data large-scale coupling system. In order to enhance the tracking performance of the digital tracker at specified sampling instants, we apply the iterative learning control (ILC) to train the control input via continual learning. As a result, the proposed iterative learning-based decentralized adaptive tracker not only has robust closed-loop decoupled property but also possesses good tracking performance at both transient and steady state. Besides, evolutionary programming is applied to search for a good learning gain to speed up the learning process of ILC. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Hydraulic head applications of flow logs in the study of heterogeneous aquifers

USGS Publications Warehouse

Paillet, Frederick L.

2001-01-01

Permeability profiles derived from high-resolution flow logs in heterogeneous aquifers provide a limited sample of the most permeable beds or fractures determining the hydraulic properties of those aquifers. This paper demonstrates that flow logs can also be used to infer the large-scale properties of aquifers surrounding boreholes. The analysis is based on the interpretation of the hydraulic head values estimated from the flow log analysis. Pairs of quasi-steady flow profiles obtained under ambient conditions and while either pumping or injecting are used to estimate the hydraulic head in each water-producing zone. Although the analysis yields localized estimates of transmissivity for a few water-producing zones, the hydraulic head estimates apply to the farfield aquifers to which these zones are connected. The hydraulic head data are combined with information from other sources to identify the large-scale structure of heterogeneous aquifers. More complicated cross-borehole flow experiments are used to characterize the pattern of connection between large-scale aquifer units inferred from the hydraulic head estimates. The interpretation of hydraulic heads in situ under steady and transient conditions is illustrated by several case studies, including an example with heterogeneous permeable beds in an unconsolidated aquifer, and four examples with heterogeneous distributions of bedding planes and/or fractures in bedrock aquifers.

Impact Cratering Physics al Large Planetary Scales

NASA Astrophysics Data System (ADS)

Ahrens, Thomas J.

2007-06-01

Present understanding of the physics controlling formation of ˜10^3 km diameter, multi-ringed impact structures on planets were derived from the ideas of Scripps oceanographer, W. Van Dorn, University of London's, W, Murray, and, Caltech's, D. O'Keefe who modeled the vertical oscillations (gravity and elasticity restoring forces) of shock-induced melt and damaged rock within the transient crater immediately after the downward propagating hemispheric shock has processed rock (both lining, and substantially below, the transient cavity crater). The resulting very large surface wave displacements produce the characteristic concentric, multi-ringed basins, as stored energy is radiated away and also dissipated upon inducing further cracking. Initial calculational description, of the above oscillation scenario, has focused upon on properly predicting the resulting density of cracks, and, their orientations. A new numerical version of the Ashby--Sammis crack damage model is coupled to an existing shock hydrodynamics code to predict impact induced damage distributions in a series of 15--70 cm rock targets from high speed impact experiments for a range of impactor type and velocity. These are compared to results of crack damage distributions induced in crustal rocks with small arms impactors and mapped ultrasonically in recent Caltech experiments (Ai and Ahrens, 2006).

Flares from Galactic Centre pulsars: a new class of X-ray transients?

NASA Astrophysics Data System (ADS)

Giannios, Dimitrios; Lorimer, Duncan R.

2016-06-01

Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known in this region, the Galactic Centre (GC) should harbour a large number of neutron stars. Population syntheses suggest several thousand neutron stars may be present in the GC. Many of these could be highly energetic millisecond pulsars which are also proposed to be responsible for the GC gamma-ray excess. We propose that the presence of a neutron star within 0.03 pc from Sgr A* can be revealed by the shock interactions with the disc around the central black hole. As we demonstrate, these interactions result in observable transient non-thermal X-ray and gamma-ray emission over time-scales of months, provided that the spin-down luminosity of the neutron star is Lsd ˜ 1035 erg s-1. Current limits on the population of normal and millisecond pulsars in the GC region suggest that a number of such pulsars are present with such luminosities.

The supermassive black hole coincident with the luminous transient ASASSN-15lh

NASA Astrophysics Data System (ADS)

Krühler, T.; Fraser, M.; Leloudas, G.; Schulze, S.; Stone, N. C.; van Velzen, S.; Amorin, R.; Hjorth, J.; Jonker, P. G.; Kann, D. A.; Kim, S.; Kuncarayakti, H.; Mehner, A.; Nicuesa Guelbenzu, A.

2018-02-01

The progenitors of astronomical transients are linked to a specific stellar population and galactic environment, and observing their host galaxies hence constrains the physical nature of the transient itself. Here, we use imaging from the Hubble Space Telescope, and spatially resolved, medium-resolution spectroscopy from the Very Large Telescope obtained with X-shooter and MUSE to study the host of the very luminous transient ASASSN-15lh. The dominant stellar population at the transient site is old (around 1 to 2 Gyr) without signs of recent star formation. We also detect emission from ionized gas, originating from three different, time invariable, narrow components of collisionally excited metal and Balmer lines. The ratios of emission lines in the Baldwin-Phillips-Terlevich diagnostic diagram indicate that the ionization source is a weak active galactic nucleus with a black hole mass of M• = 5-3+8 × 108 M⊙, derived through the M•-σ relation. The narrow line components show spatial and velocity offsets on scales of 1 kpc and 500 km s-1, respectively; these offsets are best explained by gas kinematics in the narrow-line region. The location of the central component, which we argue is also the position of the supermassive black hole, aligns with that of the transient within an uncertainty of 170 pc. Using this positional coincidence as well as other similarities with the hosts of tidal disruption events, we strengthen the argument that the transient emission observed as ASASSN-15lh is related to the disruption of a star around a supermassive black hole, most probably spinning with a Kerr parameter a• ≳ 0.5. Based on observations at ESO, Program IDs: 097.D-1054, 297.B-5035, 099.D-0115.The data used in this manuscript are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A14

Validation of mathematical model for CZ process using small-scale laboratory crystal growth furnace

NASA Astrophysics Data System (ADS)

Bergfelds, Kristaps; Sabanskis, Andrejs; Virbulis, Janis

2018-05-01

The present material is focused on the modelling of small-scale laboratory NaCl-RbCl crystal growth furnace. First steps towards fully transient simulations are taken in the form of stationary simulations that deal with the optimization of material properties to match the model to experimental conditions. For this purpose, simulation software primarily used for the modelling of industrial-scale silicon crystal growth process was successfully applied. Finally, transient simulations of the crystal growth are presented, giving a sufficient agreement to experimental results.

Transient sodium current at subthreshold voltages: activation by EPSP waveforms

PubMed Central

Carter, Brett C.; Giessel, Andrew J.; Sabatini, Bernardo L.; Bean, Bruce P.

2012-01-01

Summary Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also “persistent” sodium current, a non-inactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37 °C with near-physiological ionic conditions. Unexpectedly, in both cell types small voltage steps at subthreshold voltages activated a substantial component of transient sodium current as well as persistent current. Subthreshold EPSP-like waveforms also activated a large component of transient sodium current, but IPSP-like waveforms engaged primarily persistent sodium current with only a small additional transient component. Activation of transient as well as persistent sodium current at subthreshold voltages produces amplification of EPSPs that is sensitive to the rate of depolarization and can help account for the dependence of spike threshold on depolarization rate, as previously observed in vivo. PMID:22998875

Rotating waves during human sleep spindles organize global patterns of activity that repeat precisely through the night

PubMed Central

Muller, Lyle; Piantoni, Giovanni; Koller, Dominik; Cash, Sydney S; Halgren, Eric; Sejnowski, Terrence J

2016-01-01

During sleep, the thalamus generates a characteristic pattern of transient, 11-15 Hz sleep spindle oscillations, which synchronize the cortex through large-scale thalamocortical loops. Spindles have been increasingly demonstrated to be critical for sleep-dependent consolidation of memory, but the specific neural mechanism for this process remains unclear. We show here that cortical spindles are spatiotemporally organized into circular wave-like patterns, organizing neuronal activity over tens of milliseconds, within the timescale for storing memories in large-scale networks across the cortex via spike-time dependent plasticity. These circular patterns repeat over hours of sleep with millisecond temporal precision, allowing reinforcement of the activity patterns through hundreds of reverberations. These results provide a novel mechanistic account for how global sleep oscillations and synaptic plasticity could strengthen networks distributed across the cortex to store coherent and integrated memories. DOI: http://dx.doi.org/10.7554/eLife.17267.001 PMID:27855061

Imaging different components of a tectonic tremor sequence in southwestern Japan using an automatic statistical detection and location method

NASA Astrophysics Data System (ADS)

Poiata, Natalia; Vilotte, Jean-Pierre; Bernard, Pascal; Satriano, Claudio; Obara, Kazushige

2018-06-01

In this study, we demonstrate the capability of an automatic network-based detection and location method to extract and analyse different components of tectonic tremor activity by analysing a 9-day energetic tectonic tremor sequence occurring at the downdip extension of the subducting slab in southwestern Japan. The applied method exploits the coherency of multiscale, frequency-selective characteristics of non-stationary signals recorded across the seismic network. Use of different characteristic functions, in the signal processing step of the method, allows to extract and locate the sources of short-duration impulsive signal transients associated with low-frequency earthquakes and of longer-duration energy transients during the tectonic tremor sequence. Frequency-dependent characteristic functions, based on higher-order statistics' properties of the seismic signals, are used for the detection and location of low-frequency earthquakes. This allows extracting a more complete (˜6.5 times more events) and time-resolved catalogue of low-frequency earthquakes than the routine catalogue provided by the Japan Meteorological Agency. As such, this catalogue allows resolving the space-time evolution of the low-frequency earthquakes activity in great detail, unravelling spatial and temporal clustering, modulation in response to tide, and different scales of space-time migration patterns. In the second part of the study, the detection and source location of longer-duration signal energy transients within the tectonic tremor sequence is performed using characteristic functions built from smoothed frequency-dependent energy envelopes. This leads to a catalogue of longer-duration energy sources during the tectonic tremor sequence, characterized by their durations and 3-D spatial likelihood maps of the energy-release source regions. The summary 3-D likelihood map for the 9-day tectonic tremor sequence, built from this catalogue, exhibits an along-strike spatial segmentation of the long-duration energy-release regions, matching the large-scale clustering features evidenced from the low-frequency earthquake's activity analysis. Further examination of the two catalogues showed that the extracted short-duration low-frequency earthquakes activity coincides in space, within about 10-15 km distance, with the longer-duration energy sources during the tectonic tremor sequence. This observation provides a potential constraint on the size of the longer-duration energy-radiating source region in relation with the clustering of low-frequency earthquakes activity during the analysed tectonic tremor sequence. We show that advanced statistical network-based methods offer new capabilities for automatic high-resolution detection, location and monitoring of different scale-components of tectonic tremor activity, enriching existing slow earthquakes catalogues. Systematic application of such methods to large continuous data sets will allow imaging the slow transient seismic energy-release activity at higher resolution, and therefore, provide new insights into the underlying multiscale mechanisms of slow earthquakes generation.

Continuous microalgal cultivation in a laboratory-scale photobioreactor under seasonal day-night irradiation: experiments and simulation.

PubMed

Bertucco, Alberto; Beraldi, Mariaelena; Sforza, Eleonora

2014-08-01

In this work, the production of Scenedesmus obliquus in a continuous flat-plate laboratory-scale photobioreactor (PBR) under alternated day-night cycles was tested both experimentally and theoretically. Variation of light intensity according to the four seasons of the year were simulated experimentally by a tunable LED lamp, and effects on microalgal growth and productivity were measured to evaluate the conversion efficiency of light energy into biomass during the different seasons. These results were used to validate a mathematical model for algae growth that can be applied to simulate a large-scale production unit, carried out in a flat-plate PBR of similar geometry. The cellular concentration in the PBR was calculated in both steady-state and transient conditions, and the value of the maintenance kinetic term was correlated to experimental profiles. The relevance of this parameter was finally outlined.

JPL Big Data Technologies for Radio Astronomy

NASA Astrophysics Data System (ADS)

Jones, Dayton L.; D'Addario, L. R.; De Jong, E. M.; Mattmann, C. A.; Rebbapragada, U. D.; Thompson, D. R.; Wagstaff, K.

2014-04-01

During the past three years the Jet Propulsion Laboratory has been working on several technologies to deal with big data challenges facing next-generation radio arrays, among other applications. This program has focused on the following four areas: 1) We are investigating high-level ASIC architectures that reduce power consumption for cross-correlation of data from large interferometer arrays by one to two orders of magnitude. The cost of operations for the Square Kilometre Array (SKA), which may be dominated by the cost of power for data processing, is a serious concern. A large improvement in correlator power efficiency could have a major positive impact. 2) Data-adaptive algorithms (machine learning) for real-time detection and classification of fast transient signals in high volume data streams are being developed and demonstrated. Studies of the dynamic universe, particularly searches for fast (<< 1 second) transient events, require that data be analyzed rapidly and with robust RFI rejection. JPL, in collaboration with the International Center for Radio Astronomy Research in Australia, has developed a fast transient search system for eventual deployment on ASKAP. In addition, a real-time transient detection experiment is now running continuously and commensally on NRAO's Very Long Baseline Array. 3) Scalable frameworks for data archiving, mining, and distribution are being applied to radio astronomy. A set of powerful open-source Object Oriented Data Technology (OODT) tools is now available through Apache. OODT was developed at JPL for Earth science data archives, but it is proving to be useful for radio astronomy, planetary science, health care, Earth climate, and other large-scale archives. 4) We are creating automated, event-driven data visualization tools that can be used to extract information from a wide range of complex data sets. Visualization of complex data can be improved through algorithms that detect events or features of interest and autonomously generate images or video to display those features. This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Detection of right-to-left shunts: comparison between the International Consensus and Spencer Logarithmic Scale criteria.

PubMed

Lao, Annabelle Y; Sharma, Vijay K; Tsivgoulis, Georgios; Frey, James L; Malkoff, Marc D; Navarro, Jose C; Alexandrov, Andrei V

2008-10-01

International Consensus Criteria (ICC) consider right-to-left shunt (RLS) present when Transcranial Doppler (TCD) detects even one microbubble (microB). Spencer Logarithmic Scale (SLS) offers more grades of RLS with detection of >30 microB corresponding to a large shunt. We compared the yield of ICC and SLS in detection and quantification of a large RLS. We prospectively evaluated paradoxical embolism in consecutive patients with ischemic strokes or transient ischemic attack (TIA) using injections of 9 cc saline agitated with 1 cc of air. Results were classified according to ICC [negative (no microB), grade I (1-20 microB), grade II (>20 microB or "shower" appearance of microB), and grade III ("curtain" appearance of microB)] and SLS criteria [negative (no microB), grade I (1-10 microB), grade II (11-30 microB), grade III (31100 microB), grade IV (101300 microB), grade V (>300 microB)]. The RLS size was defined as large (>4 mm) using diameter measurement of the septal defects on transesophageal echocardiography (TEE). TCD comparison to TEE showed 24 true positive, 48 true negative, 4 false positive, and 2 false negative cases (sensitivity 92.3%, specificity 92.3%, positive predictive value (PPV) 85.7%, negative predictive value (NPV) 96%, and accuracy 92.3%) for any RLS presence. Both ICC and SLS were 100% sensitive for detection of large RLS. ICC and SLS criteria yielded a false positive rate of 24.4% and 7.7%, respectively when compared to TEE. Although both grading scales provide agreement as to any shunt presence, using the Spencer Scale grade III or higher can decrease by one-half the number of false positive TCD diagnoses to predict large RLS on TEE.

RACORO continental boundary layer cloud investigations. Part I: Case study development and ensemble large-scale forcings

DOE PAGES

Vogelmann, Andrew M.; Fridlind, Ann M.; Toto, Tami; ...

2015-06-19

Observation-based modeling case studies of continental boundary layer clouds have been developed to study cloudy boundary layers, aerosol influences upon them, and their representation in cloud- and global-scale models. Three 60-hour case study periods span the temporal evolution of cumulus, stratiform, and drizzling boundary layer cloud systems, representing mixed and transitional states rather than idealized or canonical cases. Based on in-situ measurements from the RACORO field campaign and remote-sensing observations, the cases are designed with a modular configuration to simplify use in large-eddy simulations (LES) and single-column models. Aircraft measurements of aerosol number size distribution are fit to lognormal functionsmore » for concise representation in models. Values of the aerosol hygroscopicity parameter, κ, are derived from observations to be ~0.10, which are lower than the 0.3 typical over continents and suggestive of a large aerosol organic fraction. Ensemble large-scale forcing datasets are derived from the ARM variational analysis, ECMWF forecasts, and a multi-scale data assimilation system. The forcings are assessed through comparison of measured bulk atmospheric and cloud properties to those computed in 'trial' large-eddy simulations, where more efficient run times are enabled through modest reductions in grid resolution and domain size compared to the full-sized LES grid. Simulations capture many of the general features observed, but the state-of-the-art forcings were limited at representing details of cloud onset, and tight gradients and high-resolution transients of importance. Methods for improving the initial conditions and forcings are discussed. The cases developed are available to the general modeling community for studying continental boundary clouds.« less

The seesaw space, a vector space to identify and characterize large-scale structures at 1 AU

NASA Astrophysics Data System (ADS)

Lara, A.; Niembro, T.

2017-12-01

We introduce the seesaw space, an orthonormal space formed by the local and the global fluctuations of any of the four basic solar parameters: velocity, density, magnetic field and temperature at any heliospheric distance. The fluctuations compare the standard deviation of a moving average of three hours against the running average of the parameter in a month (consider as the local fluctuations) and in a year (global fluctuations) We created this new vectorial spaces to identify the arrival of transients to any spacecraft without the need of an observer. We applied our method to the one-minute resolution data of WIND spacecraft from 1996 to 2016. To study the behavior of the seesaw norms in terms of the solar cycle, we computed annual histograms and fixed piecewise functions formed by two log-normal distributions and observed that one of the distributions is due to large-scale structures while the other to the ambient solar wind. The norm values in which the piecewise functions change vary in terms of the solar cycle. We compared the seesaw norms of each of the basic parameters due to the arrival of coronal mass ejections, co-rotating interaction regions and sector boundaries reported in literature. High seesaw norms are due to large-scale structures. We found three critical values of the norms that can be used to determined the arrival of coronal mass ejections. We present as well general comparisons of the norms during the two maxima and the minimum solar cycle periods and the differences of the norms due to large-scale structures depending on each period.

Integrating transient heterogeneity of non-photochemical quenching in shade-grown heterobaric leaves of avocado (Persea americana L.): responses to CO2 concentration, stomatal occlusion, dehydration and relative humidity.

PubMed

Takayama, Kotaro; King, Diana; Robinson, Sharon A; Osmond, Barry

2013-11-01

Long-lived shade leaves of avocado had extremely low rates of photosynthesis. Gas exchange measurements of photosynthesis were of limited use, so we resorted to Chl fluorescence imaging (CFI) and spot measurements to evaluate photosynthetic electron transport rates (ETRs) and non-photochemical quenching (NPQ). Imaging revealed a remarkable transient heterogeneity of NPQ during photosynthetic induction in these hypostomatous, heterobaric leaves, but was adequately integrated by spot measurements, despite long-lasting artifacts from repeated saturating flashes during assays. Major veins (mid-vein, first- and second-order veins) defined areas of more static large-scale heterogeneous NPQ, with more dynamic small-scale heterogeneity most strongly expressed in mesophyll cells between third- and fourth-order veins. Both responded to external CO2 concentration ([CO2]), occlusion of stomata with Vaseline™, leaf dehydration and relative humidity (RH). We interpreted these responses in terms of independent behavior of stomata in adjacent areoles that was largely expressed through CO2-limited photosynthesis. Heterogeneity was most pronounced and prolonged in the absence of net CO2 fixation in 100 p.p.m. [CO2] when respiratory and photorespiratory CO2 cycling constrained the inferred ETR to ~75% of values in 400 or 700 p.p.m. [CO2]. Likewise, sustained higher NPQ under Vaseline™, after dehydration or at low RH, also restricted ETR to ~75% of control values. Low NPQ in chloroplast-containing cells adjacent to major veins but remote from stomata suggested internal sources of high [CO2] in these tissues.

Regional Climate Modeling of Volcanic Eruptions and the Arctic Climate System: A Baffin Island Case Study

NASA Astrophysics Data System (ADS)

Losic, M.; Robock, A.

2010-12-01

It is well-understood that the effects of volcanic aerosol loading into the stratosphere are transient, with global cooling lasting only a few years after a single large eruption. Geological evidence collected from Northern Baffin Island, Canada, suggests ice cap growth began soon after a succession of several large eruptions in the 13th century, and they did not start to melt until roughly a century ago. We investigate which feedbacks allowed these ice caps to be maintained long after the transient forcing of the volcanic aerosols, by conducting sensitivity studies with the Weather Research and Forecasting (WRF) Model and Polar WRF, a version of WRF developed specifically for the polar regions. Results from an ensemble of month-long regional simulations over Baffin Island suggest that better treatment of snow and ice in Polar WRF improves our regional climate simulations. Thus, sensitivity test results from decade-long runs with imposed changes to boundary condition temperatures and carbon dioxide concentrations using Polar WRF are presented. Preliminary findings suggest that not only large scale but localized climate feedbacks play an important role in the responses of the ice caps after temperature and carbon dioxide forcings are applied. The results from these and further sensitivity tests will provide insight into the influence of regional feedbacks on the persistence of these ice caps long after the 13th century eruptions.

Multi-scale multi-point observation of dipolarization in the near-Earth's magnetotail

NASA Astrophysics Data System (ADS)

Nakamura, R.; Varsani, A.; Genestreti, K.; Nakamura, T.; Baumjohann, W.; Birn, J.; Le Contel, O.; Nagai, T.

2017-12-01

We report on evolution of the dipolarization in the near-Earth plasma sheet during two intense substorms based on observations when the four spacecraft of the Magnetospheric Multiscale (MMS) together with GOES and Geotail were located in the near Earth magnetotail. These multiple spacecraft together with the ground-based magnetogram enabled to obtain the location of the large- scale substorm current wedge (SCW) and overall changes in the plasma sheet configuration. MMS was located in the southern hemisphere at the outer plasma sheet and observed fast flow disturbances associated with dipolarizations. The high time-resolution measurements from MMS enable us to detect the rapid motion of the field structures and the flow disturbances separately and to resolve signatures below the ion-scales. We found small-scale transient field-aligned current sheets associated with upward streaming cold plasmas and Hall-current layers in the fast flow shear region. Observations of these current structures are compared with simulations of reconnection jets.

The Problem of Late ART initiation in Sub-Saharan Africa: A Transient Aspect of Scale-up or a Long-term Phenomenon?

PubMed Central

Lahuerta, Maria; Ue, Frances; Hoffman, Susie; Elul, Batya; Kulkarni, Sarah Gorrell; Wu, Yingfeng; Nuwagaba-Biribonwoha, Harriet; Remien, Robert H.; Sadr, Wafaa El; Nash, Denis

2013-01-01

Efforts to scale-up HIV care and treatment have been successful at initiating large numbers of patients onto antiretroviral therapy (ART), although persistent challenges remain to optimizing scale-up effectiveness in both resource-rich and resource-limited settings. Among the most important are very high rates of ART initiation in the advanced stages of HIV disease, which in turn drive morbidity, mortality, and onward transmission of HIV. With a focus on sub-Saharan Africa, this review article presents a conceptual framework for a broader discussion of the persistent problem of late ART initiation, including a need for more focus on the upstream precursors (late HIV diagnosis and late enrollment into HIV care) and their determinants. Without additional research and identification of multilevel interventions that successfully promote earlier initiation of ART, the problem of late ART initiation will persist, significantly undermining the long-term impact of HIV care scale-up on reducing mortality and controlling the HIV epidemic. PMID:23377739

The excavation stage of basin formation - A qualitative model

NASA Technical Reports Server (NTRS)

Croft, S. K.

1981-01-01

One of the most complex problems in planetary geology and geophysics is the determination of the nature of the impact cratering processes at scales of tens to thousands of kilometers that produce the complex morphological structures of multiring basins. The cratering process is frequently considered to be divided into three stages, including a short high-pressure stage of initial contact between the projectile and the planetary crust, a longer excavation or cratering flow stage culminating in the formation of a transient crater, and a still longer modification stage during which the transient crater is modified into the observed final geologic form. The transient crater may be considered as the initial boundary condition of the modification stage. In the present investigation, the nature of the transient crater is indicated by the cratering flow field determined from numerical simulations of the excavation stage. Attention is given to empirical and theoretical scaling.

The Very Large Array: Pioneering New Directions in Radio Astronomy

NASA Astrophysics Data System (ADS)

McKinnon, Mark

2018-01-01

The Very Large Array (VLA) started science operations in 1980 and was rechristened the Jansky VLA after a major upgrade to its electronics system was completed in 2012. The VLA plays a prominent role in scientific discovery through studies of the Solar System, star and planet formation, galaxy formation, and time domain astronomy. It has attained iconic status as one of the most scientifically productive telescopes on EarthIn 2017, three major initiatives were launched at the VLA with the goal of maintaining its leadership role and impact in radio astronomy in the near and long term future:1. In September, the VLA embarked upon the VLA Sky Survey (VLASS), the highest resolution survey ever undertaken at radio wavelengths. The survey was planned in consultation with the astronomy community and will be used to search for transients, study the polarization properties of extragalactic radio sources, and study highly obscured sources in our Galaxy.2. Detailed planning for a next generation VLA (ngVLA) began in earnest in 2017. The ngVLA will open a new window on the Universe through ultra-sensitive imaging of thermal line and continuum emission down to milliarcsecond resolution, as well as unprecedented broad-band continuum polarimetric imaging of non-thermal processes. A proposal for the instrument will be submitted to the 2020 Decadal Survey.3. A multi-year program to replace the 40+ year old infrastructure at the VLA site was initiated in 2017. The program includes the replacement of the VLA’s electrical infrastructure in 2018, improvements to the VLA rail system, and the replacement of heavy maintenance equipment.The VLA continued to play a major role in discovering and explaining the physics of transient phenomena in 2017, to include fast transients, such as fast radio bursts, and long time scale transients, such as novae, tidal disruption events, and gamma-ray bursts.More thorough descriptions of the VLASS and ngVLA, along with the science that can be done with them, and of VLA observations of transient phenomena are given in the presentations in this session.

An asset-based approach to vulnerability: the case of small-scale fishing areas in Cameroon and Nigeria.

PubMed

Chiwaula, Levison S; Witt, Rudolf; Waibel, Hermann

2011-01-01

This paper analyses vulnerability to poverty of rural small-scale fishing communities using cross-section data from 295 households in Cameroon and 267 in Nigeria. We propose a vulnerability measure that incorporates the idea of asset poverty into the concept of expected poverty, which allows decomposing expected poverty into expected structural-chronic, structural-transient, and stochastic-transient poverty. The findings show that most households in our study areas are expected to be structurally-chronic and structurally-transient poor. This underlines the importance of asset formation for long-term poverty reduction strategies. Further refinements are possible with longitudinal data and information about future states of nature.

A multi-scale comparison of trait linkages to environmental and spatial variables in fish communities across a large freshwater lake.

PubMed

Strecker, Angela L; Casselman, John M; Fortin, Marie-Josée; Jackson, Donald A; Ridgway, Mark S; Abrams, Peter A; Shuter, Brian J

2011-07-01

Species present in communities are affected by the prevailing environmental conditions, and the traits that these species display may be sensitive indicators of community responses to environmental change. However, interpretation of community responses may be confounded by environmental variation at different spatial scales. Using a hierarchical approach, we assessed the spatial and temporal variation of traits in coastal fish communities in Lake Huron over a 5-year time period (2001-2005) in response to biotic and abiotic environmental factors. The association of environmental and spatial variables with trophic, life-history, and thermal traits at two spatial scales (regional basin-scale, local site-scale) was quantified using multivariate statistics and variation partitioning. We defined these two scales (regional, local) on which to measure variation and then applied this measurement framework identically in all 5 study years. With this framework, we found that there was no change in the spatial scales of fish community traits over the course of the study, although there were small inter-annual shifts in the importance of regional basin- and local site-scale variables in determining community trait composition (e.g., life-history, trophic, and thermal). The overriding effects of regional-scale variables may be related to inter-annual variation in average summer temperature. Additionally, drivers of fish community traits were highly variable among study years, with some years dominated by environmental variation and others dominated by spatially structured variation. The influence of spatial factors on trait composition was dynamic, which suggests that spatial patterns in fish communities over large landscapes are transient. Air temperature and vegetation were significant variables in most years, underscoring the importance of future climate change and shoreline development as drivers of fish community structure. Overall, a trait-based hierarchical framework may be a useful conservation tool, as it highlights the multi-scaled interactive effect of variables over a large landscape.

Transient behavior of vertical scaling of mesoscale winds in the light of atmospheric turbulence transfer in and between synoptic and mesoscales

NASA Astrophysics Data System (ADS)

Barros, A. P.; Eghdami, M.

2017-12-01

High-resolution ( 1 km) numerical weather prediction models are capable of producing atmospheric spectra over synoptic and mesoscale ranges. Nogueira and Barros (2015) showed using high-resolution simulations in the Andes that the horizontal scale invariant behavior of atmospheric wind and water fields in the model is a process-dependent transient property that varies with the underlying dynamics. They found a sharp transition in the scaling parameters between non-convective and convective conditions. Spectral slopes around 2-2.3 arise under non-convective or very weak convective conditions, whereas in convective situations the transient scaling exponents remain under -5/3. Based on these results, Nogueira and Barros (2015) proposed a new sub-grid scale parameterization of clouds obtained from coarse resolution states alone. High Reynolds number direct numerical simulations of two-dimensional turbulence transfer shows that atmospheric flows involve concurrent direct (downscale) enstrophy transfer in the synoptic scales and inverse (upscale) kinetic energy transfer from the meso- to the synoptic-scales. In this study we use an analogy to investigate the transient behavior of kinetic energy spectra of winds over the Andes and Southern Appalachian Mountains representative of high and middle mountains, respectively. In the unstable conditions and particularly in the Planetary Boundary Layer (PBL) the spectral slopes approach -5/3 associated with the upscale KE turbulence transfer. However, in the stable conditions and above the planetary boundary layer, the spectra slopes approach steeper slopes about -3 associated with the downscale KE transfer. The underlying topography, surface roughness, diurnal heating and cooling and moist processes add to the complexity of the problem by introducing anisotropy and sources and sinks of energy. A comprehensive analysis and scaling of flow behavior conditional on stability regime for both KE and moist processes (total water, cloud water, rainfall) is necessary to elucidate scale-interactions among different processes.

Plasma jets in the near-Earth's magnetotail (Julius Bartels Medal Lecture)

NASA Astrophysics Data System (ADS)

Nakamura, Rumi

2014-05-01

The Earth's magnetosphere is formed as a consequence of the interaction between the magnetized solar wind and the terrestrial magnetic field. While the large-scale and average (>hours) properties of the Earth's magnetotail current sheet can be well described by overall solar wind-magnetosphere interaction, the most dramatic energy conversion process takes place in an explosive manner involving transient (up to several minutes) and localized (up to a few RE) phenomena in the plasma sheet/current sheet regions. One of the most clear observables of such processes are the localized and transient plasma jets called Bursty bulk flows (BBF), embedding velocity peaks of 1-min duration, which are called flow bursts. This talk is a review of the current understanding of these plasma jets by highlighting the results from multi-spacecraft observations by the Cluster and THEMIS spacecraft. The first four-spacecraft mission Cluster crossed the near-Earth plasma sheet with inter-spacecraft distance of about 250 km to 10000 km, ideal for studying local structures of the flow bursts. The five-spacecraft THEMIS mission , separated by larger distances , succeeded to monitor the large-scale evolution of the fast flows from the mid-tail to the inner magnetosphere. Multi-point observations of BBFS have established the importance of measuring local gradients of the fields and the plasma to understand the BBF structures such as the spatial scales and 3D structure of localized Earthward convecting flux tubes. Among others the magnetic field disturbance forming at the front of BBF, called dipolarization front (DF), has been intensively studied. From the propagation properties of DF relative to the flows and by comparing with ionospheric data, the evolution of the fast flows in terms of magnetosphere-ionospheric coupling through field-aligned currents are established. An important aspect of BBF is the interaction of the Earthward plasma jets and the Earth's dipole field. Multi-point observations combined with ground-based observations enabled to resolve how the BBFs are braked , diverted, or bounced back at the high-pressure gradient region. The multi-point capabilities in space enabled to study the BBF structure as well as large-scale evolution of BBFs. These processes are also universal processes in space plasmas and are, for example, associated with the reconnection process during the solar flares or leading to auroral phenomena at different planets.

Storage in alluvial deposits controls the timing of particle delivery from large watersheds, filtering upland erosional signals and delaying benefits from watershed best management practices

NASA Astrophysics Data System (ADS)

Pizzuto, J. E.; Skalak, K.; Karwan, D. L.

2017-12-01

Transport of suspended sediment and sediment-borne constituents (here termed fluvial particles) through large river systems can be significantly influenced by episodic storage in floodplains and other alluvial deposits. Geomorphologists quantify the importance of storage using sediment budgets, but these data alone are insufficient to determine how storage influences the routing of fluvial particles through river corridors across large spatial scales. For steady state systems, models that combine sediment budget data with "waiting time distributions" (to define how long deposited particles remain stored until being remobilized) and velocities during transport events can provide useful predictions. Limited field data suggest that waiting time distributions are well represented by power laws, extending from <1 to >104 years, while the probability of storage defined by sediment budgets varies from 0.1 km-1 for small drainage basins to 0.001 km-1 for the world's largest watersheds. Timescales of particle delivery from large watersheds are determined by storage rather than by transport processes, with most particles requiring 102 -104 years to reach the basin outlet. These predictions suggest that erosional "signals" induced by climate change, tectonics, or anthropogenic activity will be transformed by storage before delivery to the outlets of large watersheds. In particular, best management practices (BMPs) implemented in upland source areas, designed to reduce the loading of fluvial particles to estuarine receiving waters, will not achieve their intended benefits for centuries (or longer). For transient systems, waiting time distributions cannot be constant, but will vary as portions of transient sediment "pulses" enter and are later released from storage. The delivery of sediment pulses under transient conditions can be predicted by adopting the hypothesis that the probability of erosion of stored particles will decrease with increasing "age" (where age is defined as the elapsed time since deposition). Then, waiting time and age distributions for stored particles become predictions based on the architecture of alluvial storage and the tendency for erosional processes to preferentially remove younger deposits, improving assessment of watershed BMPs and other important applications.

The fast transient sky with Gaia

NASA Astrophysics Data System (ADS)

Wevers, Thomas; Jonker, Peter G.; Hodgkin, Simon T.; Kostrzewa-Rutkowska, Zuzanna; Harrison, Diana L.; Rixon, Guy; Nelemans, Gijs; Roelens, Maroussia; Eyer, Laurent; van Leeuwen, Floor; Yoldas, Abdullah

2018-01-01

The ESA Gaia satellite scans the whole sky with a temporal sampling ranging from seconds and hours to months. Each time a source passes within the Gaia field of view, it moves over 10 charge coupled devices (CCDs) in 45 s and a light curve with 4.5 s sampling (the crossing time per CCD) is registered. Given that the 4.5 s sampling represents a virtually unexplored parameter space in optical time domain astronomy, this data set potentially provides a unique opportunity to open up the fast transient sky. We present a method to start mining the wealth of information in the per CCD Gaia data. We perform extensive data filtering to eliminate known onboard and data processing artefacts, and present a statistical method to identify sources that show transient brightness variations on ≲2 h time-scales. We illustrate that by using the Gaia photometric CCD measurements, we can detect transient brightness variations down to an amplitude of 0.3 mag on time-scales ranging from 15 s to several hours. We search an area of ∼23.5 deg2 on the sky and find four strong candidate fast transients. Two candidates are tentatively classified as flares on M-dwarf stars, while one is probably a flare on a giant star and one potentially a flare on a solar-type star. These classifications are based on archival data and the time-scales involved. We argue that the method presented here can be added to the existing Gaia Science Alerts infrastructure for the near real-time public dissemination of fast transient events.

Slow-blue nuclear hypervariables in PanSTARRS-1

DOE PAGES

Lawrence, A.; Bruce, A. G.; MacLeod, C.; ...

2016-09-08

We discuss 76 large amplitude transients (Δm > 1.5) occurring in the nuclei of galaxies, nearly all with no previously known active galactic nucleus (AGN). They have been discovered as part of the Pan-STARRS1 (PS1) 3π survey, by comparison with Sloan Digital Sky Survey (SDSS) photometry a decade earlier, and then monitored with the Liverpool Telescope, and studied spectroscopically with the William Herschel Telescope (WHT). Based on colours, light-curve shape, and spectra, these transients fall into four groups. A few are misclassified stars or objects of unknown type. Some are red/fast transients and are known or likely nuclear supernovae. Amore » few are either radio sources or erratic variables and so likely blazars. However the majority (~66 per cent) are blue and evolve slowly, on a time-scale of years. Spectroscopy shows them to be AGN at z ~0.3 – 1.4, which must have brightened since the SDSS photometry by around an order of magnitude. It is likely that these objects were in fact AGN a decade ago, but too weak to be recognized by SDSS; they could then be classed as ‘hypervariable’ AGN. By searching the SDSS Stripe 82 quasar database, we find 15 similar objects. We discuss several possible explanations for these slow-blue hypervariables – (i) unusually luminous tidal disruption events; (ii) extinction events; (iii) changes in accretion state; and (iv) large amplitude microlensing by stars in foreground galaxies. A mixture of explanations (iii) and (iv) seems most likely. As a result, both hold promise of considerable new insight into the AGN phenomenon.« less

Slow-blue nuclear hypervariables in PanSTARRS-1

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

Lawrence, A.; Bruce, A. G.; MacLeod, C.

We discuss 76 large amplitude transients (Δm > 1.5) occurring in the nuclei of galaxies, nearly all with no previously known active galactic nucleus (AGN). They have been discovered as part of the Pan-STARRS1 (PS1) 3π survey, by comparison with Sloan Digital Sky Survey (SDSS) photometry a decade earlier, and then monitored with the Liverpool Telescope, and studied spectroscopically with the William Herschel Telescope (WHT). Based on colours, light-curve shape, and spectra, these transients fall into four groups. A few are misclassified stars or objects of unknown type. Some are red/fast transients and are known or likely nuclear supernovae. Amore » few are either radio sources or erratic variables and so likely blazars. However the majority (~66 per cent) are blue and evolve slowly, on a time-scale of years. Spectroscopy shows them to be AGN at z ~0.3 – 1.4, which must have brightened since the SDSS photometry by around an order of magnitude. It is likely that these objects were in fact AGN a decade ago, but too weak to be recognized by SDSS; they could then be classed as ‘hypervariable’ AGN. By searching the SDSS Stripe 82 quasar database, we find 15 similar objects. We discuss several possible explanations for these slow-blue hypervariables – (i) unusually luminous tidal disruption events; (ii) extinction events; (iii) changes in accretion state; and (iv) large amplitude microlensing by stars in foreground galaxies. A mixture of explanations (iii) and (iv) seems most likely. As a result, both hold promise of considerable new insight into the AGN phenomenon.« less

Production of recombinant adeno-associated vectors using two bioreactor configurations at different scales

PubMed Central

Negrete, Alejandro; Kotin, Robert M.

2007-01-01

The conventional methods for producing recombinant adeno-associated virus (rAAV) rely on transient transfection of adherent mammalian cells. To gain acceptance and achieve current good manufacturing process (cGMP) compliance, clinical grade rAAV production process should have the following qualities: simplicity, consistency, cost effectiveness, and scalability. Currently, the only viable method for producing rAAV in large-scale, e.g.≥1016 particles per production run, utilizes Baculovirus Expression Vectors (BEVs) and insect cells suspension cultures. The previously described rAAV production in 40 L culture using a stirred tank bioreactor requires special conditions for implementation and operation not available in all laboratories. Alternatives to producing rAAV in stirred-tank bioreactors are single-use, disposable bioreactors, e.g. Wave™. The disposable bags are purchased pre-sterilized thereby eliminating the need for end-user sterilization and also avoiding cleaning steps between production runs thus facilitating the production process. In this study, rAAV production in stirred tank and Wave™ bioreactors was compared. The working volumes were 10 L and 40 L for the stirred tank bioreactors and 5 L and 20 L for the Wave™ bioreactors. Comparable yields of rAAV, ~2e+13 particles per liter of cell culture were obtained in all volumes and configurations. These results demonstrate that producing rAAV in large scale using BEVs is reproducible, scalable, and independent of the bioreactor configuration. Keywords: adeno-associated vectors; large-scale production; stirred tank bioreactor; wave bioreactor; gene therapy. PMID:17606302

Transient Stability of the US Western Interconnection with High Wind and Solar Generation

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

Clark, Kara; Miller, Nicholas W.; Shao, Miaolei

The addition of large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. This paper reports the results of a study that investigated the transient stability of the WI with high penetrations of wind and solar generation. The mainmore » goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.« less

Considering transient population dynamics in the conservation of slow life-history species: An application to the sandhill crane

USGS Publications Warehouse

Gerber, Brian D.; Kendall, William L.

2016-01-01

The importance of transient dynamics of structured populations is increasingly recognized in ecology, yet these implications are not largely considered in conservation practices. We investigate transient and long-term population dynamics to demonstrate the process and utility of incorporating transient dynamics into conservation research and to better understand the population management of slow life-history species; these species can be theoretically highly sensitive to short- and long-term transient effects. We are specifically interested in the effects of anthropogenic removal of individuals from populations, such as caused by harvest, poaching, translocation, or incidental take. We use the sandhill crane (Grus canadensis) as an exemplar species; it is long-lived, has low reproduction, late maturity, and multiple populations are subject to sport harvest. We found sandhill cranes to have extremely high potential, but low likelihood for transient dynamics, even when the population is being harvested. The typically low population growth rate of slow life-history species appears to buffer against many perturbations causing large transient effects. Transient dynamics will dominate population trajectories of these species when stage structures are highly biased towards the younger and non-reproducing individuals, a situation that may be rare in established populations of long-lived animals. However, short-term transient population growth can be highly sensitive to vital rates that are relatively insensitive under equilibrium, suggesting that stage structure should be known if perturbation analysis is used to identify effective conservation strategies. For populations of slow life-history species that are not prone to large perturbations to their most productive individuals, population growth may be approximated by equilibrium dynamics.

Imaging the distribution of transient viscosity after the 2016 Mw 7.1 Kumamoto earthquake

NASA Astrophysics Data System (ADS)

Moore, James D. P.; Yu, Hang; Tang, Chi-Hsien; Wang, Teng; Barbot, Sylvain; Peng, Dongju; Masuti, Sagar; Dauwels, Justin; Hsu, Ya-Ju; Lambert, Valère; Nanjundiah, Priyamvada; Wei, Shengji; Lindsey, Eric; Feng, Lujia; Shibazaki, Bunichiro

2017-04-01

The deformation of mantle and crustal rocks in response to stress plays a crucial role in the distribution of seismic and volcanic hazards, controlling tectonic processes ranging from continental drift to earthquake triggering. However, the spatial variation of these dynamic properties is poorly understood as they are difficult to measure. We exploited the large stress perturbation incurred by the 2016 earthquake sequence in Kumamoto, Japan, to directly image localized and distributed deformation. The earthquakes illuminated distinct regions of low effective viscosity in the lower crust, notably beneath the Mount Aso and Mount Kuju volcanoes, surrounded by larger-scale variations of viscosity across the back-arc. This study demonstrates a new potential for geodesy to directly probe rock rheology in situ across many spatial and temporal scales.

Coronal Mass Ejections and their Implications for the Corona and Heliosphere

NASA Technical Reports Server (NTRS)

Antiochos, Spiro K.

2008-01-01

Coronal mass ejections (CMEs) are the largest and most energetic form of transients that connect the Sun to the heliosphere. They are critically important both for understanding the physical mechanisms of explosive solar activity and for predicting space weather. Furthermore they are an extreme example of how cross-scale coupling can play a critical role in determining the properties of a large-scale dynamical system. In this presentation CME theories are reviewed and the latest results from 3D numerical modeling of CME initiation propagation to the heliosphere are presented. In particular the focus is on the breakout model, but many of the results hold for the flux rope models as well. The implications of these results for understanding heliospheric structure and dynamics and for upcoming space missions will be discussed.

Techno-economic analysis of a transient plant-based platform for monoclonal antibody production

PubMed Central

Nandi, Somen; Kwong, Aaron T.; Holtz, Barry R.; Erwin, Robert L.; Marcel, Sylvain; McDonald, Karen A.

2016-01-01

ABSTRACT Plant-based biomanufacturing of therapeutic proteins is a relatively new platform with a small number of commercial-scale facilities, but offers advantages of linear scalability, reduced upstream complexity, reduced time to market, and potentially lower capital and operating costs. In this study we present a detailed process simulation model for a large-scale new “greenfield” biomanufacturing facility that uses transient agroinfiltration of Nicotiana benthamiana plants grown hydroponically indoors under light-emitting diode lighting for the production of a monoclonal antibody. The model was used to evaluate the total capital investment, annual operating cost, and cost of goods sold as a function of mAb expression level in the plant (g mAb/kg fresh weight of the plant) and production capacity (kg mAb/year). For the Base Case design scenario (300 kg mAb/year, 1 g mAb/kg fresh weight, and 65% recovery in downstream processing), the model predicts a total capital investment of $122 million dollars and cost of goods sold of $121/g including depreciation. Compared with traditional biomanufacturing platforms that use mammalian cells grown in bioreactors, the model predicts significant reductions in capital investment and >50% reduction in cost of goods compared with published values at similar production scales. The simulation model can be modified or adapted by others to assess the profitability of alternative designs, implement different process assumptions, and help guide process development and optimization. PMID:27559626

Techno-economic analysis of a transient plant-based platform for monoclonal antibody production.

PubMed

Nandi, Somen; Kwong, Aaron T; Holtz, Barry R; Erwin, Robert L; Marcel, Sylvain; McDonald, Karen A

Plant-based biomanufacturing of therapeutic proteins is a relatively new platform with a small number of commercial-scale facilities, but offers advantages of linear scalability, reduced upstream complexity, reduced time to market, and potentially lower capital and operating costs. In this study we present a detailed process simulation model for a large-scale new "greenfield" biomanufacturing facility that uses transient agroinfiltration of Nicotiana benthamiana plants grown hydroponically indoors under light-emitting diode lighting for the production of a monoclonal antibody. The model was used to evaluate the total capital investment, annual operating cost, and cost of goods sold as a function of mAb expression level in the plant (g mAb/kg fresh weight of the plant) and production capacity (kg mAb/year). For the Base Case design scenario (300 kg mAb/year, 1 g mAb/kg fresh weight, and 65% recovery in downstream processing), the model predicts a total capital investment of $122 million dollars and cost of goods sold of $121/g including depreciation. Compared with traditional biomanufacturing platforms that use mammalian cells grown in bioreactors, the model predicts significant reductions in capital investment and >50% reduction in cost of goods compared with published values at similar production scales. The simulation model can be modified or adapted by others to assess the profitability of alternative designs, implement different process assumptions, and help guide process development and optimization.

Screening and large-scale expression of membrane proteins in mammalian cells for structural studies.

PubMed

Goehring, April; Lee, Chia-Hsueh; Wang, Kevin H; Michel, Jennifer Carlisle; Claxton, Derek P; Baconguis, Isabelle; Althoff, Thorsten; Fischer, Suzanne; Garcia, K Christopher; Gouaux, Eric

2014-11-01

Structural, biochemical and biophysical studies of eukaryotic membrane proteins are often hampered by difficulties in overexpression of the candidate molecule. Baculovirus transduction of mammalian cells (BacMam), although a powerful method to heterologously express membrane proteins, can be cumbersome for screening and expression of multiple constructs. We therefore developed plasmid Eric Gouaux (pEG) BacMam, a vector optimized for use in screening assays, as well as for efficient production of baculovirus and robust expression of the target protein. In this protocol, we show how to use small-scale transient transfection and fluorescence-detection size-exclusion chromatography (FSEC) experiments using a GFP-His8-tagged candidate protein to screen for monodispersity and expression level. Once promising candidates are identified, we describe how to generate baculovirus, transduce HEK293S GnTI(-) (N-acetylglucosaminyltransferase I-negative) cells in suspension culture and overexpress the candidate protein. We have used these methods to prepare pure samples of chicken acid-sensing ion channel 1a (cASIC1) and Caenorhabditis elegans glutamate-gated chloride channel (GluCl) for X-ray crystallography, demonstrating how to rapidly and efficiently screen hundreds of constructs and accomplish large-scale expression in 4-6 weeks.

Screening and large-scale expression of membrane proteins in mammalian cells for structural studies

PubMed Central

Goehring, April; Lee, Chia-Hsueh; Wang, Kevin H.; Michel, Jennifer Carlisle; Claxton, Derek P.; Baconguis, Isabelle; Althoff, Thorsten; Fischer, Suzanne; Garcia, K. Christopher; Gouaux, Eric

2014-01-01

Structural, biochemical and biophysical studies of eukaryotic membrane proteins are often hampered by difficulties in over-expression of the candidate molecule. Baculovirus transduction of mammalian cells (BacMam), although a powerful method to heterologously express membrane proteins, can be cumbersome for screening and expression of multiple constructs. We therefore developed plasmid Eric Gouaux (pEG) BacMam, a vector optimized for use in screening assays, as well as for efficient production of baculovirus and robust expression of the target protein. In this protocol we show how to use small-scale transient transfection and fluorescence-detection, size-exclusion chromatography (FSEC) experiments using a GFP-His8 tagged candidate protein to screen for monodispersity and expression level. Once promising candidates are identified, we describe how to generate baculovirus, transduce HEK293S GnTI− (N-acetylglucosaminyltransferase I-negative) cells in suspension culture, and over-express the candidate protein. We have used these methods to prepare pure samples of chicken acid-sensing ion channel 1a (cASIC1) and Caenorhabditis elegans glutamate-gated chloride channel (GluCl), for X-ray crystallography, demonstrating how to rapidly and efficiently screen hundreds of constructs and accomplish large-scale expression in 4-6 weeks. PMID:25299155

Physical experiments and analysis on the generation and evolution of tsunami-induced turbulent coherent structures

NASA Astrophysics Data System (ADS)

Kalligeris, Nikos; Lynett, Patrick

2017-11-01

Numerous historical accounts describe the formation of ``whirpools'' inside ports and harbors during tsunami events, causing port operation disruptions. Videos from the Japan 2011 tsunami revealed complex nearshore flow patters, resulting from the interaction of tsunami-induced currents with the man-made coastline, and the generation of large eddies (or turbulent coherent structures) in numerous ports and harbors near the earthquake epicenter. The aim of this work is to study the generation and evolution of tsunami-induced turbulent coherent structures (TCS) in a well-controlled environment using realistic scaling. A physical configuration is created in the image of a port entrance at a scale of 1:27 and a small-amplitude, long period wave creates a transient flow through the asymmetric harbor channel. A separated region forms, which coupled with the transient flow, leads to the formation of a stable monopolar TCS. The surface flow is examined through mono- and stereo-PTV techniques to extract surface velocity vectors. Surface velocity maps and vortex flow profiles are used to study the experimental TCS generation and evolution, and characterize the TCS structure. Analytical tools are used to describe the TCS growth rate and kinetic energy decay. This work was funded by the National Science Foundation NEES Research program, with Award Number 1135026.

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

Tiede, D.M.; Kellogg, E.C.; Kolaczkowski, S.

We have carried out a more stringent test for electron transfer along the M-pathway at low temperature. This has been done by directly detecting transient states generated from the trapped PH{sub L}{sup {minus}}H{sub M} state in Rps viridis reaction centers. Under these conditions the normal forward electron transfer to H{sub L} is blocked, and the yield of transient P{sup +}H{sub M}{sup {minus}} is determined with respect to the lifetime of P*. Others have measured this lifetime to be 20 ps at room temperature. This enhances the opportunity for detecting a reaction between P* and H{sub M} by 20-fold. These experimentsmore » find that transient bleaching of the P990 nm band occurs from the trapped PH{sub L}{sup {minus}}H{sub M} state on the ns time scale, with a quantum yield of 0.09 {plus minus} 0.06 compared to normal photochemistry. This measurement places an upper limit on the yield of a transient P{sup +}H{sub M}{sup {minus}} state. The measured yield and estimated lifetime of P* suggest that the maximum electron transfer rate P* {yields} H{sub M} is about 5 {times} 10{sup 9} sec{sup {minus}1} ({tau}{sub M} = 200 ps). This corresponds to a k{sub L}/k{sub M} ratio of at least 200. This large value of the branching ratio is remarkable in view of the structural symmetry of the reaction center. 13 refs., 2 figs.« less

Spontaneous, synchronous electrical activity in neonatal mouse cortical neurones

PubMed Central

Corlew, Rebekah; Bosma, Martha M; Moody, William J

2004-01-01

Spontaneous [Ca2+]i transients were measured in the mouse neocortex from embryonic day 16 (E16) to postnatal day 6 (P6). On the day of birth (P0), cortical neurones generated widespread, highly synchronous [Ca2+]i transients over large areas. On average, 52% of neurones participated in these transients, and in 20% of slices, an average of 80% participated. These transients were blocked by TTX and nifedipine, indicating that they resulted from Ca2+ influx during electrical activity, and occurred at a mean frequency of 0.91 min−1. The occurrence of this activity was highly centred at P0: at E16 and P2 an average of only 15% and 24% of neurones, respectively, participated in synchronous transients, and they occurred at much lower frequencies at both E16 and P2 than at P0. The overall frequency of [Ca2+]i transients in individual cells did not change between E16 and P2, just the degree of their synchronicity. The onset of this spontaneous, synchronous activity correlated with a large increase in Na+ current density that occurred just before P0, and its cessation with a large decrease in resting resistance that occurred just after P2. This widespread, synchronous activity may serve a variety of functions in the neonatal nervous system. PMID:15297578

Biogrid--a microfluidic device for large-scale enzyme-free dissociation of stem cell aggregates.

PubMed

Wallman, Lars; Åkesson, Elisabet; Ceric, Dario; Andersson, Per Henrik; Day, Kelly; Hovatta, Outi; Falci, Scott; Laurell, Thomas; Sundström, Erik

2011-10-07

Culturing stem cells as free-floating aggregates in suspension facilitates large-scale production of cells in closed systems, for clinical use. To comply with GMP standards, the use of substances such as proteolytic enzymes should be avoided. Instead of enzymatic dissociation, the growing cell aggregates may be mechanically cut at passage, but available methods are not compatible with large-scale cell production and hence translation into the clinic becomes a severe bottle-neck. We have developed the Biogrid device, which consists of an array of micrometerscale knife edges, micro-fabricated in silicon, and a manifold in which the microgrid is placed across the central fluid channel. By connecting one side of the Biogrid to a syringe or a pump and the other side to the cell culture, the culture medium with suspended cell aggregates can be aspirated, forcing the aggregates through the microgrid, and ejected back to the cell culture container. Large aggregates are thereby dissociated into smaller fragments while small aggregates pass through the microgrid unaffected. As proof-of-concept, we demonstrate that the Biogrid device can be successfully used for repeated passage of human neural stem/progenitor cells cultured as so-called neurospheres, as well as for passage of suspension cultures of human embryonic stem cells. We also show that human neural stem/progenitor cells tolerate transient pressure changes far exceeding those that will occur in a fluidic system incorporating the Biogrid microgrids. Thus, by using the Biogrid device it is possible to mechanically passage large quantities of cells in suspension cultures in closed fluidic systems, without the use of proteolytic enzymes.

Imaging of earthquake faults using small UAVs as a pathfinder for air and space observations

USGS Publications Warehouse

Donnellan, Andrea; Green, Joseph; Ansar, Adnan; Aletky, Joseph; Glasscoe, Margaret; Ben-Zion, Yehuda; Arrowsmith, J. Ramón; DeLong, Stephen B.

2017-01-01

Large earthquakes cause billions of dollars in damage and extensive loss of life and property. Geodetic and topographic imaging provide measurements of transient and long-term crustal deformation needed to monitor fault zones and understand earthquakes. Earthquake-induced strain and rupture characteristics are expressed in topographic features imprinted on the landscapes of fault zones. Small UAVs provide an efficient and flexible means to collect multi-angle imagery to reconstruct fine scale fault zone topography and provide surrogate data to determine requirements for and to simulate future platforms for air- and space-based multi-angle imaging.

Grand unification scale primordial black holes: consequences and constraints.

PubMed

Anantua, Richard; Easther, Richard; Giblin, John T

2009-09-11

A population of very light primordial black holes which evaporate before nucleosynthesis begins is unconstrained unless the decaying black holes leave stable relics. We show that gravitons Hawking radiated from these black holes would source a substantial stochastic background of high frequency gravititational waves (10(12) Hz or more) in the present Universe. These black holes may lead to a transient period of matter-dominated expansion. In this case the primordial Universe could be temporarily dominated by large clusters of "Hawking stars" and the resulting gravitational wave spectrum is independent of the initial number density of primordial black holes.

Simulations of Instabilities in Complex Valve and Feed Systems

NASA Technical Reports Server (NTRS)

Ahuja, Vineet; Hosangadi, Ashvin; Shipman, Jeremy; Cavallo, Peter A.

2006-01-01

CFD analyses are playing an increasingly important role in identifying and characterizing flow induced instabilities in rocket engine test facilities and flight systems. In this paper, we analyze instability mechanisms that range from turbulent pressure fluctuations due to vortex shedding in structurally complex valve systems to flow resonance in plug cavities to large scale pressure fluctuations due to collapse of cavitation induced vapor clouds. Furthermore, we discuss simulations of transient behavior related to valve motion that can serve as guidelines for valve scheduling. Such predictions of valve response to varying flow conditions is of crucial importance to engine operation and testing.

5 Percent Ares I Scale Model Acoustic Test: Overpressure Characterization and Analysis

NASA Technical Reports Server (NTRS)

Alvord, David; Casiano, Matthew; McDaniels, Dave

2011-01-01

During the ignition of a ducted solid rocket motor (SRM), rapid expansion of injected hot gases from the motor into a confined volume causes the development of a steep fronted wave. This low frequency transient wave propagates outward from the exhaust duct, impinging the vehicle and ground structures. An unsuppressed overpressure wave can potentially cause modal excitation in the structures and vehicle, subsequently leading to damage. This presentation details the ignition transient f indings from the 5% Ares I Scale Model Acoustic Test (ASMAT). The primary events of the ignition transient environment induced by the SRM are the ignition overpressure (IOP), duct overpressure (DOP), and source overpressure (SOP). The resulting observations include successful knockdown of the IOP environment through use of a Space Shuttle derived IOP suppression system, a potential load applied to the vehicle stemming from instantaneous asymmetrical IOP and DOP wave impingement, and launch complex geometric influences on the environment. The results are scaled to a full-scale Ares I equivalent and compared with heritage data including Ares I-X and both suppressed and unsuppressed Space Shuttle IOP environments.

Transient nature of cooperation by pay-it-forward reciprocity

PubMed Central

Horita, Yutaka; Takezawa, Masanori; Kinjo, Takuji; Nakawake, Yo; Masuda, Naoki

2016-01-01

Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation. PMID:26786178

"Virtual shear box" experiments of stress and slip cycling within a subduction interface mélange

NASA Astrophysics Data System (ADS)

Webber, Sam; Ellis, Susan; Fagereng, Åke

2018-04-01

What role does the progressive geometric evolution of subduction-related mélange shear zones play in the development of strain transients? We use a "virtual shear box" experiment, based on outcrop-scale observations from an ancient exhumed subduction interface - the Chrystalls Beach Complex (CBC), New Zealand - to constrain numerical models of slip processes within a meters-thick shear zone. The CBC is dominated by large, competent clasts surrounded by interconnected weak matrix. Under constant slip velocity boundary conditions, models of the CBC produce stress cycling behavior, accompanied by mixed brittle-viscous deformation. This occurs as a consequence of the reorganization of competent clasts, and the progressive development and breakdown of stress bridges as clasts mutually obstruct one another. Under constant shear stress boundary conditions, the models show periods of relative inactivity punctuated by aseismic episodic slip at rapid rates (meters per year). Such a process may contribute to the development of strain transients such as slow slip.

Review: Moisture loading—the hidden information in groundwater observation well records

NASA Astrophysics Data System (ADS)

van der Kamp, Garth; Schmidt, Randy

2017-12-01

Changes of total moisture mass above an aquifer such as snow accumulation, soil moisture, and storage at the water table, represent changes of mechanical load acting on the aquifer. The resulting moisture-loading effects occur in all observation well records for confined aquifers. Deep observation wells therefore act as large-scale geological weighing lysimeters, referred to as "geolysimeters". Barometric pressure effects on groundwater levels are a similar response to surface loading and are familiar to every hydrogeologist dealing with the "barometric efficiency" of observation wells. Moisture-loading effects are small and generally not recognized because they are obscured by hydraulic head fluctuations due to other causes, primarily barometric pressure changes. For semiconfined aquifers, long-term moisture-loading effects may be dissipated and obscured by transient flow through overlying aquitards. Removal of barometric and earth tide effects from observation well records allows identification of moisture loading and comparison with hydrological observations, and also comparison with the results of numerical models that can account for transient groundwater flow.

Computational technique and performance of Transient Inundation Model for Rivers--2 Dimensional (TRIM2RD) : a depth-averaged two-dimensional flow model

USGS Publications Warehouse

Fulford, Janice M.

2003-01-01

A numerical computer model, Transient Inundation Model for Rivers -- 2 Dimensional (TrimR2D), that solves the two-dimensional depth-averaged flow equations is documented and discussed. The model uses a semi-implicit, semi-Lagrangian finite-difference method. It is a variant of the Trim model and has been used successfully in estuarine environments such as San Francisco Bay. The abilities of the model are documented for three scenarios: uniform depth flows, laboratory dam-break flows, and large-scale riverine flows. The model can start computations from a ?dry? bed and converge to accurate solutions. Inflows are expressed as source terms, which limits the use of the model to sufficiently long reaches where the flow reaches equilibrium with the channel. The data sets used by the investigation demonstrate that the model accurately propagates flood waves through long river reaches and simulates dam breaks with abrupt water-surface changes.

Transient nature of cooperation by pay-it-forward reciprocity.

PubMed

Horita, Yutaka; Takezawa, Masanori; Kinjo, Takuji; Nakawake, Yo; Masuda, Naoki

2016-01-20

Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation.

Coherent structure in solar wind C{sup 6+}/C{sup 4+} ionic composition data during the quiet-sun conditions of 2008

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

Edmondson, J. K.; Lepri, S. T.; Zurbuchen, T. H.

2013-11-20

This analysis offers evidence of characteristic scale sizes in solar wind charge state data measured in situ for 13 quiet-Sun Carrington rotations in 2008. Using a previously established novel methodology, we analyze the wavelet power spectrum of the charge state ratio C{sup 6+}/C{sup 4+} measured in situ by ACE/SWICS for 2 hr and 12 minute cadence. We construct a statistical significance level in the wavelet power spectrum to quantify the interference effects arising from filling missing data in the time series, allowing extraction of significant power from the measured data to a resolution of 24 minutes. We analyze each waveletmore » power spectrum for transient coherency and global periodicities resulting from the superposition of repeating coherent structures. From the significant wavelet power spectra, we find evidence for a general upper limit on individual transient coherency of ∼10 days. We find evidence for a set of global periodicities between 4-5 hr and 35-45 days. We find evidence for the distribution of individual transient coherency scales consisting of two distinct populations. Below the ∼2 day timescale, the distribution is reasonably approximated by an inverse power law, whereas for scales ≳2 days, the distribution levels off, showing discrete peaks at common coherency scales. In addition, by organizing the transient coherency scale distributions by wind type, we find that these larger, common coherency scales are more prevalent and well defined in coronal hole wind. Finally, we discuss the implications of our results for current theories of solar wind generation and describe future work for determining the relationship between the coherent structures in our ionic composition data and the structure of the coronal magnetic field.« less

Under-ice ambient noise in Eastern Beaufort Sea, Canadian Arctic, and its relation to environmental forcing.

PubMed

Kinda, G Bazile; Simard, Yvan; Gervaise, Cédric; Mars, Jérome I; Fortier, Louis

2013-07-01

This paper analyzes an 8-month time series (November 2005 to June 2006) of underwater noise recorded at the mouth of the Amundsen Gulf in the marginal ice zone of the western Canadian Arctic when the area was >90% ice covered. The time-series of the ambient noise component was computed using an algorithm that filtered out transient acoustic events from 7-min hourly recordings of total ocean noise over a [0-4.1] kHz frequency band. Under-ice ambient noise did not respond to thermal changes, but showed consistent correlations with large-scale regional ice drift, wind speed, and measured currents in upper water column. The correlation of ambient noise with ice drift peaked for locations at ranges of ~300 km off the mouth of the Amundsen Gulf. These locations are within the multi-year ice plume that extends westerly along the coast in the Eastern Beaufort Sea due to the large Beaufort Gyre circulation. These results reveal that ambient noise in Eastern Beaufort Sea in winter is mainly controlled by the same meteorological and oceanographic forcing processes that drive the ice drift and the large-scale circulation in this part of the Arctic Ocean.

Large-scale modeling on the fate and transport of polycyclic aromatic hydrocarbons (PAHs) in multimedia over China

NASA Astrophysics Data System (ADS)

Huang, Y.; Liu, M.; Wada, Y.; He, X.; Sun, X.

2017-12-01

In recent decades, with rapid economic growth, industrial development and urbanization, expanding pollution of polycyclic aromatic hydrocarbons (PAHs) has become a diversified and complicated phenomenon in China. However, the availability of sufficient monitoring activities for PAHs in multi-compartment and the corresponding multi-interface migration processes are still limited, especially at a large geographic area. In this study, we couple the Multimedia Fate Model (MFM) to the Community Multi-Scale Air Quality (CMAQ) model in order to consider the fugacity and the transient contamination processes. This coupled dynamic contaminant model can evaluate the detailed local variations and mass fluxes of PAHs in different environmental media (e.g., air, surface film, soil, sediment, water and vegetation) across different spatial (a county to country) and temporal (days to years) scales. This model has been applied to a large geographical domain of China at a 36 km by 36 km grid resolution. The model considers response characteristics of typical environmental medium to complex underlying surface. Results suggest that direct emission is the main input pathway of PAHs entering the atmosphere, while advection is the main outward flow of pollutants from the environment. In addition, both soil and sediment act as the main sink of PAHs and have the longest retention time. Importantly, the highest PAHs loadings are found in urbanized and densely populated regions of China, such as Yangtze River Delta and Pearl River Delta. This model can provide a good scientific basis towards a better understanding of the large-scale dynamics of environmental pollutants for land conservation and sustainable development. In a next step, the dynamic contaminant model will be integrated with the continental-scale hydrological and water resources model (i.e., Community Water Model, CWatM) to quantify a more accurate representation and feedbacks between the hydrological cycle and water quality at even larger geographical domains. Keywords: PAHs; Community multi-scale air quality model; Multimedia fate model; Land use

Transient and Steady-state Tests of the Space Power Research Engine with Resistive and Motor Loads

NASA Technical Reports Server (NTRS)

Rauch, Jeffrey S.; Kankam, M. David

1995-01-01

The NASA Lewis Research Center (LeRC) has been testing free-piston Stirling engine/linear alternators (FPSE/LA) to develop advanced power convertors for space-based electrical power generation. Tests reported herein were performed to evaluate the interaction and transient behavior of FPSE/LA-based power systems with typical user loads. Both resistive and small induction motor loads were tested with the space power research engine (SPRE) power system. Tests showed that the control system could maintain constant long term voltage and stable periodic operation over a large range of engine operating parameters and loads. Modest resistive load changes were shown to cause relatively large voltage and, therefore, piston and displacer amplitude excursions. Starting a typical small induction motor was shown to cause large and, in some cases, deleterious voltage transients. The tests identified the need for more effective controls, if FPSE/LAs are to be used for stand-alone power systems. The tests also generated a large body of transient dynamic data useful for analysis code validation.

Transient and steady-state tests of the space power research engine with resistive and motor loads

NASA Astrophysics Data System (ADS)

Rauch, Jeffrey S.; Kankam, M. David

1995-01-01

The NASA Lewis Research Center (LeRC) has been testing free-piston Stirling engine/linear alternators (FPSE/LA) to develop advanced power convertors for space-based electrical power generation. Tests reported herein were performed to evaluate the interaction and transient behavior of FPSE/LA-based power systems with typical user loads. Both resistive and small induction motor loads were tested with the space power research engine (SPRE) power system. Tests showed that the control system could maintain constant long term voltage and stable periodic operation over a large range of engine operating parameters and loads. Modest resistive load changes were shown to cause relatively large voltage and, therefore, piston and displacer amplitude excursions. Starting a typical small induction motor was shown to cause large and, in some cases, deleterious voltage transients. The tests identified the need for more effective controls, if FPSE/LAs are to be used for stand-alone power systems. The tests also generated a large body of transient dynamic data useful for analysis code validation.

Sub-synchronous resonance damping using high penetration PV plant

NASA Astrophysics Data System (ADS)

Khayyatzadeh, M.; Kazemzadeh, R.

2017-02-01

The growing need to the clean and renewable energy has led to the fast development of transmission voltage-level photovoltaic (PV) plants all over the world. These large scale PV plants are going to be connected to power systems and one of the important subjects that should be investigated is the impact of these plants on the power system stability. Can large scale PV plants help to damp sub-synchronous resonance (SSR) and how? In this paper, this capability of a large scale PV plant is investigated. The IEEE Second Benchmark Model aggregated with a PV plant is utilized as the case study. A Wide Area Measurement System (WAMS) based conventional damping controller is designed and added to the main control loop of PV plant in order to damp the SSR and also investigation of the destructive effect of time delay in remote feedback signal. A new optimization algorithm called teaching-learning-based-optimization (TLBO) algorithm has been used for managing the optimization problems. Fast Furrier Transformer (FFT) analysis and also transient simulations of detailed nonlinear system are considered to investigate the performance of the controller. Robustness of the proposed system has been analyzed by facing the system with disturbances leading to significant changes in generator and power system operating point, fault duration time and PV plant generated power. All the simulations are carried out in MATLAB/SIMULINK environment.

HIGH-FIDELITY SIMULATION-DRIVEN MODEL DEVELOPMENT FOR COARSE-GRAINED COMPUTATIONAL FLUID DYNAMICS

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

Hanna, Botros N.; Dinh, Nam T.; Bolotnov, Igor A.

Nuclear reactor safety analysis requires identifying various credible accident scenarios and determining their consequences. For a full-scale nuclear power plant system behavior, it is impossible to obtain sufficient experimental data for a broad range of risk-significant accident scenarios. In single-phase flow convective problems, Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) can provide us with high fidelity results when physical data are unavailable. However, these methods are computationally expensive and cannot be afforded for simulation of long transient scenarios in nuclear accidents despite extraordinary advances in high performance scientific computing over the past decades. The major issue is themore » inability to make the transient computation parallel, thus making number of time steps required in high-fidelity methods unaffordable for long transients. In this work, we propose to apply a high fidelity simulation-driven approach to model sub-grid scale (SGS) effect in Coarse Grained Computational Fluid Dynamics CG-CFD. This approach aims to develop a statistical surrogate model instead of the deterministic SGS model. We chose to start with a turbulent natural convection case with volumetric heating in a horizontal fluid layer with a rigid, insulated lower boundary and isothermal (cold) upper boundary. This scenario of unstable stratification is relevant to turbulent natural convection in a molten corium pool during a severe nuclear reactor accident, as well as in containment mixing and passive cooling. The presented approach demonstrates how to create a correction for the CG-CFD solution by modifying the energy balance equation. A global correction for the temperature equation proves to achieve a significant improvement to the prediction of steady state temperature distribution through the fluid layer.« less

Plasmoid formation in the elongated current sheet during transient CHI on HIST

NASA Astrophysics Data System (ADS)

Nagata, Masayoshi; Fujita, Akihiro; Matsui, Takahiro; Kikuchi, Yusuke; Fukumoto, Naoyuki; Kanki, Takashi

2016-10-01

The Transient-Coaxial Helicity Injection (T-CHI) is a promising candidate for the non-inductive plasma start-up on Spherical Torus (ST). The problem of the flux closure in the T-CHI is important and related to understand the physics of fast magnetic reconnection. The recent MHD simulation (F. Ebrahimi and R. Raman, Phys. Rev. Lett. 114, 205003 (2015)) on T-CHI for NSTX predicts the formation and breakup of an elongated Sweet-Parker (S-P) current sheet and a transient to plasmoid instability. According to this simulation, the reconnection rate based on the plasmoid instability is faster than that by S-P model and becomes nearly independent of the Lundquist number S. In this meeting, we will present that the formation of multiple X-points and plasmoids has been observed in T-CHI start-up plasmas on HIST. The stronger external guide (toroidal) magnetic field makes plasma less compressible, leading to slower reconnection time and longer current sheet. The experimental observation shows that 2/3 plasmoids are generated in the elongated current sheet with the narrow width comparable to the ion skin depth or the ion sound gyro-radius. The small plasmoids develop to a large-scale flux structure due to a current inward diffusion during the decay phase.

An investigation on die crack detection using Temperature Sensitive Parameter for high speed LED mass production

NASA Astrophysics Data System (ADS)

Annaniah, Luruthudass; Devarajan, Mutharasu; San, Teoh Kok

To ensure the highest quality & long-term reliability of LED components it is necessary to examine LED dice that have sustained mechanical damage during the manufacturing process. This paper has demonstrated that detection of die crack in mass manufactured LEDs can be achieved by measuring Temperature Sensitive Parameters (TSPs) during final testing. A newly-designed apparatus and microcontroller was used for this investigation in order to achieve the millisecond switching time needed for detecting thermal transient effects and at the same time meet the expected speed for mass manufacturing. Evaluations conducted at lab scale shows that thermal transient behaviour of cracked die is significantly different than that of an undamaged die. Having an established test limits to differentiate cracked dice, large volume tests in a production environment were used to confirm the effectiveness of this test method. Failure Bin Analysis (FBA) of this high volume experiment confirmed that all the cracked die LEDs were detected and the undamaged LEDs passed this test without over-rejection. The work verifies that tests based on TSP are effective in identifying die cracks and it is believed that the method could be extended to other types of rejects that have thermal transient signatures such as die delamination.

Adaptive polynomial chaos techniques for uncertainty quantification of a gas cooled fast reactor transient

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

Perko, Z.; Gilli, L.; Lathouwers, D.

2013-07-01

Uncertainty quantification plays an increasingly important role in the nuclear community, especially with the rise of Best Estimate Plus Uncertainty methodologies. Sensitivity analysis, surrogate models, Monte Carlo sampling and several other techniques can be used to propagate input uncertainties. In recent years however polynomial chaos expansion has become a popular alternative providing high accuracy at affordable computational cost. This paper presents such polynomial chaos (PC) methods using adaptive sparse grids and adaptive basis set construction, together with an application to a Gas Cooled Fast Reactor transient. Comparison is made between a new sparse grid algorithm and the traditionally used techniquemore » proposed by Gerstner. An adaptive basis construction method is also introduced and is proved to be advantageous both from an accuracy and a computational point of view. As a demonstration the uncertainty quantification of a 50% loss of flow transient in the GFR2400 Gas Cooled Fast Reactor design was performed using the CATHARE code system. The results are compared to direct Monte Carlo sampling and show the superior convergence and high accuracy of the polynomial chaos expansion. Since PC techniques are easy to implement, they can offer an attractive alternative to traditional techniques for the uncertainty quantification of large scale problems. (authors)« less

Long-Lasting Crossmodal Cortical Reorganization Triggered by Brief Postnatal Visual Deprivation.

PubMed

Collignon, Olivier; Dormal, Giulia; de Heering, Adelaide; Lepore, Franco; Lewis, Terri L; Maurer, Daphne

2015-09-21

Animal and human studies have demonstrated that transient visual deprivation early in life, even for a very short period, permanently alters the response properties of neurons in the visual cortex and leads to corresponding behavioral visual deficits. While it is acknowledged that early-onset and longstanding blindness leads the occipital cortex to respond to non-visual stimulation, it remains unknown whether a short and transient period of postnatal visual deprivation is sufficient to trigger crossmodal reorganization that persists after years of visual experience. In the present study, we characterized brain responses to auditory stimuli in 11 adults who had been deprived of all patterned vision at birth by congenital cataracts in both eyes until they were treated at 9 to 238 days of age. When compared to controls with typical visual experience, the cataract-reversal group showed enhanced auditory-driven activity in focal visual regions. A combination of dynamic causal modeling with Bayesian model selection indicated that this auditory-driven activity in the occipital cortex was better explained by direct cortico-cortical connections with the primary auditory cortex than by subcortical connections. Thus, a short and transient period of visual deprivation early in life leads to enduring large-scale crossmodal reorganization of the brain circuitry typically dedicated to vision. Copyright © 2015 Elsevier Ltd. All rights reserved.

Assessing the capability of different satellite observing configurations to resolve the distribution of methane emissions at kilometer scales

NASA Astrophysics Data System (ADS)

Turner, Alexander J.; Jacob, Daniel J.; Benmergui, Joshua; Brandman, Jeremy; White, Laurent; Randles, Cynthia A.

2018-06-01

Anthropogenic methane emissions originate from a large number of fine-scale and often transient point sources. Satellite observations of atmospheric methane columns are an attractive approach for monitoring these emissions but have limitations from instrument precision, pixel resolution, and measurement frequency. Dense observations will soon be available in both low-Earth and geostationary orbits, but the extent to which they can provide fine-scale information on methane sources has yet to be explored. Here we present an observation system simulation experiment (OSSE) to assess the capabilities of different satellite observing system configurations. We conduct a 1-week WRF-STILT simulation to generate methane column footprints at 1.3 × 1.3 km2 spatial resolution and hourly temporal resolution over a 290 × 235 km2 domain in the Barnett Shale, a major oil and gas field in Texas with a large number of point sources. We sub-sample these footprints to match the observing characteristics of the recently launched TROPOMI instrument (7 × 7 km2 pixels, 11 ppb precision, daily frequency), the planned GeoCARB instrument (2.7 × 3.0 km2 pixels, 4 ppb precision, nominal twice-daily frequency), and other proposed observing configurations. The information content of the various observing systems is evaluated using the Fisher information matrix and its eigenvalues. We find that a week of TROPOMI observations should provide information on temporally invariant emissions at ˜ 30 km spatial resolution. GeoCARB should provide information available on temporally invariant emissions ˜ 2-7 km spatial resolution depending on sampling frequency (hourly to daily). Improvements to the instrument precision yield greater increases in information content than improved sampling frequency. A precision better than 6 ppb is critical for GeoCARB to achieve fine resolution of emissions. Transient emissions would be missed with either TROPOMI or GeoCARB. An aspirational high-resolution geostationary instrument with 1.3 × 1.3 km2 pixel resolution, hourly return time, and 1 ppb precision would effectively constrain the temporally invariant emissions in the Barnett Shale at the kilometer scale and provide some information on hourly variability of sources.

Liverpool telescope 2: a new robotic facility for rapid transient follow-up

NASA Astrophysics Data System (ADS)

Copperwheat, C. M.; Steele, I. A.; Barnsley, R. M.; Bates, S. D.; Bersier, D.; Bode, M. F.; Carter, D.; Clay, N. R.; Collins, C. A.; Darnley, M. J.; Davis, C. J.; Gutierrez, C. M.; Harman, D. J.; James, P. A.; Knapen, J. H.; Kobayashi, S.; Marchant, J. M.; Mazzali, P. A.; Mottram, C. J.; Mundell, C. G.; Newsam, A.; Oscoz, A.; Palle, E.; Piascik, A.; Rebolo, R.; Smith, R. J.

2015-03-01

The Liverpool Telescope is one of the world's premier facilities for time domain astronomy. The time domain landscape is set to radically change in the coming decade, with synoptic all-sky surveys such as LSST providing huge numbers of transient detections on a nightly basis; transient detections across the electromagnetic spectrum from other major facilities such as SVOM, SKA and CTA; and the era of `multi-messenger astronomy', wherein astrophysical events are detected via non-electromagnetic means, such as neutrino or gravitational wave emission. We describe here our plans for the Liverpool Telescope 2: a new robotic telescope designed to capitalise on this new era of time domain astronomy. LT2 will be a 4-metre class facility co-located with the Liverpool Telescope at the Observatorio del Roque de Los Muchachos on the Canary island of La Palma. The telescope will be designed for extremely rapid response: the aim is that the telescope will take data within 30 seconds of the receipt of a trigger from another facility. The motivation for this is twofold: firstly it will make it a world-leading facility for the study of fast fading transients and explosive phenomena discovered at early times. Secondly, it will enable large-scale programmes of low-to-intermediate resolution spectral classification of transients to be performed with great efficiency. In the target-rich environment of the LSST era, minimising acquisition overheads will be key to maximising the science gains from any follow-up programme. The telescope will have a diverse instrument suite which is simultaneously mounted for automatic changes, but it is envisaged that the primary instrument will be an intermediate resolution, optical/infrared spectrograph for scientific exploitation of transients discovered with the next generation of synoptic survey facilities. In this paper we outline the core science drivers for the telescope, and the requirements for the optical and mechanical design.

Solar and interplanetary dynamics; Proceedings of the Symposium, Harvard University, Cambridge, Mass., August 27-31, 1979

NASA Technical Reports Server (NTRS)

Dryer, M. (Editor); Tandberg-Hanssen, E.

1980-01-01

The symposium focuses on solar phenomena as the source of transient events propagating through the solar system, and theoretical and observational assessments of the dynamic processes involved in these events. The topics discussed include the life history of coronal structures and fields, coronal and interplanetary responses to long time scale phenomena, solar transient phenomena affecting the corona and interplanetary medium, coronal and interplanetary responses to short time scale phenomena, and future directions.

The temporal scaling of Caenorhabditis elegans ageing.

PubMed

Stroustrup, Nicholas; Anthony, Winston E; Nash, Zachary M; Gowda, Vivek; Gomez, Adam; López-Moyado, Isaac F; Apfeld, Javier; Fontana, Walter

2016-02-04

The process of ageing makes death increasingly likely, involving a random aspect that produces a wide distribution of lifespan even in homogeneous populations. The study of this stochastic behaviour may link molecular mechanisms to the ageing process that determines lifespan. Here, by collecting high-precision mortality statistics from large populations, we observe that interventions as diverse as changes in diet, temperature, exposure to oxidative stress, and disruption of genes including the heat shock factor hsf-1, the hypoxia-inducible factor hif-1, and the insulin/IGF-1 pathway components daf-2, age-1, and daf-16 all alter lifespan distributions by an apparent stretching or shrinking of time. To produce such temporal scaling, each intervention must alter to the same extent throughout adult life all physiological determinants of the risk of death. Organismic ageing in Caenorhabditis elegans therefore appears to involve aspects of physiology that respond in concert to a diverse set of interventions. In this way, temporal scaling identifies a novel state variable, r(t), that governs the risk of death and whose average decay dynamics involves a single effective rate constant of ageing, kr. Interventions that produce temporal scaling influence lifespan exclusively by altering kr. Such interventions, when applied transiently even in early adulthood, temporarily alter kr with an attendant transient increase or decrease in the rate of change in r and a permanent effect on remaining lifespan. The existence of an organismal ageing dynamics that is invariant across genetic and environmental contexts provides the basis for a new, quantitative framework for evaluating the manner and extent to which specific molecular processes contribute to the aspect of ageing that determines lifespan.

The temporal scaling of Caenorhabditis elegans ageing

NASA Astrophysics Data System (ADS)

Stroustrup, Nicholas; Anthony, Winston E.; Nash, Zachary M.; Gowda, Vivek; Gomez, Adam; López-Moyado, Isaac F.; Apfeld, Javier; Fontana, Walter

2016-02-01

The process of ageing makes death increasingly likely, involving a random aspect that produces a wide distribution of lifespan even in homogeneous populations. The study of this stochastic behaviour may link molecular mechanisms to the ageing process that determines lifespan. Here, by collecting high-precision mortality statistics from large populations, we observe that interventions as diverse as changes in diet, temperature, exposure to oxidative stress, and disruption of genes including the heat shock factor hsf-1, the hypoxia-inducible factor hif-1, and the insulin/IGF-1 pathway components daf-2, age-1, and daf-16 all alter lifespan distributions by an apparent stretching or shrinking of time. To produce such temporal scaling, each intervention must alter to the same extent throughout adult life all physiological determinants of the risk of death. Organismic ageing in Caenorhabditis elegans therefore appears to involve aspects of physiology that respond in concert to a diverse set of interventions. In this way, temporal scaling identifies a novel state variable, r(t), that governs the risk of death and whose average decay dynamics involves a single effective rate constant of ageing, kr. Interventions that produce temporal scaling influence lifespan exclusively by altering kr. Such interventions, when applied transiently even in early adulthood, temporarily alter kr with an attendant transient increase or decrease in the rate of change in r and a permanent effect on remaining lifespan. The existence of an organismal ageing dynamics that is invariant across genetic and environmental contexts provides the basis for a new, quantitative framework for evaluating the manner and extent to which specific molecular processes contribute to the aspect of ageing that determines lifespan.

The temporal scaling of Caenorhabditis elegans ageing

PubMed Central

Stroustrup, Nicholas; Anthony, Winston E.; Nash, Zachary M.; Gowda, Vivek; Gomez, Adam; López-Moyado, Isaac F.; Apfeld, Javier; Fontana, Walter

2016-01-01

The process of ageing makes death increasingly likely, but involves a random aspect that produces a wide distribution of lifespan even in homogeneous populations1,2. The study of this stochastic behaviour may link molecular mechanisms to the ageing process that determines lifespan. Here, by collecting high-precision mortality statistics from large populations, we observe that interventions as diverse as changes in diet, temperature, exposure to oxidative stress, and disruption of genes including the heat shock factor hsf-1, the hypoxia-inducible factor hif-1, and the insulin/IGF-1 pathway components daf-2, age-1, and daf-16 all alter lifespan distributions by an apparent stretching or shrinking of time. To produce such temporal scaling, each intervention must alter to the same extent throughout adult life all physiological determinants of the risk of death. Organismic ageing in Caenorhabditis elegans therefore appears to involve aspects of physiology that respond in concert to a diverse set of interventions. In this way, temporal scaling identifies a novel state variable, r(t), that governs the risk of death and whose average decay dynamics involves a single effective rate constant of ageing, kr. Interventions that produce temporal scaling influence lifespan exclusively by altering kr. Such interventions, when applied transiently even in early adulthood, temporarily alter kr with an attendant transient increase or decrease in the rate of change in r and a permanent effect on remaining lifespan. The existence of an organismal ageing dynamics that is invariant across genetic and environmental contexts provides the basis for a new, quantitative framework for evaluating how and how much specific molecular processes contribute to the aspect of ageing that determines lifespan. PMID:26814965

Geometry of a large-scale, low-angle, midcrustal thrust (Woodroffe Thrust, central Australia)

NASA Astrophysics Data System (ADS)

Wex, S.; Mancktelow, N. S.; Hawemann, F.; Camacho, A.; Pennacchioni, G.

2017-11-01

The Musgrave Block in central Australia exposes numerous large-scale mylonitic shear zones developed during the intracontinental Petermann Orogeny around 560-520 Ma. The most prominent structure is the crustal-scale, over 600 km long, E-W trending Woodroffe Thrust, which is broadly undulate but generally dips shallowly to moderately to the south and shows an approximately top-to-north sense of movement. The estimated metamorphic conditions of mylonitization indicate a regional variation from predominantly midcrustal (circa 520-620°C and 0.8-1.1 GPa) to lower crustal ( 650°C and 1.0-1.3 GPa) levels in the direction of thrusting, which is also reflected in the distribution of preserved deformation microstructures. This variation in metamorphic conditions is consistent with a south dipping thrust plane but is only small, implying that a ≥60 km long N-S segment of the Woodroffe Thrust was originally shallowly dipping at an average estimated angle of ≤6°. The reconstructed geometry suggests that basement-cored, thick-skinned, midcrustal thrusts can be very shallowly dipping on a scale of many tens of kilometers in the direction of movement. Such a geometry would require the rocks along the thrust to be weak, but field observations (e.g., large volumes of syntectonic pseudotachylyte) argue for a strong behavior, at least transiently. Localization on a low-angle, near-planar structure that crosscuts lithological layers requires a weak precursor, such as a seismic rupture in the middle to lower crust. If this was a single event, the intracontinental earthquake must have been large, with the rupture extending laterally over hundreds of kilometers.

Antipodal Magnetic Anomalies on the Moon, Contributions from Impact Induced Currents Due to Positive Holes and Flexoelectric Phenomina and Dynamo

NASA Technical Reports Server (NTRS)

Kletetschka, G.; Freund, F.; Wasilewski, P. J.; Mikula, V.; Kohout, Tomas

2005-01-01

Large impacts on the Moon generate large pressure pulses that penetrate the whole body. Several of these large impacts may have generated antipodal structure with anomalous magnetic intensity.These regions can be more than a thousand km across, with fields of the order of tens to hundreds of nT. This is the case of Orientale, Imbrium, Serenitatis, Crisium, and Nectaris impact basins. The production of large-scale magnetic fields and associated crustal magnetization due to lunar basin-forming impacts was hypothesized to have an origin in fields external to the impact plasma cloud that are produced by the magnetohydrodynamic interaction of the cloud with ambient magnetic fields and plasmas. During the period of compressed antipodal field amplification, seismic compressional waves from the impact converge at the antipode resulting in transient shock pressures that reach 2 GPa (20 kbar). This can produce conditions for shock magnetic acquisition of the crust antipodal to impact basins.

Single polymer dynamics in semi-dilute unentangled and entangled solutions: from molecular conformation to normal stress

NASA Astrophysics Data System (ADS)

Schroeder, Charles

Semi-dilute polymer solutions are encountered in a wide array of applications such as advanced 3D printing technologies. Semi-dilute solutions are characterized by large fluctuations in concentration, such that hydrodynamic interactions, excluded volume interactions, and transient chain entanglements may be important, which greatly complicates analytical modeling and theoretical treatment. Despite recent progress, we still lack a complete molecular-level understanding of polymer dynamics in these systems. In this talk, I will discuss three recent projects in my group to study semi-dilute solutions that focus on single molecule studies of linear and ring polymers and a new method to measure normal stresses in microfluidic devices based on the Stokes trap. In the first effort, we use single polymer techniques to investigate the dynamics of semi-dilute unentangled and semi-dilute entangled DNA solutions in extensional flow, including polymer relaxation from high stretch, transient stretching dynamics in step-strain experiments, and steady-state stretching in flow. In the semi-dilute unentangled regime, our results show a power-law scaling of the longest polymer relaxation time that is consistent with scaling arguments based on the double cross-over regime. Upon increasing concentration, we observe a transition region in dynamics to the entangled regime. We also studied the transient and steady-state stretching dynamics in extensional flow using the Stokes trap, and our results show a decrease in transient polymer stretch and a milder coil-to-stretch transition for semi-dilute polymer solutions compared to dilute solutions, which is interpreted in the context of a critical Weissenberg number Wi at the coil-to-stretch transition. Interestingly, we observe a unique set of polymer conformations in semi-dilute unentangled solutions that are highly suggestive of transient topological entanglements in solutions that are nominally unentangled at equilibrium. Taken together, these results suggest that the transient stretching pathways in semi-dilute solution extensional flows are qualitatively different than for both dilute solutions and for semi-dilute solutions in shear flow. In a second effort, we studied the dynamics of ring polymers in background solutions of semi-dilute linear polymers. Interestingly, we observe strikingly large fluctuations in steady-state polymer extension for ring polymers in flow, which occurs due to the interplay between polymer topology and concentration leading to chain `threading' in flow. In a third effort, we developed a new microfluidic method to measure normal stress and extensional viscosity that can be loosely described as passive yet non-linear microrheology. In particular, we incorporated 3-D particle imaging velocimetry (PIV) with the Stokes trap to study extensional flow-induced particle migration in semi-dilute polymer solutions. Experimental results are analyzed using the framework of a second-order-fluid model, which allows for measurement of normal stress and extensional viscosity in semi-dilute polymer solutions, all of which is a first-of-its-kind demonstration. Microfluidic measurements of extensional viscosity are directly compared to the dripping-onto-substrate or DOS method, and good agreement is generally observed. Overall, our work aims to provide a molecular-level understanding of the role of polymer topology and concentration on bulk rheological properties by using single polymer techniques.

Multi-Scale Observation of Time-Variable Interactions of a Stream and its Valley Bottom During a Storm Event

NASA Astrophysics Data System (ADS)

Hixson, J.; Ward, A. S.; Schmadel, N.

2015-12-01

The exchange of water and solutes across the stream-hyporheic-riparian-hillslope continuum is controlled by the interaction of dynamic hydrological processes with the underlying geological setting. Our current understanding of exchange processes is primarily based on field observations collected during baseflow conditions, with few studies considering time-variable stream-aquifer interactions during storm events. We completed ten sets of four in-stream tracer slug injections during and after a large storm event in a headwater catchment at the H.J. Andrews Experimental Forest, Oregon. The injections were performed in three adjacent 50-meter study reaches, enabling comparison of spatial heterogeneity in transport processes. Reach-scale data demonstrate apparent trends with discharge in both transient storage and long-term storage (commonly "channel water balance"). Comparison of flowpath-scale observations from a network of monitoring wells to reach-scale observations showed that the advective timescale changed with discharge making it difficult to infer process from simple, reach-scale tracer studies. Overall, our results highlight the opportunities and challenges for interpretation of multi-scale solute tracer data along the stream-hyporheic-riparian-hillslope continuum.

Transient numerical model of magma ascent dynamics: application to the explosive eruptions at the Soufrière Hills Volcano

NASA Astrophysics Data System (ADS)

La Spina, G.; de'Michieli Vitturi, M.; Clarke, A. B.

2017-04-01

Volcanic activity exhibits a wide range of eruption styles, from relatively slow effusive eruptions that produce lava flows and lava domes, to explosive eruptions that can inject large volumes of fragmented magma and volcanic gases high into the atmosphere. Although controls on eruption style and scale are not fully understood, previous research suggests that the dynamics of magma ascent in the shallow subsurface (< 10 km depth) may in part control the transition from effusive to explosive eruption and variations in eruption style and scale. Here we investigate the initial stages of explosive eruptions using a 1D transient model for magma ascent through a conduit based on the theory of the thermodynamically compatible systems. The model is novel in that it implements finite rates of volatile exsolution and velocity and pressure relaxation between the phases. We validate the model against a simple two-phase Riemann problem, the Air-Water Shock Tube problem, which contains strong shock and rarefaction waves. We then use the model to explore the role of the aforementioned finite rates in controlling eruption style and duration, within the context of two types of eruptions at the Soufrière Hills Volcano, Montserrat: Vulcanian and sub-Plinian eruptions. Exsolution, pressure, and velocity relaxation rates all appear to exert important controls on eruption duration. More significantly, however, a single finite exsolution rate characteristic of the Soufrière Hills magma composition is able to produce both end-member eruption durations observed in nature. The duration therefore appears to be largely controlled by the timescales available for exsolution, which depend on dynamic processes such as ascent rate and fragmentation wave speed.

Transient and residual stresses in large castings, taking time effects into account

NASA Astrophysics Data System (ADS)

Thorborg, J.; Klinkhammer, J.; Heitzer, M.

2012-07-01

Casting of large scale steel and iron parts leads to long solidification and cooling times. Solid mechanical calculations for these castings have to take the time scale of the process into account, in order to predict the transient and residual stress levels with a reasonable accuracy. This paper presents a study on the modelling of the thermo-mechanical conditions in the cast material using a unified approach to describe the constitutive behaviour. This means a classical splitting of the mechanical strain into an elastic and an inelastic contribution, where the inelastic strain is only formulated in the deviatoric space in terms of the J2 invariant. At high temperatures, creep is pronounced. Since the cooling time is long, the model includes a type of Norton's power law to integrate the significant contribution of creep to the inelastic strains. At these temperature levels, annealing effects are also dominant and hence no hardening is modelled. However, at intermediate and lower temperature levels, hardening is more pronounced and isotropic hardening is considered. Different hardening models have been studied and selected based on their ability to describe the behaviour at the different temperature levels. At the lower temperature levels, time effects decrease and the formulation reduces to a time independent formulation, like classical J2-flow theory. Several tensile and creep experiments have been made at different temperature levels to provide input data for selecting the appropriate contributions to the material model. The measurements have furthermore been used as input for extracting material data for the model. The numerical model is applied on different industrial examples to verify the agreement between measured and calculated deformations.

Transient Stability and Frequency Response of the US Western Interconnection Under Conditions of High Wind and Solar Generation

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

Miller, Nicholas W.; Shao, Miaolei; Pajic, Slobodan

The addition of large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. This paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrationsmore » of wind and solar generation. The main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.« less

Transient Stability and Frequency Response of the Us Western Interconnection Under Conditions of High Wind and Solar Generation

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

Clark, Kara; Miller, Nicholas W.; Shao, Miaolei

Adding large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. Our paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrations of windmore » and solar generation. Moreover, the main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.« less

Transients in the synchronization of asymmetrically coupled oscillator arrays

NASA Astrophysics Data System (ADS)

Cantos, C. E.; Hammond, D. K.; Veerman, J. J. P.

2016-09-01

We consider the transient behavior of a large linear array of coupled linear damped harmonic oscillators following perturbation of a single element. Our work is motivated by modeling the behavior of flocks of autonomous vehicles. We first state a number of conjectures that allow us to derive an explicit characterization of the transients, within a certain parameter regime Ω. As corollaries we show that minimizing the transients requires considering non-symmetric coupling, and that within Ω the computed linear growth in N of the transients is independent of (reasonable) boundary conditions.

Transient synchrony among populations of five foliage-feeding Lepidoptera

Treesearch

Maartje J. Klapwijk; Jonathan A. Walter; Anikó Hirka; György Csóka; Christer Björkman; Andrew M. Liebhold

2018-01-01

Studies of transient population dynamics have largely focused on temporal changes in dynamical behaviour, such as the transition between periods of stability and instability. This study explores a related dynamic pattern, namely transient synchrony during a 49-year period among populations of five sympatric species of forest insects that share host tree resources. The...

Imaging the distribution of transient viscosity after the 2016 Mw 7.1 Kumamoto earthquake.

PubMed

Moore, James D P; Yu, Hang; Tang, Chi-Hsien; Wang, Teng; Barbot, Sylvain; Peng, Dongju; Masuti, Sagar; Dauwels, Justin; Hsu, Ya-Ju; Lambert, Valère; Nanjundiah, Priyamvada; Wei, Shengji; Lindsey, Eric; Feng, Lujia; Shibazaki, Bunichiro

2017-04-14

The deformation of mantle and crustal rocks in response to stress plays a crucial role in the distribution of seismic and volcanic hazards, controlling tectonic processes ranging from continental drift to earthquake triggering. However, the spatial variation of these dynamic properties is poorly understood as they are difficult to measure. We exploited the large stress perturbation incurred by the 2016 earthquake sequence in Kumamoto, Japan, to directly image localized and distributed deformation. The earthquakes illuminated distinct regions of low effective viscosity in the lower crust, notably beneath the Mount Aso and Mount Kuju volcanoes, surrounded by larger-scale variations of viscosity across the back-arc. This study demonstrates a new potential for geodesy to directly probe rock rheology in situ across many spatial and temporal scales. Copyright © 2017, American Association for the Advancement of Science.

Slow dynamics in translation-invariant quantum lattice models

NASA Astrophysics Data System (ADS)

Michailidis, Alexios A.; Žnidarič, Marko; Medvedyeva, Mariya; Abanin, Dmitry A.; Prosen, Tomaž; Papić, Z.

2018-03-01

Many-body quantum systems typically display fast dynamics and ballistic spreading of information. Here we address the open problem of how slow the dynamics can be after a generic breaking of integrability by local interactions. We develop a method based on degenerate perturbation theory that reveals slow dynamical regimes and delocalization processes in general translation invariant models, along with accurate estimates of their delocalization time scales. Our results shed light on the fundamental questions of the robustness of quantum integrable systems and the possibility of many-body localization without disorder. As an example, we construct a large class of one-dimensional lattice models where, despite the absence of asymptotic localization, the transient dynamics is exceptionally slow, i.e., the dynamics is indistinguishable from that of many-body localized systems for the system sizes and time scales accessible in experiments and numerical simulations.

Exploring the Hot and Energetic Universe: The first scientific conference dedicated to the Athena X-ray observatory

NASA Astrophysics Data System (ADS)

Ehle, Matthias

2015-09-01

The Advanced Telescope for High Energy Astrophysics (Athena) is a large-class mission of the European Space Agency (ESA). It is currently entering an assessment study phase, with launch planned for 2028. Athena has been designed to address the science theme "The Hot and Energetic Universe", which poses two key questions: - How does ordinary matter assemble into the large-scale structures we see today? - How do black holes grow and influence the Universe? The mission will employ a variety of techniques to address these topics in a comprehensive matter, including spatially-resolved high resolution spectroscopy, sensitive wide field imaging, high throughput spectral-timing, and fast follow-up of transient phenomena. The purpose of this conference is to gather together all members of the astronomical community worldwide who have an interest in Athena. The main focus of the meeting is to discuss the key science questions which will be addressed by the mission. A significant portion of the programme is devoted to presenting the status of the project and discussing the synergies with other future large multi-wavelength facilities and missions. Scientific topics include: - Formation, evolution and physical properties of clusters of galaxies - Cosmic feedback - The missing baryons and the WHIM - Supermassive black hole evolution - Accretion physics and strong gravity - High energy transient phenomena - Solar system and exoplanets - Star formation and evolution - The physics of compact object - Supernovae, supernova remnants and the ISM - Multiwavelength synergies

Temperature-dependent daily variability of precipitable water in special sensor microwave/imager observations

NASA Technical Reports Server (NTRS)

Gutowski, William J.; Lindemulder, Elizabeth A.; Jovaag, Kari

1995-01-01

We use retrievals of atmospheric precipitable water from satellite microwave observations and analyses of near-surface temperature to examine the relationship between these two fields on daily and longer time scales. The retrieval technique producing the data used here is most effective over the open ocean, so the analysis focuses on the southern hemisphere's extratropics, which have an extensive ocean surface. For both the total and the eddy precipitable water fields, there is a close correspondence between local variations in the precipitable water and near-surface temperature. The correspondence appears particularly strong for synoptic and planetary scale transient eddies. More specifically, the results support a typical modeling assumption that transient eddy moisture fields are proportional to transient eddy temperature fields under the assumption f constant relative humidity.

RISPERIDONE VERSUS HALOPERIDOL IN ACUTE AND TRANSIENT PSYCHOTIC DISORDER

PubMed Central

Chaudhuri, Bijoy Pratim; Bhagabati, Dipesh; Medhi, Dipanjali

2000-01-01

The mechanism of action of a relatively new antipsychotic drug-Risperidone differs from conventional antipsychotics like Haloperidol. We compared low dosages of Risperidone with near equivalent dosages of Haloperidol in first episode drug naive Acute and Transient Psychotic disorder. A single blind randomised four-week study protocol was employed. Highly significant and comparable efficacy as assessed by Brief Psychiatric Rating Scale and Global Assessment of Functioning Scale was seen at the end of the Study protocol in both the groups. Risperidone had significantly, an early onset of action on some of the positive as well as negative symptoms with less incidence of Extrapyramidal Symptoms in comparison to Haloperidol. We conclude that Risperidone may represent a potential useful first line agent in the treatment of Acute and Transient Psychotic Disorder. PMID:21407958

Investigation of natural circulation instability and transients in passively safe novel modular reactor

NASA Astrophysics Data System (ADS)

Shi, Shanbin

The Purdue Novel Modular Reactor (NMR) is a new type small modular reactor (SMR) that belongs to the design of boiling water reactor (BWR). Specifically, the NMR is one third the height and area of a conventional BWR reactor pressure vessel (RPV) with an electric output of 50 MWe. The fuel cycle length of the NMR-50 is extended up to 10 years due to optimized neutronics design. The NMR-50 is designed with double passive engineering safety system. However, natural circulation BWRs (NCBWR) could experience certain operational difficulties due to flow instabilities that occur at low pressure and low power conditions. Static instabilities (i.e. flow excursion (Ledinegg) instability and flow pattern transition instability) and dynamic instabilities (i.e. density wave instability and flashing/condensation instability) pose a significant challenge in two-phase natural circulation systems. In order to experimentally study the natural circulation flow instability, a proper scaling methodology is needed to build a reduced-size test facility. The scaling analysis of the NMR uses a three-level scaling method, which was developed and applied for the design of the Purdue Multi-dimensional Integral Test Assembly (PUMA). Scaling criteria is derived from dimensionless field equations and constitutive equations. The scaling process is validated by the RELAP5 analysis for both steady state and startup transients. A new well-scaled natural circulation test facility is designed and constructed based on the scaling analysis of the NMR-50. The experimental facility is installed with different equipment to measure various thermal-hydraulic parameters such as pressure, temperature, mass flow rate and void fraction. Characterization tests are performed before the startup transient tests and quasi-steady tests to determine the loop flow resistance. The controlling system and data acquisition system are programmed with LabVIEW to realize the real-time control and data storage. The thermal-hydraulic and nuclear coupled startup transients are performed to investigate the flow instabilities at low pressure and low power conditions. Two different power ramps are chosen to study the effect of power density on the flow instability. The experimental startup transient tests show the existence of three different flow instability mechanisms during the low pressure startup transients, i.e., flashing instability, condensation induced instability, and density wave oscillations. Flashing instability in the chimney section of the test loop and density wave oscillation are the main flow instabilities observed when the system pressure is below 0.5 MPa. They show completely different type of oscillations, i.e., intermittent oscillation and sinusoidal oscillation, in void fraction profile during the startup transients. In order to perform nuclear-coupled startup transients with void reactivity feedback, the Point Kinetics model is utilized to calculate the transient power during the startup transients. In addition, the differences between the electric resistance heaters and typical fuel element are taken into account. The reactor power calculated shows some oscillations due to flashing instability during the transients. However, the void reactivity feedback does not have significant influence on the flow instability during the startup procedure for the NMR-50. Further investigation of very small power ramp on the startup transients is carried out for the thermal-hydraulic startup transients. It is found that very small power density can eliminate the flashing oscillation in the single phase natural circulation and stabilize the flow oscillations in the phase of net vapor generation. Furthermore, initially pressurized startup procedure is investigated to eliminate the main flow instabilities. The results show that the pressurized startup procedure can suppress the flashing instability at low pressure and low power conditions. In order to have a deep understanding of natural circulation flow instability, the quasi-steady tests are performed using the test facility installed with preheater and subcooler. The effects of system pressure, core inlet subcooling, core power density, inlet flow resistance coefficient, and void reactivity feedback are investigated in the quasi-steady state tests. The stability boundaries are determined between unstable and stable flow conditions in the dimensionless stability plane of inlet subcooling number and Zuber number. In order to predict the stability boundary theoretically, linear stability analysis in the frequency domain is performed at four sections of the loop. The flashing in the chimney is considered as an axially uniform heat source. The dimensionless characteristic equation of the pressure drop perturbation is obtained by considering the void fraction effect and outlet flow resistance in the chimney section. The flashing boundary shows some discrepancies with previous experimental data from the quasi-steady state tests. In the future, thermal non-equilibrium is recommended to improve the accuracy of flashing instability boundary.

A SEARCH FOR RAPIDLY SPINNING PULSARS AND FAST TRANSIENTS IN UNIDENTIFIED RADIO SOURCES WITH THE NRAO 43 METER TELESCOPE

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

Schmidt, Deborah; Crawford, Fronefield; Gilpin, Claire

2013-04-15

We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g., sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications formore » models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a different epoch with a new 800 MHz backend on the NRAO 43 m Telescope at a center frequency of 1200 MHz. Our search was sensitive to sub-millisecond pulsars in highly accelerated binary systems and to short transient pulses. No periodic or transient signals were detected from any of the target sources. We conclude that diffractive scintillation, dispersive smearing, and binary acceleration are unlikely to have prevented detection of the large majority of the sources if they are pulsars, though we cannot rule out eclipsing, nulling or intermittent emission, or radio interference as possible factors for some non-detections. Other (speculative) possibilities for what these sources might include radio-emitting magnetic cataclysmic variables or older pulsars with aligned magnetic and spin axes.« less

CPM Is a Useful Cell Surface Marker to Isolate Expandable Bi-Potential Liver Progenitor Cells Derived from Human iPS Cells.

PubMed

Kido, Taketomo; Koui, Yuta; Suzuki, Kaori; Kobayashi, Ayaka; Miura, Yasushi; Chern, Edward Y; Tanaka, Minoru; Miyajima, Atsushi

2015-10-13

To develop a culture system for large-scale production of mature hepatocytes, liver progenitor cells (LPCs) with a high proliferation potential would be advantageous. We have found that carboxypeptidase M (CPM) is highly expressed in embryonic LPCs, hepatoblasts, while its expression is decreased along with hepatic maturation. Consistently, CPM expression was transiently induced during hepatic specification from human-induced pluripotent stem cells (hiPSCs). CPM(+) cells isolated from differentiated hiPSCs at the immature hepatocyte stage proliferated extensively in vitro and expressed a set of genes that were typical of hepatoblasts. Moreover, the CPM(+) cells exhibited a mature hepatocyte phenotype after induction of hepatic maturation and also underwent cholangiocytic differentiation in a three-dimensional culture system. These results indicated that hiPSC-derived CPM(+) cells share the characteristics of LPCs, with the potential to proliferate and differentiate bi-directionally. Thus, CPM is a useful marker for isolating hiPSC-derived LPCs, which allows development of a large-scale culture system for producing hepatocytes and cholangiocytes. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

CPM Is a Useful Cell Surface Marker to Isolate Expandable Bi-Potential Liver Progenitor Cells Derived from Human iPS Cells

PubMed Central

Kido, Taketomo; Koui, Yuta; Suzuki, Kaori; Kobayashi, Ayaka; Miura, Yasushi; Chern, Edward Y.; Tanaka, Minoru; Miyajima, Atsushi

2015-01-01

Summary To develop a culture system for large-scale production of mature hepatocytes, liver progenitor cells (LPCs) with a high proliferation potential would be advantageous. We have found that carboxypeptidase M (CPM) is highly expressed in embryonic LPCs, hepatoblasts, while its expression is decreased along with hepatic maturation. Consistently, CPM expression was transiently induced during hepatic specification from human-induced pluripotent stem cells (hiPSCs). CPM+ cells isolated from differentiated hiPSCs at the immature hepatocyte stage proliferated extensively in vitro and expressed a set of genes that were typical of hepatoblasts. Moreover, the CPM+ cells exhibited a mature hepatocyte phenotype after induction of hepatic maturation and also underwent cholangiocytic differentiation in a three-dimensional culture system. These results indicated that hiPSC-derived CPM+ cells share the characteristics of LPCs, with the potential to proliferate and differentiate bi-directionally. Thus, CPM is a useful marker for isolating hiPSC-derived LPCs, which allows development of a large-scale culture system for producing hepatocytes and cholangiocytes. PMID:26365514

Steric interactions lead to collective tilting motion in the ribosome during mRNA-tRNA translocation

NASA Astrophysics Data System (ADS)

Nguyen, Kien; Whitford, Paul C.

2016-02-01

Translocation of mRNA and tRNA through the ribosome is associated with large-scale rearrangements of the head domain in the 30S ribosomal subunit. To elucidate the relationship between 30S head dynamics and mRNA-tRNA displacement, we apply molecular dynamics simulations using an all-atom structure-based model. Here we provide a statistical analysis of 250 spontaneous transitions between the A/P-P/E and P/P-E/E ensembles. Consistent with structural studies, the ribosome samples a chimeric ap/P-pe/E intermediate, where the 30S head is rotated ~18°. It then transiently populates a previously unreported intermediate ensemble, which is characterized by a ~10° tilt of the head. To identify the origins of head tilting, we analyse 781 additional simulations in which specific steric features are perturbed. These calculations show that head tilting may be attributed to specific steric interactions between tRNA and the 30S subunit (PE loop and protein S13). Taken together, this study demonstrates how molecular structure can give rise to large-scale collective rearrangements.

Production of lentiviral vectors

PubMed Central

Merten, Otto-Wilhelm; Hebben, Matthias; Bovolenta, Chiara

2016-01-01

Lentiviral vectors (LV) have seen considerably increase in use as gene therapy vectors for the treatment of acquired and inherited diseases. This review presents the state of the art of the production of these vectors with particular emphasis on their large-scale production for clinical purposes. In contrast to oncoretroviral vectors, which are produced using stable producer cell lines, clinical-grade LV are in most of the cases produced by transient transfection of 293 or 293T cells grown in cell factories. However, more recent developments, also, tend to use hollow fiber reactor, suspension culture processes, and the implementation of stable producer cell lines. As is customary for the biotech industry, rather sophisticated downstream processing protocols have been established to remove any undesirable process-derived contaminant, such as plasmid or host cell DNA or host cell proteins. This review compares published large-scale production and purification processes of LV and presents their process performances. Furthermore, developments in the domain of stable cell lines and their way to the use of production vehicles of clinical material will be presented. PMID:27110581

Classification of epilepsy types through global network analysis of scalp electroencephalograms

NASA Astrophysics Data System (ADS)

Lee, Uncheol; Kim, Seunghwan; Jung, Ki-Young

2006-04-01

Epilepsy is a dynamic disease in which self-organization and emergent structures occur dynamically at multiple levels of neuronal integration. Therefore, the transient relationship within multichannel electroencephalograms (EEGs) is crucial for understanding epileptic processes. In this paper, we show that the global relationship within multichannel EEGs provides us with more useful information in classifying two different epilepsy types than pairwise relationships such as cross correlation. To demonstrate this, we determine the global network structure within channels of the scalp EEG based on the minimum spanning tree method. The topological dissimilarity of the network structures from different types of temporal lobe epilepsy is described in the form of the divergence rate and is computed for 11 patients with left (LTLE) and right temporal lobe epilepsy (RTLE). We find that patients with LTLE and RTLE exhibit different large scale network structures, which emerge at the epoch immediately before the seizure onset, not in the preceding epochs. Our results suggest that patients with the two different epilepsy types display distinct large scale dynamical networks with characteristic epileptic network structures.

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

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

Chen, F.; Zhu, Y.; Liu, S.

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. Thismore » effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

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

Chen, F.; Zhu, Y.; Liu, S.

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent acrossmore » unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

DOE PAGES

Chen, F.; Zhu, Y.; Liu, S.; ...

2016-11-22

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent acrossmore » unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

Commercial-scale biotherapeutics manufacturing facility for plant-made pharmaceuticals.

PubMed

Holtz, Barry R; Berquist, Brian R; Bennett, Lindsay D; Kommineni, Vally J M; Munigunti, Ranjith K; White, Earl L; Wilkerson, Don C; Wong, Kah-Yat I; Ly, Lan H; Marcel, Sylvain

2015-10-01

Rapid, large-scale manufacture of medical countermeasures can be uniquely met by the plant-made-pharmaceutical platform technology. As a participant in the Defense Advanced Research Projects Agency (DARPA) Blue Angel project, the Caliber Biotherapeutics facility was designed, constructed, commissioned and released a therapeutic target (H1N1 influenza subunit vaccine) in <18 months from groundbreaking. As of 2015, this facility was one of the world's largest plant-based manufacturing facilities, with the capacity to process over 3500 kg of plant biomass per week in an automated multilevel growing environment using proprietary LED lighting. The facility can commission additional plant grow rooms that are already built to double this capacity. In addition to the commercial-scale manufacturing facility, a pilot production facility was designed based on the large-scale manufacturing specifications as a way to integrate product development and technology transfer. The primary research, development and manufacturing system employs vacuum-infiltrated Nicotiana benthamiana plants grown in a fully contained, hydroponic system for transient expression of recombinant proteins. This expression platform has been linked to a downstream process system, analytical characterization, and assessment of biological activity. This integrated approach has demonstrated rapid, high-quality production of therapeutic monoclonal antibody targets, including a panel of rituximab biosimilar/biobetter molecules and antiviral antibodies against influenza and dengue fever. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Vortex/Flame Interactions in Microgravity Pulsed Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

Bahadori, M. Y.; Hegde, U.; Stocker, D. P.

1999-01-01

The problem of vortex/flame interaction is of fundamental importance to turbulent combustion. These interactions have been studied in normal gravity. It was found that due to the interactions between the imposed disturbances and buoyancy induced instabilities, several overall length scales dominated the flame. The problem of multiple scales does not exist in microgravity for a pulsed laminar flame, since there are no buoyancy induced instabilities. The absence of buoyant convection therefore provides an environment to study the role of vortices interacting with flames in a controlled manner. There are strong similarities between imposed and naturally occurring perturbations, since both can be described by the same spatial instability theory. Hence, imposing a harmonic disturbance on a microgravity laminar flame creates effects similar to those occurring naturally in transitional/turbulent diffusion flames observed in microgravity. In this study, controlled, large-scale, axisymmetric vortices are imposed on a microgravity laminar diffusion flame. The experimental results and predictions from a numerical model of transient jet diffusion flames are presented and the characteristics of pulsed flame are described.

A detailed model for simulation of catchment scale subsurface hydrologic processes

NASA Technical Reports Server (NTRS)

Paniconi, Claudio; Wood, Eric F.

1993-01-01

A catchment scale numerical model is developed based on the three-dimensional transient Richards equation describing fluid flow in variably saturated porous media. The model is designed to take advantage of digital elevation data bases and of information extracted from these data bases by topographic analysis. The practical application of the model is demonstrated in simulations of a small subcatchment of the Konza Prairie reserve near Manhattan, Kansas. In a preliminary investigation of computational issues related to model resolution, we obtain satisfactory numerical results using large aspect ratios, suggesting that horizontal grid dimensions may not be unreasonably constrained by the typically much smaller vertical length scale of a catchment and by vertical discretization requirements. Additional tests are needed to examine the effects of numerical constraints and parameter heterogeneity in determining acceptable grid aspect ratios. In other simulations we attempt to match the observed streamflow response of the catchment, and we point out the small contribution of the streamflow component to the overall water balance of the catchment.

Induced groundwater flux by increases in the aquifer's total stress.

PubMed

Chang, Ching-Min; Yeh, Hund-Der

2015-01-01

Fluid-filled granular soils experience changes in total stress because of earth and oceanic tides, earthquakes, erosion, sedimentation, and changes in atmospheric pressure. The pore volume may deform in response to the changes in stress and this may lead to changes in pore fluid pressure. The transient fluid flow can therefore be induced by the gradient in excess pressure in a fluid-saturated porous medium. This work demonstrates the use of stochastic methodology in prediction of induced one-dimensional field-scale groundwater flow through a heterogeneous aquifer. A closed-form of mean groundwater flux is developed to quantify the induced field-scale mean behavior of groundwater flow and analyze the impacts of the spatial correlation length scale of log hydraulic conductivity and the pore compressibility. The findings provided here could be useful for the rational planning and management of groundwater resources in aquifers that contain lenses with large vertical aquifer matrix compressibility values. © 2014, National Ground Water Association.

Low transient storage and uptake efficiencies in seven agricultural streams: implications for nutrient demand

USGS Publications Warehouse

Sheibley, Rich W.; Duff, John H.; Tesoriero, Anthony J.

2014-01-01

We used mass load budgets, transient storage modeling, and nutrient spiraling metrics to characterize nitrate (NO3−), ammonium (NH4+), and inorganic phosphorus (SRP) demand in seven agricultural streams across the United States and to identify in-stream services that may control these conditions. Retention of one or all nutrients was observed in all but one stream, but demand for all nutrients was low relative to the mass in transport. Transient storage metrics (As/A, Fmed200, Tstr, and qs) correlated with NO3− retention but not NH4+ or SRP retention, suggesting in-stream services associated with transient storage and stream water residence time could influence reach-scale NO3− demand. However, because the fraction of median reach-scale travel time due to transient storage (Fmed200) was ≤1.2% across the sites, only a relatively small demand for NO3− could be generated by transient storage. In contrast, net uptake of nutrients from the water column calculated from nutrient spiraling metrics were not significant at any site because uptake lengths calculated from background nutrient concentrations were statistically insignificant and therefore much longer than the study reaches. These results suggest that low transient storage coupled with high surface water NO3− inputs have resulted in uptake efficiencies that are not sufficient to offset groundwater inputs of N. Nutrient retention has been linked to physical and hydrogeologic elements that drive flow through transient storage areas where residence time and biotic contact are maximized; however, our findings indicate that similar mechanisms are unable to generate a significant nutrient demand in these streams relative to the loads.

Patients' and procedural characteristics of AV-block during slow pathway modulation for AVNRT-single center 10year experience.

PubMed

Wasmer, Kristina; Dechering, Dirk G; Köbe, Julia; Leitz, Patrick; Frommeyer, Gerrit; Lange, Phillip S; Kochhäuser, Simon; Reinke, Florian; Pott, Christian; Mönnig, Gerold; Breithardt, Günter; Eckardt, Lars

2017-10-01

Permanent AV-block is a recognized and feared complication of slow pathway modulation for AVNRT. We aimed to assess incidence of transient and permanent AV-block as well as consequences of transient AV-block in a large contemporary AVNRT ablation cohort. We searched our single center prospective ablation database for occurrence of transient and permanent AV-block during slow pathway modulation between January 2004 and October 2015. We analyzed patients' and procedural characteristics as well as outcome of patients in whom transient or permanent AV-block occurred. Of 9170 patients who underwent a catheter ablation at our institution between January 2004 and October 2015, 2101 patients (64% women, mean age 50±18years) underwent slow pathway modulation. In three patients, permanent AV-block occurred during RF application. Additional two patients had transient AV-block that recovered (after a few minutes and 25min), but recurred within two days of the procedure. All five patients underwent dual chamber pacemaker implantation (0.2%). Transient AV-block related to RF delivery occurred in 44 patients (2%). Transient mechanical AV-block occurred in additional 17 patients (0.8%). In 12 patients, ablation was continued despite transient AV-block. One of these patients developed permanent AV-block. Permanent AV-block following slow pathway modulation is a rare event, occurring in 0.2% of patients in a large contemporary single center cohort. Transient AV-block is more frequent (2%). Copyright © 2017 Elsevier B.V. All rights reserved.

Seismic and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory

USGS Publications Warehouse

Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.

2011-01-01

We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and seismic modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station seismic network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of seismic signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip faults. The landslide basal surface beneath our seismic network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.

Method for detecting moment connection fracture using high-frequency transients in recorded accelerations

USGS Publications Warehouse

Rodgers, J.E.; Elebi, M.

2011-01-01

The 1994 Northridge earthquake caused brittle fractures in steel moment frame building connections, despite causing little visible building damage in most cases. Future strong earthquakes are likely to cause similar damage to the many un-retrofitted pre-Northridge buildings in the western US and elsewhere. Without obvious permanent building deformation, costly intrusive inspections are currently the only way to determine if major fracture damage that compromises building safety has occurred. Building instrumentation has the potential to provide engineers and owners with timely information on fracture occurrence. Structural dynamics theory predicts and scale model experiments have demonstrated that sudden, large changes in structure properties caused by moment connection fractures will cause transient dynamic response. A method is proposed for detecting the building-wide level of connection fracture damage, based on observing high-frequency, fracture-induced transient dynamic responses in strong motion accelerograms. High-frequency transients are short (<1 s), sudden-onset waveforms with frequency content above 25 Hz that are visually apparent in recorded accelerations. Strong motion data and damage information from intrusive inspections collected from 24 sparsely instrumented buildings following the 1994 Northridge earthquake are used to evaluate the proposed method. The method's overall success rate for this data set is 67%, but this rate varies significantly with damage level. The method performs reasonably well in detecting significant fracture damage and in identifying cases with no damage, but fails in cases with few fractures. Combining the method with other damage indicators and removing records with excessive noise improves the ability to detect the level of damage. ?? 2010 Elsevier B.V. All rights reserved.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed

Ma, Xiaohui; Chang, Ping; Saravanan, R; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-12-04

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy-atmosphere interaction in forecast and climate models.

Reorientations of the large-scale flow in turbulent convection in a cube

NASA Astrophysics Data System (ADS)

Foroozani, N.; Niemela, J. J.; Armenio, V.; Sreenivasan, K. R.

2017-03-01

Large-eddy simulations of turbulent Rayleigh-Bénard convection were conducted for a fluid of Prandtl number Pr=0.7 confined in a cube, for Rayleigh numbers of 106 and 108. The model solves the unsteady Navier-Stokes equations under the Boussinesq approximation, using a dynamic Smagorinsky model with a Lagrangian averaging technique for the subgrid terms. Under fully developed conditions the flow topology is characterized by a large-scale circulation (LSC) developing in a plane containing one of the diagonals of the cell, while two counter-rotating vortices consequently develop in the other diagonal plane, resulting in a strong inflow at the horizontal midplane. This flow structure is not static, with the LSC undergoing nonperiodic reorientations, or switching, between the two diagonal planes; hence, we supplement the observations of the three-dimensional time-averaged flow structures with single point measurements (time series) to shed light on the dynamics of the reorientations. For all observations, this switching results from a lateral rotation of the LSC in which some finite time spent in a transient state where the large-scale circulation is parallel to one set of side walls; there are, importantly, no observations consistent with so-called cessations of the LSC, in which it decays and then reforms in another plane without such a rotation. The average switching rate for the LSC is in excellent agreement with the results of Bai et al. [K. Bai, D. Ji, and E. Brown, Phys. Rev. E 93, 023117 (2016), 10.1103/PhysRevE.93.023117].

Scalable subsurface inverse modeling of huge data sets with an application to tracer concentration breakthrough data from magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Lee, Jonghyun; Yoon, Hongkyu; Kitanidis, Peter K.; Werth, Charles J.; Valocchi, Albert J.

2016-07-01

Characterizing subsurface properties is crucial for reliable and cost-effective groundwater supply management and contaminant remediation. With recent advances in sensor technology, large volumes of hydrogeophysical and geochemical data can be obtained to achieve high-resolution images of subsurface properties. However, characterization with such a large amount of information requires prohibitive computational costs associated with "big data" processing and numerous large-scale numerical simulations. To tackle such difficulties, the principal component geostatistical approach (PCGA) has been proposed as a "Jacobian-free" inversion method that requires much smaller forward simulation runs for each iteration than the number of unknown parameters and measurements needed in the traditional inversion methods. PCGA can be conveniently linked to any multiphysics simulation software with independent parallel executions. In this paper, we extend PCGA to handle a large number of measurements (e.g., 106 or more) by constructing a fast preconditioner whose computational cost scales linearly with the data size. For illustration, we characterize the heterogeneous hydraulic conductivity (K) distribution in a laboratory-scale 3-D sand box using about 6 million transient tracer concentration measurements obtained using magnetic resonance imaging. Since each individual observation has little information on the K distribution, the data were compressed by the zeroth temporal moment of breakthrough curves, which is equivalent to the mean travel time under the experimental setting. Only about 2000 forward simulations in total were required to obtain the best estimate with corresponding estimation uncertainty, and the estimated K field captured key patterns of the original packing design, showing the efficiency and effectiveness of the proposed method.

Reorientations of the large-scale flow in turbulent convection in a cube.

PubMed

Foroozani, N; Niemela, J J; Armenio, V; Sreenivasan, K R

2017-03-01

Large-eddy simulations of turbulent Rayleigh-Bénard convection were conducted for a fluid of Prandtl number Pr=0.7 confined in a cube, for Rayleigh numbers of 10^{6} and 10^{8}. The model solves the unsteady Navier-Stokes equations under the Boussinesq approximation, using a dynamic Smagorinsky model with a Lagrangian averaging technique for the subgrid terms. Under fully developed conditions the flow topology is characterized by a large-scale circulation (LSC) developing in a plane containing one of the diagonals of the cell, while two counter-rotating vortices consequently develop in the other diagonal plane, resulting in a strong inflow at the horizontal midplane. This flow structure is not static, with the LSC undergoing nonperiodic reorientations, or switching, between the two diagonal planes; hence, we supplement the observations of the three-dimensional time-averaged flow structures with single point measurements (time series) to shed light on the dynamics of the reorientations. For all observations, this switching results from a lateral rotation of the LSC in which some finite time spent in a transient state where the large-scale circulation is parallel to one set of side walls; there are, importantly, no observations consistent with so-called cessations of the LSC, in which it decays and then reforms in another plane without such a rotation. The average switching rate for the LSC is in excellent agreement with the results of Bai et al. [K. Bai, D. Ji, and E. Brown, Phys. Rev. E 93, 023117 (2016)PLEEE81539-375510.1103/PhysRevE.93.023117].

RACORO Continental Boundary Layer Cloud Investigations: 1. Case Study Development and Ensemble Large-Scale Forcings

NASA Technical Reports Server (NTRS)

Vogelmann, Andrew M.; Fridlind, Ann M.; Toto, Tami; Endo, Satoshi; Lin, Wuyin; Wang, Jian; Feng, Sha; Zhang, Yunyan; Turner, David D.; Liu, Yangang;

RACORO continental boundary layer cloud investigations: 1. Case study development and ensemble large-scale forcings

NASA Astrophysics Data System (ADS)

Vogelmann, Andrew M.; Fridlind, Ann M.; Toto, Tami; Endo, Satoshi; Lin, Wuyin; Wang, Jian; Feng, Sha; Zhang, Yunyan; Turner, David D.; Liu, Yangang; Li, Zhijin; Xie, Shaocheng; Ackerman, Andrew S.; Zhang, Minghua; Khairoutdinov, Marat

2015-06-01

Observation-based modeling case studies of continental boundary layer clouds have been developed to study cloudy boundary layers, aerosol influences upon them, and their representation in cloud- and global-scale models. Three 60 h case study periods span the temporal evolution of cumulus, stratiform, and drizzling boundary layer cloud systems, representing mixed and transitional states rather than idealized or canonical cases. Based on in situ measurements from the Routine AAF (Atmospheric Radiation Measurement (ARM) Aerial Facility) CLOWD (Clouds with Low Optical Water Depth) Optical Radiative Observations (RACORO) field campaign and remote sensing observations, the cases are designed with a modular configuration to simplify use in large-eddy simulations (LES) and single-column models. Aircraft measurements of aerosol number size distribution are fit to lognormal functions for concise representation in models. Values of the aerosol hygroscopicity parameter, κ, are derived from observations to be 0.10, which are lower than the 0.3 typical over continents and suggestive of a large aerosol organic fraction. Ensemble large-scale forcing data sets are derived from the ARM variational analysis, European Centre for Medium-Range Weather Forecasts, and a multiscale data assimilation system. The forcings are assessed through comparison of measured bulk atmospheric and cloud properties to those computed in "trial" large-eddy simulations, where more efficient run times are enabled through modest reductions in grid resolution and domain size compared to the full-sized LES grid. Simulations capture many of the general features observed, but the state-of-the-art forcings were limited at representing details of cloud onset, and tight gradients and high-resolution transients of importance. Methods for improving the initial conditions and forcings are discussed. The cases developed are available to the general modeling community for studying continental boundary clouds.

Dynamically Consistent Parameterization of Mesoscale Eddies This work aims at parameterization of eddy effects for use in non-eddy-resolving ocean models and focuses on the effect of the stochastic part of the eddy forcing that backscatters and induces eastward jet extension of the western boundary currents and its adjacent recirculation zones.

NASA Astrophysics Data System (ADS)

Berloff, P. S.

2016-12-01

This work aims at developing a framework for dynamically consistent parameterization of mesoscale eddy effects for use in non-eddy-resolving ocean circulation models. The proposed eddy parameterization framework is successfully tested on the classical, wind-driven double-gyre model, which is solved both with explicitly resolved vigorous eddy field and in the non-eddy-resolving configuration with the eddy parameterization replacing the eddy effects. The parameterization focuses on the effect of the stochastic part of the eddy forcing that backscatters and induces eastward jet extension of the western boundary currents and its adjacent recirculation zones. The parameterization locally approximates transient eddy flux divergence by spatially localized and temporally periodic forcing, referred to as the plunger, and focuses on the linear-dynamics flow solution induced by it. The nonlinear self-interaction of this solution, referred to as the footprint, characterizes and quantifies the induced eddy forcing exerted on the large-scale flow. We find that spatial pattern and amplitude of each footprint strongly depend on the underlying large-scale flow, and the corresponding relationships provide the basis for the eddy parameterization and its closure on the large-scale flow properties. Dependencies of the footprints on other important parameters of the problem are also systematically analyzed. The parameterization utilizes the local large-scale flow information, constructs and scales the corresponding footprints, and then sums them up over the gyres to produce the resulting eddy forcing field, which is interactively added to the model as an extra forcing. Thus, the assumed ensemble of plunger solutions can be viewed as a simple model for the cumulative effect of the stochastic eddy forcing. The parameterization framework is implemented in the simplest way, but it provides a systematic strategy for improving the implementation algorithm.

Scaling laws for perturbations in the ocean-atmosphere system following large CO2 emissions

NASA Astrophysics Data System (ADS)

Towles, N.; Olson, P.; Gnanadesikan, A.

2015-01-01

Scaling relationships are derived for the perturbations to atmosphere and ocean variables from large transient CO2 emissions. Using the carbon cycle model LOSCAR (Zeebe et al., 2009; Zeebe, 2012b) we calculate perturbations to atmosphere temperature and total carbon, ocean temperature, total ocean carbon, pH, and alkalinity, marine sediment carbon, plus carbon-13 isotope anomalies in the ocean and atmosphere resulting from idealized CO2 emission events. The peak perturbations in the atmosphere and ocean variables are then fit to power law functions of the form γDαEbeta, where D is the event duration, E is its total carbon emission, and γ is a coefficient. Good power law fits are obtained for most system variables for E up to 50 000 PgC and D up to 100 kyr. However, these power laws deviate substantially from predictions based on simplified equilibrium considerations. For example, although all of the peak perturbations increase with emission rate E/D, we find no evidence of emission rate-only scaling α + β =0, a prediction of the long-term equilibrium between CO2 input by volcanism and CO2 removal by silicate weathering. Instead, our scaling yields α + β ≃ 1 for total ocean and atmosphere carbon and 0< α + β < 1 for most of the other system variables. The deviations in these scaling laws from equilibrium predictions are mainly due to the multitude and diversity of time scales that govern the exchange of carbon between marine sediments, the ocean, and the atmosphere.

Computational and Experimental Study of the Transient Transport Phenomena in a Full-Scale Twin-Roll Continuous Casting Machine

NASA Astrophysics Data System (ADS)

Xu, Mianguang; Li, Zhongyang; Wang, Zhaohui; Zhu, Miaoyong

2017-02-01

To gain a fundamental understanding of the transient fluid flow in twin-roll continuous casting, the current paper applies both large eddy simulation (LES) and full-scale water modeling experiments to investigate the characteristics of the top free surface, stirring effect of the roll rotation, boundary layer fluctuations, and backflow stability. The results show that, the characteristics of the top free surface and the flow field in the wedge-shaped pool region are quite different with/without the consideration of the roll rotation. The roll rotation decreases the instantaneous fluctuation range of the top free surface, but increases its horizontal velocity. The stirring effect of the roll rotating makes the flow field more homogenous and there exists clear shear flow on the rotating roll surface. The vortex shedding induced by the Kármán Vortex Street from the submerged entry nozzle (SEN) causes the "velocity magnitude wave" and strongly influences the boundary layer stability and the backflow stability. The boundary layer fluctuations or the "velocity magnitude wave" induced by the vortex shedding could give rise to the internal porosity. In strip continuous casting process, the vortex shedding phenomenon indicates that the laminar flow can give rise to instability and that it should be made important in the design of the feeding system and the setting of the operating parameters.

Papaloizou-Pringle instability suppression by the magnetorotational instability in relativistic accretion discs

NASA Astrophysics Data System (ADS)

Bugli, M.; Guilet, J.; Müller, E.; Del Zanna, L.; Bucciantini, N.; Montero, P. J.

2018-03-01

Geometrically thick tori with constant specific angular momentum have been widely used in the last decades to construct numerical models of accretion flows on to black holes. Such discs are prone to a global non-axisymmetric hydrodynamic instability, known as Papaloizou-Pringle instability (PPI), which can redistribute angular momentum and also lead to an emission of gravitational waves. It is, however, not clear yet how the development of the PPI is affected by the presence of a magnetic field and by the concurrent development of the magnetorotational instability (MRI). We present a numerical analysis using three-dimensional GRMHD simulations of the interplay between the PPI and the MRI considering, for the first time, an analytical magnetized equilibrium solution as initial condition. In the purely hydrodynamic case, the PPI selects as expected the large-scale m = 1 azimuthal mode as the fastest growing and non-linearly dominant mode. However, when the torus is threaded by a weak toroidal magnetic field, the development of the MRI leads to the suppression of large-scale modes and redistributes power across smaller scales. If the system starts with a significantly excited m = 1 mode, the PPI can be dominant in a transient phase, before being ultimately quenched by the MRI. Such dynamics may well be important in compact star mergers and tidal disruption events.

Stochastic theory of log-periodic patterns

NASA Astrophysics Data System (ADS)

Canessa, Enrique

2000-12-01

We introduce an analytical model based on birth-death clustering processes to help in understanding the empirical log-periodic corrections to power law scaling and the finite-time singularity as reported in several domains including rupture, earthquakes, world population and financial systems. In our stochastic theory log-periodicities are a consequence of transient clusters induced by an entropy-like term that may reflect the amount of co-operative information carried by the state of a large system of different species. The clustering completion rates for the system are assumed to be given by a simple linear death process. The singularity at t0 is derived in terms of birth-death clustering coefficients.

Modelling and operation strategies of DLR's large scale thermocline test facility (TESIS)

NASA Astrophysics Data System (ADS)

Odenthal, Christian; Breidenbach, Nils; Bauer, Thomas

2017-06-01

In this work an overview of the TESIS:store thermocline test facility and its current construction status will be given. Based on this, the TESIS:store facility using sensible solid filler material is modelled with a fully transient model, implemented in MATLAB®. Results in terms of the impact of filler site and operation strategies will be presented. While low porosity and small particle diameters for the filler material are beneficial, operation strategy is one key element with potential for optimization. It is shown that plant operators have to ponder between utilization and exergetic efficiency. Different durations of the charging and discharging period enable further potential for optimizations.

Production technology for high efficiency ion implanted solar cells

NASA Technical Reports Server (NTRS)

Kirkpatrick, A. R.; Minnucci, J. A.; Greenwald, A. C.; Josephs, R. H.

1978-01-01

Ion implantation is being developed for high volume automated production of silicon solar cells. An implanter designed for solar cell processing and able to properly implant up to 300 4-inch wafers per hour is now operational. A machine to implant 180 sq m/hr of solar cell material has been designed. Implanted silicon solar cells with efficiencies exceeding 16% AM1 are now being produced and higher efficiencies are expected. Ion implantation and transient processing by pulsed electron beams are being integrated with electrostatic bonding to accomplish a simple method for large scale, low cost production of high efficiency solar cell arrays.

Utilization of ERTS-1 data in geological evaluation, regional planning, forest management, and water management in North Carolina

NASA Technical Reports Server (NTRS)

Welby, C. W. (Principal Investigator); Lammi, J. O.; Carson, R. J., III

1974-01-01

The author has identified the following significant results. ERTS-1 imagery has been evaluated for use in resource planning and management in North Carolina, and found to be useful for general reconnaissance purposes in forestry, geology, and water resources work. It has also been used for studying large-scale transient phenomena such as river plumes and movement of sediment in the sounds. ERTS-1 imagery has been an aid to geologic and land-use mapping. Stereoscopes, projectors of various kinds, and microscopes have proved useful instruments for the kinds of data acquisition needed by resource planners and managers.

Wakefield Computations for the CLIC PETS using the Parallel Finite Element Time-Domain Code T3P

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

Candel, A; Kabel, A.; Lee, L.

In recent years, SLAC's Advanced Computations Department (ACD) has developed the high-performance parallel 3D electromagnetic time-domain code, T3P, for simulations of wakefields and transients in complex accelerator structures. T3P is based on advanced higher-order Finite Element methods on unstructured grids with quadratic surface approximation. Optimized for large-scale parallel processing on leadership supercomputing facilities, T3P allows simulations of realistic 3D structures with unprecedented accuracy, aiding the design of the next generation of accelerator facilities. Applications to the Compact Linear Collider (CLIC) Power Extraction and Transfer Structure (PETS) are presented.

Large-Scale Transient Transfection of Chinese Hamster Ovary Cells in Suspension.

PubMed

Rajendra, Yashas; Balasubramanian, Sowmya; Hacker, David L

2017-01-01

We describe a one-liter transfection of suspension-adapted Chinese hamster ovary (CHO-DG44) cells using polyethyleneimine (PEI) for DNA delivery. The method involves transfection at a high cell density (5 × 10 6 cells/mL) by direct addition of plasmid DNA (pDNA) and PEI to the culture and subsequent incubation at 31 °C with agitation by orbital shaking. We also describe an alternative method in which 90% of the pDNA is replaced by nonspecific (filler) DNA, and the production phase is performed at 31 °C in the presence of 0.25% N, N-dimethylacetamide (DMA).

Transient Phenomena in Multiphase and Multicomponent Systems: Research Report

NASA Astrophysics Data System (ADS)

Zur Beurteilung von Stoffen in der Landwirtschaft, Senatskommission

2000-09-01

Due to the reinforced risk and safety-analysis of industrial plants in chemical and energy-engineering there has been increased demand in industry for more information on thermo- and fluiddynamic effects of non-equilibria during strong transients. Therefore, the 'Deutsche Forschungsgemeinschaft' initiated a special research program focusing on the study of transient phenomena in multiphase systems with one or several components. This book describes macroscopic as well as microscopic transient situations. A large part of the book deals with numerical methods for describing transients in two-phase mixtures. New developments in measuring techniques are also presented.

Investigation of Natural Circulation Instability and Transients in Passively Safe Small Modular Reactors

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

Ishii, Mamoru

The NEUP funded project, NEUP-3496, aims to experimentally investigate two-phase natural circulation flow instability that could occur in Small Modular Reactors (SMRs), especially for natural circulation SMRs. The objective has been achieved by systematically performing tests to study the general natural circulation instability characteristics and the natural circulation behavior under start-up or design basis accident conditions. Experimental data sets highlighting the effect of void reactivity feedback as well as the effect of power ramp-up rate and system pressure have been used to develop a comprehensive stability map. The safety analysis code, RELAP5, has been used to evaluate experimental results andmore » models. Improvements to the constitutive relations for flashing have been made in order to develop a reliable analysis tool. This research has been focusing on two generic SMR designs, i.e. a small modular Simplified Boiling Water Reactor (SBWR) like design and a small integral Pressurized Water Reactor (PWR) like design. A BWR-type natural circulation test facility was firstly built based on the three-level scaling analysis of the Purdue Novel Modular Reactor (NMR) with an electric output of 50 MWe, namely NMR-50, which represents a BWR-type SMR with a significantly reduced reactor pressure vessel (RPV) height. The experimental facility was installed with various equipment to measure thermalhydraulic parameters such as pressure, temperature, mass flow rate and void fraction. Characterization tests were performed before the startup transient tests and quasi-steady tests to determine the loop flow resistance. The control system and data acquisition system were programmed with LabVIEW to realize the realtime control and data storage. The thermal-hydraulic and nuclear coupled startup transients were performed to investigate the flow instabilities at low pressure and low power conditions for NMR-50. Two different power ramps were chosen to study the effect of startup power density on the flow instability. The experimental startup transient results showed the existence of three different flow instability mechanisms, i.e., flashing instability, condensation induced flow instability, and density wave oscillations. In addition, the void-reactivity feedback did not have significant effects on the flow instability during the startup transients for NMR-50. ii Several initial startup procedures with different power ramp rates were experimentally investigated to eliminate the flow instabilities observed from the startup transients. Particularly, the very slow startup transient and pressurized startup transient tests were performed and compared. It was found that the very slow startup transients by applying very small power density can eliminate the flashing oscillations in the single-phase natural circulation and stabilize the flow oscillations in the phase of net vapor generation. The initially pressurized startup procedure was tested to eliminate the flashing instability during the startup transients as well. The pressurized startup procedure included the initial pressurization, heat-up, and venting process. The startup transient tests showed that the pressurized startup procedure could eliminate the flow instability during the transition from single-phase flow to two-phase flow at low pressure conditions. The experimental results indicated that both startup procedures were applicable to the initial startup of NMR. However, the pressurized startup procedures might be preferred due to short operating hours required. In order to have a deeper understanding of natural circulation flow instability, the quasi-steady tests were performed using the test facility installed with preheater and subcooler. The effect of system pressure, core inlet subcooling, core power density, inlet flow resistance coefficient, and void reactivity feedback were investigated in the quasi-steady state tests. The experimental stability boundaries were determined between unstable and stable flow conditions in the dimensionless stability plane of inlet subcooling number and Zuber number. To predict the stability boundary theoretically, linear stability analysis in the frequency domain was performed at four sections of the natural circulation test loop. The flashing phenomena in the chimney section was considered as an axially uniform heat source. And the dimensionless characteristic equation of the pressure drop perturbation was obtained by considering the void fraction effect and outlet flow resistance in the core section. The theoretical flashing boundary showed some discrepancies with previous experimental data from the quasi-steady state tests. In the future, thermal non-equilibrium was recommended to improve the accuracy of flashing instability boundary. As another part of the funded research, flow instabilities of a PWR-type SMR under low pressure and low power conditions were investigated experimentally as well. The NuScale reactor design was selected as the prototype for the PWR-type SMR. In order to experimentally study the natural circulation behavior of NuScale iii reactor during accidental scenarios, detailed scaling analyses are necessary to ensure that the scaled phenomena could be obtained in a laboratory test facility. The three-level scaling method is used as well to obtain the scaling ratios derived from various non-dimensional numbers. The design of the ideally scaled facility (ISF) was initially accomplished based on these scaling ratios. Then the engineering scaled facility (ESF) was designed and constructed based on the ISF by considering engineering limitations including laboratory space, pipe size, and pipe connections etc. PWR-type SMR experiments were performed in this well-scaled test facility to investigate the potential thermal hydraulic flow instability during the blowdown events, which might occur during the loss of coolant accident (LOCA) and loss of heat sink accident (LOHS) of the prototype PWR-type SMR. Two kinds of experiments, normal blowdown event and cold blowdown event, were experimentally investigated and compared with code predictions. The normal blowdown event was experimentally simulated since an initial condition where the pressure was lower than the designed pressure of the experiment facility, while the code prediction of blowdown started from the normal operation condition. Important thermal hydraulic parameters including reactor pressure vessel (RPV) pressure, containment pressure, local void fraction and temperature, pressure drop and natural circulation flow rate were measured and analyzed during the blowdown event. The pressure and water level transients are similar to the experimental results published by NuScale [51], which proves the capability of current loop in simulating the thermal hydraulic transient of real PWR-type SMR. During the 20000s blowdown experiment, water level in the core was always above the active fuel assemble during the experiment and proved the safety of natural circulation cooling and water recycling design of PWR-type SMR. Besides, pressure, temperature, and water level transient can be accurately predicted by RELAP5 code. However, the oscillations of natural circulation flow rate, water level and pressure drops were observed during the blowdown transients. This kind of flow oscillations are related to the water level and the location upper plenum, which is a path for coolant flow from chimney to steam generator and down comer. In order to investigate the transients start from the opening of ADS valve in both experimental and numerical way, the cold blow-down experiment is conducted. For the cold blowdown event, different from setting both reactor iv pressure vessel (RPV) and containment at high temperature and pressure, only RPV was heated close to the highest designed pressure and then open the ADS valve, same process was predicted using RELAP5 code. By doing cold blowdown experiment, the entire transients from the opening of ADS can be investigated by code and benchmarked with experimental data. Similar flow instability observed in the cold blowdown experiment. The comparison between code prediction and experiment data showed that the RELAP5 code can successfully predict the pressure void fraction and temperature transient during the cold blowdown event with limited error, but numerical instability exists in predicting natural circulation flow rate. Besides, the code is lack of capability in predicting the water level related flow instability observed in experiments.« less

VLITE-Fast: A Real-time, 350 MHz Commensal VLA Survey for Fast Transients

NASA Astrophysics Data System (ADS)

Kerr, Matthew; Ray, Paul S.; Kassim, Namir E.; Clarke, Tracy; Deneva, Julia; Polisensky, Emil

2018-01-01

The VLITE (VLA Low Band Ionosphere and Transient Experiment; http://vlite.nrao.edu) program operates commensally during all Very Large Array observations, collecting data from 320 to 384 MHz. Recently expanded to include 16 antennas, the large field of view and huge time on sky offer good coverage of the transient, low-frequency sky. We describe the VLITE-Fast system, a GPU-based signal processor capable of detecting short (<1s) transients in real time and triggering recording of baseband voltage for offline imaging. In the case of Fast Radio Bursts, this offers the opportunity for discovering host galaxies of non-repeating FRBs, and in the case of single pulses, the identification of pulsar positions for dedicated follow-up. We describe the observing system, techniques for mitigating interference, and initial results from searches for FRBs.

Mesoscale Computational Investigation of Shocked Heterogeneous Materials with Application to Large Impact Craters

NASA Technical Reports Server (NTRS)

Crawford, D. A.; Barnouin-Jha, O. S.; Cintala, M. J.

2003-01-01

The propagation of shock waves through target materials is strongly influenced by the presence of small-scale structure, fractures, physical and chemical heterogeneities. Pre-existing fractures often create craters that appear square in outline (e.g. Meteor Crater). Reverberations behind the shock from the presence of physical heterogeneity have been proposed as a mechanism for transient weakening of target materials. Pre-existing fractures can also affect melt generation. In this study, we are attempting to bridge the gap in numerical modeling between the micro-scale and the continuum, the so-called meso-scale. To accomplish this, we are developing a methodology to be used in the shock physics hydrocode (CTH) using Monte-Carlo-type methods to investigate the shock properties of heterogeneous materials. By comparing the results of numerical experiments at the micro-scale with experimental results and by using statistical techniques to evaluate the performance of simple constitutive models, we hope to embed the effect of physical heterogeneity into the field variables (pressure, stress, density, velocity) allowing us to directly imprint the effects of micro-scale heterogeneity at the continuum level without incurring high computational cost.

Extratropical Weather Systems on Mars: Radiatively-Active Water Ice Effects

NASA Technical Reports Server (NTRS)

Hollingsworth, J. L.; Kahre, M. A.; Haberle, R. M.; Urata, R. A.; Montmessin, F.

2017-01-01

Extratropical, large-scale weather disturbances, namely transient, synoptic-period,baroclinic barotropic eddies - or - low- (high-) pressure cyclones (anticyclones), are components fundamental to global circulation patterns for rapidly rotating, differentially heated, shallow atmospheres such as Earth and Mars. Such "wave-like" disturbances that arise via (geophysical) fluid shear instability develop, mature and decay, and travel west-to-east in the middle and high latitudes within terrestrial-like planetary atmospheres. These disturbances serve as critical agents in the transport of heat and momentum between low and high latitudes of the planet. Moreover, they transport trace species within the atmosphere (e.g., water vapor/ice, other aerosols (dust), chemical species, etc). Between early autumn through early spring, middle and high latitudes on Mars exhibit strong equator-to-pole mean temperature contrasts (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that such strong baroclinicity supports vigorous, large-scale eastward traveling weather systems [Banfield et al., 2004; Barnes et al., 1993]. A good example of traveling weather systems, frontal wave activity and sequestered dust activity from MGS/MOC image analyses is provided in Figure 1 (cf. Wang et al. [2005]). Utilizing an upgraded and evolving version of the NASA Ames Research Center (ARC) Mars global climate model, investigated here are key dynamical and physical aspects of simulated northern hemisphere (NH) large-scale extratropica lweather systems,with and without radiatively-active water ice clouds. Mars Climate Model:

Liquid Oxygen Propellant Densification Production and Performance Test Results With a Large-Scale Flight-Weight Propellant Tank for the X33 RLV

NASA Technical Reports Server (NTRS)

Tomsik, Thomas M.; Meyer, Michael L.

2010-01-01

This paper describes in-detail a test program that was initiated at the Glenn Research Center (GRC) involving the cryogenic densification of liquid oxygen (LO2). A large scale LO2 propellant densification system rated for 200 gpm and sized for the X-33 LO2 propellant tank, was designed, fabricated and tested at the GRC. Multiple objectives of the test program included validation of LO2 production unit hardware and characterization of densifier performance at design and transient conditions. First, performance data is presented for an initial series of LO2 densifier screening and check-out tests using densified liquid nitrogen. The second series of tests show performance data collected during LO2 densifier test operations with liquid oxygen as the densified product fluid. An overview of LO2 X-33 tanking operations and load tests with the 20,000 gallon Structural Test Article (STA) are described. Tank loading testing and the thermal stratification that occurs inside of a flight-weight launch vehicle propellant tank were investigated. These operations involved a closed-loop recirculation process of LO2 flow through the densifier and then back into the STA. Finally, in excess of 200,000 gallons of densified LO2 at 120 oR was produced with the propellant densification unit during the demonstration program, an achievement that s never been done before in the realm of large-scale cryogenic tests.

Rhythms of Consciousness: Binocular Rivalry Reveals Large-Scale Oscillatory Network Dynamics Mediating Visual Perception

PubMed Central

Doesburg, Sam M.; Green, Jessica J.; McDonald, John J.; Ward, Lawrence M.

2009-01-01

Consciousness has been proposed to emerge from functionally integrated large-scale ensembles of gamma-synchronous neural populations that form and dissolve at a frequency in the theta band. We propose that discrete moments of perceptual experience are implemented by transient gamma-band synchronization of relevant cortical regions, and that disintegration and reintegration of these assemblies is time-locked to ongoing theta oscillations. In support of this hypothesis we provide evidence that (1) perceptual switching during binocular rivalry is time-locked to gamma-band synchronizations which recur at a theta rate, indicating that the onset of new conscious percepts coincides with the emergence of a new gamma-synchronous assembly that is locked to an ongoing theta rhythm; (2) localization of the generators of these gamma rhythms reveals recurrent prefrontal and parietal sources; (3) theta modulation of gamma-band synchronization is observed between and within the activated brain regions. These results suggest that ongoing theta-modulated-gamma mechanisms periodically reintegrate a large-scale prefrontal-parietal network critical for perceptual experience. Moreover, activation and network inclusion of inferior temporal cortex and motor cortex uniquely occurs on the cycle immediately preceding responses signaling perceptual switching. This suggests that the essential prefrontal-parietal oscillatory network is expanded to include additional cortical regions relevant to tasks and perceptions furnishing consciousness at that moment, in this case image processing and response initiation, and that these activations occur within a time frame consistent with the notion that conscious processes directly affect behaviour. PMID:19582165

Transient etiolation: protochlorophyll(ide) and chlorophyll forms in differentiating plastids of closed and breaking leaf buds of horse chestnut (Aesculus hippocastanum).

PubMed

Solymosi, Katalin; Bóka, Károly; Böddi, Béla

2006-08-01

An accompanying paper reports the accumulation of photoactive protochlorophyllide (Pchlide) in the innermost leaf primordia of buds of many tree species. In this paper, we describe plastid differentiation, changes in pigment concentrations and spectral properties of bud scales and leaf primordia of horse chestnut (Aesculus hippocastanum L.) from January until the end of bud break in April. The bud scales contained plastids with grana, stroma thylakoids characteristic of chloroplasts and large dense bodies within the stroma. In January, proplastids and young chloroplasts were present in the leaf primordia, and the fluorescence spectra of the primordia were similar to those of green leaves except for a minor band at 630 nm, indicative of a protochlorophyll(ide). During bud break, the pigment concentrations of the green bud scales and the outermost leaf primordia increased, and Pchlide forms with emission maxima at 633, 644 and 655 nm accumulated in the middle and innermost leaf primordia. Depending on the position of the leaf primordia within the bud, their plastids and their pigment concentrations varied. Etio-chloroplasts with prolamellar bodies (PLBs) and prothylakoids with developing grana were observed in the innermost leaves. Besides the above-mentioned Pchlide forms, the middle and innnermost leaf primordia contained only a Chl band with an emission maximum at 686 nm. The outermost leaf primordia contained etio-chloroplasts with well-developed grana and small, narrow-type PLBs. These outermost leaves contained only chlorophyll forms like the mature green leaves. No Pchlide accumulation was observed after bud break, indicating that etiolation of the innermost and middle leaves is transient. The Pchlide forms and the plastid types of the primordia in buds grown in nature were similar to those of leaves of dark-germinated seedlings and to those of the leaf primordia of dark-forced buds. We conclude that transient etiolation occurs under natural conditions. The formation of PLBs and etio-chloroplasts and the accumulation of the light-dependent NADPH:protochlorophyllide oxidoreductase are involved in the natural greening process and ontogenesis of young leaf primordia of horse chestnut buds.

Pore-scale supercritical CO2 dissolution and mass transfer under imbibition conditions

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

Chang, Chun; Zhou, Quanlin; Kneafsey, Timothy J.

2016-06-01

In modeling of geological carbon storage, dissolution of supercritical CO2 (scCO2) is often assumed to be instantaneous with equilibrium phase partitioning. In contrast, recent core-scale imbibition experiments have shown a prolonged depletion of residual scCO2 by dissolution, implying a non-equilibrium mechanism. In this study, eight pore-scale scCO2 dissolution experiments in a 2D heterogeneous, sandstone-analogue micromodel were conducted at supercritical conditions (9 MPa and 40 °C). The micromodel was first saturated with deionized (DI) water and drained by injecting scCO2 to establish a stable scCO2 saturation. DI water was then injected at constant flow rates after scCO2 drainage was completed. Highmore » resolution time-lapse images of scCO2 and water distributions were obtained during imbibition and dissolution, aided by a scCO2-soluble fluorescent dye introduced with scCO2 during drainage. These images were used to estimate scCO2 saturations and scCO2 depletion rates. Experimental results show that (1) a time-independent, varying number of water-flow channels are created during imbibition and later dominant dissolution by the random nature of water flow at the micromodel inlet, and (2) a time-dependent number of water-flow channels are created by coupled imbibition and dissolution following completion of dominant imbibition. The number of water-flow paths, constant or transient in nature, greatly affects the overall depletion rate of scCO2 by dissolution. The average mass fraction of dissolved CO2 (dsCO2) in water effluent varies from 0.38% to 2.72% of CO2 solubility, indicating non-equilibrium scCO2 dissolution in the millimeter-scale pore network. In general, the transient depletion rate decreases as trapped, discontinuous scCO2 bubbles and clusters within water-flow paths dissolve, then remains low with dissolution of large bypassed scCO2 clusters at their interfaces with longitudinal water flow, and finally increases with coupled transverse water flow and enhanced dissolution of large scCO2 clusters. The three stages of scCO2 depletion, common to experiments with time-independent water-flow paths, are revealed by zoom-in image analysis of individual scCO2 bubbles and clusters. The measured relative permeability of water, affected by scCO2 dissolution and bi-modal permeability, shows a non-monotonic dependence on saturation. The results for experiments with different injection rates imply that the non-equilibrium nature of scCO2 dissolution becomes less important when water flow is relatively low and the time scale for dissolution is large, and more pronounced when heterogeneity is strong.« less

Using "Big Data" in a Classroom Setting for Student-Developed Projects

NASA Astrophysics Data System (ADS)

Hayes-Gehrke, Melissa; Vogel, Stuart N.

2018-01-01

The advances in exploration of the optical transient sky anticipated with major facilities such as the Zwicky Transient Facility (ZTF) and Large Synoptic Survey Telescope (LSST) provide an opportunity to integrate large public research datasets into the undergraduate classroom. As a step in this direction, the NSF PIRE-funded GROWTH (Global Relay of Observatories Watching Transients Happen) collaboration provided funding for curriculum development using data from the precursor to ZTF, the Intermediate Palomar Transient Factory (iPTF). One of the iPTF portals, the PTF Variable Marshal, was used by 56 Astronomy majors in the fall 2016 and 2017 semesters of the required Observational Astronomy course at the University of Maryland. Student teams learned about the iPTF survey and how to use the PTF Variable Marshal and then developed their own hypotheses about variable stars to test using data they gathered from the Variable Marshal. Through this project, students gained experience in how to develop scientific questions that can be explored using large datasets and became aware of the limitations and difficulties of such projects. This work was supported in part by NSF award OISE-1545949.

Some TEM observations of Al2O3 scales formed on NiCrAl alloys

NASA Technical Reports Server (NTRS)

Smialek, J.; Gibala, R.

1979-01-01

The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

A space-based classification system for RF transients

NASA Astrophysics Data System (ADS)

Moore, K. R.; Call, D.; Johnson, S.; Payne, T.; Ford, W.; Spencer, K.; Wilkerson, J. F.; Baumgart, C.

The FORTE (Fast On-Orbit Recording of Transient Events) small satellite is scheduled for launch in mid 1995. The mission is to measure and classify VHF (30-300 MHz) electromagnetic pulses, primarily due to lightning, within a high noise environment dominated by continuous wave carriers such as TV and FM stations. The FORTE Event Classifier will use specialized hardware to implement signal processing and neural network algorithms that perform onboard classification of RF transients and carriers. Lightning events will also be characterized with optical data telemetered to the ground. A primary mission science goal is to develop a comprehensive understanding of the correlation between the optical flash and the VHF emissions from lightning. By combining FORTE measurements with ground measurements and/or active transmitters, other science issues can be addressed. Examples include the correlation of global precipitation rates with lightning flash rates and location, the effects of large scale structures within the ionosphere (such as traveling ionospheric disturbances and horizontal gradients in the total electron content) on the propagation of broad bandwidth RF signals, and various areas of lightning physics. Event classification is a key feature of the FORTE mission. Neural networks are promising candidates for this application. The authors describe the proposed FORTE Event Classifier flight system, which consists of a commercially available digital signal processing board and a custom board, and discuss work on signal processing and neural network algorithms.

Transient effects of sudden changes of heat load in a naturally ventilated room

NASA Astrophysics Data System (ADS)

Caulfield, C. P.; Bower, D. J.; Fitzgerald, S.; Woods, A. W.

2006-11-01

Using reduced numerical models and small-scale laboratory experiments, we investigate the transient effects of changing isolated heat loads discontinuously within a large, ventilated space. We consider the emptying filling box (with high and low openings) driven by a single isolated source of buoyancy. The original steady state consists of a buoyant layer, whose depth (for the simplest case of a point source plume) is determined by the geometric properties of the room alone. When the buoyancy flux of the source is increased, a new layer `fills' the room from the top with a more buoyant layer. The original layer disappears due to entrainment by the rising plume. The behaviour is qualitatively different when the source buoyancy flux is decreased. In this case, the rising plume fluid is now relatively dense, and so it inevitably collapses back to `intrude' below the original layer. In this case, the original layer disappears due to both draining through the upper opening, and penetrative entrainment by the dense plume. We compare the predictions of three numerical models using different penetrative entrainment parametrizations to a sequence of laboratory experiments. This entrainment reduces the density of the intruding layer, and so the rising plume eventually stalls, and no longer reaches the (draining) original layer. We demonstrate that it is necessary to consider the transient effects of penetrative entrainment when the reduction in source buoyancy flux is sufficiently small.

Cortical travelling waves: mechanisms and computational principles

PubMed Central

Muller, Lyle; Chavane, Frédéric; Reynolds, John

2018-01-01

Multichannel recording technologies have revealed travelling waves of neural activity in multiple sensory, motor and cognitive systems. These waves can be spontaneously generated by recurrent circuits or evoked by external stimuli. They travel along brain networks at multiple scales, transiently modulating spiking and excitability as they pass. Here, we review recent experimental findings that have found evidence for travelling waves at single-area (mesoscopic) and whole-brain (macroscopic) scales. We place these findings in the context of the current theoretical understanding of wave generation and propagation in recurrent networks. During the large low-frequency rhythms of sleep or the relatively desynchronized state of the awake cortex, travelling waves may serve a variety of functions, from long-term memory consolidation to processing of dynamic visual stimuli. We explore new avenues for experimental and computational understanding of the role of spatiotemporal activity patterns in the cortex. PMID:29563572

Observation of Exciton-Exciton Interaction Mediated Valley Depolarization in Monolayer MoSe2.

PubMed

Mahmood, Fahad; Alpichshev, Zhanybek; Lee, Yi-Hsien; Kong, Jing; Gedik, Nuh

2018-01-10

The valley pseudospin in monolayer transition metal dichalcogenides (TMDs) has been proposed as a new way to manipulate information in various optoelectronic devices. This relies on a large valley polarization that remains stable over long time scales (hundreds of nanoseconds). However, time-resolved measurements report valley lifetimes of only a few picoseconds. This has been attributed to mechanisms such as phonon-mediated intervalley scattering and a precession of the valley pseudospin through electron-hole exchange. Here we use transient spin grating to directly measure the valley depolarization lifetime in monolayer MoSe 2 . We find a fast valley decay rate that scales linearly with the excitation density at different temperatures. This establishes the presence of strong exciton-exciton Coulomb exchange interactions enhancing the valley depolarization. Our work highlights the microscopic processes inhibiting the efficient use of the exciton valley pseudospin in monolayer TMDs.

Terminal Transient Phase of Chaotic Transients

NASA Astrophysics Data System (ADS)

Lilienkamp, Thomas; Parlitz, Ulrich

2018-03-01

Transient chaos in spatially extended systems can be characterized by the length of the transient phase, which typically grows quickly with the system size (supertransients). For a large class of these systems, the chaotic phase terminates abruptly, without any obvious precursors in commonly used observables. Here we investigate transient spatiotemporal chaos in two different models of this class. By probing the state space using perturbed trajectories we show the existence of a "terminal transient phase," which occurs prior to the abrupt collapse of chaotic dynamics. During this phase the impact of perturbations is significantly different from the earlier transient and particular patterns of (non)susceptible regions in state space occur close to the chaotic trajectories. We therefore hypothesize that even without perturbations proper precursors for the collapse of chaotic transients exist, which might be highly relevant for coping with spatiotemporal chaos in cardiac arrhythmias or brain functionality, for example.

Assessment of the TRACE Reactor Analysis Code Against Selected PANDA Transient Data

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

Zavisca, M.; Ghaderi, M.; Khatib-Rahbar, M.

2006-07-01

The TRACE (TRAC/RELAP Advanced Computational Engine) code is an advanced, best-estimate thermal-hydraulic program intended to simulate the transient behavior of light-water reactor systems, using a two-fluid (steam and water, with non-condensable gas), seven-equation representation of the conservation equations and flow-regime dependent constitutive relations in a component-based model with one-, two-, or three-dimensional elements, as well as solid heat structures and logical elements for the control system. The U.S. Nuclear Regulatory Commission is currently supporting the development of the TRACE code and its assessment against a variety of experimental data pertinent to existing and evolutionary reactor designs. This paper presents themore » results of TRACE post-test prediction of P-series of experiments (i.e., tests comprising the ISP-42 blind and open phases) conducted at the PANDA large-scale test facility in 1990's. These results show reasonable agreement with the reported test results, indicating good performance of the code and relevant underlying thermal-hydraulic and heat transfer models. (authors)« less

Stability of fluctuating and transient aggregates of amphiphilic solutes in aqueous binary mixtures: Studies of dimethylsulfoxide, ethanol, and tert-butyl alcohol

NASA Astrophysics Data System (ADS)

Banerjee, Saikat; Bagchi, Biman

2013-10-01

In aqueous binary mixtures, amphiphilic solutes such as dimethylsulfoxide (DMSO), ethanol, tert-butyl alcohol (TBA), etc., are known to form aggregates (or large clusters) at small to intermediate solute concentrations. These aggregates are transient in nature. Although the system remains homogeneous on macroscopic length and time scales, the microheterogeneous aggregation may profoundly affect the properties of the mixture in several distinct ways, particularly if the survival times of the aggregates are longer than density relaxation times of the binary liquid. Here we propose a theoretical scheme to quantify the lifetime and thus the stability of these microheterogeneous clusters, and apply the scheme to calculate the same for water-ethanol, water-DMSO, and water-TBA mixtures. We show that the lifetime of these clusters can range from less than a picosecond (ps) for ethanol clusters to few tens of ps for DMSO and TBA clusters. This helps explaining the absence of a strong composition dependent anomaly in water-ethanol mixtures but the presence of the same in water-DMSO and water-TBA mixtures.

On Parallelizing Single Dynamic Simulation Using HPC Techniques and APIs of Commercial Software

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

Diao, Ruisheng; Jin, Shuangshuang; Howell, Frederic

Time-domain simulations are heavily used in today’s planning and operation practices to assess power system transient stability and post-transient voltage/frequency profiles following severe contingencies to comply with industry standards. Because of the increased modeling complexity, it is several times slower than real time for state-of-the-art commercial packages to complete a dynamic simulation for a large-scale model. With the growing stochastic behavior introduced by emerging technologies, power industry has seen a growing need for performing security assessment in real time. This paper presents a parallel implementation framework to speed up a single dynamic simulation by leveraging the existing stability model librarymore » in commercial tools through their application programming interfaces (APIs). Several high performance computing (HPC) techniques are explored such as parallelizing the calculation of generator current injection, identifying fast linear solvers for network solution, and parallelizing data outputs when interacting with APIs in the commercial package, TSAT. The proposed method has been tested on a WECC planning base case with detailed synchronous generator models and exhibits outstanding scalable performance with sufficient accuracy.« less

Non-Equilibrium Turbulence and Two-Equation Modeling

NASA Technical Reports Server (NTRS)

Rubinstein, Robert

2011-01-01

Two-equation turbulence models are analyzed from the perspective of spectral closure theories. Kolmogorov theory provides useful information for models, but it is limited to equilibrium conditions in which the energy spectrum has relaxed to a steady state consistent with the forcing at large scales; it does not describe transient evolution between such states. Transient evolution is necessarily through nonequilibrium states, which can only be found from a theory of turbulence evolution, such as one provided by a spectral closure. When the departure from equilibrium is small, perturbation theory can be used to approximate the evolution by a two-equation model. The perturbation theory also gives explicit conditions under which this model can be valid, and when it will fail. Implications of the non-equilibrium corrections for the classic Tennekes-Lumley balance in the dissipation rate equation are drawn: it is possible to establish both the cancellation of the leading order Re1/2 divergent contributions to vortex stretching and enstrophy destruction, and the existence of a nonzero difference which is finite in the limit of infinite Reynolds number.

Molecular modeling study of the induced-fit effect on kinase inhibition: the case of fibroblast growth factor receptor 3 (FGFR3)

NASA Astrophysics Data System (ADS)

Li, Yan; Delamar, Michel; Busca, Patricia; Prestat, Guillaume; Le Corre, Laurent; Legeai-Mallet, Laurence; Hu, RongJing; Zhang, Ruisheng; Barbault, Florent

2015-07-01

Tyrosine kinases are a wide family of targets with strong pharmacological relevance. These proteins undergo large-scale conformational motions able to inactivate them. By the end of one of these structural processes, a new cavity is opened allowing the access to a specific type of inhibitors, called type II. The kinase domain of fibroblast growth factor receptor 3 (FGFR3) falls into this family of kinases. We describe here, for the first time, its inactivation process through target molecular dynamics. The transient cavity, at the crossroad between the DFGout and Cα helix out inactivation is herein explored. Molecular docking calculations of known ligands demonstrated that type II inhibitors are able to interact with this metastable transient conformation of FGFR3 kinase. Besides, supplemental computations were conducted and clearly show that type II inhibitors drive the kinase inactivation process through specific stabilization with the DFG triad. This induced-fit effect of type II ligands toward FGFR3 might be extrapolated to other kinase systems and provides meaningful structural information for future drug developments.

Flow path oscillations in transient ground-water simulations of large peatland systems

USGS Publications Warehouse

Reeve, A.S.; Evensen, R.; Glaser, P.H.; Siegel, D.I.; Rosenberry, D.

2006-01-01

Transient numerical simulations of the Glacial Lake Agassiz Peatland near the Red Lakes in Northern Minnesota were constructed to evaluate observed reversals in vertical ground-water flow. Seasonal weather changes were introduced to a ground-water flow model by varying evapotranspiration and recharge over time. Vertical hydraulic reversals, driven by changes in recharge and evapotranspiration were produced in the simulated peat layer. These simulations indicate that the high specific storage associated with the peat is an important control on hydraulic reversals. Seasonally driven vertical flow is on the order of centimeters in the deep peat, suggesting that seasonal vertical advective fluxes are not significant and that ground-water flow into the deep peat likely occurs on decadal or longer time scales. Particles tracked within the ground-water flow model oscillate over time, suggesting that seasonal flow reversals will enhance vertical mixing in the peat column. The amplitude of flow path oscillations increased with increasing peat storativity, with amplitudes of about 5 cm occurring when peat specific storativity was set to about 0.05 m-1. ?? 2005 Elsevier B.V. All rights reserved.

Transient state kinetics tutorial using the kinetics simulation program, KINSIM.

PubMed Central

Wachsstock, D H; Pollard, T D

1994-01-01

This article provides an introduction to a computer tutorial on transient state kinetics. The tutorial uses our Macintosh version of the computer program, KINSIM, that calculates the time course of reactions. KINSIM is also available for other popular computers. This program allows even those investigators not mathematically inclined to evaluate the rate constants for the transitions between the intermediates in any reaction mechanism. These rate constants are one of the insights that are essential for understanding how biochemical processes work at the molecular level. The approach is applicable not only to enzyme reactions but also to any other type of process of interest to biophysicists, cell biologists, and molecular biologists in which concentrations change with time. In principle, the same methods could be used to characterize time-dependent, large-scale processes in ecology and evolution. Completion of the tutorial takes students 6-10 h. This investment is rewarded by a deep understanding of the principles of chemical kinetics and familiarity with the tools of kinetics simulation as an approach to solve everyday problems in the laboratory. PMID:7811941

Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

NASA Astrophysics Data System (ADS)

Lim, Sungkeun

Gordon Moore famously predicted the exponential increase in transistor integration and computing power that has been witnessed in recent decades [1]. In the near future, it is expected that more than one billion transistors will be integrated per chip, and advanced microprocessors will require clock speeds in excess of several GHz. The increasing number of transistors and high clock speeds will necessitate the consumption of more power. By 2014, it is expected that the maximum power consumption of the microprocessor will reach approximately 150W, and the maximum load current will be around 150A. Today's trend in power and thermal management is to reduce supply voltage as low as possible to reduce delivered power. It is anticipated that the Intel cores will operate on 0.8V of supply voltage by 2014 [2]. A significant challenge in Voltage Regulator Module (VRM) development for next generation microprocessors is to regulate the supply voltage within a certain tolerance band during high slew rate load transitions, since the required supply voltage tolerance band will be much narrower than the current requirement. If VR output impedance is maintained at a constant value from DC to high frequency, large output voltage spikes can be avoided during load cur- rent transients. Based on this, the Adaptive Voltage Position (AVP) concept was developed to achieve constant VR output impedance to improve transient response performance [3]. However, the VR output impedance can not be made constant over the entire frequency range with AVP design, because the AVP design makes the VR output impedance constant only at low frequencies. To make the output impedance constant at high frequencies, many bulk capacitors and ceramic capacitors are required. The tight supply voltage tolerance for the next generation of microprocessors during high slew rate load transitions requires fast transient response power supplies. A VRM can not follow the high slew rate load current transients, because of the slow inductor current slew rate which is determined by the input voltage, output voltage, and the inductance. The remaining inductor current in the power delivery path will charge the output capacitors and develop a voltage across the ESR. As a result, large output voltage spikes occur during load current transients. Due to their limited control bandwidth, traditional VRs can not sufficiently respond rapidly to certain load transients. As a result, a large output voltage spike can occur during load transients, hence requiring a large amount of bulk capacitance to decouple the VR from the load [2]. If the remaining inductor current is removed from the power stage or the inductor current slew rate is changed, the output voltage spikes can be clamped, allowing the output capacitance to be reduced. A new design methodology for a Transient Performance Improvement Circuit(TPIC) based on controlling the output impedance of a regulator is presented. The TPIC works in parallel with a voltage regulator (VR)'s ceramic capacitors to achieve faster voltage regulation without the need for a large bulk capacitance, and can serve as a replacement for bulk capacitors. The specific function of the TPIC is to mimic the behavior of the bulk capacitance in a traditional VRM by sinking and sourcing large currents during transients, allowing the VR to respond quickly to current transients without the need for a large bulk capacitance. This will allow fast transient response without the need for a large bulk capacitor. The main challenge in applying the TPIC is creating a design which will not interfere with VR operation. A TPIC for a 4 Switch Buck-Boost (4SBB) converter is presented which functions by con- trolling the inductor current slew rate during load current transients. By increasing the inductor current slew rate, the remaining inductor current can be removed from the 4SBB power delivery path and the output voltage spike can be clamped. A second TPIC is presented which is designed to improve the performance of an LDO regulator during output current transients. A TPIC for a LDO regulator is proposed to reduce the over voltage spike settling time. During a load current step down transient, the only current discharging path is a light load current. However, it takes a long time to discharge the current charged in the output capacitors with the light load current. The proposed TPIC will make an additional current discharging path to reduce the long settling time. By reducing the settling time, the load current transient frequency of the LDO regulator can be increased. A Ripple Cancellation Circuit (RCC) is proposed to reduce the output voltage ripple. The RCC has a very similar concept with the TPIC which is sinking or injecting additional current to the power stage to compensate the inductor ripple current. The proposed TPICs and RCC have been implemented with a 0.6m CMOS process. A single-phase VR, a 4SBB converter, and a LDO regulator have been utilized with the proposed TPIC to evaluate its performance. The theoretical analysis will be confirmed by Cadence simulation results and experimental results.

Asteroid entry in Venusian atmosphere: Pressure and density fields effect on crater formation

NASA Technical Reports Server (NTRS)

Schmidt, Robert

1995-01-01

The objectives are to look at time scales of overpressure compared to cratering and to determine: what are the transient pressure and density due to atmospheric entry; do shock waves evacuate ambient gas; do transient atmospheric disturbances 'settle down' during cratering; can the pressure/density field be approximated as quasi-static; how does disturbance scale with impactor size; and what is the role of atmospheric thickness. The general approach is to perform inexpensive exploratory calculations, perform experiments to validate code and observe crater growth, and to follow up with more realistic coupling calculations. This viewgraph presentation presents progress made with the objective to obtain useful scaling relationships for crater formation when atmospheric effects are important.

Observations of Seafloor Roughness in a Tidally Modulated Inlet

NASA Astrophysics Data System (ADS)

Lippmann, T. C.; Hunt, J.

2014-12-01

The vertical structure of shallow water flows are influenced by the presence of a bottom boundary layer, which spans the water column for long period waves or mean flows. The nature of the boundary is determined in part by the roughness elements that make up the seafloor, and includes sometimes complex undulations associated with regular and irregular shaped bedforms whose scales range several orders of magnitude from orbital wave ripples (10-1 m) to mega-ripples (100 m) and even larger features (101-103) such as sand waves, bars, and dunes. Modeling efforts often parameterize the effects of roughness elements on flow fields, depending on the complexity of the boundary layer formulations. The problem is exacerbated by the transient nature of bedforms and their large spatial extent and variability. This is particularly important in high flow areas with large sediment transport, such as tidally dominated sandy inlets like New River Inlet, NC. Quantification of small scale seafloor variability over large spatial areas requires the use of mobile platforms that can measure with fine scale (order cm) accuracy in wide swaths. The problem is difficult in shallow water where waves and currents are large, and water clarity is often limited. In this work, we present results from bathymetric surveys obtained with the Coastal Bathymetry Survey System, a personal watercraft equipped with a Imagenex multibeam acoustic echosounder and Applanix POS-MV 320 GPS-aided inertial measurement unit. This system is able to measure shallow water seafloor bathymetry and backscatter intensity with very fine scale (10-1 m) resolution and over relatively large scales (103 m) in the presence of high waves and currents. Wavenumber spectra show that the noise floor of the resolved multibeam bathymetry is on the order of 2.5 - 5 cm in amplitude, depending on water depths ranging 2 - 6 m, and about 30 cm in wavelength. Seafloor roughness elements are estimated from wavenumber spectra across the inlet from bathymetric maps of the seafloor obtained with 10-25 cm horizontal resolution. Implications of the effects of the bottom variability on the vertical structure of the currents will be discussed. This work was supported by ONR and NOAA.

Intermountain Cyclogenesis: a Climatology and Multiscale Case Studies

NASA Astrophysics Data System (ADS)

Lee, Tiros Peijiun

1995-11-01

A detailed study of Intermountain cyclones over the western United States is conducted through climatological and case studies. An eleven-year (1976-1986) statistical survey shows that the Nevada cyclogenesis is mainly a springtime (March, April) event while a secondary maximum of cyclogenesis frequency is found in November. Nearly 75% of the Nevada cyclogenesis events (177 out of 237 cases) take place under large-scale westerly to southerly flow aloft across the Sierra Nevada Mountains, while 24% of the events (57 out of 237 cases) occur under northwesterly flow aloft. A composite study of these two types of the flow is shown to demonstrate how differences in large-scale topography affect Intermountain cyclogenesis processes. The result from a case study of 9-11 February 1984 reveals that an antecedent Nevada lee trough formed as a result of large-scale southwesterly flow aloft interacting with the underlying terrain well before the surface and upper-level troughs moved onshore. Subsequent cyclogenesis took place in situ with the axis of the trough as the center of large-scale quasi-geostrophic ascent/positive potential vorticity advection began to spread across the Sierra Nevada Mountains. As the cyclone moved downstream, it was observed to weaken well before reaching the Continental Divide while a new cyclonic development occurred east of the Rocky Mountains. It is shown that the weakening of the Intermountain cyclone was associated with the ongoing interaction between the Intermountain cyclone and large-scale topography and the progressive outrunning of the large-scale dynamical forcing aloft away from the surface cyclone center. An investigation of the large-scale evolution for the 26-29 January 1980 case, which developed beneath the northwesterly flow aloft, further reveals that the underlying topography plays two major roles in contributing to the initial cyclogenesis: (1) to block and to retard cold, stable air east of the Continental Divide from rushing into the Great Basin region, and (2) to produce differential pressure falls across the Sierra Nevada Mountains (more along the eastern slopes) in response to increasing cross -mountain flow. Numerous transient shortwaves in the midtroposphere rapidly move across the GB and the Rocky Mountains into the Plains States, while the Intermountain cyclone moves slower than to the disturbances aloft. There is no downstream lee trough/cyclogenesis to the east of the Rockies during the investigation period since the leeside is characterized by cold, stable air. The third case study is made of an 11-14 December 1987 Intermountain cyclogenesis case which took place in an area of relatively warm and less stable environment near the Arizona-New Mexico border beneath northwesterly flow aloft. The ensuing interaction between the large -scale flow and underlying terrain allowed the surface cyclone to remain quasi-stationary for its entire 36 h life span. We also document a cold-season small-scale Catalina eddy development in the coastal southern California waters in this case. The eddy formed as the equatorward and northeasterly flow upstream of the coastal (San Rafael and Saint Ynez) mountains increased in the lower troposphere. Weak large-scale ascent in the mid- and upper-troposphere over the incipient eddy environment provided evidence of the orographic nature of the small -scale cyclone. The eddy was eventually displaced seaward and weakened with the arrival of powerful large-scale subsidence and increasing northeasterly downslope flow at the lower levels that reached the coastal waters.

Convolutional neural networks for transient candidate vetting in large-scale surveys

NASA Astrophysics Data System (ADS)

Gieseke, Fabian; Bloemen, Steven; van den Bogaard, Cas; Heskes, Tom; Kindler, Jonas; Scalzo, Richard A.; Ribeiro, Valério A. R. M.; van Roestel, Jan; Groot, Paul J.; Yuan, Fang; Möller, Anais; Tucker, Brad E.

2017-12-01

Current synoptic sky surveys monitor large areas of the sky to find variable and transient astronomical sources. As the number of detections per night at a single telescope easily exceeds several thousand, current detection pipelines make intensive use of machine learning algorithms to classify the detected objects and to filter out the most interesting candidates. A number of upcoming surveys will produce up to three orders of magnitude more data, which renders high-precision classification systems essential to reduce the manual and, hence, expensive vetting by human experts. We present an approach based on convolutional neural networks to discriminate between true astrophysical sources and artefacts in reference-subtracted optical images. We show that relatively simple networks are already competitive with state-of-the-art systems and that their quality can further be improved via slightly deeper networks and additional pre-processing steps - eventually yielding models outperforming state-of-the-art systems. In particular, our best model correctly classifies about 97.3 per cent of all 'real' and 99.7 per cent of all 'bogus' instances on a test set containing 1942 'bogus' and 227 'real' instances in total. Furthermore, the networks considered in this work can also successfully classify these objects at hand without relying on difference images, which might pave the way for future detection pipelines not containing image subtraction steps at all.

Revealing the cascade of slow transients behind a large slow slip event

NASA Astrophysics Data System (ADS)

Frank, W.; Rousset, B.; Lasserre, C.; Campillo, M.

2017-12-01

Capable of reaching similar magnitudes to large megathrust earthquakes (Mw > 7), slow slip events play a major role in accommodating tectonic motion on plate boundaries. These slip transients are the slow release of built-up tectonic stress that are geodetically imaged as a predominantly aseismic rupture, which is smooth in both time and space. We demonstrate here that large slow slip events are in fact a complex cascade of short-duration slow transients. Using a dense catalog of low-frequency earthquakes as a guide, we investigate the Mw 7.5 slow slip event that occurred in 2006 along the subduction interface 40 km beneath Guerrero, Mexico. We show that while the long-period surface displacement as recorded by GPS suggests a six month duration, motion in the direction of tectonic release only sporadically occurs over 55 days and its surface signature is attenuated by rapid relocking of the plate interface. These results demonstrate that our current conceptual model of slow and continuous rupture is an artifact of low-resolution geodetic observations of a superposition of small, clustered slip events. Our proposed description of slow slip as a cascade of slow transients implies that we systematically overestimate the duration T and underestimate the moment magnitude M of large slow slip events.

On transient events in the upper atmosphere generated away of thunderstorm regions

NASA Astrophysics Data System (ADS)

Morozenko, V.; Garipov, G.; Khrenov, B.; Klimov, P.; Panasyuk, M.; Sharakin, S.; Zotov, M.

2011-12-01

Experimental data on transient events in UV and Red-IR ranges obtained in the MSU missions "Unversitetsky-Tatiana" (wavelengths 300-400 nm) and "Unversitetsky-Tatiana-2" (wavelengths 300-400 nm and 600-800 nm), published by Garipov et al, in 2010 at COSPAR session http://www.cospar2010.org, at TEPA conference http://www.aragats.am/Conferences/tepa2010 and in 2011 by Sadovnichy et al, Solar System Research, 45, #1, 3-29 (2011); Vedenkin et al, JETP, v. 140, issue 3(9), 1-11 (2011) demonstrated existence of transients at large distances (up to thousands km) away of cloud thunderstorm regions. Those "remote" transients are short (1-5 msec) and are less luminous than the transients above thunderstorm regions. The ratio of Red-IR to UV photon numbers in those transients indicates high altitude of their origin (~70 km). Important observation facts are also: 1. a change of the exponent in transient distribution on luminosity Q ("-1" for photon numbers Q=1020 -1023 to "-2" for Q>1023), 2. a change of global distribution of transient with their luminosity (transients with Q>1023 are concentrated in equatorial range above continents, while transients with low luminosity are distributed more uniformly), 3. a phenomenon of transient sequences in one satellite orbit which is close to geomagnetic meridian. In the present paper phenomenological features of transients are explained in assumption that the observed transients have to be divided in two classes: 1. transients related to local, lower in the atmosphere, lightning at distance not more than hundreds km from satellite detector field of view in the atmosphere and 2. transients generated by far away lightning. Local transients are luminous and presumably are events called "transient luminous events" (TLE). In distribution on luminosity those events have some threshold Q~1023 and their differential luminosity distribution is approximated by power law exponent "-2". Remote transients have to be considered separately. Their origin may be related to electromagnetic pulses (EMP) or waves (whistler, EMW) generated by lightning. The EMP-EMW is transmitted in the ionosphere- ground channel to large distances R with low absorption. The part of EMP-EMW "visible" in the detector aperture diminishes with distance as R-1 due to observation geometry. The EMP-EMW triggers the electric discharge in the upper atmosphere (lower ionosphere, ~70 km). Estimates of resulting transients luminosity and their correlation with geomagnetic field are in progress.

Transient severe left ventricular dysfunction following percutaneous patent ductus arteriosus closure in an adult with bicuspid aortic valve: A case report

PubMed Central

HWANG, HUI-JEONG; YOON, KYUNG LIM; SOHN, IL SUK

2016-01-01

The present study reported the case of a 60-year-old female with patent ductus arteriosus (PDA) and a bicuspid aortic valve, who presented with transient severe left ventricular (LV) dysfunction following percutaneous closure of PDA, as identified by speckle tracking analysis. Transient LV dysfunction following PDA closure has previously been reported; however, severe LV dysfunction is rare. In the present case, the combination of a large PDA size, large amount of shunting, LV remodeling and bicuspid aortic valve may have induced serious deterioration of LV function following PDA closure. Furthermore, speckle-tracking echocardiography may be useful in the estimation of functional alterations in the myocardium of the LV following PDA closure. The observations detailed in the present study may improve the understanding of the pathophysiology and myocardial patterns of transient left ventricular dysfunction following PDA closure in adult humans. PMID:26998021

Transient severe left ventricular dysfunction following percutaneous patent ductus arteriosus closure in an adult with bicuspid aortic valve: A case report.

PubMed

Hwang, Hui-Jeong; Yoon, Kyung Lim; Sohn, Il Suk

2016-03-01

The present study reported the case of a 60-year-old female with patent ductus arteriosus (PDA) and a bicuspid aortic valve, who presented with transient severe left ventricular (LV) dysfunction following percutaneous closure of PDA, as identified by speckle tracking analysis. Transient LV dysfunction following PDA closure has previously been reported; however, severe LV dysfunction is rare. In the present case, the combination of a large PDA size, large amount of shunting, LV remodeling and bicuspid aortic valve may have induced serious deterioration of LV function following PDA closure. Furthermore, speckle-tracking echocardiography may be useful in the estimation of functional alterations in the myocardium of the LV following PDA closure. The observations detailed in the present study may improve the understanding of the pathophysiology and myocardial patterns of transient left ventricular dysfunction following PDA closure in adult humans.

TRANSIENT BEAM LOADING EFFECTS IN RF SYSTEMS IN JLEIC

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

Wang, Haipeng; Guo, Jiquan; Rimmer, Robert A.

2016-05-01

The pulsed electron bunch trains generated from the Continuous Electron Beam Accelerator Facility (CEBAF) linac to inject into the proposed Jefferson Lab Electron Ion Collider (JLEIC) e-ring will produce transient beam loading effects in the Superconducting Radio Frequency (SRF) systems that, if not mitigated, could cause unacceptably large beam energy deviation in the injection capture, or exceed the energy acceptance of CEBAF’s recirculating arcs. In the electron storage ring, the beam abort or ion clearing gaps or uneven bucket filling can cause large beam phase transients in the (S)RF cavity control systems and even beam loss due to Robinson instability.more » We have first analysed the beam stability criteria in steady state and estimated the transient effect in Feedforward and Feedback RF controls. Initial analytical models for these effects are shown for the design of the JLEIC e-ring from 3GeV to 12GeV.« less

Repeating Earthquake and Nonvolcanic Tremor Observations of Aseismic Deep Fault Transients in Central California.

NASA Astrophysics Data System (ADS)

Nadeau, R. M.; Traer, M.; Guilhem, A.

2005-12-01

Seismic indicators of fault zone deformation can complement geodetic measurements by providing information on aseismic transient deformation: 1) from deep within the fault zone, 2) on a regional scale, 3) with intermediate temporal resolution (weeks to months) and 4) that spans over 2 decades (1984 to early 2005), including pre- GPS and INSAR coverage. Along the San Andreas Fault (SAF) in central California, two types of seismic indicators are proving to be particularly useful for providing information on deep fault zone deformation. The first, characteristically repeating microearthquakes, provide long-term coverage (decades) on the evolution of aseismic fault slip rates at seismogenic depths along a large (~175 km) stretch of the SAF between the rupture zones of the ~M8 1906 San Francisco and 1857 Fort Tejon earthquakes. In Cascadia and Japan the second type of seismic indicator, nonvolcanic tremors, have shown a remarkable correlation between their activity rates and GPS and tiltmeter measurements of transient deformation in the deep (sub-seismogenic) fault zone. This correlation suggests that tremor rate changes and deep transient deformation are intimately related and that deformation associated with the tremor activity may be stressing the seismogenic zone in both areas. Along the SAF, nonvolcanic tremors have only recently been discovered (i.e., in the Parkfield-Cholame area), and knowledge of their full spatial extent is still relatively limited. Nonetheless the observed temporal correlation between earthquake and tremor activity in this area is consistent with a model in which sub-seismogenic deformation and seismogenic zone stress changes are closely related. We present observations of deep aseismic transient deformation associated with the 28 September 2004, M6 Parkfield earthquake from both repeating earthquake and nonvolcanic tremor data. Also presented are updated deep fault slip rate estimates from prepeating quakes in the San Juan Bautista area with an assessment of their significance to previously reported quasi-periodic slip rate pulses and small to moderate magnitude (> M3.5) earthquake occurrence in the area.

Solar influence on climate during the past millennium: Results from transient simulations with the NCAR Climate System Model

PubMed Central

Ammann, Caspar M.; Joos, Fortunat; Schimel, David S.; Otto-Bliesner, Bette L.; Tomas, Robert A.

2007-01-01

The potential role of solar variations in modulating recent climate has been debated for many decades and recent papers suggest that solar forcing may be less than previously believed. Because solar variability before the satellite period must be scaled from proxy data, large uncertainty exists about phase and magnitude of the forcing. We used a coupled climate system model to determine whether proxy-based irradiance series are capable of inducing climatic variations that resemble variations found in climate reconstructions, and if part of the previously estimated large range of past solar irradiance changes could be excluded. Transient simulations, covering the published range of solar irradiance estimates, were integrated from 850 AD to the present. Solar forcing as well as volcanic and anthropogenic forcing are detectable in the model results despite internal variability. The resulting climates are generally consistent with temperature reconstructions. Smaller, rather than larger, long-term trends in solar irradiance appear more plausible and produced modeled climates in better agreement with the range of Northern Hemisphere temperature proxy records both with respect to phase and magnitude. Despite the direct response of the model to solar forcing, even large solar irradiance change combined with realistic volcanic forcing over past centuries could not explain the late 20th century warming without inclusion of greenhouse gas forcing. Although solar and volcanic effects appear to dominate most of the slow climate variations within the past thousand years, the impacts of greenhouse gases have dominated since the second half of the last century. PMID:17360418

Irradiation behaviour of the large grained UO{sub 2} fuel pellet in the transient conditions

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

Kosaka, Yuji; Watanabe, Seiichi; Arakawa, Yasushi

2007-07-01

In order to achieve a high duty fuel rod design, it is the key issue to suppress the fission gas release from the view point of the fuel rod inner pressure design. The large grain UO{sub 2} pellet is one of the candidates to meet such a requirement by reducing the fission gas release especially at high power and/or high burnup. We have demonstrated the fuel performance of the large grain pellet in the PWR irradiation conditions, which was fabricated with no additive but with active UO{sub 2} powder through the conventional pelletizing process for the normal grain size pellet.more » According to the mechanism of the fission gas retention, there may be a concern about the larger gas bubble swelling of the large grain pellet at the power transient conditions which may increase the potential of the PCMI failure. In this paper, we focus on the differences of the dimensional change in comparison among the pellets with the different grain sizes at the power transient conditions. The power ramp tests were carried out on the high burnup fuel rods of normal and large grain pellet with no additive, which had been irradiated in the PWR conditions up to around 60 GWd/t at peak position. The detailed PIE results revealed that the volume increment due to the power ramp clearly showed the dependence on the grain size as well as the fission gas release and suggested that the larger grain with no additive may suppress the gas bubble swelling at the power transient conditions. According to the experimental results, it is concluded that the large grain pellet with no additive does not deteriorate the irradiation performance during the power transient conditions from the view point of the gas bubble swelling. (authors)« less

Physical and chemical controls on ore shoots - insights from 3D modeling of an orogenic gold deposit

NASA Astrophysics Data System (ADS)

Vollgger, S. A.; Tomkins, A. G.; Micklethwaite, S.; Cruden, A. R.; Wilson, C. J. L.

2016-12-01

Many ore deposits have irregular grade distributions with localized elongate and well-mineralized rock volumes commonly referred to as ore shoots. The chemical and physical processes that control ore shoot formation are rarely understood, although transient episodes of elevated permeability are thought to be important within the brittle and brittle-ductile crust, due to faulting and fracturing associated with earthquake-aftershock sequences or earthquake swarms. We present data from an orogenic gold deposit in Australia where the bulk of the gold is contained in abundant fine arsenopyrite crystals associated with a fault-vein network within tight upright folds. The deposit-scale fault network is connected to a deeper network of thrust faults (tens of kilometers long). Using 3D implicit modeling of geochemical data, based on radial basis functions, gold grades and gold-arsenic element ratios were interpolated and related to major faults, vein networks and late intrusions. Additionally, downhole bedding measurements were used to model first order (mine-scale) fold structures. The results show that ore shoot plunges are not parallel with mine-scale or regional fold plunges, and that bedding parallel faults related to flexural slip folding play a pivotal role on ore shoot attitudes. 3D fault slip and dilation tendency analysis indicate that fault reactivation and formation of linking faults are associated with large volumes of high-grade ore. We suggest slip events on the large-scale thrust network allowed mineralizing fluids to rapidly migrate over large distances and become supersaturated in elements such as gold, promoting widespread precipitation and high nucleation densities of arsenopyrite upon fluid-rock interaction at trap sites within the deposit.

Quantifying Km-scale Hydrological Exchange Flows under Dynamic Flows and Their Influences on River Corridor Biogeochemistry

NASA Astrophysics Data System (ADS)

Chen, X.; Song, X.; Shuai, P.; Hammond, G. E.; Ren, H.; Zachara, J. M.

2017-12-01

Hydrologic exchange flows (HEFs) in rivers play vital roles in watershed ecological and biogeochemical functions due to their strong capacity to attenuate contaminants and process significant quantities of carbon and nutrients. While most of existing HEF studies focus on headwater systems with the assumption of steady-state flow, there is lack of understanding of large-scale HEFs in high-order regulated rivers that experience high-frequency stage fluctuations. The large variability of HEFs is a result of interactions between spatial heterogeneity in hydrogeologic properties and temporal variation in river discharge induced by natural or anthropogenic perturbations. Our 9-year spatially distributed dataset (water elevation, specific conductance, and temperature) combined with mechanistic hydrobiogeochemical simulations have revealed complex spatial and temporal dynamics in km-scale HEFs and their significant impacts on contaminant plume mobility and hyporheic biogeochemical processes along the Hanford Reach. Extended multidirectional flow behaviors of unconfined, river corridor groundwater were observed hundreds of meters inland from the river shore resulting from discharge-dependent HEFs. An appropriately sized modeling domain to capture the impact of regional groundwater flow as well as knowledge of subsurface structures controlling intra-aquifer hydrologic connectivity were essential to realistically model transient storage in this large-scale river corridor. This work showed that both river water and mobile groundwater contaminants could serve as effective tracers of HEFs, thus providing valuable information for evaluating and validating the HEF models. Multimodal residence time distributions with long tails were resulted from the mixture of long and short exchange pathways, which consequently impact the carbon and nutrient cycling within the river corridor. Improved understanding of HEFs using integrated observational and modeling approaches sheds light on developing fundamental understanding of the influences of HEFs on water quality, nutrient dynamics, and ecosystem health in dynamic river corridor systems.

Large-scale manufacture and characterization of a lentiviral vector produced for clinical ex vivo gene therapy application.

PubMed

Merten, Otto-Wilhelm; Charrier, Sabine; Laroudie, Nicolas; Fauchille, Sylvain; Dugué, Céline; Jenny, Christine; Audit, Muriel; Zanta-Boussif, Maria-Antonietta; Chautard, Hélène; Radrizzani, Marina; Vallanti, Giuliana; Naldini, Luigi; Noguiez-Hellin, Patricia; Galy, Anne

2011-03-01

From the perspective of a pilot clinical gene therapy trial for Wiskott-Aldrich syndrome (WAS), we implemented a process to produce a lentiviral vector under good manufacturing practices (GMP). The process is based on the transient transfection of 293T cells in Cell Factory stacks, scaled up to harvest 50 liters of viral stock per batch, followed by purification of the vesicular stomatitis virus glycoprotein-pseudotyped particles through several membrane-based and chromatographic steps. The process leads to a 200-fold volume concentration and an approximately 3-log reduction in protein and DNA contaminants. An average yield of 13% of infectious particles was obtained in six full-scale preparations. The final product contained low levels of contaminants such as simian virus 40 large T antigen or E1A sequences originating from producer cells. Titers as high as 2 × 10(9) infectious particles per milliliter were obtained, generating up to 6 × 10(11) infectious particles per batch. The purified WAS vector was biologically active, efficiently expressing the genetic insert in WAS protein-deficient B cell lines and transducing CD34(+) cells. The vector introduced 0.3-1 vector copy per cell on average in CD34(+) cells when used at the concentration of 10(8) infectious particles per milliliter, which is comparable to preclinical preparations. There was no evidence of cellular toxicity. These results show the implementation of large-scale GMP production, purification, and control of advanced HIV-1-derived lentiviral technology. Results obtained with the WAS vector provide the initial manufacturing and quality control benchmarking that should be helpful to further development and clinical applications.

Short-term depression and transient memory in sensory cortex.

PubMed

Gillary, Grant; Heydt, Rüdiger von der; Niebur, Ernst

2017-12-01

Persistent neuronal activity is usually studied in the context of short-term memory localized in central cortical areas. Recent studies show that early sensory areas also can have persistent representations of stimuli which emerge quickly (over tens of milliseconds) and decay slowly (over seconds). Traditional positive feedback models cannot explain sensory persistence for at least two reasons: (i) They show attractor dynamics, with transient perturbations resulting in a quasi-permanent change of system state, whereas sensory systems return to the original state after a transient. (ii) As we show, those positive feedback models which decay to baseline lose their persistence when their recurrent connections are subject to short-term depression, a common property of excitatory connections in early sensory areas. Dual time constant network behavior has also been implemented by nonlinear afferents producing a large transient input followed by much smaller steady state input. We show that such networks require unphysiologically large onset transients to produce the rise and decay observed in sensory areas. Our study explores how memory and persistence can be implemented in another model class, derivative feedback networks. We show that these networks can operate with two vastly different time courses, changing their state quickly when new information is coming in but retaining it for a long time, and that these capabilities are robust to short-term depression. Specifically, derivative feedback networks with short-term depression that acts differentially on positive and negative feedback projections are capable of dynamically changing their time constant, thus allowing fast onset and slow decay of responses without requiring unrealistically large input transients.

Transient-Switch-Signal Suppressor

NASA Technical Reports Server (NTRS)

Bozeman, Richard J., Jr.

1995-01-01

Circuit delays transmission of switch-opening or switch-closing signal until after preset suppression time. Used to prevent transmission of undesired momentary switch signal. Basic mode of operation simple. Beginning of switch signal initiates timing sequence. If switch signal persists after preset suppression time, circuit transmits switch signal to external circuitry. If switch signal no longer present after suppression time, switch signal deemed transient, and circuit does not pass signal on to external circuitry, as though no transient switch signal. Suppression time preset at value large enough to allow for damping of underlying pressure wave or other mechanical transient.

Transient conduction-radiation analysis of an absolute active cavity radiometer using finite elements

NASA Technical Reports Server (NTRS)

Mahan, J. R.; Kowsary, F.; Tira, N.; Gardiner, B. D.

1987-01-01

A NASA-developed finite element-based model of a generic active cavity radiometer (ACR) has been developed in order to study the dependence on operating temperature of the closed-loop and open-loop transient response of the instrument. Transient conduction within the sensing element is explored, and the transient temperature distribution resulting from the application of a time-varying radiative boundary condition is calculated. The results verify the prediction that operation of an ACR at cryogenic temperatures results in large gains in frequency response.

Investigations of an Environmentally Induced Long Duration Hall Thruster Start Transient (PREPRINT)

DTIC Science & Technology

2006-02-06

Hall thruster start transient is produced by exposure of the thruster to ambient laboratory atmosphere. This behavior was first observed during operation of a cluster of four 200 W BHT-200 Hall effect thrusters where large anode discharge fluctuations, visible as increased anode current and a diffuse plume structure, occurred in an apparently random manner. During operation of a single thruster, the start transient appears as a quickly rising and later smoothly decaying elevated anode current with a diffuse plume that persists for less than 500 seconds. The start transient

Femtosecond transient absorption, Raman, and electrochemistry studies of tetrasulfonated copper phthalocyanine in water solutions.

PubMed

Abramczyk, H; Brozek-Płuska, B; Kurczewski, K; Kurczewska, M; Szymczyk, I; Krzyczmonik, P; Błaszczyk, T; Scholl, H; Czajkowski, W

2006-07-20

Ultrafast time-resolved electronic spectra of the primary events induced in the copper tetrasulfonated phthalocyanine Cu(tsPc)4-) in aqueous solution has been measured by femtosecond pump-probe transient absorption spectroscopy. The primary events initiated by the absorption of a photon occurring within the femtosecond time scale are discussed on the basis of the electron transfer mechanism between the adjacent phthalocyanine rings proposed recently in our laboratory. The femtosecond transient absorption results are compared with the low temperature emission spectra obtained with Raman spectroscopy and the voltammetric curves.

Simulations of neutral wind shear effect on the equatorial ionosphere irregularities

NASA Astrophysics Data System (ADS)

Kim, J.; Chagelishvili, G.; Horton, W.

2005-12-01

We present numerical calculations of the large-scale electron density driven by the gradient drift instability in the daytime equatorial electrojet. Under two-fluid theory the linear analysis for kilometer scale waves lead to the result that all the perturbations are transformed to small scales through linear convection by shear and then damped by diffusion. The inclusion of the nonlinearity enables inverse energy cascade to provide energy to long scale. The feedback between velocity shear and nonlinearity keeps waves growing and leads to the turbulence. In strongly turbulent regime, the nonlinear states are saturated [1]. Since the convective nonlinearities are isotropic while the interactions of velocity shear with waves are anisotropic, the feedback do not necessarily enable waves to grow. The growth of waves are highly variable on k-space configuration [2]. Our simulations show that the directional relationship between vorticity of irregularities and shear are one of key factors. Thus during the transient period, the irregularities show the anisotropy of the vorticity power spectrum. We report the evolution of the power spectrum of the vorticity and density of irregularties and its anistropic nature as observed. The work was supported in part by the Department of NSF Grant ATM-0229863 and ISTC Grant G-553. C. Ronchi, R.N. Sudan, and D.T. Farley. Numerical simulations of large-scale plasma turbulece in teh day time equatorial electrojet. J. Geophys. Res., 96:21263--21279, 1991. G.D. Chagelishvili, R.G. Chanishvili, T.S. Hristov, and J.G. Lominadze. A turbulence model in unbounded smooth shear flows : The weak turbulence approach. JETP, 94(2):434--445, 2002.

The Transient High-Energy Sky and Early Universe Surveyor (THESEUS)

NASA Astrophysics Data System (ADS)

Amati, L.

2016-10-01

THESEUS is a mission concept by a large international collaboration aimed at exploiting GRBs for investigating the early universe and at vastly increasing the discovery space of the high energy transient phenomena over the entire cosmic history.

Identification of coronal sources of the solar wind from solar images in the EUV spectral range

NASA Astrophysics Data System (ADS)

Slemzin, V. A.; Shugai, Yu. S.

2015-01-01

Methods of localizing coronal sources of the solar wind (SW), such as coronal holes, quasi-stationary fluxes from active regions, and transient sources associated with small-scale active phenomena are considered based on vacuum-ultraviolet (EUV) images of the corona at low solar activity during the initial period of the 24th solar cycle (2010). It is shown that a SW velocity profile can be calculated from the relative areas of coronal holes (CH) at the central part of the disk based on the images in the ranges of 193 and 171 Å. The images in the 193 Å describe the geometry of large HCs that represent sources of fast SW well. The images in 171 Å are a better visualization of small CHs, based on which the profile of a slow SW component was calculated to a high accuracy (up to 65 km/s). According to Hinode/EIS data of October 15, 2010, using the Doppler spectroscopy method at the streamer base over the active region 11112, the source of the outgoing plasma flux with the mean velocity of 17 km/s was localized in the magnetic field region with an intensity of less than 200 Gauss. According to the estimate, the density of the plasma flux from this source is an order of magnitude greater than the value required for explaining the distinction between the calculated and measured profiles of a slow SW velocity. For finding the transient SW component based on small-scale flare activity, SW parameters were analyzed for the periods of flares accompanied by coronal mass ejections (CMEs), and for the periods without flares, according to the data obtained in 2010 from the ACE and GOES satellites and by coronagraphs on the STEREO-A and - B spacecraft. The ion ratios C+6/C+5 and O+7/O+6 and the mean charge of Fe ions for periods with flares were shown to be shifted toward large values, suggesting the presence of a hot SW component associated with flare activity. A noticeable correlation between the maximum charge of Fe ions and the peak power of a flare, previously observed for flares of a higher class, was confirmed. The mean value of the SW flux density during the periods of flares was 30% higher than that in the periods without flares, which is possibly associated also with the growth of fluxes from other sources with an increasing solar activity level. Based on the example of a series of flares of October 13-14, 2010, it was supposed that transient SW fluxes from the weak flares at low solar activity can manifest themselves in the form of interplanetary ICME-transients.

Wave Response during Hydrostatic and Geostrophic Adjustment. Part I: Transient Dynamics.

NASA Astrophysics Data System (ADS)

Chagnon, Jeffrey M.; Bannon, Peter R.

2005-05-01

The adjustment of a compressible, stably stratified atmosphere to sources of hydrostatic and geostrophic imbalance is investigated using a linear model. Imbalance is produced by prescribed, time-dependent injections of mass, heat, or momentum that model those processes considered “external” to the scales of motion on which the linearization and other model assumptions are justifiable. Solutions are demonstrated in response to a localized warming characteristic of small isolated clouds, larger thunderstorms, and convective systems.For a semi-infinite atmosphere, solutions consist of a set of vertical modes of continuously varying wavenumber, each of which contains time dependencies classified as steady, acoustic wave, and buoyancy wave contributions. Additionally, a rigid lower-boundary condition implies the existence of a discrete mode—the Lamb mode— containing only a steady and acoustic wave contribution. The forced solutions are generalized in terms of a temporal Green's function, which represents the response to an instantaneous injection.The response to an instantaneous warming with geometry representative of a small, isolated cloud takes place in two stages. Within the first few minutes, acoustic and Lamb waves accomplish an expansion of the heated region. Within the first quarter-hour, nonhydrostatic buoyancy waves accomplish an upward displacement inside of the heated region with inflow below, outflow above, and weak subsidence on the periphery—all mainly accomplished by the lowest vertical wavenumber modes, which have the largest horizontal group speed. More complicated transient patterns of inflow aloft and outflow along the lower boundary are accomplished by higher vertical wavenumber modes. Among these is an outwardly propagating rotor along the lower boundary that effectively displaces the low-level inflow upward and outward.A warming of 20 min duration with geometry representative of a large thunderstorm generates only a weak acoustic response in the horizontal by the Lamb waves. The amplitude of this signal increases during the onset of the heating and decreases as the heating is turned off. The lowest vertical wavenumber buoyancy waves still dominate the horizontal adjustment, and the horizontal scale of displacements is increased by an order of magnitude. Within a few hours the transient motions remove the perturbations and an approximately trivial balanced state is established.A warming of 2 h duration with geometry representative of a large convective system generates a weak but discernible Lamb wave signal. The response to the conglomerate system is mainly hydrostatic. After several hours, the only signal in the vicinity of the heated region is that of inertia-gravity waves oscillating about a nontrivial hydrostatic and geostrophic state.This paper is the first of two parts treating the transient dynamics of hydrostatic and geostrophic adjustment. Part II examines the potential vorticity conservation and the partitioning of total energy.

Internal and near nozzle measurements of Engine Combustion Network “Spray G” gasoline direct injectors

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

Duke, Daniel J.; Kastengren, Alan L.; Matusik, Katarzyna E.

Gasoline direct injection (GDI) sprays are complex multiphase flows. When compared to multi-hole diesel sprays, the plumes are closely spaced, and the sprays are more likely to interact. The effects of multi-jet interaction on entrainment and spray targeting can be influenced by small variations in the mass fluxes from the holes, which in turn depend on transients in the needle movement and small-scale details of the internal geometry. In this paper, we present a comprehensive overview of a multi-institutional effort to experimentally characterize the internal geometry and near-nozzle flow of the Engine Combustion Network (ECN) Spray G gasoline injector. Inmore » order to develop a complete picture of the near-nozzle flow, a standardized setup was shared between facilities. A wide range of techniques were employed, including both X-ray and visible-light diagnostics. The novel aspects of this work include both new experimental measurements, and a comparison of the results across different techniques and facilities. The breadth and depth of the data reveal phenomena which were not apparent from analysis of the individual data sets. We show that plume-to-plume variations in the mass fluxes from the holes can cause large-scale asymmetries in the entrainment field and spray structure. Both internal flow transients and small-scale geometric features can have an effect on the external flow. The sharp turning angle of the flow into the holes also causes an inward vectoring of the plumes relative to the hole drill angle, which increases with time due to entrainment of gas into a low-pressure region between the plumes. In conclusion, these factors increase the likelihood of spray collapse with longer injection durations.« less

Internal and near nozzle measurements of Engine Combustion Network “Spray G” gasoline direct injectors

DOE PAGES

Duke, Daniel J.; Kastengren, Alan L.; Matusik, Katarzyna E.; ...

2017-07-25

Gasoline direct injection (GDI) sprays are complex multiphase flows. When compared to multi-hole diesel sprays, the plumes are closely spaced, and the sprays are more likely to interact. The effects of multi-jet interaction on entrainment and spray targeting can be influenced by small variations in the mass fluxes from the holes, which in turn depend on transients in the needle movement and small-scale details of the internal geometry. In this paper, we present a comprehensive overview of a multi-institutional effort to experimentally characterize the internal geometry and near-nozzle flow of the Engine Combustion Network (ECN) Spray G gasoline injector. Inmore » order to develop a complete picture of the near-nozzle flow, a standardized setup was shared between facilities. A wide range of techniques were employed, including both X-ray and visible-light diagnostics. The novel aspects of this work include both new experimental measurements, and a comparison of the results across different techniques and facilities. The breadth and depth of the data reveal phenomena which were not apparent from analysis of the individual data sets. We show that plume-to-plume variations in the mass fluxes from the holes can cause large-scale asymmetries in the entrainment field and spray structure. Both internal flow transients and small-scale geometric features can have an effect on the external flow. The sharp turning angle of the flow into the holes also causes an inward vectoring of the plumes relative to the hole drill angle, which increases with time due to entrainment of gas into a low-pressure region between the plumes. In conclusion, these factors increase the likelihood of spray collapse with longer injection durations.« less

Analyses of 1/15 scale Creare bypass transient experiments. [PWR

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

Kmetyk, L.N.; Buxton, L.D.; Cole, R.K. Jr.

1982-09-01

RELAP4 analyses of several 1/15 scale Creare H-series bypass transient experiments have been done to investigate the effect of using different downcomer nodalizations, physical scales, slip models, and vapor fraction donoring methods. Most of the analyses were thermal equilibrium calculations performed with RELAP4/MOD5, but a few such calculations were done with RELAP4/MOD6 and RELAP4/MOD7, which contain improved slip models. In order to estimate the importance of nonequilibrium effects, additional analyses were performed with TRAC-PD2, RELAP5 and the nonequilibrium option of RELAP4/MOD7. The purpose of these studies was to determine whether results from Westinghouse's calculation of the Creare experiments, which weremore » done with a UHI-modified version of SATAN, were sufficient to guarantee SATAN would be conservative with respect to ECC bypass in full-scale plant analyses.« less

Scalable subsurface inverse modeling of huge data sets with an application to tracer concentration breakthrough data from magnetic resonance imaging

DOE PAGES

Lee, Jonghyun; Yoon, Hongkyu; Kitanidis, Peter K.; ...

2016-06-09

When characterizing subsurface properties is crucial for reliable and cost-effective groundwater supply management and contaminant remediation. With recent advances in sensor technology, large volumes of hydro-geophysical and geochemical data can be obtained to achieve high-resolution images of subsurface properties. However, characterization with such a large amount of information requires prohibitive computational costs associated with “big data” processing and numerous large-scale numerical simulations. To tackle such difficulties, the Principal Component Geostatistical Approach (PCGA) has been proposed as a “Jacobian-free” inversion method that requires much smaller forward simulation runs for each iteration than the number of unknown parameters and measurements needed inmore » the traditional inversion methods. PCGA can be conveniently linked to any multi-physics simulation software with independent parallel executions. In our paper, we extend PCGA to handle a large number of measurements (e.g. 106 or more) by constructing a fast preconditioner whose computational cost scales linearly with the data size. For illustration, we characterize the heterogeneous hydraulic conductivity (K) distribution in a laboratory-scale 3-D sand box using about 6 million transient tracer concentration measurements obtained using magnetic resonance imaging. Since each individual observation has little information on the K distribution, the data was compressed by the zero-th temporal moment of breakthrough curves, which is equivalent to the mean travel time under the experimental setting. Moreover, only about 2,000 forward simulations in total were required to obtain the best estimate with corresponding estimation uncertainty, and the estimated K field captured key patterns of the original packing design, showing the efficiency and effectiveness of the proposed method. This article is protected by copyright. All rights reserved.« less

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

Lee, Jonghyun; Yoon, Hongkyu; Kitanidis, Peter K.

When characterizing subsurface properties is crucial for reliable and cost-effective groundwater supply management and contaminant remediation. With recent advances in sensor technology, large volumes of hydro-geophysical and geochemical data can be obtained to achieve high-resolution images of subsurface properties. However, characterization with such a large amount of information requires prohibitive computational costs associated with “big data” processing and numerous large-scale numerical simulations. To tackle such difficulties, the Principal Component Geostatistical Approach (PCGA) has been proposed as a “Jacobian-free” inversion method that requires much smaller forward simulation runs for each iteration than the number of unknown parameters and measurements needed inmore » the traditional inversion methods. PCGA can be conveniently linked to any multi-physics simulation software with independent parallel executions. In our paper, we extend PCGA to handle a large number of measurements (e.g. 106 or more) by constructing a fast preconditioner whose computational cost scales linearly with the data size. For illustration, we characterize the heterogeneous hydraulic conductivity (K) distribution in a laboratory-scale 3-D sand box using about 6 million transient tracer concentration measurements obtained using magnetic resonance imaging. Since each individual observation has little information on the K distribution, the data was compressed by the zero-th temporal moment of breakthrough curves, which is equivalent to the mean travel time under the experimental setting. Moreover, only about 2,000 forward simulations in total were required to obtain the best estimate with corresponding estimation uncertainty, and the estimated K field captured key patterns of the original packing design, showing the efficiency and effectiveness of the proposed method. This article is protected by copyright. All rights reserved.« less

Sprites, elf transients, and positive ground strokes

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

Boccippio, D.J.; Boldi, R.; Williams, E.R.

1995-08-25

In two summertime mesoscale convective systems (MCSs), mesospheric optical sprite phenomena were often coincident with both large-amplitude positive cloud-to-ground lightning and transient Schumann resonance excitations of the entire Earth-ionosphere cavity. These observations, together with earlier studies of MCS electrification, suggest that sprites are triggered when the rapid removal of large quantities of positive charge from an areally extensive charge layer stresses the mesosphere to dielectric breakdown. 46 refs., 7 figs., 1 tab.

A transient search using combined human and machine classifications

NASA Astrophysics Data System (ADS)

Wright, Darryl E.; Lintott, Chris J.; Smartt, Stephen J.; Smith, Ken W.; Fortson, Lucy; Trouille, Laura; Allen, Campbell R.; Beck, Melanie; Bouslog, Mark C.; Boyer, Amy; Chambers, K. C.; Flewelling, Heather; Granger, Will; Magnier, Eugene A.; McMaster, Adam; Miller, Grant R. M.; O'Donnell, James E.; Simmons, Brooke; Spiers, Helen; Tonry, John L.; Veldthuis, Marten; Wainscoat, Richard J.; Waters, Chris; Willman, Mark; Wolfenbarger, Zach; Young, Dave R.

2017-12-01

Large modern surveys require efficient review of data in order to find transient sources such as supernovae, and to distinguish such sources from artefacts and noise. Much effort has been put into the development of automatic algorithms, but surveys still rely on human review of targets. This paper presents an integrated system for the identification of supernovae in data from Pan-STARRS1, combining classifications from volunteers participating in a citizen science project with those from a convolutional neural network. The unique aspect of this work is the deployment, in combination, of both human and machine classifications for near real-time discovery in an astronomical project. We show that the combination of the two methods outperforms either one used individually. This result has important implications for the future development of transient searches, especially in the era of Large Synoptic Survey Telescope and other large-throughput surveys.

Anxiety After Stroke

PubMed Central

Whiteley, William N.; Dennis, Martin S.; Mead, Gillian E.; Carson, Alan J.

2018-01-01

Background and Purpose— Anxiety after stroke is common and disabling. Stroke trialists have treated anxiety as a homogenous condition, and intervention studies have followed suit, neglecting the different treatment approaches for phobic and generalized anxiety. Using diagnostic psychiatric interviews, we aimed to report the frequency of phobic and generalized anxiety, phobic avoidance, predictors of anxiety, and patient outcomes at 3 months poststroke/transient ischemic attack. Methods— We followed prospectively a cohort of new diagnosis of stroke/transient ischemic attack at 3 months with a telephone semistructured psychiatric interview, Fear Questionnaire, modified Rankin Scale, EuroQol-5D5L, and Work and Social Adjustment Scale. Results— Anxiety disorder was common (any anxiety disorder, 38 of 175 [22%]). Phobic disorder was the predominant anxiety subtype: phobic disorder only, 18 of 175 (10%); phobic and generalized anxiety disorder, 13 of 175 (7%); and generalized anxiety disorder only, 7 of 175 (4%). Participants with anxiety disorder reported higher level of phobic avoidance across all situations on the Fear Questionnaire. Younger age (per decade increase in odds ratio, 0.64; 95% confidence interval, 0.45–0.91) and having previous anxiety/depression (odds ratio, 4.38; 95% confidence interval, 1.94–9.89) were predictors for anxiety poststroke/transient ischemic attack. Participants with anxiety disorder were more dependent (modified Rankin Scale score 3–5, [anxiety] 55% versus [no anxiety] 29%; P<0.0005), had poorer quality of life on EQ-5D5L, and restricted participation (Work and Social Adjustment Scale: median, interquartile range, [anxiety] 19.5, 10–27 versus [no anxiety] 0, 0–5; P<0.001). Conclusions— Anxiety after stroke/transient ischemic attack is predominantly phobic and is associated with poorer patient outcomes. Trials of anxiety intervention in stroke should consider the different treatment approaches needed for phobic and generalized anxiety. PMID:29437982

Anxiety After Stroke: The Importance of Subtyping.

PubMed

Chun, Ho-Yan Yvonne; Whiteley, William N; Dennis, Martin S; Mead, Gillian E; Carson, Alan J

2018-03-01

Anxiety after stroke is common and disabling. Stroke trialists have treated anxiety as a homogenous condition, and intervention studies have followed suit, neglecting the different treatment approaches for phobic and generalized anxiety. Using diagnostic psychiatric interviews, we aimed to report the frequency of phobic and generalized anxiety, phobic avoidance, predictors of anxiety, and patient outcomes at 3 months poststroke/transient ischemic attack. We followed prospectively a cohort of new diagnosis of stroke/transient ischemic attack at 3 months with a telephone semistructured psychiatric interview, Fear Questionnaire, modified Rankin Scale, EuroQol-5D5L, and Work and Social Adjustment Scale. Anxiety disorder was common (any anxiety disorder, 38 of 175 [22%]). Phobic disorder was the predominant anxiety subtype: phobic disorder only, 18 of 175 (10%); phobic and generalized anxiety disorder, 13 of 175 (7%); and generalized anxiety disorder only, 7 of 175 (4%). Participants with anxiety disorder reported higher level of phobic avoidance across all situations on the Fear Questionnaire. Younger age (per decade increase in odds ratio, 0.64; 95% confidence interval, 0.45-0.91) and having previous anxiety/depression (odds ratio, 4.38; 95% confidence interval, 1.94-9.89) were predictors for anxiety poststroke/transient ischemic attack. Participants with anxiety disorder were more dependent (modified Rankin Scale score 3-5, [anxiety] 55% versus [no anxiety] 29%; P <0.0005), had poorer quality of life on EQ-5D5L, and restricted participation (Work and Social Adjustment Scale: median, interquartile range, [anxiety] 19.5, 10-27 versus [no anxiety] 0, 0-5; P <0.001). Anxiety after stroke/transient ischemic attack is predominantly phobic and is associated with poorer patient outcomes. Trials of anxiety intervention in stroke should consider the different treatment approaches needed for phobic and generalized anxiety. © 2018 The Authors.

Floquet–Magnus theory and generic transient dynamics in periodically driven many-body quantum systems

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

Kuwahara, Tomotaka, E-mail: tomotaka.phys@gmail.com; WPI, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577; Mori, Takashi

2016-04-15

This work explores a fundamental dynamical structure for a wide range of many-body quantum systems under periodic driving. Generically, in the thermodynamic limit, such systems are known to heat up to infinite temperature states in the long-time limit irrespective of dynamical details, which kills all the specific properties of the system. In the present study, instead of considering infinitely long-time scale, we aim to provide a general framework to understand the long but finite time behavior, namely the transient dynamics. In our analysis, we focus on the Floquet–Magnus (FM) expansion that gives a formal expression of the effective Hamiltonian onmore » the system. Although in general the full series expansion is not convergent in the thermodynamics limit, we give a clear relationship between the FM expansion and the transient dynamics. More precisely, we rigorously show that a truncated version of the FM expansion accurately describes the exact dynamics for a certain time-scale. Our theory reveals an experimental time-scale for which non-trivial dynamical phenomena can be reliably observed. We discuss several dynamical phenomena, such as the effect of small integrability breaking, efficient numerical simulation of periodically driven systems, dynamical localization and thermalization. Especially on thermalization, we discuss a generic scenario on the prethermalization phenomenon in periodically driven systems. -- Highlights: •A general framework to describe transient dynamics for periodically driven systems. •The theory is applicable to generic quantum many-body systems including long-range interacting systems. •Physical meaning of the truncation of the Floquet–Magnus expansion is rigorously established. •New mechanism of the prethermalization is proposed. •Revealing an experimental time-scale for which non-trivial dynamical phenomena can be reliably observed.« less

Assessment of Groundwater Susceptibility to Non-Point Source Contaminants Using Three-Dimensional Transient Indexes.

PubMed

Zhang, Yong; Weissmann, Gary S; Fogg, Graham E; Lu, Bingqing; Sun, HongGuang; Zheng, Chunmiao

2018-06-05

Groundwater susceptibility to non-point source contamination is typically quantified by stable indexes, while groundwater quality evolution (or deterioration globally) can be a long-term process that may last for decades and exhibit strong temporal variations. This study proposes a three-dimensional (3- d ), transient index map built upon physical models to characterize the complete temporal evolution of deep aquifer susceptibility. For illustration purposes, the previous travel time probability density (BTTPD) approach is extended to assess the 3- d deep groundwater susceptibility to non-point source contamination within a sequence stratigraphic framework observed in the Kings River fluvial fan (KRFF) aquifer. The BTTPD, which represents complete age distributions underlying a single groundwater sample in a regional-scale aquifer, is used as a quantitative, transient measure of aquifer susceptibility. The resultant 3- d imaging of susceptibility using the simulated BTTPDs in KRFF reveals the strong influence of regional-scale heterogeneity on susceptibility. The regional-scale incised-valley fill deposits increase the susceptibility of aquifers by enhancing rapid downward solute movement and displaying relatively narrow and young age distributions. In contrast, the regional-scale sequence-boundary paleosols within the open-fan deposits "protect" deep aquifers by slowing downward solute movement and displaying a relatively broad and old age distribution. Further comparison of the simulated susceptibility index maps to known contaminant distributions shows that these maps are generally consistent with the high concentration and quick evolution of 1,2-dibromo-3-chloropropane (DBCP) in groundwater around the incised-valley fill since the 1970s'. This application demonstrates that the BTTPDs can be used as quantitative and transient measures of deep aquifer susceptibility to non-point source contamination.

Probabilistic structural mechanics research for parallel processing computers

NASA Technical Reports Server (NTRS)

Sues, Robert H.; Chen, Heh-Chyun; Twisdale, Lawrence A.; Martin, William R.

1991-01-01

Aerospace structures and spacecraft are a complex assemblage of structural components that are subjected to a variety of complex, cyclic, and transient loading conditions. Significant modeling uncertainties are present in these structures, in addition to the inherent randomness of material properties and loads. To properly account for these uncertainties in evaluating and assessing the reliability of these components and structures, probabilistic structural mechanics (PSM) procedures must be used. Much research has focused on basic theory development and the development of approximate analytic solution methods in random vibrations and structural reliability. Practical application of PSM methods was hampered by their computationally intense nature. Solution of PSM problems requires repeated analyses of structures that are often large, and exhibit nonlinear and/or dynamic response behavior. These methods are all inherently parallel and ideally suited to implementation on parallel processing computers. New hardware architectures and innovative control software and solution methodologies are needed to make solution of large scale PSM problems practical.

Coronal X-ray enhancements associated with H-alpha filament disappearances

NASA Technical Reports Server (NTRS)

Webb, D. F.; Krieger, A. S.; Rust, D. M.

1976-01-01

The X-ray telescope experiment aboard the Skylab/ATM mission provided high-resolution soft X-ray images of the lower corona away from active regions, revealing frequent large-scale transient X-ray enhancements which could often be associated with the disappearance of H-alpha filaments. The X-ray emitting structures featured peak brightnesses similar to those of nonflaring active region structures, durations from 3 to 40 hours, shapes that in general outlined the preexisting H-alpha filaments to as large as 400,000 km, apparent expansion velocities of the order of tens of km/sec, and observed peak temperatures of the order of a few million degrees. One such event is described and analyzed in detail. Two explanations of the events are discussed: (1) excess cool material is present in the filament cavity, contributing to the X-ray enhancement, and (2) the enhancement is due to the compression of preexisting material by a changing magnetic field.

Analysis of unmitigated large break loss of coolant accidents using MELCOR code

NASA Astrophysics Data System (ADS)

Pescarini, M.; Mascari, F.; Mostacci, D.; De Rosa, F.; Lombardo, C.; Giannetti, F.

2017-11-01

In the framework of severe accident research activity developed by ENEA, a MELCOR nodalization of a generic Pressurized Water Reactor of 900 MWe has been developed. The aim of this paper is to present the analysis of MELCOR code calculations concerning two independent unmitigated large break loss of coolant accident transients, occurring in the cited type of reactor. In particular, the analysis and comparison between the transients initiated by an unmitigated double-ended cold leg rupture and an unmitigated double-ended hot leg rupture in the loop 1 of the primary cooling system is presented herein. This activity has been performed focusing specifically on the in-vessel phenomenology that characterizes this kind of accidents. The analysis of the thermal-hydraulic transient phenomena and the core degradation phenomena is therefore here presented. The analysis of the calculated data shows the capability of the code to reproduce the phenomena typical of these transients and permits their phenomenological study. A first sequence of main events is here presented and shows that the cold leg break transient results faster than the hot leg break transient because of the position of the break. Further analyses are in progress to quantitatively assess the results of the code nodalization for accident management strategy definition and fission product source term evaluation.

In situ grazing incidence small-angle X-ray scattering investigation of polystyrene nanoparticle spray deposition onto silicon.

PubMed

Herzog, Gerd; Benecke, Gunthard; Buffet, Adeline; Heidmann, Berit; Perlich, Jan; Risch, Johannes F H; Santoro, Gonzalo; Schwartzkopf, Matthias; Yu, Shun; Wurth, Wilfried; Roth, Stephan V

2013-09-10

We investigated the spray deposition and subsequent self-assembly during drying of a polystyrene nanoparticle dispersion with in situ grazing incidence small-angle X-ray scattering at high time resolution. During the fast deposition of the dispersion and the subsequent evaporation of the solvent, different transient stages of nanoparticle assembly can be identified. In the first stage, the solvent starts to evaporate without ordering of the nanoparticles. During the second stage, large-scale structures imposed by the breakup of the liquid film are observable. In this stage, the solvent evaporates further and nanoparticle ordering starts. In the late third drying stage, the nanoparticles self-assemble into the final layer structure.

Plant-made vaccine antigens and biopharmaceuticals

PubMed Central

Daniell, Henry; Singh, Nameirakpam D.; Mason, Hugh; Streatfield, Stephen J.

2009-01-01

Plant cells are ideal bioreactors for the production and oral delivery of vaccines and biopharmaceuticals, eliminating the need for expensive fermentation, purification, cold storage, transportation and sterile delivery. Plant-made vaccines have been developed for two decades but none has advanced beyond Phase I. However, two plant-made biopharmaceuticals are now advancing through Phase II and Phase III human clinical trials. In this review, we evaluate the advantages and disadvantages of different plant expression systems (stable nuclear and chloroplast or transient viral) and their current limitations or challenges. We provide suggestions for advancing this valuable concept for clinical applications and conclude that greater research emphasis is needed on large scale production, purification, functional characterization, oral delivery and preclinical evaluation. PMID:19836291

Optimization of a Monte Carlo Model of the Transient Reactor Test Facility

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

Smith, Kristin; DeHart, Mark; Goluoglu, Sedat

2017-03-01

The ultimate goal of modeling and simulation is to obtain reasonable answers to problems that don’t have representations which can be easily evaluated while minimizing the amount of computational resources. With the advances during the last twenty years of large scale computing centers, researchers have had the ability to create a multitude of tools to minimize the number of approximations necessary when modeling a system. The tremendous power of these centers requires the user to possess an immense amount of knowledge to optimize the models for accuracy and efficiency.This paper seeks to evaluate the KENO model of TREAT to optimizemore » calculational efforts.« less

Transient Go: A Mobile App for Transient Astronomy Outreach

NASA Astrophysics Data System (ADS)

Crichton, D.; Mahabal, A.; Djorgovski, S. G.; Drake, A.; Early, J.; Ivezic, Z.; Jacoby, S.; Kanbur, S.

2016-12-01

Augmented Reality (AR) is set to revolutionize human interaction with the real world as demonstrated by the phenomenal success of `Pokemon Go'. That very technology can be used to rekindle the interest in science at the school level. We are in the process of developing a prototype app based on sky maps that will use AR to introduce different classes of astronomical transients to students as they are discovered i.e. in real-time. This will involve transient streams from surveys such as the Catalina Real-time Transient Survey (CRTS) today and the Large Synoptic Survey Telescope (LSST) in the near future. The transient streams will be combined with archival and latest image cut-outs and other auxiliary data as well as historical and statistical perspectives on each of the transient types being served. Such an app could easily be adapted to work with various NASA missions and NSF projects to enrich the student experience.

M.I.T. studies of transient X-ray phenomena. [astronomical observations

NASA Technical Reports Server (NTRS)

Canizares, C. R.

1976-01-01

A variety of transient X-ray phenomena have been studied. Data from the OSO-7 satellite reveal both long and short time-scale transients. Extensive observations have been made of the Lupus X-ray Nova (3U1543-47) and GX339-4(MX 1658-48) which may represent a very different type of transient source. A unique, intense X-ray flare lasting ten minutes was also recorded, and the X-ray emission from the active galaxy Cen A was found to vary significantly over a period of several days. In a recent balloon flight the Crab pulsar, NP0532, was observed to exhibit a transient pulsed component distinct from the usual main pulse and interpulse. A sounding-rocket experiment detected an ultrasoft transient X-ray source tentatively associated with SS Cygni, and preliminary results from SAS-3 show a very hard spectrum for the new source A0535 + 26. On the other hand, extensive OSO-7 null observations of both Type I and II supernovae and of the flaring radio star Algol make it unlikely that these types of objects are potent transient X-ray emitters.

The first PANDA tests

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

Dreier, J.; Huggenberger, M.; Aubert, C.

1996-08-01

The PANDA test facility at PSI in Switzerland is used to study the long-term Simplified Boiling Water Reactor (SBWR) Passive Containment Cooling System (PCCS) performance. The PANDA tests demonstrate performance on a larger scale than previous tests and examine the effects of any non-uniform spatial distributions of steam and non-condensables in the system. The PANDA facility has a 1:1 vertical scale, and 1:25 ``system`` scale (volume, power, etc.). Steady-state PCCS condenser performance tests and extensive facility characterization tests have been completed. Transient system behavior tests were conducted late in 1995; results from the first three transient tests (M3 series) aremore » reviewed. The first PANDA tests showed that the overall global behavior of the SBWR containment was globally repeatable and very favorable; the system exhibited great ``robustness.``« less

Structure and sources of solar wind in the growing phase of 24th solar cycle

NASA Astrophysics Data System (ADS)

Slemzin, Vladimir; Goryaev, Farid; Shugay, Julia; Rodkin, Denis; Veselovsky, Igor

2015-04-01

We present analysis of the solar wind (SW) structure and its association with coronal sources during the minimum and rising phase of 24th solar cycle (2009-2011). The coronal sources prominent in this period - coronal holes, small areas of open magnetic fields near active regions and transient sources associated with small-scale solar activity have been investigated using EUV solar images and soft X-ray fluxes obtained by the CORONAS-Photon/TESIS/Sphinx, PROBA2/SWAP, Hinode/EIS and AIA/SDO instruments as well as the magnetograms obtained by HMI/SDO. It was found that at solar minimum (2009) velocity and magnetic field strength of high speed wind (HSW) and transient SW from small-scale flares did not differ significantly from those of the background slow speed wind (SSW). The major difference between parameters of different SW components was seen in the ion composition represented by the C6/C5, O7/O6, Fe/O ratios and the mean charge of Fe ions. With growing solar activity, the speed of HSW increased due to transformation of its sources - small-size low-latitude coronal holes into equatorial extensions of large polar holes. At that period, the ion composition of transient SW changed from low-temperature to high-temperature values, which was caused by variation of the source conditions and change of the recombination/ionization rates during passage of the plasma flow through the low corona. However, we conclude that criteria of separation of the SW components based on the ion ratios established earlier by Zhao&Fisk (2009) for higher solar activity are not applicable to the extremely weak beginning of 24th cycle. The research leading to these results has received funding from the European Commission's Seventh Framework Programme (FP7/2007-2013) under the grant agreement eHeroes (project n° 284461, www.eheroes.eu).

Dynamics and Size of Cross-Linking-Induced Lipid Nanodomains in Model Membranes

PubMed Central

Štefl, Martin; Šachl, Radek; Humpolíčková, Jana; Cebecauer, Marek; Macháň, Radek; Kolářová, Marie; Johansson, Lennart B.-Å.; Hof, Martin

2012-01-01

Changes of membrane organization upon cross-linking of its components trigger cell signaling response to various exogenous factors. Cross-linking of raft gangliosides GM1 with cholera toxin (CTxB) was shown to cause microscopic phase separation in model membranes, and the CTxB-GM1 complexes forming a minimal lipid raft unit are the subject of ongoing cell membrane research. Yet, those subdiffraction sized rafts have never been described in terms of size and dynamics. By means of two-color z-scan fluorescence correlation spectroscopy, we show that the nanosized domains are formed in model membranes at lower sphingomyelin (Sph) content than needed for the large-scale phase separation and that the CTxB-GM1 complexes are confined in the domains poorly stabilized with Sph. Förster resonance energy transfer together with Monte Carlo modeling of the donor decay response reveal the domain radius of ∼8 nm, which increases at higher Sph content. We observed two types of domains behaving differently, which suggests a dual role of the cross-linker: first, local transient condensation of the GM1 molecules compensating for a lack of Sph and second, coalescence of existing nanodomains ending in large-scale phase separation. PMID:22824274

Dynamic security contingency screening and ranking using neural networks.

PubMed

Mansour, Y; Vaahedi, E; El-Sharkawi, M A

1997-01-01

This paper summarizes BC Hydro's experience in applying neural networks to dynamic security contingency screening and ranking. The idea is to use the information on the prevailing operating condition and directly provide contingency screening and ranking using a trained neural network. To train the two neural networks for the large scale systems of BC Hydro and Hydro Quebec, in total 1691 detailed transient stability simulation were conducted, 1158 for BC Hydro system and 533 for the Hydro Quebec system. The simulation program was equipped with the energy margin calculation module (second kick) to measure the energy margin in each run. The first set of results showed poor performance for the neural networks in assessing the dynamic security. However a number of corrective measures improved the results significantly. These corrective measures included: 1) the effectiveness of output; 2) the number of outputs; 3) the type of features (static versus dynamic); 4) the number of features; 5) system partitioning; and 6) the ratio of training samples to features. The final results obtained using the large scale systems of BC Hydro and Hydro Quebec demonstrates a good potential for neural network in dynamic security assessment contingency screening and ranking.

Transcontinental Surface Validation of Satellite Observations of Enhanced Methane Anomalies Associated with Fossil Fuel Industrial Methane Emissions

NASA Astrophysics Data System (ADS)

Leifer, I.; Culling, D.; Schneising, O.; Bovensmann, H.; Buchwitz, M.; Burrows, J. P.

2012-12-01

A ground-based, transcontinental (Florida to California - i.e., satellite-scale) survey was conducted to understand better the role of fossil fuel industrial (FFI) fugitive emissions of the potent greenhouse gas, methane. Data were collected by flame ion detection gas chromatography (Fall 2010) and by a cavity ring-down sensor (Winter 2012) from a nearly continuously moving recreational vehicle, allowing 24/7 data collection. Nocturnal methane measurements for similar sources tended to be higher compared to daytime values, sometime significantly, due to day/night meteorological differences. Data revealed strong and persistent FFI methane sources associated with refining, a presumed major pipeline leak, and several minor pipeline leaks, a coal loading plant, and areas of active petroleum production. Data showed FFI source emissions were highly transient and heterogeneous; however, integrated over these large-scale facilities, methane signatures overwhelmed that of other sources, creating clearly identifiable plumes that were well elevated above ambient. The highest methane concentration recorded was 39 ppm at an active central valley California production field, while desert values were as low as 1.80 ppm. Surface methane data show similar trends with strong emissions correlated with FFI on large (4° bin) scales and positive methane anomalies centered on the Gulf Coast area of Houston, home to most of US refining capacity. Comparison with SCIAMACHY and GOSAT satellite data show agreement with surface data in the large-scale methane spatial patterns. Positive satellite methane anomalies in the southeast and Mexico largely correlated with methane anthropogenic and wetland inventory models suggests most strong ground methane anomalies in the Gulf of Mexico region were related to dominant FFI input for most seasons. Wind advection played a role, in some cases confounding a clear relationship. Results are consistent with a non-negligible underestimation of the FFI contribution to global methane budgets.; In situ methane concentrations during transcontinental survey Fall 2010.

Impacts of a lengthening open water season on Alaskan coastal communities: deriving locally relevant indices from large-scale datasets and community observations

NASA Astrophysics Data System (ADS)

Rolph, Rebecca J.; Mahoney, Andrew R.; Walsh, John; Loring, Philip A.

2018-05-01

Using thresholds of physical climate variables developed from community observations, together with two large-scale datasets, we have produced local indices directly relevant to the impacts of a reduced sea ice cover on Alaska coastal communities. The indices include the number of false freeze-ups defined by transient exceedances of ice concentration prior to a corresponding exceedance that persists, false break-ups, timing of freeze-up and break-up, length of the open water duration, number of days when the winds preclude hunting via boat (wind speed threshold exceedances), the number of wind events conducive to geomorphological work or damage to infrastructure from ocean waves, and the number of these wind events with on- and along-shore components promoting water setup along the coastline. We demonstrate how community observations can inform use of large-scale datasets to derive these locally relevant indices. The two primary large-scale datasets are the Historical Sea Ice Atlas for Alaska and the atmospheric output from a regional climate model used to downscale the ERA-Interim atmospheric reanalysis. We illustrate the variability and trends of these indices by application to the rural Alaska communities of Kotzebue, Shishmaref, and Utqiaġvik (previously Barrow), although the same procedure and metrics can be applied to other coastal communities. Over the 1979-2014 time period, there has been a marked increase in the number of combined false freeze-ups and false break-ups as well as the number of days too windy for hunting via boat for all three communities, especially Utqiaġvik. At Utqiaġvik, there has been an approximate tripling of the number of wind events conducive to coastline erosion from 1979 to 2014. We have also found a delay in freeze-up and earlier break-up, leading to a lengthened open water period for all of the communities examined.

Transient chaos - a resolution of breakdown of quantum-classical correspondence in optomechanics.

PubMed

Wang, Guanglei; Lai, Ying-Cheng; Grebogi, Celso

2016-10-17

Recently, the phenomenon of quantum-classical correspondence breakdown was uncovered in optomechanics, where in the classical regime the system exhibits chaos but in the corresponding quantum regime the motion is regular - there appears to be no signature of classical chaos whatsoever in the corresponding quantum system, generating a paradox. We find that transient chaos, besides being a physically meaningful phenomenon by itself, provides a resolution. Using the method of quantum state diffusion to simulate the system dynamics subject to continuous homodyne detection, we uncover transient chaos associated with quantum trajectories. The transient behavior is consistent with chaos in the classical limit, while the long term evolution of the quantum system is regular. Transient chaos thus serves as a bridge for the quantum-classical transition (QCT). Strikingly, as the system transitions from the quantum to the classical regime, the average chaotic transient lifetime increases dramatically (faster than the Ehrenfest time characterizing the QCT for isolated quantum systems). We develop a physical theory to explain the scaling law.

Transient chaos - a resolution of breakdown of quantum-classical correspondence in optomechanics

PubMed Central

Wang, Guanglei; Lai, Ying-Cheng; Grebogi, Celso

2016-01-01

Recently, the phenomenon of quantum-classical correspondence breakdown was uncovered in optomechanics, where in the classical regime the system exhibits chaos but in the corresponding quantum regime the motion is regular - there appears to be no signature of classical chaos whatsoever in the corresponding quantum system, generating a paradox. We find that transient chaos, besides being a physically meaningful phenomenon by itself, provides a resolution. Using the method of quantum state diffusion to simulate the system dynamics subject to continuous homodyne detection, we uncover transient chaos associated with quantum trajectories. The transient behavior is consistent with chaos in the classical limit, while the long term evolution of the quantum system is regular. Transient chaos thus serves as a bridge for the quantum-classical transition (QCT). Strikingly, as the system transitions from the quantum to the classical regime, the average chaotic transient lifetime increases dramatically (faster than the Ehrenfest time characterizing the QCT for isolated quantum systems). We develop a physical theory to explain the scaling law. PMID:27748418

Scaling of transient storage parameter estimates with increasing reach length in a mountain headwater stream

Treesearch

M. Briggs; M. N. Gooseff; B. McGlynn

2006-01-01

We performed two conservative tracer injections in a mountain stream in order to access the relationship between storage parameters on the short subreach scale to the longer reach which they comprise.

Evidence of Hierarchy in the Complex Fractured System of Geropotamos (Crete, Greece), as Extracted from Transient Electromagnetic Responses

NASA Astrophysics Data System (ADS)

Vallianatos, Filippos; Kouli, Maria; Kalisperi, Despina

2018-03-01

The essential goals of this paper are to test the transient electromagnetic (TEM) response in a fractured geological complex medium and to better understand the physics introduced by associating a roughness parameter β to the geological formation. An anomalous fractional diffusion approach is incorporated to describe the electromagnetic induction in rough multi-scaled geological structures. The multi-scaling characteristics of Geropotamos basin in Crete are revealed through the analysis of transient step-off response of an EM loop antenna. The semi-empirical parameters derived from late-time TEM measurements are correlated with the multi-scale heterogeneities of the medium. Certain interesting properties of the late-time slope γ(β) and the power law of near surface resistivity distribution, as extracted from TEM inversion for different depth, are presented. The analysis of the parameter γ(β) which scales the induced voltage in the loop in the late stage of the electromagnetic response leads to a different view of the EM geophysical data interpretation. We show that it is strongly correlated with areas of high fracture density within the geological formations of the Geropotamos area. For that reason, it is proposed as a local multi-scaling empirical index. The results of this paper suggest that anomalous diffusion could be a viable physical mechanism for the fractal transport of charge carriers, explaining observed late-time TEM responses across a variety of natural geological settings.

The Volumetric Rate of Calcium-rich Transients in the Local Universe

NASA Astrophysics Data System (ADS)

Frohmaier, Chris; Sullivan, Mark; Maguire, Kate; Nugent, Peter

2018-05-01

We present a measurement of the volumetric rate of “calcium-rich” optical transients in the local universe, using a sample of three events from the Palomar Transient Factory (PTF). This measurement builds on a detailed study of the PTF transient detection efficiencies and uses a Monte Carlo simulation of the PTF survey. We measure the volumetric rate of calcium-rich transients to be higher than previous estimates: {1.21}-0.39+1.13 × {10}-5 events yr‑1 Mpc‑3. This is equivalent to 33%–94% of the local volumetric Type Ia supernova rate. This calcium-rich transient rate is sufficient to reproduce the observed calcium abundances in galaxy clusters, assuming an asymptotic calcium yield per calcium-rich event of ∼0.05 {M}ȯ . We also study the PTF detection efficiency of these transients as a function of position within their candidate host galaxies. We confirm as a real physical effect previous results that suggest that calcium-rich transients prefer large physical offsets from their host galaxies.

Follow-up observations of SN 2010dn

NASA Astrophysics Data System (ADS)

Botticella, Maria Teresa; Kotak, Rubina; Meikle, Peter; Smartt, Stephen; Pastorello, Andrea; Benetti, Stefano

2010-06-01

A new intriguing transient, SN 2010dn in NGC 3184, was discovered ten days ago. The spectroscopic and photometric evolution make this transient similar to SN 2008S, the 2006 optical transient in M85 and the 2008 optical transient in NGC 300, members of a new class of transient events given the similar pre-explosion?and post-explosion properties. The nature of these transient is still debated?and our experience with SN 2008S proved that?Spitzer data are?invaluable to shed light on it providing a critical information in the understanding?the geometry of the circumstellar environment of these transients both for the dust enshrouded progenitor stars and after?their explosion. We would like to obtain a rapid follow-up of SN 2010dn with Spitzer to check if also this transient is producing an IR echo from substantial circumstellar material around the progenitor star. The modeling of the light echo will allow us to constrain the mass and?physical scale?of the circumstellar dust around this transient and as consequence to probe the mass loss history of the progenitor star. The proposed observations will be coordinated with an extensive optical follow up and?will be of interest to the broad scientific community. To obtain prompt observations after the discovery?is crucial.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed Central

Ma, Xiaohui; Chang, Ping; Saravanan, R.; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-01-01

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy–atmosphere interaction in forecast and climate models. PMID:26635077

Flow and residence times of dynamic river bank storage and sinuosity-driven hyporheic exchange

USGS Publications Warehouse

Gomez-Velez, J.D.; Wilson, J.L.; Cardenas, M.B.; Harvey, Judson

2017-01-01

Hydrologic exchange fluxes (HEFs) vary significantly along river corridors due to spatiotemporal changes in discharge and geomorphology. This variability results in the emergence of biogeochemical hot-spots and hot-moments that ultimately control solute and energy transport and ecosystem services from the local to the watershed scales. In this work, we use a reduced-order model to gain mechanistic understanding of river bank storage and sinuosity-driven hyporheic exchange induced by transient river discharge. This is the first time that a systematic analysis of both processes is presented and serves as an initial step to propose parsimonious, physics-based models for better predictions of water quality at the large watershed scale. The effects of channel sinuosity, alluvial valley slope, hydraulic conductivity, and river stage forcing intensity and duration are encapsulated in dimensionless variables that can be easily estimated or constrained. We find that the importance of perturbations in the hyporheic zone's flux, residence times, and geometry is mainly explained by two-dimensionless variables representing the ratio of the hydraulic time constant of the aquifer and the duration of the event (Γd) and the importance of the ambient groundwater flow ( ). Our model additionally shows that even systems with small sensitivity, resulting in small changes in the hyporheic zone extent, are characterized by highly variable exchange fluxes and residence times. These findings highlight the importance of including dynamic changes in hyporheic zones for typical HEF models such as the transient storage model.

DYNAMICS OF ON-DISK PLUMES AS OBSERVED WITH THE INTERFACE REGION IMAGING SPECTROGRAPH, THE ATMOSPHERIC IMAGING ASSEMBLY, AND THE HELIOSEISMIC AND MAGNETIC IMAGER

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

Pant, Vaibhav; Mazumder, Rakesh; Banerjee, Dipankar

2015-07-01

We examine the role of small-scale transients in the formation and evolution of solar coronal plumes. We study the dynamics of plume footpoints seen in the vicinity of a coronal hole using the Atmospheric Imaging Assembly (AIA) images, the Helioseismic and Magnetic Imager magnetogram on board the Solar Dynamics Observatory and spectroscopic data from the Interface Region Imaging Spectrograph (IRIS). Quasi-periodic brightenings are observed in the base of the plumes and are associated with magnetic flux changes. With the high spectral and spatial resolution of IRIS, we identify the sources of these oscillations and try to understand what role themore » transients at the footpoints can play in sustaining the coronal plumes. IRIS “sit-and-stare” observations provide a unique opportunity to study the evolution of footpoints of the plumes. We notice enhanced line width and intensity, and large deviation from the average Doppler shift in the line profiles at specific instances, which indicate the presence of flows at the footpoints of plumes. We propose that outflows (jet-like features) as a result of small-scale reconnections affect the line profiles. These jet-like features may also be responsible for the generation of propagating disturbances (PDs) within the plumes, which are observed to be propagating to larger distances as recorded from multiple AIA channels. These PDs can be explained in terms of slow magnetoacoustic waves.« less

Large-Scale Conformational Changes of Trypanosoma cruzi Proline Racemase Predicted by Accelerated Molecular Dynamics Simulation

PubMed Central

McCammon, J. Andrew

2011-01-01

Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), is a life-threatening illness affecting 11–18 million people. Currently available treatments are limited, with unacceptable efficacy and safety profiles. Recent studies have revealed an essential T. cruzi proline racemase enzyme (TcPR) as an attractive candidate for improved chemotherapeutic intervention. Conformational changes associated with substrate binding to TcPR are believed to expose critical residues that elicit a host mitogenic B-cell response, a process contributing to parasite persistence and immune system evasion. Characterization of the conformational states of TcPR requires access to long-time-scale motions that are currently inaccessible by standard molecular dynamics simulations. Here we describe advanced accelerated molecular dynamics that extend the effective simulation time and capture large-scale motions of functional relevance. Conservation and fragment mapping analyses identified potential conformational epitopes located in the vicinity of newly identified transient binding pockets. The newly identified open TcPR conformations revealed by this study along with knowledge of the closed to open interconversion mechanism advances our understanding of TcPR function. The results and the strategy adopted in this work constitute an important step toward the rationalization of the molecular basis behind the mitogenic B-cell response of TcPR and provide new insights for future structure-based drug discovery. PMID:22022240

Large-scale conformational changes of Trypanosoma cruzi proline racemase predicted by accelerated molecular dynamics simulation.

PubMed

de Oliveira, César Augusto F; Grant, Barry J; Zhou, Michelle; McCammon, J Andrew

2011-10-01

Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), is a life-threatening illness affecting 11-18 million people. Currently available treatments are limited, with unacceptable efficacy and safety profiles. Recent studies have revealed an essential T. cruzi proline racemase enzyme (TcPR) as an attractive candidate for improved chemotherapeutic intervention. Conformational changes associated with substrate binding to TcPR are believed to expose critical residues that elicit a host mitogenic B-cell response, a process contributing to parasite persistence and immune system evasion. Characterization of the conformational states of TcPR requires access to long-time-scale motions that are currently inaccessible by standard molecular dynamics simulations. Here we describe advanced accelerated molecular dynamics that extend the effective simulation time and capture large-scale motions of functional relevance. Conservation and fragment mapping analyses identified potential conformational epitopes located in the vicinity of newly identified transient binding pockets. The newly identified open TcPR conformations revealed by this study along with knowledge of the closed to open interconversion mechanism advances our understanding of TcPR function. The results and the strategy adopted in this work constitute an important step toward the rationalization of the molecular basis behind the mitogenic B-cell response of TcPR and provide new insights for future structure-based drug discovery.

realfast: Real-time, Commensal Fast Transient Surveys with the Very Large Array

NASA Astrophysics Data System (ADS)

Law, C. J.; Bower, G. C.; Burke-Spolaor, S.; Butler, B. J.; Demorest, P.; Halle, A.; Khudikyan, S.; Lazio, T. J. W.; Pokorny, M.; Robnett, J.; Rupen, M. P.

2018-05-01

Radio interferometers have the ability to precisely localize and better characterize the properties of sources. This ability is having a powerful impact on the study of fast radio transients, where a few milliseconds of data is enough to pinpoint a source at cosmological distances. However, recording interferometric data at millisecond cadence produces a terabyte-per-hour data stream that strains networks, computing systems, and archives. This challenge mirrors that of other domains of science, where the science scope is limited by the computational architecture as much as the physical processes at play. Here, we present a solution to this problem in the context of radio transients: realfast, a commensal, fast transient search system at the Jansky Very Large Array. realfast uses a novel architecture to distribute fast-sampled interferometric data to a 32-node, 64-GPU cluster for real-time imaging and transient detection. By detecting transients in situ, we can trigger the recording of data for those rare, brief instants when the event occurs and reduce the recorded data volume by a factor of 1000. This makes it possible to commensally search a data stream that would otherwise be impossible to record. This system will search for millisecond transients in more than 1000 hr of data per year, potentially localizing several Fast Radio Bursts, pulsars, and other sources of impulsive radio emission. We describe the science scope for realfast, the system design, expected outcomes, and ways in which real-time analysis can help in other fields of astrophysics.

EFFECTS OF LARGE-SCALE NON-AXISYMMETRIC PERTURBATIONS IN THE MEAN-FIELD SOLAR DYNAMO

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

Pipin, V. V.; Kosovichev, A. G.

2015-11-10

We explore the response of a nonlinear non-axisymmetric mean-field solar dynamo model to shallow non-axisymmetric perturbations. After a relaxation period, the amplitude of the non-axisymmetric field depends on the initial condition, helicity conservation, and the depth of perturbation. It is found that a perturbation that is anchored at 0.9 R{sub ⊙} has a profound effect on the dynamo process, producing a transient magnetic cycle of the axisymmetric magnetic field, if it is initiated at the growing phase of the cycle. The non-symmetric, with respect to the equator, perturbation results in a hemispheric asymmetry of the magnetic activity. The evolution ofmore » the axisymmetric and non-axisymmetric fields depends on the turbulent magnetic Reynolds number R{sub m}. In the range of R{sub m} = 10{sup 4}–10{sup 6} the evolution returns to the normal course in the next cycle, in which the non-axisymmetric field is generated due to a nonlinear α-effect and magnetic buoyancy. In the stationary state, the large-scale magnetic field demonstrates a phenomenon of “active longitudes” with cyclic 180° “flip-flop” changes of the large-scale magnetic field orientation. The flip-flop effect is known from observations of solar and stellar magnetic cycles. However, this effect disappears in the model, which includes the meridional circulation pattern determined by helioseismology. The rotation rate of the non-axisymmetric field components varies during the relaxation period and carries important information about the dynamo process.« less

Imaging the Chicxulub central crater zone from large scale seismic acoustic wave propagation and gravity modeling

NASA Astrophysics Data System (ADS)

Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.

2017-12-01

Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments

Studies of Transient Meteor Activity

NASA Technical Reports Server (NTRS)

Jenniskens, Peter M. M.

2002-01-01

Meteoroids bombard Earth's atmosphere daily, but occasionally meteor rates increase to unusual high levels when Earth crosses the relatively fresh ejecta of comets. These transient events in meteor activity provide clues about the whereabouts of Earth-threatening long-period comets, the mechanisms of large-grain dust ejection from comets, and the particle composition and size distribution of the cometary ejecta. Observations of these transient events provide important insight in natural processes that determine the large grain dust environment of comets, in natural phenomena that were prevalent during the time of the origin of life, and in processes that determine the hazard of civilizations to large impacts and of man-made satellites to the periodic blizzard of small meteoroids. In this proposal, three tasks form a coherent program aimed at elucidating various aspects of meteor outbursts, with special reference to planetary astronomy and astrobiology. Task 1 was a ground-based effort to observe periods of transient meteor activity. This includes: (1) stereoscopic imaging of meteors during transient meteor events for measurements of particle size distribution, meteoroid orbital dispersions and fluxes; and (2) technical support for Global-MS-Net, a network of amateur-operated automatic counting stations for meteor reflections from commercial VHF radio and TV broadcasting stations, keeping a 24h vigil on the level of meteor activity for the detection of new meteor streams. Task 2 consisted of ground-based and satellite born spectroscopic observations of meteors and meteor trains during transient meteor events for measurements of elemental composition, the presence of organic matter in the meteoroids, and products generated by the interaction of the meteoroid with the atmosphere. Task 3 was an airborne effort to explore the 2000 Leonid meteor outbursts, which are anticipated to be the most significant of transient meteor activity events in the remainder of the agreement period. This includes technical support for a multi-instrument aircraft campaign, Leonid MAC.

Western Wind and Solar Integration Study Phase 3A: Low Levels of Synchronous Generation

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

Miller, Nicholas W.; Leonardi, Bruno; D'Aquila, Robert

The stability of the North American electric power grids under conditions of high penetrations of wind and solar is a significant concern and possible impediment to reaching renewable energy goals. The 33% wind and solar annual energy penetration considered in this study results in substantial changes to the characteristics of the bulk power system. This includes different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior from wind and solar generation. The Western Wind and Solar Integration Study (WWSIS), sponsored by the U.S. Department of Energy, is one of the largest regional solar andmore » wind integration studies to date. In multiple phases, it has explored different aspects of the question: Can we integrate large amounts of wind and solar energy into the electric power system of the West? The work reported here focused on the impact of low levels of synchronous generation on the transient stability performance in one part of the region in which wind generation has displaced synchronous thermal generation under highly stressed, weak system conditions. It is essentially an extension of WWSIS-3. Transient stability, the ability of the power system to maintain synchronism among all elements following disturbances, is a major constraint on operations in many grids, including the western U.S. and Texas systems. These constraints primarily concern the performance of the large-scale bulk power system. But grid-wide stability concerns with high penetrations of wind and solar are still not thoroughly understood. This work focuses on 'traditional' fundamental frequency stability issues, such as maintaining synchronism, frequency, and voltage. The objectives of this study are to better understand the implications of low levels of synchronous generation and a weak grid on overall system performance by: 1) Investigating the Western Interconnection under conditions of both high renewable generation (e.g., wind and solar) and low synchronous generation (e.g., significant coal power plant decommitment or retirement); and 2) Analyzing both the large-scale stability of the Western Interconnection and regional stability issues driven by more geographically dispersed renewable generation interacting with a transmission grid that evolved with large, central station plants at key nodes. As noted above, the work reported here is an extension of the research performed in WWSIS-3.« less

Ultra-Long Time Dynamics of Contaminant Plume Mixing Induced by Transient Forcing Factors in Geologic Formations

NASA Astrophysics Data System (ADS)

Rajabi, F.; Battiato, I.

2016-12-01

Long term predictions of the impact of anthropogenic stressors on the environment is essential to reduce the risks associated with processes such as CO2 sequestration and nuclear waste storage in the subsurface. On the other hand, transient forcing factors (e.g. time-varying injection or pumping rate) with evolving heterogeneity of time scales spanning from days to years can influence transport phenomena at the pore scale. A comprehensive spatio-temporal prediction of reactive transport in porous media under time-dependent forcing factors for thousands of years requires the formulation of continuum scale models for time-averages. Yet, as every macroscopic model, time-averaged models can loose predictivity and accuracy when certain conditions are violated. This is true whenever lack of temporal and spatial scale separation occurs and it makes the continuum scale equation a poor assumption for the processes at the pore scale. In this work, we consider mass transport of a dissolved species undergoing a heterogeneous reaction and subject to time-varying boundary conditions in a periodic porous medium. By means of homogenization method and asymptotic expansion technique, we derive a macro-time continuum-scale equation as well as expressions for its effective properties. Our analysis demonstrates that the dynamics at the macro-scale is strongly influenced by the interplay between signal frequency at the boundary and transport processes at the pore level. In addition, we provide the conditions under which the space-time averaged equations accurately describe pore-scale processes. To validate our theoretical predictions, we consider a thin fracture with reacting walls and transient boundary conditions at the inlet. Our analysis shows a good agreement between numerical simulations and theoretical predictions. Furthermore, our numerical experiments show that mixing patterns of the contaminant plumes at the pore level strongly depend on the signal frequency.

Scaling of Transient Storage Parameter Estimates with Increasing Reach Length in a Mountain Headwater Stream

NASA Astrophysics Data System (ADS)

Briggs, M.; Gooseff, M. N.; McGlynn, B.

2006-12-01

. Numerous studies have used the methods of stream tracer experiments and subsequent solute transport modeling to determine transient storage characteristics of streams. Experimental reach length is often determined by site logistics, morphology, specific study goals, etc. Harvey et al. [1996] provided guidance for optimal study reach lengths, based on the Dahmkoler number, as a balance between timescales of advective transport and transient storage. In this study, we investigate the scaling of parameters in a solute transport model (OTIS) with increasing spatial scale of investigation. We conducted 2 6-hour constant rate injections of dissolved NaCl in Spring Park Creek, a headwater stream in the Tenderfoot Creek Experimental Forest, Montana. Below the first injection we sampled 4 reaches ~200m in length, we then moved upstream 640m for the second injection and sampled 3 more ~200 m reaches. Solute transport simulations were conducted for each of these sub-reaches and for combinations of these sub-reaches, from which we assessed estimates of solute velocity, dispersion, transient storage exchange, storage zone size, and Fmed (proportion of median transport time due to storage). Dahmkoler values calculated for each simulation (sub-reaches as well as longer combined reach) were within an order of magnitude of 1, suggesting that our study reach lengths were appropriate. Length-weighted average solute transport and transient storage parameters for the sub-reaches were found to be comparable to their counterparts in the longer reach simulation. In particular the average dispersion found for the sub-reaches (0.43 m2/s) compared very favorably with the value for dispersion calculated for the larger reach (0.40 m2/s). In contrast the weighted average of storage zone size for the sub-reaches was much greater (1.17 m2) than those calculated for the injection reach as a whole (0.09 m2) by a factor of ~13. Weighted average values for transient storage exchange and size for the sub-reaches were both found to be higher than that of the reach as a whole, but only by factors of ~2.5 and 3 respectively. This study indicates that some values of solute transport and transient storage for a particular reach can be reasonably extrapolated from its corresponding component reach values.

Multi-Scale Stochastic Resonance Spectrogram for fault diagnosis of rolling element bearings

NASA Astrophysics Data System (ADS)

He, Qingbo; Wu, Enhao; Pan, Yuanyuan

2018-04-01

It is not easy to identify incipient defect of a rolling element bearing by analyzing the vibration data because of the disturbance of background noise. The weak and unrecognizable transient fault signal of a mechanical system can be enhanced by the stochastic resonance (SR) technique that utilizes the noise in the system. However, it is challenging for the SR technique to identify sensitive fault information in non-stationary signals. This paper proposes a new method called multi-scale SR spectrogram (MSSRS) for bearing defect diagnosis. The new method considers the non-stationary property of the defective bearing vibration signals, and treats every scale of the time-frequency distribution (TFD) as a modulation system. Then the SR technique is utilized on each modulation system according to each frequencies in the TFD. The SR results are sensitive to the defect information because the energy of transient vibration is distributed in a limited frequency band in the TFD. Collecting the spectra of the SR outputs at all frequency scales then generates the MSSRS. The proposed MSSRS is able to well deal with the non-stationary transient signal, and can highlight the defect-induced frequency component corresponding to the impulse information. Experimental results with practical defective bearing vibration data have shown that the proposed method outperforms the former SR methods and exhibits a good application prospect in rolling element bearing fault diagnosis.

Time scales of transient enhanced diffusion: Free and clustered interstitials

NASA Astrophysics Data System (ADS)

Cowern, N. E. B.; Huizing, H. G. A.; Stolk, P. A.; Visser, C. C. G.; de Kruif, R. C. M.; Kyllesbech Larsen, K.; Privitera, V.; Nanver, L. K.; Crans, W.

1996-12-01

Transient enhanced diffusion (TED) and electrical activation after nonamorphizing Si implantations into lightly B-doped Si multilayers shows two distinct timescales, each related to a different class of interstitial defect. At 700°C, ultrafast TED occurs within the first 15 s with a B diffusivity enhancement of > 2 × 10 5. Immobile clustered B is present at low concentration levels after the ultrafast transient and persists for an extended period (˜ 10 2-10 3 s). The later phase of TED exhibits a near-constant diffusivity enhancement of ≈ 1 × 10 4, consistent with interstitial injection controlled by dissolving {113} interstitial clusters. The relative contributions of the ultrafast and regular TED regimes to the final diffusive broadening of the B profile depends on the proportion of interstitials that escape capture by {113} clusters growing within the implant damage region upon annealing. Our results explain the ultrafast TED recently observed after medium-dose B implantation. In that case there are enough B atoms to trap a large proportion of interstitials in SiB clusters, and the remaining interstitials contribute to TED without passing through an intermediate {113} defect stage. The data on the ultrafast TED pulse allows us to extract lower limits for the diffusivities of the Si interstitial ( DI > 2 × 10 -10 cm 2s -1) and the B interstitial(cy) defect ( DBi > 2 × 10 -13 cm 2s -1) at 700°C.

Roll-to-roll Slot-die Printed Polymer Solar Cell by Self-Assembly.

PubMed

Yang, Junyu; Lin, Yuanbao; Zheng, Wenhao; Liu, Alei; Cai, Wanzhu; Yu, Xiaomin; Zhang, Fengling; Liang, Quanbin; Wu, Hongbin; Qin, Donghuan; Hou, Lintao

2018-06-12

Extremely simplified one-step roll-to-roll slot-die printed flexible ITO-free polymer solar cells (PSCs) are demonstrated based on ternary blends of electron-donor polymer thieno [3,4-b]thiophene/benzodithiophene (PTB7), electron-acceptor fullerene [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) and electron extracting polymer poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) at room temperature (RT) in ambient air. The flexible ITO-free PSC exhibits a comparable power conversion efficiency (PCE) with the device employing complicated two-step slot-die printing (5.29% vs 5.41%), which indicates that PFN molecules can migrate from the ternary nanocomposite towards Ag cathode via vertical self-assembly during the one-step slot-die printing process in air. To confirm the migration of PFN, the morphology and elemental analysis as well as charge transport of different active layers are investigated with in-situ transient film drying process, transmission electron microscopy, atomic force microscopy, contact angle and surface energy, X-ray photoelectron spectroscopy, scanning electron microscope, impedance spectroscopy, transient photovoltage and transient photocurrent as well as laser beam induced current. Moreover, the good air and mechanical stability of the flexible device with a decent PCE achieved in 1 cm2 PSCs at RT in air suggests the feasibility of energy-saving and time-saving one-step slot-die printing to large-scale roll-to-roll manufacture in the future.

Research on photodiode detector-based spatial transient light detection and processing system

NASA Astrophysics Data System (ADS)

Liu, Meiying; Wang, Hu; Liu, Yang; Zhao, Hui; Nan, Meng

2016-10-01

In order to realize real-time signal identification and processing of spatial transient light, the features and the energy of the captured target light signal are first described and quantitatively calculated. Considering that the transient light signal has random occurrence, a short duration and an evident beginning and ending, a photodiode detector based spatial transient light detection and processing system is proposed and designed in this paper. This system has a large field of view and is used to realize non-imaging energy detection of random, transient and weak point target under complex background of spatial environment. Weak signal extraction under strong background is difficult. In this paper, considering that the background signal changes slowly and the target signal changes quickly, filter is adopted for signal's background subtraction. A variable speed sampling is realized by the way of sampling data points with a gradually increased interval. The two dilemmas that real-time processing of large amount of data and power consumption required by the large amount of data needed to be stored are solved. The test results with self-made simulative signal demonstrate the effectiveness of the design scheme. The practical system could be operated reliably. The detection and processing of the target signal under the strong sunlight background was realized. The results indicate that the system can realize real-time detection of target signal's characteristic waveform and monitor the system working parameters. The prototype design could be used in a variety of engineering applications.

Effective image differencing with convolutional neural networks for real-time transient hunting

NASA Astrophysics Data System (ADS)

Sedaghat, Nima; Mahabal, Ashish

2018-06-01

Large sky surveys are increasingly relying on image subtraction pipelines for real-time (and archival) transient detection. In this process one has to contend with varying point-spread function (PSF) and small brightness variations in many sources, as well as artefacts resulting from saturated stars and, in general, matching errors. Very often the differencing is done with a reference image that is deeper than individual images and the attendant difference in noise characteristics can also lead to artefacts. We present here a deep-learning approach to transient detection that encapsulates all the steps of a traditional image-subtraction pipeline - image registration, background subtraction, noise removal, PSF matching and subtraction - in a single real-time convolutional network. Once trained, the method works lightening-fast and, given that it performs multiple steps in one go, the time saved and false positives eliminated for multi-CCD surveys like Zwicky Transient Facility and Large Synoptic Survey Telescope will be immense, as millions of subtractions will be needed per night.

Recent Results on SNRs and PWNe from the Fermi Large Area Telescope

NASA Technical Reports Server (NTRS)

Hays, Elizabeth

2010-01-01

Topics include: Fermi LAT Collaboration groups; galactic results from LAT; a GeV, wide-field instrument; the 1FGL catalog, the Fermi LAT 1FGL source catalog, unidentified gamma-ray sources; variability in 1FGL sources; curvature in 1FGL sources; spectral-variability classification; pulsars and their wind nebulae; gamma-ray pulsars and MSPs; GeV PWN search; Crab pulsar and nebula; Vela X nebular of Vela pulsar; MSH 15-52; supernova remnants, resolved GeV sources, galactic transients, LAT unassociated transient detections; gamma rays from a nova; V407 Cyngi - a symbiotic nova; V407 Cygni: a variable star; and March 11 - a nova. Summary slides include pulsars everywhere, blazars, LAT as an electron detector, cosmic ray spectrum, the Large Area Telescope, the Fermi Observatory, LAT sensitivity with time, candidate gamma-ray events, on-orbit energy calibration and rate, a 1 year sky map, LAT automated science processing, reported GeV flares, early activity and spectacular flare, gamma-ray transients near the galactic plane , two early unassociated transients, counter part search - Fermi J0910-5404; counterpart search 3EG J0903-3531, and a new LAT transient - J1057-6027.

Fabrication and characterization of controllable grain boundary arrays in solution-processed small molecule organic semiconductor films

NASA Astrophysics Data System (ADS)

Wo, Songtao; Headrick, Randall L.; Anthony, John E.

2012-04-01

We have produced solution-processed thin films of 6,13-bis(tri-isopropyl-silylethynyl) pentacene with grain sizes from a few micrometers up to millimeter scale by lateral crystallization from a rectangular stylus. Grains are oriented along the crystallization direction, and the grain size transverse to the crystallization direction depends inversely on the writing speed, hence forming a regular array of oriented grain boundaries with controllable spacing. We utilize these controllable arrays to systematically study the role of large-angle grain boundaries in carrier transport and charge trapping in thin film transistors. The effective mobility scales with the grain size, leading to an estimate of the potential drop at individual large-angle grain boundaries of more than 1 volt. This result indicates that the structure of grain boundaries is not molecularly abrupt, which may be a general feature of solution-processed small molecule organic semiconductor thin films, where relatively high energy grain boundaries are typically formed. Transient measurements after switching from positive to negative gate bias or between large and small negative gate bias reveal reversible charge trapping, with time constants on the order of 10 s and trap densities that are correlated with grain boundary density. We suggest that charge diffusion along grain boundaries and other defects is the rate-determining mechanism of the reversible trapping.

Temporal evolution of continental lithospheric strength in actively deforming regions

USGS Publications Warehouse

Thatcher, W.; Pollitz, F.F.

2008-01-01

It has been agreed for nearly a century that a strong, load-bearing outer layer of earth is required to support mountain ranges, transmit stresses to deform active regions and store elastic strain to generate earthquakes. However the dept and extent of this strong layer remain controversial. Here we use a variety of observations to infer the distribution of lithospheric strength in the active western United States from seismic to steady-state time scales. We use evidence from post-seismic transient and earthquake cycle deformation reservoir loading glacio-isostatic adjustment, and lithosphere isostatic adjustment to large surface and subsurface loads. The nearly perfectly elastic behavior of Earth's crust and mantle at the time scale of seismic wave propagation evolves to that of a strong, elastic crust and weak, ductile upper mantle lithosphere at both earthquake cycle (EC, ???10?? to 103 yr) and glacio-isostatic adjustment (GIA, ???103 to 104 yr) time scales. Topography and gravity field correlations indicate that lithosphere isostatic adjustment (LIA) on ???106-107 yr time scales occurs with most lithospheric stress supported by an upper crust overlying a much weaker ductile subtrate. These comparisons suggest that the upper mantle lithosphere is weaker than the crust at all time scales longer than seismic. In contrast, the lower crust has a chameleon-like behavior, strong at EC and GIA time scales and weak for LIA and steady-state deformation processes. The lower crust might even take on a third identity in regions of rapid crustal extension or continental collision, where anomalously high temperatures may lead to large-scale ductile flow in a lower crustal layer that is locally weaker than the upper mantle. Modeling of lithospheric processes in active regions thus cannot use a one-size-fits-all prescription of rheological layering (relation between applied stress and deformation as a function of depth) but must be tailored to the time scale and tectonic setting of the process being investigated.

Zolpidem Reduces Hippocampal Neuronal Activity in Freely Behaving Mice: A Large Scale Calcium Imaging Study with Miniaturized Fluorescence Microscope

PubMed Central

Berdyyeva, Tamara; Otte, Stephani; Aluisio, Leah; Ziv, Yaniv; Burns, Laurie D.; Dugovic, Christine; Yun, Sujin; Ghosh, Kunal K.; Schnitzer, Mark J.; Lovenberg, Timothy; Bonaventure, Pascal

2014-01-01

Therapeutic drugs for cognitive and psychiatric disorders are often characterized by their molecular mechanism of action. Here we demonstrate a new approach to elucidate drug action on large-scale neuronal activity by tracking somatic calcium dynamics in hundreds of CA1 hippocampal neurons of pharmacologically manipulated behaving mice. We used an adeno-associated viral vector to express the calcium sensor GCaMP3 in CA1 pyramidal cells under control of the CaMKII promoter and a miniaturized microscope to observe cellular dynamics. We visualized these dynamics with and without a systemic administration of Zolpidem, a GABAA agonist that is the most commonly prescribed drug for the treatment of insomnia in the United States. Despite growing concerns about the potential adverse effects of Zolpidem on memory and cognition, it remained unclear whether Zolpidem alters neuronal activity in the hippocampus, a brain area critical for cognition and memory. Zolpidem, when delivered at a dose known to induce and prolong sleep, strongly suppressed CA1 calcium signaling. The rate of calcium transients after Zolpidem administration was significantly lower compared to vehicle treatment. To factor out the contribution of changes in locomotor or physiological conditions following Zolpidem treatment, we compared the cellular activity across comparable epochs matched by locomotor and physiological assessments. This analysis revealed significantly depressive effects of Zolpidem regardless of the animal’s state. Individual hippocampal CA1 pyramidal cells differed in their responses to Zolpidem with the majority (∼65%) significantly decreasing the rate of calcium transients, and a small subset (3%) showing an unexpected and significant increase. By linking molecular mechanisms with the dynamics of neural circuitry and behavioral states, this approach has the potential to contribute substantially to the development of new therapeutics for the treatment of CNS disorders. PMID:25372144

Exploring Low-Amplitude, Long-Duration Deformational Transients on the Cascadia Subduction Zone

NASA Astrophysics Data System (ADS)

Nuyen, C.; Schmidt, D. A.

2017-12-01

The absence of long-term slow slip events (SSEs) in Cascadia is enigmatic on account of the diverse group of subduction zone systems that do experience long-term SSEs. In particular, southwest Japan, Alaska, New Zealand and Mexico have observed long-term SSEs, with some of the larger events exhibiting centimeter-scale surface displacements over the course of multiple years. The conditions that encourage long-term slow slip are not well established due to the variability in thermal parameter and plate dip amongst subduction zones that host long-term events. The Cascadia Subduction Zone likely has the capacity to host long-term SSEs, and the lack of such events motivates further exploration of the observational data. In order to search for the existence of long-duration transients in surface displacements, we examine Cascadia GPS time series from PANGA and PBO to determine whether or not Cascadia has hosted a long-term slow slip event in the past 20 years. A careful review of the time series does not reveal any large-scale multi-year transients. In order to more clearly recognize possible small amplitude long-term SSEs in Cascadia, the GPS time series are reduced with two separate methods. The first method involves manually removing (1) continental water loading terms, (2) transient displacements of known short-term SSEs, and (3) common mode signals that span the network. The second method utilizes a seasonal-trend decomposition procedure (STL) to extract a long-term trend from the GPS time-series. Manual inspection of both of these products reveals intriguing long-term changes in the longitudinal component of several GPS stations in central Cascadia. To determine whether these shifts could be due to long-term slow slip, we invert the reduced surface displacement time series for fault slip using a principle component analysis-based inversion method. We also utilize forward fault models of various synthetic long-term SSEs to better understand how these events may appear in the time series for a range of magnitudes and durations. Results from this research have direct implications for the possible slip modes in Cascadia and how variations in slip over time can impact stress and strain accumulations along the margin.

Autonomic consequences of arousal from sleep: mechanisms and implications.

PubMed

Horner, R L

1996-12-01

Normal spontaneous arousals from sleep are associated with transient increases in blood pressure, heart rate, and ventilation caused by large transient changes in autonomic output. These autonomic changes are out of proportion to obvious physiological need and are in excess of those observed in later periods of quiet wakefulness. This paper discusses some of the mechanisms underlying the cardio-respiratory consequences of arousal from sleep, and discusses why the normal onset of wakefulness may be associated with such large changes in autonomic output.

A new perspective on the regional hydrologic cycle over North and South America

NASA Astrophysics Data System (ADS)

Weng, Shu-Ping

The GEOS-1 vertically-integrated 3-hr moisture flux reanalyses and hourly-gridded United States station precipitation plus a satellite-based, 6-hr global precipitation estimate were employed to investigate the impacts of nocturnal low-level jets (LLJs) on the regional hydrological cycle over the central United States (Part I) and the subtropical plains of South America (Part II). Research stressed the influences of upper-level synoptic-scale waves (i.e., synoptic-scale forcings) upon the regional hydrologic processes, which were explored by the impacts associated with the occurrence of LLJ. Besides the conventional budget analysis, the adopted `synoptic-forcing approach' was proven illustrative in describing these impacts through the down-scaling process of LLJs. In Part 1, the major findings include: (1)the seasonal-averaged hydrological cycle over the Great Plains is strongly affected by the occurrence of GPLLJ, (2)the synoptic-scale forcing provided by the upper-level propagating jet (ULJ) streams is essential in generating the large-scale precipitation after the GPLLJ forms from the diurnal boundary layer process, (3)without the dynamic coupling between the ULJ and LLJ, the impact of LLJ on the hydrological cycle is demonstrated to be less important, and (4)the importance of synoptic-scale forcings in preconditioning the setting of wet/dry seasons in the interannual variability of rainfall anomaly is further illustrated by examining the changes of intensity as well as the occurrence frequency between the different types of LLJ. In Part II of this study, it was found that the occurrence of Andean LLJ represents a transient episode that detours the climatic rainfall activity along the South Atlantic Convergent Zone (SACZ) to the subtropical plains (Brazilian Nordeste) in its southwestern (northeastern) flank. The appearance of a seesaw pattern in the rainfall and flux convergence anomalies along the southeastern portion of South America, which is spatially in quadrature with the seasonal mean circulation, reflects the synoptic-scale forcing generated by the upper-level propagating transient-scale waves. In this regard, the function of the Andean LLJ in providing a scale-interaction mechanism that links the synoptic-scale setting with the localized rainfall event is the same as the GPLLJ. Due to the unique geographic background such as the narrow east-west landmass extension and the relative orientation between the Andean LLJ and the ULJ, however, the enhanced rainfall activity over the subtropical plains in response to the perturbed flux convergence is smaller than the case in the GPLLJ.

Characterization of Regular Wave, Irregular Wave, and Large-Amplitude Wave Group Kinematics in an Experimental Basin

DTIC Science & Technology

2011-02-01

seakeeping was the transient wave technique, developed analytically by Davis and Zarnick (1964). At the David Taylor Model Basin, Davis and Zarnick, and...Gersten and Johnson (1969) applied the transient wave technique to regular wave model experiments for heave and pitch, at zero forward speed. These...tests demonstrated a potential reduction by an order of magnitude of the total necessary testing time. The transient wave technique was also applied to

Experimental Investigation of Bearing Slip in a Wind Turbine Gearbox During a Transient Grid Loss Event

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

Helsen, Jan; Guo, Yi; Keller, Jonathan

This work investigates the behaviour of the high speed stage of a wind turbine gearbox during a transient grid loss event. Dynamometer testing on a full scale wind turbine nacelle is used. A combination of external and internal gearbox measurements is analysed. Particular focus is on the characterization of the high speed shaft tapered roller bearing slip behaviour. This slipping behaviour is linked to dynamic events by many researchers and described as potential bearing failure initiator. However only limited full scale dynamic testing is documented. Strain gauge bridges in grooves along the circumference of the outer ring are used tomore » characterize the bearing behaviour in detail. It is shown that during the transient event the high speed shaft experiences a combined torsional and bending deformation. These unfavourable loading conditions induce roller slip in the bearings during the torque reversals indicating the potential of the applied load case to go beyond the preload of the tapered roller bearing.« less

Optimization of Computational Performance and Accuracy in 3-D Transient CFD Model for CFB Hydrodynamics Predictions

NASA Astrophysics Data System (ADS)

Rampidis, I.; Nikolopoulos, A.; Koukouzas, N.; Grammelis, P.; Kakaras, E.

2007-09-01

This work aims to present a pure 3-D CFD model, accurate and efficient, for the simulation of a pilot scale CFB hydrodynamics. The accuracy of the model was investigated as a function of the numerical parameters, in order to derive an optimum model setup with respect to computational cost. The necessity of the in depth examination of hydrodynamics emerges by the trend to scale up CFBCs. This scale up brings forward numerous design problems and uncertainties, which can be successfully elucidated by CFD techniques. Deriving guidelines for setting a computational efficient model is important as the scale of the CFBs grows fast, while computational power is limited. However, the optimum efficiency matter has not been investigated thoroughly in the literature as authors were more concerned for their models accuracy and validity. The objective of this work is to investigate the parameters that influence the efficiency and accuracy of CFB computational fluid dynamics models, find the optimum set of these parameters and thus establish this technique as a competitive method for the simulation and design of industrial, large scale beds, where the computational cost is otherwise prohibitive. During the tests that were performed in this work, the influence of turbulence modeling approach, time and space density and discretization schemes were investigated on a 1.2 MWth CFB test rig. Using Fourier analysis dominant frequencies were extracted in order to estimate the adequate time period for the averaging of all instantaneous values. The compliance with the experimental measurements was very good. The basic differences between the predictions that arose from the various model setups were pointed out and analyzed. The results showed that a model with high order space discretization schemes when applied on a coarse grid and averaging of the instantaneous scalar values for a 20 sec period, adequately described the transient hydrodynamic behaviour of a pilot CFB while the computational cost was kept low. Flow patterns inside the bed such as the core-annulus flow and the transportation of clusters were at least qualitatively captured.

Transient coherence of media under strong phase modulation exploiting electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Shwa, David; Katz, Nadav

2014-08-01

When quantum systems are shifted faster than their transition and coupling time scales, their susceptibility is dramatically modified. We measure the optical susceptibility of a strongly modulated electromagnetically induced transparency system. Time vs detuning plots for different pump modulation frequencies reveal a transition between an adiabatic regime where a series of smooth pulses are created and a nonadiabatic regime where a strong transient oscillating response is added. Applying a magnetic field lifts the hyperfine level degeneracy, revealing an interference effect between the different magnetic level transients. We explore the dynamics of the magnetic and nonmagnetic cases and discuss their coherent nature. We finally combine the global phase of the transmitted pulses with the transient interference to achieve broadband magnetic sensing without losing the sensitivity of a single electromagnetically induced transparency line.

Comparative Model Evaluation Studies of Biogenic Trace Gas Fluxes in Tropical Forests

NASA Technical Reports Server (NTRS)

Potter, C. S.; Peterson, David L. (Technical Monitor)

1997-01-01

Simulation modeling can play a number of important roles in large-scale ecosystem studies, including synthesis of patterns and changes in carbon and nutrient cycling dynamics, scaling up to regional estimates, and formulation of testable hypotheses for process studies. Recent comparative studies have shown that ecosystem models of soil trace gas exchange with the atmosphere are evolving into several distinct simulation approaches. Different levels of detail exist among process models in the treatment of physical controls on ecosystem nutrient fluxes and organic substrate transformations leading to gas emissions. These differences are is in part from distinct objectives of scaling and extrapolation. Parameter requirements for initialization scalings, boundary conditions, and time-series driven therefore vary among ecosystem simulation models, such that the design of field experiments for integration with modeling should consider a consolidated series of measurements that will satisfy most of the various model requirements. For example, variables that provide information on soil moisture holding capacity, moisture retention characteristics, potential evapotranspiration and drainage rates, and rooting depth appear to be of the first order in model evaluation trials for tropical moist forest ecosystems. The amount and nutrient content of labile organic matter in the soil, based on accurate plant production estimates, are also key parameters that determine emission model response. Based on comparative model results, it is possible to construct a preliminary evaluation matrix along categories of key diagnostic parameters and temporal domains. Nevertheless, as large-scale studied are planned, it is notable that few existing models age designed to simulate transient states of ecosystem change, a feature which will be essential for assessment of anthropogenic disturbance on regional gas budgets, and effects of long-term climate variability on biosphere-atmosphere exchange.

Time-Frequency Analysis of Rocket Nozzle Wall Pressures During Start-up Transients

NASA Technical Reports Server (NTRS)

Baars, Woutijn J.; Tinney, Charles E.; Ruf, Joseph H.

2011-01-01

Surveys of the fluctuating wall pressure were conducted on a sub-scale, thrust- optimized parabolic nozzle in order to develop a physical intuition for its Fourier-azimuthal mode behavior during fixed and transient start-up conditions. These unsteady signatures are driven by shock wave turbulent boundary layer interactions which depend on the nozzle pressure ratio and nozzle geometry. The focus however, is on the degree of similarity between the spectral footprints of these modes obtained from transient start-ups as opposed to a sequence of fixed nozzle pressure ratio conditions. For the latter, statistically converged spectra are computed using conventional Fourier analyses techniques, whereas the former are investigated by way of time-frequency analysis. The findings suggest that at low nozzle pressure ratios -- where the flow resides in a Free Shock Separation state -- strong spectral similarities occur between fixed and transient conditions. Conversely, at higher nozzle pressure ratios -- where the flow resides in Restricted Shock Separation -- stark differences are observed between the fixed and transient conditions and depends greatly on the ramping rate of the transient period. And so, it appears that an understanding of the dynamics during transient start-up conditions cannot be furnished by a way of fixed flow analysis.

Evaluation of the eigenvalue method in the solution of transient heat conduction problems

NASA Astrophysics Data System (ADS)

Landry, D. W.

1985-01-01

The eigenvalue method is evaluated to determine the advantages and disadvantages of the method as compared to fully explicit, fully implicit, and Crank-Nicolson methods. Time comparisons and accuracy comparisons are made in an effort to rank the eigenvalue method in relation to the comparison schemes. The eigenvalue method is used to solve the parabolic heat equation in multidimensions with transient temperatures. Extensions into three dimensions are made to determine the method's feasibility in handling large geometry problems requiring great numbers of internal mesh points. The eigenvalue method proves to be slightly better in accuracy than the comparison routines because of an exact treatment, as opposed to a numerical approximation, of the time derivative in the heat equation. It has the potential of being a very powerful routine in solving long transient type problems. The method is not well suited to finely meshed grid arrays or large regions because of the time and memory requirements necessary for calculating large sets of eigenvalues and eigenvectors.

Hydraulic transients in the long diversion-type hydropower station with a complex differential surge tank.

PubMed

Yu, Xiaodong; Zhang, Jian; Zhou, Ling

2014-01-01

Based on the theory of hydraulic transients and the method of characteristics (MOC), a mathematic model of the differential surge tank with pressure-reduction orifices (PROs) and overflow weirs for transient calculation is proposed. The numerical model of hydraulic transients is established using the data of a practical hydropower station; and the probable transients are simulated. The results show that successive load rejection is critical for calculating the maximum pressure in spiral case and the maximum rotating speed of runner when the bifurcated pipe is converging under the surge tank in a diversion-type hydropower station; the pressure difference between two sides of breast wall is large during transient conditions, and it would be more serious when simultaneous load rejections happen after load acceptance; the reasonable arrangement of PROs on breast wall can effectively decrease the pressure difference.

Hydraulic Transients in the Long Diversion-Type Hydropower Station with a Complex Differential Surge Tank

PubMed Central

Yu, Xiaodong; Zhang, Jian

2014-01-01

Based on the theory of hydraulic transients and the method of characteristics (MOC), a mathematic model of the differential surge tank with pressure-reduction orifices (PROs) and overflow weirs for transient calculation is proposed. The numerical model of hydraulic transients is established using the data of a practical hydropower station; and the probable transients are simulated. The results show that successive load rejection is critical for calculating the maximum pressure in spiral case and the maximum rotating speed of runner when the bifurcated pipe is converging under the surge tank in a diversion-type hydropower station; the pressure difference between two sides of breast wall is large during transient conditions, and it would be more serious when simultaneous load rejections happen after load acceptance; the reasonable arrangement of PROs on breast wall can effectively decrease the pressure difference. PMID:25133213

The Volumetric Rate of Calcium-rich Transients in the Local Universe

DOE PAGES

Frohmaier, Chris; Sullivan, Mark; Maguire, Kate; ...

2018-05-04

Here, we present a measurement of the volumetric rate of "calcium-rich" optical transients in the local universe, using a sample of three events from the Palomar Transient Factory (PTF). This measurement builds on a detailed study of the PTF transient detection efficiencies and uses a Monte Carlo simulation of the PTF survey. We measure the volumetric rate of calcium-rich transients to be higher than previous estimates: 1.21 -0.39 +1.13 10 -5 events yr -1Mpc -3. This is equivalent to 33%-94% of the local volumetric Type Ia supernova rate. This calcium-rich transient rate is sufficient to reproduce the observed calcium abundancesmore » in galaxy clusters, assuming an asymptotic calcium yield per calcium-rich event of ~0.05 M ⊙. As a result, we also study the PTF detection efficiency of these transients as a function of position within their candidate host galaxies. We confirm as a real physical effect previous results that suggest that calcium-rich transients prefer large physical offsets from their host galaxies.« less

Neuroprotective effects of ischemic preconditioning on hippocampal CA1 pyramidal neurons through maintaining calbindin D28k immunoreactivity following subsequent transient cerebral ischemia

PubMed Central

Kim, In Hye; Jeon, Yong Hwan; Lee, Tae-Kyeong; Cho, Jeong Hwi; Lee, Jae-Chul; Park, Joon Ha; Ahn, Ji Hyeon; Shin, Bich-Na; Kim, Yang Hee; Hong, Seongkweon; Yan, Bing Chun; Won, Moo-Ho; Lee, Yun Lyul

2017-01-01

Ischemic preconditioning elicited by a non-fatal brief occlusion of blood flow has been applied for an experimental therapeutic strategy against a subsequent fatal ischemic insult. In this study, we investigated the neuroprotective effects of ischemic preconditioning (2-minute transient cerebral ischemia) on calbindin D28k immunoreactivity in the gerbil hippocampal CA1 area following a subsequent fatal transient ischemic insult (5-minute transient cerebral ischemia). A large number of pyramidal neurons in the hippocampal CA1 area died 4 days after 5-minute transient cerebral ischemia. Ischemic preconditioning reduced the death of pyramidal neurons in the hippocampal CA1 area. Calbindin D28k immunoreactivity was greatly attenuated at 2 days after 5-minute transient cerebral ischemia and it was hardly detected at 5 days post-ischemia. Ischemic preconditioning maintained calbindin D28k immunoreactivity after transient cerebral ischemia. These findings suggest that ischemic preconditioning can attenuate transient cerebral ischemia-caused damage to the pyramidal neurons in the hippocampal CA1 area through maintaining calbindin D28k immunoreactivity. PMID:28761424

Numerical study of vortex rope during load rejection of a prototype pump-turbine

NASA Astrophysics Data System (ADS)

Liu, J. T.; Liu, S. H.; Sun, Y. K.; Wu, Y. L.; Wang, L. Q.

2012-11-01

A transient process of load rejection of a prototype pump-turbine was studied by three dimensional, unsteady simulations, as well as steady calculations.Dynamic mesh (DM) method and remeshing method were used to simulate the rotation of guide vanes and runner. The rotational speed of the runner was predicted by fluid couplingmethod. Both the transient calculation and steady calculation were performed based on turbulence model. Results show that steady calculation results have large error in the prediction of the external characteristics of the transient process. The runaway speed can reach 1.15 times the initial rotational speed during the transient process. The vortex rope occurs before the pump-turbine runs at zero moment point. Vortex rope has the same rotating direction with the runner. The vortex rope is separated into two parts as the flow rate decreases to 0. Pressure level decreases during the whole transient process.The transient simulation result were also compared and verified by experimental results. This computational method could be used in the fault diagnosis of transient operation, as well as the optimization of a transient process.

The Volumetric Rate of Calcium-rich Transients in the Local Universe

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

Frohmaier, Chris; Sullivan, Mark; Maguire, Kate

Here, we present a measurement of the volumetric rate of "calcium-rich" optical transients in the local universe, using a sample of three events from the Palomar Transient Factory (PTF). This measurement builds on a detailed study of the PTF transient detection efficiencies and uses a Monte Carlo simulation of the PTF survey. We measure the volumetric rate of calcium-rich transients to be higher than previous estimates: 1.21 -0.39 +1.13 10 -5 events yr -1Mpc -3. This is equivalent to 33%-94% of the local volumetric Type Ia supernova rate. This calcium-rich transient rate is sufficient to reproduce the observed calcium abundancesmore » in galaxy clusters, assuming an asymptotic calcium yield per calcium-rich event of ~0.05 M ⊙. As a result, we also study the PTF detection efficiency of these transients as a function of position within their candidate host galaxies. We confirm as a real physical effect previous results that suggest that calcium-rich transients prefer large physical offsets from their host galaxies.« less

On the use of variability time-scales as an early classifier of radio transients and variables

NASA Astrophysics Data System (ADS)

Pietka, M.; Staley, T. D.; Pretorius, M. L.; Fender, R. P.

2017-11-01

We have shown previously that a broad correlation between the peak radio luminosity and the variability time-scales, approximately L ∝ τ5, exists for variable synchrotron emitting sources and that different classes of astrophysical sources occupy different regions of luminosity and time-scale space. Based on those results, we investigate whether the most basic information available for a newly discovered radio variable or transient - their rise and/or decline rate - can be used to set initial constraints on the class of events from which they originate. We have analysed a sample of ≈800 synchrotron flares, selected from light curves of ≈90 sources observed at 5-8 GHz, representing a wide range of astrophysical phenomena, from flare stars to supermassive black holes. Selection of outbursts from the noisy radio light curves has been done automatically in order to ensure reproducibility of results. The distribution of rise/decline rates for the selected flares is modelled as a Gaussian probability distribution for each class of object, and further convolved with estimated areal density of that class in order to correct for the strong bias in our sample. We show in this way that comparing the measured variability time-scale of a radio transient/variable of unknown origin can provide an early, albeit approximate, classification of the object, and could form part of a suite of measurements used to provide early categorization of such events. Finally, we also discuss the effect scintillating sources will have on our ability to classify events based on their variability time-scales.

Experimental transient and permanent deformation studies of steel-sphere-impacted or impulsively-loaded aluminum beams with clamped ends

NASA Technical Reports Server (NTRS)

Witmer, E. A.

1975-01-01

The sheet explosive loading technique (SELT) was employed to obtain elastic-plastic, large-deflection transient and/or permanent strain data on simple well-defined structural specimens and materials: initially-flat 6061-T651 aluminum beams with both ends ideally clamped via integral construction. The SELT loading technique was chosen since it is both convenient and provides forcing function information of small uncertainty. These data will be useful for evaluating pertinent structural response prediction methods. A second objective was to obtain high-quality transient-strain data for a well-defined structural/material model subjected to impact by a rigid body of known mass, impact velocity, and geometry; large-deflection, elastic-plastic transient response conditions are of primary interest. The beam with both ends clamped and a steel sphere as the impacting body were chosen. The steel sphere was launched vertically by explosive propulsion to achieve various desired impact velocities. The sphere/beam impact tests resulted in producing a wide range of structural responses and permanent deformations, including rupture of the beam from excessive structural response in two cases. The transient and permanent strain data as well as the permanent deflection data obtained are of high quality and should be useful for checking and evaluating methods for predicting the responses of simple 2-d structures to fragment (sphere) impact. Transient strain data very close to the point of impact were not obtained over as long a time as desirable because the gage(s) in that region became detached during the transient response.

Detecting switching and intermittent causalities in time series

NASA Astrophysics Data System (ADS)

Zanin, Massimiliano; Papo, David

2017-04-01

During the last decade, complex network representations have emerged as a powerful instrument for describing the cross-talk between different brain regions both at rest and as subjects are carrying out cognitive tasks, in healthy brains and neurological pathologies. The transient nature of such cross-talk has nevertheless by and large been neglected, mainly due to the inherent limitations of some metrics, e.g., causality ones, which require a long time series in order to yield statistically significant results. Here, we present a methodology to account for intermittent causal coupling in neural activity, based on the identification of non-overlapping windows within the original time series in which the causality is strongest. The result is a less coarse-grained assessment of the time-varying properties of brain interactions, which can be used to create a high temporal resolution time-varying network. We apply the proposed methodology to the analysis of the brain activity of control subjects and alcoholic patients performing an image recognition task. Our results show that short-lived, intermittent, local-scale causality is better at discriminating both groups than global network metrics. These results highlight the importance of the transient nature of brain activity, at least under some pathological conditions.

Measuring thermal conductivity of thin films and coatings with the ultra-fast transient hot-strip technique

NASA Astrophysics Data System (ADS)

Belkerk, B. E.; Soussou, M. A.; Carette, M.; Djouadi, M. A.; Scudeller, Y.

2012-07-01

This paper reports the ultra-fast transient hot-strip (THS) technique for determining the thermal conductivity of thin films and coatings of materials on substrates. The film thicknesses can vary between 10 nm and more than 10 µm. Precise measurement of thermal conductivity was performed with an experimental device generating ultra-short electrical pulses, and subsequent temperature increases were electrically measured on nanosecond and microsecond time scales. The electrical pulses were applied within metallized micro-strips patterned on the sample films and the temperature increases were analysed within time periods selected in the window [100 ns-10 µs]. The thermal conductivity of the films was extracted from the time-dependent thermal impedance of the samples derived from a three-dimensional heat diffusion model. The technique is described and its performance demonstrated on different materials covering a large thermal conductivity range. Experiments were carried out on bulk Si and thin films of amorphous SiO2 and crystallized aluminum nitride (AlN). The present approach can assess film thermal resistances as low as 10-8 K m2 W-1 with a precision of about 10%. This has never been attained before with the THS technique.

Dynamic reconfiguration of frontal brain networks during executive cognition in humans

PubMed Central

Braun, Urs; Schäfer, Axel; Walter, Henrik; Erk, Susanne; Romanczuk-Seiferth, Nina; Haddad, Leila; Schweiger, Janina I.; Grimm, Oliver; Heinz, Andreas; Tost, Heike; Meyer-Lindenberg, Andreas; Bassett, Danielle S.

2015-01-01

The brain is an inherently dynamic system, and executive cognition requires dynamically reconfiguring, highly evolving networks of brain regions that interact in complex and transient communication patterns. However, a precise characterization of these reconfiguration processes during cognitive function in humans remains elusive. Here, we use a series of techniques developed in the field of “dynamic network neuroscience” to investigate the dynamics of functional brain networks in 344 healthy subjects during a working-memory challenge (the “n-back” task). In contrast to a control condition, in which dynamic changes in cortical networks were spread evenly across systems, the effortful working-memory condition was characterized by a reconfiguration of frontoparietal and frontotemporal networks. This reconfiguration, which characterizes “network flexibility,” employs transient and heterogeneous connectivity between frontal systems, which we refer to as “integration.” Frontal integration predicted neuropsychological measures requiring working memory and executive cognition, suggesting that dynamic network reconfiguration between frontal systems supports those functions. Our results characterize dynamic reconfiguration of large-scale distributed neural circuits during executive cognition in humans and have implications for understanding impaired cognitive function in disorders affecting connectivity, such as schizophrenia or dementia. PMID:26324898

Structural imaging of nanoscale phonon transport in ferroelectrics excited by metamaterial-enhanced terahertz fields

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

Zhu, Yi; Chen, Frank; Park, Joonkyu

Nanoscale phonon transport is a key process that governs thermal conduction in a wide range of materials and devices. Creating controlled phonon populations by resonant excitation at terahertz (THz) frequencies can drastically change the characteristics of nanoscale thermal transport and allow a direct real-space characterization of phonon mean-free paths. Using metamaterial-enhanced terahertz excitation, we tailored a phononic excitation by selectively populating low-frequency phonons within a nanoscale volume in a ferroelectric BaTiO3 thin film. Real-space time-resolved x-ray diffraction microscopy following THz excitation reveals ballistic phonon transport over a distance of hundreds of nm, two orders of magnitude longer than the averagedmore » phonon mean-free path in BaTiO3. On longer length scales, diffusive phonon transport dominates the recovery of the transient strain response, largely due to heat conduction into the substrate. The measured real-space phonon transport can be directly compared with the phonon mean-free path as predicted by molecular dynamics modeling. This time-resolved real-space visualization of THz-matter interactions opens up opportunities to engineer and image nanoscale transient structural states with new functionalities.« less

Structural imaging of nanoscale phonon transport in ferroelectrics excited by metamaterial-enhanced terahertz fields

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

Zhu, Yi; Chen, Frank; Park, Joonkyu

Nanoscale phonon transport is a key process that governs thermal conduction in a wide range of materials and devices. Creating controlled phonon populations by resonant excitation at terahertz (THz) frequencies can drastically change the characteristics of nanoscale thermal transport and allow a direct real-space characterization of phonon mean-free paths. Using metamaterial-enhanced terahertz excitation, we tailored a phononic excitation by selectively populating low-frequency phonons within a nanoscale volume in a ferroelectric BaTiO 3 thin film. Real-space time-resolved x-ray diffraction microscopy following THz excitation reveals ballistic phonon transport over a distance of hundreds of nm, two orders of magnitude longer than themore » averaged phonon mean-free path in BaTiO 3. On longer length scales, diffusive phonon transport dominates the recovery of the transient strain response, largely due to heat conduction into the substrate. The measured real-space phonon transport can be directly compared with the phonon mean-free path as predicted by molecular dynamics modeling. In conclusion, this time-resolved real-space visualization of THz-matter interactions opens up opportunities to engineer and image nanoscale transient structural states with new functionalities.« less

An efficient and stable hydrodynamic model with novel source term discretization schemes for overland flow and flood simulations

NASA Astrophysics Data System (ADS)

Xia, Xilin; Liang, Qiuhua; Ming, Xiaodong; Hou, Jingming

2017-05-01

Numerical models solving the full 2-D shallow water equations (SWEs) have been increasingly used to simulate overland flows and better understand the transient flow dynamics of flash floods in a catchment. However, there still exist key challenges that have not yet been resolved for the development of fully dynamic overland flow models, related to (1) the difficulty of maintaining numerical stability and accuracy in the limit of disappearing water depth and (2) inaccurate estimation of velocities and discharges on slopes as a result of strong nonlinearity of friction terms. This paper aims to tackle these key research challenges and present a new numerical scheme for accurately and efficiently modeling large-scale transient overland flows over complex terrains. The proposed scheme features a novel surface reconstruction method (SRM) to correctly compute slope source terms and maintain numerical stability at small water depth, and a new implicit discretization method to handle the highly nonlinear friction terms. The resulting shallow water overland flow model is first validated against analytical and experimental test cases and then applied to simulate a hypothetic rainfall event in the 42 km2 Haltwhistle Burn, UK.

Structural imaging of nanoscale phonon transport in ferroelectrics excited by metamaterial-enhanced terahertz fields

DOE PAGES

Zhu, Yi; Chen, Frank; Park, Joonkyu; ...

2017-11-16

Nanoscale phonon transport is a key process that governs thermal conduction in a wide range of materials and devices. Creating controlled phonon populations by resonant excitation at terahertz (THz) frequencies can drastically change the characteristics of nanoscale thermal transport and allow a direct real-space characterization of phonon mean-free paths. Using metamaterial-enhanced terahertz excitation, we tailored a phononic excitation by selectively populating low-frequency phonons within a nanoscale volume in a ferroelectric BaTiO 3 thin film. Real-space time-resolved x-ray diffraction microscopy following THz excitation reveals ballistic phonon transport over a distance of hundreds of nm, two orders of magnitude longer than themore » averaged phonon mean-free path in BaTiO 3. On longer length scales, diffusive phonon transport dominates the recovery of the transient strain response, largely due to heat conduction into the substrate. The measured real-space phonon transport can be directly compared with the phonon mean-free path as predicted by molecular dynamics modeling. In conclusion, this time-resolved real-space visualization of THz-matter interactions opens up opportunities to engineer and image nanoscale transient structural states with new functionalities.« less

Absence of residual structure in the intrinsically disordered regulatory protein CP12 in its reduced state

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

Launay, Hélène; Barré, Patrick; Puppo, Carine

2016-08-12

The redox switch protein CP12 is a key player of the regulation of the Benson–Calvin cycle. Its oxidation state is controlled by the formation/dissociation of two intramolecular disulphide bridges during the day/night cycle. CP12 was known to be globally intrinsically disordered on a large scale in its reduced state, while being partly ordered in the oxidised state. By combining Nuclear Magnetic Resonance and Small Angle X-ray Scattering experiments, we showed that, contrary to secondary structure or disorder predictions, reduced CP12 is fully disordered, with no transient or local residual structure likely to be precursor of the structures identified in themore » oxidised active state and/or in the bound state with GAPDH or PRK. These results highlight the diversity of the mechanisms of regulation of conditionally disordered redox switches, and question the stability of oxidised CP12 scaffold. - Highlights: • CP12 is predicted to form two helices in its N-terminal sequence. • Reduced CP12 is disordered as a random coil according to SAXS. • Limited or no transient structures are observed in reduced CP12 by NMR.« less

Kinetic Monte Carlo simulations for transient thermal fields: Computational methodology and application to the submicrosecond laser processes in implanted silicon.

PubMed

Fisicaro, G; Pelaz, L; Lopez, P; La Magna, A

2012-09-01

Pulsed laser irradiation of damaged solids promotes ultrafast nonequilibrium kinetics, on the submicrosecond scale, leading to microscopic modifications of the material state. Reliable theoretical predictions of this evolution can be achieved only by simulating particle interactions in the presence of large and transient gradients of the thermal field. We propose a kinetic Monte Carlo (KMC) method for the simulation of damaged systems in the extremely far-from-equilibrium conditions caused by the laser irradiation. The reference systems are nonideal crystals containing point defect excesses, an order of magnitude larger than the equilibrium density, due to a preirradiation ion implantation process. The thermal and, eventual, melting problem is solved within the phase-field methodology, and the numerical solutions for the space- and time-dependent thermal field were then dynamically coupled to the KMC code. The formalism, implementation, and related tests of our computational code are discussed in detail. As an application example we analyze the evolution of the defect system caused by P ion implantation in Si under nanosecond pulsed irradiation. The simulation results suggest a significant annihilation of the implantation damage which can be well controlled by the laser fluence.

A resolvable subfilter-scale model specific to large-eddy simulation of under-resolved turbulence

NASA Astrophysics Data System (ADS)

Zhou, Yong; Brasseur, James G.; Juneja, Anurag

2001-09-01

Large-eddy simulation (LES) of boundary-layer flows has serious deficiencies near the surface when a viscous sublayer either does not exist (rough walls) or is not practical to resolve (high Reynolds numbers). In previous work, we have shown that the near-surface errors arise from the poor performance of algebraic subfilter-scale (SFS) models at the first several grid levels, where integral scales are necessarily under-resolved and the turbulence is highly anisotropic. In under-resolved turbulence, eddy viscosity and similarity SFS models create a spurious feedback loop between predicted resolved-scale (RS) velocity and modeled SFS acceleration, and are unable to simultaneously capture SFS acceleration and RS-SFS energy flux. To break the spurious coupling in a dynamically meaningful manner, we introduce a new modeling strategy in which the grid-resolved subfilter velocity is estimated from a separate dynamical equation containing the essential inertial interactions between SFS and RS velocity. This resolved SFS (RSFS) velocity is then used as a surrogate for the complete SFS velocity in the SFS stress tensor. We test the RSFS model by comparing LES of highly under-resolved anisotropic buoyancy-generated homogeneous turbulence with a corresponding direct numerical simulation (DNS). The new model successfully suppresses the spurious feedback loop between RS velocity and SFS acceleration, and greatly improves model predictions of the anisotropic structure of SFS acceleration and resolved velocity fields. Unlike algebraic models, the RSFS model accurately captures SFS acceleration intensity and RS-SFS energy flux, even during the nonequilibrium transient, and properly partitions SFS acceleration between SFS stress divergence and SFS pressure force.

Time scales of tunneling decay of a localized state

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

Ban, Yue; Muga, J. G.; Sherman, E. Ya.

2010-12-15

Motivated by recent time-domain experiments on ultrafast atom ionization, we analyze the transients and time scales that characterize, aside from the relatively long lifetime, the decay of a localized state by tunneling. While the tunneling starts immediately, some time is required for the outgoing flux to develop. This short-term behavior depends strongly on the initial state. For the initial state, tightly localized so that the initial transients are dominated by over-the-barrier motion, the time scale for flux propagation through the barrier is close to the Buettiker-Landauer traversal time. Then a quasistationary, slow-decay process follows, which sets ideal conditions for observingmore » diffraction in time at longer times and distances. To define operationally a tunneling time at the barrier edge, we extrapolate backward the propagation of the wave packet that escaped from the potential. This extrapolated time is considerably longer than the time scale of the flux and density buildup at the barrier edge.« less

rfpipe: Radio interferometric transient search pipeline

NASA Astrophysics Data System (ADS)

Law, Casey J.

2017-10-01

rfpipe supports Python-based analysis of radio interferometric data (especially from the Very Large Array) and searches for fast radio transients. This extends on the rtpipe library (ascl:1706.002) with new approaches to parallelization, acceleration, and more portable data products. rfpipe can run in standalone mode or be in a cluster environment.

CHARACTERIZATION OF HEAVY-DUTY MOTOR VEHICLE EMISSIONS UNDER TRANSIENT DRIVING CONDITIONS

EPA Science Inventory

The objective of this program was to characterize heavy-duty diesel truck and bus emissions produced during transient driving cycles. In the initial phase of the program an improved road-load simulation method was developed for use in operating large trucks on a chassis dynamomet...

Simulating the biogeochemical and biogeophysical impacts of transient land cover change and wood harvest in the Community Climate System Model (CCSM4) from 1850 to 2100

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

Lawrence, Peter J.; Feddema, Johannes J.; Bonan, Gordon B.

To assess the climate impacts of historical and projected land cover change and land use in the Community Climate System Model (CCSM4) we have developed new time series of transient Community Land Model (CLM4) Plant Functional Type (PFT) parameters and wood harvest parameters. The new parameters capture the dynamics of the Coupled Model Inter-comparison Project phase 5 (CMIP5) land cover change and wood harvest trajectories for the historical period from 1850 to 2005, and for the four Representative Concentration Pathways (RCP) periods from 2006 to 2100. Analysis of the biogeochemical impacts of land cover change in CCSM4 with the parametersmore » found the model produced an historical cumulative land use flux of 148.4 PgC from 1850 to 2005, which was in good agreement with other global estimates of around 156 PgC for the same period. The biogeophysical impacts of only applying the transient land cover change parameters in CCSM4 were cooling of the near surface atmospheric over land by -0.1OC, through increased surface albedo and reduced shortwave radiation absorption. When combined with other transient climate forcings, the higher albedo from land cover change was overwhelmed at global scales by decreases in snow albedo from black carbon deposition and from high latitude warming. At regional scales however the land cover change forcing persisted resulting in reduced warming, with the biggest impacts in eastern North America. The future CCSM4 RCP simulations showed that the CLM4 transient PFT and wood harvest parameters could be used to represent a wide range of human land cover change and land use scenarios. Furthermore, these simulations ranged from the RCP 4.5 reforestation scenario that was able to draw down 82.6 PgC from the atmosphere, to the RCP 8.5 wide scale deforestation scenario that released 171.6 PgC to the atmosphere.« less

Cortical cholinergic signaling controls the detection of cues

PubMed Central

Gritton, Howard J.; Howe, William M.; Mallory, Caitlin S.; Hetrick, Vaughn L.; Berke, Joshua D.; Sarter, Martin

2016-01-01

The cortical cholinergic input system has been described as a neuromodulator system that influences broadly defined behavioral and brain states. The discovery of phasic, trial-based increases in extracellular choline (transients), resulting from the hydrolysis of newly released acetylcholine (ACh), in the cortex of animals reporting the presence of cues suggests that ACh may have a more specialized role in cognitive processes. Here we expressed channelrhodopsin or halorhodopsin in basal forebrain cholinergic neurons of mice with optic fibers directed into this region and prefrontal cortex. Cholinergic transients, evoked in accordance with photostimulation parameters determined in vivo, were generated in mice performing a task necessitating the reporting of cue and noncue events. Generating cholinergic transients in conjunction with cues enhanced cue detection rates. Moreover, generating transients in noncued trials, where cholinergic transients normally are not observed, increased the number of invalid claims for cues. Enhancing hits and generating false alarms both scaled with stimulation intensity. Suppression of endogenous cholinergic activity during cued trials reduced hit rates. Cholinergic transients may be essential for synchronizing cortical neuronal output driven by salient cues and executing cue-guided responses. PMID:26787867

Transient heterogeneity in an aquifer undergoing bioremediation of hydrocarbons.

PubMed

Schillig, P C; Devlin, J F; Roberts, J A; Tsoflias, G P; McGlashan, M A

2011-01-01

Localized, transient heterogeneity was studied in a sand aquifer undergoing benzene, toluene, ethylbenzene, and xylene bioremediation using a novel array of multilevel, in situ point velocity probes (PVPs). The experiment was conducted within a sheet-pile alleyway to maintain a constant average flow direction through time. The PVPs measured changes in groundwater velocity direction and magnitude at the centimeter scale, making them ideal to monitor small-scale changes in hydraulic conductivity (K). Velocities were shown to vary nonuniformly by up to a factor of 3 when a source of oxygen was established down-gradient of the petroleum spill. In spite of these local variations, the average groundwater velocity within the 7 m × 20 m sheet-piled test area only varied within ± 25%. The nonuniform nature of the velocity variations across the gate indicated that the changes were not due solely to seasonal hydraulic gradient fluctuations. At the conclusion of the experiment, microbial biomass levels in the aquifer sediments was approximately 1 order of magnitude higher in the oxygen-amended portion of the aquifer than at the edge of the plume or in locations up-gradient of the source. These data suggest that the transient velocities resulted, at least in part, from enhanced biological activity that caused transient heterogeneities in the porous medium.

High energy from space

NASA Technical Reports Server (NTRS)

Margon, Bruce; Canizares, Claude; Catura, Richard C.; Clark, George W.; Fichtel, Carl E.; Friedman, Herbert; Giacconi, Riccardo; Grindlay, Jonathan E.; Helfand, David J.; Holt, Stephen S.

1991-01-01

The following subject areas are covered: (1) important scientific problems for high energy astrophysics (stellar activity, the interstellar medium in galaxies, supernovae and endpoints of stellar evolution, nucleosynthesis, relativistic plasmas and matter under extreme conditions, nature of gamma-bursts, identification of black holes, active nuclei, accretion physics, large-scale structures, intracluster medium, nature of dark matter, and the X- and gamma-ray background); (2) the existing experimental programs (Advanced X-Ray Astrophysics Facility (AXAF), Gamma Ray Observatory (GRO), X-Ray Timing Explorer (XTE), High Energy Transient Experiment (HETE), U.S. participation in foreign missions, and attached Shuttle and Space Station Freedom payloads); (3) major missions for the 1990's; (4) a new program of moderate missions; (5) new opportunities for small missions; (6) technology development issues; and (7) policy issues.

Interactive flare sites within an active region complex

NASA Technical Reports Server (NTRS)

Poletto, G.; Gary, G. A.; Machado, M. E.

1993-01-01

We examine here a set of images of an active region complex, acquired on June 24-25, 1980, by the Hard X-ray Imaging Spectrometer on SMM, with the purpose of establishing whether there was any interplay between the frequent activity observed at different sites in the activity center and, in such a case, how the interaction was established. By analyzing both quiet and active orbits we show that, as a rule, activity originating in one region triggers the other region's activity. However, we find little unambiguous evidence for the presence of large-scale interconnecting loops. A comparison of X-ray images with magnetic field observations suggested that we interpret the active region behavior in terms of the interaction between different loop systems, in a scenario quite analogous to the interacting bipole representation of individual flares. We conclude that active region interplay provides an easily observable case to study the time-dependent topology and the mechanisms for the spreading of activity in transient events over all energy scales.

Regional Differences in Tropical Lightning Distributions.

NASA Astrophysics Data System (ADS)

Boccippio, Dennis J.; Goodman, Steven J.; Heckman, Stan

2000-12-01

Observations from the National Aeronautics and Space Administration Optical Transient Detector (OTD) and Tropical Rainfall Measuring Mission (TRMM)-based Lightning Imaging Sensor (LIS) are analyzed for variability between land and ocean, various geographic regions, and different (objectively defined) convective `regimes.' The bulk of the order-of-magnitude differences between land and ocean regional flash rates are accounted for by differences in storm spacing (density) and/or frequency of occurrence, rather than differences in storm instantaneous flash rates, which only vary by a factor of 2 on average. Regional variability in cell density and cell flash rates closely tracks differences in 85-GHz microwave brightness temperatures. Monotonic relationships are found with the gross moist stability of the tropical atmosphere, a large-scale `adjusted state' parameter. This result strongly suggests that it will be possible, using TRMM observations, to objectively test numerical or theoretical predictions of how mesoscale convective organization interacts with the larger-scale environment. Further parameters are suggested for a complete objective definition of tropical convective regimes.

Waves associated to COMPLEX EVENTS observed by STEREO

NASA Astrophysics Data System (ADS)

Siu Tapia, A. L.; Blanco-Cano, X.; Kajdic, P.; Aguilar-Rodriguez, E.; Russell, C. T.; Jian, L. K.; Luhmann, J. G.

2012-12-01

Complex Events are formed by two or more large-scale solar wind structures which interact in space. Typical cases are interactions of: (i) a Magnetic Cloud/Interplanetary Coronal Mass Ejection (MC/ICME) with another MC/ICME transient; and (ii) an ICME followed by a Stream Interaction Region (SIR). Complex Events are of importance for space weather studies and studying them can enhance our understanding of collisionless plasma physics. Some of these structures can produce or enhance southward magnetic fields, a key factor in geomagnetic storm generation. Using data from the STEREO mission during the years 2006-2011, we found 17 Complex Events preceded by a shock wave. We use magnetic field and plasma data to study the micro-scale structure of the shocks, and the waves associated to these shocks and within Complex Events structures. To determine wave characteristics we perform Power Spectra and Minimum Variance Analysis. We also use PLASTIC WAP protons data to study foreshock extensions and the relationship between Complex Regions and particle acceleration to suprathermal energies.

Quantum matter bounce with a dark energy expanding phase

NASA Astrophysics Data System (ADS)

Colin, Samuel; Pinto-Neto, Nelson

2017-09-01

Analyzing quantum cosmological scenarios containing one scalar field with exponential potential, we have obtained a universe model which realizes a classical dust contraction from very large scales, the initial repeller of the model, and moves to a stiff matter contraction near the singularity, which is avoided due to a quantum bounce. The universe is then launched in a stiff matter expanding phase, which then moves to a dark energy era, finally returning to the dust expanding phase, the final attractor of the model. Hence, one has obtained a nonsingular cosmological model where a single scalar field can describe both the matter contracting phase of a bouncing model, necessary to give an almost scale invariant spectrum of scalar cosmological perturbations, and a transient expanding dark energy phase. As the universe is necessarily dust dominated in the far past, usual adiabatic vacuum initial conditions can be easily imposed in this era, avoiding the usual issues appearing when dark energy is considered in bouncing models.

Regional Climate Sensitivity- and Historical-Based Projections to 2100

NASA Astrophysics Data System (ADS)

Hébert, Raphaël.; Lovejoy, Shaun

2018-05-01

Reliable climate projections at the regional scale are needed in order to evaluate climate change impacts and inform policy. We develop an alternative method for projections based on the transient climate sensitivity (TCS), which relies on a linear relationship between the forced temperature response and the strongly increasing anthropogenic forcing. The TCS is evaluated at the regional scale (5° by 5°), and projections are made accordingly to 2100 using the high and low Representative Concentration Pathways emission scenarios. We find that there are large spatial discrepancies between the regional TCS from 5 historical data sets and 32 global climate model (GCM) historical runs and furthermore that the global mean GCM TCS is about 15% too high. Given that the GCM Representative Concentration Pathway scenario runs are mostly linear with respect to their (inadequate) TCS, we conclude that historical methods of regional projection are better suited given that they are directly calibrated on the real world (historical) climate.

A framework for studying transient dynamics of population projection matrix models.

PubMed

Stott, Iain; Townley, Stuart; Hodgson, David James

2011-09-01

Empirical models are central to effective conservation and population management, and should be predictive of real-world dynamics. Available modelling methods are diverse, but analysis usually focuses on long-term dynamics that are unable to describe the complicated short-term time series that can arise even from simple models following ecological disturbances or perturbations. Recent interest in such transient dynamics has led to diverse methodologies for their quantification in density-independent, time-invariant population projection matrix (PPM) models, but the fragmented nature of this literature has stifled the widespread analysis of transients. We review the literature on transient analyses of linear PPM models and synthesise a coherent framework. We promote the use of standardised indices, and categorise indices according to their focus on either convergence times or transient population density, and on either transient bounds or case-specific transient dynamics. We use a large database of empirical PPM models to explore relationships between indices of transient dynamics. This analysis promotes the use of population inertia as a simple, versatile and informative predictor of transient population density, but criticises the utility of established indices of convergence times. Our findings should guide further development of analyses of transient population dynamics using PPMs or other empirical modelling techniques. © 2011 Blackwell Publishing Ltd/CNRS.

Multi-scale temporal and spatial variation in genotypic composition of Cladophora-borne Escherichia coli populations in Lake Michigan.

PubMed

Badgley, Brian D; Ferguson, John; Vanden Heuvel, Amy; Kleinheinz, Gregory T; McDermott, Colleen M; Sandrin, Todd R; Kinzelman, Julie; Junion, Emily A; Byappanahalli, Muruleedhara N; Whitman, Richard L; Sadowsky, Michael J

2011-01-01

High concentrations of Escherichia coli in mats of Cladophora in the Great Lakes have raised concern over the continued use of this bacterium as an indicator of microbial water quality. Determining the impacts of these environmentally abundant E. coli, however, necessitates a better understanding of their ecology. In this study, the population structure of 4285 Cladophora-borne E. coli isolates, obtained over multiple three day periods from Lake Michigan Cladophora mats in 2007-2009, was examined by using DNA fingerprint analyses. In contrast to previous studies that have been done using isolates from attached Cladophora obtained over large time scales and distances, the extensive sampling done here on free-floating mats over successive days at multiple sites provided a large dataset that allowed for a detailed examination of changes in population structure over a wide range of spatial and temporal scales. While Cladophora-borne E. coli populations were highly diverse and consisted of many unique isolates, multiple clonal groups were also present and accounted for approximately 33% of all isolates examined. Patterns in population structure were also evident. At the broadest scales, E. coli populations showed some temporal clustering when examined by year, but did not show good spatial distinction among sites. E. coli population structure also showed significant patterns at much finer temporal scales. Populations were distinct on an individual mat basis at a given site, and on individual days within a single mat. Results of these studies indicate that Cladophora-borne E. coli populations consist of a mixture of stable, and possibly naturalized, strains that persist during the life of the mat, and more unique, transient strains that can change over rapid time scales. It is clear that further study of microbial processes at fine spatial and temporal scales is needed, and that caution must be taken when interpolating short term microbial dynamics from results obtained from weekly or monthly samples. Copyright © 2010 Elsevier Ltd. All rights reserved.

Multi-scale temporal and spatial variation in genotypic composition of Cladophora-borne Escherichia coli populations in Lake Michigan

USGS Publications Warehouse

Badgley, B.D.; Ferguson, J.; Heuvel, A.V.; Kleinheinz, G.T.; McDermott, C.M.; Sandrin, T.R.; Kinzelman, J.; Junion, E.A.; Byappanahalli, M.N.; Whitman, R.L.; Sadowsky, M.J.

2011-01-01

High concentrations of Escherichia coli in mats of Cladophora in the Great Lakes have raised concern over the continued use of this bacterium as an indicator of microbial water quality. Determining the impacts of these environmentally abundant E. coli, however, necessitates a better understanding of their ecology. In this study, the population structure of 4285 Cladophora-borne E. coli isolates, obtained over multiple three day periods from Lake Michigan Cladophora mats in 2007-2009, was examined by using DNA fingerprint analyses. In contrast to previous studies that have been done using isolates from attached Cladophora obtained over large time scales and distances, the extensive sampling done here on free-floating mats over successive days at multiple sites provided a large dataset that allowed for a detailed examination of changes in population structure over a wide range of spatial and temporal scales. While Cladophora-borne E. coli populations were highly diverse and consisted of many unique isolates, multiple clonal groups were also present and accounted for approximately 33% of all isolates examined. Patterns in population structure were also evident. At the broadest scales, E. coli populations showed some temporal clustering when examined by year, but did not show good spatial distinction among sites. E. coli population structure also showed significant patterns at much finer temporal scales. Populations were distinct on an individual mat basis at a given site, and on individual days within a single mat. Results of these studies indicate that Cladophora-borne E. coli populations consist of a mixture of stable, and possibly naturalized, strains that persist during the life of the mat, and more unique, transient strains that can change over rapid time scales. It is clear that further study of microbial processes at fine spatial and temporal scales is needed, and that caution must be taken when interpolating short term microbial dynamics from results obtained from weekly or monthly samples.

Volcanic Eruptions and Climate

NASA Technical Reports Server (NTRS)

LeGrande, Allegra N.; Anchukaitis, Kevin J.

2015-01-01

Volcanic eruptions represent some of the most climatically important and societally disruptive short-term events in human history. Large eruptions inject ash, dust, sulfurous gases (e.g. SO2, H2S), halogens (e.g. Hcl and Hbr), and water vapor into the Earth's atmosphere. Sulfurous emissions principally interact with the climate by converting into sulfate aerosols that reduce incoming solar radiation, warming the stratosphere and altering ozone creation, reducing global mean surface temperature, and suppressing the hydrological cycle. In this issue, we focus on the history, processes, and consequences of these large eruptions that inject enough material into the stratosphere to significantly affect the climate system. In terms of the changes wrought on the energy balance of the Earth System, these transient events can temporarily have a radiative forcing magnitude larger than the range of solar, greenhouse gas, and land use variability over the last millennium. In simulations as well as modern and paleoclimate observations, volcanic eruptions cause large inter-annual to decadal-scale changes in climate. Active debates persist concerning their role in longer-term (multi-decadal to centennial) modification of the Earth System, however.

An accidental geophysical discovery of an Iron Age archaeological site on the western shore of Lake Baikal

NASA Astrophysics Data System (ADS)

Kozhevnikov, Nikolai O.; Kharinsky, Arthur V.; Kozhevnikov, Oleg K.

2001-06-01

Slowly decaying transients were measured during a TEM survey over crystalline metamorphic rocks in the vicinity of the village of Chernorud, on the western shore of Lake Baikal. Once converted to apparent resistivities, these transients resulted in values of about 2-5 Ω m. Because neither in-field nor laboratory DC resistivity measurements indicate conductive rocks, the TEM results are confusing. It is hypothesized that the anomalous transients were caused by the relaxation of the magnetization of extremely fine ferri- and/or ferromagnetic particles concentrated in the near-surface layer. In 1997, in the soil thrown out of a gopher burrow, slags and charcoal fragments were found which suggested ancient metallurgical activity. Despite the slags being electrically poorly conductive, once placed into a small coil, they produced slowly decaying transients caused by magnetic viscosity effects. On the basis of their chemical and mineral composition, the Chernorud site slags proved to be identical to those which are known to have been formed during the production of iron in ancient bloomery furnaces. An excavation carried out at the site of the gopher burrow resulted in the discovery of a large bloomery furnace, much slag, charcoal, and baked clay fragments. In 1999, reconnaissance magnetic field and galvanic resistivity profiling measurements were conducted, focused on the site's archaeological potential. Data were taken over a 96×100 m area at 4 m intervals along parallel profiles spaced at 4 m. The magnetic field contour and surface maps exhibited an isometrically shaped positive anomaly with an amplitude of 40-50 nT, that was 30-40 m in diameter. The bloomery and other archaeometallurgical structures fall within the central part of the magnetic anomaly. The galvanic profiling has revealed a resistivity high (1000-1500 Ω m against 300-500 Ω m) which might be attributed to ancient human activity. Radiocarbon dating of three charcoal fragments sampled during the excavation from different depth intervals has given uncalibrated ages of 1915±35, 2050±35 and 2180±30 years BP. These results make it apparent that the Iron Age on the western shore of Lake Baikal started about 700-900 years earlier than is generally accepted. Occurrence of slags over an area of no less than 15 ha suggests that iron production in the Barun-Khal valley was performed on a large scale.

Floquet-Magnus theory and generic transient dynamics in periodically driven many-body quantum systems

NASA Astrophysics Data System (ADS)

Kuwahara, Tomotaka; Mori, Takashi; Saito, Keiji

2016-04-01

This work explores a fundamental dynamical structure for a wide range of many-body quantum systems under periodic driving. Generically, in the thermodynamic limit, such systems are known to heat up to infinite temperature states in the long-time limit irrespective of dynamical details, which kills all the specific properties of the system. In the present study, instead of considering infinitely long-time scale, we aim to provide a general framework to understand the long but finite time behavior, namely the transient dynamics. In our analysis, we focus on the Floquet-Magnus (FM) expansion that gives a formal expression of the effective Hamiltonian on the system. Although in general the full series expansion is not convergent in the thermodynamics limit, we give a clear relationship between the FM expansion and the transient dynamics. More precisely, we rigorously show that a truncated version of the FM expansion accurately describes the exact dynamics for a certain time-scale. Our theory reveals an experimental time-scale for which non-trivial dynamical phenomena can be reliably observed. We discuss several dynamical phenomena, such as the effect of small integrability breaking, efficient numerical simulation of periodically driven systems, dynamical localization and thermalization. Especially on thermalization, we discuss a generic scenario on the prethermalization phenomenon in periodically driven systems.

Comparing the results of an analytical model of the no-vent fill process with no-vent fill test results for a 4.96 cubic meters (175 cubic feet) tank

NASA Technical Reports Server (NTRS)

Taylor, William J.; Chato, David J.

1993-01-01

The NASA Lewis Research Center (NASA/LeRC) have been investigating a no-vent fill method for refilling cryogenic storage tanks in low gravity. Analytical modeling based on analyzing the heat transfer of a droplet has successfully represented the process in 0.034 m and 0.142 cubic m commercial dewars using liquid nitrogen and hydrogen. Recently a large tank (4.96 cubic m) was tested with hydrogen. This lightweight tank is representative of spacecraft construction. This paper presents efforts to model the large tank test data. The droplet heat transfer model is found to over predict the tank pressure level when compared to the large tank data. A new model based on equilibrium thermodynamics has been formulated. This new model is compared to the published large scale tank's test results as well as some additional test runs with the same equipment. The results are shown to match the test results within the measurement uncertainty of the test data except for the initial transient wall cooldown where it is conservative (i.e., overpredicts the initial pressure spike found in this time frame).

Transient photoresponse in amorphous In-Ga-Zn-O thin films under stretched exponential analysis

NASA Astrophysics Data System (ADS)

Luo, Jiajun; Adler, Alexander U.; Mason, Thomas O.; Bruce Buchholz, D.; Chang, R. P. H.; Grayson, M.

2013-04-01

We investigated transient photoresponse and Hall effect in amorphous In-Ga-Zn-O thin films and observed a stretched exponential response which allows characterization of the activation energy spectrum with only three fit parameters. Measurements of as-grown films and 350 K annealed films were conducted at room temperature by recording conductivity, carrier density, and mobility over day-long time scales, both under illumination and in the dark. Hall measurements verify approximately constant mobility, even as the photoinduced carrier density changes by orders of magnitude. The transient photoconductivity data fit well to a stretched exponential during both illumination and dark relaxation, but with slower response in the dark. The inverse Laplace transforms of these stretched exponentials yield the density of activation energies responsible for transient photoconductivity. An empirical equation is introduced, which determines the linewidth of the activation energy band from the stretched exponential parameter β. Dry annealing at 350 K is observed to slow the transient photoresponse.

A Large Signal Model for CMUT Arrays with Arbitrary Membrane Geometries Operating in Non-Collapsed Mode

PubMed Central

Satir, Sarp; Zahorian, Jaime; Degertekin, F. Levent

2014-01-01

A large signal, transient model has been developed to predict the output characteristics of a CMUT array operated in the non-collapse mode. The model is based on separation of the nonlinear electrostatic voltage-to-force relation and the linear acoustic array response. For linear acoustic radiation and crosstalk effects, the boundary element method is used. The stiffness matrix in the vibroacoustics calculations is obtained using static finite element analysis of a single membrane which can have arbitrary geometry and boundary conditions. A lumped modeling approach is used to reduce the order of the system for modeling the transient nonlinear electrostatic actuation. To accurately capture the dynamics of the non-uniform electrostatic force distribution over the CMUT electrode during large deflections, the membrane electrode is divided into patches shaped to match higher order membrane modes, each introducing a variable to the system model. This reduced order nonlinear lumped model is solved in the time domain using Simulink. The model has two linear blocks to calculate the displacement profile of the electrode patches and the output pressure for a given force distribution over the array, respectively. The force to array displacement block uses the linear acoustic model, and the Rayleigh integral is evaluated to calculate the pressure at any field point. Using the model, the transient transmitted pressure can be simulated for different large signal drive signal configurations. The acoustic model is verified by comparison to harmonic FEA in vacuum and fluid for high and low aspect ratio membranes as well as mass-loaded membranes. The overall Simulink model is verified by comparison to transient 3D FEA and experimental results for different large drive signals; and an example for a phased array simulation is given. PMID:24158297

Performance evaluation capabilities for the design of physical systems

NASA Technical Reports Server (NTRS)

Pilkey, W. D.; Wang, B. P.

1972-01-01

The results are presented of a study aimed at developing and formulating a capability for the limiting performance of large steady state systems. The accomplishments reported include: (1) development of a theory of limiting performance of large systems subject to steady state inputs; (2) application and modification of PERFORM, the computational capability for the limiting performance of systems with transient inputs; and (3) demonstration that use of an inherently smooth control force for a limiting performance calculation improves the system identification phase of the design process for physical systems subjected to transient loading.

Neural control and transient analysis of the LCL-type resonant converter

NASA Astrophysics Data System (ADS)

Zouggar, S.; Nait Charif, H.; Azizi, M.

2000-07-01

This paper proposes a generalised inverse learning structure to control the LCL converter. A feedforward neural network is trained to act as an inverse model of the LCL converter then both are cascaded such that the composed system results in an identity mapping between desired response and the LCL output voltage. Using the large signal model, we analyse the transient output response of the controlled LCL converter in the case of large variation of the load. The simulation results show the efficiency of using neural networks to regulate the LCL converter.

Transient regional climate change: analysis of the summer climate response in a high-resolution, century-scale, ensemble experiment over the continental United States

PubMed Central

Diffenbaugh, Noah S.; Ashfaq, Moetasim; Scherer, Martin

2013-01-01

Integrating the potential for climate change impacts into policy and planning decisions requires quantification of the emergence of sub-regional climate changes that could occur in response to transient changes in global radiative forcing. Here we report results from a high-resolution, century-scale, ensemble simulation of climate in the United States, forced by atmospheric constituent concentrations from the Special Report on Emissions Scenarios (SRES) A1B scenario. We find that 21st century summer warming permanently emerges beyond the baseline decadal-scale variability prior to 2020 over most areas of the continental U.S. Permanent emergence beyond the baseline annual-scale variability shows much greater spatial heterogeneity, with emergence occurring prior to 2030 over areas of the southwestern U.S., but not prior to the end of the 21st century over much of the southcentral and southeastern U.S. The pattern of emergence of robust summer warming contrasts with the pattern of summer warming magnitude, which is greatest over the central U.S. and smallest over the western U.S. In addition to stronger warming, the central U.S. also exhibits stronger coupling of changes in surface air temperature, precipitation, and moisture and energy fluxes, along with changes in atmospheric circulation towards increased anticylonic anomalies in the mid-troposphere and a poleward shift in the mid-latitude jet aloft. However, as a fraction of the baseline variability, the transient warming over the central U.S. is smaller than the warming over the southwestern or northeastern U.S., delaying the emergence of the warming signal over the central U.S. Our comparisons with observations and the Coupled Model Intercomparison Project Phase 3 (CMIP3) ensemble of global climate model experiments suggest that near-term global warming is likely to cause robust sub-regional-scale warming over areas that exhibit relatively little baseline variability. In contrast, where there is greater variability in the baseline climate dynamics, there can be greater variability in the response to elevated greenhouse forcing, decreasing the robustness of the transient warming signal. PMID:24307747

On the origin of the March 5, 1979 gamma ray transient: A vibrating neutron star in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Ramaty, R.; Bonazzola, S.; Cline, T. L.; Kazanas, D.; Meszaros, P.; Lingenfelter, R. E.

1980-01-01

It is proposed that a vibrating neutron star in the Large Magellanic Cloud is the source of the March 5 transient. Neutron star vibrations transport energy rapidly to the surface, heat the atmosphere by wave dissipation, and decay by gravitational radiation reaction. The electromagnetic emission arises from e(+)-e(-) pairs which cool and annihilate in the strong magnetic field of the neutron star. The field also confines the pairs, and this allows the production of the redshifted annihilation feature observed in the data. The redshift implies a gravitational radiation damping time which agrees with the 0.15 second duration of the impulsive phase of the event. Thus, the March 5 transient may be both the first detection of a vibrating neutron star and indirect evidence for gravitational radiation.

Glutamate 338 is an electrostatic facilitator of C–Co bond breakage in a dynamic/electrostatic model of catalysis by ornithine aminomutase

PubMed Central

Menon, Binuraj R K; Menon, Navya; Fisher, Karl; Rigby, Stephen E J; Leys, David; Scrutton, Nigel S

2015-01-01

How cobalamin-dependent enzymes promote C–Co homolysis to initiate radical catalysis has been debated extensively. For the pyridoxal 5′-phosphate and cobalamin-dependent enzymes lysine 5,6-aminomutase and ornithine 4,5-aminomutase (OAM), large-scale re-orientation of the cobalamin-binding domain linked to C–Co bond breakage has been proposed. In these models, substrate binding triggers dynamic sampling of the B12-binding Rossmann domain to achieve a catalytically competent ‘closed’ conformational state. In ‘closed’ conformations of OAM, Glu338 is thought to facilitate C–Co bond breakage by close association with the cobalamin adenosyl group. We investigated this using stopped-flow continuous-wave photolysis, viscosity dependence kinetic measurements, and electron paramagnetic resonance spectroscopy of a series of Glu338 variants. We found that substrate-induced C–Co bond homolysis is compromised in Glu388 variant forms of OAM, although photolysis of the C–Co bond is not affected by the identity of residue 338. Electrostatic interactions of Glu338 with the 5′-deoxyadenosyl group of B12 potentiate C–Co bond homolysis in ‘closed’ conformations only; these conformations are unlocked by substrate binding. Our studies extend earlier models that identified a requirement for large-scale motion of the cobalamin domain. Our findings indicate that large-scale motion is required to pre-organize the active site by enabling transient formation of ‘closed’ conformations of OAM. In ‘closed’ conformations, Glu338 interacts with the 5′-deoxyadenosyl group of cobalamin. This interaction is required to potentiate C–Co homolysis, and is a crucial component of the approximately 1012 rate enhancement achieved by cobalamin-dependent enzymes for C–Co bond homolysis. PMID:25627283

Transient hypothyroidism after withdrawal of thyroxin therapy

PubMed Central

Distiller, L. A.; Joffe, B. I.

1975-01-01

Continued administration of large doses of thyroid may not produce hyperthyroidism in euthyroid individuals. Cessation of prolonged high-dosage thyroid replacement can cause transient clinical and biochemical hypothyroidism owing to pituitary suppression. A case is recorded in which both these phenomena are well demonstrated. This case highlights these basic endocrinological principles. PMID:1197170

The intensity recovery of Forbush-type decreases as a function of heliocentric distance and its relationship to the 11-year variation

NASA Astrophysics Data System (ADS)

Lockwood, J. A.; Webber, W. R.; Jokipii, J. R.

1985-08-01

Recent data indicating that the solar modulation effects are propagated outward in the heliospheric cavity suggest that the 11-year cosmic ray modulation can best be described by a dynamic time dependent model. In this context an understanding of the recovery characteristics of large transient Forbush type decreases is important. This includes the typical recovery time at a fixed energy at 1 AU as well as at large heliocentric radial distances, the energy dependence of the recovery time at 1 Au, and the dependence of the time for the intensity to decrease to the minimum in the transient decreases as a function of distance. These transient decreases are characterized by their asymmetrical decrease and recovery times, generally 1 to 2 days and 3 to 10 days respectively at approx. 1 AU. Near earth these are referred to as Forbush decreases, associated witha shock or blast wave passage. At R equal to or greater than + or - 10 AU, these transient decreases may represent the combined effects of several shock waves that have merged together.

In-Flight Validation of a Pilot Rating Scale for Evaluating Failure Transients in Electronic Flight Control Systems

NASA Technical Reports Server (NTRS)

Kalinowski, Kevin F.; Tucker, George E.; Moralez, Ernesto, III

2006-01-01

Engineering development and qualification of a Research Flight Control System (RFCS) for the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) JUH-60A has motivated the development of a pilot rating scale for evaluating failure transients in fly-by-wire flight control systems. The RASCAL RFCS includes a highly-reliable, dual-channel Servo Control Unit (SCU) to command and monitor the performance of the fly-by-wire actuators and protect against the effects of erroneous commands from the flexible, but single-thread Flight Control Computer. During the design phase of the RFCS, two piloted simulations were conducted on the Ames Research Center Vertical Motion Simulator (VMS) to help define the required performance characteristics of the safety monitoring algorithms in the SCU. Simulated failures, including hard-over and slow-over commands, were injected into the command path, and the aircraft response and safety monitor performance were evaluated. A subjective Failure/Recovery Rating (F/RR) scale was developed as a means of quantifying the effects of the injected failures on the aircraft state and the degree of pilot effort required to safely recover the aircraft. A brief evaluation of the rating scale was also conducted on the Army/NASA CH-47B variable stability helicopter to confirm that the rating scale was likely to be equally applicable to in-flight evaluations. Following the initial research flight qualification of the RFCS in 2002, a flight test effort was begun to validate the performance of the safety monitors and to validate their design for the safe conduct of research flight testing. Simulated failures were injected into the SCU, and the F/RR scale was applied to assess the results. The results validate the performance of the monitors, and indicate that the Failure/Recovery Rating scale is a very useful tool for evaluating failure transients in fly-by-wire flight control systems.

Detecting TLEs using a massive all-sky camera network

NASA Astrophysics Data System (ADS)

Garnung, M. B.; Celestin, S. J.

2017-12-01

Transient Luminous Events (TLEs) are large-scale optical events occurring in the upper-atmosphere from the top of thunderclouds up to the ionosphere. TLEs may have important effects in local, regional, and global scales, and many features of TLEs are not fully understood yet [e.g, Pasko, JGR, 115, A00E35, 2010]. Moreover, meteor events have been suggested to play a role in sprite initiation by producing ionospheric irregularities [e.g, Qin et al., Nat. Commun., 5, 3740, 2014]. The French Fireball Recovery and InterPlanetary Observation Network (FRIPON, https://www.fripon.org/?lang=en), is a national all-sky 30 fps camera network designed to continuously detect meteor events. We seek to make use of this network to observe TLEs over unprecedented space and time scales ( 1000×1000 km with continuous acquisition). To do so, we had to significantly modify FRIPON's triggering software Freeture (https://github.com/fripon/freeture) while leaving the meteor detection capability uncompromised. FRIPON has a great potential in the study of TLEs. Not only could it produce new results about spatial and time distributions of TLEs over a very large area, it could also be used to validate and complement observations from future space missions such as ASIM (ESA) and TARANIS (CNES). In this work, we present an original image processing algorithm that can detect sprites using all-sky cameras while strongly limiting the frequency of false positives and our ongoing work on sprite triangulation using the FRIPON network.

The Avoidance of Saturation Limits in Magnetic Bearing Systems During Transient Excitation

NASA Technical Reports Server (NTRS)

Rutland, Neil K.; Keogh, Patrick S.; Burrows, Clifford R.

1996-01-01

When a transient event, such as mass loss, occurs in a rotor/magnetic bearing system, optimal vibration control forces may exceed bearing capabilities. This will be inevitable when the mass loss is sufficiently large and a conditionally unstable dynamic system could result if the bearing characteristic become non-linear. This paper provides a controller design procedure to suppress, where possible, bearing force demands below saturation levels while maintaining vibration control. It utilizes H(sub infinity) optimization with appropriate input and output weightings. Simulation of transient behavior following mass loss from a flexible rotor is used to demonstrate the avoidance of conditional instability. A compromise between transient control force and vibration levels was achieved.

Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space.

PubMed

Masui, Kiyoshi Wesley; Sigurdson, Kris

2015-09-18

We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources. Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances. The rate of fast radio bursts has been estimated to be several thousand over the whole sky per day and, if cosmological, the sources of these events should trace the large-scale structure of the Universe. We calculate the dispersion-space power spectra for a simple model where electrons and FRBs are biased tracers of the large-scale structure of the Universe, and we show that the clustering signal could be measured using as few as 10 000 events. Such a survey is in line with what may be achieved with upcoming wide-field radio telescopes.

Scramjet test flow reconstruction for a large-scale expansion tube, Part 1: quasi-one-dimensional modelling

NASA Astrophysics Data System (ADS)

Gildfind, D. E.; Jacobs, P. A.; Morgan, R. G.; Chan, W. Y. K.; Gollan, R. J.

2018-07-01

Large-scale free-piston driven expansion tubes have uniquely high total pressure capabilities which make them an important resource for development of access-to-space scramjet engine technology. However, many aspects of their operation are complex, and their test flows are fundamentally unsteady and difficult to measure. While computational fluid dynamics methods provide an important tool for quantifying these flows, these calculations become very expensive with increasing facility size and therefore have to be carefully constructed to ensure sufficient accuracy is achieved within feasible computational times. This study examines modelling strategies for a Mach 10 scramjet test condition developed for The University of Queensland's X3 facility. The present paper outlines the challenges associated with test flow reconstruction, describes the experimental set-up for the X3 experiments, and then details the development of an experimentally tuned quasi-one-dimensional CFD model of the full facility. The 1-D model, which accurately captures longitudinal wave processes, is used to calculate the transient flow history in the shock tube. This becomes the inflow to a higher-fidelity 2-D axisymmetric simulation of the downstream facility, detailed in the Part 2 companion paper, leading to a validated, fully defined nozzle exit test flow.

Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space

NASA Astrophysics Data System (ADS)

Masui, Kiyoshi Wesley; Sigurdson, Kris

2015-09-01

We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources. Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances. The rate of fast radio bursts has been estimated to be several thousand over the whole sky per day and, if cosmological, the sources of these events should trace the large-scale structure of the Universe. We calculate the dispersion-space power spectra for a simple model where electrons and FRBs are biased tracers of the large-scale structure of the Universe, and we show that the clustering signal could be measured using as few as 10 000 events. Such a survey is in line with what may be achieved with upcoming wide-field radio telescopes.

Testing of the NASA Hypersonics Project Combined Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE LlMX)

NASA Technical Reports Server (NTRS)

Saunders, J. D.; Stueber, T. J.; Thomas, S. R.; Suder, K. L.; Weir, L. J.; Sanders, B. W.

2012-01-01

Status on an effort to develop Turbine Based Combined Cycle (TBCC) propulsion is described. This propulsion technology can enable reliable and reusable space launch systems. TBCC propulsion offers improved performance and safety over rocket propulsion. The potential to realize aircraft-like operations and reduced maintenance are additional benefits. Among most the critical TBCC enabling technologies are: 1) mode transition from turbine to scramjet propulsion, 2) high Mach turbine engines and 3) TBCC integration. To address these TBCC challenges, the effort is centered on a propulsion mode transition experiment and includes analytical research. The test program, the Combined-Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE LIMX), was conceived to integrate TBCC propulsion with proposed hypersonic vehicles. The goals address: (1) dual inlet operability and performance, (2) mode-transition sequences enabling a switch between turbine and scramjet flow paths, and (3) turbine engine transients during transition. Four test phases are planned from which a database can be used to both validate design and analysis codes and characterize operability and integration issues for TBCC propulsion. In this paper we discuss the research objectives, features of the CCE hardware and test plans, and status of the parametric inlet characterization testing which began in 2011. This effort is sponsored by the NASA Fundamental Aeronautics Hypersonics project

Traveling magnetopause distortion related to a large-scale magnetosheath plasma jet: THEMIS and ground-based observations

NASA Astrophysics Data System (ADS)

Dmitriev, A. V.; Suvorova, A. V.

2012-08-01

Here, we present a case study of THEMIS and ground-based observations of the perturbed dayside magnetopause and the geomagnetic field in relation to the interaction of an interplanetary directional discontinuity (DD) with the magnetosphere on 16 June 2007. The interaction resulted in a large-scale local magnetopause distortion of an "expansion - compression - expansion" (ECE) sequence that lasted for ˜15 min. The compression was caused by a very dense, cold, and fast high-βmagnetosheath plasma flow, a so-called plasma jet, whose kinetic energy was approximately three times higher than the energy of the incident solar wind. The plasma jet resulted in the effective penetration of magnetosheath plasma inside the magnetosphere. A strong distortion of the Chapman-Ferraro current in the ECE sequence generated a tripolar magnetic pulse "decrease - peak- decrease" (DPD) that was observed at low and middle latitudes by some ground-based magnetometers of the INTERMAGNET network. The characteristics of the ECE sequence and the spatial-temporal dynamics of the DPD pulse were found to be very different from any reported patterns of DD interactions with the magnetosphere. The observed features only partially resembled structures such as FTE, hot flow anomalies, and transient density events. Thus, it is difficult to explain them in the context of existing models.

The timetable of evolution

PubMed Central

Knoll, Andrew H.; Nowak, Martin A.

2017-01-01

The integration of fossils, phylogeny, and geochronology has resulted in an increasingly well-resolved timetable of evolution. Life appears to have taken root before the earliest known minimally metamorphosed sedimentary rocks were deposited, but for a billion years or more, evolution played out beneath an essentially anoxic atmosphere. Oxygen concentrations in the atmosphere and surface oceans first rose in the Great Oxygenation Event (GOE) 2.4 billion years ago, and a second increase beginning in the later Neoproterozoic Era [Neoproterozoic Oxygenation Event (NOE)] established the redox profile of modern oceans. The GOE facilitated the emergence of eukaryotes, whereas the NOE is associated with large and complex multicellular organisms. Thus, the GOE and NOE are fundamental pacemakers for evolution. On the time scale of Earth’s entire 4 billion–year history, the evolutionary dynamics of the planet’s biosphere appears to be fast, and the pace of evolution is largely determined by physical changes of the planet. However, in Phanerozoic ecosystems, interactions between new functions enabled by the accumulation of characters in a complex regulatory environment and changing biological components of effective environments appear to have an important influence on the timing of evolutionary innovations. On the much shorter time scale of transient environmental perturbations, such as those associated with mass extinctions, rates of genetic accommodation may have been limiting for life. PMID:28560344

Scramjet test flow reconstruction for a large-scale expansion tube, Part 1: quasi-one-dimensional modelling

NASA Astrophysics Data System (ADS)

Gildfind, D. E.; Jacobs, P. A.; Morgan, R. G.; Chan, W. Y. K.; Gollan, R. J.

2017-11-01

Large-scale free-piston driven expansion tubes have uniquely high total pressure capabilities which make them an important resource for development of access-to-space scramjet engine technology. However, many aspects of their operation are complex, and their test flows are fundamentally unsteady and difficult to measure. While computational fluid dynamics methods provide an important tool for quantifying these flows, these calculations become very expensive with increasing facility size and therefore have to be carefully constructed to ensure sufficient accuracy is achieved within feasible computational times. This study examines modelling strategies for a Mach 10 scramjet test condition developed for The University of Queensland's X3 facility. The present paper outlines the challenges associated with test flow reconstruction, describes the experimental set-up for the X3 experiments, and then details the development of an experimentally tuned quasi-one-dimensional CFD model of the full facility. The 1-D model, which accurately captures longitudinal wave processes, is used to calculate the transient flow history in the shock tube. This becomes the inflow to a higher-fidelity 2-D axisymmetric simulation of the downstream facility, detailed in the Part 2 companion paper, leading to a validated, fully defined nozzle exit test flow.